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                                 $msg = __METHOD__ . ": lost connection to {$this->getServer()}; reconnected";
 949                                 $this->connLogger->warning( $msg );
 950                                 $this->queryLogger->warning(
 951                                         "$msg:\n" . ( new RuntimeException() )->getTraceAsString() );
 952
 953                                 if ( !$recoverable ) {
 954                                         # Callers may catch the exception and continue to use the DB
 955                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname );
 956                                 } else {
 957                                         # Should be safe to silently retry the query
 958                                         $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
 959                                 }
 960                         } else {
 961                                 $msg = __METHOD__ . ": lost connection to {$this->getServer()} permanently";
 962                                 $this->connLogger->error( $msg );
 963                         }
 964                 }
 965
 966                 if ( false === $ret ) {
 967                         # Deadlocks cause the entire transaction to abort, not just the statement.
 968                         # https://dev.mysql.com/doc/refman/5.7/en/innodb-error-handling.html
 969                         # https://www.postgresql.org/docs/9.1/static/explicit-locking.html
 970                         if ( $this->wasDeadlock() ) {
 971                                 if ( $this->explicitTrxActive() || $priorWritesPending ) {
 972                                         $tempIgnore = false; // not recoverable
 973                                 }
 974                                 # Update state tracking to reflect transaction loss
 975                                 $this->handleSessionLoss();
 976                         }
 977
 978                         $this->reportQueryError(
 979                                 $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 980                 }
 981
 982                 $res = $this->resultObject( $ret );
 983
 984                 return $res;
 985         }
 986
 987         /**
 988          * Helper method for query() that handles profiling and logging and sends
 989          * the query to doQuery()
 990          *
 991          * @param string $sql Original SQL query
 992          * @param string $commentedSql SQL query with debugging/trace comment
 993          * @param bool $isWrite Whether the query is a (non-temporary) write operation
 994          * @param string $fname Name of the calling function
 995          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
 996          *     object for a successful read query, or false on failure
 997          */
 998         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
 999                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1000                 # generalizeSQL() will probably cut down the query to reasonable
1001                 # logging size most of the time. The substr is really just a sanity check.
1002                 if ( $isMaster ) {
1003                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1004                 } else {
1005                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1006                 }
1007
1008                 # Include query transaction state
1009                 $queryProf .= $this->mTrxShortId ? " [TRX#{$this->mTrxShortId}]" : "";
1010
1011                 $startTime = microtime( true );
1012                 if ( $this->profiler ) {
1013                         call_user_func( [ $this->profiler, 'profileIn' ], $queryProf );
1014                 }
1015                 $ret = $this->doQuery( $commentedSql );
1016                 if ( $this->profiler ) {
1017                         call_user_func( [ $this->profiler, 'profileOut' ], $queryProf );
1018                 }
1019                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1020
1021                 unset( $queryProfSection ); // profile out (if set)
1022
1023                 if ( $ret !== false ) {
1024                         $this->lastPing = $startTime;
1025                         if ( $isWrite && $this->mTrxLevel ) {
1026                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1027                                 $this->mTrxWriteCallers[] = $fname;
1028                         }
1029                 }
1030
1031                 if ( $sql === self::PING_QUERY ) {
1032                         $this->mRTTEstimate = $queryRuntime;
1033                 }
1034
1035                 $this->trxProfiler->recordQueryCompletion(
1036                         $queryProf, $startTime, $isWrite, $this->affectedRows()
1037                 );
1038                 $this->queryLogger->debug( $sql, [
1039                         'method' => $fname,
1040                         'master' => $isMaster,
1041                         'runtime' => $queryRuntime,
1042                 ] );
1043
1044                 return $ret;
1045         }
1046
1047         /**
1048          * Update the estimated run-time of a query, not counting large row lock times
1049          *
1050          * LoadBalancer can be set to rollback transactions that will create huge replication
1051          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1052          * queries, like inserting a row can take a long time due to row locking. This method
1053          * uses some simple heuristics to discount those cases.
1054          *
1055          * @param string $sql A SQL write query
1056          * @param float $runtime Total runtime, including RTT
1057          * @param int $affected Affected row count
1058          */
1059         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1060                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1061                 $indicativeOfReplicaRuntime = true;
1062                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1063                         $verb = $this->getQueryVerb( $sql );
1064                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1065                         if ( $verb === 'INSERT' ) {
1066                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1067                         } elseif ( $verb === 'REPLACE' ) {
1068                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1069                         }
1070                 }
1071
1072                 $this->mTrxWriteDuration += $runtime;
1073                 $this->mTrxWriteQueryCount += 1;
1074                 $this->mTrxWriteAffectedRows += $affected;
1075                 if ( $indicativeOfReplicaRuntime ) {
1076                         $this->mTrxWriteAdjDuration += $runtime;
1077                         $this->mTrxWriteAdjQueryCount += 1;
1078                 }
1079         }
1080
1081         /**
1082          * Determine whether or not it is safe to retry queries after a database
1083          * connection is lost
1084          *
1085          * @param string $sql SQL query
1086          * @param bool $priorWritesPending Whether there is a transaction open with
1087          *     possible write queries or transaction pre-commit/idle callbacks
1088          *     waiting on it to finish.
1089          * @return bool True if it is safe to retry the query, false otherwise
1090          */
1091         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1092                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1093                 # Dropped connections also mean that named locks are automatically released.
1094                 # Only allow error suppression in autocommit mode or when the lost transaction
1095                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1096                 if ( $this->mNamedLocksHeld ) {
1097                         return false; // possible critical section violation
1098                 } elseif ( $sql === 'COMMIT' ) {
1099                         return !$priorWritesPending; // nothing written anyway? (T127428)
1100                 } elseif ( $sql === 'ROLLBACK' ) {
1101                         return true; // transaction lost...which is also what was requested :)
1102                 } elseif ( $this->explicitTrxActive() ) {
1103                         return false; // don't drop atomocity
1104                 } elseif ( $priorWritesPending ) {
1105                         return false; // prior writes lost from implicit transaction
1106                 }
1107
1108                 return true;
1109         }
1110
1111         /**
1112          * Clean things up after transaction loss due to disconnection
1113          *
1114          * @return null|Exception
1115          */
1116         private function handleSessionLoss() {
1117                 $this->mTrxLevel = 0;
1118                 $this->mTrxIdleCallbacks = []; // T67263
1119                 $this->mTrxPreCommitCallbacks = []; // T67263
1120                 $this->mSessionTempTables = [];
1121                 $this->mNamedLocksHeld = [];
1122                 try {
1123                         // Handle callbacks in mTrxEndCallbacks
1124                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1125                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1126                         return null;
1127                 } catch ( Exception $e ) {
1128                         // Already logged; move on...
1129                         return $e;
1130                 }
1131         }
1132
1133         /**
1134          * Checks whether the cause of the error is detected to be a timeout.
1135          *
1136          * It returns false by default, and not all engines support detecting this yet.
1137          * If this returns false, it will be treated as a generic query error.
1138          *
1139          * @param string $error Error text
1140          * @param int $errno Error number
1141          * @return bool
1142          */
1143         protected function wasQueryTimeout( $error, $errno ) {
1144                 return false;
1145         }
1146
1147         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1148                 if ( $this->ignoreErrors() || $tempIgnore ) {
1149                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1150                 } else {
1151                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1152                         $this->queryLogger->error(
1153                                 "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1154                                 $this->getLogContext( [
1155                                         'method' => __METHOD__,
1156                                         'errno' => $errno,
1157                                         'error' => $error,
1158                                         'sql1line' => $sql1line,
1159                                         'fname' => $fname,
1160                                 ] )
1161                         );
1162                         $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1163                         $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1164                         if ( $wasQueryTimeout ) {
1165                                 throw new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1166                         } else {
1167                                 throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1168                         }
1169                 }
1170         }
1171
1172         public function freeResult( $res ) {
1173         }
1174
1175         public function selectField(
1176                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1177         ) {
1178                 if ( $var === '*' ) { // sanity
1179                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1180                 }
1181
1182                 if ( !is_array( $options ) ) {
1183                         $options = [ $options ];
1184                 }
1185
1186                 $options['LIMIT'] = 1;
1187
1188                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1189                 if ( $res === false || !$this->numRows( $res ) ) {
1190                         return false;
1191                 }
1192
1193                 $row = $this->fetchRow( $res );
1194
1195                 if ( $row !== false ) {
1196                         return reset( $row );
1197                 } else {
1198                         return false;
1199                 }
1200         }
1201
1202         public function selectFieldValues(
1203                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1204         ) {
1205                 if ( $var === '*' ) { // sanity
1206                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1207                 } elseif ( !is_string( $var ) ) { // sanity
1208                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1209                 }
1210
1211                 if ( !is_array( $options ) ) {
1212                         $options = [ $options ];
1213                 }
1214
1215                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1216                 if ( $res === false ) {
1217                         return false;
1218                 }
1219
1220                 $values = [];
1221                 foreach ( $res as $row ) {
1222                         $values[] = $row->$var;
1223                 }
1224
1225                 return $values;
1226         }
1227
1228         /**
1229          * Returns an optional USE INDEX clause to go after the table, and a
1230          * string to go at the end of the query.
1231          *
1232          * @param array $options Associative array of options to be turned into
1233          *   an SQL query, valid keys are listed in the function.
1234          * @return array
1235          * @see Database::select()
1236          */
1237         protected function makeSelectOptions( $options ) {
1238                 $preLimitTail = $postLimitTail = '';
1239                 $startOpts = '';
1240
1241                 $noKeyOptions = [];
1242
1243                 foreach ( $options as $key => $option ) {
1244                         if ( is_numeric( $key ) ) {
1245                                 $noKeyOptions[$option] = true;
1246                         }
1247                 }
1248
1249                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1250
1251                 $preLimitTail .= $this->makeOrderBy( $options );
1252
1253                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1254                         $postLimitTail .= ' FOR UPDATE';
1255                 }
1256
1257                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1258                         $postLimitTail .= ' LOCK IN SHARE MODE';
1259                 }
1260
1261                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1262                         $startOpts .= 'DISTINCT';
1263                 }
1264
1265                 # Various MySQL extensions
1266                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1267                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1268                 }
1269
1270                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1271                         $startOpts .= ' HIGH_PRIORITY';
1272                 }
1273
1274                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1275                         $startOpts .= ' SQL_BIG_RESULT';
1276                 }
1277
1278                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1279                         $startOpts .= ' SQL_BUFFER_RESULT';
1280                 }
1281
1282                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1283                         $startOpts .= ' SQL_SMALL_RESULT';
1284                 }
1285
1286                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1287                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1288                 }
1289
1290                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1291                         $startOpts .= ' SQL_CACHE';
1292                 }
1293
1294                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1295                         $startOpts .= ' SQL_NO_CACHE';
1296                 }
1297
1298                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1299                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1300                 } else {
1301                         $useIndex = '';
1302                 }
1303                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1304                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1305                 } else {
1306                         $ignoreIndex = '';
1307                 }
1308
1309                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1310         }
1311
1312         /**
1313          * Returns an optional GROUP BY with an optional HAVING
1314          *
1315          * @param array $options Associative array of options
1316          * @return string
1317          * @see Database::select()
1318          * @since 1.21
1319          */
1320         protected function makeGroupByWithHaving( $options ) {
1321                 $sql = '';
1322                 if ( isset( $options['GROUP BY'] ) ) {
1323                         $gb = is_array( $options['GROUP BY'] )
1324                                 ? implode( ',', $options['GROUP BY'] )
1325                                 : $options['GROUP BY'];
1326                         $sql .= ' GROUP BY ' . $gb;
1327                 }
1328                 if ( isset( $options['HAVING'] ) ) {
1329                         $having = is_array( $options['HAVING'] )
1330                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1331                                 : $options['HAVING'];
1332                         $sql .= ' HAVING ' . $having;
1333                 }
1334
1335                 return $sql;
1336         }
1337
1338         /**
1339          * Returns an optional ORDER BY
1340          *
1341          * @param array $options Associative array of options
1342          * @return string
1343          * @see Database::select()
1344          * @since 1.21
1345          */
1346         protected function makeOrderBy( $options ) {
1347                 if ( isset( $options['ORDER BY'] ) ) {
1348                         $ob = is_array( $options['ORDER BY'] )
1349                                 ? implode( ',', $options['ORDER BY'] )
1350                                 : $options['ORDER BY'];
1351
1352                         return ' ORDER BY ' . $ob;
1353                 }
1354
1355                 return '';
1356         }
1357
1358         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1359                 $options = [], $join_conds = [] ) {
1360                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1361
1362                 return $this->query( $sql, $fname );
1363         }
1364
1365         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1366                 $options = [], $join_conds = []
1367         ) {
1368                 if ( is_array( $vars ) ) {
1369                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1370                 }
1371
1372                 $options = (array)$options;
1373                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1374                         ? $options['USE INDEX']
1375                         : [];
1376                 $ignoreIndexes = (
1377                         isset( $options['IGNORE INDEX'] ) &&
1378                         is_array( $options['IGNORE INDEX'] )
1379                 )
1380                         ? $options['IGNORE INDEX']
1381                         : [];
1382
1383                 if ( is_array( $table ) ) {
1384                         $from = ' FROM ' .
1385                                 $this->tableNamesWithIndexClauseOrJOIN(
1386                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1387                 } elseif ( $table != '' ) {
1388                         if ( $table[0] == ' ' ) {
1389                                 $from = ' FROM ' . $table;
1390                         } else {
1391                                 $from = ' FROM ' .
1392                                         $this->tableNamesWithIndexClauseOrJOIN(
1393                                                 [ $table ], $useIndexes, $ignoreIndexes, [] );
1394                         }
1395                 } else {
1396                         $from = '';
1397                 }
1398
1399                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1400                         $this->makeSelectOptions( $options );
1401
1402                 if ( !empty( $conds ) ) {
1403                         if ( is_array( $conds ) ) {
1404                                 $conds = $this->makeList( $conds, self::LIST_AND );
1405                         }
1406                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex " .
1407                                 "WHERE $conds $preLimitTail";
1408                 } else {
1409                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex $preLimitTail";
1410                 }
1411
1412                 if ( isset( $options['LIMIT'] ) ) {
1413                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1414                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1415                 }
1416                 $sql = "$sql $postLimitTail";
1417
1418                 if ( isset( $options['EXPLAIN'] ) ) {
1419                         $sql = 'EXPLAIN ' . $sql;
1420                 }
1421
1422                 return $sql;
1423         }
1424
1425         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1426                 $options = [], $join_conds = []
1427         ) {
1428                 $options = (array)$options;
1429                 $options['LIMIT'] = 1;
1430                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1431
1432                 if ( $res === false ) {
1433                         return false;
1434                 }
1435
1436                 if ( !$this->numRows( $res ) ) {
1437                         return false;
1438                 }
1439
1440                 $obj = $this->fetchObject( $res );
1441
1442                 return $obj;
1443         }
1444
1445         public function estimateRowCount(
1446                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
1447         ) {
1448                 $rows = 0;
1449                 $res = $this->select( $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options );
1450
1451                 if ( $res ) {
1452                         $row = $this->fetchRow( $res );
1453                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1454                 }
1455
1456                 return $rows;
1457         }
1458
1459         public function selectRowCount(
1460                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1461         ) {
1462                 $rows = 0;
1463                 $sql = $this->selectSQLText( $tables, '1', $conds, $fname, $options, $join_conds );
1464                 // The identifier quotes is primarily for MSSQL.
1465                 $rowCountCol = $this->addIdentifierQuotes( "rowcount" );
1466                 $tableName = $this->addIdentifierQuotes( "tmp_count" );
1467                 $res = $this->query( "SELECT COUNT(*) AS $rowCountCol FROM ($sql) $tableName", $fname );
1468
1469                 if ( $res ) {
1470                         $row = $this->fetchRow( $res );
1471                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1472                 }
1473
1474                 return $rows;
1475         }
1476
1477         /**
1478          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1479          * It's only slightly flawed. Don't use for anything important.
1480          *
1481          * @param string $sql A SQL Query
1482          *
1483          * @return string
1484          */
1485         protected static function generalizeSQL( $sql ) {
1486                 # This does the same as the regexp below would do, but in such a way
1487                 # as to avoid crashing php on some large strings.
1488                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1489
1490                 $sql = str_replace( "\\\\", '', $sql );
1491                 $sql = str_replace( "\\'", '', $sql );
1492                 $sql = str_replace( "\\\"", '', $sql );
1493                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1494                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1495
1496                 # All newlines, tabs, etc replaced by single space
1497                 $sql = preg_replace( '/\s+/', ' ', $sql );
1498
1499                 # All numbers => N,
1500                 # except the ones surrounded by characters, e.g. l10n
1501                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1502                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1503
1504                 return $sql;
1505         }
1506
1507         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1508                 $info = $this->fieldInfo( $table, $field );
1509
1510                 return (bool)$info;
1511         }
1512
1513         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1514                 if ( !$this->tableExists( $table ) ) {
1515                         return null;
1516                 }
1517
1518                 $info = $this->indexInfo( $table, $index, $fname );
1519                 if ( is_null( $info ) ) {
1520                         return null;
1521                 } else {
1522                         return $info !== false;
1523                 }
1524         }
1525
1526         public function tableExists( $table, $fname = __METHOD__ ) {
1527                 $tableRaw = $this->tableName( $table, 'raw' );
1528                 if ( isset( $this->mSessionTempTables[$tableRaw] ) ) {
1529                         return true; // already known to exist
1530                 }
1531
1532                 $table = $this->tableName( $table );
1533                 $ignoreErrors = true;
1534                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname, $ignoreErrors );
1535
1536                 return (bool)$res;
1537         }
1538
1539         public function indexUnique( $table, $index ) {
1540                 $indexInfo = $this->indexInfo( $table, $index );
1541
1542                 if ( !$indexInfo ) {
1543                         return null;
1544                 }
1545
1546                 return !$indexInfo[0]->Non_unique;
1547         }
1548
1549         /**
1550          * Helper for Database::insert().
1551          *
1552          * @param array $options
1553          * @return string
1554          */
1555         protected function makeInsertOptions( $options ) {
1556                 return implode( ' ', $options );
1557         }
1558
1559         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1560                 # No rows to insert, easy just return now
1561                 if ( !count( $a ) ) {
1562                         return true;
1563                 }
1564
1565                 $table = $this->tableName( $table );
1566
1567                 if ( !is_array( $options ) ) {
1568                         $options = [ $options ];
1569                 }
1570
1571                 $fh = null;
1572                 if ( isset( $options['fileHandle'] ) ) {
1573                         $fh = $options['fileHandle'];
1574                 }
1575                 $options = $this->makeInsertOptions( $options );
1576
1577                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1578                         $multi = true;
1579                         $keys = array_keys( $a[0] );
1580                 } else {
1581                         $multi = false;
1582                         $keys = array_keys( $a );
1583                 }
1584
1585                 $sql = 'INSERT ' . $options .
1586                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1587
1588                 if ( $multi ) {
1589                         $first = true;
1590                         foreach ( $a as $row ) {
1591                                 if ( $first ) {
1592                                         $first = false;
1593                                 } else {
1594                                         $sql .= ',';
1595                                 }
1596                                 $sql .= '(' . $this->makeList( $row ) . ')';
1597                         }
1598                 } else {
1599                         $sql .= '(' . $this->makeList( $a ) . ')';
1600                 }
1601
1602                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1603                         return false;
1604                 } elseif ( $fh !== null ) {
1605                         return true;
1606                 }
1607
1608                 return (bool)$this->query( $sql, $fname );
1609         }
1610
1611         /**
1612          * Make UPDATE options array for Database::makeUpdateOptions
1613          *
1614          * @param array $options
1615          * @return array
1616          */
1617         protected function makeUpdateOptionsArray( $options ) {
1618                 if ( !is_array( $options ) ) {
1619                         $options = [ $options ];
1620                 }
1621
1622                 $opts = [];
1623
1624                 if ( in_array( 'IGNORE', $options ) ) {
1625                         $opts[] = 'IGNORE';
1626                 }
1627
1628                 return $opts;
1629         }
1630
1631         /**
1632          * Make UPDATE options for the Database::update function
1633          *
1634          * @param array $options The options passed to Database::update
1635          * @return string
1636          */
1637         protected function makeUpdateOptions( $options ) {
1638                 $opts = $this->makeUpdateOptionsArray( $options );
1639
1640                 return implode( ' ', $opts );
1641         }
1642
1643         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1644                 $table = $this->tableName( $table );
1645                 $opts = $this->makeUpdateOptions( $options );
1646                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
1647
1648                 if ( $conds !== [] && $conds !== '*' ) {
1649                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
1650                 }
1651
1652                 return (bool)$this->query( $sql, $fname );
1653         }
1654
1655         public function makeList( $a, $mode = self::LIST_COMMA ) {
1656                 if ( !is_array( $a ) ) {
1657                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1658                 }
1659
1660                 $first = true;
1661                 $list = '';
1662
1663                 foreach ( $a as $field => $value ) {
1664                         if ( !$first ) {
1665                                 if ( $mode == self::LIST_AND ) {
1666                                         $list .= ' AND ';
1667                                 } elseif ( $mode == self::LIST_OR ) {
1668                                         $list .= ' OR ';
1669                                 } else {
1670                                         $list .= ',';
1671                                 }
1672                         } else {
1673                                 $first = false;
1674                         }
1675
1676                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
1677                                 $list .= "($value)";
1678                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
1679                                 $list .= "$value";
1680                         } elseif (
1681                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
1682                         ) {
1683                                 // Remove null from array to be handled separately if found
1684                                 $includeNull = false;
1685                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
1686                                         $includeNull = true;
1687                                         unset( $value[$nullKey] );
1688                                 }
1689                                 if ( count( $value ) == 0 && !$includeNull ) {
1690                                         throw new InvalidArgumentException(
1691                                                 __METHOD__ . ": empty input for field $field" );
1692                                 } elseif ( count( $value ) == 0 ) {
1693                                         // only check if $field is null
1694                                         $list .= "$field IS NULL";
1695                                 } else {
1696                                         // IN clause contains at least one valid element
1697                                         if ( $includeNull ) {
1698                                                 // Group subconditions to ensure correct precedence
1699                                                 $list .= '(';
1700                                         }
1701                                         if ( count( $value ) == 1 ) {
1702                                                 // Special-case single values, as IN isn't terribly efficient
1703                                                 // Don't necessarily assume the single key is 0; we don't
1704                                                 // enforce linear numeric ordering on other arrays here.
1705                                                 $value = array_values( $value )[0];
1706                                                 $list .= $field . " = " . $this->addQuotes( $value );
1707                                         } else {
1708                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1709                                         }
1710                                         // if null present in array, append IS NULL
1711                                         if ( $includeNull ) {
1712                                                 $list .= " OR $field IS NULL)";
1713                                         }
1714                                 }
1715                         } elseif ( $value === null ) {
1716                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
1717                                         $list .= "$field IS ";
1718                                 } elseif ( $mode == self::LIST_SET ) {
1719                                         $list .= "$field = ";
1720                                 }
1721                                 $list .= 'NULL';
1722                         } else {
1723                                 if (
1724                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
1725                                 ) {
1726                                         $list .= "$field = ";
1727                                 }
1728                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
1729                         }
1730                 }
1731
1732                 return $list;
1733         }
1734
1735         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1736                 $conds = [];
1737
1738                 foreach ( $data as $base => $sub ) {
1739                         if ( count( $sub ) ) {
1740                                 $conds[] = $this->makeList(
1741                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
1742                                         self::LIST_AND );
1743                         }
1744                 }
1745
1746                 if ( $conds ) {
1747                         return $this->makeList( $conds, self::LIST_OR );
1748                 } else {
1749                         // Nothing to search for...
1750                         return false;
1751                 }
1752         }
1753
1754         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1755                 return $valuename;
1756         }
1757
1758         public function bitNot( $field ) {
1759                 return "(~$field)";
1760         }
1761
1762         public function bitAnd( $fieldLeft, $fieldRight ) {
1763                 return "($fieldLeft & $fieldRight)";
1764         }
1765
1766         public function bitOr( $fieldLeft, $fieldRight ) {
1767                 return "($fieldLeft | $fieldRight)";
1768         }
1769
1770         public function buildConcat( $stringList ) {
1771                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1772         }
1773
1774         public function buildGroupConcatField(
1775                 $delim, $table, $field, $conds = '', $join_conds = []
1776         ) {
1777                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
1778
1779                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
1780         }
1781
1782         public function buildStringCast( $field ) {
1783                 return $field;
1784         }
1785
1786         public function databasesAreIndependent() {
1787                 return false;
1788         }
1789
1790         public function selectDB( $db ) {
1791                 # Stub. Shouldn't cause serious problems if it's not overridden, but
1792                 # if your database engine supports a concept similar to MySQL's
1793                 # databases you may as well.
1794                 $this->mDBname = $db;
1795
1796                 return true;
1797         }
1798
1799         public function getDBname() {
1800                 return $this->mDBname;
1801         }
1802
1803         public function getServer() {
1804                 return $this->mServer;
1805         }
1806
1807         public function tableName( $name, $format = 'quoted' ) {
1808                 # Skip the entire process when we have a string quoted on both ends.
1809                 # Note that we check the end so that we will still quote any use of
1810                 # use of `database`.table. But won't break things if someone wants
1811                 # to query a database table with a dot in the name.
1812                 if ( $this->isQuotedIdentifier( $name ) ) {
1813                         return $name;
1814                 }
1815
1816                 # Lets test for any bits of text that should never show up in a table
1817                 # name. Basically anything like JOIN or ON which are actually part of
1818                 # SQL queries, but may end up inside of the table value to combine
1819                 # sql. Such as how the API is doing.
1820                 # Note that we use a whitespace test rather than a \b test to avoid
1821                 # any remote case where a word like on may be inside of a table name
1822                 # surrounded by symbols which may be considered word breaks.
1823                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1824                         return $name;
1825                 }
1826
1827                 # Split database and table into proper variables.
1828                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
1829
1830                 # Quote $table and apply the prefix if not quoted.
1831                 # $tableName might be empty if this is called from Database::replaceVars()
1832                 $tableName = "{$prefix}{$table}";
1833                 if ( $format === 'quoted'
1834                         && !$this->isQuotedIdentifier( $tableName )
1835                         && $tableName !== ''
1836                 ) {
1837                         $tableName = $this->addIdentifierQuotes( $tableName );
1838                 }
1839
1840                 # Quote $schema and $database and merge them with the table name if needed
1841                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
1842                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
1843
1844                 return $tableName;
1845         }
1846
1847         /**
1848          * Get the table components needed for a query given the currently selected database
1849          *
1850          * @param string $name Table name in the form of db.schema.table, db.table, or table
1851          * @return array (DB name or "" for default, schema name, table prefix, table name)
1852          */
1853         protected function qualifiedTableComponents( $name ) {
1854                 # We reverse the explode so that database.table and table both output the correct table.
1855                 $dbDetails = explode( '.', $name, 3 );
1856                 if ( count( $dbDetails ) == 3 ) {
1857                         list( $database, $schema, $table ) = $dbDetails;
1858                         # We don't want any prefix added in this case
1859                         $prefix = '';
1860                 } elseif ( count( $dbDetails ) == 2 ) {
1861                         list( $database, $table ) = $dbDetails;
1862                         # We don't want any prefix added in this case
1863                         $prefix = '';
1864                         # In dbs that support it, $database may actually be the schema
1865                         # but that doesn't affect any of the functionality here
1866                         $schema = '';
1867                 } else {
1868                         list( $table ) = $dbDetails;
1869                         if ( isset( $this->tableAliases[$table] ) ) {
1870                                 $database = $this->tableAliases[$table]['dbname'];
1871                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
1872                                         ? $this->tableAliases[$table]['schema']
1873                                         : $this->mSchema;
1874                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
1875                                         ? $this->tableAliases[$table]['prefix']
1876                                         : $this->mTablePrefix;
1877                         } else {
1878                                 $database = '';
1879                                 $schema = $this->mSchema; # Default schema
1880                                 $prefix = $this->mTablePrefix; # Default prefix
1881                         }
1882                 }
1883
1884                 return [ $database, $schema, $prefix, $table ];
1885         }
1886
1887         /**
1888          * @param string|null $namespace Database or schema
1889          * @param string $relation Name of table, view, sequence, etc...
1890          * @param string $format One of (raw, quoted)
1891          * @return string Relation name with quoted and merged $namespace as needed
1892          */
1893         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
1894                 if ( strlen( $namespace ) ) {
1895                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
1896                                 $namespace = $this->addIdentifierQuotes( $namespace );
1897                         }
1898                         $relation = $namespace . '.' . $relation;
1899                 }
1900
1901                 return $relation;
1902         }
1903
1904         public function tableNames() {
1905                 $inArray = func_get_args();
1906                 $retVal = [];
1907
1908                 foreach ( $inArray as $name ) {
1909                         $retVal[$name] = $this->tableName( $name );
1910                 }
1911
1912                 return $retVal;
1913         }
1914
1915         public function tableNamesN() {
1916                 $inArray = func_get_args();
1917                 $retVal = [];
1918
1919                 foreach ( $inArray as $name ) {
1920                         $retVal[] = $this->tableName( $name );
1921                 }
1922
1923                 return $retVal;
1924         }
1925
1926         /**
1927          * Get an aliased table name
1928          * e.g. tableName AS newTableName
1929          *
1930          * @param string $name Table name, see tableName()
1931          * @param string|bool $alias Alias (optional)
1932          * @return string SQL name for aliased table. Will not alias a table to its own name
1933          */
1934         protected function tableNameWithAlias( $name, $alias = false ) {
1935                 if ( !$alias || $alias == $name ) {
1936                         return $this->tableName( $name );
1937                 } else {
1938                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
1939                 }
1940         }
1941
1942         /**
1943          * Gets an array of aliased table names
1944          *
1945          * @param array $tables [ [alias] => table ]
1946          * @return string[] See tableNameWithAlias()
1947          */
1948         protected function tableNamesWithAlias( $tables ) {
1949                 $retval = [];
1950                 foreach ( $tables as $alias => $table ) {
1951                         if ( is_numeric( $alias ) ) {
1952                                 $alias = $table;
1953                         }
1954                         $retval[] = $this->tableNameWithAlias( $table, $alias );
1955                 }
1956
1957                 return $retval;
1958         }
1959
1960         /**
1961          * Get an aliased field name
1962          * e.g. fieldName AS newFieldName
1963          *
1964          * @param string $name Field name
1965          * @param string|bool $alias Alias (optional)
1966          * @return string SQL name for aliased field. Will not alias a field to its own name
1967          */
1968         protected function fieldNameWithAlias( $name, $alias = false ) {
1969                 if ( !$alias || (string)$alias === (string)$name ) {
1970                         return $name;
1971                 } else {
1972                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
1973                 }
1974         }
1975
1976         /**
1977          * Gets an array of aliased field names
1978          *
1979          * @param array $fields [ [alias] => field ]
1980          * @return string[] See fieldNameWithAlias()
1981          */
1982         protected function fieldNamesWithAlias( $fields ) {
1983                 $retval = [];
1984                 foreach ( $fields as $alias => $field ) {
1985                         if ( is_numeric( $alias ) ) {
1986                                 $alias = $field;
1987                         }
1988                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
1989                 }
1990
1991                 return $retval;
1992         }
1993
1994         /**
1995          * Get the aliased table name clause for a FROM clause
1996          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
1997          *
1998          * @param array $tables ( [alias] => table )
1999          * @param array $use_index Same as for select()
2000          * @param array $ignore_index Same as for select()
2001          * @param array $join_conds Same as for select()
2002          * @return string
2003          */
2004         protected function tableNamesWithIndexClauseOrJOIN(
2005                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2006         ) {
2007                 $ret = [];
2008                 $retJOIN = [];
2009                 $use_index = (array)$use_index;
2010                 $ignore_index = (array)$ignore_index;
2011                 $join_conds = (array)$join_conds;
2012
2013                 foreach ( $tables as $alias => $table ) {
2014                         if ( !is_string( $alias ) ) {
2015                                 // No alias? Set it equal to the table name
2016                                 $alias = $table;
2017                         }
2018
2019                         if ( is_array( $table ) ) {
2020                                 // A parenthesized group
2021                                 $joinedTable = '('
2022                                         . $this->tableNamesWithIndexClauseOrJOIN( $table, $use_index, $ignore_index, $join_conds )
2023                                         . ')';
2024                         } else {
2025                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2026                         }
2027
2028                         // Is there a JOIN clause for this table?
2029                         if ( isset( $join_conds[$alias] ) ) {
2030                                 list( $joinType, $conds ) = $join_conds[$alias];
2031                                 $tableClause = $joinType;
2032                                 $tableClause .= ' ' . $joinedTable;
2033                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2034                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2035                                         if ( $use != '' ) {
2036                                                 $tableClause .= ' ' . $use;
2037                                         }
2038                                 }
2039                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2040                                         $ignore = $this->ignoreIndexClause(
2041                                                 implode( ',', (array)$ignore_index[$alias] ) );
2042                                         if ( $ignore != '' ) {
2043                                                 $tableClause .= ' ' . $ignore;
2044                                         }
2045                                 }
2046                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2047                                 if ( $on != '' ) {
2048                                         $tableClause .= ' ON (' . $on . ')';
2049                                 }
2050
2051                                 $retJOIN[] = $tableClause;
2052                         } elseif ( isset( $use_index[$alias] ) ) {
2053                                 // Is there an INDEX clause for this table?
2054                                 $tableClause = $joinedTable;
2055                                 $tableClause .= ' ' . $this->useIndexClause(
2056                                                 implode( ',', (array)$use_index[$alias] )
2057                                         );
2058
2059                                 $ret[] = $tableClause;
2060                         } elseif ( isset( $ignore_index[$alias] ) ) {
2061                                 // Is there an INDEX clause for this table?
2062                                 $tableClause = $joinedTable;
2063                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2064                                                 implode( ',', (array)$ignore_index[$alias] )
2065                                         );
2066
2067                                 $ret[] = $tableClause;
2068                         } else {
2069                                 $tableClause = $joinedTable;
2070
2071                                 $ret[] = $tableClause;
2072                         }
2073                 }
2074
2075                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2076                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2077                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2078
2079                 // Compile our final table clause
2080                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2081         }
2082
2083         /**
2084          * Allows for index remapping in queries where this is not consistent across DBMS
2085          *
2086          * @param string $index
2087          * @return string
2088          */
2089         protected function indexName( $index ) {
2090                 return $index;
2091         }
2092
2093         public function addQuotes( $s ) {
2094                 if ( $s instanceof Blob ) {
2095                         $s = $s->fetch();
2096                 }
2097                 if ( $s === null ) {
2098                         return 'NULL';
2099                 } elseif ( is_bool( $s ) ) {
2100                         return (int)$s;
2101                 } else {
2102                         # This will also quote numeric values. This should be harmless,
2103                         # and protects against weird problems that occur when they really
2104                         # _are_ strings such as article titles and string->number->string
2105                         # conversion is not 1:1.
2106                         return "'" . $this->strencode( $s ) . "'";
2107                 }
2108         }
2109
2110         /**
2111          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2112          * MySQL uses `backticks` while basically everything else uses double quotes.
2113          * Since MySQL is the odd one out here the double quotes are our generic
2114          * and we implement backticks in DatabaseMysqlBase.
2115          *
2116          * @param string $s
2117          * @return string
2118          */
2119         public function addIdentifierQuotes( $s ) {
2120                 return '"' . str_replace( '"', '""', $s ) . '"';
2121         }
2122
2123         /**
2124          * Returns if the given identifier looks quoted or not according to
2125          * the database convention for quoting identifiers .
2126          *
2127          * @note Do not use this to determine if untrusted input is safe.
2128          *   A malicious user can trick this function.
2129          * @param string $name
2130          * @return bool
2131          */
2132         public function isQuotedIdentifier( $name ) {
2133                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2134         }
2135
2136         /**
2137          * @param string $s
2138          * @param string $escapeChar
2139          * @return string
2140          */
2141         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2142                 return str_replace( [ $escapeChar, '%', '_' ],
2143                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2144                         $s );
2145         }
2146
2147         public function buildLike() {
2148                 $params = func_get_args();
2149
2150                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2151                         $params = $params[0];
2152                 }
2153
2154                 $s = '';
2155
2156                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2157                 // may escape backslashes, creating problems of double escaping. The `
2158                 // character has good cross-DBMS compatibility, avoiding special operators
2159                 // in MS SQL like ^ and %
2160                 $escapeChar = '`';
2161
2162                 foreach ( $params as $value ) {
2163                         if ( $value instanceof LikeMatch ) {
2164                                 $s .= $value->toString();
2165                         } else {
2166                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2167                         }
2168                 }
2169
2170                 return ' LIKE ' . $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2171         }
2172
2173         public function anyChar() {
2174                 return new LikeMatch( '_' );
2175         }
2176
2177         public function anyString() {
2178                 return new LikeMatch( '%' );
2179         }
2180
2181         public function nextSequenceValue( $seqName ) {
2182                 return null;
2183         }
2184
2185         /**
2186          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2187          * is only needed because a) MySQL must be as efficient as possible due to
2188          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2189          * which index to pick. Anyway, other databases might have different
2190          * indexes on a given table. So don't bother overriding this unless you're
2191          * MySQL.
2192          * @param string $index
2193          * @return string
2194          */
2195         public function useIndexClause( $index ) {
2196                 return '';
2197         }
2198
2199         /**
2200          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2201          * is only needed because a) MySQL must be as efficient as possible due to
2202          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2203          * which index to pick. Anyway, other databases might have different
2204          * indexes on a given table. So don't bother overriding this unless you're
2205          * MySQL.
2206          * @param string $index
2207          * @return string
2208          */
2209         public function ignoreIndexClause( $index ) {
2210                 return '';
2211         }
2212
2213         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2214                 $quotedTable = $this->tableName( $table );
2215
2216                 if ( count( $rows ) == 0 ) {
2217                         return;
2218                 }
2219
2220                 # Single row case
2221                 if ( !is_array( reset( $rows ) ) ) {
2222                         $rows = [ $rows ];
2223                 }
2224
2225                 // @FXIME: this is not atomic, but a trx would break affectedRows()
2226                 foreach ( $rows as $row ) {
2227                         # Delete rows which collide
2228                         if ( $uniqueIndexes ) {
2229                                 $sql = "DELETE FROM $quotedTable WHERE ";
2230                                 $first = true;
2231                                 foreach ( $uniqueIndexes as $index ) {
2232                                         if ( $first ) {
2233                                                 $first = false;
2234                                                 $sql .= '( ';
2235                                         } else {
2236                                                 $sql .= ' ) OR ( ';
2237                                         }
2238                                         if ( is_array( $index ) ) {
2239                                                 $first2 = true;
2240                                                 foreach ( $index as $col ) {
2241                                                         if ( $first2 ) {
2242                                                                 $first2 = false;
2243                                                         } else {
2244                                                                 $sql .= ' AND ';
2245                                                         }
2246                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2247                                                 }
2248                                         } else {
2249                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2250                                         }
2251                                 }
2252                                 $sql .= ' )';
2253                                 $this->query( $sql, $fname );
2254                         }
2255
2256                         # Now insert the row
2257                         $this->insert( $table, $row, $fname );
2258                 }
2259         }
2260
2261         /**
2262          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2263          * statement.
2264          *
2265          * @param string $table Table name
2266          * @param array|string $rows Row(s) to insert
2267          * @param string $fname Caller function name
2268          *
2269          * @return ResultWrapper
2270          */
2271         protected function nativeReplace( $table, $rows, $fname ) {
2272                 $table = $this->tableName( $table );
2273
2274                 # Single row case
2275                 if ( !is_array( reset( $rows ) ) ) {
2276                         $rows = [ $rows ];
2277                 }
2278
2279                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2280                 $first = true;
2281
2282                 foreach ( $rows as $row ) {
2283                         if ( $first ) {
2284                                 $first = false;
2285                         } else {
2286                                 $sql .= ',';
2287                         }
2288
2289                         $sql .= '(' . $this->makeList( $row ) . ')';
2290                 }
2291
2292                 return $this->query( $sql, $fname );
2293         }
2294
2295         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2296                 $fname = __METHOD__
2297         ) {
2298                 if ( !count( $rows ) ) {
2299                         return true; // nothing to do
2300                 }
2301
2302                 if ( !is_array( reset( $rows ) ) ) {
2303                         $rows = [ $rows ];
2304                 }
2305
2306                 if ( count( $uniqueIndexes ) ) {
2307                         $clauses = []; // list WHERE clauses that each identify a single row
2308                         foreach ( $rows as $row ) {
2309                                 foreach ( $uniqueIndexes as $index ) {
2310                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2311                                         $rowKey = []; // unique key to this row
2312                                         foreach ( $index as $column ) {
2313                                                 $rowKey[$column] = $row[$column];
2314                                         }
2315                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2316                                 }
2317                         }
2318                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2319                 } else {
2320                         $where = false;
2321                 }
2322
2323                 $useTrx = !$this->mTrxLevel;
2324                 if ( $useTrx ) {
2325                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2326                 }
2327                 try {
2328                         # Update any existing conflicting row(s)
2329                         if ( $where !== false ) {
2330                                 $ok = $this->update( $table, $set, $where, $fname );
2331                         } else {
2332                                 $ok = true;
2333                         }
2334                         # Now insert any non-conflicting row(s)
2335                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2336                 } catch ( Exception $e ) {
2337                         if ( $useTrx ) {
2338                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
2339                         }
2340                         throw $e;
2341                 }
2342                 if ( $useTrx ) {
2343                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2344                 }
2345
2346                 return $ok;
2347         }
2348
2349         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2350                 $fname = __METHOD__
2351         ) {
2352                 if ( !$conds ) {
2353                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2354                 }
2355
2356                 $delTable = $this->tableName( $delTable );
2357                 $joinTable = $this->tableName( $joinTable );
2358                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2359                 if ( $conds != '*' ) {
2360                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2361                 }
2362                 $sql .= ')';
2363
2364                 $this->query( $sql, $fname );
2365         }
2366
2367         public function textFieldSize( $table, $field ) {
2368                 $table = $this->tableName( $table );
2369                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2370                 $res = $this->query( $sql, __METHOD__ );
2371                 $row = $this->fetchObject( $res );
2372
2373                 $m = [];
2374
2375                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2376                         $size = $m[1];
2377                 } else {
2378                         $size = -1;
2379                 }
2380
2381                 return $size;
2382         }
2383
2384         public function delete( $table, $conds, $fname = __METHOD__ ) {
2385                 if ( !$conds ) {
2386                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2387                 }
2388
2389                 $table = $this->tableName( $table );
2390                 $sql = "DELETE FROM $table";
2391
2392                 if ( $conds != '*' ) {
2393                         if ( is_array( $conds ) ) {
2394                                 $conds = $this->makeList( $conds, self::LIST_AND );
2395                         }
2396                         $sql .= ' WHERE ' . $conds;
2397                 }
2398
2399                 return $this->query( $sql, $fname );
2400         }
2401
2402         public function insertSelect(
2403                 $destTable, $srcTable, $varMap, $conds,
2404                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2405         ) {
2406                 if ( $this->cliMode ) {
2407                         // For massive migrations with downtime, we don't want to select everything
2408                         // into memory and OOM, so do all this native on the server side if possible.
2409                         return $this->nativeInsertSelect(
2410                                 $destTable,
2411                                 $srcTable,
2412                                 $varMap,
2413                                 $conds,
2414                                 $fname,
2415                                 $insertOptions,
2416                                 $selectOptions,
2417                                 $selectJoinConds
2418                         );
2419                 }
2420
2421                 return $this->nonNativeInsertSelect(
2422                         $destTable,
2423                         $srcTable,
2424                         $varMap,
2425                         $conds,
2426                         $fname,
2427                         $insertOptions,
2428                         $selectOptions,
2429                         $selectJoinConds
2430                 );
2431         }
2432
2433         /**
2434          * Implementation of insertSelect() based on select() and insert()
2435          *
2436          * @see IDatabase::insertSelect()
2437          * @since 1.30
2438          * @param string $destTable
2439          * @param string|array $srcTable
2440          * @param array $varMap
2441          * @param array $conds
2442          * @param string $fname
2443          * @param array $insertOptions
2444          * @param array $selectOptions
2445          * @param array $selectJoinConds
2446          * @return bool
2447          */
2448         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2449                 $fname = __METHOD__,
2450                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2451         ) {
2452                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
2453                 // on only the master (without needing row-based-replication). It also makes it easy to
2454                 // know how big the INSERT is going to be.
2455                 $fields = [];
2456                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
2457                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
2458                 }
2459                 $selectOptions[] = 'FOR UPDATE';
2460                 $res = $this->select(
2461                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
2462                 );
2463                 if ( !$res ) {
2464                         return false;
2465                 }
2466
2467                 $rows = [];
2468                 foreach ( $res as $row ) {
2469                         $rows[] = (array)$row;
2470                 }
2471
2472                 return $this->insert( $destTable, $rows, $fname, $insertOptions );
2473         }
2474
2475         /**
2476          * Native server-side implementation of insertSelect() for situations where
2477          * we don't want to select everything into memory
2478          *
2479          * @see IDatabase::insertSelect()
2480          * @param string $destTable
2481          * @param string|array $srcTable
2482          * @param array $varMap
2483          * @param array $conds
2484          * @param string $fname
2485          * @param array $insertOptions
2486          * @param array $selectOptions
2487          * @param array $selectJoinConds
2488          * @return bool
2489          */
2490         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2491                 $fname = __METHOD__,
2492                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2493         ) {
2494                 $destTable = $this->tableName( $destTable );
2495
2496                 if ( !is_array( $insertOptions ) ) {
2497                         $insertOptions = [ $insertOptions ];
2498                 }
2499
2500                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2501
2502                 $selectSql = $this->selectSQLText(
2503                         $srcTable,
2504                         array_values( $varMap ),
2505                         $conds,
2506                         $fname,
2507                         $selectOptions,
2508                         $selectJoinConds
2509                 );
2510
2511                 $sql = "INSERT $insertOptions" .
2512                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
2513                         $selectSql;
2514
2515                 return $this->query( $sql, $fname );
2516         }
2517
2518         /**
2519          * Construct a LIMIT query with optional offset. This is used for query
2520          * pages. The SQL should be adjusted so that only the first $limit rows
2521          * are returned. If $offset is provided as well, then the first $offset
2522          * rows should be discarded, and the next $limit rows should be returned.
2523          * If the result of the query is not ordered, then the rows to be returned
2524          * are theoretically arbitrary.
2525          *
2526          * $sql is expected to be a SELECT, if that makes a difference.
2527          *
2528          * The version provided by default works in MySQL and SQLite. It will very
2529          * likely need to be overridden for most other DBMSes.
2530          *
2531          * @param string $sql SQL query we will append the limit too
2532          * @param int $limit The SQL limit
2533          * @param int|bool $offset The SQL offset (default false)
2534          * @throws DBUnexpectedError
2535          * @return string
2536          */
2537         public function limitResult( $sql, $limit, $offset = false ) {
2538                 if ( !is_numeric( $limit ) ) {
2539                         throw new DBUnexpectedError( $this,
2540                                 "Invalid non-numeric limit passed to limitResult()\n" );
2541                 }
2542
2543                 return "$sql LIMIT "
2544                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2545                 . "{$limit} ";
2546         }
2547
2548         public function unionSupportsOrderAndLimit() {
2549                 return true; // True for almost every DB supported
2550         }
2551
2552         public function unionQueries( $sqls, $all ) {
2553                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2554
2555                 return '(' . implode( $glue, $sqls ) . ')';
2556         }
2557
2558         public function unionConditionPermutations(
2559                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
2560                 $options = [], $join_conds = []
2561         ) {
2562                 // First, build the Cartesian product of $permute_conds
2563                 $conds = [ [] ];
2564                 foreach ( $permute_conds as $field => $values ) {
2565                         if ( !$values ) {
2566                                 // Skip empty $values
2567                                 continue;
2568                         }
2569                         $values = array_unique( $values ); // For sanity
2570                         $newConds = [];
2571                         foreach ( $conds as $cond ) {
2572                                 foreach ( $values as $value ) {
2573                                         $cond[$field] = $value;
2574                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
2575                                 }
2576                         }
2577                         $conds = $newConds;
2578                 }
2579
2580                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
2581
2582                 // If there's just one condition and no subordering, hand off to
2583                 // selectSQLText directly.
2584                 if ( count( $conds ) === 1 &&
2585                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
2586                 ) {
2587                         return $this->selectSQLText(
2588                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
2589                         );
2590                 }
2591
2592                 // Otherwise, we need to pull out the order and limit to apply after
2593                 // the union. Then build the SQL queries for each set of conditions in
2594                 // $conds. Then union them together (using UNION ALL, because the
2595                 // product *should* already be distinct).
2596                 $orderBy = $this->makeOrderBy( $options );
2597                 $limit = isset( $options['LIMIT'] ) ? $options['LIMIT'] : null;
2598                 $offset = isset( $options['OFFSET'] ) ? $options['OFFSET'] : false;
2599                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
2600                 if ( !$this->unionSupportsOrderAndLimit() ) {
2601                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
2602                 } else {
2603                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
2604                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
2605                         }
2606                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
2607                                 // We need to increase the limit by the offset rather than
2608                                 // using the offset directly, otherwise it'll skip incorrectly
2609                                 // in the subqueries.
2610                                 $options['LIMIT'] = $limit + $offset;
2611                                 unset( $options['OFFSET'] );
2612                         }
2613                 }
2614
2615                 $sqls = [];
2616                 foreach ( $conds as $cond ) {
2617                         $sqls[] = $this->selectSQLText(
2618                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
2619                         );
2620                 }
2621                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
2622                 if ( $limit !== null ) {
2623                         $sql = $this->limitResult( $sql, $limit, $offset );
2624                 }
2625
2626                 return $sql;
2627         }
2628
2629         public function conditional( $cond, $trueVal, $falseVal ) {
2630                 if ( is_array( $cond ) ) {
2631                         $cond = $this->makeList( $cond, self::LIST_AND );
2632                 }
2633
2634                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2635         }
2636
2637         public function strreplace( $orig, $old, $new ) {
2638                 return "REPLACE({$orig}, {$old}, {$new})";
2639         }
2640
2641         public function getServerUptime() {
2642                 return 0;
2643         }
2644
2645         public function wasDeadlock() {
2646                 return false;
2647         }
2648
2649         public function wasLockTimeout() {
2650                 return false;
2651         }
2652
2653         public function wasErrorReissuable() {
2654                 return false;
2655         }
2656
2657         public function wasReadOnlyError() {
2658                 return false;
2659         }
2660
2661         /**
2662          * Do not use this method outside of Database/DBError classes
2663          *
2664          * @param int|string $errno
2665          * @return bool Whether the given query error was a connection drop
2666          */
2667         public function wasConnectionError( $errno ) {
2668                 return false;
2669         }
2670
2671         public function deadlockLoop() {
2672                 $args = func_get_args();
2673                 $function = array_shift( $args );
2674                 $tries = self::DEADLOCK_TRIES;
2675
2676                 $this->begin( __METHOD__ );
2677
2678                 $retVal = null;
2679                 /** @var Exception $e */
2680                 $e = null;
2681                 do {
2682                         try {
2683                                 $retVal = call_user_func_array( $function, $args );
2684                                 break;
2685                         } catch ( DBQueryError $e ) {
2686                                 if ( $this->wasDeadlock() ) {
2687                                         // Retry after a randomized delay
2688                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
2689                                 } else {
2690                                         // Throw the error back up
2691                                         throw $e;
2692                                 }
2693                         }
2694                 } while ( --$tries > 0 );
2695
2696                 if ( $tries <= 0 ) {
2697                         // Too many deadlocks; give up
2698                         $this->rollback( __METHOD__ );
2699                         throw $e;
2700                 } else {
2701                         $this->commit( __METHOD__ );
2702
2703                         return $retVal;
2704                 }
2705         }
2706
2707         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2708                 # Real waits are implemented in the subclass.
2709                 return 0;
2710         }
2711
2712         public function getReplicaPos() {
2713                 # Stub
2714                 return false;
2715         }
2716
2717         public function getMasterPos() {
2718                 # Stub
2719                 return false;
2720         }
2721
2722         public function serverIsReadOnly() {
2723                 return false;
2724         }
2725
2726         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
2727                 if ( !$this->mTrxLevel ) {
2728                         throw new DBUnexpectedError( $this, "No transaction is active." );
2729                 }
2730                 $this->mTrxEndCallbacks[] = [ $callback, $fname ];
2731         }
2732
2733         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
2734                 $this->mTrxIdleCallbacks[] = [ $callback, $fname ];
2735                 if ( !$this->mTrxLevel ) {
2736                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
2737                 }
2738         }
2739
2740         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
2741                 if ( $this->mTrxLevel || $this->getFlag( self::DBO_TRX ) ) {
2742                         // As long as DBO_TRX is set, writes will accumulate until the load balancer issues
2743                         // an implicit commit of all peer databases. This is true even if a transaction has
2744                         // not yet been triggered by writes; make sure $callback runs *after* any such writes.
2745                         $this->mTrxPreCommitCallbacks[] = [ $callback, $fname ];
2746                 } else {
2747                         // No transaction is active nor will start implicitly, so make one for this callback
2748                         $this->startAtomic( __METHOD__ );
2749                         try {
2750                                 call_user_func( $callback );
2751                                 $this->endAtomic( __METHOD__ );
2752                         } catch ( Exception $e ) {
2753                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2754                                 throw $e;
2755                         }
2756                 }
2757         }
2758
2759         final public function setTransactionListener( $name, callable $callback = null ) {
2760                 if ( $callback ) {
2761                         $this->mTrxRecurringCallbacks[$name] = $callback;
2762                 } else {
2763                         unset( $this->mTrxRecurringCallbacks[$name] );
2764                 }
2765         }
2766
2767         /**
2768          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
2769          *
2770          * This method should not be used outside of Database/LoadBalancer
2771          *
2772          * @param bool $suppress
2773          * @since 1.28
2774          */
2775         final public function setTrxEndCallbackSuppression( $suppress ) {
2776                 $this->mTrxEndCallbacksSuppressed = $suppress;
2777         }
2778
2779         /**
2780          * Actually run and consume any "on transaction idle/resolution" callbacks.
2781          *
2782          * This method should not be used outside of Database/LoadBalancer
2783          *
2784          * @param int $trigger IDatabase::TRIGGER_* constant
2785          * @since 1.20
2786          * @throws Exception
2787          */
2788         public function runOnTransactionIdleCallbacks( $trigger ) {
2789                 if ( $this->mTrxEndCallbacksSuppressed ) {
2790                         return;
2791                 }
2792
2793                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
2794                 /** @var Exception $e */
2795                 $e = null; // first exception
2796                 do { // callbacks may add callbacks :)
2797                         $callbacks = array_merge(
2798                                 $this->mTrxIdleCallbacks,
2799                                 $this->mTrxEndCallbacks // include "transaction resolution" callbacks
2800                         );
2801                         $this->mTrxIdleCallbacks = []; // consumed (and recursion guard)
2802                         $this->mTrxEndCallbacks = []; // consumed (recursion guard)
2803                         foreach ( $callbacks as $callback ) {
2804                                 try {
2805                                         list( $phpCallback ) = $callback;
2806                                         $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
2807                                         call_user_func_array( $phpCallback, [ $trigger ] );
2808                                         if ( $autoTrx ) {
2809                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
2810                                         } else {
2811                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
2812                                         }
2813                                 } catch ( Exception $ex ) {
2814                                         call_user_func( $this->errorLogger, $ex );
2815                                         $e = $e ?: $ex;
2816                                         // Some callbacks may use startAtomic/endAtomic, so make sure
2817                                         // their transactions are ended so other callbacks don't fail
2818                                         if ( $this->trxLevel() ) {
2819                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2820                                         }
2821                                 }
2822                         }
2823                 } while ( count( $this->mTrxIdleCallbacks ) );
2824
2825                 if ( $e instanceof Exception ) {
2826                         throw $e; // re-throw any first exception
2827                 }
2828         }
2829
2830         /**
2831          * Actually run and consume any "on transaction pre-commit" callbacks.
2832          *
2833          * This method should not be used outside of Database/LoadBalancer
2834          *
2835          * @since 1.22
2836          * @throws Exception
2837          */
2838         public function runOnTransactionPreCommitCallbacks() {
2839                 $e = null; // first exception
2840                 do { // callbacks may add callbacks :)
2841                         $callbacks = $this->mTrxPreCommitCallbacks;
2842                         $this->mTrxPreCommitCallbacks = []; // consumed (and recursion guard)
2843                         foreach ( $callbacks as $callback ) {
2844                                 try {
2845                                         list( $phpCallback ) = $callback;
2846                                         call_user_func( $phpCallback );
2847                                 } catch ( Exception $ex ) {
2848                                         call_user_func( $this->errorLogger, $ex );
2849                                         $e = $e ?: $ex;
2850                                 }
2851                         }
2852                 } while ( count( $this->mTrxPreCommitCallbacks ) );
2853
2854                 if ( $e instanceof Exception ) {
2855                         throw $e; // re-throw any first exception
2856                 }
2857         }
2858
2859         /**
2860          * Actually run any "transaction listener" callbacks.
2861          *
2862          * This method should not be used outside of Database/LoadBalancer
2863          *
2864          * @param int $trigger IDatabase::TRIGGER_* constant
2865          * @throws Exception
2866          * @since 1.20
2867          */
2868         public function runTransactionListenerCallbacks( $trigger ) {
2869                 if ( $this->mTrxEndCallbacksSuppressed ) {
2870                         return;
2871                 }
2872
2873                 /** @var Exception $e */
2874                 $e = null; // first exception
2875
2876                 foreach ( $this->mTrxRecurringCallbacks as $phpCallback ) {
2877                         try {
2878                                 $phpCallback( $trigger, $this );
2879                         } catch ( Exception $ex ) {
2880                                 call_user_func( $this->errorLogger, $ex );
2881                                 $e = $e ?: $ex;
2882                         }
2883                 }
2884
2885                 if ( $e instanceof Exception ) {
2886                         throw $e; // re-throw any first exception
2887                 }
2888         }
2889
2890         final public function startAtomic( $fname = __METHOD__ ) {
2891                 if ( !$this->mTrxLevel ) {
2892                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2893                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
2894                         // in all changes being in one transaction to keep requests transactional.
2895                         if ( !$this->getFlag( self::DBO_TRX ) ) {
2896                                 $this->mTrxAutomaticAtomic = true;
2897                         }
2898                 }
2899
2900                 $this->mTrxAtomicLevels[] = $fname;
2901         }
2902
2903         final public function endAtomic( $fname = __METHOD__ ) {
2904                 if ( !$this->mTrxLevel ) {
2905                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
2906                 }
2907                 if ( !$this->mTrxAtomicLevels ||
2908                         array_pop( $this->mTrxAtomicLevels ) !== $fname
2909                 ) {
2910                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
2911                 }
2912
2913                 if ( !$this->mTrxAtomicLevels && $this->mTrxAutomaticAtomic ) {
2914                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2915                 }
2916         }
2917
2918         final public function doAtomicSection( $fname, callable $callback ) {
2919                 $this->startAtomic( $fname );
2920                 try {
2921                         $res = call_user_func_array( $callback, [ $this, $fname ] );
2922                 } catch ( Exception $e ) {
2923                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2924                         throw $e;
2925                 }
2926                 $this->endAtomic( $fname );
2927
2928                 return $res;
2929         }
2930
2931         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
2932                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
2933                 if ( $this->mTrxLevel ) {
2934                         if ( $this->mTrxAtomicLevels ) {
2935                                 $levels = implode( ', ', $this->mTrxAtomicLevels );
2936                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
2937                                 throw new DBUnexpectedError( $this, $msg );
2938                         } elseif ( !$this->mTrxAutomatic ) {
2939                                 $msg = "$fname: Explicit transaction already active (from {$this->mTrxFname}).";
2940                                 throw new DBUnexpectedError( $this, $msg );
2941                         } else {
2942                                 // @TODO: make this an exception at some point
2943                                 $msg = "$fname: Implicit transaction already active (from {$this->mTrxFname}).";
2944                                 $this->queryLogger->error( $msg );
2945                                 return; // join the main transaction set
2946                         }
2947                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
2948                         // @TODO: make this an exception at some point
2949                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
2950                         $this->queryLogger->error( $msg );
2951                         return; // let any writes be in the main transaction
2952                 }
2953
2954                 // Avoid fatals if close() was called
2955                 $this->assertOpen();
2956
2957                 $this->doBegin( $fname );
2958                 $this->mTrxTimestamp = microtime( true );
2959                 $this->mTrxFname = $fname;
2960                 $this->mTrxDoneWrites = false;
2961                 $this->mTrxAutomaticAtomic = false;
2962                 $this->mTrxAtomicLevels = [];
2963                 $this->mTrxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
2964                 $this->mTrxWriteDuration = 0.0;
2965                 $this->mTrxWriteQueryCount = 0;
2966                 $this->mTrxWriteAffectedRows = 0;
2967                 $this->mTrxWriteAdjDuration = 0.0;
2968                 $this->mTrxWriteAdjQueryCount = 0;
2969                 $this->mTrxWriteCallers = [];
2970                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
2971                 // Get an estimate of the replica DB lag before then, treating estimate staleness
2972                 // as lag itself just to be safe
2973                 $status = $this->getApproximateLagStatus();
2974                 $this->mTrxReplicaLag = $status['lag'] + ( microtime( true ) - $status['since'] );
2975                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
2976                 // caller will think its OK to muck around with the transaction just because startAtomic()
2977                 // has not yet completed (e.g. setting mTrxAtomicLevels).
2978                 $this->mTrxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
2979         }
2980
2981         /**
2982          * Issues the BEGIN command to the database server.
2983          *
2984          * @see Database::begin()
2985          * @param string $fname
2986          */
2987         protected function doBegin( $fname ) {
2988                 $this->query( 'BEGIN', $fname );
2989                 $this->mTrxLevel = 1;
2990         }
2991
2992         final public function commit( $fname = __METHOD__, $flush = '' ) {
2993                 if ( $this->mTrxLevel && $this->mTrxAtomicLevels ) {
2994                         // There are still atomic sections open. This cannot be ignored
2995                         $levels = implode( ', ', $this->mTrxAtomicLevels );
2996                         throw new DBUnexpectedError(
2997                                 $this,
2998                                 "$fname: Got COMMIT while atomic sections $levels are still open."
2999                         );
3000                 }
3001
3002                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3003                         if ( !$this->mTrxLevel ) {
3004                                 return; // nothing to do
3005                         } elseif ( !$this->mTrxAutomatic ) {
3006                                 throw new DBUnexpectedError(
3007                                         $this,
3008                                         "$fname: Flushing an explicit transaction, getting out of sync."
3009                                 );
3010                         }
3011                 } else {
3012                         if ( !$this->mTrxLevel ) {
3013                                 $this->queryLogger->error(
3014                                         "$fname: No transaction to commit, something got out of sync." );
3015                                 return; // nothing to do
3016                         } elseif ( $this->mTrxAutomatic ) {
3017                                 // @TODO: make this an exception at some point
3018                                 $msg = "$fname: Explicit commit of implicit transaction.";
3019                                 $this->queryLogger->error( $msg );
3020                                 return; // wait for the main transaction set commit round
3021                         }
3022                 }
3023
3024                 // Avoid fatals if close() was called
3025                 $this->assertOpen();
3026
3027                 $this->runOnTransactionPreCommitCallbacks();
3028                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3029                 $this->doCommit( $fname );
3030                 if ( $this->mTrxDoneWrites ) {
3031                         $this->mLastWriteTime = microtime( true );
3032                         $this->trxProfiler->transactionWritingOut(
3033                                 $this->mServer,
3034                                 $this->mDBname,
3035                                 $this->mTrxShortId,
3036                                 $writeTime,
3037                                 $this->mTrxWriteAffectedRows
3038                         );
3039                 }
3040
3041                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3042                 $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3043         }
3044
3045         /**
3046          * Issues the COMMIT command to the database server.
3047          *
3048          * @see Database::commit()
3049          * @param string $fname
3050          */
3051         protected function doCommit( $fname ) {
3052                 if ( $this->mTrxLevel ) {
3053                         $this->query( 'COMMIT', $fname );
3054                         $this->mTrxLevel = 0;
3055                 }
3056         }
3057
3058         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3059                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3060                         if ( !$this->mTrxLevel ) {
3061                                 return; // nothing to do
3062                         }
3063                 } else {
3064                         if ( !$this->mTrxLevel ) {
3065                                 $this->queryLogger->error(
3066                                         "$fname: No transaction to rollback, something got out of sync." );
3067                                 return; // nothing to do
3068                         } elseif ( $this->getFlag( self::DBO_TRX ) ) {
3069                                 throw new DBUnexpectedError(
3070                                         $this,
3071                                         "$fname: Expected mass rollback of all peer databases (DBO_TRX set)."
3072                                 );
3073                         }
3074                 }
3075
3076                 // Avoid fatals if close() was called
3077                 $this->assertOpen();
3078
3079                 $this->doRollback( $fname );
3080                 $this->mTrxAtomicLevels = [];
3081                 if ( $this->mTrxDoneWrites ) {
3082                         $this->trxProfiler->transactionWritingOut(
3083                                 $this->mServer,
3084                                 $this->mDBname,
3085                                 $this->mTrxShortId
3086                         );
3087                 }
3088
3089                 $this->mTrxIdleCallbacks = []; // clear
3090                 $this->mTrxPreCommitCallbacks = []; // clear
3091                 try {
3092                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
3093                 } catch ( Exception $e ) {
3094                         // already logged; finish and let LoadBalancer move on during mass-rollback
3095                 }
3096                 try {
3097                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
3098                 } catch ( Exception $e ) {
3099                         // already logged; let LoadBalancer move on during mass-rollback
3100                 }
3101         }
3102
3103         /**
3104          * Issues the ROLLBACK command to the database server.
3105          *
3106          * @see Database::rollback()
3107          * @param string $fname
3108          */
3109         protected function doRollback( $fname ) {
3110                 if ( $this->mTrxLevel ) {
3111                         # Disconnects cause rollback anyway, so ignore those errors
3112                         $ignoreErrors = true;
3113                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
3114                         $this->mTrxLevel = 0;
3115                 }
3116         }
3117
3118         public function flushSnapshot( $fname = __METHOD__ ) {
3119                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
3120                         // This only flushes transactions to clear snapshots, not to write data
3121                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3122                         throw new DBUnexpectedError(
3123                                 $this,
3124                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
3125                         );
3126                 }
3127
3128                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3129         }
3130
3131         public function explicitTrxActive() {
3132                 return $this->mTrxLevel && ( $this->mTrxAtomicLevels || !$this->mTrxAutomatic );
3133         }
3134
3135         public function duplicateTableStructure(
3136                 $oldName, $newName, $temporary = false, $fname = __METHOD__
3137         ) {
3138                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3139         }
3140
3141         public function listTables( $prefix = null, $fname = __METHOD__ ) {
3142                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3143         }
3144
3145         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3146                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3147         }
3148
3149         public function timestamp( $ts = 0 ) {
3150                 $t = new ConvertibleTimestamp( $ts );
3151                 // Let errors bubble up to avoid putting garbage in the DB
3152                 return $t->getTimestamp( TS_MW );
3153         }
3154
3155         public function timestampOrNull( $ts = null ) {
3156                 if ( is_null( $ts ) ) {
3157                         return null;
3158                 } else {
3159                         return $this->timestamp( $ts );
3160                 }
3161         }
3162
3163         /**
3164          * Take the result from a query, and wrap it in a ResultWrapper if
3165          * necessary. Boolean values are passed through as is, to indicate success
3166          * of write queries or failure.
3167          *
3168          * Once upon a time, Database::query() returned a bare MySQL result
3169          * resource, and it was necessary to call this function to convert it to
3170          * a wrapper. Nowadays, raw database objects are never exposed to external
3171          * callers, so this is unnecessary in external code.
3172          *
3173          * @param bool|ResultWrapper|resource|object $result
3174          * @return bool|ResultWrapper
3175          */
3176         protected function resultObject( $result ) {
3177                 if ( !$result ) {
3178                         return false;
3179                 } elseif ( $result instanceof ResultWrapper ) {
3180                         return $result;
3181                 } elseif ( $result === true ) {
3182                         // Successful write query
3183                         return $result;
3184                 } else {
3185                         return new ResultWrapper( $this, $result );
3186                 }
3187         }
3188
3189         public function ping( &$rtt = null ) {
3190                 // Avoid hitting the server if it was hit recently
3191                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
3192                         if ( !func_num_args() || $this->mRTTEstimate > 0 ) {
3193                                 $rtt = $this->mRTTEstimate;
3194                                 return true; // don't care about $rtt
3195                         }
3196                 }
3197
3198                 // This will reconnect if possible or return false if not
3199                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
3200                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
3201                 $this->restoreFlags( self::RESTORE_PRIOR );
3202
3203                 if ( $ok ) {
3204                         $rtt = $this->mRTTEstimate;
3205                 }
3206
3207                 return $ok;
3208         }
3209
3210         /**
3211          * Close existing database connection and open a new connection
3212          *
3213          * @return bool True if new connection is opened successfully, false if error
3214          */
3215         protected function reconnect() {
3216                 $this->closeConnection();
3217                 $this->mOpened = false;
3218                 $this->mConn = false;
3219                 try {
3220                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3221                         $this->lastPing = microtime( true );
3222                         $ok = true;
3223                 } catch ( DBConnectionError $e ) {
3224                         $ok = false;
3225                 }
3226
3227                 return $ok;
3228         }
3229
3230         public function getSessionLagStatus() {
3231                 return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
3232         }
3233
3234         /**
3235          * Get the replica DB lag when the current transaction started
3236          *
3237          * This is useful when transactions might use snapshot isolation
3238          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
3239          * is this lag plus transaction duration. If they don't, it is still
3240          * safe to be pessimistic. This returns null if there is no transaction.
3241          *
3242          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
3243          * @since 1.27
3244          */
3245         protected function getTransactionLagStatus() {
3246                 return $this->mTrxLevel
3247                         ? [ 'lag' => $this->mTrxReplicaLag, 'since' => $this->trxTimestamp() ]
3248                         : null;
3249         }
3250
3251         /**
3252          * Get a replica DB lag estimate for this server
3253          *
3254          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
3255          * @since 1.27
3256          */
3257         protected function getApproximateLagStatus() {
3258                 return [
3259                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
3260                         'since' => microtime( true )
3261                 ];
3262         }
3263
3264         /**
3265          * Merge the result of getSessionLagStatus() for several DBs
3266          * using the most pessimistic values to estimate the lag of
3267          * any data derived from them in combination
3268          *
3269          * This is information is useful for caching modules
3270          *
3271          * @see WANObjectCache::set()
3272          * @see WANObjectCache::getWithSetCallback()
3273          *
3274          * @param IDatabase $db1
3275          * @param IDatabase $dbs,...
3276          * @return array Map of values:
3277          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3278          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3279          *   - pending: whether any of the DBs have uncommitted changes
3280          * @since 1.27
3281          */
3282         public static function getCacheSetOptions( IDatabase $db1 ) {
3283                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3284                 foreach ( func_get_args() as $db ) {
3285                         /** @var IDatabase $db */
3286                         $status = $db->getSessionLagStatus();
3287                         if ( $status['lag'] === false ) {
3288                                 $res['lag'] = false;
3289                         } elseif ( $res['lag'] !== false ) {
3290                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3291                         }
3292                         $res['since'] = min( $res['since'], $status['since'] );
3293                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3294                 }
3295
3296                 return $res;
3297         }
3298
3299         public function getLag() {
3300                 return 0;
3301         }
3302
3303         public function maxListLen() {
3304                 return 0;
3305         }
3306
3307         public function encodeBlob( $b ) {
3308                 return $b;
3309         }
3310
3311         public function decodeBlob( $b ) {
3312                 if ( $b instanceof Blob ) {
3313                         $b = $b->fetch();
3314                 }
3315                 return $b;
3316         }
3317
3318         public function setSessionOptions( array $options ) {
3319         }
3320
3321         public function sourceFile(
3322                 $filename,
3323                 callable $lineCallback = null,
3324                 callable $resultCallback = null,
3325                 $fname = false,
3326                 callable $inputCallback = null
3327         ) {
3328                 MediaWiki\suppressWarnings();
3329                 $fp = fopen( $filename, 'r' );
3330                 MediaWiki\restoreWarnings();
3331
3332                 if ( false === $fp ) {
3333                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
3334                 }
3335
3336                 if ( !$fname ) {
3337                         $fname = __METHOD__ . "( $filename )";
3338                 }
3339
3340                 try {
3341                         $error = $this->sourceStream(
3342                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3343                 } catch ( Exception $e ) {
3344                         fclose( $fp );
3345                         throw $e;
3346                 }
3347
3348                 fclose( $fp );
3349
3350                 return $error;
3351         }
3352
3353         public function setSchemaVars( $vars ) {
3354                 $this->mSchemaVars = $vars;
3355         }
3356
3357         public function sourceStream(
3358                 $fp,
3359                 callable $lineCallback = null,
3360                 callable $resultCallback = null,
3361                 $fname = __METHOD__,
3362                 callable $inputCallback = null
3363         ) {
3364                 $cmd = '';
3365
3366                 while ( !feof( $fp ) ) {
3367                         if ( $lineCallback ) {
3368                                 call_user_func( $lineCallback );
3369                         }
3370
3371                         $line = trim( fgets( $fp ) );
3372
3373                         if ( $line == '' ) {
3374                                 continue;
3375                         }
3376
3377                         if ( '-' == $line[0] && '-' == $line[1] ) {
3378                                 continue;
3379                         }
3380
3381                         if ( $cmd != '' ) {
3382                                 $cmd .= ' ';
3383                         }
3384
3385                         $done = $this->streamStatementEnd( $cmd, $line );
3386
3387                         $cmd .= "$line\n";
3388
3389                         if ( $done || feof( $fp ) ) {
3390                                 $cmd = $this->replaceVars( $cmd );
3391
3392                                 if ( !$inputCallback || call_user_func( $inputCallback, $cmd ) ) {
3393                                         $res = $this->query( $cmd, $fname );
3394
3395                                         if ( $resultCallback ) {
3396                                                 call_user_func( $resultCallback, $res, $this );
3397                                         }
3398
3399                                         if ( false === $res ) {
3400                                                 $err = $this->lastError();
3401
3402                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3403                                         }
3404                                 }
3405                                 $cmd = '';
3406                         }
3407                 }
3408
3409                 return true;
3410         }
3411
3412         /**
3413          * Called by sourceStream() to check if we've reached a statement end
3414          *
3415          * @param string &$sql SQL assembled so far
3416          * @param string &$newLine New line about to be added to $sql
3417          * @return bool Whether $newLine contains end of the statement
3418          */
3419         public function streamStatementEnd( &$sql, &$newLine ) {
3420                 if ( $this->delimiter ) {
3421                         $prev = $newLine;
3422                         $newLine = preg_replace(
3423                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3424                         if ( $newLine != $prev ) {
3425                                 return true;
3426                         }
3427                 }
3428
3429                 return false;
3430         }
3431
3432         /**
3433          * Database independent variable replacement. Replaces a set of variables
3434          * in an SQL statement with their contents as given by $this->getSchemaVars().
3435          *
3436          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3437          *
3438          * - '{$var}' should be used for text and is passed through the database's
3439          *   addQuotes method.
3440          * - `{$var}` should be used for identifiers (e.g. table and database names).
3441          *   It is passed through the database's addIdentifierQuotes method which
3442          *   can be overridden if the database uses something other than backticks.
3443          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
3444          *   database's tableName method.
3445          * - / *i* / passes the name that follows through the database's indexName method.
3446          * - In all other cases, / *$var* / is left unencoded. Except for table options,
3447          *   its use should be avoided. In 1.24 and older, string encoding was applied.
3448          *
3449          * @param string $ins SQL statement to replace variables in
3450          * @return string The new SQL statement with variables replaced
3451          */
3452         protected function replaceVars( $ins ) {
3453                 $vars = $this->getSchemaVars();
3454                 return preg_replace_callback(
3455                         '!
3456                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
3457                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
3458                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
3459                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
3460                         !x',
3461                         function ( $m ) use ( $vars ) {
3462                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
3463                                 // check for both nonexistent keys *and* the empty string.
3464                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
3465                                         if ( $m[1] === 'i' ) {
3466                                                 return $this->indexName( $m[2] );
3467                                         } else {
3468                                                 return $this->tableName( $m[2] );
3469                                         }
3470                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
3471                                         return $this->addQuotes( $vars[$m[3]] );
3472                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
3473                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
3474                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
3475                                         return $vars[$m[5]];
3476                                 } else {
3477                                         return $m[0];
3478                                 }
3479                         },
3480                         $ins
3481                 );
3482         }
3483
3484         /**
3485          * Get schema variables. If none have been set via setSchemaVars(), then
3486          * use some defaults from the current object.
3487          *
3488          * @return array
3489          */
3490         protected function getSchemaVars() {
3491                 if ( $this->mSchemaVars ) {
3492                         return $this->mSchemaVars;
3493                 } else {
3494                         return $this->getDefaultSchemaVars();
3495                 }
3496         }
3497
3498         /**
3499          * Get schema variables to use if none have been set via setSchemaVars().
3500          *
3501          * Override this in derived classes to provide variables for tables.sql
3502          * and SQL patch files.
3503          *
3504          * @return array
3505          */
3506         protected function getDefaultSchemaVars() {
3507                 return [];
3508         }
3509
3510         public function lockIsFree( $lockName, $method ) {
3511                 return true;
3512         }
3513
3514         public function lock( $lockName, $method, $timeout = 5 ) {
3515                 $this->mNamedLocksHeld[$lockName] = 1;
3516
3517                 return true;
3518         }
3519
3520         public function unlock( $lockName, $method ) {
3521                 unset( $this->mNamedLocksHeld[$lockName] );
3522
3523                 return true;
3524         }
3525
3526         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
3527                 if ( $this->writesOrCallbacksPending() ) {
3528                         // This only flushes transactions to clear snapshots, not to write data
3529                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3530                         throw new DBUnexpectedError(
3531                                 $this,
3532                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
3533                         );
3534                 }
3535
3536                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
3537                         return null;
3538                 }
3539
3540                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
3541                         if ( $this->trxLevel() ) {
3542                                 // There is a good chance an exception was thrown, causing any early return
3543                                 // from the caller. Let any error handler get a chance to issue rollback().
3544                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
3545                                 $this->onTransactionResolution(
3546                                         function () use ( $lockKey, $fname ) {
3547                                                 $this->unlock( $lockKey, $fname );
3548                                         },
3549                                         $fname
3550                                 );
3551                         } else {
3552                                 $this->unlock( $lockKey, $fname );
3553                         }
3554                 } );
3555
3556                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3557
3558                 return $unlocker;
3559         }
3560
3561         public function namedLocksEnqueue() {
3562                 return false;
3563         }
3564
3565         public function tableLocksHaveTransactionScope() {
3566                 return true;
3567         }
3568
3569         final public function lockTables( array $read, array $write, $method ) {
3570                 if ( $this->writesOrCallbacksPending() ) {
3571                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
3572                 }
3573
3574                 if ( $this->tableLocksHaveTransactionScope() ) {
3575                         $this->startAtomic( $method );
3576                 }
3577
3578                 return $this->doLockTables( $read, $write, $method );
3579         }
3580
3581         /**
3582          * Helper function for lockTables() that handles the actual table locking
3583          *
3584          * @param array $read Array of tables to lock for read access
3585          * @param array $write Array of tables to lock for write access
3586          * @param string $method Name of caller
3587          * @return true
3588          */
3589         protected function doLockTables( array $read, array $write, $method ) {
3590                 return true;
3591         }
3592
3593         final public function unlockTables( $method ) {
3594                 if ( $this->tableLocksHaveTransactionScope() ) {
3595                         $this->endAtomic( $method );
3596
3597                         return true; // locks released on COMMIT/ROLLBACK
3598                 }
3599
3600                 return $this->doUnlockTables( $method );
3601         }
3602
3603         /**
3604          * Helper function for unlockTables() that handles the actual table unlocking
3605          *
3606          * @param string $method Name of caller
3607          * @return true
3608          */
3609         protected function doUnlockTables( $method ) {
3610                 return true;
3611         }
3612
3613         /**
3614          * Delete a table
3615          * @param string $tableName
3616          * @param string $fName
3617          * @return bool|ResultWrapper
3618          * @since 1.18
3619          */
3620         public function dropTable( $tableName, $fName = __METHOD__ ) {
3621                 if ( !$this->tableExists( $tableName, $fName ) ) {
3622                         return false;
3623                 }
3624                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
3625
3626                 return $this->query( $sql, $fName );
3627         }
3628
3629         public function getInfinity() {
3630                 return 'infinity';
3631         }
3632
3633         public function encodeExpiry( $expiry ) {
3634                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3635                         ? $this->getInfinity()
3636                         : $this->timestamp( $expiry );
3637         }
3638
3639         public function decodeExpiry( $expiry, $format = TS_MW ) {
3640                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
3641                         return 'infinity';
3642                 }
3643
3644                 return ConvertibleTimestamp::convert( $format, $expiry );
3645         }
3646
3647         public function setBigSelects( $value = true ) {
3648                 // no-op
3649         }
3650
3651         public function isReadOnly() {
3652                 return ( $this->getReadOnlyReason() !== false );
3653         }
3654
3655         /**
3656          * @return string|bool Reason this DB is read-only or false if it is not
3657          */
3658         protected function getReadOnlyReason() {
3659                 $reason = $this->getLBInfo( 'readOnlyReason' );
3660
3661                 return is_string( $reason ) ? $reason : false;
3662         }
3663
3664         public function setTableAliases( array $aliases ) {
3665                 $this->tableAliases = $aliases;
3666         }
3667
3668         /**
3669          * @return bool Whether a DB user is required to access the DB
3670          * @since 1.28
3671          */
3672         protected function requiresDatabaseUser() {
3673                 return true;
3674         }
3675
3676         /**
3677          * Get the underlying binding handle, mConn
3678          *
3679          * Makes sure that mConn is set (disconnects and ping() failure can unset it).
3680          * This catches broken callers than catch and ignore disconnection exceptions.
3681          * Unlike checking isOpen(), this is safe to call inside of open().
3682          *
3683          * @return resource|object
3684          * @throws DBUnexpectedError
3685          * @since 1.26
3686          */
3687         protected function getBindingHandle() {
3688                 if ( !$this->mConn ) {
3689                         throw new DBUnexpectedError(
3690                                 $this,
3691                                 'DB connection was already closed or the connection dropped.'
3692                         );
3693                 }
3694
3695                 return $this->mConn;
3696         }
3697
3698         /**
3699          * @since 1.19
3700          * @return string
3701          */
3702         public function __toString() {
3703                 return (string)$this->mConn;
3704         }
3705
3706         /**
3707          * Make sure that copies do not share the same client binding handle
3708          * @throws DBConnectionError
3709          */
3710         public function __clone() {
3711                 $this->connLogger->warning(
3712                         "Cloning " . static::class . " is not recomended; forking connection:\n" .
3713                         ( new RuntimeException() )->getTraceAsString()
3714                 );
3715
3716                 if ( $this->isOpen() ) {
3717                         // Open a new connection resource without messing with the old one
3718                         $this->mOpened = false;
3719                         $this->mConn = false;
3720                         $this->mTrxEndCallbacks = []; // don't copy
3721                         $this->handleSessionLoss(); // no trx or locks anymore
3722                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3723                         $this->lastPing = microtime( true );
3724                 }
3725         }
3726
3727         /**
3728          * Called by serialize. Throw an exception when DB connection is serialized.
3729          * This causes problems on some database engines because the connection is
3730          * not restored on unserialize.
3731          */
3732         public function __sleep() {
3733                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
3734                         'the connection is not restored on wakeup.' );
3735         }
3736
3737         /**
3738          * Run a few simple sanity checks and close dangling connections
3739          */
3740         public function __destruct() {
3741                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
3742                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
3743                 }
3744
3745                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
3746                 if ( $danglingWriters ) {
3747                         $fnames = implode( ', ', $danglingWriters );
3748                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
3749                 }
3750
3751                 if ( $this->mConn ) {
3752                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
3753                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
3754                         \MediaWiki\suppressWarnings();
3755                         $this->closeConnection();
3756                         \MediaWiki\restoreWarnings();
3757                         $this->mConn = false;
3758                         $this->mOpened = false;
3759                 }
3760         }
3761 }
3762
3763 class_alias( Database::class, 'DatabaseBase' ); // b/c for old name
3764 class_alias( Database::class, 'Database' ); // b/c global alias