includes/libs/rdbms/database/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 namespace Wikimedia\Rdbms;
  27
  28 use Psr\Log\LoggerAwareInterface;
  29 use Psr\Log\LoggerInterface;
  30 use Wikimedia\ScopedCallback;
  31 use Wikimedia\Timestamp\ConvertibleTimestamp;
  32 use MediaWiki;
  33 use BagOStuff;
  34 use HashBagOStuff;
  35 use InvalidArgumentException;
  36 use Exception;
  37 use RuntimeException;
  38
  39 /**
  40  * Relational database abstraction object
  41  *
  42  * @ingroup Database
  43  * @since 1.28
  44  */
  45 abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAwareInterface {
  46         /** Number of times to re-try an operation in case of deadlock */
  47         const DEADLOCK_TRIES = 4;
  48         /** Minimum time to wait before retry, in microseconds */
  49         const DEADLOCK_DELAY_MIN = 500000;
  50         /** Maximum time to wait before retry */
  51         const DEADLOCK_DELAY_MAX = 1500000;
  52
  53         /** How long before it is worth doing a dummy query to test the connection */
  54         const PING_TTL = 1.0;
  55         const PING_QUERY = 'SELECT 1 AS ping';
  56
  57         const TINY_WRITE_SEC = 0.010;
  58         const SLOW_WRITE_SEC = 0.500;
  59         const SMALL_WRITE_ROWS = 100;
  60
  61         /** @var string SQL query */
  62         protected $mLastQuery = '';
  63         /** @var float|bool UNIX timestamp of last write query */
  64         protected $mLastWriteTime = false;
  65         /** @var string|bool */
  66         protected $mPHPError = false;
  67         /** @var string */
  68         protected $mServer;
  69         /** @var string */
  70         protected $mUser;
  71         /** @var string */
  72         protected $mPassword;
  73         /** @var string */
  74         protected $mDBname;
  75         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  76         protected $tableAliases = [];
  77         /** @var bool Whether this PHP instance is for a CLI script */
  78         protected $cliMode;
  79         /** @var string Agent name for query profiling */
  80         protected $agent;
  81
  82         /** @var BagOStuff APC cache */
  83         protected $srvCache;
  84         /** @var LoggerInterface */
  85         protected $connLogger;
  86         /** @var LoggerInterface */
  87         protected $queryLogger;
  88         /** @var callback Error logging callback */
  89         protected $errorLogger;
  90
  91         /** @var resource|null Database connection */
  92         protected $mConn = null;
  93         /** @var bool */
  94         protected $mOpened = false;
  95
  96         /** @var array[] List of (callable, method name) */
  97         protected $mTrxIdleCallbacks = [];
  98         /** @var array[] List of (callable, method name) */
  99         protected $mTrxPreCommitCallbacks = [];
 100         /** @var array[] List of (callable, method name) */
 101         protected $mTrxEndCallbacks = [];
 102         /** @var callable[] Map of (name => callable) */
 103         protected $mTrxRecurringCallbacks = [];
 104         /** @var bool Whether to suppress triggering of transaction end callbacks */
 105         protected $mTrxEndCallbacksSuppressed = false;
 106
 107         /** @var string */
 108         protected $mTablePrefix = '';
 109         /** @var string */
 110         protected $mSchema = '';
 111         /** @var int */
 112         protected $mFlags;
 113         /** @var array */
 114         protected $mLBInfo = [];
 115         /** @var bool|null */
 116         protected $mDefaultBigSelects = null;
 117         /** @var array|bool */
 118         protected $mSchemaVars = false;
 119         /** @var array */
 120         protected $mSessionVars = [];
 121         /** @var array|null */
 122         protected $preparedArgs;
 123         /** @var string|bool|null Stashed value of html_errors INI setting */
 124         protected $htmlErrors;
 125         /** @var string */
 126         protected $delimiter = ';';
 127         /** @var DatabaseDomain */
 128         protected $currentDomain;
 129
 130         /**
 131          * Either 1 if a transaction is active or 0 otherwise.
 132          * The other Trx fields may not be meaningfull if this is 0.
 133          *
 134          * @var int
 135          */
 136         protected $mTrxLevel = 0;
 137         /**
 138          * Either a short hexidecimal string if a transaction is active or ""
 139          *
 140          * @var string
 141          * @see Database::mTrxLevel
 142          */
 143         protected $mTrxShortId = '';
 144         /**
 145          * The UNIX time that the transaction started. Callers can assume that if
 146          * snapshot isolation is used, then the data is *at least* up to date to that
 147          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 148          *
 149          * @var float|null
 150          * @see Database::mTrxLevel
 151          */
 152         private $mTrxTimestamp = null;
 153         /** @var float Lag estimate at the time of BEGIN */
 154         private $mTrxReplicaLag = null;
 155         /**
 156          * Remembers the function name given for starting the most recent transaction via begin().
 157          * Used to provide additional context for error reporting.
 158          *
 159          * @var string
 160          * @see Database::mTrxLevel
 161          */
 162         private $mTrxFname = null;
 163         /**
 164          * Record if possible write queries were done in the last transaction started
 165          *
 166          * @var bool
 167          * @see Database::mTrxLevel
 168          */
 169         private $mTrxDoneWrites = false;
 170         /**
 171          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 172          *
 173          * @var bool
 174          * @see Database::mTrxLevel
 175          */
 176         private $mTrxAutomatic = false;
 177         /**
 178          * Array of levels of atomicity within transactions
 179          *
 180          * @var array
 181          */
 182         private $mTrxAtomicLevels = [];
 183         /**
 184          * Record if the current transaction was started implicitly by Database::startAtomic
 185          *
 186          * @var bool
 187          */
 188         private $mTrxAutomaticAtomic = false;
 189         /**
 190          * Track the write query callers of the current transaction
 191          *
 192          * @var string[]
 193          */
 194         private $mTrxWriteCallers = [];
 195         /**
 196          * @var float Seconds spent in write queries for the current transaction
 197          */
 198         private $mTrxWriteDuration = 0.0;
 199         /**
 200          * @var int Number of write queries for the current transaction
 201          */
 202         private $mTrxWriteQueryCount = 0;
 203         /**
 204          * @var int Number of rows affected by write queries for the current transaction
 205          */
 206         private $mTrxWriteAffectedRows = 0;
 207         /**
 208          * @var float Like mTrxWriteQueryCount but excludes lock-bound, easy to replicate, queries
 209          */
 210         private $mTrxWriteAdjDuration = 0.0;
 211         /**
 212          * @var int Number of write queries counted in mTrxWriteAdjDuration
 213          */
 214         private $mTrxWriteAdjQueryCount = 0;
 215         /**
 216          * @var float RTT time estimate
 217          */
 218         private $mRTTEstimate = 0.0;
 219
 220         /** @var array Map of (name => 1) for locks obtained via lock() */
 221         private $mNamedLocksHeld = [];
 222         /** @var array Map of (table name => 1) for TEMPORARY tables */
 223         protected $mSessionTempTables = [];
 224
 225         /** @var IDatabase|null Lazy handle to the master DB this server replicates from */
 226         private $lazyMasterHandle;
 227
 228         /** @var float UNIX timestamp */
 229         protected $lastPing = 0.0;
 230
 231         /** @var int[] Prior mFlags values */
 232         private $priorFlags = [];
 233
 234         /** @var object|string Class name or object With profileIn/profileOut methods */
 235         protected $profiler;
 236         /** @var TransactionProfiler */
 237         protected $trxProfiler;
 238
 239         /**
 240          * Constructor and database handle and attempt to connect to the DB server
 241          *
 242          * IDatabase classes should not be constructed directly in external
 243          * code. Database::factory() should be used instead.
 244          *
 245          * @param array $params Parameters passed from Database::factory()
 246          */
 247         function __construct( array $params ) {
 248                 $server = $params['host'];
 249                 $user = $params['user'];
 250                 $password = $params['password'];
 251                 $dbName = $params['dbname'];
 252
 253                 $this->mSchema = $params['schema'];
 254                 $this->mTablePrefix = $params['tablePrefix'];
 255
 256                 $this->cliMode = $params['cliMode'];
 257                 // Agent name is added to SQL queries in a comment, so make sure it can't break out
 258                 $this->agent = str_replace( '/', '-', $params['agent'] );
 259
 260                 $this->mFlags = $params['flags'];
 261                 if ( $this->mFlags & self::DBO_DEFAULT ) {
 262                         if ( $this->cliMode ) {
 263                                 $this->mFlags &= ~self::DBO_TRX;
 264                         } else {
 265                                 $this->mFlags |= self::DBO_TRX;
 266                         }
 267                 }
 268
 269                 $this->mSessionVars = $params['variables'];
 270
 271                 $this->srvCache = isset( $params['srvCache'] )
 272                         ? $params['srvCache']
 273                         : new HashBagOStuff();
 274
 275                 $this->profiler = $params['profiler'];
 276                 $this->trxProfiler = $params['trxProfiler'];
 277                 $this->connLogger = $params['connLogger'];
 278                 $this->queryLogger = $params['queryLogger'];
 279                 $this->errorLogger = $params['errorLogger'];
 280
 281                 // Set initial dummy domain until open() sets the final DB/prefix
 282                 $this->currentDomain = DatabaseDomain::newUnspecified();
 283
 284                 if ( $user ) {
 285                         $this->open( $server, $user, $password, $dbName );
 286                 } elseif ( $this->requiresDatabaseUser() ) {
 287                         throw new InvalidArgumentException( "No database user provided." );
 288                 }
 289
 290                 // Set the domain object after open() sets the relevant fields
 291                 if ( $this->mDBname != '' ) {
 292                         // Domains with server scope but a table prefix are not used by IDatabase classes
 293                         $this->currentDomain = new DatabaseDomain( $this->mDBname, null, $this->mTablePrefix );
 294                 }
 295         }
 296
 297         /**
 298          * Construct a Database subclass instance given a database type and parameters
 299          *
 300          * This also connects to the database immediately upon object construction
 301          *
 302          * @param string $dbType A possible DB type (sqlite, mysql, postgres)
 303          * @param array $p Parameter map with keys:
 304          *   - host : The hostname of the DB server
 305          *   - user : The name of the database user the client operates under
 306          *   - password : The password for the database user
 307          *   - dbname : The name of the database to use where queries do not specify one.
 308          *      The database must exist or an error might be thrown. Setting this to the empty string
 309          *      will avoid any such errors and make the handle have no implicit database scope. This is
 310          *      useful for queries like SHOW STATUS, CREATE DATABASE, or DROP DATABASE. Note that a
 311          *      "database" in Postgres is rougly equivalent to an entire MySQL server. This the domain
 312          *      in which user names and such are defined, e.g. users are database-specific in Postgres.
 313          *   - schema : The database schema to use (if supported). A "schema" in Postgres is roughly
 314          *      equivalent to a "database" in MySQL. Note that MySQL and SQLite do not use schemas.
 315          *   - tablePrefix : Optional table prefix that is implicitly added on to all table names
 316          *      recognized in queries. This can be used in place of schemas for handle site farms.
 317          *   - flags : Optional bitfield of DBO_* constants that define connection, protocol,
 318          *      buffering, and transaction behavior. It is STRONGLY adviced to leave the DBO_DEFAULT
 319          *      flag in place UNLESS this this database simply acts as a key/value store.
 320          *   - driver: Optional name of a specific DB client driver. For MySQL, there is the old
 321          *      'mysql' driver and the newer 'mysqli' driver.
 322          *   - variables: Optional map of session variables to set after connecting. This can be
 323          *      used to adjust lock timeouts or encoding modes and the like.
 324          *   - connLogger: Optional PSR-3 logger interface instance.
 325          *   - queryLogger: Optional PSR-3 logger interface instance.
 326          *   - profiler: Optional class name or object with profileIn()/profileOut() methods.
 327          *      These will be called in query(), using a simplified version of the SQL that also
 328          *      includes the agent as a SQL comment.
 329          *   - trxProfiler: Optional TransactionProfiler instance.
 330          *   - errorLogger: Optional callback that takes an Exception and logs it.
 331          *   - cliMode: Whether to consider the execution context that of a CLI script.
 332          *   - agent: Optional name used to identify the end-user in query profiling/logging.
 333          *   - srvCache: Optional BagOStuff instance to an APC-style cache.
 334          * @return Database|null If the database driver or extension cannot be found
 335          * @throws InvalidArgumentException If the database driver or extension cannot be found
 336          * @since 1.18
 337          */
 338         final public static function factory( $dbType, $p = [] ) {
 339                 static $canonicalDBTypes = [
 340                         'mysql' => [ 'mysqli', 'mysql' ],
 341                         'postgres' => [],
 342                         'sqlite' => [],
 343                         'oracle' => [],
 344                         'mssql' => [],
 345                 ];
 346                 static $classAliases = [
 347                         'DatabaseMssql' => DatabaseMssql::class,
 348                         'DatabaseMysql' => DatabaseMysql::class,
 349                         'DatabaseMysqli' => DatabaseMysqli::class,
 350                         'DatabaseSqlite' => DatabaseSqlite::class,
 351                         'DatabasePostgres' => DatabasePostgres::class
 352                 ];
 353
 354                 $driver = false;
 355                 $dbType = strtolower( $dbType );
 356                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 357                         $possibleDrivers = $canonicalDBTypes[$dbType];
 358                         if ( !empty( $p['driver'] ) ) {
 359                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 360                                         $driver = $p['driver'];
 361                                 } else {
 362                                         throw new InvalidArgumentException( __METHOD__ .
 363                                                 " type '$dbType' does not support driver '{$p['driver']}'" );
 364                                 }
 365                         } else {
 366                                 foreach ( $possibleDrivers as $posDriver ) {
 367                                         if ( extension_loaded( $posDriver ) ) {
 368                                                 $driver = $posDriver;
 369                                                 break;
 370                                         }
 371                                 }
 372                         }
 373                 } else {
 374                         $driver = $dbType;
 375                 }
 376
 377                 if ( $driver === false || $driver === '' ) {
 378                         throw new InvalidArgumentException( __METHOD__ .
 379                                 " no viable database extension found for type '$dbType'" );
 380                 }
 381
 382                 $class = 'Database' . ucfirst( $driver );
 383                 if ( isset( $classAliases[$class] ) ) {
 384                         $class = $classAliases[$class];
 385                 }
 386
 387                 if ( class_exists( $class ) && is_subclass_of( $class, IDatabase::class ) ) {
 388                         // Resolve some defaults for b/c
 389                         $p['host'] = isset( $p['host'] ) ? $p['host'] : false;
 390                         $p['user'] = isset( $p['user'] ) ? $p['user'] : false;
 391                         $p['password'] = isset( $p['password'] ) ? $p['password'] : false;
 392                         $p['dbname'] = isset( $p['dbname'] ) ? $p['dbname'] : false;
 393                         $p['flags'] = isset( $p['flags'] ) ? $p['flags'] : 0;
 394                         $p['variables'] = isset( $p['variables'] ) ? $p['variables'] : [];
 395                         $p['tablePrefix'] = isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : '';
 396                         $p['schema'] = isset( $p['schema'] ) ? $p['schema'] : '';
 397                         $p['cliMode'] = isset( $p['cliMode'] ) ? $p['cliMode'] : ( PHP_SAPI === 'cli' );
 398                         $p['agent'] = isset( $p['agent'] ) ? $p['agent'] : '';
 399                         if ( !isset( $p['connLogger'] ) ) {
 400                                 $p['connLogger'] = new \Psr\Log\NullLogger();
 401                         }
 402                         if ( !isset( $p['queryLogger'] ) ) {
 403                                 $p['queryLogger'] = new \Psr\Log\NullLogger();
 404                         }
 405                         $p['profiler'] = isset( $p['profiler'] ) ? $p['profiler'] : null;
 406                         if ( !isset( $p['trxProfiler'] ) ) {
 407                                 $p['trxProfiler'] = new TransactionProfiler();
 408                         }
 409                         if ( !isset( $p['errorLogger'] ) ) {
 410                                 $p['errorLogger'] = function ( Exception $e ) {
 411                                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 412                                 };
 413                         }
 414
 415                         $conn = new $class( $p );
 416                 } else {
 417                         $conn = null;
 418                 }
 419
 420                 return $conn;
 421         }
 422
 423         /**
 424          * Set the PSR-3 logger interface to use for query logging. (The logger
 425          * interfaces for connection logging and error logging can be set with the
 426          * constructor.)
 427          *
 428          * @param LoggerInterface $logger
 429          */
 430         public function setLogger( LoggerInterface $logger ) {
 431                 $this->queryLogger = $logger;
 432         }
 433
 434         public function getServerInfo() {
 435                 return $this->getServerVersion();
 436         }
 437
 438         public function bufferResults( $buffer = null ) {
 439                 $res = !$this->getFlag( self::DBO_NOBUFFER );
 440                 if ( $buffer !== null ) {
 441                         $buffer
 442                                 ? $this->clearFlag( self::DBO_NOBUFFER )
 443                                 : $this->setFlag( self::DBO_NOBUFFER );
 444                 }
 445
 446                 return $res;
 447         }
 448
 449         /**
 450          * Turns on (false) or off (true) the automatic generation and sending
 451          * of a "we're sorry, but there has been a database error" page on
 452          * database errors. Default is on (false). When turned off, the
 453          * code should use lastErrno() and lastError() to handle the
 454          * situation as appropriate.
 455          *
 456          * Do not use this function outside of the Database classes.
 457          *
 458          * @param null|bool $ignoreErrors
 459          * @return bool The previous value of the flag.
 460          */
 461         protected function ignoreErrors( $ignoreErrors = null ) {
 462                 $res = $this->getFlag( self::DBO_IGNORE );
 463                 if ( $ignoreErrors !== null ) {
 464                         $ignoreErrors
 465                                 ? $this->setFlag( self::DBO_IGNORE )
 466                                 : $this->clearFlag( self::DBO_IGNORE );
 467                 }
 468
 469                 return $res;
 470         }
 471
 472         public function trxLevel() {
 473                 return $this->mTrxLevel;
 474         }
 475
 476         public function trxTimestamp() {
 477                 return $this->mTrxLevel ? $this->mTrxTimestamp : null;
 478         }
 479
 480         public function tablePrefix( $prefix = null ) {
 481                 $old = $this->mTablePrefix;
 482                 if ( $prefix !== null ) {
 483                         $this->mTablePrefix = $prefix;
 484                         $this->currentDomain = ( $this->mDBname != '' )
 485                                 ? new DatabaseDomain( $this->mDBname, null, $this->mTablePrefix )
 486                                 : DatabaseDomain::newUnspecified();
 487                 }
 488
 489                 return $old;
 490         }
 491
 492         public function dbSchema( $schema = null ) {
 493                 $old = $this->mSchema;
 494                 if ( $schema !== null ) {
 495                         $this->mSchema = $schema;
 496                 }
 497
 498                 return $old;
 499         }
 500
 501         public function getLBInfo( $name = null ) {
 502                 if ( is_null( $name ) ) {
 503                         return $this->mLBInfo;
 504                 } else {
 505                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 506                                 return $this->mLBInfo[$name];
 507                         } else {
 508                                 return null;
 509                         }
 510                 }
 511         }
 512
 513         public function setLBInfo( $name, $value = null ) {
 514                 if ( is_null( $value ) ) {
 515                         $this->mLBInfo = $name;
 516                 } else {
 517                         $this->mLBInfo[$name] = $value;
 518                 }
 519         }
 520
 521         public function setLazyMasterHandle( IDatabase $conn ) {
 522                 $this->lazyMasterHandle = $conn;
 523         }
 524
 525         /**
 526          * @return IDatabase|null
 527          * @see setLazyMasterHandle()
 528          * @since 1.27
 529          */
 530         protected function getLazyMasterHandle() {
 531                 return $this->lazyMasterHandle;
 532         }
 533
 534         public function implicitGroupby() {
 535                 return true;
 536         }
 537
 538         public function implicitOrderby() {
 539                 return true;
 540         }
 541
 542         public function lastQuery() {
 543                 return $this->mLastQuery;
 544         }
 545
 546         public function doneWrites() {
 547                 return (bool)$this->mLastWriteTime;
 548         }
 549
 550         public function lastDoneWrites() {
 551                 return $this->mLastWriteTime ?: false;
 552         }
 553
 554         public function writesPending() {
 555                 return $this->mTrxLevel && $this->mTrxDoneWrites;
 556         }
 557
 558         public function writesOrCallbacksPending() {
 559                 return $this->mTrxLevel && (
 560                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 561                 );
 562         }
 563
 564         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 565                 if ( !$this->mTrxLevel ) {
 566                         return false;
 567                 } elseif ( !$this->mTrxDoneWrites ) {
 568                         return 0.0;
 569                 }
 570
 571                 switch ( $type ) {
 572                         case self::ESTIMATE_DB_APPLY:
 573                                 $this->ping( $rtt );
 574                                 $rttAdjTotal = $this->mTrxWriteAdjQueryCount * $rtt;
 575                                 $applyTime = max( $this->mTrxWriteAdjDuration - $rttAdjTotal, 0 );
 576                                 // For omitted queries, make them count as something at least
 577                                 $omitted = $this->mTrxWriteQueryCount - $this->mTrxWriteAdjQueryCount;
 578                                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 579
 580                                 return $applyTime;
 581                         default: // everything
 582                                 return $this->mTrxWriteDuration;
 583                 }
 584         }
 585
 586         public function pendingWriteCallers() {
 587                 return $this->mTrxLevel ? $this->mTrxWriteCallers : [];
 588         }
 589
 590         public function pendingWriteRowsAffected() {
 591                 return $this->mTrxWriteAffectedRows;
 592         }
 593
 594         /**
 595          * Get the list of method names that have pending write queries or callbacks
 596          * for this transaction
 597          *
 598          * @return array
 599          */
 600         protected function pendingWriteAndCallbackCallers() {
 601                 if ( !$this->mTrxLevel ) {
 602                         return [];
 603                 }
 604
 605                 $fnames = $this->mTrxWriteCallers;
 606                 foreach ( [
 607                         $this->mTrxIdleCallbacks,
 608                         $this->mTrxPreCommitCallbacks,
 609                         $this->mTrxEndCallbacks
 610                 ] as $callbacks ) {
 611                         foreach ( $callbacks as $callback ) {
 612                                 $fnames[] = $callback[1];
 613                         }
 614                 }
 615
 616                 return $fnames;
 617         }
 618
 619         public function isOpen() {
 620                 return $this->mOpened;
 621         }
 622
 623         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 624                 if ( $remember === self::REMEMBER_PRIOR ) {
 625                         array_push( $this->priorFlags, $this->mFlags );
 626                 }
 627                 $this->mFlags |= $flag;
 628         }
 629
 630         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 631                 if ( $remember === self::REMEMBER_PRIOR ) {
 632                         array_push( $this->priorFlags, $this->mFlags );
 633                 }
 634                 $this->mFlags &= ~$flag;
 635         }
 636
 637         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 638                 if ( !$this->priorFlags ) {
 639                         return;
 640                 }
 641
 642                 if ( $state === self::RESTORE_INITIAL ) {
 643                         $this->mFlags = reset( $this->priorFlags );
 644                         $this->priorFlags = [];
 645                 } else {
 646                         $this->mFlags = array_pop( $this->priorFlags );
 647                 }
 648         }
 649
 650         public function getFlag( $flag ) {
 651                 return !!( $this->mFlags & $flag );
 652         }
 653
 654         /**
 655          * @param string $name Class field name
 656          * @return mixed
 657          * @deprecated Since 1.28
 658          */
 659         public function getProperty( $name ) {
 660                 return $this->$name;
 661         }
 662
 663         public function getDomainID() {
 664                 return $this->currentDomain->getId();
 665         }
 666
 667         final public function getWikiID() {
 668                 return $this->getDomainID();
 669         }
 670
 671         /**
 672          * Get information about an index into an object
 673          * @param string $table Table name
 674          * @param string $index Index name
 675          * @param string $fname Calling function name
 676          * @return mixed Database-specific index description class or false if the index does not exist
 677          */
 678         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 679
 680         /**
 681          * Wrapper for addslashes()
 682          *
 683          * @param string $s String to be slashed.
 684          * @return string Slashed string.
 685          */
 686         abstract function strencode( $s );
 687
 688         /**
 689          * Set a custom error handler for logging errors during database connection
 690          */
 691         protected function installErrorHandler() {
 692                 $this->mPHPError = false;
 693                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 694                 set_error_handler( [ $this, 'connectionErrorLogger' ] );
 695         }
 696
 697         /**
 698          * Restore the previous error handler and return the last PHP error for this DB
 699          *
 700          * @return bool|string
 701          */
 702         protected function restoreErrorHandler() {
 703                 restore_error_handler();
 704                 if ( $this->htmlErrors !== false ) {
 705                         ini_set( 'html_errors', $this->htmlErrors );
 706                 }
 707
 708                 return $this->getLastPHPError();
 709         }
 710
 711         /**
 712          * @return string|bool Last PHP error for this DB (typically connection errors)
 713          */
 714         protected function getLastPHPError() {
 715                 if ( $this->mPHPError ) {
 716                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 717                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 718
 719                         return $error;
 720                 }
 721
 722                 return false;
 723         }
 724
 725         /**
 726          * Error handler for logging errors during database connection
 727          * This method should not be used outside of Database classes
 728          *
 729          * @param int $errno
 730          * @param string $errstr
 731          */
 732         public function connectionErrorLogger( $errno, $errstr ) {
 733                 $this->mPHPError = $errstr;
 734         }
 735
 736         /**
 737          * Create a log context to pass to PSR-3 logger functions.
 738          *
 739          * @param array $extras Additional data to add to context
 740          * @return array
 741          */
 742         protected function getLogContext( array $extras = [] ) {
 743                 return array_merge(
 744                         [
 745                                 'db_server' => $this->mServer,
 746                                 'db_name' => $this->mDBname,
 747                                 'db_user' => $this->mUser,
 748                         ],
 749                         $extras
 750                 );
 751         }
 752
 753         public function close() {
 754                 if ( $this->mConn ) {
 755                         if ( $this->trxLevel() ) {
 756                                 $this->commit( __METHOD__, self::FLUSHING_INTERNAL );
 757                         }
 758
 759                         $closed = $this->closeConnection();
 760                         $this->mConn = false;
 761                 } elseif (
 762                         $this->mTrxIdleCallbacks ||
 763                         $this->mTrxPreCommitCallbacks ||
 764                         $this->mTrxEndCallbacks
 765                 ) { // sanity
 766                         throw new RuntimeException( "Transaction callbacks still pending." );
 767                 } else {
 768                         $closed = true;
 769                 }
 770                 $this->mOpened = false;
 771
 772                 return $closed;
 773         }
 774
 775         /**
 776          * Make sure isOpen() returns true as a sanity check
 777          *
 778          * @throws DBUnexpectedError
 779          */
 780         protected function assertOpen() {
 781                 if ( !$this->isOpen() ) {
 782                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
 783                 }
 784         }
 785
 786         /**
 787          * Closes underlying database connection
 788          * @since 1.20
 789          * @return bool Whether connection was closed successfully
 790          */
 791         abstract protected function closeConnection();
 792
 793         public function reportConnectionError( $error = 'Unknown error' ) {
 794                 $myError = $this->lastError();
 795                 if ( $myError ) {
 796                         $error = $myError;
 797                 }
 798
 799                 # New method
 800                 throw new DBConnectionError( $this, $error );
 801         }
 802
 803         /**
 804          * The DBMS-dependent part of query()
 805          *
 806          * @param string $sql SQL query.
 807          * @return ResultWrapper|bool Result object to feed to fetchObject,
 808          *   fetchRow, ...; or false on failure
 809          */
 810         abstract protected function doQuery( $sql );
 811
 812         /**
 813          * Determine whether a query writes to the DB.
 814          * Should return true if unsure.
 815          *
 816          * @param string $sql
 817          * @return bool
 818          */
 819         protected function isWriteQuery( $sql ) {
 820                 return !preg_match(
 821                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 822         }
 823
 824         /**
 825          * @param string $sql
 826          * @return string|null
 827          */
 828         protected function getQueryVerb( $sql ) {
 829                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
 830         }
 831
 832         /**
 833          * Determine whether a SQL statement is sensitive to isolation level.
 834          * A SQL statement is considered transactable if its result could vary
 835          * depending on the transaction isolation level. Operational commands
 836          * such as 'SET' and 'SHOW' are not considered to be transactable.
 837          *
 838          * @param string $sql
 839          * @return bool
 840          */
 841         protected function isTransactableQuery( $sql ) {
 842                 return !in_array(
 843                         $this->getQueryVerb( $sql ),
 844                         [ 'BEGIN', 'COMMIT', 'ROLLBACK', 'SHOW', 'SET', 'CREATE', 'ALTER' ],
 845                         true
 846                 );
 847         }
 848
 849         /**
 850          * @param string $sql A SQL query
 851          * @return bool Whether $sql is SQL for TEMPORARY table operation
 852          */
 853         protected function registerTempTableOperation( $sql ) {
 854                 if ( preg_match(
 855                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 856                         $sql,
 857                         $matches
 858                 ) ) {
 859                         $this->mSessionTempTables[$matches[1]] = 1;
 860
 861                         return true;
 862                 } elseif ( preg_match(
 863                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 864                         $sql,
 865                         $matches
 866                 ) ) {
 867                         $isTemp = isset( $this->mSessionTempTables[$matches[1]] );
 868                         unset( $this->mSessionTempTables[$matches[1]] );
 869
 870                         return $isTemp;
 871                 } elseif ( preg_match(
 872                         '/^TRUNCATE\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 873                         $sql,
 874                         $matches
 875                 ) ) {
 876                         return isset( $this->mSessionTempTables[$matches[1]] );
 877                 } elseif ( preg_match(
 878                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
 879                         $sql,
 880                         $matches
 881                 ) ) {
 882                         return isset( $this->mSessionTempTables[$matches[1]] );
 883                 }
 884
 885                 return false;
 886         }
 887
 888         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 889                 $priorWritesPending = $this->writesOrCallbacksPending();
 890                 $this->mLastQuery = $sql;
 891
 892                 $isWrite = $this->isWriteQuery( $sql );
 893                 if ( $isWrite ) {
 894                         $isNonTempWrite = !$this->registerTempTableOperation( $sql );
 895                 } else {
 896                         $isNonTempWrite = false;
 897                 }
 898
 899                 if ( $isWrite ) {
 900                         # In theory, non-persistent writes are allowed in read-only mode, but due to things
 901                         # like https://bugs.mysql.com/bug.php?id=33669 that might not work anyway...
 902                         $reason = $this->getReadOnlyReason();
 903                         if ( $reason !== false ) {
 904                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
 905                         }
 906                         # Set a flag indicating that writes have been done
 907                         $this->mLastWriteTime = microtime( true );
 908                 }
 909
 910                 # Add trace comment to the begin of the sql string, right after the operator.
 911                 # Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598)
 912                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
 913
 914                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
 915                 if ( !$this->mTrxLevel && $this->getFlag( self::DBO_TRX )
 916                         && $this->isTransactableQuery( $sql )
 917                 ) {
 918                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
 919                         $this->mTrxAutomatic = true;
 920                 }
 921
 922                 # Keep track of whether the transaction has write queries pending
 923                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $isWrite ) {
 924                         $this->mTrxDoneWrites = true;
 925                         $this->trxProfiler->transactionWritingIn(
 926                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
 927                 }
 928
 929                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
 930                         $this->queryLogger->debug( "{$this->mDBname} {$commentedSql}" );
 931                 }
 932
 933                 # Avoid fatals if close() was called
 934                 $this->assertOpen();
 935
 936                 # Send the query to the server
 937                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
 938
 939                 # Try reconnecting if the connection was lost
 940                 if ( false === $ret && $this->wasErrorReissuable() ) {
 941                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
 942                         # Stash the last error values before anything might clear them
 943                         $lastError = $this->lastError();
 944                         $lastErrno = $this->lastErrno();
 945                         # Update state tracking to reflect transaction loss due to disconnection
 946                         $this->handleSessionLoss();
 947                         if ( $this->reconnect() ) {
 948                                 $msg = __METHOD__ . ': lost connection to {dbserver}; reconnected';
 949                                 $params = [ 'dbserver' => $this->getServer() ];
 950                                 $this->connLogger->warning( $msg, $params );
 951                                 $this->queryLogger->warning( $msg, $params +
 952                                         [ 'trace' => ( new RuntimeException() )->getTraceAsString() ] );
 953
 954                                 if ( !$recoverable ) {
 955                                         # Callers may catch the exception and continue to use the DB
 956                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname );
 957                                 } else {
 958                                         # Should be safe to silently retry the query
 959                                         $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
 960                                 }
 961                         } else {
 962                                 $msg = __METHOD__ . ': lost connection to {dbserver} permanently';
 963                                 $this->connLogger->error( $msg, [ 'dbserver' => $this->getServer() ] );
 964                         }
 965                 }
 966
 967                 if ( false === $ret ) {
 968                         # Deadlocks cause the entire transaction to abort, not just the statement.
 969                         # https://dev.mysql.com/doc/refman/5.7/en/innodb-error-handling.html
 970                         # https://www.postgresql.org/docs/9.1/static/explicit-locking.html
 971                         if ( $this->wasDeadlock() ) {
 972                                 if ( $this->explicitTrxActive() || $priorWritesPending ) {
 973                                         $tempIgnore = false; // not recoverable
 974                                 }
 975                                 # Update state tracking to reflect transaction loss
 976                                 $this->handleSessionLoss();
 977                         }
 978
 979                         $this->reportQueryError(
 980                                 $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 981                 }
 982
 983                 $res = $this->resultObject( $ret );
 984
 985                 return $res;
 986         }
 987
 988         /**
 989          * Helper method for query() that handles profiling and logging and sends
 990          * the query to doQuery()
 991          *
 992          * @param string $sql Original SQL query
 993          * @param string $commentedSql SQL query with debugging/trace comment
 994          * @param bool $isWrite Whether the query is a (non-temporary) write operation
 995          * @param string $fname Name of the calling function
 996          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
 997          *     object for a successful read query, or false on failure
 998          */
 999         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
1000                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1001                 # generalizeSQL() will probably cut down the query to reasonable
1002                 # logging size most of the time. The substr is really just a sanity check.
1003                 if ( $isMaster ) {
1004                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1005                 } else {
1006                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1007                 }
1008
1009                 # Include query transaction state
1010                 $queryProf .= $this->mTrxShortId ? " [TRX#{$this->mTrxShortId}]" : "";
1011
1012                 $startTime = microtime( true );
1013                 if ( $this->profiler ) {
1014                         call_user_func( [ $this->profiler, 'profileIn' ], $queryProf );
1015                 }
1016                 $ret = $this->doQuery( $commentedSql );
1017                 if ( $this->profiler ) {
1018                         call_user_func( [ $this->profiler, 'profileOut' ], $queryProf );
1019                 }
1020                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1021
1022                 unset( $queryProfSection ); // profile out (if set)
1023
1024                 if ( $ret !== false ) {
1025                         $this->lastPing = $startTime;
1026                         if ( $isWrite && $this->mTrxLevel ) {
1027                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1028                                 $this->mTrxWriteCallers[] = $fname;
1029                         }
1030                 }
1031
1032                 if ( $sql === self::PING_QUERY ) {
1033                         $this->mRTTEstimate = $queryRuntime;
1034                 }
1035
1036                 $this->trxProfiler->recordQueryCompletion(
1037                         $queryProf, $startTime, $isWrite, $this->affectedRows()
1038                 );
1039                 $this->queryLogger->debug( $sql, [
1040                         'method' => $fname,
1041                         'master' => $isMaster,
1042                         'runtime' => $queryRuntime,
1043                 ] );
1044
1045                 return $ret;
1046         }
1047
1048         /**
1049          * Update the estimated run-time of a query, not counting large row lock times
1050          *
1051          * LoadBalancer can be set to rollback transactions that will create huge replication
1052          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1053          * queries, like inserting a row can take a long time due to row locking. This method
1054          * uses some simple heuristics to discount those cases.
1055          *
1056          * @param string $sql A SQL write query
1057          * @param float $runtime Total runtime, including RTT
1058          * @param int $affected Affected row count
1059          */
1060         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1061                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1062                 $indicativeOfReplicaRuntime = true;
1063                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1064                         $verb = $this->getQueryVerb( $sql );
1065                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1066                         if ( $verb === 'INSERT' ) {
1067                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1068                         } elseif ( $verb === 'REPLACE' ) {
1069                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1070                         }
1071                 }
1072
1073                 $this->mTrxWriteDuration += $runtime;
1074                 $this->mTrxWriteQueryCount += 1;
1075                 $this->mTrxWriteAffectedRows += $affected;
1076                 if ( $indicativeOfReplicaRuntime ) {
1077                         $this->mTrxWriteAdjDuration += $runtime;
1078                         $this->mTrxWriteAdjQueryCount += 1;
1079                 }
1080         }
1081
1082         /**
1083          * Determine whether or not it is safe to retry queries after a database
1084          * connection is lost
1085          *
1086          * @param string $sql SQL query
1087          * @param bool $priorWritesPending Whether there is a transaction open with
1088          *     possible write queries or transaction pre-commit/idle callbacks
1089          *     waiting on it to finish.
1090          * @return bool True if it is safe to retry the query, false otherwise
1091          */
1092         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1093                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1094                 # Dropped connections also mean that named locks are automatically released.
1095                 # Only allow error suppression in autocommit mode or when the lost transaction
1096                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1097                 if ( $this->mNamedLocksHeld ) {
1098                         return false; // possible critical section violation
1099                 } elseif ( $sql === 'COMMIT' ) {
1100                         return !$priorWritesPending; // nothing written anyway? (T127428)
1101                 } elseif ( $sql === 'ROLLBACK' ) {
1102                         return true; // transaction lost...which is also what was requested :)
1103                 } elseif ( $this->explicitTrxActive() ) {
1104                         return false; // don't drop atomocity
1105                 } elseif ( $priorWritesPending ) {
1106                         return false; // prior writes lost from implicit transaction
1107                 }
1108
1109                 return true;
1110         }
1111
1112         /**
1113          * Clean things up after transaction loss due to disconnection
1114          *
1115          * @return null|Exception
1116          */
1117         private function handleSessionLoss() {
1118                 $this->mTrxLevel = 0;
1119                 $this->mTrxIdleCallbacks = []; // T67263
1120                 $this->mTrxPreCommitCallbacks = []; // T67263
1121                 $this->mSessionTempTables = [];
1122                 $this->mNamedLocksHeld = [];
1123                 try {
1124                         // Handle callbacks in mTrxEndCallbacks
1125                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1126                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1127                         return null;
1128                 } catch ( Exception $e ) {
1129                         // Already logged; move on...
1130                         return $e;
1131                 }
1132         }
1133
1134         /**
1135          * Checks whether the cause of the error is detected to be a timeout.
1136          *
1137          * It returns false by default, and not all engines support detecting this yet.
1138          * If this returns false, it will be treated as a generic query error.
1139          *
1140          * @param string $error Error text
1141          * @param int $errno Error number
1142          * @return bool
1143          */
1144         protected function wasQueryTimeout( $error, $errno ) {
1145                 return false;
1146         }
1147
1148         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1149                 if ( $this->ignoreErrors() || $tempIgnore ) {
1150                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1151                 } else {
1152                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1153                         $this->queryLogger->error(
1154                                 "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1155                                 $this->getLogContext( [
1156                                         'method' => __METHOD__,
1157                                         'errno' => $errno,
1158                                         'error' => $error,
1159                                         'sql1line' => $sql1line,
1160                                         'fname' => $fname,
1161                                 ] )
1162                         );
1163                         $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1164                         $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1165                         if ( $wasQueryTimeout ) {
1166                                 throw new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1167                         } else {
1168                                 throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1169                         }
1170                 }
1171         }
1172
1173         public function freeResult( $res ) {
1174         }
1175
1176         public function selectField(
1177                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1178         ) {
1179                 if ( $var === '*' ) { // sanity
1180                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1181                 }
1182
1183                 if ( !is_array( $options ) ) {
1184                         $options = [ $options ];
1185                 }
1186
1187                 $options['LIMIT'] = 1;
1188
1189                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1190                 if ( $res === false || !$this->numRows( $res ) ) {
1191                         return false;
1192                 }
1193
1194                 $row = $this->fetchRow( $res );
1195
1196                 if ( $row !== false ) {
1197                         return reset( $row );
1198                 } else {
1199                         return false;
1200                 }
1201         }
1202
1203         public function selectFieldValues(
1204                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1205         ) {
1206                 if ( $var === '*' ) { // sanity
1207                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1208                 } elseif ( !is_string( $var ) ) { // sanity
1209                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1210                 }
1211
1212                 if ( !is_array( $options ) ) {
1213                         $options = [ $options ];
1214                 }
1215
1216                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1217                 if ( $res === false ) {
1218                         return false;
1219                 }
1220
1221                 $values = [];
1222                 foreach ( $res as $row ) {
1223                         $values[] = $row->$var;
1224                 }
1225
1226                 return $values;
1227         }
1228
1229         /**
1230          * Returns an optional USE INDEX clause to go after the table, and a
1231          * string to go at the end of the query.
1232          *
1233          * @param array $options Associative array of options to be turned into
1234          *   an SQL query, valid keys are listed in the function.
1235          * @return array
1236          * @see Database::select()
1237          */
1238         protected function makeSelectOptions( $options ) {
1239                 $preLimitTail = $postLimitTail = '';
1240                 $startOpts = '';
1241
1242                 $noKeyOptions = [];
1243
1244                 foreach ( $options as $key => $option ) {
1245                         if ( is_numeric( $key ) ) {
1246                                 $noKeyOptions[$option] = true;
1247                         }
1248                 }
1249
1250                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1251
1252                 $preLimitTail .= $this->makeOrderBy( $options );
1253
1254                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1255                         $postLimitTail .= ' FOR UPDATE';
1256                 }
1257
1258                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1259                         $postLimitTail .= ' LOCK IN SHARE MODE';
1260                 }
1261
1262                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1263                         $startOpts .= 'DISTINCT';
1264                 }
1265
1266                 # Various MySQL extensions
1267                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1268                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1269                 }
1270
1271                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1272                         $startOpts .= ' HIGH_PRIORITY';
1273                 }
1274
1275                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1276                         $startOpts .= ' SQL_BIG_RESULT';
1277                 }
1278
1279                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1280                         $startOpts .= ' SQL_BUFFER_RESULT';
1281                 }
1282
1283                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1284                         $startOpts .= ' SQL_SMALL_RESULT';
1285                 }
1286
1287                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1288                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1289                 }
1290
1291                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1292                         $startOpts .= ' SQL_CACHE';
1293                 }
1294
1295                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1296                         $startOpts .= ' SQL_NO_CACHE';
1297                 }
1298
1299                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1300                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1301                 } else {
1302                         $useIndex = '';
1303                 }
1304                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1305                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1306                 } else {
1307                         $ignoreIndex = '';
1308                 }
1309
1310                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1311         }
1312
1313         /**
1314          * Returns an optional GROUP BY with an optional HAVING
1315          *
1316          * @param array $options Associative array of options
1317          * @return string
1318          * @see Database::select()
1319          * @since 1.21
1320          */
1321         protected function makeGroupByWithHaving( $options ) {
1322                 $sql = '';
1323                 if ( isset( $options['GROUP BY'] ) ) {
1324                         $gb = is_array( $options['GROUP BY'] )
1325                                 ? implode( ',', $options['GROUP BY'] )
1326                                 : $options['GROUP BY'];
1327                         $sql .= ' GROUP BY ' . $gb;
1328                 }
1329                 if ( isset( $options['HAVING'] ) ) {
1330                         $having = is_array( $options['HAVING'] )
1331                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1332                                 : $options['HAVING'];
1333                         $sql .= ' HAVING ' . $having;
1334                 }
1335
1336                 return $sql;
1337         }
1338
1339         /**
1340          * Returns an optional ORDER BY
1341          *
1342          * @param array $options Associative array of options
1343          * @return string
1344          * @see Database::select()
1345          * @since 1.21
1346          */
1347         protected function makeOrderBy( $options ) {
1348                 if ( isset( $options['ORDER BY'] ) ) {
1349                         $ob = is_array( $options['ORDER BY'] )
1350                                 ? implode( ',', $options['ORDER BY'] )
1351                                 : $options['ORDER BY'];
1352
1353                         return ' ORDER BY ' . $ob;
1354                 }
1355
1356                 return '';
1357         }
1358
1359         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1360                 $options = [], $join_conds = [] ) {
1361                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1362
1363                 return $this->query( $sql, $fname );
1364         }
1365
1366         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1367                 $options = [], $join_conds = []
1368         ) {
1369                 if ( is_array( $vars ) ) {
1370                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1371                 }
1372
1373                 $options = (array)$options;
1374                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1375                         ? $options['USE INDEX']
1376                         : [];
1377                 $ignoreIndexes = (
1378                         isset( $options['IGNORE INDEX'] ) &&
1379                         is_array( $options['IGNORE INDEX'] )
1380                 )
1381                         ? $options['IGNORE INDEX']
1382                         : [];
1383
1384                 if ( is_array( $table ) ) {
1385                         $from = ' FROM ' .
1386                                 $this->tableNamesWithIndexClauseOrJOIN(
1387                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1388                 } elseif ( $table != '' ) {
1389                         if ( $table[0] == ' ' ) {
1390                                 $from = ' FROM ' . $table;
1391                         } else {
1392                                 $from = ' FROM ' .
1393                                         $this->tableNamesWithIndexClauseOrJOIN(
1394                                                 [ $table ], $useIndexes, $ignoreIndexes, [] );
1395                         }
1396                 } else {
1397                         $from = '';
1398                 }
1399
1400                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1401                         $this->makeSelectOptions( $options );
1402
1403                 if ( !empty( $conds ) ) {
1404                         if ( is_array( $conds ) ) {
1405                                 $conds = $this->makeList( $conds, self::LIST_AND );
1406                         }
1407                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex " .
1408                                 "WHERE $conds $preLimitTail";
1409                 } else {
1410                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex $preLimitTail";
1411                 }
1412
1413                 if ( isset( $options['LIMIT'] ) ) {
1414                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1415                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1416                 }
1417                 $sql = "$sql $postLimitTail";
1418
1419                 if ( isset( $options['EXPLAIN'] ) ) {
1420                         $sql = 'EXPLAIN ' . $sql;
1421                 }
1422
1423                 return $sql;
1424         }
1425
1426         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1427                 $options = [], $join_conds = []
1428         ) {
1429                 $options = (array)$options;
1430                 $options['LIMIT'] = 1;
1431                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1432
1433                 if ( $res === false ) {
1434                         return false;
1435                 }
1436
1437                 if ( !$this->numRows( $res ) ) {
1438                         return false;
1439                 }
1440
1441                 $obj = $this->fetchObject( $res );
1442
1443                 return $obj;
1444         }
1445
1446         public function estimateRowCount(
1447                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
1448         ) {
1449                 $rows = 0;
1450                 $res = $this->select( $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options );
1451
1452                 if ( $res ) {
1453                         $row = $this->fetchRow( $res );
1454                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1455                 }
1456
1457                 return $rows;
1458         }
1459
1460         public function selectRowCount(
1461                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1462         ) {
1463                 $rows = 0;
1464                 $sql = $this->selectSQLText( $tables, '1', $conds, $fname, $options, $join_conds );
1465                 // The identifier quotes is primarily for MSSQL.
1466                 $rowCountCol = $this->addIdentifierQuotes( "rowcount" );
1467                 $tableName = $this->addIdentifierQuotes( "tmp_count" );
1468                 $res = $this->query( "SELECT COUNT(*) AS $rowCountCol FROM ($sql) $tableName", $fname );
1469
1470                 if ( $res ) {
1471                         $row = $this->fetchRow( $res );
1472                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1473                 }
1474
1475                 return $rows;
1476         }
1477
1478         /**
1479          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1480          * It's only slightly flawed. Don't use for anything important.
1481          *
1482          * @param string $sql A SQL Query
1483          *
1484          * @return string
1485          */
1486         protected static function generalizeSQL( $sql ) {
1487                 # This does the same as the regexp below would do, but in such a way
1488                 # as to avoid crashing php on some large strings.
1489                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1490
1491                 $sql = str_replace( "\\\\", '', $sql );
1492                 $sql = str_replace( "\\'", '', $sql );
1493                 $sql = str_replace( "\\\"", '', $sql );
1494                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1495                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1496
1497                 # All newlines, tabs, etc replaced by single space
1498                 $sql = preg_replace( '/\s+/', ' ', $sql );
1499
1500                 # All numbers => N,
1501                 # except the ones surrounded by characters, e.g. l10n
1502                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1503                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1504
1505                 return $sql;
1506         }
1507
1508         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1509                 $info = $this->fieldInfo( $table, $field );
1510
1511                 return (bool)$info;
1512         }
1513
1514         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1515                 if ( !$this->tableExists( $table ) ) {
1516                         return null;
1517                 }
1518
1519                 $info = $this->indexInfo( $table, $index, $fname );
1520                 if ( is_null( $info ) ) {
1521                         return null;
1522                 } else {
1523                         return $info !== false;
1524                 }
1525         }
1526
1527         public function tableExists( $table, $fname = __METHOD__ ) {
1528                 $tableRaw = $this->tableName( $table, 'raw' );
1529                 if ( isset( $this->mSessionTempTables[$tableRaw] ) ) {
1530                         return true; // already known to exist
1531                 }
1532
1533                 $table = $this->tableName( $table );
1534                 $ignoreErrors = true;
1535                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname, $ignoreErrors );
1536
1537                 return (bool)$res;
1538         }
1539
1540         public function indexUnique( $table, $index ) {
1541                 $indexInfo = $this->indexInfo( $table, $index );
1542
1543                 if ( !$indexInfo ) {
1544                         return null;
1545                 }
1546
1547                 return !$indexInfo[0]->Non_unique;
1548         }
1549
1550         /**
1551          * Helper for Database::insert().
1552          *
1553          * @param array $options
1554          * @return string
1555          */
1556         protected function makeInsertOptions( $options ) {
1557                 return implode( ' ', $options );
1558         }
1559
1560         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1561                 # No rows to insert, easy just return now
1562                 if ( !count( $a ) ) {
1563                         return true;
1564                 }
1565
1566                 $table = $this->tableName( $table );
1567
1568                 if ( !is_array( $options ) ) {
1569                         $options = [ $options ];
1570                 }
1571
1572                 $fh = null;
1573                 if ( isset( $options['fileHandle'] ) ) {
1574                         $fh = $options['fileHandle'];
1575                 }
1576                 $options = $this->makeInsertOptions( $options );
1577
1578                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1579                         $multi = true;
1580                         $keys = array_keys( $a[0] );
1581                 } else {
1582                         $multi = false;
1583                         $keys = array_keys( $a );
1584                 }
1585
1586                 $sql = 'INSERT ' . $options .
1587                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1588
1589                 if ( $multi ) {
1590                         $first = true;
1591                         foreach ( $a as $row ) {
1592                                 if ( $first ) {
1593                                         $first = false;
1594                                 } else {
1595                                         $sql .= ',';
1596                                 }
1597                                 $sql .= '(' . $this->makeList( $row ) . ')';
1598                         }
1599                 } else {
1600                         $sql .= '(' . $this->makeList( $a ) . ')';
1601                 }
1602
1603                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1604                         return false;
1605                 } elseif ( $fh !== null ) {
1606                         return true;
1607                 }
1608
1609                 return (bool)$this->query( $sql, $fname );
1610         }
1611
1612         /**
1613          * Make UPDATE options array for Database::makeUpdateOptions
1614          *
1615          * @param array $options
1616          * @return array
1617          */
1618         protected function makeUpdateOptionsArray( $options ) {
1619                 if ( !is_array( $options ) ) {
1620                         $options = [ $options ];
1621                 }
1622
1623                 $opts = [];
1624
1625                 if ( in_array( 'IGNORE', $options ) ) {
1626                         $opts[] = 'IGNORE';
1627                 }
1628
1629                 return $opts;
1630         }
1631
1632         /**
1633          * Make UPDATE options for the Database::update function
1634          *
1635          * @param array $options The options passed to Database::update
1636          * @return string
1637          */
1638         protected function makeUpdateOptions( $options ) {
1639                 $opts = $this->makeUpdateOptionsArray( $options );
1640
1641                 return implode( ' ', $opts );
1642         }
1643
1644         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1645                 $table = $this->tableName( $table );
1646                 $opts = $this->makeUpdateOptions( $options );
1647                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
1648
1649                 if ( $conds !== [] && $conds !== '*' ) {
1650                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
1651                 }
1652
1653                 return (bool)$this->query( $sql, $fname );
1654         }
1655
1656         public function makeList( $a, $mode = self::LIST_COMMA ) {
1657                 if ( !is_array( $a ) ) {
1658                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1659                 }
1660
1661                 $first = true;
1662                 $list = '';
1663
1664                 foreach ( $a as $field => $value ) {
1665                         if ( !$first ) {
1666                                 if ( $mode == self::LIST_AND ) {
1667                                         $list .= ' AND ';
1668                                 } elseif ( $mode == self::LIST_OR ) {
1669                                         $list .= ' OR ';
1670                                 } else {
1671                                         $list .= ',';
1672                                 }
1673                         } else {
1674                                 $first = false;
1675                         }
1676
1677                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
1678                                 $list .= "($value)";
1679                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
1680                                 $list .= "$value";
1681                         } elseif (
1682                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
1683                         ) {
1684                                 // Remove null from array to be handled separately if found
1685                                 $includeNull = false;
1686                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
1687                                         $includeNull = true;
1688                                         unset( $value[$nullKey] );
1689                                 }
1690                                 if ( count( $value ) == 0 && !$includeNull ) {
1691                                         throw new InvalidArgumentException(
1692                                                 __METHOD__ . ": empty input for field $field" );
1693                                 } elseif ( count( $value ) == 0 ) {
1694                                         // only check if $field is null
1695                                         $list .= "$field IS NULL";
1696                                 } else {
1697                                         // IN clause contains at least one valid element
1698                                         if ( $includeNull ) {
1699                                                 // Group subconditions to ensure correct precedence
1700                                                 $list .= '(';
1701                                         }
1702                                         if ( count( $value ) == 1 ) {
1703                                                 // Special-case single values, as IN isn't terribly efficient
1704                                                 // Don't necessarily assume the single key is 0; we don't
1705                                                 // enforce linear numeric ordering on other arrays here.
1706                                                 $value = array_values( $value )[0];
1707                                                 $list .= $field . " = " . $this->addQuotes( $value );
1708                                         } else {
1709                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1710                                         }
1711                                         // if null present in array, append IS NULL
1712                                         if ( $includeNull ) {
1713                                                 $list .= " OR $field IS NULL)";
1714                                         }
1715                                 }
1716                         } elseif ( $value === null ) {
1717                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
1718                                         $list .= "$field IS ";
1719                                 } elseif ( $mode == self::LIST_SET ) {
1720                                         $list .= "$field = ";
1721                                 }
1722                                 $list .= 'NULL';
1723                         } else {
1724                                 if (
1725                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
1726                                 ) {
1727                                         $list .= "$field = ";
1728                                 }
1729                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
1730                         }
1731                 }
1732
1733                 return $list;
1734         }
1735
1736         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1737                 $conds = [];
1738
1739                 foreach ( $data as $base => $sub ) {
1740                         if ( count( $sub ) ) {
1741                                 $conds[] = $this->makeList(
1742                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
1743                                         self::LIST_AND );
1744                         }
1745                 }
1746
1747                 if ( $conds ) {
1748                         return $this->makeList( $conds, self::LIST_OR );
1749                 } else {
1750                         // Nothing to search for...
1751                         return false;
1752                 }
1753         }
1754
1755         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1756                 return $valuename;
1757         }
1758
1759         public function bitNot( $field ) {
1760                 return "(~$field)";
1761         }
1762
1763         public function bitAnd( $fieldLeft, $fieldRight ) {
1764                 return "($fieldLeft & $fieldRight)";
1765         }
1766
1767         public function bitOr( $fieldLeft, $fieldRight ) {
1768                 return "($fieldLeft | $fieldRight)";
1769         }
1770
1771         public function buildConcat( $stringList ) {
1772                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1773         }
1774
1775         public function buildGroupConcatField(
1776                 $delim, $table, $field, $conds = '', $join_conds = []
1777         ) {
1778                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
1779
1780                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
1781         }
1782
1783         public function buildStringCast( $field ) {
1784                 return $field;
1785         }
1786
1787         public function databasesAreIndependent() {
1788                 return false;
1789         }
1790
1791         public function selectDB( $db ) {
1792                 # Stub. Shouldn't cause serious problems if it's not overridden, but
1793                 # if your database engine supports a concept similar to MySQL's
1794                 # databases you may as well.
1795                 $this->mDBname = $db;
1796
1797                 return true;
1798         }
1799
1800         public function getDBname() {
1801                 return $this->mDBname;
1802         }
1803
1804         public function getServer() {
1805                 return $this->mServer;
1806         }
1807
1808         public function tableName( $name, $format = 'quoted' ) {
1809                 # Skip the entire process when we have a string quoted on both ends.
1810                 # Note that we check the end so that we will still quote any use of
1811                 # use of `database`.table. But won't break things if someone wants
1812                 # to query a database table with a dot in the name.
1813                 if ( $this->isQuotedIdentifier( $name ) ) {
1814                         return $name;
1815                 }
1816
1817                 # Lets test for any bits of text that should never show up in a table
1818                 # name. Basically anything like JOIN or ON which are actually part of
1819                 # SQL queries, but may end up inside of the table value to combine
1820                 # sql. Such as how the API is doing.
1821                 # Note that we use a whitespace test rather than a \b test to avoid
1822                 # any remote case where a word like on may be inside of a table name
1823                 # surrounded by symbols which may be considered word breaks.
1824                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1825                         return $name;
1826                 }
1827
1828                 # Split database and table into proper variables.
1829                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
1830
1831                 # Quote $table and apply the prefix if not quoted.
1832                 # $tableName might be empty if this is called from Database::replaceVars()
1833                 $tableName = "{$prefix}{$table}";
1834                 if ( $format === 'quoted'
1835                         && !$this->isQuotedIdentifier( $tableName )
1836                         && $tableName !== ''
1837                 ) {
1838                         $tableName = $this->addIdentifierQuotes( $tableName );
1839                 }
1840
1841                 # Quote $schema and $database and merge them with the table name if needed
1842                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
1843                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
1844
1845                 return $tableName;
1846         }
1847
1848         /**
1849          * Get the table components needed for a query given the currently selected database
1850          *
1851          * @param string $name Table name in the form of db.schema.table, db.table, or table
1852          * @return array (DB name or "" for default, schema name, table prefix, table name)
1853          */
1854         protected function qualifiedTableComponents( $name ) {
1855                 # We reverse the explode so that database.table and table both output the correct table.
1856                 $dbDetails = explode( '.', $name, 3 );
1857                 if ( count( $dbDetails ) == 3 ) {
1858                         list( $database, $schema, $table ) = $dbDetails;
1859                         # We don't want any prefix added in this case
1860                         $prefix = '';
1861                 } elseif ( count( $dbDetails ) == 2 ) {
1862                         list( $database, $table ) = $dbDetails;
1863                         # We don't want any prefix added in this case
1864                         $prefix = '';
1865                         # In dbs that support it, $database may actually be the schema
1866                         # but that doesn't affect any of the functionality here
1867                         $schema = '';
1868                 } else {
1869                         list( $table ) = $dbDetails;
1870                         if ( isset( $this->tableAliases[$table] ) ) {
1871                                 $database = $this->tableAliases[$table]['dbname'];
1872                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
1873                                         ? $this->tableAliases[$table]['schema']
1874                                         : $this->mSchema;
1875                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
1876                                         ? $this->tableAliases[$table]['prefix']
1877                                         : $this->mTablePrefix;
1878                         } else {
1879                                 $database = '';
1880                                 $schema = $this->mSchema; # Default schema
1881                                 $prefix = $this->mTablePrefix; # Default prefix
1882                         }
1883                 }
1884
1885                 return [ $database, $schema, $prefix, $table ];
1886         }
1887
1888         /**
1889          * @param string|null $namespace Database or schema
1890          * @param string $relation Name of table, view, sequence, etc...
1891          * @param string $format One of (raw, quoted)
1892          * @return string Relation name with quoted and merged $namespace as needed
1893          */
1894         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
1895                 if ( strlen( $namespace ) ) {
1896                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
1897                                 $namespace = $this->addIdentifierQuotes( $namespace );
1898                         }
1899                         $relation = $namespace . '.' . $relation;
1900                 }
1901
1902                 return $relation;
1903         }
1904
1905         public function tableNames() {
1906                 $inArray = func_get_args();
1907                 $retVal = [];
1908
1909                 foreach ( $inArray as $name ) {
1910                         $retVal[$name] = $this->tableName( $name );
1911                 }
1912
1913                 return $retVal;
1914         }
1915
1916         public function tableNamesN() {
1917                 $inArray = func_get_args();
1918                 $retVal = [];
1919
1920                 foreach ( $inArray as $name ) {
1921                         $retVal[] = $this->tableName( $name );
1922                 }
1923
1924                 return $retVal;
1925         }
1926
1927         /**
1928          * Get an aliased table name
1929          * e.g. tableName AS newTableName
1930          *
1931          * @param string $name Table name, see tableName()
1932          * @param string|bool $alias Alias (optional)
1933          * @return string SQL name for aliased table. Will not alias a table to its own name
1934          */
1935         protected function tableNameWithAlias( $name, $alias = false ) {
1936                 if ( !$alias || $alias == $name ) {
1937                         return $this->tableName( $name );
1938                 } else {
1939                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
1940                 }
1941         }
1942
1943         /**
1944          * Gets an array of aliased table names
1945          *
1946          * @param array $tables [ [alias] => table ]
1947          * @return string[] See tableNameWithAlias()
1948          */
1949         protected function tableNamesWithAlias( $tables ) {
1950                 $retval = [];
1951                 foreach ( $tables as $alias => $table ) {
1952                         if ( is_numeric( $alias ) ) {
1953                                 $alias = $table;
1954                         }
1955                         $retval[] = $this->tableNameWithAlias( $table, $alias );
1956                 }
1957
1958                 return $retval;
1959         }
1960
1961         /**
1962          * Get an aliased field name
1963          * e.g. fieldName AS newFieldName
1964          *
1965          * @param string $name Field name
1966          * @param string|bool $alias Alias (optional)
1967          * @return string SQL name for aliased field. Will not alias a field to its own name
1968          */
1969         protected function fieldNameWithAlias( $name, $alias = false ) {
1970                 if ( !$alias || (string)$alias === (string)$name ) {
1971                         return $name;
1972                 } else {
1973                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
1974                 }
1975         }
1976
1977         /**
1978          * Gets an array of aliased field names
1979          *
1980          * @param array $fields [ [alias] => field ]
1981          * @return string[] See fieldNameWithAlias()
1982          */
1983         protected function fieldNamesWithAlias( $fields ) {
1984                 $retval = [];
1985                 foreach ( $fields as $alias => $field ) {
1986                         if ( is_numeric( $alias ) ) {
1987                                 $alias = $field;
1988                         }
1989                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
1990                 }
1991
1992                 return $retval;
1993         }
1994
1995         /**
1996          * Get the aliased table name clause for a FROM clause
1997          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
1998          *
1999          * @param array $tables ( [alias] => table )
2000          * @param array $use_index Same as for select()
2001          * @param array $ignore_index Same as for select()
2002          * @param array $join_conds Same as for select()
2003          * @return string
2004          */
2005         protected function tableNamesWithIndexClauseOrJOIN(
2006                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2007         ) {
2008                 $ret = [];
2009                 $retJOIN = [];
2010                 $use_index = (array)$use_index;
2011                 $ignore_index = (array)$ignore_index;
2012                 $join_conds = (array)$join_conds;
2013
2014                 foreach ( $tables as $alias => $table ) {
2015                         if ( !is_string( $alias ) ) {
2016                                 // No alias? Set it equal to the table name
2017                                 $alias = $table;
2018                         }
2019
2020                         if ( is_array( $table ) ) {
2021                                 // A parenthesized group
2022                                 $joinedTable = '('
2023                                         . $this->tableNamesWithIndexClauseOrJOIN( $table, $use_index, $ignore_index, $join_conds )
2024                                         . ')';
2025                         } else {
2026                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2027                         }
2028
2029                         // Is there a JOIN clause for this table?
2030                         if ( isset( $join_conds[$alias] ) ) {
2031                                 list( $joinType, $conds ) = $join_conds[$alias];
2032                                 $tableClause = $joinType;
2033                                 $tableClause .= ' ' . $joinedTable;
2034                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2035                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2036                                         if ( $use != '' ) {
2037                                                 $tableClause .= ' ' . $use;
2038                                         }
2039                                 }
2040                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2041                                         $ignore = $this->ignoreIndexClause(
2042                                                 implode( ',', (array)$ignore_index[$alias] ) );
2043                                         if ( $ignore != '' ) {
2044                                                 $tableClause .= ' ' . $ignore;
2045                                         }
2046                                 }
2047                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2048                                 if ( $on != '' ) {
2049                                         $tableClause .= ' ON (' . $on . ')';
2050                                 }
2051
2052                                 $retJOIN[] = $tableClause;
2053                         } elseif ( isset( $use_index[$alias] ) ) {
2054                                 // Is there an INDEX clause for this table?
2055                                 $tableClause = $joinedTable;
2056                                 $tableClause .= ' ' . $this->useIndexClause(
2057                                                 implode( ',', (array)$use_index[$alias] )
2058                                         );
2059
2060                                 $ret[] = $tableClause;
2061                         } elseif ( isset( $ignore_index[$alias] ) ) {
2062                                 // Is there an INDEX clause for this table?
2063                                 $tableClause = $joinedTable;
2064                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2065                                                 implode( ',', (array)$ignore_index[$alias] )
2066                                         );
2067
2068                                 $ret[] = $tableClause;
2069                         } else {
2070                                 $tableClause = $joinedTable;
2071
2072                                 $ret[] = $tableClause;
2073                         }
2074                 }
2075
2076                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2077                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2078                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2079
2080                 // Compile our final table clause
2081                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2082         }
2083
2084         /**
2085          * Allows for index remapping in queries where this is not consistent across DBMS
2086          *
2087          * @param string $index
2088          * @return string
2089          */
2090         protected function indexName( $index ) {
2091                 return $index;
2092         }
2093
2094         public function addQuotes( $s ) {
2095                 if ( $s instanceof Blob ) {
2096                         $s = $s->fetch();
2097                 }
2098                 if ( $s === null ) {
2099                         return 'NULL';
2100                 } elseif ( is_bool( $s ) ) {
2101                         return (int)$s;
2102                 } else {
2103                         # This will also quote numeric values. This should be harmless,
2104                         # and protects against weird problems that occur when they really
2105                         # _are_ strings such as article titles and string->number->string
2106                         # conversion is not 1:1.
2107                         return "'" . $this->strencode( $s ) . "'";
2108                 }
2109         }
2110
2111         /**
2112          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2113          * MySQL uses `backticks` while basically everything else uses double quotes.
2114          * Since MySQL is the odd one out here the double quotes are our generic
2115          * and we implement backticks in DatabaseMysqlBase.
2116          *
2117          * @param string $s
2118          * @return string
2119          */
2120         public function addIdentifierQuotes( $s ) {
2121                 return '"' . str_replace( '"', '""', $s ) . '"';
2122         }
2123
2124         /**
2125          * Returns if the given identifier looks quoted or not according to
2126          * the database convention for quoting identifiers .
2127          *
2128          * @note Do not use this to determine if untrusted input is safe.
2129          *   A malicious user can trick this function.
2130          * @param string $name
2131          * @return bool
2132          */
2133         public function isQuotedIdentifier( $name ) {
2134                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2135         }
2136
2137         /**
2138          * @param string $s
2139          * @param string $escapeChar
2140          * @return string
2141          */
2142         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2143                 return str_replace( [ $escapeChar, '%', '_' ],
2144                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2145                         $s );
2146         }
2147
2148         public function buildLike() {
2149                 $params = func_get_args();
2150
2151                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2152                         $params = $params[0];
2153                 }
2154
2155                 $s = '';
2156
2157                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2158                 // may escape backslashes, creating problems of double escaping. The `
2159                 // character has good cross-DBMS compatibility, avoiding special operators
2160                 // in MS SQL like ^ and %
2161                 $escapeChar = '`';
2162
2163                 foreach ( $params as $value ) {
2164                         if ( $value instanceof LikeMatch ) {
2165                                 $s .= $value->toString();
2166                         } else {
2167                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2168                         }
2169                 }
2170
2171                 return ' LIKE ' . $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2172         }
2173
2174         public function anyChar() {
2175                 return new LikeMatch( '_' );
2176         }
2177
2178         public function anyString() {
2179                 return new LikeMatch( '%' );
2180         }
2181
2182         public function nextSequenceValue( $seqName ) {
2183                 return null;
2184         }
2185
2186         /**
2187          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2188          * is only needed because a) MySQL must be as efficient as possible due to
2189          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2190          * which index to pick. Anyway, other databases might have different
2191          * indexes on a given table. So don't bother overriding this unless you're
2192          * MySQL.
2193          * @param string $index
2194          * @return string
2195          */
2196         public function useIndexClause( $index ) {
2197                 return '';
2198         }
2199
2200         /**
2201          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2202          * is only needed because a) MySQL must be as efficient as possible due to
2203          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2204          * which index to pick. Anyway, other databases might have different
2205          * indexes on a given table. So don't bother overriding this unless you're
2206          * MySQL.
2207          * @param string $index
2208          * @return string
2209          */
2210         public function ignoreIndexClause( $index ) {
2211                 return '';
2212         }
2213
2214         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2215                 $quotedTable = $this->tableName( $table );
2216
2217                 if ( count( $rows ) == 0 ) {
2218                         return;
2219                 }
2220
2221                 # Single row case
2222                 if ( !is_array( reset( $rows ) ) ) {
2223                         $rows = [ $rows ];
2224                 }
2225
2226                 // @FXIME: this is not atomic, but a trx would break affectedRows()
2227                 foreach ( $rows as $row ) {
2228                         # Delete rows which collide
2229                         if ( $uniqueIndexes ) {
2230                                 $sql = "DELETE FROM $quotedTable WHERE ";
2231                                 $first = true;
2232                                 foreach ( $uniqueIndexes as $index ) {
2233                                         if ( $first ) {
2234                                                 $first = false;
2235                                                 $sql .= '( ';
2236                                         } else {
2237                                                 $sql .= ' ) OR ( ';
2238                                         }
2239                                         if ( is_array( $index ) ) {
2240                                                 $first2 = true;
2241                                                 foreach ( $index as $col ) {
2242                                                         if ( $first2 ) {
2243                                                                 $first2 = false;
2244                                                         } else {
2245                                                                 $sql .= ' AND ';
2246                                                         }
2247                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2248                                                 }
2249                                         } else {
2250                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2251                                         }
2252                                 }
2253                                 $sql .= ' )';
2254                                 $this->query( $sql, $fname );
2255                         }
2256
2257                         # Now insert the row
2258                         $this->insert( $table, $row, $fname );
2259                 }
2260         }
2261
2262         /**
2263          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2264          * statement.
2265          *
2266          * @param string $table Table name
2267          * @param array|string $rows Row(s) to insert
2268          * @param string $fname Caller function name
2269          *
2270          * @return ResultWrapper
2271          */
2272         protected function nativeReplace( $table, $rows, $fname ) {
2273                 $table = $this->tableName( $table );
2274
2275                 # Single row case
2276                 if ( !is_array( reset( $rows ) ) ) {
2277                         $rows = [ $rows ];
2278                 }
2279
2280                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2281                 $first = true;
2282
2283                 foreach ( $rows as $row ) {
2284                         if ( $first ) {
2285                                 $first = false;
2286                         } else {
2287                                 $sql .= ',';
2288                         }
2289
2290                         $sql .= '(' . $this->makeList( $row ) . ')';
2291                 }
2292
2293                 return $this->query( $sql, $fname );
2294         }
2295
2296         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2297                 $fname = __METHOD__
2298         ) {
2299                 if ( !count( $rows ) ) {
2300                         return true; // nothing to do
2301                 }
2302
2303                 if ( !is_array( reset( $rows ) ) ) {
2304                         $rows = [ $rows ];
2305                 }
2306
2307                 if ( count( $uniqueIndexes ) ) {
2308                         $clauses = []; // list WHERE clauses that each identify a single row
2309                         foreach ( $rows as $row ) {
2310                                 foreach ( $uniqueIndexes as $index ) {
2311                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2312                                         $rowKey = []; // unique key to this row
2313                                         foreach ( $index as $column ) {
2314                                                 $rowKey[$column] = $row[$column];
2315                                         }
2316                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2317                                 }
2318                         }
2319                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2320                 } else {
2321                         $where = false;
2322                 }
2323
2324                 $useTrx = !$this->mTrxLevel;
2325                 if ( $useTrx ) {
2326                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2327                 }
2328                 try {
2329                         # Update any existing conflicting row(s)
2330                         if ( $where !== false ) {
2331                                 $ok = $this->update( $table, $set, $where, $fname );
2332                         } else {
2333                                 $ok = true;
2334                         }
2335                         # Now insert any non-conflicting row(s)
2336                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2337                 } catch ( Exception $e ) {
2338                         if ( $useTrx ) {
2339                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
2340                         }
2341                         throw $e;
2342                 }
2343                 if ( $useTrx ) {
2344                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2345                 }
2346
2347                 return $ok;
2348         }
2349
2350         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2351                 $fname = __METHOD__
2352         ) {
2353                 if ( !$conds ) {
2354                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2355                 }
2356
2357                 $delTable = $this->tableName( $delTable );
2358                 $joinTable = $this->tableName( $joinTable );
2359                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2360                 if ( $conds != '*' ) {
2361                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2362                 }
2363                 $sql .= ')';
2364
2365                 $this->query( $sql, $fname );
2366         }
2367
2368         public function textFieldSize( $table, $field ) {
2369                 $table = $this->tableName( $table );
2370                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2371                 $res = $this->query( $sql, __METHOD__ );
2372                 $row = $this->fetchObject( $res );
2373
2374                 $m = [];
2375
2376                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2377                         $size = $m[1];
2378                 } else {
2379                         $size = -1;
2380                 }
2381
2382                 return $size;
2383         }
2384
2385         public function delete( $table, $conds, $fname = __METHOD__ ) {
2386                 if ( !$conds ) {
2387                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2388                 }
2389
2390                 $table = $this->tableName( $table );
2391                 $sql = "DELETE FROM $table";
2392
2393                 if ( $conds != '*' ) {
2394                         if ( is_array( $conds ) ) {
2395                                 $conds = $this->makeList( $conds, self::LIST_AND );
2396                         }
2397                         $sql .= ' WHERE ' . $conds;
2398                 }
2399
2400                 return $this->query( $sql, $fname );
2401         }
2402
2403         public function insertSelect(
2404                 $destTable, $srcTable, $varMap, $conds,
2405                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2406         ) {
2407                 if ( $this->cliMode ) {
2408                         // For massive migrations with downtime, we don't want to select everything
2409                         // into memory and OOM, so do all this native on the server side if possible.
2410                         return $this->nativeInsertSelect(
2411                                 $destTable,
2412                                 $srcTable,
2413                                 $varMap,
2414                                 $conds,
2415                                 $fname,
2416                                 $insertOptions,
2417                                 $selectOptions,
2418                                 $selectJoinConds
2419                         );
2420                 }
2421
2422                 return $this->nonNativeInsertSelect(
2423                         $destTable,
2424                         $srcTable,
2425                         $varMap,
2426                         $conds,
2427                         $fname,
2428                         $insertOptions,
2429                         $selectOptions,
2430                         $selectJoinConds
2431                 );
2432         }
2433
2434         /**
2435          * Implementation of insertSelect() based on select() and insert()
2436          *
2437          * @see IDatabase::insertSelect()
2438          * @since 1.30
2439          * @param string $destTable
2440          * @param string|array $srcTable
2441          * @param array $varMap
2442          * @param array $conds
2443          * @param string $fname
2444          * @param array $insertOptions
2445          * @param array $selectOptions
2446          * @param array $selectJoinConds
2447          * @return bool
2448          */
2449         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2450                 $fname = __METHOD__,
2451                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2452         ) {
2453                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
2454                 // on only the master (without needing row-based-replication). It also makes it easy to
2455                 // know how big the INSERT is going to be.
2456                 $fields = [];
2457                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
2458                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
2459                 }
2460                 $selectOptions[] = 'FOR UPDATE';
2461                 $res = $this->select(
2462                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
2463                 );
2464                 if ( !$res ) {
2465                         return false;
2466                 }
2467
2468                 $rows = [];
2469                 foreach ( $res as $row ) {
2470                         $rows[] = (array)$row;
2471                 }
2472
2473                 return $this->insert( $destTable, $rows, $fname, $insertOptions );
2474         }
2475
2476         /**
2477          * Native server-side implementation of insertSelect() for situations where
2478          * we don't want to select everything into memory
2479          *
2480          * @see IDatabase::insertSelect()
2481          * @param string $destTable
2482          * @param string|array $srcTable
2483          * @param array $varMap
2484          * @param array $conds
2485          * @param string $fname
2486          * @param array $insertOptions
2487          * @param array $selectOptions
2488          * @param array $selectJoinConds
2489          * @return bool
2490          */
2491         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2492                 $fname = __METHOD__,
2493                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2494         ) {
2495                 $destTable = $this->tableName( $destTable );
2496
2497                 if ( !is_array( $insertOptions ) ) {
2498                         $insertOptions = [ $insertOptions ];
2499                 }
2500
2501                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2502
2503                 $selectSql = $this->selectSQLText(
2504                         $srcTable,
2505                         array_values( $varMap ),
2506                         $conds,
2507                         $fname,
2508                         $selectOptions,
2509                         $selectJoinConds
2510                 );
2511
2512                 $sql = "INSERT $insertOptions" .
2513                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
2514                         $selectSql;
2515
2516                 return $this->query( $sql, $fname );
2517         }
2518
2519         /**
2520          * Construct a LIMIT query with optional offset. This is used for query
2521          * pages. The SQL should be adjusted so that only the first $limit rows
2522          * are returned. If $offset is provided as well, then the first $offset
2523          * rows should be discarded, and the next $limit rows should be returned.
2524          * If the result of the query is not ordered, then the rows to be returned
2525          * are theoretically arbitrary.
2526          *
2527          * $sql is expected to be a SELECT, if that makes a difference.
2528          *
2529          * The version provided by default works in MySQL and SQLite. It will very
2530          * likely need to be overridden for most other DBMSes.
2531          *
2532          * @param string $sql SQL query we will append the limit too
2533          * @param int $limit The SQL limit
2534          * @param int|bool $offset The SQL offset (default false)
2535          * @throws DBUnexpectedError
2536          * @return string
2537          */
2538         public function limitResult( $sql, $limit, $offset = false ) {
2539                 if ( !is_numeric( $limit ) ) {
2540                         throw new DBUnexpectedError( $this,
2541                                 "Invalid non-numeric limit passed to limitResult()\n" );
2542                 }
2543
2544                 return "$sql LIMIT "
2545                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2546                 . "{$limit} ";
2547         }
2548
2549         public function unionSupportsOrderAndLimit() {
2550                 return true; // True for almost every DB supported
2551         }
2552
2553         public function unionQueries( $sqls, $all ) {
2554                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2555
2556                 return '(' . implode( $glue, $sqls ) . ')';
2557         }
2558
2559         public function unionConditionPermutations(
2560                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
2561                 $options = [], $join_conds = []
2562         ) {
2563                 // First, build the Cartesian product of $permute_conds
2564                 $conds = [ [] ];
2565                 foreach ( $permute_conds as $field => $values ) {
2566                         if ( !$values ) {
2567                                 // Skip empty $values
2568                                 continue;
2569                         }
2570                         $values = array_unique( $values ); // For sanity
2571                         $newConds = [];
2572                         foreach ( $conds as $cond ) {
2573                                 foreach ( $values as $value ) {
2574                                         $cond[$field] = $value;
2575                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
2576                                 }
2577                         }
2578                         $conds = $newConds;
2579                 }
2580
2581                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
2582
2583                 // If there's just one condition and no subordering, hand off to
2584                 // selectSQLText directly.
2585                 if ( count( $conds ) === 1 &&
2586                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
2587                 ) {
2588                         return $this->selectSQLText(
2589                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
2590                         );
2591                 }
2592
2593                 // Otherwise, we need to pull out the order and limit to apply after
2594                 // the union. Then build the SQL queries for each set of conditions in
2595                 // $conds. Then union them together (using UNION ALL, because the
2596                 // product *should* already be distinct).
2597                 $orderBy = $this->makeOrderBy( $options );
2598                 $limit = isset( $options['LIMIT'] ) ? $options['LIMIT'] : null;
2599                 $offset = isset( $options['OFFSET'] ) ? $options['OFFSET'] : false;
2600                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
2601                 if ( !$this->unionSupportsOrderAndLimit() ) {
2602                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
2603                 } else {
2604                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
2605                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
2606                         }
2607                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
2608                                 // We need to increase the limit by the offset rather than
2609                                 // using the offset directly, otherwise it'll skip incorrectly
2610                                 // in the subqueries.
2611                                 $options['LIMIT'] = $limit + $offset;
2612                                 unset( $options['OFFSET'] );
2613                         }
2614                 }
2615
2616                 $sqls = [];
2617                 foreach ( $conds as $cond ) {
2618                         $sqls[] = $this->selectSQLText(
2619                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
2620                         );
2621                 }
2622                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
2623                 if ( $limit !== null ) {
2624                         $sql = $this->limitResult( $sql, $limit, $offset );
2625                 }
2626
2627                 return $sql;
2628         }
2629
2630         public function conditional( $cond, $trueVal, $falseVal ) {
2631                 if ( is_array( $cond ) ) {
2632                         $cond = $this->makeList( $cond, self::LIST_AND );
2633                 }
2634
2635                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2636         }
2637
2638         public function strreplace( $orig, $old, $new ) {
2639                 return "REPLACE({$orig}, {$old}, {$new})";
2640         }
2641
2642         public function getServerUptime() {
2643                 return 0;
2644         }
2645
2646         public function wasDeadlock() {
2647                 return false;
2648         }
2649
2650         public function wasLockTimeout() {
2651                 return false;
2652         }
2653
2654         public function wasErrorReissuable() {
2655                 return false;
2656         }
2657
2658         public function wasReadOnlyError() {
2659                 return false;
2660         }
2661
2662         /**
2663          * Do not use this method outside of Database/DBError classes
2664          *
2665          * @param int|string $errno
2666          * @return bool Whether the given query error was a connection drop
2667          */
2668         public function wasConnectionError( $errno ) {
2669                 return false;
2670         }
2671
2672         public function deadlockLoop() {
2673                 $args = func_get_args();
2674                 $function = array_shift( $args );
2675                 $tries = self::DEADLOCK_TRIES;
2676
2677                 $this->begin( __METHOD__ );
2678
2679                 $retVal = null;
2680                 /** @var Exception $e */
2681                 $e = null;
2682                 do {
2683                         try {
2684                                 $retVal = call_user_func_array( $function, $args );
2685                                 break;
2686                         } catch ( DBQueryError $e ) {
2687                                 if ( $this->wasDeadlock() ) {
2688                                         // Retry after a randomized delay
2689                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
2690                                 } else {
2691                                         // Throw the error back up
2692                                         throw $e;
2693                                 }
2694                         }
2695                 } while ( --$tries > 0 );
2696
2697                 if ( $tries <= 0 ) {
2698                         // Too many deadlocks; give up
2699                         $this->rollback( __METHOD__ );
2700                         throw $e;
2701                 } else {
2702                         $this->commit( __METHOD__ );
2703
2704                         return $retVal;
2705                 }
2706         }
2707
2708         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2709                 # Real waits are implemented in the subclass.
2710                 return 0;
2711         }
2712
2713         public function getReplicaPos() {
2714                 # Stub
2715                 return false;
2716         }
2717
2718         public function getMasterPos() {
2719                 # Stub
2720                 return false;
2721         }
2722
2723         public function serverIsReadOnly() {
2724                 return false;
2725         }
2726
2727         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
2728                 if ( !$this->mTrxLevel ) {
2729                         throw new DBUnexpectedError( $this, "No transaction is active." );
2730                 }
2731                 $this->mTrxEndCallbacks[] = [ $callback, $fname ];
2732         }
2733
2734         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
2735                 $this->mTrxIdleCallbacks[] = [ $callback, $fname ];
2736                 if ( !$this->mTrxLevel ) {
2737                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
2738                 }
2739         }
2740
2741         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
2742                 if ( $this->mTrxLevel || $this->getFlag( self::DBO_TRX ) ) {
2743                         // As long as DBO_TRX is set, writes will accumulate until the load balancer issues
2744                         // an implicit commit of all peer databases. This is true even if a transaction has
2745                         // not yet been triggered by writes; make sure $callback runs *after* any such writes.
2746                         $this->mTrxPreCommitCallbacks[] = [ $callback, $fname ];
2747                 } else {
2748                         // No transaction is active nor will start implicitly, so make one for this callback
2749                         $this->startAtomic( __METHOD__ );
2750                         try {
2751                                 call_user_func( $callback );
2752                                 $this->endAtomic( __METHOD__ );
2753                         } catch ( Exception $e ) {
2754                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2755                                 throw $e;
2756                         }
2757                 }
2758         }
2759
2760         final public function setTransactionListener( $name, callable $callback = null ) {
2761                 if ( $callback ) {
2762                         $this->mTrxRecurringCallbacks[$name] = $callback;
2763                 } else {
2764                         unset( $this->mTrxRecurringCallbacks[$name] );
2765                 }
2766         }
2767
2768         /**
2769          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
2770          *
2771          * This method should not be used outside of Database/LoadBalancer
2772          *
2773          * @param bool $suppress
2774          * @since 1.28
2775          */
2776         final public function setTrxEndCallbackSuppression( $suppress ) {
2777                 $this->mTrxEndCallbacksSuppressed = $suppress;
2778         }
2779
2780         /**
2781          * Actually run and consume any "on transaction idle/resolution" callbacks.
2782          *
2783          * This method should not be used outside of Database/LoadBalancer
2784          *
2785          * @param int $trigger IDatabase::TRIGGER_* constant
2786          * @since 1.20
2787          * @throws Exception
2788          */
2789         public function runOnTransactionIdleCallbacks( $trigger ) {
2790                 if ( $this->mTrxEndCallbacksSuppressed ) {
2791                         return;
2792                 }
2793
2794                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
2795                 /** @var Exception $e */
2796                 $e = null; // first exception
2797                 do { // callbacks may add callbacks :)
2798                         $callbacks = array_merge(
2799                                 $this->mTrxIdleCallbacks,
2800                                 $this->mTrxEndCallbacks // include "transaction resolution" callbacks
2801                         );
2802                         $this->mTrxIdleCallbacks = []; // consumed (and recursion guard)
2803                         $this->mTrxEndCallbacks = []; // consumed (recursion guard)
2804                         foreach ( $callbacks as $callback ) {
2805                                 try {
2806                                         list( $phpCallback ) = $callback;
2807                                         $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
2808                                         call_user_func_array( $phpCallback, [ $trigger ] );
2809                                         if ( $autoTrx ) {
2810                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
2811                                         } else {
2812                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
2813                                         }
2814                                 } catch ( Exception $ex ) {
2815                                         call_user_func( $this->errorLogger, $ex );
2816                                         $e = $e ?: $ex;
2817                                         // Some callbacks may use startAtomic/endAtomic, so make sure
2818                                         // their transactions are ended so other callbacks don't fail
2819                                         if ( $this->trxLevel() ) {
2820                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2821                                         }
2822                                 }
2823                         }
2824                 } while ( count( $this->mTrxIdleCallbacks ) );
2825
2826                 if ( $e instanceof Exception ) {
2827                         throw $e; // re-throw any first exception
2828                 }
2829         }
2830
2831         /**
2832          * Actually run and consume any "on transaction pre-commit" callbacks.
2833          *
2834          * This method should not be used outside of Database/LoadBalancer
2835          *
2836          * @since 1.22
2837          * @throws Exception
2838          */
2839         public function runOnTransactionPreCommitCallbacks() {
2840                 $e = null; // first exception
2841                 do { // callbacks may add callbacks :)
2842                         $callbacks = $this->mTrxPreCommitCallbacks;
2843                         $this->mTrxPreCommitCallbacks = []; // consumed (and recursion guard)
2844                         foreach ( $callbacks as $callback ) {
2845                                 try {
2846                                         list( $phpCallback ) = $callback;
2847                                         call_user_func( $phpCallback );
2848                                 } catch ( Exception $ex ) {
2849                                         call_user_func( $this->errorLogger, $ex );
2850                                         $e = $e ?: $ex;
2851                                 }
2852                         }
2853                 } while ( count( $this->mTrxPreCommitCallbacks ) );
2854
2855                 if ( $e instanceof Exception ) {
2856                         throw $e; // re-throw any first exception
2857                 }
2858         }
2859
2860         /**
2861          * Actually run any "transaction listener" callbacks.
2862          *
2863          * This method should not be used outside of Database/LoadBalancer
2864          *
2865          * @param int $trigger IDatabase::TRIGGER_* constant
2866          * @throws Exception
2867          * @since 1.20
2868          */
2869         public function runTransactionListenerCallbacks( $trigger ) {
2870                 if ( $this->mTrxEndCallbacksSuppressed ) {
2871                         return;
2872                 }
2873
2874                 /** @var Exception $e */
2875                 $e = null; // first exception
2876
2877                 foreach ( $this->mTrxRecurringCallbacks as $phpCallback ) {
2878                         try {
2879                                 $phpCallback( $trigger, $this );
2880                         } catch ( Exception $ex ) {
2881                                 call_user_func( $this->errorLogger, $ex );
2882                                 $e = $e ?: $ex;
2883                         }
2884                 }
2885
2886                 if ( $e instanceof Exception ) {
2887                         throw $e; // re-throw any first exception
2888                 }
2889         }
2890
2891         final public function startAtomic( $fname = __METHOD__ ) {
2892                 if ( !$this->mTrxLevel ) {
2893                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2894                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
2895                         // in all changes being in one transaction to keep requests transactional.
2896                         if ( !$this->getFlag( self::DBO_TRX ) ) {
2897                                 $this->mTrxAutomaticAtomic = true;
2898                         }
2899                 }
2900
2901                 $this->mTrxAtomicLevels[] = $fname;
2902         }
2903
2904         final public function endAtomic( $fname = __METHOD__ ) {
2905                 if ( !$this->mTrxLevel ) {
2906                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
2907                 }
2908                 if ( !$this->mTrxAtomicLevels ||
2909                         array_pop( $this->mTrxAtomicLevels ) !== $fname
2910                 ) {
2911                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
2912                 }
2913
2914                 if ( !$this->mTrxAtomicLevels && $this->mTrxAutomaticAtomic ) {
2915                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2916                 }
2917         }
2918
2919         final public function doAtomicSection( $fname, callable $callback ) {
2920                 $this->startAtomic( $fname );
2921                 try {
2922                         $res = call_user_func_array( $callback, [ $this, $fname ] );
2923                 } catch ( Exception $e ) {
2924                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2925                         throw $e;
2926                 }
2927                 $this->endAtomic( $fname );
2928
2929                 return $res;
2930         }
2931
2932         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
2933                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
2934                 if ( $this->mTrxLevel ) {
2935                         if ( $this->mTrxAtomicLevels ) {
2936                                 $levels = implode( ', ', $this->mTrxAtomicLevels );
2937                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
2938                                 throw new DBUnexpectedError( $this, $msg );
2939                         } elseif ( !$this->mTrxAutomatic ) {
2940                                 $msg = "$fname: Explicit transaction already active (from {$this->mTrxFname}).";
2941                                 throw new DBUnexpectedError( $this, $msg );
2942                         } else {
2943                                 // @TODO: make this an exception at some point
2944                                 $msg = "$fname: Implicit transaction already active (from {$this->mTrxFname}).";
2945                                 $this->queryLogger->error( $msg );
2946                                 return; // join the main transaction set
2947                         }
2948                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
2949                         // @TODO: make this an exception at some point
2950                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
2951                         $this->queryLogger->error( $msg );
2952                         return; // let any writes be in the main transaction
2953                 }
2954
2955                 // Avoid fatals if close() was called
2956                 $this->assertOpen();
2957
2958                 $this->doBegin( $fname );
2959                 $this->mTrxTimestamp = microtime( true );
2960                 $this->mTrxFname = $fname;
2961                 $this->mTrxDoneWrites = false;
2962                 $this->mTrxAutomaticAtomic = false;
2963                 $this->mTrxAtomicLevels = [];
2964                 $this->mTrxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
2965                 $this->mTrxWriteDuration = 0.0;
2966                 $this->mTrxWriteQueryCount = 0;
2967                 $this->mTrxWriteAffectedRows = 0;
2968                 $this->mTrxWriteAdjDuration = 0.0;
2969                 $this->mTrxWriteAdjQueryCount = 0;
2970                 $this->mTrxWriteCallers = [];
2971                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
2972                 // Get an estimate of the replica DB lag before then, treating estimate staleness
2973                 // as lag itself just to be safe
2974                 $status = $this->getApproximateLagStatus();
2975                 $this->mTrxReplicaLag = $status['lag'] + ( microtime( true ) - $status['since'] );
2976                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
2977                 // caller will think its OK to muck around with the transaction just because startAtomic()
2978                 // has not yet completed (e.g. setting mTrxAtomicLevels).
2979                 $this->mTrxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
2980         }
2981
2982         /**
2983          * Issues the BEGIN command to the database server.
2984          *
2985          * @see Database::begin()
2986          * @param string $fname
2987          */
2988         protected function doBegin( $fname ) {
2989                 $this->query( 'BEGIN', $fname );
2990                 $this->mTrxLevel = 1;
2991         }
2992
2993         final public function commit( $fname = __METHOD__, $flush = '' ) {
2994                 if ( $this->mTrxLevel && $this->mTrxAtomicLevels ) {
2995                         // There are still atomic sections open. This cannot be ignored
2996                         $levels = implode( ', ', $this->mTrxAtomicLevels );
2997                         throw new DBUnexpectedError(
2998                                 $this,
2999                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3000                         );
3001                 }
3002
3003                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3004                         if ( !$this->mTrxLevel ) {
3005                                 return; // nothing to do
3006                         } elseif ( !$this->mTrxAutomatic ) {
3007                                 throw new DBUnexpectedError(
3008                                         $this,
3009                                         "$fname: Flushing an explicit transaction, getting out of sync."
3010                                 );
3011                         }
3012                 } else {
3013                         if ( !$this->mTrxLevel ) {
3014                                 $this->queryLogger->error(
3015                                         "$fname: No transaction to commit, something got out of sync." );
3016                                 return; // nothing to do
3017                         } elseif ( $this->mTrxAutomatic ) {
3018                                 // @TODO: make this an exception at some point
3019                                 $msg = "$fname: Explicit commit of implicit transaction.";
3020                                 $this->queryLogger->error( $msg );
3021                                 return; // wait for the main transaction set commit round
3022                         }
3023                 }
3024
3025                 // Avoid fatals if close() was called
3026                 $this->assertOpen();
3027
3028                 $this->runOnTransactionPreCommitCallbacks();
3029                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3030                 $this->doCommit( $fname );
3031                 if ( $this->mTrxDoneWrites ) {
3032                         $this->mLastWriteTime = microtime( true );
3033                         $this->trxProfiler->transactionWritingOut(
3034                                 $this->mServer,
3035                                 $this->mDBname,
3036                                 $this->mTrxShortId,
3037                                 $writeTime,
3038                                 $this->mTrxWriteAffectedRows
3039                         );
3040                 }
3041
3042                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3043                 $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3044         }
3045
3046         /**
3047          * Issues the COMMIT command to the database server.
3048          *
3049          * @see Database::commit()
3050          * @param string $fname
3051          */
3052         protected function doCommit( $fname ) {
3053                 if ( $this->mTrxLevel ) {
3054                         $this->query( 'COMMIT', $fname );
3055                         $this->mTrxLevel = 0;
3056                 }
3057         }
3058
3059         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3060                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3061                         if ( !$this->mTrxLevel ) {
3062                                 return; // nothing to do
3063                         }
3064                 } else {
3065                         if ( !$this->mTrxLevel ) {
3066                                 $this->queryLogger->error(
3067                                         "$fname: No transaction to rollback, something got out of sync." );
3068                                 return; // nothing to do
3069                         } elseif ( $this->getFlag( self::DBO_TRX ) ) {
3070                                 throw new DBUnexpectedError(
3071                                         $this,
3072                                         "$fname: Expected mass rollback of all peer databases (DBO_TRX set)."
3073                                 );
3074                         }
3075                 }
3076
3077                 // Avoid fatals if close() was called
3078                 $this->assertOpen();
3079
3080                 $this->doRollback( $fname );
3081                 $this->mTrxAtomicLevels = [];
3082                 if ( $this->mTrxDoneWrites ) {
3083                         $this->trxProfiler->transactionWritingOut(
3084                                 $this->mServer,
3085                                 $this->mDBname,
3086                                 $this->mTrxShortId
3087                         );
3088                 }
3089
3090                 $this->mTrxIdleCallbacks = []; // clear
3091                 $this->mTrxPreCommitCallbacks = []; // clear
3092                 try {
3093                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
3094                 } catch ( Exception $e ) {
3095                         // already logged; finish and let LoadBalancer move on during mass-rollback
3096                 }
3097                 try {
3098                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
3099                 } catch ( Exception $e ) {
3100                         // already logged; let LoadBalancer move on during mass-rollback
3101                 }
3102         }
3103
3104         /**
3105          * Issues the ROLLBACK command to the database server.
3106          *
3107          * @see Database::rollback()
3108          * @param string $fname
3109          */
3110         protected function doRollback( $fname ) {
3111                 if ( $this->mTrxLevel ) {
3112                         # Disconnects cause rollback anyway, so ignore those errors
3113                         $ignoreErrors = true;
3114                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
3115                         $this->mTrxLevel = 0;
3116                 }
3117         }
3118
3119         public function flushSnapshot( $fname = __METHOD__ ) {
3120                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
3121                         // This only flushes transactions to clear snapshots, not to write data
3122                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3123                         throw new DBUnexpectedError(
3124                                 $this,
3125                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
3126                         );
3127                 }
3128
3129                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3130         }
3131
3132         public function explicitTrxActive() {
3133                 return $this->mTrxLevel && ( $this->mTrxAtomicLevels || !$this->mTrxAutomatic );
3134         }
3135
3136         public function duplicateTableStructure(
3137                 $oldName, $newName, $temporary = false, $fname = __METHOD__
3138         ) {
3139                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3140         }
3141
3142         public function listTables( $prefix = null, $fname = __METHOD__ ) {
3143                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3144         }
3145
3146         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3147                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3148         }
3149
3150         public function timestamp( $ts = 0 ) {
3151                 $t = new ConvertibleTimestamp( $ts );
3152                 // Let errors bubble up to avoid putting garbage in the DB
3153                 return $t->getTimestamp( TS_MW );
3154         }
3155
3156         public function timestampOrNull( $ts = null ) {
3157                 if ( is_null( $ts ) ) {
3158                         return null;
3159                 } else {
3160                         return $this->timestamp( $ts );
3161                 }
3162         }
3163
3164         /**
3165          * Take the result from a query, and wrap it in a ResultWrapper if
3166          * necessary. Boolean values are passed through as is, to indicate success
3167          * of write queries or failure.
3168          *
3169          * Once upon a time, Database::query() returned a bare MySQL result
3170          * resource, and it was necessary to call this function to convert it to
3171          * a wrapper. Nowadays, raw database objects are never exposed to external
3172          * callers, so this is unnecessary in external code.
3173          *
3174          * @param bool|ResultWrapper|resource|object $result
3175          * @return bool|ResultWrapper
3176          */
3177         protected function resultObject( $result ) {
3178                 if ( !$result ) {
3179                         return false;
3180                 } elseif ( $result instanceof ResultWrapper ) {
3181                         return $result;
3182                 } elseif ( $result === true ) {
3183                         // Successful write query
3184                         return $result;
3185                 } else {
3186                         return new ResultWrapper( $this, $result );
3187                 }
3188         }
3189
3190         public function ping( &$rtt = null ) {
3191                 // Avoid hitting the server if it was hit recently
3192                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
3193                         if ( !func_num_args() || $this->mRTTEstimate > 0 ) {
3194                                 $rtt = $this->mRTTEstimate;
3195                                 return true; // don't care about $rtt
3196                         }
3197                 }
3198
3199                 // This will reconnect if possible or return false if not
3200                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
3201                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
3202                 $this->restoreFlags( self::RESTORE_PRIOR );
3203
3204                 if ( $ok ) {
3205                         $rtt = $this->mRTTEstimate;
3206                 }
3207
3208                 return $ok;
3209         }
3210
3211         /**
3212          * Close existing database connection and open a new connection
3213          *
3214          * @return bool True if new connection is opened successfully, false if error
3215          */
3216         protected function reconnect() {
3217                 $this->closeConnection();
3218                 $this->mOpened = false;
3219                 $this->mConn = false;
3220                 try {
3221                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3222                         $this->lastPing = microtime( true );
3223                         $ok = true;
3224                 } catch ( DBConnectionError $e ) {
3225                         $ok = false;
3226                 }
3227
3228                 return $ok;
3229         }
3230
3231         public function getSessionLagStatus() {
3232                 return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
3233         }
3234
3235         /**
3236          * Get the replica DB lag when the current transaction started
3237          *
3238          * This is useful when transactions might use snapshot isolation
3239          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
3240          * is this lag plus transaction duration. If they don't, it is still
3241          * safe to be pessimistic. This returns null if there is no transaction.
3242          *
3243          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
3244          * @since 1.27
3245          */
3246         protected function getTransactionLagStatus() {
3247                 return $this->mTrxLevel
3248                         ? [ 'lag' => $this->mTrxReplicaLag, 'since' => $this->trxTimestamp() ]
3249                         : null;
3250         }
3251
3252         /**
3253          * Get a replica DB lag estimate for this server
3254          *
3255          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
3256          * @since 1.27
3257          */
3258         protected function getApproximateLagStatus() {
3259                 return [
3260                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
3261                         'since' => microtime( true )
3262                 ];
3263         }
3264
3265         /**
3266          * Merge the result of getSessionLagStatus() for several DBs
3267          * using the most pessimistic values to estimate the lag of
3268          * any data derived from them in combination
3269          *
3270          * This is information is useful for caching modules
3271          *
3272          * @see WANObjectCache::set()
3273          * @see WANObjectCache::getWithSetCallback()
3274          *
3275          * @param IDatabase $db1
3276          * @param IDatabase $dbs,...
3277          * @return array Map of values:
3278          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3279          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3280          *   - pending: whether any of the DBs have uncommitted changes
3281          * @since 1.27
3282          */
3283         public static function getCacheSetOptions( IDatabase $db1 ) {
3284                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3285                 foreach ( func_get_args() as $db ) {
3286                         /** @var IDatabase $db */
3287                         $status = $db->getSessionLagStatus();
3288                         if ( $status['lag'] === false ) {
3289                                 $res['lag'] = false;
3290                         } elseif ( $res['lag'] !== false ) {
3291                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3292                         }
3293                         $res['since'] = min( $res['since'], $status['since'] );
3294                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3295                 }
3296
3297                 return $res;
3298         }
3299
3300         public function getLag() {
3301                 return 0;
3302         }
3303
3304         public function maxListLen() {
3305                 return 0;
3306         }
3307
3308         public function encodeBlob( $b ) {
3309                 return $b;
3310         }
3311
3312         public function decodeBlob( $b ) {
3313                 if ( $b instanceof Blob ) {
3314                         $b = $b->fetch();
3315                 }
3316                 return $b;
3317         }
3318
3319         public function setSessionOptions( array $options ) {
3320         }
3321
3322         public function sourceFile(
3323                 $filename,
3324                 callable $lineCallback = null,
3325                 callable $resultCallback = null,
3326                 $fname = false,
3327                 callable $inputCallback = null
3328         ) {
3329                 MediaWiki\suppressWarnings();
3330                 $fp = fopen( $filename, 'r' );
3331                 MediaWiki\restoreWarnings();
3332
3333                 if ( false === $fp ) {
3334                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
3335                 }
3336
3337                 if ( !$fname ) {
3338                         $fname = __METHOD__ . "( $filename )";
3339                 }
3340
3341                 try {
3342                         $error = $this->sourceStream(
3343                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3344                 } catch ( Exception $e ) {
3345                         fclose( $fp );
3346                         throw $e;
3347                 }
3348
3349                 fclose( $fp );
3350
3351                 return $error;
3352         }
3353
3354         public function setSchemaVars( $vars ) {
3355                 $this->mSchemaVars = $vars;
3356         }
3357
3358         public function sourceStream(
3359                 $fp,
3360                 callable $lineCallback = null,
3361                 callable $resultCallback = null,
3362                 $fname = __METHOD__,
3363                 callable $inputCallback = null
3364         ) {
3365                 $cmd = '';
3366
3367                 while ( !feof( $fp ) ) {
3368                         if ( $lineCallback ) {
3369                                 call_user_func( $lineCallback );
3370                         }
3371
3372                         $line = trim( fgets( $fp ) );
3373
3374                         if ( $line == '' ) {
3375                                 continue;
3376                         }
3377
3378                         if ( '-' == $line[0] && '-' == $line[1] ) {
3379                                 continue;
3380                         }
3381
3382                         if ( $cmd != '' ) {
3383                                 $cmd .= ' ';
3384                         }
3385
3386                         $done = $this->streamStatementEnd( $cmd, $line );
3387
3388                         $cmd .= "$line\n";
3389
3390                         if ( $done || feof( $fp ) ) {
3391                                 $cmd = $this->replaceVars( $cmd );
3392
3393                                 if ( !$inputCallback || call_user_func( $inputCallback, $cmd ) ) {
3394                                         $res = $this->query( $cmd, $fname );
3395
3396                                         if ( $resultCallback ) {
3397                                                 call_user_func( $resultCallback, $res, $this );
3398                                         }
3399
3400                                         if ( false === $res ) {
3401                                                 $err = $this->lastError();
3402
3403                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3404                                         }
3405                                 }
3406                                 $cmd = '';
3407                         }
3408                 }
3409
3410                 return true;
3411         }
3412
3413         /**
3414          * Called by sourceStream() to check if we've reached a statement end
3415          *
3416          * @param string &$sql SQL assembled so far
3417          * @param string &$newLine New line about to be added to $sql
3418          * @return bool Whether $newLine contains end of the statement
3419          */
3420         public function streamStatementEnd( &$sql, &$newLine ) {
3421                 if ( $this->delimiter ) {
3422                         $prev = $newLine;
3423                         $newLine = preg_replace(
3424                                 '/' . 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                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3531                         throw new DBUnexpectedError(
3532                                 $this,
3533                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
3534                         );
3535                 }
3536
3537                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
3538                         return null;
3539                 }
3540
3541                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
3542                         if ( $this->trxLevel() ) {
3543                                 // There is a good chance an exception was thrown, causing any early return
3544                                 // from the caller. Let any error handler get a chance to issue rollback().
3545                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
3546                                 $this->onTransactionResolution(
3547                                         function () use ( $lockKey, $fname ) {
3548                                                 $this->unlock( $lockKey, $fname );
3549                                         },
3550                                         $fname
3551                                 );
3552                         } else {
3553                                 $this->unlock( $lockKey, $fname );
3554                         }
3555                 } );
3556
3557                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3558
3559                 return $unlocker;
3560         }
3561
3562         public function namedLocksEnqueue() {
3563                 return false;
3564         }
3565
3566         public function tableLocksHaveTransactionScope() {
3567                 return true;
3568         }
3569
3570         final public function lockTables( array $read, array $write, $method ) {
3571                 if ( $this->writesOrCallbacksPending() ) {
3572                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
3573                 }
3574
3575                 if ( $this->tableLocksHaveTransactionScope() ) {
3576                         $this->startAtomic( $method );
3577                 }
3578
3579                 return $this->doLockTables( $read, $write, $method );
3580         }
3581
3582         /**
3583          * Helper function for lockTables() that handles the actual table locking
3584          *
3585          * @param array $read Array of tables to lock for read access
3586          * @param array $write Array of tables to lock for write access
3587          * @param string $method Name of caller
3588          * @return true
3589          */
3590         protected function doLockTables( array $read, array $write, $method ) {
3591                 return true;
3592         }
3593
3594         final public function unlockTables( $method ) {
3595                 if ( $this->tableLocksHaveTransactionScope() ) {
3596                         $this->endAtomic( $method );
3597
3598                         return true; // locks released on COMMIT/ROLLBACK
3599                 }
3600
3601                 return $this->doUnlockTables( $method );
3602         }
3603
3604         /**
3605          * Helper function for unlockTables() that handles the actual table unlocking
3606          *
3607          * @param string $method Name of caller
3608          * @return true
3609          */
3610         protected function doUnlockTables( $method ) {
3611                 return true;
3612         }
3613
3614         /**
3615          * Delete a table
3616          * @param string $tableName
3617          * @param string $fName
3618          * @return bool|ResultWrapper
3619          * @since 1.18
3620          */
3621         public function dropTable( $tableName, $fName = __METHOD__ ) {
3622                 if ( !$this->tableExists( $tableName, $fName ) ) {
3623                         return false;
3624                 }
3625                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
3626
3627                 return $this->query( $sql, $fName );
3628         }
3629
3630         public function getInfinity() {
3631                 return 'infinity';
3632         }
3633
3634         public function encodeExpiry( $expiry ) {
3635                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3636                         ? $this->getInfinity()
3637                         : $this->timestamp( $expiry );
3638         }
3639
3640         public function decodeExpiry( $expiry, $format = TS_MW ) {
3641                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
3642                         return 'infinity';
3643                 }
3644
3645                 return ConvertibleTimestamp::convert( $format, $expiry );
3646         }
3647
3648         public function setBigSelects( $value = true ) {
3649                 // no-op
3650         }
3651
3652         public function isReadOnly() {
3653                 return ( $this->getReadOnlyReason() !== false );
3654         }
3655
3656         /**
3657          * @return string|bool Reason this DB is read-only or false if it is not
3658          */
3659         protected function getReadOnlyReason() {
3660                 $reason = $this->getLBInfo( 'readOnlyReason' );
3661
3662                 return is_string( $reason ) ? $reason : false;
3663         }
3664
3665         public function setTableAliases( array $aliases ) {
3666                 $this->tableAliases = $aliases;
3667         }
3668
3669         /**
3670          * @return bool Whether a DB user is required to access the DB
3671          * @since 1.28
3672          */
3673         protected function requiresDatabaseUser() {
3674                 return true;
3675         }
3676
3677         /**
3678          * Get the underlying binding handle, mConn
3679          *
3680          * Makes sure that mConn is set (disconnects and ping() failure can unset it).
3681          * This catches broken callers than catch and ignore disconnection exceptions.
3682          * Unlike checking isOpen(), this is safe to call inside of open().
3683          *
3684          * @return resource|object
3685          * @throws DBUnexpectedError
3686          * @since 1.26
3687          */
3688         protected function getBindingHandle() {
3689                 if ( !$this->mConn ) {
3690                         throw new DBUnexpectedError(
3691                                 $this,
3692                                 'DB connection was already closed or the connection dropped.'
3693                         );
3694                 }
3695
3696                 return $this->mConn;
3697         }
3698
3699         /**
3700          * @since 1.19
3701          * @return string
3702          */
3703         public function __toString() {
3704                 return (string)$this->mConn;
3705         }
3706
3707         /**
3708          * Make sure that copies do not share the same client binding handle
3709          * @throws DBConnectionError
3710          */
3711         public function __clone() {
3712                 $this->connLogger->warning(
3713                         "Cloning " . static::class . " is not recomended; forking connection:\n" .
3714                         ( new RuntimeException() )->getTraceAsString()
3715                 );
3716
3717                 if ( $this->isOpen() ) {
3718                         // Open a new connection resource without messing with the old one
3719                         $this->mOpened = false;
3720                         $this->mConn = false;
3721                         $this->mTrxEndCallbacks = []; // don't copy
3722                         $this->handleSessionLoss(); // no trx or locks anymore
3723                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3724                         $this->lastPing = microtime( true );
3725                 }
3726         }
3727
3728         /**
3729          * Called by serialize. Throw an exception when DB connection is serialized.
3730          * This causes problems on some database engines because the connection is
3731          * not restored on unserialize.
3732          */
3733         public function __sleep() {
3734                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
3735                         'the connection is not restored on wakeup.' );
3736         }
3737
3738         /**
3739          * Run a few simple sanity checks and close dangling connections
3740          */
3741         public function __destruct() {
3742                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
3743                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
3744                 }
3745
3746                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
3747                 if ( $danglingWriters ) {
3748                         $fnames = implode( ', ', $danglingWriters );
3749                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
3750                 }
3751
3752                 if ( $this->mConn ) {
3753                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
3754                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
3755                         \MediaWiki\suppressWarnings();
3756                         $this->closeConnection();
3757                         \MediaWiki\restoreWarnings();
3758                         $this->mConn = false;
3759                         $this->mOpened = false;
3760                 }
3761         }
3762 }
3763
3764 class_alias( Database::class, 'DatabaseBase' ); // b/c for old name
3765 class_alias( Database::class, 'Database' ); // b/c global alias