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                         // setFlag()/clearFlag() do not allow DBO_IGNORE changes for sanity
 465                         if ( $ignoreErrors ) {
 466                                 $this->mFlags |= self::DBO_IGNORE;
 467                         } else {
 468                                 $this->mFlags &= ~self::DBO_IGNORE;
 469                         }
 470                 }
 471
 472                 return $res;
 473         }
 474
 475         public function trxLevel() {
 476                 return $this->mTrxLevel;
 477         }
 478
 479         public function trxTimestamp() {
 480                 return $this->mTrxLevel ? $this->mTrxTimestamp : null;
 481         }
 482
 483         public function tablePrefix( $prefix = null ) {
 484                 $old = $this->mTablePrefix;
 485                 if ( $prefix !== null ) {
 486                         $this->mTablePrefix = $prefix;
 487                         $this->currentDomain = ( $this->mDBname != '' )
 488                                 ? new DatabaseDomain( $this->mDBname, null, $this->mTablePrefix )
 489                                 : DatabaseDomain::newUnspecified();
 490                 }
 491
 492                 return $old;
 493         }
 494
 495         public function dbSchema( $schema = null ) {
 496                 $old = $this->mSchema;
 497                 if ( $schema !== null ) {
 498                         $this->mSchema = $schema;
 499                 }
 500
 501                 return $old;
 502         }
 503
 504         public function getLBInfo( $name = null ) {
 505                 if ( is_null( $name ) ) {
 506                         return $this->mLBInfo;
 507                 } else {
 508                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 509                                 return $this->mLBInfo[$name];
 510                         } else {
 511                                 return null;
 512                         }
 513                 }
 514         }
 515
 516         public function setLBInfo( $name, $value = null ) {
 517                 if ( is_null( $value ) ) {
 518                         $this->mLBInfo = $name;
 519                 } else {
 520                         $this->mLBInfo[$name] = $value;
 521                 }
 522         }
 523
 524         public function setLazyMasterHandle( IDatabase $conn ) {
 525                 $this->lazyMasterHandle = $conn;
 526         }
 527
 528         /**
 529          * @return IDatabase|null
 530          * @see setLazyMasterHandle()
 531          * @since 1.27
 532          */
 533         protected function getLazyMasterHandle() {
 534                 return $this->lazyMasterHandle;
 535         }
 536
 537         public function implicitGroupby() {
 538                 return true;
 539         }
 540
 541         public function implicitOrderby() {
 542                 return true;
 543         }
 544
 545         public function lastQuery() {
 546                 return $this->mLastQuery;
 547         }
 548
 549         public function doneWrites() {
 550                 return (bool)$this->mLastWriteTime;
 551         }
 552
 553         public function lastDoneWrites() {
 554                 return $this->mLastWriteTime ?: false;
 555         }
 556
 557         public function writesPending() {
 558                 return $this->mTrxLevel && $this->mTrxDoneWrites;
 559         }
 560
 561         public function writesOrCallbacksPending() {
 562                 return $this->mTrxLevel && (
 563                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 564                 );
 565         }
 566
 567         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 568                 if ( !$this->mTrxLevel ) {
 569                         return false;
 570                 } elseif ( !$this->mTrxDoneWrites ) {
 571                         return 0.0;
 572                 }
 573
 574                 switch ( $type ) {
 575                         case self::ESTIMATE_DB_APPLY:
 576                                 $this->ping( $rtt );
 577                                 $rttAdjTotal = $this->mTrxWriteAdjQueryCount * $rtt;
 578                                 $applyTime = max( $this->mTrxWriteAdjDuration - $rttAdjTotal, 0 );
 579                                 // For omitted queries, make them count as something at least
 580                                 $omitted = $this->mTrxWriteQueryCount - $this->mTrxWriteAdjQueryCount;
 581                                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 582
 583                                 return $applyTime;
 584                         default: // everything
 585                                 return $this->mTrxWriteDuration;
 586                 }
 587         }
 588
 589         public function pendingWriteCallers() {
 590                 return $this->mTrxLevel ? $this->mTrxWriteCallers : [];
 591         }
 592
 593         public function pendingWriteRowsAffected() {
 594                 return $this->mTrxWriteAffectedRows;
 595         }
 596
 597         /**
 598          * Get the list of method names that have pending write queries or callbacks
 599          * for this transaction
 600          *
 601          * @return array
 602          */
 603         protected function pendingWriteAndCallbackCallers() {
 604                 if ( !$this->mTrxLevel ) {
 605                         return [];
 606                 }
 607
 608                 $fnames = $this->mTrxWriteCallers;
 609                 foreach ( [
 610                         $this->mTrxIdleCallbacks,
 611                         $this->mTrxPreCommitCallbacks,
 612                         $this->mTrxEndCallbacks
 613                 ] as $callbacks ) {
 614                         foreach ( $callbacks as $callback ) {
 615                                 $fnames[] = $callback[1];
 616                         }
 617                 }
 618
 619                 return $fnames;
 620         }
 621
 622         public function isOpen() {
 623                 return $this->mOpened;
 624         }
 625
 626         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 627                 if ( ( $flag & self::DBO_IGNORE ) ) {
 628                         throw new \UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 629                 }
 630
 631                 if ( $remember === self::REMEMBER_PRIOR ) {
 632                         array_push( $this->priorFlags, $this->mFlags );
 633                 }
 634                 $this->mFlags |= $flag;
 635         }
 636
 637         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 638                 if ( ( $flag & self::DBO_IGNORE ) ) {
 639                         throw new \UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 640                 }
 641
 642                 if ( $remember === self::REMEMBER_PRIOR ) {
 643                         array_push( $this->priorFlags, $this->mFlags );
 644                 }
 645                 $this->mFlags &= ~$flag;
 646         }
 647
 648         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 649                 if ( !$this->priorFlags ) {
 650                         return;
 651                 }
 652
 653                 if ( $state === self::RESTORE_INITIAL ) {
 654                         $this->mFlags = reset( $this->priorFlags );
 655                         $this->priorFlags = [];
 656                 } else {
 657                         $this->mFlags = array_pop( $this->priorFlags );
 658                 }
 659         }
 660
 661         public function getFlag( $flag ) {
 662                 return !!( $this->mFlags & $flag );
 663         }
 664
 665         /**
 666          * @param string $name Class field name
 667          * @return mixed
 668          * @deprecated Since 1.28
 669          */
 670         public function getProperty( $name ) {
 671                 return $this->$name;
 672         }
 673
 674         public function getDomainID() {
 675                 return $this->currentDomain->getId();
 676         }
 677
 678         final public function getWikiID() {
 679                 return $this->getDomainID();
 680         }
 681
 682         /**
 683          * Get information about an index into an object
 684          * @param string $table Table name
 685          * @param string $index Index name
 686          * @param string $fname Calling function name
 687          * @return mixed Database-specific index description class or false if the index does not exist
 688          */
 689         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 690
 691         /**
 692          * Wrapper for addslashes()
 693          *
 694          * @param string $s String to be slashed.
 695          * @return string Slashed string.
 696          */
 697         abstract function strencode( $s );
 698
 699         /**
 700          * Set a custom error handler for logging errors during database connection
 701          */
 702         protected function installErrorHandler() {
 703                 $this->mPHPError = false;
 704                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 705                 set_error_handler( [ $this, 'connectionErrorLogger' ] );
 706         }
 707
 708         /**
 709          * Restore the previous error handler and return the last PHP error for this DB
 710          *
 711          * @return bool|string
 712          */
 713         protected function restoreErrorHandler() {
 714                 restore_error_handler();
 715                 if ( $this->htmlErrors !== false ) {
 716                         ini_set( 'html_errors', $this->htmlErrors );
 717                 }
 718
 719                 return $this->getLastPHPError();
 720         }
 721
 722         /**
 723          * @return string|bool Last PHP error for this DB (typically connection errors)
 724          */
 725         protected function getLastPHPError() {
 726                 if ( $this->mPHPError ) {
 727                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 728                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 729
 730                         return $error;
 731                 }
 732
 733                 return false;
 734         }
 735
 736         /**
 737          * Error handler for logging errors during database connection
 738          * This method should not be used outside of Database classes
 739          *
 740          * @param int $errno
 741          * @param string $errstr
 742          */
 743         public function connectionErrorLogger( $errno, $errstr ) {
 744                 $this->mPHPError = $errstr;
 745         }
 746
 747         /**
 748          * Create a log context to pass to PSR-3 logger functions.
 749          *
 750          * @param array $extras Additional data to add to context
 751          * @return array
 752          */
 753         protected function getLogContext( array $extras = [] ) {
 754                 return array_merge(
 755                         [
 756                                 'db_server' => $this->mServer,
 757                                 'db_name' => $this->mDBname,
 758                                 'db_user' => $this->mUser,
 759                         ],
 760                         $extras
 761                 );
 762         }
 763
 764         public function close() {
 765                 if ( $this->mConn ) {
 766                         if ( $this->trxLevel() ) {
 767                                 $this->commit( __METHOD__, self::FLUSHING_INTERNAL );
 768                         }
 769
 770                         $closed = $this->closeConnection();
 771                         $this->mConn = false;
 772                 } elseif (
 773                         $this->mTrxIdleCallbacks ||
 774                         $this->mTrxPreCommitCallbacks ||
 775                         $this->mTrxEndCallbacks
 776                 ) { // sanity
 777                         throw new RuntimeException( "Transaction callbacks still pending." );
 778                 } else {
 779                         $closed = true;
 780                 }
 781                 $this->mOpened = false;
 782
 783                 return $closed;
 784         }
 785
 786         /**
 787          * Make sure isOpen() returns true as a sanity check
 788          *
 789          * @throws DBUnexpectedError
 790          */
 791         protected function assertOpen() {
 792                 if ( !$this->isOpen() ) {
 793                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
 794                 }
 795         }
 796
 797         /**
 798          * Closes underlying database connection
 799          * @since 1.20
 800          * @return bool Whether connection was closed successfully
 801          */
 802         abstract protected function closeConnection();
 803
 804         public function reportConnectionError( $error = 'Unknown error' ) {
 805                 $myError = $this->lastError();
 806                 if ( $myError ) {
 807                         $error = $myError;
 808                 }
 809
 810                 # New method
 811                 throw new DBConnectionError( $this, $error );
 812         }
 813
 814         /**
 815          * The DBMS-dependent part of query()
 816          *
 817          * @param string $sql SQL query.
 818          * @return ResultWrapper|bool Result object to feed to fetchObject,
 819          *   fetchRow, ...; or false on failure
 820          */
 821         abstract protected function doQuery( $sql );
 822
 823         /**
 824          * Determine whether a query writes to the DB.
 825          * Should return true if unsure.
 826          *
 827          * @param string $sql
 828          * @return bool
 829          */
 830         protected function isWriteQuery( $sql ) {
 831                 return !preg_match(
 832                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 833         }
 834
 835         /**
 836          * @param string $sql
 837          * @return string|null
 838          */
 839         protected function getQueryVerb( $sql ) {
 840                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
 841         }
 842
 843         /**
 844          * Determine whether a SQL statement is sensitive to isolation level.
 845          * A SQL statement is considered transactable if its result could vary
 846          * depending on the transaction isolation level. Operational commands
 847          * such as 'SET' and 'SHOW' are not considered to be transactable.
 848          *
 849          * @param string $sql
 850          * @return bool
 851          */
 852         protected function isTransactableQuery( $sql ) {
 853                 return !in_array(
 854                         $this->getQueryVerb( $sql ),
 855                         [ 'BEGIN', 'COMMIT', 'ROLLBACK', 'SHOW', 'SET', 'CREATE', 'ALTER' ],
 856                         true
 857                 );
 858         }
 859
 860         /**
 861          * @param string $sql A SQL query
 862          * @return bool Whether $sql is SQL for TEMPORARY table operation
 863          */
 864         protected function registerTempTableOperation( $sql ) {
 865                 if ( preg_match(
 866                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 867                         $sql,
 868                         $matches
 869                 ) ) {
 870                         $this->mSessionTempTables[$matches[1]] = 1;
 871
 872                         return true;
 873                 } elseif ( preg_match(
 874                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 875                         $sql,
 876                         $matches
 877                 ) ) {
 878                         $isTemp = isset( $this->mSessionTempTables[$matches[1]] );
 879                         unset( $this->mSessionTempTables[$matches[1]] );
 880
 881                         return $isTemp;
 882                 } elseif ( preg_match(
 883                         '/^TRUNCATE\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 884                         $sql,
 885                         $matches
 886                 ) ) {
 887                         return isset( $this->mSessionTempTables[$matches[1]] );
 888                 } elseif ( preg_match(
 889                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
 890                         $sql,
 891                         $matches
 892                 ) ) {
 893                         return isset( $this->mSessionTempTables[$matches[1]] );
 894                 }
 895
 896                 return false;
 897         }
 898
 899         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 900                 $priorWritesPending = $this->writesOrCallbacksPending();
 901                 $this->mLastQuery = $sql;
 902
 903                 $isWrite = $this->isWriteQuery( $sql );
 904                 if ( $isWrite ) {
 905                         $isNonTempWrite = !$this->registerTempTableOperation( $sql );
 906                 } else {
 907                         $isNonTempWrite = false;
 908                 }
 909
 910                 if ( $isWrite ) {
 911                         if ( $this->getLBInfo( 'replica' ) === true ) {
 912                                 throw new DBError(
 913                                         $this,
 914                                         'Write operations are not allowed on replica database connections.'
 915                                 );
 916                         }
 917                         # In theory, non-persistent writes are allowed in read-only mode, but due to things
 918                         # like https://bugs.mysql.com/bug.php?id=33669 that might not work anyway...
 919                         $reason = $this->getReadOnlyReason();
 920                         if ( $reason !== false ) {
 921                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
 922                         }
 923                         # Set a flag indicating that writes have been done
 924                         $this->mLastWriteTime = microtime( true );
 925                 }
 926
 927                 # Add trace comment to the begin of the sql string, right after the operator.
 928                 # Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598)
 929                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
 930
 931                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
 932                 if ( !$this->mTrxLevel && $this->getFlag( self::DBO_TRX )
 933                         && $this->isTransactableQuery( $sql )
 934                 ) {
 935                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
 936                         $this->mTrxAutomatic = true;
 937                 }
 938
 939                 # Keep track of whether the transaction has write queries pending
 940                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $isWrite ) {
 941                         $this->mTrxDoneWrites = true;
 942                         $this->trxProfiler->transactionWritingIn(
 943                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
 944                 }
 945
 946                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
 947                         $this->queryLogger->debug( "{$this->mDBname} {$commentedSql}" );
 948                 }
 949
 950                 # Avoid fatals if close() was called
 951                 $this->assertOpen();
 952
 953                 # Send the query to the server
 954                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
 955
 956                 # Try reconnecting if the connection was lost
 957                 if ( false === $ret && $this->wasErrorReissuable() ) {
 958                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
 959                         # Stash the last error values before anything might clear them
 960                         $lastError = $this->lastError();
 961                         $lastErrno = $this->lastErrno();
 962                         # Update state tracking to reflect transaction loss due to disconnection
 963                         $this->handleSessionLoss();
 964                         if ( $this->reconnect() ) {
 965                                 $msg = __METHOD__ . ': lost connection to {dbserver}; reconnected';
 966                                 $params = [ 'dbserver' => $this->getServer() ];
 967                                 $this->connLogger->warning( $msg, $params );
 968                                 $this->queryLogger->warning( $msg, $params +
 969                                         [ 'trace' => ( new RuntimeException() )->getTraceAsString() ] );
 970
 971                                 if ( !$recoverable ) {
 972                                         # Callers may catch the exception and continue to use the DB
 973                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname );
 974                                 } else {
 975                                         # Should be safe to silently retry the query
 976                                         $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
 977                                 }
 978                         } else {
 979                                 $msg = __METHOD__ . ': lost connection to {dbserver} permanently';
 980                                 $this->connLogger->error( $msg, [ 'dbserver' => $this->getServer() ] );
 981                         }
 982                 }
 983
 984                 if ( false === $ret ) {
 985                         # Deadlocks cause the entire transaction to abort, not just the statement.
 986                         # https://dev.mysql.com/doc/refman/5.7/en/innodb-error-handling.html
 987                         # https://www.postgresql.org/docs/9.1/static/explicit-locking.html
 988                         if ( $this->wasDeadlock() ) {
 989                                 if ( $this->explicitTrxActive() || $priorWritesPending ) {
 990                                         $tempIgnore = false; // not recoverable
 991                                 }
 992                                 # Update state tracking to reflect transaction loss
 993                                 $this->handleSessionLoss();
 994                         }
 995
 996                         $this->reportQueryError(
 997                                 $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 998                 }
 999
1000                 $res = $this->resultObject( $ret );
1001
1002                 return $res;
1003         }
1004
1005         /**
1006          * Helper method for query() that handles profiling and logging and sends
1007          * the query to doQuery()
1008          *
1009          * @param string $sql Original SQL query
1010          * @param string $commentedSql SQL query with debugging/trace comment
1011          * @param bool $isWrite Whether the query is a (non-temporary) write operation
1012          * @param string $fname Name of the calling function
1013          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
1014          *     object for a successful read query, or false on failure
1015          */
1016         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
1017                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1018                 # generalizeSQL() will probably cut down the query to reasonable
1019                 # logging size most of the time. The substr is really just a sanity check.
1020                 if ( $isMaster ) {
1021                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1022                 } else {
1023                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1024                 }
1025
1026                 # Include query transaction state
1027                 $queryProf .= $this->mTrxShortId ? " [TRX#{$this->mTrxShortId}]" : "";
1028
1029                 $startTime = microtime( true );
1030                 if ( $this->profiler ) {
1031                         call_user_func( [ $this->profiler, 'profileIn' ], $queryProf );
1032                 }
1033                 $ret = $this->doQuery( $commentedSql );
1034                 if ( $this->profiler ) {
1035                         call_user_func( [ $this->profiler, 'profileOut' ], $queryProf );
1036                 }
1037                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1038
1039                 unset( $queryProfSection ); // profile out (if set)
1040
1041                 if ( $ret !== false ) {
1042                         $this->lastPing = $startTime;
1043                         if ( $isWrite && $this->mTrxLevel ) {
1044                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1045                                 $this->mTrxWriteCallers[] = $fname;
1046                         }
1047                 }
1048
1049                 if ( $sql === self::PING_QUERY ) {
1050                         $this->mRTTEstimate = $queryRuntime;
1051                 }
1052
1053                 $this->trxProfiler->recordQueryCompletion(
1054                         $queryProf, $startTime, $isWrite, $this->affectedRows()
1055                 );
1056                 $this->queryLogger->debug( $sql, [
1057                         'method' => $fname,
1058                         'master' => $isMaster,
1059                         'runtime' => $queryRuntime,
1060                 ] );
1061
1062                 return $ret;
1063         }
1064
1065         /**
1066          * Update the estimated run-time of a query, not counting large row lock times
1067          *
1068          * LoadBalancer can be set to rollback transactions that will create huge replication
1069          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1070          * queries, like inserting a row can take a long time due to row locking. This method
1071          * uses some simple heuristics to discount those cases.
1072          *
1073          * @param string $sql A SQL write query
1074          * @param float $runtime Total runtime, including RTT
1075          * @param int $affected Affected row count
1076          */
1077         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1078                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1079                 $indicativeOfReplicaRuntime = true;
1080                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1081                         $verb = $this->getQueryVerb( $sql );
1082                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1083                         if ( $verb === 'INSERT' ) {
1084                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1085                         } elseif ( $verb === 'REPLACE' ) {
1086                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1087                         }
1088                 }
1089
1090                 $this->mTrxWriteDuration += $runtime;
1091                 $this->mTrxWriteQueryCount += 1;
1092                 $this->mTrxWriteAffectedRows += $affected;
1093                 if ( $indicativeOfReplicaRuntime ) {
1094                         $this->mTrxWriteAdjDuration += $runtime;
1095                         $this->mTrxWriteAdjQueryCount += 1;
1096                 }
1097         }
1098
1099         /**
1100          * Determine whether or not it is safe to retry queries after a database
1101          * connection is lost
1102          *
1103          * @param string $sql SQL query
1104          * @param bool $priorWritesPending Whether there is a transaction open with
1105          *     possible write queries or transaction pre-commit/idle callbacks
1106          *     waiting on it to finish.
1107          * @return bool True if it is safe to retry the query, false otherwise
1108          */
1109         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1110                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1111                 # Dropped connections also mean that named locks are automatically released.
1112                 # Only allow error suppression in autocommit mode or when the lost transaction
1113                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1114                 if ( $this->mNamedLocksHeld ) {
1115                         return false; // possible critical section violation
1116                 } elseif ( $sql === 'COMMIT' ) {
1117                         return !$priorWritesPending; // nothing written anyway? (T127428)
1118                 } elseif ( $sql === 'ROLLBACK' ) {
1119                         return true; // transaction lost...which is also what was requested :)
1120                 } elseif ( $this->explicitTrxActive() ) {
1121                         return false; // don't drop atomocity
1122                 } elseif ( $priorWritesPending ) {
1123                         return false; // prior writes lost from implicit transaction
1124                 }
1125
1126                 return true;
1127         }
1128
1129         /**
1130          * Clean things up after transaction loss due to disconnection
1131          *
1132          * @return null|Exception
1133          */
1134         private function handleSessionLoss() {
1135                 $this->mTrxLevel = 0;
1136                 $this->mTrxIdleCallbacks = []; // T67263
1137                 $this->mTrxPreCommitCallbacks = []; // T67263
1138                 $this->mSessionTempTables = [];
1139                 $this->mNamedLocksHeld = [];
1140                 try {
1141                         // Handle callbacks in mTrxEndCallbacks
1142                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1143                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1144                         return null;
1145                 } catch ( Exception $e ) {
1146                         // Already logged; move on...
1147                         return $e;
1148                 }
1149         }
1150
1151         /**
1152          * Checks whether the cause of the error is detected to be a timeout.
1153          *
1154          * It returns false by default, and not all engines support detecting this yet.
1155          * If this returns false, it will be treated as a generic query error.
1156          *
1157          * @param string $error Error text
1158          * @param int $errno Error number
1159          * @return bool
1160          */
1161         protected function wasQueryTimeout( $error, $errno ) {
1162                 return false;
1163         }
1164
1165         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1166                 if ( $this->ignoreErrors() || $tempIgnore ) {
1167                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1168                 } else {
1169                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1170                         $this->queryLogger->error(
1171                                 "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1172                                 $this->getLogContext( [
1173                                         'method' => __METHOD__,
1174                                         'errno' => $errno,
1175                                         'error' => $error,
1176                                         'sql1line' => $sql1line,
1177                                         'fname' => $fname,
1178                                 ] )
1179                         );
1180                         $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1181                         $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1182                         if ( $wasQueryTimeout ) {
1183                                 throw new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1184                         } else {
1185                                 throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1186                         }
1187                 }
1188         }
1189
1190         public function freeResult( $res ) {
1191         }
1192
1193         public function selectField(
1194                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1195         ) {
1196                 if ( $var === '*' ) { // sanity
1197                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1198                 }
1199
1200                 if ( !is_array( $options ) ) {
1201                         $options = [ $options ];
1202                 }
1203
1204                 $options['LIMIT'] = 1;
1205
1206                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1207                 if ( $res === false || !$this->numRows( $res ) ) {
1208                         return false;
1209                 }
1210
1211                 $row = $this->fetchRow( $res );
1212
1213                 if ( $row !== false ) {
1214                         return reset( $row );
1215                 } else {
1216                         return false;
1217                 }
1218         }
1219
1220         public function selectFieldValues(
1221                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1222         ) {
1223                 if ( $var === '*' ) { // sanity
1224                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1225                 } elseif ( !is_string( $var ) ) { // sanity
1226                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1227                 }
1228
1229                 if ( !is_array( $options ) ) {
1230                         $options = [ $options ];
1231                 }
1232
1233                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1234                 if ( $res === false ) {
1235                         return false;
1236                 }
1237
1238                 $values = [];
1239                 foreach ( $res as $row ) {
1240                         $values[] = $row->$var;
1241                 }
1242
1243                 return $values;
1244         }
1245
1246         /**
1247          * Returns an optional USE INDEX clause to go after the table, and a
1248          * string to go at the end of the query.
1249          *
1250          * @param array $options Associative array of options to be turned into
1251          *   an SQL query, valid keys are listed in the function.
1252          * @return array
1253          * @see Database::select()
1254          */
1255         protected function makeSelectOptions( $options ) {
1256                 $preLimitTail = $postLimitTail = '';
1257                 $startOpts = '';
1258
1259                 $noKeyOptions = [];
1260
1261                 foreach ( $options as $key => $option ) {
1262                         if ( is_numeric( $key ) ) {
1263                                 $noKeyOptions[$option] = true;
1264                         }
1265                 }
1266
1267                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1268
1269                 $preLimitTail .= $this->makeOrderBy( $options );
1270
1271                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1272                         $postLimitTail .= ' FOR UPDATE';
1273                 }
1274
1275                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1276                         $postLimitTail .= ' LOCK IN SHARE MODE';
1277                 }
1278
1279                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1280                         $startOpts .= 'DISTINCT';
1281                 }
1282
1283                 # Various MySQL extensions
1284                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1285                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1286                 }
1287
1288                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1289                         $startOpts .= ' HIGH_PRIORITY';
1290                 }
1291
1292                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1293                         $startOpts .= ' SQL_BIG_RESULT';
1294                 }
1295
1296                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1297                         $startOpts .= ' SQL_BUFFER_RESULT';
1298                 }
1299
1300                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1301                         $startOpts .= ' SQL_SMALL_RESULT';
1302                 }
1303
1304                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1305                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1306                 }
1307
1308                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1309                         $startOpts .= ' SQL_CACHE';
1310                 }
1311
1312                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1313                         $startOpts .= ' SQL_NO_CACHE';
1314                 }
1315
1316                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1317                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1318                 } else {
1319                         $useIndex = '';
1320                 }
1321                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1322                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1323                 } else {
1324                         $ignoreIndex = '';
1325                 }
1326
1327                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1328         }
1329
1330         /**
1331          * Returns an optional GROUP BY with an optional HAVING
1332          *
1333          * @param array $options Associative array of options
1334          * @return string
1335          * @see Database::select()
1336          * @since 1.21
1337          */
1338         protected function makeGroupByWithHaving( $options ) {
1339                 $sql = '';
1340                 if ( isset( $options['GROUP BY'] ) ) {
1341                         $gb = is_array( $options['GROUP BY'] )
1342                                 ? implode( ',', $options['GROUP BY'] )
1343                                 : $options['GROUP BY'];
1344                         $sql .= ' GROUP BY ' . $gb;
1345                 }
1346                 if ( isset( $options['HAVING'] ) ) {
1347                         $having = is_array( $options['HAVING'] )
1348                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1349                                 : $options['HAVING'];
1350                         $sql .= ' HAVING ' . $having;
1351                 }
1352
1353                 return $sql;
1354         }
1355
1356         /**
1357          * Returns an optional ORDER BY
1358          *
1359          * @param array $options Associative array of options
1360          * @return string
1361          * @see Database::select()
1362          * @since 1.21
1363          */
1364         protected function makeOrderBy( $options ) {
1365                 if ( isset( $options['ORDER BY'] ) ) {
1366                         $ob = is_array( $options['ORDER BY'] )
1367                                 ? implode( ',', $options['ORDER BY'] )
1368                                 : $options['ORDER BY'];
1369
1370                         return ' ORDER BY ' . $ob;
1371                 }
1372
1373                 return '';
1374         }
1375
1376         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1377                 $options = [], $join_conds = [] ) {
1378                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1379
1380                 return $this->query( $sql, $fname );
1381         }
1382
1383         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1384                 $options = [], $join_conds = []
1385         ) {
1386                 if ( is_array( $vars ) ) {
1387                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1388                 }
1389
1390                 $options = (array)$options;
1391                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1392                         ? $options['USE INDEX']
1393                         : [];
1394                 $ignoreIndexes = (
1395                         isset( $options['IGNORE INDEX'] ) &&
1396                         is_array( $options['IGNORE INDEX'] )
1397                 )
1398                         ? $options['IGNORE INDEX']
1399                         : [];
1400
1401                 if ( is_array( $table ) ) {
1402                         $from = ' FROM ' .
1403                                 $this->tableNamesWithIndexClauseOrJOIN(
1404                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1405                 } elseif ( $table != '' ) {
1406                         if ( $table[0] == ' ' ) {
1407                                 $from = ' FROM ' . $table;
1408                         } else {
1409                                 $from = ' FROM ' .
1410                                         $this->tableNamesWithIndexClauseOrJOIN(
1411                                                 [ $table ], $useIndexes, $ignoreIndexes, [] );
1412                         }
1413                 } else {
1414                         $from = '';
1415                 }
1416
1417                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1418                         $this->makeSelectOptions( $options );
1419
1420                 if ( !empty( $conds ) ) {
1421                         if ( is_array( $conds ) ) {
1422                                 $conds = $this->makeList( $conds, self::LIST_AND );
1423                         }
1424                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex " .
1425                                 "WHERE $conds $preLimitTail";
1426                 } else {
1427                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex $preLimitTail";
1428                 }
1429
1430                 if ( isset( $options['LIMIT'] ) ) {
1431                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1432                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1433                 }
1434                 $sql = "$sql $postLimitTail";
1435
1436                 if ( isset( $options['EXPLAIN'] ) ) {
1437                         $sql = 'EXPLAIN ' . $sql;
1438                 }
1439
1440                 return $sql;
1441         }
1442
1443         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1444                 $options = [], $join_conds = []
1445         ) {
1446                 $options = (array)$options;
1447                 $options['LIMIT'] = 1;
1448                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1449
1450                 if ( $res === false ) {
1451                         return false;
1452                 }
1453
1454                 if ( !$this->numRows( $res ) ) {
1455                         return false;
1456                 }
1457
1458                 $obj = $this->fetchObject( $res );
1459
1460                 return $obj;
1461         }
1462
1463         public function estimateRowCount(
1464                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
1465         ) {
1466                 $rows = 0;
1467                 $res = $this->select( $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options );
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         public function selectRowCount(
1478                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1479         ) {
1480                 $rows = 0;
1481                 $sql = $this->selectSQLText( $tables, '1', $conds, $fname, $options, $join_conds );
1482                 // The identifier quotes is primarily for MSSQL.
1483                 $rowCountCol = $this->addIdentifierQuotes( "rowcount" );
1484                 $tableName = $this->addIdentifierQuotes( "tmp_count" );
1485                 $res = $this->query( "SELECT COUNT(*) AS $rowCountCol FROM ($sql) $tableName", $fname );
1486
1487                 if ( $res ) {
1488                         $row = $this->fetchRow( $res );
1489                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1490                 }
1491
1492                 return $rows;
1493         }
1494
1495         /**
1496          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1497          * It's only slightly flawed. Don't use for anything important.
1498          *
1499          * @param string $sql A SQL Query
1500          *
1501          * @return string
1502          */
1503         protected static function generalizeSQL( $sql ) {
1504                 # This does the same as the regexp below would do, but in such a way
1505                 # as to avoid crashing php on some large strings.
1506                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1507
1508                 $sql = str_replace( "\\\\", '', $sql );
1509                 $sql = str_replace( "\\'", '', $sql );
1510                 $sql = str_replace( "\\\"", '', $sql );
1511                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1512                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1513
1514                 # All newlines, tabs, etc replaced by single space
1515                 $sql = preg_replace( '/\s+/', ' ', $sql );
1516
1517                 # All numbers => N,
1518                 # except the ones surrounded by characters, e.g. l10n
1519                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1520                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1521
1522                 return $sql;
1523         }
1524
1525         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1526                 $info = $this->fieldInfo( $table, $field );
1527
1528                 return (bool)$info;
1529         }
1530
1531         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1532                 if ( !$this->tableExists( $table ) ) {
1533                         return null;
1534                 }
1535
1536                 $info = $this->indexInfo( $table, $index, $fname );
1537                 if ( is_null( $info ) ) {
1538                         return null;
1539                 } else {
1540                         return $info !== false;
1541                 }
1542         }
1543
1544         public function tableExists( $table, $fname = __METHOD__ ) {
1545                 $tableRaw = $this->tableName( $table, 'raw' );
1546                 if ( isset( $this->mSessionTempTables[$tableRaw] ) ) {
1547                         return true; // already known to exist
1548                 }
1549
1550                 $table = $this->tableName( $table );
1551                 $ignoreErrors = true;
1552                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname, $ignoreErrors );
1553
1554                 return (bool)$res;
1555         }
1556
1557         public function indexUnique( $table, $index ) {
1558                 $indexInfo = $this->indexInfo( $table, $index );
1559
1560                 if ( !$indexInfo ) {
1561                         return null;
1562                 }
1563
1564                 return !$indexInfo[0]->Non_unique;
1565         }
1566
1567         /**
1568          * Helper for Database::insert().
1569          *
1570          * @param array $options
1571          * @return string
1572          */
1573         protected function makeInsertOptions( $options ) {
1574                 return implode( ' ', $options );
1575         }
1576
1577         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1578                 # No rows to insert, easy just return now
1579                 if ( !count( $a ) ) {
1580                         return true;
1581                 }
1582
1583                 $table = $this->tableName( $table );
1584
1585                 if ( !is_array( $options ) ) {
1586                         $options = [ $options ];
1587                 }
1588
1589                 $fh = null;
1590                 if ( isset( $options['fileHandle'] ) ) {
1591                         $fh = $options['fileHandle'];
1592                 }
1593                 $options = $this->makeInsertOptions( $options );
1594
1595                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1596                         $multi = true;
1597                         $keys = array_keys( $a[0] );
1598                 } else {
1599                         $multi = false;
1600                         $keys = array_keys( $a );
1601                 }
1602
1603                 $sql = 'INSERT ' . $options .
1604                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1605
1606                 if ( $multi ) {
1607                         $first = true;
1608                         foreach ( $a as $row ) {
1609                                 if ( $first ) {
1610                                         $first = false;
1611                                 } else {
1612                                         $sql .= ',';
1613                                 }
1614                                 $sql .= '(' . $this->makeList( $row ) . ')';
1615                         }
1616                 } else {
1617                         $sql .= '(' . $this->makeList( $a ) . ')';
1618                 }
1619
1620                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1621                         return false;
1622                 } elseif ( $fh !== null ) {
1623                         return true;
1624                 }
1625
1626                 return (bool)$this->query( $sql, $fname );
1627         }
1628
1629         /**
1630          * Make UPDATE options array for Database::makeUpdateOptions
1631          *
1632          * @param array $options
1633          * @return array
1634          */
1635         protected function makeUpdateOptionsArray( $options ) {
1636                 if ( !is_array( $options ) ) {
1637                         $options = [ $options ];
1638                 }
1639
1640                 $opts = [];
1641
1642                 if ( in_array( 'IGNORE', $options ) ) {
1643                         $opts[] = 'IGNORE';
1644                 }
1645
1646                 return $opts;
1647         }
1648
1649         /**
1650          * Make UPDATE options for the Database::update function
1651          *
1652          * @param array $options The options passed to Database::update
1653          * @return string
1654          */
1655         protected function makeUpdateOptions( $options ) {
1656                 $opts = $this->makeUpdateOptionsArray( $options );
1657
1658                 return implode( ' ', $opts );
1659         }
1660
1661         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1662                 $table = $this->tableName( $table );
1663                 $opts = $this->makeUpdateOptions( $options );
1664                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
1665
1666                 if ( $conds !== [] && $conds !== '*' ) {
1667                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
1668                 }
1669
1670                 return (bool)$this->query( $sql, $fname );
1671         }
1672
1673         public function makeList( $a, $mode = self::LIST_COMMA ) {
1674                 if ( !is_array( $a ) ) {
1675                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1676                 }
1677
1678                 $first = true;
1679                 $list = '';
1680
1681                 foreach ( $a as $field => $value ) {
1682                         if ( !$first ) {
1683                                 if ( $mode == self::LIST_AND ) {
1684                                         $list .= ' AND ';
1685                                 } elseif ( $mode == self::LIST_OR ) {
1686                                         $list .= ' OR ';
1687                                 } else {
1688                                         $list .= ',';
1689                                 }
1690                         } else {
1691                                 $first = false;
1692                         }
1693
1694                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
1695                                 $list .= "($value)";
1696                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
1697                                 $list .= "$value";
1698                         } elseif (
1699                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
1700                         ) {
1701                                 // Remove null from array to be handled separately if found
1702                                 $includeNull = false;
1703                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
1704                                         $includeNull = true;
1705                                         unset( $value[$nullKey] );
1706                                 }
1707                                 if ( count( $value ) == 0 && !$includeNull ) {
1708                                         throw new InvalidArgumentException(
1709                                                 __METHOD__ . ": empty input for field $field" );
1710                                 } elseif ( count( $value ) == 0 ) {
1711                                         // only check if $field is null
1712                                         $list .= "$field IS NULL";
1713                                 } else {
1714                                         // IN clause contains at least one valid element
1715                                         if ( $includeNull ) {
1716                                                 // Group subconditions to ensure correct precedence
1717                                                 $list .= '(';
1718                                         }
1719                                         if ( count( $value ) == 1 ) {
1720                                                 // Special-case single values, as IN isn't terribly efficient
1721                                                 // Don't necessarily assume the single key is 0; we don't
1722                                                 // enforce linear numeric ordering on other arrays here.
1723                                                 $value = array_values( $value )[0];
1724                                                 $list .= $field . " = " . $this->addQuotes( $value );
1725                                         } else {
1726                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1727                                         }
1728                                         // if null present in array, append IS NULL
1729                                         if ( $includeNull ) {
1730                                                 $list .= " OR $field IS NULL)";
1731                                         }
1732                                 }
1733                         } elseif ( $value === null ) {
1734                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
1735                                         $list .= "$field IS ";
1736                                 } elseif ( $mode == self::LIST_SET ) {
1737                                         $list .= "$field = ";
1738                                 }
1739                                 $list .= 'NULL';
1740                         } else {
1741                                 if (
1742                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
1743                                 ) {
1744                                         $list .= "$field = ";
1745                                 }
1746                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
1747                         }
1748                 }
1749
1750                 return $list;
1751         }
1752
1753         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1754                 $conds = [];
1755
1756                 foreach ( $data as $base => $sub ) {
1757                         if ( count( $sub ) ) {
1758                                 $conds[] = $this->makeList(
1759                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
1760                                         self::LIST_AND );
1761                         }
1762                 }
1763
1764                 if ( $conds ) {
1765                         return $this->makeList( $conds, self::LIST_OR );
1766                 } else {
1767                         // Nothing to search for...
1768                         return false;
1769                 }
1770         }
1771
1772         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1773                 return $valuename;
1774         }
1775
1776         public function bitNot( $field ) {
1777                 return "(~$field)";
1778         }
1779
1780         public function bitAnd( $fieldLeft, $fieldRight ) {
1781                 return "($fieldLeft & $fieldRight)";
1782         }
1783
1784         public function bitOr( $fieldLeft, $fieldRight ) {
1785                 return "($fieldLeft | $fieldRight)";
1786         }
1787
1788         public function buildConcat( $stringList ) {
1789                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1790         }
1791
1792         public function buildGroupConcatField(
1793                 $delim, $table, $field, $conds = '', $join_conds = []
1794         ) {
1795                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
1796
1797                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
1798         }
1799
1800         public function buildStringCast( $field ) {
1801                 return $field;
1802         }
1803
1804         public function databasesAreIndependent() {
1805                 return false;
1806         }
1807
1808         public function selectDB( $db ) {
1809                 # Stub. Shouldn't cause serious problems if it's not overridden, but
1810                 # if your database engine supports a concept similar to MySQL's
1811                 # databases you may as well.
1812                 $this->mDBname = $db;
1813
1814                 return true;
1815         }
1816
1817         public function getDBname() {
1818                 return $this->mDBname;
1819         }
1820
1821         public function getServer() {
1822                 return $this->mServer;
1823         }
1824
1825         public function tableName( $name, $format = 'quoted' ) {
1826                 # Skip the entire process when we have a string quoted on both ends.
1827                 # Note that we check the end so that we will still quote any use of
1828                 # use of `database`.table. But won't break things if someone wants
1829                 # to query a database table with a dot in the name.
1830                 if ( $this->isQuotedIdentifier( $name ) ) {
1831                         return $name;
1832                 }
1833
1834                 # Lets test for any bits of text that should never show up in a table
1835                 # name. Basically anything like JOIN or ON which are actually part of
1836                 # SQL queries, but may end up inside of the table value to combine
1837                 # sql. Such as how the API is doing.
1838                 # Note that we use a whitespace test rather than a \b test to avoid
1839                 # any remote case where a word like on may be inside of a table name
1840                 # surrounded by symbols which may be considered word breaks.
1841                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1842                         return $name;
1843                 }
1844
1845                 # Split database and table into proper variables.
1846                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
1847
1848                 # Quote $table and apply the prefix if not quoted.
1849                 # $tableName might be empty if this is called from Database::replaceVars()
1850                 $tableName = "{$prefix}{$table}";
1851                 if ( $format === 'quoted'
1852                         && !$this->isQuotedIdentifier( $tableName )
1853                         && $tableName !== ''
1854                 ) {
1855                         $tableName = $this->addIdentifierQuotes( $tableName );
1856                 }
1857
1858                 # Quote $schema and $database and merge them with the table name if needed
1859                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
1860                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
1861
1862                 return $tableName;
1863         }
1864
1865         /**
1866          * Get the table components needed for a query given the currently selected database
1867          *
1868          * @param string $name Table name in the form of db.schema.table, db.table, or table
1869          * @return array (DB name or "" for default, schema name, table prefix, table name)
1870          */
1871         protected function qualifiedTableComponents( $name ) {
1872                 # We reverse the explode so that database.table and table both output the correct table.
1873                 $dbDetails = explode( '.', $name, 3 );
1874                 if ( count( $dbDetails ) == 3 ) {
1875                         list( $database, $schema, $table ) = $dbDetails;
1876                         # We don't want any prefix added in this case
1877                         $prefix = '';
1878                 } elseif ( count( $dbDetails ) == 2 ) {
1879                         list( $database, $table ) = $dbDetails;
1880                         # We don't want any prefix added in this case
1881                         $prefix = '';
1882                         # In dbs that support it, $database may actually be the schema
1883                         # but that doesn't affect any of the functionality here
1884                         $schema = '';
1885                 } else {
1886                         list( $table ) = $dbDetails;
1887                         if ( isset( $this->tableAliases[$table] ) ) {
1888                                 $database = $this->tableAliases[$table]['dbname'];
1889                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
1890                                         ? $this->tableAliases[$table]['schema']
1891                                         : $this->mSchema;
1892                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
1893                                         ? $this->tableAliases[$table]['prefix']
1894                                         : $this->mTablePrefix;
1895                         } else {
1896                                 $database = '';
1897                                 $schema = $this->mSchema; # Default schema
1898                                 $prefix = $this->mTablePrefix; # Default prefix
1899                         }
1900                 }
1901
1902                 return [ $database, $schema, $prefix, $table ];
1903         }
1904
1905         /**
1906          * @param string|null $namespace Database or schema
1907          * @param string $relation Name of table, view, sequence, etc...
1908          * @param string $format One of (raw, quoted)
1909          * @return string Relation name with quoted and merged $namespace as needed
1910          */
1911         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
1912                 if ( strlen( $namespace ) ) {
1913                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
1914                                 $namespace = $this->addIdentifierQuotes( $namespace );
1915                         }
1916                         $relation = $namespace . '.' . $relation;
1917                 }
1918
1919                 return $relation;
1920         }
1921
1922         public function tableNames() {
1923                 $inArray = func_get_args();
1924                 $retVal = [];
1925
1926                 foreach ( $inArray as $name ) {
1927                         $retVal[$name] = $this->tableName( $name );
1928                 }
1929
1930                 return $retVal;
1931         }
1932
1933         public function tableNamesN() {
1934                 $inArray = func_get_args();
1935                 $retVal = [];
1936
1937                 foreach ( $inArray as $name ) {
1938                         $retVal[] = $this->tableName( $name );
1939                 }
1940
1941                 return $retVal;
1942         }
1943
1944         /**
1945          * Get an aliased table name
1946          * e.g. tableName AS newTableName
1947          *
1948          * @param string $name Table name, see tableName()
1949          * @param string|bool $alias Alias (optional)
1950          * @return string SQL name for aliased table. Will not alias a table to its own name
1951          */
1952         protected function tableNameWithAlias( $name, $alias = false ) {
1953                 if ( !$alias || $alias == $name ) {
1954                         return $this->tableName( $name );
1955                 } else {
1956                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
1957                 }
1958         }
1959
1960         /**
1961          * Gets an array of aliased table names
1962          *
1963          * @param array $tables [ [alias] => table ]
1964          * @return string[] See tableNameWithAlias()
1965          */
1966         protected function tableNamesWithAlias( $tables ) {
1967                 $retval = [];
1968                 foreach ( $tables as $alias => $table ) {
1969                         if ( is_numeric( $alias ) ) {
1970                                 $alias = $table;
1971                         }
1972                         $retval[] = $this->tableNameWithAlias( $table, $alias );
1973                 }
1974
1975                 return $retval;
1976         }
1977
1978         /**
1979          * Get an aliased field name
1980          * e.g. fieldName AS newFieldName
1981          *
1982          * @param string $name Field name
1983          * @param string|bool $alias Alias (optional)
1984          * @return string SQL name for aliased field. Will not alias a field to its own name
1985          */
1986         protected function fieldNameWithAlias( $name, $alias = false ) {
1987                 if ( !$alias || (string)$alias === (string)$name ) {
1988                         return $name;
1989                 } else {
1990                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
1991                 }
1992         }
1993
1994         /**
1995          * Gets an array of aliased field names
1996          *
1997          * @param array $fields [ [alias] => field ]
1998          * @return string[] See fieldNameWithAlias()
1999          */
2000         protected function fieldNamesWithAlias( $fields ) {
2001                 $retval = [];
2002                 foreach ( $fields as $alias => $field ) {
2003                         if ( is_numeric( $alias ) ) {
2004                                 $alias = $field;
2005                         }
2006                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2007                 }
2008
2009                 return $retval;
2010         }
2011
2012         /**
2013          * Get the aliased table name clause for a FROM clause
2014          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2015          *
2016          * @param array $tables ( [alias] => table )
2017          * @param array $use_index Same as for select()
2018          * @param array $ignore_index Same as for select()
2019          * @param array $join_conds Same as for select()
2020          * @return string
2021          */
2022         protected function tableNamesWithIndexClauseOrJOIN(
2023                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2024         ) {
2025                 $ret = [];
2026                 $retJOIN = [];
2027                 $use_index = (array)$use_index;
2028                 $ignore_index = (array)$ignore_index;
2029                 $join_conds = (array)$join_conds;
2030
2031                 foreach ( $tables as $alias => $table ) {
2032                         if ( !is_string( $alias ) ) {
2033                                 // No alias? Set it equal to the table name
2034                                 $alias = $table;
2035                         }
2036
2037                         if ( is_array( $table ) ) {
2038                                 // A parenthesized group
2039                                 if ( count( $table ) > 1 ) {
2040                                         $joinedTable = '('
2041                                                 . $this->tableNamesWithIndexClauseOrJOIN( $table, $use_index, $ignore_index, $join_conds )
2042                                                 . ')';
2043                                 } else {
2044                                         // Degenerate case
2045                                         $innerTable = reset( $table );
2046                                         $innerAlias = key( $table );
2047                                         $joinedTable = $this->tableNameWithAlias(
2048                                                 $innerTable,
2049                                                 is_string( $innerAlias ) ? $innerAlias : $innerTable
2050                                         );
2051                                 }
2052                         } else {
2053                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2054                         }
2055
2056                         // Is there a JOIN clause for this table?
2057                         if ( isset( $join_conds[$alias] ) ) {
2058                                 list( $joinType, $conds ) = $join_conds[$alias];
2059                                 $tableClause = $joinType;
2060                                 $tableClause .= ' ' . $joinedTable;
2061                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2062                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2063                                         if ( $use != '' ) {
2064                                                 $tableClause .= ' ' . $use;
2065                                         }
2066                                 }
2067                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2068                                         $ignore = $this->ignoreIndexClause(
2069                                                 implode( ',', (array)$ignore_index[$alias] ) );
2070                                         if ( $ignore != '' ) {
2071                                                 $tableClause .= ' ' . $ignore;
2072                                         }
2073                                 }
2074                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2075                                 if ( $on != '' ) {
2076                                         $tableClause .= ' ON (' . $on . ')';
2077                                 }
2078
2079                                 $retJOIN[] = $tableClause;
2080                         } elseif ( isset( $use_index[$alias] ) ) {
2081                                 // Is there an INDEX clause for this table?
2082                                 $tableClause = $joinedTable;
2083                                 $tableClause .= ' ' . $this->useIndexClause(
2084                                                 implode( ',', (array)$use_index[$alias] )
2085                                         );
2086
2087                                 $ret[] = $tableClause;
2088                         } elseif ( isset( $ignore_index[$alias] ) ) {
2089                                 // Is there an INDEX clause for this table?
2090                                 $tableClause = $joinedTable;
2091                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2092                                                 implode( ',', (array)$ignore_index[$alias] )
2093                                         );
2094
2095                                 $ret[] = $tableClause;
2096                         } else {
2097                                 $tableClause = $joinedTable;
2098
2099                                 $ret[] = $tableClause;
2100                         }
2101                 }
2102
2103                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2104                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2105                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2106
2107                 // Compile our final table clause
2108                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2109         }
2110
2111         /**
2112          * Allows for index remapping in queries where this is not consistent across DBMS
2113          *
2114          * @param string $index
2115          * @return string
2116          */
2117         protected function indexName( $index ) {
2118                 return $index;
2119         }
2120
2121         public function addQuotes( $s ) {
2122                 if ( $s instanceof Blob ) {
2123                         $s = $s->fetch();
2124                 }
2125                 if ( $s === null ) {
2126                         return 'NULL';
2127                 } elseif ( is_bool( $s ) ) {
2128                         return (int)$s;
2129                 } else {
2130                         # This will also quote numeric values. This should be harmless,
2131                         # and protects against weird problems that occur when they really
2132                         # _are_ strings such as article titles and string->number->string
2133                         # conversion is not 1:1.
2134                         return "'" . $this->strencode( $s ) . "'";
2135                 }
2136         }
2137
2138         /**
2139          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2140          * MySQL uses `backticks` while basically everything else uses double quotes.
2141          * Since MySQL is the odd one out here the double quotes are our generic
2142          * and we implement backticks in DatabaseMysqlBase.
2143          *
2144          * @param string $s
2145          * @return string
2146          */
2147         public function addIdentifierQuotes( $s ) {
2148                 return '"' . str_replace( '"', '""', $s ) . '"';
2149         }
2150
2151         /**
2152          * Returns if the given identifier looks quoted or not according to
2153          * the database convention for quoting identifiers .
2154          *
2155          * @note Do not use this to determine if untrusted input is safe.
2156          *   A malicious user can trick this function.
2157          * @param string $name
2158          * @return bool
2159          */
2160         public function isQuotedIdentifier( $name ) {
2161                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2162         }
2163
2164         /**
2165          * @param string $s
2166          * @param string $escapeChar
2167          * @return string
2168          */
2169         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2170                 return str_replace( [ $escapeChar, '%', '_' ],
2171                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2172                         $s );
2173         }
2174
2175         public function buildLike() {
2176                 $params = func_get_args();
2177
2178                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2179                         $params = $params[0];
2180                 }
2181
2182                 $s = '';
2183
2184                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2185                 // may escape backslashes, creating problems of double escaping. The `
2186                 // character has good cross-DBMS compatibility, avoiding special operators
2187                 // in MS SQL like ^ and %
2188                 $escapeChar = '`';
2189
2190                 foreach ( $params as $value ) {
2191                         if ( $value instanceof LikeMatch ) {
2192                                 $s .= $value->toString();
2193                         } else {
2194                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2195                         }
2196                 }
2197
2198                 return ' LIKE ' . $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2199         }
2200
2201         public function anyChar() {
2202                 return new LikeMatch( '_' );
2203         }
2204
2205         public function anyString() {
2206                 return new LikeMatch( '%' );
2207         }
2208
2209         public function nextSequenceValue( $seqName ) {
2210                 return null;
2211         }
2212
2213         /**
2214          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2215          * is only needed because a) MySQL must be as efficient as possible due to
2216          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2217          * which index to pick. Anyway, other databases might have different
2218          * indexes on a given table. So don't bother overriding this unless you're
2219          * MySQL.
2220          * @param string $index
2221          * @return string
2222          */
2223         public function useIndexClause( $index ) {
2224                 return '';
2225         }
2226
2227         /**
2228          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2229          * is only needed because a) MySQL must be as efficient as possible due to
2230          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2231          * which index to pick. Anyway, other databases might have different
2232          * indexes on a given table. So don't bother overriding this unless you're
2233          * MySQL.
2234          * @param string $index
2235          * @return string
2236          */
2237         public function ignoreIndexClause( $index ) {
2238                 return '';
2239         }
2240
2241         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2242                 $quotedTable = $this->tableName( $table );
2243
2244                 if ( count( $rows ) == 0 ) {
2245                         return;
2246                 }
2247
2248                 # Single row case
2249                 if ( !is_array( reset( $rows ) ) ) {
2250                         $rows = [ $rows ];
2251                 }
2252
2253                 // @FXIME: this is not atomic, but a trx would break affectedRows()
2254                 foreach ( $rows as $row ) {
2255                         # Delete rows which collide
2256                         if ( $uniqueIndexes ) {
2257                                 $sql = "DELETE FROM $quotedTable WHERE ";
2258                                 $first = true;
2259                                 foreach ( $uniqueIndexes as $index ) {
2260                                         if ( $first ) {
2261                                                 $first = false;
2262                                                 $sql .= '( ';
2263                                         } else {
2264                                                 $sql .= ' ) OR ( ';
2265                                         }
2266                                         if ( is_array( $index ) ) {
2267                                                 $first2 = true;
2268                                                 foreach ( $index as $col ) {
2269                                                         if ( $first2 ) {
2270                                                                 $first2 = false;
2271                                                         } else {
2272                                                                 $sql .= ' AND ';
2273                                                         }
2274                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2275                                                 }
2276                                         } else {
2277                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2278                                         }
2279                                 }
2280                                 $sql .= ' )';
2281                                 $this->query( $sql, $fname );
2282                         }
2283
2284                         # Now insert the row
2285                         $this->insert( $table, $row, $fname );
2286                 }
2287         }
2288
2289         /**
2290          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2291          * statement.
2292          *
2293          * @param string $table Table name
2294          * @param array|string $rows Row(s) to insert
2295          * @param string $fname Caller function name
2296          *
2297          * @return ResultWrapper
2298          */
2299         protected function nativeReplace( $table, $rows, $fname ) {
2300                 $table = $this->tableName( $table );
2301
2302                 # Single row case
2303                 if ( !is_array( reset( $rows ) ) ) {
2304                         $rows = [ $rows ];
2305                 }
2306
2307                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2308                 $first = true;
2309
2310                 foreach ( $rows as $row ) {
2311                         if ( $first ) {
2312                                 $first = false;
2313                         } else {
2314                                 $sql .= ',';
2315                         }
2316
2317                         $sql .= '(' . $this->makeList( $row ) . ')';
2318                 }
2319
2320                 return $this->query( $sql, $fname );
2321         }
2322
2323         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2324                 $fname = __METHOD__
2325         ) {
2326                 if ( !count( $rows ) ) {
2327                         return true; // nothing to do
2328                 }
2329
2330                 if ( !is_array( reset( $rows ) ) ) {
2331                         $rows = [ $rows ];
2332                 }
2333
2334                 if ( count( $uniqueIndexes ) ) {
2335                         $clauses = []; // list WHERE clauses that each identify a single row
2336                         foreach ( $rows as $row ) {
2337                                 foreach ( $uniqueIndexes as $index ) {
2338                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2339                                         $rowKey = []; // unique key to this row
2340                                         foreach ( $index as $column ) {
2341                                                 $rowKey[$column] = $row[$column];
2342                                         }
2343                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2344                                 }
2345                         }
2346                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2347                 } else {
2348                         $where = false;
2349                 }
2350
2351                 $useTrx = !$this->mTrxLevel;
2352                 if ( $useTrx ) {
2353                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2354                 }
2355                 try {
2356                         # Update any existing conflicting row(s)
2357                         if ( $where !== false ) {
2358                                 $ok = $this->update( $table, $set, $where, $fname );
2359                         } else {
2360                                 $ok = true;
2361                         }
2362                         # Now insert any non-conflicting row(s)
2363                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2364                 } catch ( Exception $e ) {
2365                         if ( $useTrx ) {
2366                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
2367                         }
2368                         throw $e;
2369                 }
2370                 if ( $useTrx ) {
2371                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2372                 }
2373
2374                 return $ok;
2375         }
2376
2377         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2378                 $fname = __METHOD__
2379         ) {
2380                 if ( !$conds ) {
2381                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2382                 }
2383
2384                 $delTable = $this->tableName( $delTable );
2385                 $joinTable = $this->tableName( $joinTable );
2386                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2387                 if ( $conds != '*' ) {
2388                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2389                 }
2390                 $sql .= ')';
2391
2392                 $this->query( $sql, $fname );
2393         }
2394
2395         public function textFieldSize( $table, $field ) {
2396                 $table = $this->tableName( $table );
2397                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2398                 $res = $this->query( $sql, __METHOD__ );
2399                 $row = $this->fetchObject( $res );
2400
2401                 $m = [];
2402
2403                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2404                         $size = $m[1];
2405                 } else {
2406                         $size = -1;
2407                 }
2408
2409                 return $size;
2410         }
2411
2412         public function delete( $table, $conds, $fname = __METHOD__ ) {
2413                 if ( !$conds ) {
2414                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2415                 }
2416
2417                 $table = $this->tableName( $table );
2418                 $sql = "DELETE FROM $table";
2419
2420                 if ( $conds != '*' ) {
2421                         if ( is_array( $conds ) ) {
2422                                 $conds = $this->makeList( $conds, self::LIST_AND );
2423                         }
2424                         $sql .= ' WHERE ' . $conds;
2425                 }
2426
2427                 return $this->query( $sql, $fname );
2428         }
2429
2430         public function insertSelect(
2431                 $destTable, $srcTable, $varMap, $conds,
2432                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2433         ) {
2434                 if ( $this->cliMode ) {
2435                         // For massive migrations with downtime, we don't want to select everything
2436                         // into memory and OOM, so do all this native on the server side if possible.
2437                         return $this->nativeInsertSelect(
2438                                 $destTable,
2439                                 $srcTable,
2440                                 $varMap,
2441                                 $conds,
2442                                 $fname,
2443                                 $insertOptions,
2444                                 $selectOptions,
2445                                 $selectJoinConds
2446                         );
2447                 }
2448
2449                 return $this->nonNativeInsertSelect(
2450                         $destTable,
2451                         $srcTable,
2452                         $varMap,
2453                         $conds,
2454                         $fname,
2455                         $insertOptions,
2456                         $selectOptions,
2457                         $selectJoinConds
2458                 );
2459         }
2460
2461         /**
2462          * Implementation of insertSelect() based on select() and insert()
2463          *
2464          * @see IDatabase::insertSelect()
2465          * @since 1.30
2466          * @param string $destTable
2467          * @param string|array $srcTable
2468          * @param array $varMap
2469          * @param array $conds
2470          * @param string $fname
2471          * @param array $insertOptions
2472          * @param array $selectOptions
2473          * @param array $selectJoinConds
2474          * @return bool
2475          */
2476         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2477                 $fname = __METHOD__,
2478                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2479         ) {
2480                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
2481                 // on only the master (without needing row-based-replication). It also makes it easy to
2482                 // know how big the INSERT is going to be.
2483                 $fields = [];
2484                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
2485                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
2486                 }
2487                 $selectOptions[] = 'FOR UPDATE';
2488                 $res = $this->select(
2489                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
2490                 );
2491                 if ( !$res ) {
2492                         return false;
2493                 }
2494
2495                 $rows = [];
2496                 foreach ( $res as $row ) {
2497                         $rows[] = (array)$row;
2498                 }
2499
2500                 return $this->insert( $destTable, $rows, $fname, $insertOptions );
2501         }
2502
2503         /**
2504          * Native server-side implementation of insertSelect() for situations where
2505          * we don't want to select everything into memory
2506          *
2507          * @see IDatabase::insertSelect()
2508          * @param string $destTable
2509          * @param string|array $srcTable
2510          * @param array $varMap
2511          * @param array $conds
2512          * @param string $fname
2513          * @param array $insertOptions
2514          * @param array $selectOptions
2515          * @param array $selectJoinConds
2516          * @return bool
2517          */
2518         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2519                 $fname = __METHOD__,
2520                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2521         ) {
2522                 $destTable = $this->tableName( $destTable );
2523
2524                 if ( !is_array( $insertOptions ) ) {
2525                         $insertOptions = [ $insertOptions ];
2526                 }
2527
2528                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2529
2530                 $selectSql = $this->selectSQLText(
2531                         $srcTable,
2532                         array_values( $varMap ),
2533                         $conds,
2534                         $fname,
2535                         $selectOptions,
2536                         $selectJoinConds
2537                 );
2538
2539                 $sql = "INSERT $insertOptions" .
2540                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
2541                         $selectSql;
2542
2543                 return $this->query( $sql, $fname );
2544         }
2545
2546         /**
2547          * Construct a LIMIT query with optional offset. This is used for query
2548          * pages. The SQL should be adjusted so that only the first $limit rows
2549          * are returned. If $offset is provided as well, then the first $offset
2550          * rows should be discarded, and the next $limit rows should be returned.
2551          * If the result of the query is not ordered, then the rows to be returned
2552          * are theoretically arbitrary.
2553          *
2554          * $sql is expected to be a SELECT, if that makes a difference.
2555          *
2556          * The version provided by default works in MySQL and SQLite. It will very
2557          * likely need to be overridden for most other DBMSes.
2558          *
2559          * @param string $sql SQL query we will append the limit too
2560          * @param int $limit The SQL limit
2561          * @param int|bool $offset The SQL offset (default false)
2562          * @throws DBUnexpectedError
2563          * @return string
2564          */
2565         public function limitResult( $sql, $limit, $offset = false ) {
2566                 if ( !is_numeric( $limit ) ) {
2567                         throw new DBUnexpectedError( $this,
2568                                 "Invalid non-numeric limit passed to limitResult()\n" );
2569                 }
2570
2571                 return "$sql LIMIT "
2572                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2573                 . "{$limit} ";
2574         }
2575
2576         public function unionSupportsOrderAndLimit() {
2577                 return true; // True for almost every DB supported
2578         }
2579
2580         public function unionQueries( $sqls, $all ) {
2581                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2582
2583                 return '(' . implode( $glue, $sqls ) . ')';
2584         }
2585
2586         public function unionConditionPermutations(
2587                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
2588                 $options = [], $join_conds = []
2589         ) {
2590                 // First, build the Cartesian product of $permute_conds
2591                 $conds = [ [] ];
2592                 foreach ( $permute_conds as $field => $values ) {
2593                         if ( !$values ) {
2594                                 // Skip empty $values
2595                                 continue;
2596                         }
2597                         $values = array_unique( $values ); // For sanity
2598                         $newConds = [];
2599                         foreach ( $conds as $cond ) {
2600                                 foreach ( $values as $value ) {
2601                                         $cond[$field] = $value;
2602                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
2603                                 }
2604                         }
2605                         $conds = $newConds;
2606                 }
2607
2608                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
2609
2610                 // If there's just one condition and no subordering, hand off to
2611                 // selectSQLText directly.
2612                 if ( count( $conds ) === 1 &&
2613                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
2614                 ) {
2615                         return $this->selectSQLText(
2616                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
2617                         );
2618                 }
2619
2620                 // Otherwise, we need to pull out the order and limit to apply after
2621                 // the union. Then build the SQL queries for each set of conditions in
2622                 // $conds. Then union them together (using UNION ALL, because the
2623                 // product *should* already be distinct).
2624                 $orderBy = $this->makeOrderBy( $options );
2625                 $limit = isset( $options['LIMIT'] ) ? $options['LIMIT'] : null;
2626                 $offset = isset( $options['OFFSET'] ) ? $options['OFFSET'] : false;
2627                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
2628                 if ( !$this->unionSupportsOrderAndLimit() ) {
2629                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
2630                 } else {
2631                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
2632                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
2633                         }
2634                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
2635                                 // We need to increase the limit by the offset rather than
2636                                 // using the offset directly, otherwise it'll skip incorrectly
2637                                 // in the subqueries.
2638                                 $options['LIMIT'] = $limit + $offset;
2639                                 unset( $options['OFFSET'] );
2640                         }
2641                 }
2642
2643                 $sqls = [];
2644                 foreach ( $conds as $cond ) {
2645                         $sqls[] = $this->selectSQLText(
2646                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
2647                         );
2648                 }
2649                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
2650                 if ( $limit !== null ) {
2651                         $sql = $this->limitResult( $sql, $limit, $offset );
2652                 }
2653
2654                 return $sql;
2655         }
2656
2657         public function conditional( $cond, $trueVal, $falseVal ) {
2658                 if ( is_array( $cond ) ) {
2659                         $cond = $this->makeList( $cond, self::LIST_AND );
2660                 }
2661
2662                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2663         }
2664
2665         public function strreplace( $orig, $old, $new ) {
2666                 return "REPLACE({$orig}, {$old}, {$new})";
2667         }
2668
2669         public function getServerUptime() {
2670                 return 0;
2671         }
2672
2673         public function wasDeadlock() {
2674                 return false;
2675         }
2676
2677         public function wasLockTimeout() {
2678                 return false;
2679         }
2680
2681         public function wasErrorReissuable() {
2682                 return false;
2683         }
2684
2685         public function wasReadOnlyError() {
2686                 return false;
2687         }
2688
2689         /**
2690          * Do not use this method outside of Database/DBError classes
2691          *
2692          * @param int|string $errno
2693          * @return bool Whether the given query error was a connection drop
2694          */
2695         public function wasConnectionError( $errno ) {
2696                 return false;
2697         }
2698
2699         public function deadlockLoop() {
2700                 $args = func_get_args();
2701                 $function = array_shift( $args );
2702                 $tries = self::DEADLOCK_TRIES;
2703
2704                 $this->begin( __METHOD__ );
2705
2706                 $retVal = null;
2707                 /** @var Exception $e */
2708                 $e = null;
2709                 do {
2710                         try {
2711                                 $retVal = call_user_func_array( $function, $args );
2712                                 break;
2713                         } catch ( DBQueryError $e ) {
2714                                 if ( $this->wasDeadlock() ) {
2715                                         // Retry after a randomized delay
2716                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
2717                                 } else {
2718                                         // Throw the error back up
2719                                         throw $e;
2720                                 }
2721                         }
2722                 } while ( --$tries > 0 );
2723
2724                 if ( $tries <= 0 ) {
2725                         // Too many deadlocks; give up
2726                         $this->rollback( __METHOD__ );
2727                         throw $e;
2728                 } else {
2729                         $this->commit( __METHOD__ );
2730
2731                         return $retVal;
2732                 }
2733         }
2734
2735         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2736                 # Real waits are implemented in the subclass.
2737                 return 0;
2738         }
2739
2740         public function getReplicaPos() {
2741                 # Stub
2742                 return false;
2743         }
2744
2745         public function getMasterPos() {
2746                 # Stub
2747                 return false;
2748         }
2749
2750         public function serverIsReadOnly() {
2751                 return false;
2752         }
2753
2754         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
2755                 if ( !$this->mTrxLevel ) {
2756                         throw new DBUnexpectedError( $this, "No transaction is active." );
2757                 }
2758                 $this->mTrxEndCallbacks[] = [ $callback, $fname ];
2759         }
2760
2761         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
2762                 $this->mTrxIdleCallbacks[] = [ $callback, $fname ];
2763                 if ( !$this->mTrxLevel ) {
2764                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
2765                 }
2766         }
2767
2768         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
2769                 if ( $this->mTrxLevel || $this->getFlag( self::DBO_TRX ) ) {
2770                         // As long as DBO_TRX is set, writes will accumulate until the load balancer issues
2771                         // an implicit commit of all peer databases. This is true even if a transaction has
2772                         // not yet been triggered by writes; make sure $callback runs *after* any such writes.
2773                         $this->mTrxPreCommitCallbacks[] = [ $callback, $fname ];
2774                 } else {
2775                         // No transaction is active nor will start implicitly, so make one for this callback
2776                         $this->startAtomic( __METHOD__ );
2777                         try {
2778                                 call_user_func( $callback );
2779                                 $this->endAtomic( __METHOD__ );
2780                         } catch ( Exception $e ) {
2781                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2782                                 throw $e;
2783                         }
2784                 }
2785         }
2786
2787         final public function setTransactionListener( $name, callable $callback = null ) {
2788                 if ( $callback ) {
2789                         $this->mTrxRecurringCallbacks[$name] = $callback;
2790                 } else {
2791                         unset( $this->mTrxRecurringCallbacks[$name] );
2792                 }
2793         }
2794
2795         /**
2796          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
2797          *
2798          * This method should not be used outside of Database/LoadBalancer
2799          *
2800          * @param bool $suppress
2801          * @since 1.28
2802          */
2803         final public function setTrxEndCallbackSuppression( $suppress ) {
2804                 $this->mTrxEndCallbacksSuppressed = $suppress;
2805         }
2806
2807         /**
2808          * Actually run and consume any "on transaction idle/resolution" callbacks.
2809          *
2810          * This method should not be used outside of Database/LoadBalancer
2811          *
2812          * @param int $trigger IDatabase::TRIGGER_* constant
2813          * @since 1.20
2814          * @throws Exception
2815          */
2816         public function runOnTransactionIdleCallbacks( $trigger ) {
2817                 if ( $this->mTrxEndCallbacksSuppressed ) {
2818                         return;
2819                 }
2820
2821                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
2822                 /** @var Exception $e */
2823                 $e = null; // first exception
2824                 do { // callbacks may add callbacks :)
2825                         $callbacks = array_merge(
2826                                 $this->mTrxIdleCallbacks,
2827                                 $this->mTrxEndCallbacks // include "transaction resolution" callbacks
2828                         );
2829                         $this->mTrxIdleCallbacks = []; // consumed (and recursion guard)
2830                         $this->mTrxEndCallbacks = []; // consumed (recursion guard)
2831                         foreach ( $callbacks as $callback ) {
2832                                 try {
2833                                         list( $phpCallback ) = $callback;
2834                                         $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
2835                                         call_user_func_array( $phpCallback, [ $trigger ] );
2836                                         if ( $autoTrx ) {
2837                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
2838                                         } else {
2839                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
2840                                         }
2841                                 } catch ( Exception $ex ) {
2842                                         call_user_func( $this->errorLogger, $ex );
2843                                         $e = $e ?: $ex;
2844                                         // Some callbacks may use startAtomic/endAtomic, so make sure
2845                                         // their transactions are ended so other callbacks don't fail
2846                                         if ( $this->trxLevel() ) {
2847                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2848                                         }
2849                                 }
2850                         }
2851                 } while ( count( $this->mTrxIdleCallbacks ) );
2852
2853                 if ( $e instanceof Exception ) {
2854                         throw $e; // re-throw any first exception
2855                 }
2856         }
2857
2858         /**
2859          * Actually run and consume any "on transaction pre-commit" callbacks.
2860          *
2861          * This method should not be used outside of Database/LoadBalancer
2862          *
2863          * @since 1.22
2864          * @throws Exception
2865          */
2866         public function runOnTransactionPreCommitCallbacks() {
2867                 $e = null; // first exception
2868                 do { // callbacks may add callbacks :)
2869                         $callbacks = $this->mTrxPreCommitCallbacks;
2870                         $this->mTrxPreCommitCallbacks = []; // consumed (and recursion guard)
2871                         foreach ( $callbacks as $callback ) {
2872                                 try {
2873                                         list( $phpCallback ) = $callback;
2874                                         call_user_func( $phpCallback );
2875                                 } catch ( Exception $ex ) {
2876                                         call_user_func( $this->errorLogger, $ex );
2877                                         $e = $e ?: $ex;
2878                                 }
2879                         }
2880                 } while ( count( $this->mTrxPreCommitCallbacks ) );
2881
2882                 if ( $e instanceof Exception ) {
2883                         throw $e; // re-throw any first exception
2884                 }
2885         }
2886
2887         /**
2888          * Actually run any "transaction listener" callbacks.
2889          *
2890          * This method should not be used outside of Database/LoadBalancer
2891          *
2892          * @param int $trigger IDatabase::TRIGGER_* constant
2893          * @throws Exception
2894          * @since 1.20
2895          */
2896         public function runTransactionListenerCallbacks( $trigger ) {
2897                 if ( $this->mTrxEndCallbacksSuppressed ) {
2898                         return;
2899                 }
2900
2901                 /** @var Exception $e */
2902                 $e = null; // first exception
2903
2904                 foreach ( $this->mTrxRecurringCallbacks as $phpCallback ) {
2905                         try {
2906                                 $phpCallback( $trigger, $this );
2907                         } catch ( Exception $ex ) {
2908                                 call_user_func( $this->errorLogger, $ex );
2909                                 $e = $e ?: $ex;
2910                         }
2911                 }
2912
2913                 if ( $e instanceof Exception ) {
2914                         throw $e; // re-throw any first exception
2915                 }
2916         }
2917
2918         final public function startAtomic( $fname = __METHOD__ ) {
2919                 if ( !$this->mTrxLevel ) {
2920                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2921                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
2922                         // in all changes being in one transaction to keep requests transactional.
2923                         if ( !$this->getFlag( self::DBO_TRX ) ) {
2924                                 $this->mTrxAutomaticAtomic = true;
2925                         }
2926                 }
2927
2928                 $this->mTrxAtomicLevels[] = $fname;
2929         }
2930
2931         final public function endAtomic( $fname = __METHOD__ ) {
2932                 if ( !$this->mTrxLevel ) {
2933                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
2934                 }
2935                 if ( !$this->mTrxAtomicLevels ||
2936                         array_pop( $this->mTrxAtomicLevels ) !== $fname
2937                 ) {
2938                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
2939                 }
2940
2941                 if ( !$this->mTrxAtomicLevels && $this->mTrxAutomaticAtomic ) {
2942                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2943                 }
2944         }
2945
2946         final public function doAtomicSection( $fname, callable $callback ) {
2947                 $this->startAtomic( $fname );
2948                 try {
2949                         $res = call_user_func_array( $callback, [ $this, $fname ] );
2950                 } catch ( Exception $e ) {
2951                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2952                         throw $e;
2953                 }
2954                 $this->endAtomic( $fname );
2955
2956                 return $res;
2957         }
2958
2959         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
2960                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
2961                 if ( $this->mTrxLevel ) {
2962                         if ( $this->mTrxAtomicLevels ) {
2963                                 $levels = implode( ', ', $this->mTrxAtomicLevels );
2964                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
2965                                 throw new DBUnexpectedError( $this, $msg );
2966                         } elseif ( !$this->mTrxAutomatic ) {
2967                                 $msg = "$fname: Explicit transaction already active (from {$this->mTrxFname}).";
2968                                 throw new DBUnexpectedError( $this, $msg );
2969                         } else {
2970                                 // @TODO: make this an exception at some point
2971                                 $msg = "$fname: Implicit transaction already active (from {$this->mTrxFname}).";
2972                                 $this->queryLogger->error( $msg );
2973                                 return; // join the main transaction set
2974                         }
2975                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
2976                         // @TODO: make this an exception at some point
2977                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
2978                         $this->queryLogger->error( $msg );
2979                         return; // let any writes be in the main transaction
2980                 }
2981
2982                 // Avoid fatals if close() was called
2983                 $this->assertOpen();
2984
2985                 $this->doBegin( $fname );
2986                 $this->mTrxTimestamp = microtime( true );
2987                 $this->mTrxFname = $fname;
2988                 $this->mTrxDoneWrites = false;
2989                 $this->mTrxAutomaticAtomic = false;
2990                 $this->mTrxAtomicLevels = [];
2991                 $this->mTrxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
2992                 $this->mTrxWriteDuration = 0.0;
2993                 $this->mTrxWriteQueryCount = 0;
2994                 $this->mTrxWriteAffectedRows = 0;
2995                 $this->mTrxWriteAdjDuration = 0.0;
2996                 $this->mTrxWriteAdjQueryCount = 0;
2997                 $this->mTrxWriteCallers = [];
2998                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
2999                 // Get an estimate of the replica DB lag before then, treating estimate staleness
3000                 // as lag itself just to be safe
3001                 $status = $this->getApproximateLagStatus();
3002                 $this->mTrxReplicaLag = $status['lag'] + ( microtime( true ) - $status['since'] );
3003                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
3004                 // caller will think its OK to muck around with the transaction just because startAtomic()
3005                 // has not yet completed (e.g. setting mTrxAtomicLevels).
3006                 $this->mTrxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
3007         }
3008
3009         /**
3010          * Issues the BEGIN command to the database server.
3011          *
3012          * @see Database::begin()
3013          * @param string $fname
3014          */
3015         protected function doBegin( $fname ) {
3016                 $this->query( 'BEGIN', $fname );
3017                 $this->mTrxLevel = 1;
3018         }
3019
3020         final public function commit( $fname = __METHOD__, $flush = '' ) {
3021                 if ( $this->mTrxLevel && $this->mTrxAtomicLevels ) {
3022                         // There are still atomic sections open. This cannot be ignored
3023                         $levels = implode( ', ', $this->mTrxAtomicLevels );
3024                         throw new DBUnexpectedError(
3025                                 $this,
3026                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3027                         );
3028                 }
3029
3030                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3031                         if ( !$this->mTrxLevel ) {
3032                                 return; // nothing to do
3033                         } elseif ( !$this->mTrxAutomatic ) {
3034                                 throw new DBUnexpectedError(
3035                                         $this,
3036                                         "$fname: Flushing an explicit transaction, getting out of sync."
3037                                 );
3038                         }
3039                 } else {
3040                         if ( !$this->mTrxLevel ) {
3041                                 $this->queryLogger->error(
3042                                         "$fname: No transaction to commit, something got out of sync." );
3043                                 return; // nothing to do
3044                         } elseif ( $this->mTrxAutomatic ) {
3045                                 // @TODO: make this an exception at some point
3046                                 $msg = "$fname: Explicit commit of implicit transaction.";
3047                                 $this->queryLogger->error( $msg );
3048                                 return; // wait for the main transaction set commit round
3049                         }
3050                 }
3051
3052                 // Avoid fatals if close() was called
3053                 $this->assertOpen();
3054
3055                 $this->runOnTransactionPreCommitCallbacks();
3056                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3057                 $this->doCommit( $fname );
3058                 if ( $this->mTrxDoneWrites ) {
3059                         $this->mLastWriteTime = microtime( true );
3060                         $this->trxProfiler->transactionWritingOut(
3061                                 $this->mServer,
3062                                 $this->mDBname,
3063                                 $this->mTrxShortId,
3064                                 $writeTime,
3065                                 $this->mTrxWriteAffectedRows
3066                         );
3067                 }
3068
3069                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3070                 $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3071         }
3072
3073         /**
3074          * Issues the COMMIT command to the database server.
3075          *
3076          * @see Database::commit()
3077          * @param string $fname
3078          */
3079         protected function doCommit( $fname ) {
3080                 if ( $this->mTrxLevel ) {
3081                         $this->query( 'COMMIT', $fname );
3082                         $this->mTrxLevel = 0;
3083                 }
3084         }
3085
3086         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3087                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3088                         if ( !$this->mTrxLevel ) {
3089                                 return; // nothing to do
3090                         }
3091                 } else {
3092                         if ( !$this->mTrxLevel ) {
3093                                 $this->queryLogger->error(
3094                                         "$fname: No transaction to rollback, something got out of sync." );
3095                                 return; // nothing to do
3096                         } elseif ( $this->getFlag( self::DBO_TRX ) ) {
3097                                 throw new DBUnexpectedError(
3098                                         $this,
3099                                         "$fname: Expected mass rollback of all peer databases (DBO_TRX set)."
3100                                 );
3101                         }
3102                 }
3103
3104                 // Avoid fatals if close() was called
3105                 $this->assertOpen();
3106
3107                 $this->doRollback( $fname );
3108                 $this->mTrxAtomicLevels = [];
3109                 if ( $this->mTrxDoneWrites ) {
3110                         $this->trxProfiler->transactionWritingOut(
3111                                 $this->mServer,
3112                                 $this->mDBname,
3113                                 $this->mTrxShortId
3114                         );
3115                 }
3116
3117                 $this->mTrxIdleCallbacks = []; // clear
3118                 $this->mTrxPreCommitCallbacks = []; // clear
3119                 try {
3120                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
3121                 } catch ( Exception $e ) {
3122                         // already logged; finish and let LoadBalancer move on during mass-rollback
3123                 }
3124                 try {
3125                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
3126                 } catch ( Exception $e ) {
3127                         // already logged; let LoadBalancer move on during mass-rollback
3128                 }
3129         }
3130
3131         /**
3132          * Issues the ROLLBACK command to the database server.
3133          *
3134          * @see Database::rollback()
3135          * @param string $fname
3136          */
3137         protected function doRollback( $fname ) {
3138                 if ( $this->mTrxLevel ) {
3139                         # Disconnects cause rollback anyway, so ignore those errors
3140                         $ignoreErrors = true;
3141                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
3142                         $this->mTrxLevel = 0;
3143                 }
3144         }
3145
3146         public function flushSnapshot( $fname = __METHOD__ ) {
3147                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
3148                         // This only flushes transactions to clear snapshots, not to write data
3149                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3150                         throw new DBUnexpectedError(
3151                                 $this,
3152                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
3153                         );
3154                 }
3155
3156                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3157         }
3158
3159         public function explicitTrxActive() {
3160                 return $this->mTrxLevel && ( $this->mTrxAtomicLevels || !$this->mTrxAutomatic );
3161         }
3162
3163         public function duplicateTableStructure(
3164                 $oldName, $newName, $temporary = false, $fname = __METHOD__
3165         ) {
3166                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3167         }
3168
3169         public function listTables( $prefix = null, $fname = __METHOD__ ) {
3170                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3171         }
3172
3173         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3174                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3175         }
3176
3177         public function timestamp( $ts = 0 ) {
3178                 $t = new ConvertibleTimestamp( $ts );
3179                 // Let errors bubble up to avoid putting garbage in the DB
3180                 return $t->getTimestamp( TS_MW );
3181         }
3182
3183         public function timestampOrNull( $ts = null ) {
3184                 if ( is_null( $ts ) ) {
3185                         return null;
3186                 } else {
3187                         return $this->timestamp( $ts );
3188                 }
3189         }
3190
3191         /**
3192          * Take the result from a query, and wrap it in a ResultWrapper if
3193          * necessary. Boolean values are passed through as is, to indicate success
3194          * of write queries or failure.
3195          *
3196          * Once upon a time, Database::query() returned a bare MySQL result
3197          * resource, and it was necessary to call this function to convert it to
3198          * a wrapper. Nowadays, raw database objects are never exposed to external
3199          * callers, so this is unnecessary in external code.
3200          *
3201          * @param bool|ResultWrapper|resource|object $result
3202          * @return bool|ResultWrapper
3203          */
3204         protected function resultObject( $result ) {
3205                 if ( !$result ) {
3206                         return false;
3207                 } elseif ( $result instanceof ResultWrapper ) {
3208                         return $result;
3209                 } elseif ( $result === true ) {
3210                         // Successful write query
3211                         return $result;
3212                 } else {
3213                         return new ResultWrapper( $this, $result );
3214                 }
3215         }
3216
3217         public function ping( &$rtt = null ) {
3218                 // Avoid hitting the server if it was hit recently
3219                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
3220                         if ( !func_num_args() || $this->mRTTEstimate > 0 ) {
3221                                 $rtt = $this->mRTTEstimate;
3222                                 return true; // don't care about $rtt
3223                         }
3224                 }
3225
3226                 // This will reconnect if possible or return false if not
3227                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
3228                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
3229                 $this->restoreFlags( self::RESTORE_PRIOR );
3230
3231                 if ( $ok ) {
3232                         $rtt = $this->mRTTEstimate;
3233                 }
3234
3235                 return $ok;
3236         }
3237
3238         /**
3239          * Close existing database connection and open a new connection
3240          *
3241          * @return bool True if new connection is opened successfully, false if error
3242          */
3243         protected function reconnect() {
3244                 $this->closeConnection();
3245                 $this->mOpened = false;
3246                 $this->mConn = false;
3247                 try {
3248                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3249                         $this->lastPing = microtime( true );
3250                         $ok = true;
3251                 } catch ( DBConnectionError $e ) {
3252                         $ok = false;
3253                 }
3254
3255                 return $ok;
3256         }
3257
3258         public function getSessionLagStatus() {
3259                 return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
3260         }
3261
3262         /**
3263          * Get the replica DB lag when the current transaction started
3264          *
3265          * This is useful when transactions might use snapshot isolation
3266          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
3267          * is this lag plus transaction duration. If they don't, it is still
3268          * safe to be pessimistic. This returns null if there is no transaction.
3269          *
3270          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
3271          * @since 1.27
3272          */
3273         protected function getTransactionLagStatus() {
3274                 return $this->mTrxLevel
3275                         ? [ 'lag' => $this->mTrxReplicaLag, 'since' => $this->trxTimestamp() ]
3276                         : null;
3277         }
3278
3279         /**
3280          * Get a replica DB lag estimate for this server
3281          *
3282          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
3283          * @since 1.27
3284          */
3285         protected function getApproximateLagStatus() {
3286                 return [
3287                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
3288                         'since' => microtime( true )
3289                 ];
3290         }
3291
3292         /**
3293          * Merge the result of getSessionLagStatus() for several DBs
3294          * using the most pessimistic values to estimate the lag of
3295          * any data derived from them in combination
3296          *
3297          * This is information is useful for caching modules
3298          *
3299          * @see WANObjectCache::set()
3300          * @see WANObjectCache::getWithSetCallback()
3301          *
3302          * @param IDatabase $db1
3303          * @param IDatabase $db2 [optional]
3304          * @return array Map of values:
3305          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3306          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3307          *   - pending: whether any of the DBs have uncommitted changes
3308          * @throws DBError
3309          * @since 1.27
3310          */
3311         public static function getCacheSetOptions( IDatabase $db1, IDatabase $db2 = null ) {
3312                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3313                 foreach ( func_get_args() as $db ) {
3314                         /** @var IDatabase $db */
3315                         $status = $db->getSessionLagStatus();
3316                         if ( $status['lag'] === false ) {
3317                                 $res['lag'] = false;
3318                         } elseif ( $res['lag'] !== false ) {
3319                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3320                         }
3321                         $res['since'] = min( $res['since'], $status['since'] );
3322                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3323                 }
3324
3325                 return $res;
3326         }
3327
3328         public function getLag() {
3329                 return 0;
3330         }
3331
3332         public function maxListLen() {
3333                 return 0;
3334         }
3335
3336         public function encodeBlob( $b ) {
3337                 return $b;
3338         }
3339
3340         public function decodeBlob( $b ) {
3341                 if ( $b instanceof Blob ) {
3342                         $b = $b->fetch();
3343                 }
3344                 return $b;
3345         }
3346
3347         public function setSessionOptions( array $options ) {
3348         }
3349
3350         public function sourceFile(
3351                 $filename,
3352                 callable $lineCallback = null,
3353                 callable $resultCallback = null,
3354                 $fname = false,
3355                 callable $inputCallback = null
3356         ) {
3357                 MediaWiki\suppressWarnings();
3358                 $fp = fopen( $filename, 'r' );
3359                 MediaWiki\restoreWarnings();
3360
3361                 if ( false === $fp ) {
3362                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
3363                 }
3364
3365                 if ( !$fname ) {
3366                         $fname = __METHOD__ . "( $filename )";
3367                 }
3368
3369                 try {
3370                         $error = $this->sourceStream(
3371                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3372                 } catch ( Exception $e ) {
3373                         fclose( $fp );
3374                         throw $e;
3375                 }
3376
3377                 fclose( $fp );
3378
3379                 return $error;
3380         }
3381
3382         public function setSchemaVars( $vars ) {
3383                 $this->mSchemaVars = $vars;
3384         }
3385
3386         public function sourceStream(
3387                 $fp,
3388                 callable $lineCallback = null,
3389                 callable $resultCallback = null,
3390                 $fname = __METHOD__,
3391                 callable $inputCallback = null
3392         ) {
3393                 $cmd = '';
3394
3395                 while ( !feof( $fp ) ) {
3396                         if ( $lineCallback ) {
3397                                 call_user_func( $lineCallback );
3398                         }
3399
3400                         $line = trim( fgets( $fp ) );
3401
3402                         if ( $line == '' ) {
3403                                 continue;
3404                         }
3405
3406                         if ( '-' == $line[0] && '-' == $line[1] ) {
3407                                 continue;
3408                         }
3409
3410                         if ( $cmd != '' ) {
3411                                 $cmd .= ' ';
3412                         }
3413
3414                         $done = $this->streamStatementEnd( $cmd, $line );
3415
3416                         $cmd .= "$line\n";
3417
3418                         if ( $done || feof( $fp ) ) {
3419                                 $cmd = $this->replaceVars( $cmd );
3420
3421                                 if ( !$inputCallback || call_user_func( $inputCallback, $cmd ) ) {
3422                                         $res = $this->query( $cmd, $fname );
3423
3424                                         if ( $resultCallback ) {
3425                                                 call_user_func( $resultCallback, $res, $this );
3426                                         }
3427
3428                                         if ( false === $res ) {
3429                                                 $err = $this->lastError();
3430
3431                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3432                                         }
3433                                 }
3434                                 $cmd = '';
3435                         }
3436                 }
3437
3438                 return true;
3439         }
3440
3441         /**
3442          * Called by sourceStream() to check if we've reached a statement end
3443          *
3444          * @param string &$sql SQL assembled so far
3445          * @param string &$newLine New line about to be added to $sql
3446          * @return bool Whether $newLine contains end of the statement
3447          */
3448         public function streamStatementEnd( &$sql, &$newLine ) {
3449                 if ( $this->delimiter ) {
3450                         $prev = $newLine;
3451                         $newLine = preg_replace(
3452                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3453                         if ( $newLine != $prev ) {
3454                                 return true;
3455                         }
3456                 }
3457
3458                 return false;
3459         }
3460
3461         /**
3462          * Database independent variable replacement. Replaces a set of variables
3463          * in an SQL statement with their contents as given by $this->getSchemaVars().
3464          *
3465          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3466          *
3467          * - '{$var}' should be used for text and is passed through the database's
3468          *   addQuotes method.
3469          * - `{$var}` should be used for identifiers (e.g. table and database names).
3470          *   It is passed through the database's addIdentifierQuotes method which
3471          *   can be overridden if the database uses something other than backticks.
3472          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
3473          *   database's tableName method.
3474          * - / *i* / passes the name that follows through the database's indexName method.
3475          * - In all other cases, / *$var* / is left unencoded. Except for table options,
3476          *   its use should be avoided. In 1.24 and older, string encoding was applied.
3477          *
3478          * @param string $ins SQL statement to replace variables in
3479          * @return string The new SQL statement with variables replaced
3480          */
3481         protected function replaceVars( $ins ) {
3482                 $vars = $this->getSchemaVars();
3483                 return preg_replace_callback(
3484                         '!
3485                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
3486                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
3487                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
3488                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
3489                         !x',
3490                         function ( $m ) use ( $vars ) {
3491                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
3492                                 // check for both nonexistent keys *and* the empty string.
3493                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
3494                                         if ( $m[1] === 'i' ) {
3495                                                 return $this->indexName( $m[2] );
3496                                         } else {
3497                                                 return $this->tableName( $m[2] );
3498                                         }
3499                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
3500                                         return $this->addQuotes( $vars[$m[3]] );
3501                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
3502                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
3503                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
3504                                         return $vars[$m[5]];
3505                                 } else {
3506                                         return $m[0];
3507                                 }
3508                         },
3509                         $ins
3510                 );
3511         }
3512
3513         /**
3514          * Get schema variables. If none have been set via setSchemaVars(), then
3515          * use some defaults from the current object.
3516          *
3517          * @return array
3518          */
3519         protected function getSchemaVars() {
3520                 if ( $this->mSchemaVars ) {
3521                         return $this->mSchemaVars;
3522                 } else {
3523                         return $this->getDefaultSchemaVars();
3524                 }
3525         }
3526
3527         /**
3528          * Get schema variables to use if none have been set via setSchemaVars().
3529          *
3530          * Override this in derived classes to provide variables for tables.sql
3531          * and SQL patch files.
3532          *
3533          * @return array
3534          */
3535         protected function getDefaultSchemaVars() {
3536                 return [];
3537         }
3538
3539         public function lockIsFree( $lockName, $method ) {
3540                 return true;
3541         }
3542
3543         public function lock( $lockName, $method, $timeout = 5 ) {
3544                 $this->mNamedLocksHeld[$lockName] = 1;
3545
3546                 return true;
3547         }
3548
3549         public function unlock( $lockName, $method ) {
3550                 unset( $this->mNamedLocksHeld[$lockName] );
3551
3552                 return true;
3553         }
3554
3555         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
3556                 if ( $this->writesOrCallbacksPending() ) {
3557                         // This only flushes transactions to clear snapshots, not to write data
3558                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3559                         throw new DBUnexpectedError(
3560                                 $this,
3561                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
3562                         );
3563                 }
3564
3565                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
3566                         return null;
3567                 }
3568
3569                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
3570                         if ( $this->trxLevel() ) {
3571                                 // There is a good chance an exception was thrown, causing any early return
3572                                 // from the caller. Let any error handler get a chance to issue rollback().
3573                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
3574                                 $this->onTransactionResolution(
3575                                         function () use ( $lockKey, $fname ) {
3576                                                 $this->unlock( $lockKey, $fname );
3577                                         },
3578                                         $fname
3579                                 );
3580                         } else {
3581                                 $this->unlock( $lockKey, $fname );
3582                         }
3583                 } );
3584
3585                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3586
3587                 return $unlocker;
3588         }
3589
3590         public function namedLocksEnqueue() {
3591                 return false;
3592         }
3593
3594         public function tableLocksHaveTransactionScope() {
3595                 return true;
3596         }
3597
3598         final public function lockTables( array $read, array $write, $method ) {
3599                 if ( $this->writesOrCallbacksPending() ) {
3600                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
3601                 }
3602
3603                 if ( $this->tableLocksHaveTransactionScope() ) {
3604                         $this->startAtomic( $method );
3605                 }
3606
3607                 return $this->doLockTables( $read, $write, $method );
3608         }
3609
3610         /**
3611          * Helper function for lockTables() that handles the actual table locking
3612          *
3613          * @param array $read Array of tables to lock for read access
3614          * @param array $write Array of tables to lock for write access
3615          * @param string $method Name of caller
3616          * @return true
3617          */
3618         protected function doLockTables( array $read, array $write, $method ) {
3619                 return true;
3620         }
3621
3622         final public function unlockTables( $method ) {
3623                 if ( $this->tableLocksHaveTransactionScope() ) {
3624                         $this->endAtomic( $method );
3625
3626                         return true; // locks released on COMMIT/ROLLBACK
3627                 }
3628
3629                 return $this->doUnlockTables( $method );
3630         }
3631
3632         /**
3633          * Helper function for unlockTables() that handles the actual table unlocking
3634          *
3635          * @param string $method Name of caller
3636          * @return true
3637          */
3638         protected function doUnlockTables( $method ) {
3639                 return true;
3640         }
3641
3642         /**
3643          * Delete a table
3644          * @param string $tableName
3645          * @param string $fName
3646          * @return bool|ResultWrapper
3647          * @since 1.18
3648          */
3649         public function dropTable( $tableName, $fName = __METHOD__ ) {
3650                 if ( !$this->tableExists( $tableName, $fName ) ) {
3651                         return false;
3652                 }
3653                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
3654
3655                 return $this->query( $sql, $fName );
3656         }
3657
3658         public function getInfinity() {
3659                 return 'infinity';
3660         }
3661
3662         public function encodeExpiry( $expiry ) {
3663                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3664                         ? $this->getInfinity()
3665                         : $this->timestamp( $expiry );
3666         }
3667
3668         public function decodeExpiry( $expiry, $format = TS_MW ) {
3669                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
3670                         return 'infinity';
3671                 }
3672
3673                 return ConvertibleTimestamp::convert( $format, $expiry );
3674         }
3675
3676         public function setBigSelects( $value = true ) {
3677                 // no-op
3678         }
3679
3680         public function isReadOnly() {
3681                 return ( $this->getReadOnlyReason() !== false );
3682         }
3683
3684         /**
3685          * @return string|bool Reason this DB is read-only or false if it is not
3686          */
3687         protected function getReadOnlyReason() {
3688                 $reason = $this->getLBInfo( 'readOnlyReason' );
3689
3690                 return is_string( $reason ) ? $reason : false;
3691         }
3692
3693         public function setTableAliases( array $aliases ) {
3694                 $this->tableAliases = $aliases;
3695         }
3696
3697         /**
3698          * @return bool Whether a DB user is required to access the DB
3699          * @since 1.28
3700          */
3701         protected function requiresDatabaseUser() {
3702                 return true;
3703         }
3704
3705         /**
3706          * Get the underlying binding handle, mConn
3707          *
3708          * Makes sure that mConn is set (disconnects and ping() failure can unset it).
3709          * This catches broken callers than catch and ignore disconnection exceptions.
3710          * Unlike checking isOpen(), this is safe to call inside of open().
3711          *
3712          * @return resource|object
3713          * @throws DBUnexpectedError
3714          * @since 1.26
3715          */
3716         protected function getBindingHandle() {
3717                 if ( !$this->mConn ) {
3718                         throw new DBUnexpectedError(
3719                                 $this,
3720                                 'DB connection was already closed or the connection dropped.'
3721                         );
3722                 }
3723
3724                 return $this->mConn;
3725         }
3726
3727         /**
3728          * @since 1.19
3729          * @return string
3730          */
3731         public function __toString() {
3732                 return (string)$this->mConn;
3733         }
3734
3735         /**
3736          * Make sure that copies do not share the same client binding handle
3737          * @throws DBConnectionError
3738          */
3739         public function __clone() {
3740                 $this->connLogger->warning(
3741                         "Cloning " . static::class . " is not recomended; forking connection:\n" .
3742                         ( new RuntimeException() )->getTraceAsString()
3743                 );
3744
3745                 if ( $this->isOpen() ) {
3746                         // Open a new connection resource without messing with the old one
3747                         $this->mOpened = false;
3748                         $this->mConn = false;
3749                         $this->mTrxEndCallbacks = []; // don't copy
3750                         $this->handleSessionLoss(); // no trx or locks anymore
3751                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3752                         $this->lastPing = microtime( true );
3753                 }
3754         }
3755
3756         /**
3757          * Called by serialize. Throw an exception when DB connection is serialized.
3758          * This causes problems on some database engines because the connection is
3759          * not restored on unserialize.
3760          */
3761         public function __sleep() {
3762                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
3763                         'the connection is not restored on wakeup.' );
3764         }
3765
3766         /**
3767          * Run a few simple sanity checks and close dangling connections
3768          */
3769         public function __destruct() {
3770                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
3771                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
3772                 }
3773
3774                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
3775                 if ( $danglingWriters ) {
3776                         $fnames = implode( ', ', $danglingWriters );
3777                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
3778                 }
3779
3780                 if ( $this->mConn ) {
3781                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
3782                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
3783                         \MediaWiki\suppressWarnings();
3784                         $this->closeConnection();
3785                         \MediaWiki\restoreWarnings();
3786                         $this->mConn = false;
3787                         $this->mOpened = false;
3788                 }
3789         }
3790 }
3791
3792 class_alias( Database::class, 'DatabaseBase' ); // b/c for old name
3793 class_alias( Database::class, 'Database' ); // b/c global alias