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 Psr\Log\NullLogger;
  31 use Wikimedia\ScopedCallback;
  32 use Wikimedia\Timestamp\ConvertibleTimestamp;
  33 use Wikimedia;
  34 use BagOStuff;
  35 use HashBagOStuff;
  36 use InvalidArgumentException;
  37 use Exception;
  38 use RuntimeException;
  39
  40 /**
  41  * Relational database abstraction object
  42  *
  43  * @ingroup Database
  44  * @since 1.28
  45  */
  46 abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAwareInterface {
  47         /** Number of times to re-try an operation in case of deadlock */
  48         const DEADLOCK_TRIES = 4;
  49         /** Minimum time to wait before retry, in microseconds */
  50         const DEADLOCK_DELAY_MIN = 500000;
  51         /** Maximum time to wait before retry */
  52         const DEADLOCK_DELAY_MAX = 1500000;
  53
  54         /** How long before it is worth doing a dummy query to test the connection */
  55         const PING_TTL = 1.0;
  56         const PING_QUERY = 'SELECT 1 AS ping';
  57
  58         const TINY_WRITE_SEC = 0.010;
  59         const SLOW_WRITE_SEC = 0.500;
  60         const SMALL_WRITE_ROWS = 100;
  61
  62         /** @var string Whether lock granularity is on the level of the entire database */
  63         const ATTR_DB_LEVEL_LOCKING = 'db-level-locking';
  64
  65         /** @var string SQL query */
  66         protected $lastQuery = '';
  67         /** @var float|bool UNIX timestamp of last write query */
  68         protected $lastWriteTime = false;
  69         /** @var string|bool */
  70         protected $phpError = false;
  71         /** @var string */
  72         protected $server;
  73         /** @var string */
  74         protected $user;
  75         /** @var string */
  76         protected $password;
  77         /** @var string */
  78         protected $dbName;
  79         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  80         protected $tableAliases = [];
  81         /** @var bool Whether this PHP instance is for a CLI script */
  82         protected $cliMode;
  83         /** @var string Agent name for query profiling */
  84         protected $agent;
  85
  86         /** @var BagOStuff APC cache */
  87         protected $srvCache;
  88         /** @var LoggerInterface */
  89         protected $connLogger;
  90         /** @var LoggerInterface */
  91         protected $queryLogger;
  92         /** @var callback Error logging callback */
  93         protected $errorLogger;
  94
  95         /** @var resource|null Database connection */
  96         protected $conn = null;
  97         /** @var bool */
  98         protected $opened = false;
  99
 100         /** @var array[] List of (callable, method name) */
 101         protected $trxIdleCallbacks = [];
 102         /** @var array[] List of (callable, method name) */
 103         protected $trxPreCommitCallbacks = [];
 104         /** @var array[] List of (callable, method name) */
 105         protected $trxEndCallbacks = [];
 106         /** @var callable[] Map of (name => callable) */
 107         protected $trxRecurringCallbacks = [];
 108         /** @var bool Whether to suppress triggering of transaction end callbacks */
 109         protected $trxEndCallbacksSuppressed = false;
 110
 111         /** @var string */
 112         protected $tablePrefix = '';
 113         /** @var string */
 114         protected $schema = '';
 115         /** @var int */
 116         protected $flags;
 117         /** @var array */
 118         protected $lbInfo = [];
 119         /** @var array|bool */
 120         protected $schemaVars = false;
 121         /** @var array */
 122         protected $sessionVars = [];
 123         /** @var array|null */
 124         protected $preparedArgs;
 125         /** @var string|bool|null Stashed value of html_errors INI setting */
 126         protected $htmlErrors;
 127         /** @var string */
 128         protected $delimiter = ';';
 129         /** @var DatabaseDomain */
 130         protected $currentDomain;
 131         /** @var integer|null Rows affected by the last query to query() or its CRUD wrappers */
 132         protected $affectedRowCount;
 133
 134         /**
 135          * Either 1 if a transaction is active or 0 otherwise.
 136          * The other Trx fields may not be meaningfull if this is 0.
 137          *
 138          * @var int
 139          */
 140         protected $trxLevel = 0;
 141         /**
 142          * Either a short hexidecimal string if a transaction is active or ""
 143          *
 144          * @var string
 145          * @see Database::trxLevel
 146          */
 147         protected $trxShortId = '';
 148         /**
 149          * The UNIX time that the transaction started. Callers can assume that if
 150          * snapshot isolation is used, then the data is *at least* up to date to that
 151          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 152          *
 153          * @var float|null
 154          * @see Database::trxLevel
 155          */
 156         private $trxTimestamp = null;
 157         /** @var float Lag estimate at the time of BEGIN */
 158         private $trxReplicaLag = null;
 159         /**
 160          * Remembers the function name given for starting the most recent transaction via begin().
 161          * Used to provide additional context for error reporting.
 162          *
 163          * @var string
 164          * @see Database::trxLevel
 165          */
 166         private $trxFname = null;
 167         /**
 168          * Record if possible write queries were done in the last transaction started
 169          *
 170          * @var bool
 171          * @see Database::trxLevel
 172          */
 173         private $trxDoneWrites = false;
 174         /**
 175          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 176          *
 177          * @var bool
 178          * @see Database::trxLevel
 179          */
 180         private $trxAutomatic = false;
 181         /**
 182          * Array of levels of atomicity within transactions
 183          *
 184          * @var array
 185          */
 186         private $trxAtomicLevels = [];
 187         /**
 188          * Record if the current transaction was started implicitly by Database::startAtomic
 189          *
 190          * @var bool
 191          */
 192         private $trxAutomaticAtomic = false;
 193         /**
 194          * Track the write query callers of the current transaction
 195          *
 196          * @var string[]
 197          */
 198         private $trxWriteCallers = [];
 199         /**
 200          * @var float Seconds spent in write queries for the current transaction
 201          */
 202         private $trxWriteDuration = 0.0;
 203         /**
 204          * @var int Number of write queries for the current transaction
 205          */
 206         private $trxWriteQueryCount = 0;
 207         /**
 208          * @var int Number of rows affected by write queries for the current transaction
 209          */
 210         private $trxWriteAffectedRows = 0;
 211         /**
 212          * @var float Like trxWriteQueryCount but excludes lock-bound, easy to replicate, queries
 213          */
 214         private $trxWriteAdjDuration = 0.0;
 215         /**
 216          * @var int Number of write queries counted in trxWriteAdjDuration
 217          */
 218         private $trxWriteAdjQueryCount = 0;
 219         /**
 220          * @var float RTT time estimate
 221          */
 222         private $rttEstimate = 0.0;
 223
 224         /** @var array Map of (name => 1) for locks obtained via lock() */
 225         private $namedLocksHeld = [];
 226         /** @var array Map of (table name => 1) for TEMPORARY tables */
 227         protected $sessionTempTables = [];
 228
 229         /** @var IDatabase|null Lazy handle to the master DB this server replicates from */
 230         private $lazyMasterHandle;
 231
 232         /** @var float UNIX timestamp */
 233         protected $lastPing = 0.0;
 234
 235         /** @var int[] Prior flags member variable values */
 236         private $priorFlags = [];
 237
 238         /** @var object|string Class name or object With profileIn/profileOut methods */
 239         protected $profiler;
 240         /** @var TransactionProfiler */
 241         protected $trxProfiler;
 242
 243         /** @var int */
 244         protected $nonNativeInsertSelectBatchSize = 10000;
 245
 246         /**
 247          * Constructor and database handle and attempt to connect to the DB server
 248          *
 249          * IDatabase classes should not be constructed directly in external
 250          * code. Database::factory() should be used instead.
 251          *
 252          * @param array $params Parameters passed from Database::factory()
 253          */
 254         function __construct( array $params ) {
 255                 $server = $params['host'];
 256                 $user = $params['user'];
 257                 $password = $params['password'];
 258                 $dbName = $params['dbname'];
 259
 260                 $this->schema = $params['schema'];
 261                 $this->tablePrefix = $params['tablePrefix'];
 262
 263                 $this->cliMode = $params['cliMode'];
 264                 // Agent name is added to SQL queries in a comment, so make sure it can't break out
 265                 $this->agent = str_replace( '/', '-', $params['agent'] );
 266
 267                 $this->flags = $params['flags'];
 268                 if ( $this->flags & self::DBO_DEFAULT ) {
 269                         if ( $this->cliMode ) {
 270                                 $this->flags &= ~self::DBO_TRX;
 271                         } else {
 272                                 $this->flags |= self::DBO_TRX;
 273                         }
 274                 }
 275
 276                 $this->sessionVars = $params['variables'];
 277
 278                 $this->srvCache = isset( $params['srvCache'] )
 279                         ? $params['srvCache']
 280                         : new HashBagOStuff();
 281
 282                 $this->profiler = $params['profiler'];
 283                 $this->trxProfiler = $params['trxProfiler'];
 284                 $this->connLogger = $params['connLogger'];
 285                 $this->queryLogger = $params['queryLogger'];
 286                 $this->errorLogger = $params['errorLogger'];
 287
 288                 if ( isset( $params['nonNativeInsertSelectBatchSize'] ) ) {
 289                         $this->nonNativeInsertSelectBatchSize = $params['nonNativeInsertSelectBatchSize'];
 290                 }
 291
 292                 // Set initial dummy domain until open() sets the final DB/prefix
 293                 $this->currentDomain = DatabaseDomain::newUnspecified();
 294
 295                 if ( $user ) {
 296                         $this->open( $server, $user, $password, $dbName );
 297                 } elseif ( $this->requiresDatabaseUser() ) {
 298                         throw new InvalidArgumentException( "No database user provided." );
 299                 }
 300
 301                 // Set the domain object after open() sets the relevant fields
 302                 if ( $this->dbName != '' ) {
 303                         // Domains with server scope but a table prefix are not used by IDatabase classes
 304                         $this->currentDomain = new DatabaseDomain( $this->dbName, null, $this->tablePrefix );
 305                 }
 306         }
 307
 308         /**
 309          * Construct a Database subclass instance given a database type and parameters
 310          *
 311          * This also connects to the database immediately upon object construction
 312          *
 313          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 314          * @param array $p Parameter map with keys:
 315          *   - host : The hostname of the DB server
 316          *   - user : The name of the database user the client operates under
 317          *   - password : The password for the database user
 318          *   - dbname : The name of the database to use where queries do not specify one.
 319          *      The database must exist or an error might be thrown. Setting this to the empty string
 320          *      will avoid any such errors and make the handle have no implicit database scope. This is
 321          *      useful for queries like SHOW STATUS, CREATE DATABASE, or DROP DATABASE. Note that a
 322          *      "database" in Postgres is rougly equivalent to an entire MySQL server. This the domain
 323          *      in which user names and such are defined, e.g. users are database-specific in Postgres.
 324          *   - schema : The database schema to use (if supported). A "schema" in Postgres is roughly
 325          *      equivalent to a "database" in MySQL. Note that MySQL and SQLite do not use schemas.
 326          *   - tablePrefix : Optional table prefix that is implicitly added on to all table names
 327          *      recognized in queries. This can be used in place of schemas for handle site farms.
 328          *   - flags : Optional bitfield of DBO_* constants that define connection, protocol,
 329          *      buffering, and transaction behavior. It is STRONGLY adviced to leave the DBO_DEFAULT
 330          *      flag in place UNLESS this this database simply acts as a key/value store.
 331          *   - driver: Optional name of a specific DB client driver. For MySQL, there is only the
 332          *      'mysqli' driver; the old one 'mysql' has been removed.
 333          *   - variables: Optional map of session variables to set after connecting. This can be
 334          *      used to adjust lock timeouts or encoding modes and the like.
 335          *   - connLogger: Optional PSR-3 logger interface instance.
 336          *   - queryLogger: Optional PSR-3 logger interface instance.
 337          *   - profiler: Optional class name or object with profileIn()/profileOut() methods.
 338          *      These will be called in query(), using a simplified version of the SQL that also
 339          *      includes the agent as a SQL comment.
 340          *   - trxProfiler: Optional TransactionProfiler instance.
 341          *   - errorLogger: Optional callback that takes an Exception and logs it.
 342          *   - cliMode: Whether to consider the execution context that of a CLI script.
 343          *   - agent: Optional name used to identify the end-user in query profiling/logging.
 344          *   - srvCache: Optional BagOStuff instance to an APC-style cache.
 345          *   - nonNativeInsertSelectBatchSize: Optional batch size for non-native INSERT SELECT emulation.
 346          * @return Database|null If the database driver or extension cannot be found
 347          * @throws InvalidArgumentException If the database driver or extension cannot be found
 348          * @since 1.18
 349          */
 350         final public static function factory( $dbType, $p = [] ) {
 351                 $class = self::getClass( $dbType, isset( $p['driver'] ) ? $p['driver'] : null );
 352
 353                 if ( class_exists( $class ) && is_subclass_of( $class, IDatabase::class ) ) {
 354                         // Resolve some defaults for b/c
 355                         $p['host'] = isset( $p['host'] ) ? $p['host'] : false;
 356                         $p['user'] = isset( $p['user'] ) ? $p['user'] : false;
 357                         $p['password'] = isset( $p['password'] ) ? $p['password'] : false;
 358                         $p['dbname'] = isset( $p['dbname'] ) ? $p['dbname'] : false;
 359                         $p['flags'] = isset( $p['flags'] ) ? $p['flags'] : 0;
 360                         $p['variables'] = isset( $p['variables'] ) ? $p['variables'] : [];
 361                         $p['tablePrefix'] = isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : '';
 362                         $p['schema'] = isset( $p['schema'] ) ? $p['schema'] : '';
 363                         $p['cliMode'] = isset( $p['cliMode'] )
 364                                 ? $p['cliMode']
 365                                 : ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 366                         $p['agent'] = isset( $p['agent'] ) ? $p['agent'] : '';
 367                         if ( !isset( $p['connLogger'] ) ) {
 368                                 $p['connLogger'] = new NullLogger();
 369                         }
 370                         if ( !isset( $p['queryLogger'] ) ) {
 371                                 $p['queryLogger'] = new NullLogger();
 372                         }
 373                         $p['profiler'] = isset( $p['profiler'] ) ? $p['profiler'] : null;
 374                         if ( !isset( $p['trxProfiler'] ) ) {
 375                                 $p['trxProfiler'] = new TransactionProfiler();
 376                         }
 377                         if ( !isset( $p['errorLogger'] ) ) {
 378                                 $p['errorLogger'] = function ( Exception $e ) {
 379                                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 380                                 };
 381                         }
 382
 383                         $conn = new $class( $p );
 384                 } else {
 385                         $conn = null;
 386                 }
 387
 388                 return $conn;
 389         }
 390
 391         /**
 392          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 393          * @param string|null $driver Optional name of a specific DB client driver
 394          * @return array Map of (Database::ATTRIBUTE_* constant => value) for all such constants
 395          * @throws InvalidArgumentException
 396          * @since 1.31
 397          */
 398         final public static function attributesFromType( $dbType, $driver = null ) {
 399                 static $defaults = [ self::ATTR_DB_LEVEL_LOCKING => false ];
 400
 401                 $class = self::getClass( $dbType, $driver );
 402
 403                 return call_user_func( [ $class, 'getAttributes' ] ) + $defaults;
 404         }
 405
 406         /**
 407          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 408          * @param string|null $driver Optional name of a specific DB client driver
 409          * @return string Database subclass name to use
 410          * @throws InvalidArgumentException
 411          */
 412         private static function getClass( $dbType, $driver = null ) {
 413                 // For database types with built-in support, the below maps type to IDatabase
 414                 // implementations. For types with multipe driver implementations (PHP extensions),
 415                 // an array can be used, keyed by extension name. In case of an array, the
 416                 // optional 'driver' parameter can be used to force a specific driver. Otherwise,
 417                 // we auto-detect the first available driver. For types without built-in support,
 418                 // an class named "Database<Type>" us used, eg. DatabaseFoo for type 'foo'.
 419                 static $builtinTypes = [
 420                         'mssql' => DatabaseMssql::class,
 421                         'mysql' => [ 'mysqli' => DatabaseMysqli::class ],
 422                         'sqlite' => DatabaseSqlite::class,
 423                         'postgres' => DatabasePostgres::class,
 424                 ];
 425
 426                 $dbType = strtolower( $dbType );
 427                 $class = false;
 428
 429                 if ( isset( $builtinTypes[$dbType] ) ) {
 430                         $possibleDrivers = $builtinTypes[$dbType];
 431                         if ( is_string( $possibleDrivers ) ) {
 432                                 $class = $possibleDrivers;
 433                         } else {
 434                                 if ( (string)$driver !== '' ) {
 435                                         if ( !isset( $possibleDrivers[$driver] ) ) {
 436                                                 throw new InvalidArgumentException( __METHOD__ .
 437                                                         " type '$dbType' does not support driver '{$driver}'" );
 438                                         } else {
 439                                                 $class = $possibleDrivers[$driver];
 440                                         }
 441                                 } else {
 442                                         foreach ( $possibleDrivers as $posDriver => $possibleClass ) {
 443                                                 if ( extension_loaded( $posDriver ) ) {
 444                                                         $class = $possibleClass;
 445                                                         break;
 446                                                 }
 447                                         }
 448                                 }
 449                         }
 450                 } else {
 451                         $class = 'Database' . ucfirst( $dbType );
 452                 }
 453
 454                 if ( $class === false ) {
 455                         throw new InvalidArgumentException( __METHOD__ .
 456                                 " no viable database extension found for type '$dbType'" );
 457                 }
 458
 459                 return $class;
 460         }
 461
 462         /**
 463          * @return array Map of (Database::ATTRIBUTE_* constant => value
 464          * @since 1.31
 465          */
 466         protected static function getAttributes() {
 467                 return [];
 468         }
 469
 470         /**
 471          * Set the PSR-3 logger interface to use for query logging. (The logger
 472          * interfaces for connection logging and error logging can be set with the
 473          * constructor.)
 474          *
 475          * @param LoggerInterface $logger
 476          */
 477         public function setLogger( LoggerInterface $logger ) {
 478                 $this->queryLogger = $logger;
 479         }
 480
 481         public function getServerInfo() {
 482                 return $this->getServerVersion();
 483         }
 484
 485         public function bufferResults( $buffer = null ) {
 486                 $res = !$this->getFlag( self::DBO_NOBUFFER );
 487                 if ( $buffer !== null ) {
 488                         $buffer
 489                                 ? $this->clearFlag( self::DBO_NOBUFFER )
 490                                 : $this->setFlag( self::DBO_NOBUFFER );
 491                 }
 492
 493                 return $res;
 494         }
 495
 496         /**
 497          * Turns on (false) or off (true) the automatic generation and sending
 498          * of a "we're sorry, but there has been a database error" page on
 499          * database errors. Default is on (false). When turned off, the
 500          * code should use lastErrno() and lastError() to handle the
 501          * situation as appropriate.
 502          *
 503          * Do not use this function outside of the Database classes.
 504          *
 505          * @param null|bool $ignoreErrors
 506          * @return bool The previous value of the flag.
 507          */
 508         protected function ignoreErrors( $ignoreErrors = null ) {
 509                 $res = $this->getFlag( self::DBO_IGNORE );
 510                 if ( $ignoreErrors !== null ) {
 511                         // setFlag()/clearFlag() do not allow DBO_IGNORE changes for sanity
 512                         if ( $ignoreErrors ) {
 513                                 $this->flags |= self::DBO_IGNORE;
 514                         } else {
 515                                 $this->flags &= ~self::DBO_IGNORE;
 516                         }
 517                 }
 518
 519                 return $res;
 520         }
 521
 522         public function trxLevel() {
 523                 return $this->trxLevel;
 524         }
 525
 526         public function trxTimestamp() {
 527                 return $this->trxLevel ? $this->trxTimestamp : null;
 528         }
 529
 530         public function tablePrefix( $prefix = null ) {
 531                 $old = $this->tablePrefix;
 532                 if ( $prefix !== null ) {
 533                         $this->tablePrefix = $prefix;
 534                         $this->currentDomain = ( $this->dbName != '' )
 535                                 ? new DatabaseDomain( $this->dbName, null, $this->tablePrefix )
 536                                 : DatabaseDomain::newUnspecified();
 537                 }
 538
 539                 return $old;
 540         }
 541
 542         public function dbSchema( $schema = null ) {
 543                 $old = $this->schema;
 544                 if ( $schema !== null ) {
 545                         $this->schema = $schema;
 546                 }
 547
 548                 return $old;
 549         }
 550
 551         public function getLBInfo( $name = null ) {
 552                 if ( is_null( $name ) ) {
 553                         return $this->lbInfo;
 554                 } else {
 555                         if ( array_key_exists( $name, $this->lbInfo ) ) {
 556                                 return $this->lbInfo[$name];
 557                         } else {
 558                                 return null;
 559                         }
 560                 }
 561         }
 562
 563         public function setLBInfo( $name, $value = null ) {
 564                 if ( is_null( $value ) ) {
 565                         $this->lbInfo = $name;
 566                 } else {
 567                         $this->lbInfo[$name] = $value;
 568                 }
 569         }
 570
 571         public function setLazyMasterHandle( IDatabase $conn ) {
 572                 $this->lazyMasterHandle = $conn;
 573         }
 574
 575         /**
 576          * @return IDatabase|null
 577          * @see setLazyMasterHandle()
 578          * @since 1.27
 579          */
 580         protected function getLazyMasterHandle() {
 581                 return $this->lazyMasterHandle;
 582         }
 583
 584         public function implicitGroupby() {
 585                 return true;
 586         }
 587
 588         public function implicitOrderby() {
 589                 return true;
 590         }
 591
 592         public function lastQuery() {
 593                 return $this->lastQuery;
 594         }
 595
 596         public function doneWrites() {
 597                 return (bool)$this->lastWriteTime;
 598         }
 599
 600         public function lastDoneWrites() {
 601                 return $this->lastWriteTime ?: false;
 602         }
 603
 604         public function writesPending() {
 605                 return $this->trxLevel && $this->trxDoneWrites;
 606         }
 607
 608         public function writesOrCallbacksPending() {
 609                 return $this->trxLevel && (
 610                         $this->trxDoneWrites ||
 611                         $this->trxIdleCallbacks ||
 612                         $this->trxPreCommitCallbacks ||
 613                         $this->trxEndCallbacks
 614                 );
 615         }
 616
 617         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 618                 if ( !$this->trxLevel ) {
 619                         return false;
 620                 } elseif ( !$this->trxDoneWrites ) {
 621                         return 0.0;
 622                 }
 623
 624                 switch ( $type ) {
 625                         case self::ESTIMATE_DB_APPLY:
 626                                 $this->ping( $rtt );
 627                                 $rttAdjTotal = $this->trxWriteAdjQueryCount * $rtt;
 628                                 $applyTime = max( $this->trxWriteAdjDuration - $rttAdjTotal, 0 );
 629                                 // For omitted queries, make them count as something at least
 630                                 $omitted = $this->trxWriteQueryCount - $this->trxWriteAdjQueryCount;
 631                                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 632
 633                                 return $applyTime;
 634                         default: // everything
 635                                 return $this->trxWriteDuration;
 636                 }
 637         }
 638
 639         public function pendingWriteCallers() {
 640                 return $this->trxLevel ? $this->trxWriteCallers : [];
 641         }
 642
 643         public function pendingWriteRowsAffected() {
 644                 return $this->trxWriteAffectedRows;
 645         }
 646
 647         /**
 648          * Get the list of method names that have pending write queries or callbacks
 649          * for this transaction
 650          *
 651          * @return array
 652          */
 653         protected function pendingWriteAndCallbackCallers() {
 654                 if ( !$this->trxLevel ) {
 655                         return [];
 656                 }
 657
 658                 $fnames = $this->trxWriteCallers;
 659                 foreach ( [
 660                         $this->trxIdleCallbacks,
 661                         $this->trxPreCommitCallbacks,
 662                         $this->trxEndCallbacks
 663                 ] as $callbacks ) {
 664                         foreach ( $callbacks as $callback ) {
 665                                 $fnames[] = $callback[1];
 666                         }
 667                 }
 668
 669                 return $fnames;
 670         }
 671
 672         public function isOpen() {
 673                 return $this->opened;
 674         }
 675
 676         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 677                 if ( ( $flag & self::DBO_IGNORE ) ) {
 678                         throw new \UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 679                 }
 680
 681                 if ( $remember === self::REMEMBER_PRIOR ) {
 682                         array_push( $this->priorFlags, $this->flags );
 683                 }
 684                 $this->flags |= $flag;
 685         }
 686
 687         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 688                 if ( ( $flag & self::DBO_IGNORE ) ) {
 689                         throw new \UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 690                 }
 691
 692                 if ( $remember === self::REMEMBER_PRIOR ) {
 693                         array_push( $this->priorFlags, $this->flags );
 694                 }
 695                 $this->flags &= ~$flag;
 696         }
 697
 698         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 699                 if ( !$this->priorFlags ) {
 700                         return;
 701                 }
 702
 703                 if ( $state === self::RESTORE_INITIAL ) {
 704                         $this->flags = reset( $this->priorFlags );
 705                         $this->priorFlags = [];
 706                 } else {
 707                         $this->flags = array_pop( $this->priorFlags );
 708                 }
 709         }
 710
 711         public function getFlag( $flag ) {
 712                 return !!( $this->flags & $flag );
 713         }
 714
 715         /**
 716          * @param string $name Class field name
 717          * @return mixed
 718          * @deprecated Since 1.28
 719          */
 720         public function getProperty( $name ) {
 721                 return $this->$name;
 722         }
 723
 724         public function getDomainID() {
 725                 return $this->currentDomain->getId();
 726         }
 727
 728         final public function getWikiID() {
 729                 return $this->getDomainID();
 730         }
 731
 732         /**
 733          * Get information about an index into an object
 734          * @param string $table Table name
 735          * @param string $index Index name
 736          * @param string $fname Calling function name
 737          * @return mixed Database-specific index description class or false if the index does not exist
 738          */
 739         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 740
 741         /**
 742          * Wrapper for addslashes()
 743          *
 744          * @param string $s String to be slashed.
 745          * @return string Slashed string.
 746          */
 747         abstract function strencode( $s );
 748
 749         /**
 750          * Set a custom error handler for logging errors during database connection
 751          */
 752         protected function installErrorHandler() {
 753                 $this->phpError = false;
 754                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 755                 set_error_handler( [ $this, 'connectionErrorLogger' ] );
 756         }
 757
 758         /**
 759          * Restore the previous error handler and return the last PHP error for this DB
 760          *
 761          * @return bool|string
 762          */
 763         protected function restoreErrorHandler() {
 764                 restore_error_handler();
 765                 if ( $this->htmlErrors !== false ) {
 766                         ini_set( 'html_errors', $this->htmlErrors );
 767                 }
 768
 769                 return $this->getLastPHPError();
 770         }
 771
 772         /**
 773          * @return string|bool Last PHP error for this DB (typically connection errors)
 774          */
 775         protected function getLastPHPError() {
 776                 if ( $this->phpError ) {
 777                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->phpError );
 778                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 779
 780                         return $error;
 781                 }
 782
 783                 return false;
 784         }
 785
 786         /**
 787          * Error handler for logging errors during database connection
 788          * This method should not be used outside of Database classes
 789          *
 790          * @param int $errno
 791          * @param string $errstr
 792          */
 793         public function connectionErrorLogger( $errno, $errstr ) {
 794                 $this->phpError = $errstr;
 795         }
 796
 797         /**
 798          * Create a log context to pass to PSR-3 logger functions.
 799          *
 800          * @param array $extras Additional data to add to context
 801          * @return array
 802          */
 803         protected function getLogContext( array $extras = [] ) {
 804                 return array_merge(
 805                         [
 806                                 'db_server' => $this->server,
 807                                 'db_name' => $this->dbName,
 808                                 'db_user' => $this->user,
 809                         ],
 810                         $extras
 811                 );
 812         }
 813
 814         public function close() {
 815                 if ( $this->conn ) {
 816                         // Resolve any dangling transaction first
 817                         if ( $this->trxLevel() ) {
 818                                 // Meaningful transactions should ideally have been resolved by now
 819                                 if ( $this->writesOrCallbacksPending() ) {
 820                                         $this->queryLogger->warning(
 821                                                 __METHOD__ . ": writes or callbacks still pending.",
 822                                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
 823                                         );
 824                                 }
 825                                 // Check if it is possible to properly commit and trigger callbacks
 826                                 if ( $this->trxEndCallbacksSuppressed ) {
 827                                         throw new DBUnexpectedError(
 828                                                 $this,
 829                                                 __METHOD__ . ': callbacks are suppressed; cannot properly commit.'
 830                                         );
 831                                 }
 832                                 // Commit the changes and run any callbacks as needed
 833                                 $this->commit( __METHOD__, self::FLUSHING_INTERNAL );
 834                         }
 835                         // Close the actual connection in the binding handle
 836                         $closed = $this->closeConnection();
 837                         $this->conn = false;
 838                         // Sanity check that no callbacks are dangling
 839                         if (
 840                                 $this->trxIdleCallbacks || $this->trxPreCommitCallbacks || $this->trxEndCallbacks
 841                         ) {
 842                                 throw new RuntimeException( "Transaction callbacks still pending." );
 843                         }
 844                 } else {
 845                         $closed = true; // already closed; nothing to do
 846                 }
 847
 848                 $this->opened = false;
 849
 850                 return $closed;
 851         }
 852
 853         /**
 854          * Make sure isOpen() returns true as a sanity check
 855          *
 856          * @throws DBUnexpectedError
 857          */
 858         protected function assertOpen() {
 859                 if ( !$this->isOpen() ) {
 860                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
 861                 }
 862         }
 863
 864         /**
 865          * Closes underlying database connection
 866          * @since 1.20
 867          * @return bool Whether connection was closed successfully
 868          */
 869         abstract protected function closeConnection();
 870
 871         public function reportConnectionError( $error = 'Unknown error' ) {
 872                 $myError = $this->lastError();
 873                 if ( $myError ) {
 874                         $error = $myError;
 875                 }
 876
 877                 # New method
 878                 throw new DBConnectionError( $this, $error );
 879         }
 880
 881         /**
 882          * The DBMS-dependent part of query()
 883          *
 884          * @param string $sql SQL query.
 885          * @return ResultWrapper|bool Result object to feed to fetchObject,
 886          *   fetchRow, ...; or false on failure
 887          */
 888         abstract protected function doQuery( $sql );
 889
 890         /**
 891          * Determine whether a query writes to the DB.
 892          * Should return true if unsure.
 893          *
 894          * @param string $sql
 895          * @return bool
 896          */
 897         protected function isWriteQuery( $sql ) {
 898                 return !preg_match(
 899                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 900         }
 901
 902         /**
 903          * @param string $sql
 904          * @return string|null
 905          */
 906         protected function getQueryVerb( $sql ) {
 907                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
 908         }
 909
 910         /**
 911          * Determine whether a SQL statement is sensitive to isolation level.
 912          * A SQL statement is considered transactable if its result could vary
 913          * depending on the transaction isolation level. Operational commands
 914          * such as 'SET' and 'SHOW' are not considered to be transactable.
 915          *
 916          * @param string $sql
 917          * @return bool
 918          */
 919         protected function isTransactableQuery( $sql ) {
 920                 return !in_array(
 921                         $this->getQueryVerb( $sql ),
 922                         [ 'BEGIN', 'COMMIT', 'ROLLBACK', 'SHOW', 'SET', 'CREATE', 'ALTER' ],
 923                         true
 924                 );
 925         }
 926
 927         /**
 928          * @param string $sql A SQL query
 929          * @return bool Whether $sql is SQL for TEMPORARY table operation
 930          */
 931         protected function registerTempTableOperation( $sql ) {
 932                 if ( preg_match(
 933                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 934                         $sql,
 935                         $matches
 936                 ) ) {
 937                         $this->sessionTempTables[$matches[1]] = 1;
 938
 939                         return true;
 940                 } elseif ( preg_match(
 941                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 942                         $sql,
 943                         $matches
 944                 ) ) {
 945                         $isTemp = isset( $this->sessionTempTables[$matches[1]] );
 946                         unset( $this->sessionTempTables[$matches[1]] );
 947
 948                         return $isTemp;
 949                 } elseif ( preg_match(
 950                         '/^TRUNCATE\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 951                         $sql,
 952                         $matches
 953                 ) ) {
 954                         return isset( $this->sessionTempTables[$matches[1]] );
 955                 } elseif ( preg_match(
 956                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
 957                         $sql,
 958                         $matches
 959                 ) ) {
 960                         return isset( $this->sessionTempTables[$matches[1]] );
 961                 }
 962
 963                 return false;
 964         }
 965
 966         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 967                 $priorWritesPending = $this->writesOrCallbacksPending();
 968                 $this->lastQuery = $sql;
 969
 970                 $isWrite = $this->isWriteQuery( $sql );
 971                 if ( $isWrite ) {
 972                         $isNonTempWrite = !$this->registerTempTableOperation( $sql );
 973                 } else {
 974                         $isNonTempWrite = false;
 975                 }
 976
 977                 if ( $isWrite ) {
 978                         if ( $this->getLBInfo( 'replica' ) === true ) {
 979                                 throw new DBError(
 980                                         $this,
 981                                         'Write operations are not allowed on replica database connections.'
 982                                 );
 983                         }
 984                         # In theory, non-persistent writes are allowed in read-only mode, but due to things
 985                         # like https://bugs.mysql.com/bug.php?id=33669 that might not work anyway...
 986                         $reason = $this->getReadOnlyReason();
 987                         if ( $reason !== false ) {
 988                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
 989                         }
 990                         # Set a flag indicating that writes have been done
 991                         $this->lastWriteTime = microtime( true );
 992                 }
 993
 994                 # Add trace comment to the begin of the sql string, right after the operator.
 995                 # Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598)
 996                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
 997
 998                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
 999                 if ( !$this->trxLevel && $this->getFlag( self::DBO_TRX )
1000                         && $this->isTransactableQuery( $sql )
1001                 ) {
1002                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
1003                         $this->trxAutomatic = true;
1004                 }
1005
1006                 # Keep track of whether the transaction has write queries pending
1007                 if ( $this->trxLevel && !$this->trxDoneWrites && $isWrite ) {
1008                         $this->trxDoneWrites = true;
1009                         $this->trxProfiler->transactionWritingIn(
1010                                 $this->server, $this->dbName, $this->trxShortId );
1011                 }
1012
1013                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
1014                         $this->queryLogger->debug( "{$this->dbName} {$commentedSql}" );
1015                 }
1016
1017                 # Avoid fatals if close() was called
1018                 $this->assertOpen();
1019
1020                 # Send the query to the server
1021                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1022
1023                 # Try reconnecting if the connection was lost
1024                 if ( false === $ret && $this->wasErrorReissuable() ) {
1025                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
1026                         # Stash the last error values before anything might clear them
1027                         $lastError = $this->lastError();
1028                         $lastErrno = $this->lastErrno();
1029                         # Update state tracking to reflect transaction loss due to disconnection
1030                         $this->handleSessionLoss();
1031                         if ( $this->reconnect() ) {
1032                                 $msg = __METHOD__ . ': lost connection to {dbserver}; reconnected';
1033                                 $params = [ 'dbserver' => $this->getServer() ];
1034                                 $this->connLogger->warning( $msg, $params );
1035                                 $this->queryLogger->warning( $msg, $params +
1036                                         [ 'trace' => ( new RuntimeException() )->getTraceAsString() ] );
1037
1038                                 if ( $recoverable ) {
1039                                         # Should be safe to silently retry the query
1040                                         $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1041                                 } else {
1042                                         # Callers may catch the exception and continue to use the DB
1043                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname );
1044                                 }
1045                         } else {
1046                                 $msg = __METHOD__ . ': lost connection to {dbserver} permanently';
1047                                 $this->connLogger->error( $msg, [ 'dbserver' => $this->getServer() ] );
1048                         }
1049                 }
1050
1051                 if ( false === $ret ) {
1052                         # Deadlocks cause the entire transaction to abort, not just the statement.
1053                         # https://dev.mysql.com/doc/refman/5.7/en/innodb-error-handling.html
1054                         # https://www.postgresql.org/docs/9.1/static/explicit-locking.html
1055                         if ( $this->wasDeadlock() ) {
1056                                 if ( $this->explicitTrxActive() || $priorWritesPending ) {
1057                                         $tempIgnore = false; // not recoverable
1058                                 }
1059                                 # Update state tracking to reflect transaction loss
1060                                 $this->handleSessionLoss();
1061                         }
1062
1063                         $this->reportQueryError(
1064                                 $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1065                 }
1066
1067                 $res = $this->resultObject( $ret );
1068
1069                 return $res;
1070         }
1071
1072         /**
1073          * Wrapper for query() that also handles profiling, logging, and affected row count updates
1074          *
1075          * @param string $sql Original SQL query
1076          * @param string $commentedSql SQL query with debugging/trace comment
1077          * @param bool $isWrite Whether the query is a (non-temporary) write operation
1078          * @param string $fname Name of the calling function
1079          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
1080          *     object for a successful read query, or false on failure
1081          */
1082         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
1083                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1084                 # generalizeSQL() will probably cut down the query to reasonable
1085                 # logging size most of the time. The substr is really just a sanity check.
1086                 if ( $isMaster ) {
1087                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1088                 } else {
1089                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1090                 }
1091
1092                 # Include query transaction state
1093                 $queryProf .= $this->trxShortId ? " [TRX#{$this->trxShortId}]" : "";
1094
1095                 $startTime = microtime( true );
1096                 if ( $this->profiler ) {
1097                         call_user_func( [ $this->profiler, 'profileIn' ], $queryProf );
1098                 }
1099                 $this->affectedRowCount = null;
1100                 $ret = $this->doQuery( $commentedSql );
1101                 $this->affectedRowCount = $this->affectedRows();
1102                 if ( $this->profiler ) {
1103                         call_user_func( [ $this->profiler, 'profileOut' ], $queryProf );
1104                 }
1105                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1106
1107                 unset( $queryProfSection ); // profile out (if set)
1108
1109                 if ( $ret !== false ) {
1110                         $this->lastPing = $startTime;
1111                         if ( $isWrite && $this->trxLevel ) {
1112                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1113                                 $this->trxWriteCallers[] = $fname;
1114                         }
1115                 }
1116
1117                 if ( $sql === self::PING_QUERY ) {
1118                         $this->rttEstimate = $queryRuntime;
1119                 }
1120
1121                 $this->trxProfiler->recordQueryCompletion(
1122                         $queryProf, $startTime, $isWrite, $this->affectedRows()
1123                 );
1124                 $this->queryLogger->debug( $sql, [
1125                         'method' => $fname,
1126                         'master' => $isMaster,
1127                         'runtime' => $queryRuntime,
1128                 ] );
1129
1130                 return $ret;
1131         }
1132
1133         /**
1134          * Update the estimated run-time of a query, not counting large row lock times
1135          *
1136          * LoadBalancer can be set to rollback transactions that will create huge replication
1137          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1138          * queries, like inserting a row can take a long time due to row locking. This method
1139          * uses some simple heuristics to discount those cases.
1140          *
1141          * @param string $sql A SQL write query
1142          * @param float $runtime Total runtime, including RTT
1143          * @param int $affected Affected row count
1144          */
1145         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1146                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1147                 $indicativeOfReplicaRuntime = true;
1148                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1149                         $verb = $this->getQueryVerb( $sql );
1150                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1151                         if ( $verb === 'INSERT' ) {
1152                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1153                         } elseif ( $verb === 'REPLACE' ) {
1154                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1155                         }
1156                 }
1157
1158                 $this->trxWriteDuration += $runtime;
1159                 $this->trxWriteQueryCount += 1;
1160                 $this->trxWriteAffectedRows += $affected;
1161                 if ( $indicativeOfReplicaRuntime ) {
1162                         $this->trxWriteAdjDuration += $runtime;
1163                         $this->trxWriteAdjQueryCount += 1;
1164                 }
1165         }
1166
1167         /**
1168          * Determine whether or not it is safe to retry queries after a database
1169          * connection is lost
1170          *
1171          * @param string $sql SQL query
1172          * @param bool $priorWritesPending Whether there is a transaction open with
1173          *     possible write queries or transaction pre-commit/idle callbacks
1174          *     waiting on it to finish.
1175          * @return bool True if it is safe to retry the query, false otherwise
1176          */
1177         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1178                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1179                 # Dropped connections also mean that named locks are automatically released.
1180                 # Only allow error suppression in autocommit mode or when the lost transaction
1181                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1182                 if ( $this->namedLocksHeld ) {
1183                         return false; // possible critical section violation
1184                 } elseif ( $sql === 'COMMIT' ) {
1185                         return !$priorWritesPending; // nothing written anyway? (T127428)
1186                 } elseif ( $sql === 'ROLLBACK' ) {
1187                         return true; // transaction lost...which is also what was requested :)
1188                 } elseif ( $this->explicitTrxActive() ) {
1189                         return false; // don't drop atomocity
1190                 } elseif ( $priorWritesPending ) {
1191                         return false; // prior writes lost from implicit transaction
1192                 }
1193
1194                 return true;
1195         }
1196
1197         /**
1198          * Clean things up after transaction loss due to disconnection
1199          *
1200          * @return null|Exception
1201          */
1202         private function handleSessionLoss() {
1203                 $this->trxLevel = 0;
1204                 $this->trxIdleCallbacks = []; // T67263; transaction already lost
1205                 $this->trxPreCommitCallbacks = []; // T67263; transaction already lost
1206                 $this->sessionTempTables = [];
1207                 $this->namedLocksHeld = [];
1208
1209                 // Note: if callback suppression is set then some *Callbacks arrays are not cleared here
1210                 $e = null;
1211                 try {
1212                         // Handle callbacks in trxEndCallbacks
1213                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1214                 } catch ( Exception $ex ) {
1215                         // Already logged; move on...
1216                         $e = $e ?: $ex;
1217                 }
1218                 try {
1219                         // Handle callbacks in trxRecurringCallbacks
1220                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1221                 } catch ( Exception $ex ) {
1222                         // Already logged; move on...
1223                         $e = $e ?: $ex;
1224                 }
1225
1226                 return $e;
1227         }
1228
1229         /**
1230          * Checks whether the cause of the error is detected to be a timeout.
1231          *
1232          * It returns false by default, and not all engines support detecting this yet.
1233          * If this returns false, it will be treated as a generic query error.
1234          *
1235          * @param string $error Error text
1236          * @param int $errno Error number
1237          * @return bool
1238          */
1239         protected function wasQueryTimeout( $error, $errno ) {
1240                 return false;
1241         }
1242
1243         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1244                 if ( $this->ignoreErrors() || $tempIgnore ) {
1245                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1246                 } else {
1247                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1248                         $this->queryLogger->error(
1249                                 "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1250                                 $this->getLogContext( [
1251                                         'method' => __METHOD__,
1252                                         'errno' => $errno,
1253                                         'error' => $error,
1254                                         'sql1line' => $sql1line,
1255                                         'fname' => $fname,
1256                                 ] )
1257                         );
1258                         $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1259                         $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1260                         if ( $wasQueryTimeout ) {
1261                                 throw new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1262                         } else {
1263                                 throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1264                         }
1265                 }
1266         }
1267
1268         public function freeResult( $res ) {
1269         }
1270
1271         public function selectField(
1272                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1273         ) {
1274                 if ( $var === '*' ) { // sanity
1275                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1276                 }
1277
1278                 if ( !is_array( $options ) ) {
1279                         $options = [ $options ];
1280                 }
1281
1282                 $options['LIMIT'] = 1;
1283
1284                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1285                 if ( $res === false || !$this->numRows( $res ) ) {
1286                         return false;
1287                 }
1288
1289                 $row = $this->fetchRow( $res );
1290
1291                 if ( $row !== false ) {
1292                         return reset( $row );
1293                 } else {
1294                         return false;
1295                 }
1296         }
1297
1298         public function selectFieldValues(
1299                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1300         ) {
1301                 if ( $var === '*' ) { // sanity
1302                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1303                 } elseif ( !is_string( $var ) ) { // sanity
1304                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1305                 }
1306
1307                 if ( !is_array( $options ) ) {
1308                         $options = [ $options ];
1309                 }
1310
1311                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1312                 if ( $res === false ) {
1313                         return false;
1314                 }
1315
1316                 $values = [];
1317                 foreach ( $res as $row ) {
1318                         $values[] = $row->$var;
1319                 }
1320
1321                 return $values;
1322         }
1323
1324         /**
1325          * Returns an optional USE INDEX clause to go after the table, and a
1326          * string to go at the end of the query.
1327          *
1328          * @param array $options Associative array of options to be turned into
1329          *   an SQL query, valid keys are listed in the function.
1330          * @return array
1331          * @see Database::select()
1332          */
1333         protected function makeSelectOptions( $options ) {
1334                 $preLimitTail = $postLimitTail = '';
1335                 $startOpts = '';
1336
1337                 $noKeyOptions = [];
1338
1339                 foreach ( $options as $key => $option ) {
1340                         if ( is_numeric( $key ) ) {
1341                                 $noKeyOptions[$option] = true;
1342                         }
1343                 }
1344
1345                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1346
1347                 $preLimitTail .= $this->makeOrderBy( $options );
1348
1349                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1350                         $postLimitTail .= ' FOR UPDATE';
1351                 }
1352
1353                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1354                         $postLimitTail .= ' LOCK IN SHARE MODE';
1355                 }
1356
1357                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1358                         $startOpts .= 'DISTINCT';
1359                 }
1360
1361                 # Various MySQL extensions
1362                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1363                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1364                 }
1365
1366                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1367                         $startOpts .= ' HIGH_PRIORITY';
1368                 }
1369
1370                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1371                         $startOpts .= ' SQL_BIG_RESULT';
1372                 }
1373
1374                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1375                         $startOpts .= ' SQL_BUFFER_RESULT';
1376                 }
1377
1378                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1379                         $startOpts .= ' SQL_SMALL_RESULT';
1380                 }
1381
1382                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1383                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1384                 }
1385
1386                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1387                         $startOpts .= ' SQL_CACHE';
1388                 }
1389
1390                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1391                         $startOpts .= ' SQL_NO_CACHE';
1392                 }
1393
1394                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1395                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1396                 } else {
1397                         $useIndex = '';
1398                 }
1399                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1400                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1401                 } else {
1402                         $ignoreIndex = '';
1403                 }
1404
1405                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1406         }
1407
1408         /**
1409          * Returns an optional GROUP BY with an optional HAVING
1410          *
1411          * @param array $options Associative array of options
1412          * @return string
1413          * @see Database::select()
1414          * @since 1.21
1415          */
1416         protected function makeGroupByWithHaving( $options ) {
1417                 $sql = '';
1418                 if ( isset( $options['GROUP BY'] ) ) {
1419                         $gb = is_array( $options['GROUP BY'] )
1420                                 ? implode( ',', $options['GROUP BY'] )
1421                                 : $options['GROUP BY'];
1422                         $sql .= ' GROUP BY ' . $gb;
1423                 }
1424                 if ( isset( $options['HAVING'] ) ) {
1425                         $having = is_array( $options['HAVING'] )
1426                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1427                                 : $options['HAVING'];
1428                         $sql .= ' HAVING ' . $having;
1429                 }
1430
1431                 return $sql;
1432         }
1433
1434         /**
1435          * Returns an optional ORDER BY
1436          *
1437          * @param array $options Associative array of options
1438          * @return string
1439          * @see Database::select()
1440          * @since 1.21
1441          */
1442         protected function makeOrderBy( $options ) {
1443                 if ( isset( $options['ORDER BY'] ) ) {
1444                         $ob = is_array( $options['ORDER BY'] )
1445                                 ? implode( ',', $options['ORDER BY'] )
1446                                 : $options['ORDER BY'];
1447
1448                         return ' ORDER BY ' . $ob;
1449                 }
1450
1451                 return '';
1452         }
1453
1454         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1455                 $options = [], $join_conds = [] ) {
1456                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1457
1458                 return $this->query( $sql, $fname );
1459         }
1460
1461         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1462                 $options = [], $join_conds = []
1463         ) {
1464                 if ( is_array( $vars ) ) {
1465                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1466                 }
1467
1468                 $options = (array)$options;
1469                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1470                         ? $options['USE INDEX']
1471                         : [];
1472                 $ignoreIndexes = (
1473                         isset( $options['IGNORE INDEX'] ) &&
1474                         is_array( $options['IGNORE INDEX'] )
1475                 )
1476                         ? $options['IGNORE INDEX']
1477                         : [];
1478
1479                 if ( is_array( $table ) ) {
1480                         $from = ' FROM ' .
1481                                 $this->tableNamesWithIndexClauseOrJOIN(
1482                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1483                 } elseif ( $table != '' ) {
1484                         $from = ' FROM ' .
1485                                 $this->tableNamesWithIndexClauseOrJOIN(
1486                                         [ $table ], $useIndexes, $ignoreIndexes, [] );
1487                 } else {
1488                         $from = '';
1489                 }
1490
1491                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1492                         $this->makeSelectOptions( $options );
1493
1494                 if ( is_array( $conds ) ) {
1495                         $conds = $this->makeList( $conds, self::LIST_AND );
1496                 }
1497
1498                 if ( $conds === null || $conds === false ) {
1499                         $this->queryLogger->warning(
1500                                 __METHOD__
1501                                 . ' called from '
1502                                 . $fname
1503                                 . ' with incorrect parameters: $conds must be a string or an array'
1504                         );
1505                         $conds = '';
1506                 }
1507
1508                 if ( $conds === '' ) {
1509                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex $preLimitTail";
1510                 } elseif ( is_string( $conds ) ) {
1511                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex " .
1512                                 "WHERE $conds $preLimitTail";
1513                 } else {
1514                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1515                 }
1516
1517                 if ( isset( $options['LIMIT'] ) ) {
1518                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1519                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1520                 }
1521                 $sql = "$sql $postLimitTail";
1522
1523                 if ( isset( $options['EXPLAIN'] ) ) {
1524                         $sql = 'EXPLAIN ' . $sql;
1525                 }
1526
1527                 return $sql;
1528         }
1529
1530         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1531                 $options = [], $join_conds = []
1532         ) {
1533                 $options = (array)$options;
1534                 $options['LIMIT'] = 1;
1535                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1536
1537                 if ( $res === false ) {
1538                         return false;
1539                 }
1540
1541                 if ( !$this->numRows( $res ) ) {
1542                         return false;
1543                 }
1544
1545                 $obj = $this->fetchObject( $res );
1546
1547                 return $obj;
1548         }
1549
1550         public function estimateRowCount(
1551                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
1552         ) {
1553                 $rows = 0;
1554                 $res = $this->select( $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options );
1555
1556                 if ( $res ) {
1557                         $row = $this->fetchRow( $res );
1558                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1559                 }
1560
1561                 return $rows;
1562         }
1563
1564         public function selectRowCount(
1565                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1566         ) {
1567                 $rows = 0;
1568                 $sql = $this->selectSQLText( $tables, '1', $conds, $fname, $options, $join_conds );
1569                 // The identifier quotes is primarily for MSSQL.
1570                 $rowCountCol = $this->addIdentifierQuotes( "rowcount" );
1571                 $tableName = $this->addIdentifierQuotes( "tmp_count" );
1572                 $res = $this->query( "SELECT COUNT(*) AS $rowCountCol FROM ($sql) $tableName", $fname );
1573
1574                 if ( $res ) {
1575                         $row = $this->fetchRow( $res );
1576                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1577                 }
1578
1579                 return $rows;
1580         }
1581
1582         /**
1583          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1584          * It's only slightly flawed. Don't use for anything important.
1585          *
1586          * @param string $sql A SQL Query
1587          *
1588          * @return string
1589          */
1590         protected static function generalizeSQL( $sql ) {
1591                 # This does the same as the regexp below would do, but in such a way
1592                 # as to avoid crashing php on some large strings.
1593                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1594
1595                 $sql = str_replace( "\\\\", '', $sql );
1596                 $sql = str_replace( "\\'", '', $sql );
1597                 $sql = str_replace( "\\\"", '', $sql );
1598                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1599                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1600
1601                 # All newlines, tabs, etc replaced by single space
1602                 $sql = preg_replace( '/\s+/', ' ', $sql );
1603
1604                 # All numbers => N,
1605                 # except the ones surrounded by characters, e.g. l10n
1606                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1607                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1608
1609                 return $sql;
1610         }
1611
1612         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1613                 $info = $this->fieldInfo( $table, $field );
1614
1615                 return (bool)$info;
1616         }
1617
1618         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1619                 if ( !$this->tableExists( $table ) ) {
1620                         return null;
1621                 }
1622
1623                 $info = $this->indexInfo( $table, $index, $fname );
1624                 if ( is_null( $info ) ) {
1625                         return null;
1626                 } else {
1627                         return $info !== false;
1628                 }
1629         }
1630
1631         public function tableExists( $table, $fname = __METHOD__ ) {
1632                 $tableRaw = $this->tableName( $table, 'raw' );
1633                 if ( isset( $this->sessionTempTables[$tableRaw] ) ) {
1634                         return true; // already known to exist
1635                 }
1636
1637                 $table = $this->tableName( $table );
1638                 $ignoreErrors = true;
1639                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname, $ignoreErrors );
1640
1641                 return (bool)$res;
1642         }
1643
1644         public function indexUnique( $table, $index ) {
1645                 $indexInfo = $this->indexInfo( $table, $index );
1646
1647                 if ( !$indexInfo ) {
1648                         return null;
1649                 }
1650
1651                 return !$indexInfo[0]->Non_unique;
1652         }
1653
1654         /**
1655          * Helper for Database::insert().
1656          *
1657          * @param array $options
1658          * @return string
1659          */
1660         protected function makeInsertOptions( $options ) {
1661                 return implode( ' ', $options );
1662         }
1663
1664         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1665                 # No rows to insert, easy just return now
1666                 if ( !count( $a ) ) {
1667                         return true;
1668                 }
1669
1670                 $table = $this->tableName( $table );
1671
1672                 if ( !is_array( $options ) ) {
1673                         $options = [ $options ];
1674                 }
1675
1676                 $fh = null;
1677                 if ( isset( $options['fileHandle'] ) ) {
1678                         $fh = $options['fileHandle'];
1679                 }
1680                 $options = $this->makeInsertOptions( $options );
1681
1682                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1683                         $multi = true;
1684                         $keys = array_keys( $a[0] );
1685                 } else {
1686                         $multi = false;
1687                         $keys = array_keys( $a );
1688                 }
1689
1690                 $sql = 'INSERT ' . $options .
1691                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1692
1693                 if ( $multi ) {
1694                         $first = true;
1695                         foreach ( $a as $row ) {
1696                                 if ( $first ) {
1697                                         $first = false;
1698                                 } else {
1699                                         $sql .= ',';
1700                                 }
1701                                 $sql .= '(' . $this->makeList( $row ) . ')';
1702                         }
1703                 } else {
1704                         $sql .= '(' . $this->makeList( $a ) . ')';
1705                 }
1706
1707                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1708                         return false;
1709                 } elseif ( $fh !== null ) {
1710                         return true;
1711                 }
1712
1713                 return (bool)$this->query( $sql, $fname );
1714         }
1715
1716         /**
1717          * Make UPDATE options array for Database::makeUpdateOptions
1718          *
1719          * @param array $options
1720          * @return array
1721          */
1722         protected function makeUpdateOptionsArray( $options ) {
1723                 if ( !is_array( $options ) ) {
1724                         $options = [ $options ];
1725                 }
1726
1727                 $opts = [];
1728
1729                 if ( in_array( 'IGNORE', $options ) ) {
1730                         $opts[] = 'IGNORE';
1731                 }
1732
1733                 return $opts;
1734         }
1735
1736         /**
1737          * Make UPDATE options for the Database::update function
1738          *
1739          * @param array $options The options passed to Database::update
1740          * @return string
1741          */
1742         protected function makeUpdateOptions( $options ) {
1743                 $opts = $this->makeUpdateOptionsArray( $options );
1744
1745                 return implode( ' ', $opts );
1746         }
1747
1748         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1749                 $table = $this->tableName( $table );
1750                 $opts = $this->makeUpdateOptions( $options );
1751                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
1752
1753                 if ( $conds !== [] && $conds !== '*' ) {
1754                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
1755                 }
1756
1757                 return (bool)$this->query( $sql, $fname );
1758         }
1759
1760         public function makeList( $a, $mode = self::LIST_COMMA ) {
1761                 if ( !is_array( $a ) ) {
1762                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1763                 }
1764
1765                 $first = true;
1766                 $list = '';
1767
1768                 foreach ( $a as $field => $value ) {
1769                         if ( !$first ) {
1770                                 if ( $mode == self::LIST_AND ) {
1771                                         $list .= ' AND ';
1772                                 } elseif ( $mode == self::LIST_OR ) {
1773                                         $list .= ' OR ';
1774                                 } else {
1775                                         $list .= ',';
1776                                 }
1777                         } else {
1778                                 $first = false;
1779                         }
1780
1781                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
1782                                 $list .= "($value)";
1783                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
1784                                 $list .= "$value";
1785                         } elseif (
1786                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
1787                         ) {
1788                                 // Remove null from array to be handled separately if found
1789                                 $includeNull = false;
1790                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
1791                                         $includeNull = true;
1792                                         unset( $value[$nullKey] );
1793                                 }
1794                                 if ( count( $value ) == 0 && !$includeNull ) {
1795                                         throw new InvalidArgumentException(
1796                                                 __METHOD__ . ": empty input for field $field" );
1797                                 } elseif ( count( $value ) == 0 ) {
1798                                         // only check if $field is null
1799                                         $list .= "$field IS NULL";
1800                                 } else {
1801                                         // IN clause contains at least one valid element
1802                                         if ( $includeNull ) {
1803                                                 // Group subconditions to ensure correct precedence
1804                                                 $list .= '(';
1805                                         }
1806                                         if ( count( $value ) == 1 ) {
1807                                                 // Special-case single values, as IN isn't terribly efficient
1808                                                 // Don't necessarily assume the single key is 0; we don't
1809                                                 // enforce linear numeric ordering on other arrays here.
1810                                                 $value = array_values( $value )[0];
1811                                                 $list .= $field . " = " . $this->addQuotes( $value );
1812                                         } else {
1813                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1814                                         }
1815                                         // if null present in array, append IS NULL
1816                                         if ( $includeNull ) {
1817                                                 $list .= " OR $field IS NULL)";
1818                                         }
1819                                 }
1820                         } elseif ( $value === null ) {
1821                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
1822                                         $list .= "$field IS ";
1823                                 } elseif ( $mode == self::LIST_SET ) {
1824                                         $list .= "$field = ";
1825                                 }
1826                                 $list .= 'NULL';
1827                         } else {
1828                                 if (
1829                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
1830                                 ) {
1831                                         $list .= "$field = ";
1832                                 }
1833                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
1834                         }
1835                 }
1836
1837                 return $list;
1838         }
1839
1840         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1841                 $conds = [];
1842
1843                 foreach ( $data as $base => $sub ) {
1844                         if ( count( $sub ) ) {
1845                                 $conds[] = $this->makeList(
1846                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
1847                                         self::LIST_AND );
1848                         }
1849                 }
1850
1851                 if ( $conds ) {
1852                         return $this->makeList( $conds, self::LIST_OR );
1853                 } else {
1854                         // Nothing to search for...
1855                         return false;
1856                 }
1857         }
1858
1859         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1860                 return $valuename;
1861         }
1862
1863         public function bitNot( $field ) {
1864                 return "(~$field)";
1865         }
1866
1867         public function bitAnd( $fieldLeft, $fieldRight ) {
1868                 return "($fieldLeft & $fieldRight)";
1869         }
1870
1871         public function bitOr( $fieldLeft, $fieldRight ) {
1872                 return "($fieldLeft | $fieldRight)";
1873         }
1874
1875         public function buildConcat( $stringList ) {
1876                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1877         }
1878
1879         public function buildGroupConcatField(
1880                 $delim, $table, $field, $conds = '', $join_conds = []
1881         ) {
1882                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
1883
1884                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
1885         }
1886
1887         public function buildSubstring( $input, $startPosition, $length = null ) {
1888                 $this->assertBuildSubstringParams( $startPosition, $length );
1889                 $functionBody = "$input FROM $startPosition";
1890                 if ( $length !== null ) {
1891                         $functionBody .= " FOR $length";
1892                 }
1893                 return 'SUBSTRING(' . $functionBody . ')';
1894         }
1895
1896         /**
1897          * Check type and bounds for parameters to self::buildSubstring()
1898          *
1899          * All supported databases have substring functions that behave the same for
1900          * positive $startPosition and non-negative $length, but behaviors differ when
1901          * given 0 or negative $startPosition or negative $length. The simplest
1902          * solution to that is to just forbid those values.
1903          *
1904          * @param int $startPosition
1905          * @param int|null $length
1906          * @since 1.31
1907          */
1908         protected function assertBuildSubstringParams( $startPosition, $length ) {
1909                 if ( !is_int( $startPosition ) || $startPosition <= 0 ) {
1910                         throw new InvalidArgumentException(
1911                                 '$startPosition must be a positive integer'
1912                         );
1913                 }
1914                 if ( !( is_int( $length ) && $length >= 0 || $length === null ) ) {
1915                         throw new InvalidArgumentException(
1916                                 '$length must be null or an integer greater than or equal to 0'
1917                         );
1918                 }
1919         }
1920
1921         public function buildStringCast( $field ) {
1922                 return $field;
1923         }
1924
1925         public function buildIntegerCast( $field ) {
1926                 return 'CAST( ' . $field . ' AS INTEGER )';
1927         }
1928
1929         public function databasesAreIndependent() {
1930                 return false;
1931         }
1932
1933         public function selectDB( $db ) {
1934                 # Stub. Shouldn't cause serious problems if it's not overridden, but
1935                 # if your database engine supports a concept similar to MySQL's
1936                 # databases you may as well.
1937                 $this->dbName = $db;
1938
1939                 return true;
1940         }
1941
1942         public function getDBname() {
1943                 return $this->dbName;
1944         }
1945
1946         public function getServer() {
1947                 return $this->server;
1948         }
1949
1950         public function tableName( $name, $format = 'quoted' ) {
1951                 # Skip the entire process when we have a string quoted on both ends.
1952                 # Note that we check the end so that we will still quote any use of
1953                 # use of `database`.table. But won't break things if someone wants
1954                 # to query a database table with a dot in the name.
1955                 if ( $this->isQuotedIdentifier( $name ) ) {
1956                         return $name;
1957                 }
1958
1959                 # Lets test for any bits of text that should never show up in a table
1960                 # name. Basically anything like JOIN or ON which are actually part of
1961                 # SQL queries, but may end up inside of the table value to combine
1962                 # sql. Such as how the API is doing.
1963                 # Note that we use a whitespace test rather than a \b test to avoid
1964                 # any remote case where a word like on may be inside of a table name
1965                 # surrounded by symbols which may be considered word breaks.
1966                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1967                         return $name;
1968                 }
1969
1970                 # Split database and table into proper variables.
1971                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
1972
1973                 # Quote $table and apply the prefix if not quoted.
1974                 # $tableName might be empty if this is called from Database::replaceVars()
1975                 $tableName = "{$prefix}{$table}";
1976                 if ( $format === 'quoted'
1977                         && !$this->isQuotedIdentifier( $tableName )
1978                         && $tableName !== ''
1979                 ) {
1980                         $tableName = $this->addIdentifierQuotes( $tableName );
1981                 }
1982
1983                 # Quote $schema and $database and merge them with the table name if needed
1984                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
1985                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
1986
1987                 return $tableName;
1988         }
1989
1990         /**
1991          * Get the table components needed for a query given the currently selected database
1992          *
1993          * @param string $name Table name in the form of db.schema.table, db.table, or table
1994          * @return array (DB name or "" for default, schema name, table prefix, table name)
1995          */
1996         protected function qualifiedTableComponents( $name ) {
1997                 # We reverse the explode so that database.table and table both output the correct table.
1998                 $dbDetails = explode( '.', $name, 3 );
1999                 if ( count( $dbDetails ) == 3 ) {
2000                         list( $database, $schema, $table ) = $dbDetails;
2001                         # We don't want any prefix added in this case
2002                         $prefix = '';
2003                 } elseif ( count( $dbDetails ) == 2 ) {
2004                         list( $database, $table ) = $dbDetails;
2005                         # We don't want any prefix added in this case
2006                         $prefix = '';
2007                         # In dbs that support it, $database may actually be the schema
2008                         # but that doesn't affect any of the functionality here
2009                         $schema = '';
2010                 } else {
2011                         list( $table ) = $dbDetails;
2012                         if ( isset( $this->tableAliases[$table] ) ) {
2013                                 $database = $this->tableAliases[$table]['dbname'];
2014                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
2015                                         ? $this->tableAliases[$table]['schema']
2016                                         : $this->schema;
2017                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
2018                                         ? $this->tableAliases[$table]['prefix']
2019                                         : $this->tablePrefix;
2020                         } else {
2021                                 $database = '';
2022                                 $schema = $this->schema; # Default schema
2023                                 $prefix = $this->tablePrefix; # Default prefix
2024                         }
2025                 }
2026
2027                 return [ $database, $schema, $prefix, $table ];
2028         }
2029
2030         /**
2031          * @param string|null $namespace Database or schema
2032          * @param string $relation Name of table, view, sequence, etc...
2033          * @param string $format One of (raw, quoted)
2034          * @return string Relation name with quoted and merged $namespace as needed
2035          */
2036         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
2037                 if ( strlen( $namespace ) ) {
2038                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
2039                                 $namespace = $this->addIdentifierQuotes( $namespace );
2040                         }
2041                         $relation = $namespace . '.' . $relation;
2042                 }
2043
2044                 return $relation;
2045         }
2046
2047         public function tableNames() {
2048                 $inArray = func_get_args();
2049                 $retVal = [];
2050
2051                 foreach ( $inArray as $name ) {
2052                         $retVal[$name] = $this->tableName( $name );
2053                 }
2054
2055                 return $retVal;
2056         }
2057
2058         public function tableNamesN() {
2059                 $inArray = func_get_args();
2060                 $retVal = [];
2061
2062                 foreach ( $inArray as $name ) {
2063                         $retVal[] = $this->tableName( $name );
2064                 }
2065
2066                 return $retVal;
2067         }
2068
2069         /**
2070          * Get an aliased table name
2071          * e.g. tableName AS newTableName
2072          *
2073          * @param string $name Table name, see tableName()
2074          * @param string|bool $alias Alias (optional)
2075          * @return string SQL name for aliased table. Will not alias a table to its own name
2076          */
2077         protected function tableNameWithAlias( $name, $alias = false ) {
2078                 if ( !$alias || $alias == $name ) {
2079                         return $this->tableName( $name );
2080                 } else {
2081                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2082                 }
2083         }
2084
2085         /**
2086          * Gets an array of aliased table names
2087          *
2088          * @param array $tables [ [alias] => table ]
2089          * @return string[] See tableNameWithAlias()
2090          */
2091         protected function tableNamesWithAlias( $tables ) {
2092                 $retval = [];
2093                 foreach ( $tables as $alias => $table ) {
2094                         if ( is_numeric( $alias ) ) {
2095                                 $alias = $table;
2096                         }
2097                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2098                 }
2099
2100                 return $retval;
2101         }
2102
2103         /**
2104          * Get an aliased field name
2105          * e.g. fieldName AS newFieldName
2106          *
2107          * @param string $name Field name
2108          * @param string|bool $alias Alias (optional)
2109          * @return string SQL name for aliased field. Will not alias a field to its own name
2110          */
2111         protected function fieldNameWithAlias( $name, $alias = false ) {
2112                 if ( !$alias || (string)$alias === (string)$name ) {
2113                         return $name;
2114                 } else {
2115                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
2116                 }
2117         }
2118
2119         /**
2120          * Gets an array of aliased field names
2121          *
2122          * @param array $fields [ [alias] => field ]
2123          * @return string[] See fieldNameWithAlias()
2124          */
2125         protected function fieldNamesWithAlias( $fields ) {
2126                 $retval = [];
2127                 foreach ( $fields as $alias => $field ) {
2128                         if ( is_numeric( $alias ) ) {
2129                                 $alias = $field;
2130                         }
2131                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2132                 }
2133
2134                 return $retval;
2135         }
2136
2137         /**
2138          * Get the aliased table name clause for a FROM clause
2139          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2140          *
2141          * @param array $tables ( [alias] => table )
2142          * @param array $use_index Same as for select()
2143          * @param array $ignore_index Same as for select()
2144          * @param array $join_conds Same as for select()
2145          * @return string
2146          */
2147         protected function tableNamesWithIndexClauseOrJOIN(
2148                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2149         ) {
2150                 $ret = [];
2151                 $retJOIN = [];
2152                 $use_index = (array)$use_index;
2153                 $ignore_index = (array)$ignore_index;
2154                 $join_conds = (array)$join_conds;
2155
2156                 foreach ( $tables as $alias => $table ) {
2157                         if ( !is_string( $alias ) ) {
2158                                 // No alias? Set it equal to the table name
2159                                 $alias = $table;
2160                         }
2161
2162                         if ( is_array( $table ) ) {
2163                                 // A parenthesized group
2164                                 if ( count( $table ) > 1 ) {
2165                                         $joinedTable = '('
2166                                                 . $this->tableNamesWithIndexClauseOrJOIN( $table, $use_index, $ignore_index, $join_conds )
2167                                                 . ')';
2168                                 } else {
2169                                         // Degenerate case
2170                                         $innerTable = reset( $table );
2171                                         $innerAlias = key( $table );
2172                                         $joinedTable = $this->tableNameWithAlias(
2173                                                 $innerTable,
2174                                                 is_string( $innerAlias ) ? $innerAlias : $innerTable
2175                                         );
2176                                 }
2177                         } else {
2178                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2179                         }
2180
2181                         // Is there a JOIN clause for this table?
2182                         if ( isset( $join_conds[$alias] ) ) {
2183                                 list( $joinType, $conds ) = $join_conds[$alias];
2184                                 $tableClause = $joinType;
2185                                 $tableClause .= ' ' . $joinedTable;
2186                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2187                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2188                                         if ( $use != '' ) {
2189                                                 $tableClause .= ' ' . $use;
2190                                         }
2191                                 }
2192                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2193                                         $ignore = $this->ignoreIndexClause(
2194                                                 implode( ',', (array)$ignore_index[$alias] ) );
2195                                         if ( $ignore != '' ) {
2196                                                 $tableClause .= ' ' . $ignore;
2197                                         }
2198                                 }
2199                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2200                                 if ( $on != '' ) {
2201                                         $tableClause .= ' ON (' . $on . ')';
2202                                 }
2203
2204                                 $retJOIN[] = $tableClause;
2205                         } elseif ( isset( $use_index[$alias] ) ) {
2206                                 // Is there an INDEX clause for this table?
2207                                 $tableClause = $joinedTable;
2208                                 $tableClause .= ' ' . $this->useIndexClause(
2209                                                 implode( ',', (array)$use_index[$alias] )
2210                                         );
2211
2212                                 $ret[] = $tableClause;
2213                         } elseif ( isset( $ignore_index[$alias] ) ) {
2214                                 // Is there an INDEX clause for this table?
2215                                 $tableClause = $joinedTable;
2216                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2217                                                 implode( ',', (array)$ignore_index[$alias] )
2218                                         );
2219
2220                                 $ret[] = $tableClause;
2221                         } else {
2222                                 $tableClause = $joinedTable;
2223
2224                                 $ret[] = $tableClause;
2225                         }
2226                 }
2227
2228                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2229                 $implicitJoins = $ret ? implode( ',', $ret ) : "";
2230                 $explicitJoins = $retJOIN ? implode( ' ', $retJOIN ) : "";
2231
2232                 // Compile our final table clause
2233                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2234         }
2235
2236         /**
2237          * Allows for index remapping in queries where this is not consistent across DBMS
2238          *
2239          * @param string $index
2240          * @return string
2241          */
2242         protected function indexName( $index ) {
2243                 return $index;
2244         }
2245
2246         public function addQuotes( $s ) {
2247                 if ( $s instanceof Blob ) {
2248                         $s = $s->fetch();
2249                 }
2250                 if ( $s === null ) {
2251                         return 'NULL';
2252                 } elseif ( is_bool( $s ) ) {
2253                         return (int)$s;
2254                 } else {
2255                         # This will also quote numeric values. This should be harmless,
2256                         # and protects against weird problems that occur when they really
2257                         # _are_ strings such as article titles and string->number->string
2258                         # conversion is not 1:1.
2259                         return "'" . $this->strencode( $s ) . "'";
2260                 }
2261         }
2262
2263         /**
2264          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2265          * MySQL uses `backticks` while basically everything else uses double quotes.
2266          * Since MySQL is the odd one out here the double quotes are our generic
2267          * and we implement backticks in DatabaseMysqlBase.
2268          *
2269          * @param string $s
2270          * @return string
2271          */
2272         public function addIdentifierQuotes( $s ) {
2273                 return '"' . str_replace( '"', '""', $s ) . '"';
2274         }
2275
2276         /**
2277          * Returns if the given identifier looks quoted or not according to
2278          * the database convention for quoting identifiers .
2279          *
2280          * @note Do not use this to determine if untrusted input is safe.
2281          *   A malicious user can trick this function.
2282          * @param string $name
2283          * @return bool
2284          */
2285         public function isQuotedIdentifier( $name ) {
2286                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2287         }
2288
2289         /**
2290          * @param string $s
2291          * @param string $escapeChar
2292          * @return string
2293          */
2294         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2295                 return str_replace( [ $escapeChar, '%', '_' ],
2296                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2297                         $s );
2298         }
2299
2300         public function buildLike() {
2301                 $params = func_get_args();
2302
2303                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2304                         $params = $params[0];
2305                 }
2306
2307                 $s = '';
2308
2309                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2310                 // may escape backslashes, creating problems of double escaping. The `
2311                 // character has good cross-DBMS compatibility, avoiding special operators
2312                 // in MS SQL like ^ and %
2313                 $escapeChar = '`';
2314
2315                 foreach ( $params as $value ) {
2316                         if ( $value instanceof LikeMatch ) {
2317                                 $s .= $value->toString();
2318                         } else {
2319                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2320                         }
2321                 }
2322
2323                 return ' LIKE ' . $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2324         }
2325
2326         public function anyChar() {
2327                 return new LikeMatch( '_' );
2328         }
2329
2330         public function anyString() {
2331                 return new LikeMatch( '%' );
2332         }
2333
2334         public function nextSequenceValue( $seqName ) {
2335                 return null;
2336         }
2337
2338         /**
2339          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2340          * is only needed because a) MySQL must be as efficient as possible due to
2341          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2342          * which index to pick. Anyway, other databases might have different
2343          * indexes on a given table. So don't bother overriding this unless you're
2344          * MySQL.
2345          * @param string $index
2346          * @return string
2347          */
2348         public function useIndexClause( $index ) {
2349                 return '';
2350         }
2351
2352         /**
2353          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2354          * is only needed because a) MySQL must be as efficient as possible due to
2355          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2356          * which index to pick. Anyway, other databases might have different
2357          * indexes on a given table. So don't bother overriding this unless you're
2358          * MySQL.
2359          * @param string $index
2360          * @return string
2361          */
2362         public function ignoreIndexClause( $index ) {
2363                 return '';
2364         }
2365
2366         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2367                 if ( count( $rows ) == 0 ) {
2368                         return;
2369                 }
2370
2371                 // Single row case
2372                 if ( !is_array( reset( $rows ) ) ) {
2373                         $rows = [ $rows ];
2374                 }
2375
2376                 try {
2377                         $this->startAtomic( $fname );
2378                         $affectedRowCount = 0;
2379                         foreach ( $rows as $row ) {
2380                                 // Delete rows which collide with this one
2381                                 $indexWhereClauses = [];
2382                                 foreach ( $uniqueIndexes as $index ) {
2383                                         $indexColumns = (array)$index;
2384                                         $indexRowValues = array_intersect_key( $row, array_flip( $indexColumns ) );
2385                                         if ( count( $indexRowValues ) != count( $indexColumns ) ) {
2386                                                 throw new DBUnexpectedError(
2387                                                         $this,
2388                                                         'New record does not provide all values for unique key (' .
2389                                                         implode( ', ', $indexColumns ) . ')'
2390                                                 );
2391                                         } elseif ( in_array( null, $indexRowValues, true ) ) {
2392                                                 throw new DBUnexpectedError(
2393                                                         $this,
2394                                                         'New record has a null value for unique key (' .
2395                                                         implode( ', ', $indexColumns ) . ')'
2396                                                 );
2397                                         }
2398                                         $indexWhereClauses[] = $this->makeList( $indexRowValues, LIST_AND );
2399                                 }
2400
2401                                 if ( $indexWhereClauses ) {
2402                                         $this->delete( $table, $this->makeList( $indexWhereClauses, LIST_OR ), $fname );
2403                                         $affectedRowCount += $this->affectedRows();
2404                                 }
2405
2406                                 // Now insert the row
2407                                 $this->insert( $table, $row, $fname );
2408                                 $affectedRowCount += $this->affectedRows();
2409                         }
2410                         $this->endAtomic( $fname );
2411                         $this->affectedRowCount = $affectedRowCount;
2412                 } catch ( Exception $e ) {
2413                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2414                         throw $e;
2415                 }
2416         }
2417
2418         /**
2419          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2420          * statement.
2421          *
2422          * @param string $table Table name
2423          * @param array|string $rows Row(s) to insert
2424          * @param string $fname Caller function name
2425          *
2426          * @return ResultWrapper
2427          */
2428         protected function nativeReplace( $table, $rows, $fname ) {
2429                 $table = $this->tableName( $table );
2430
2431                 # Single row case
2432                 if ( !is_array( reset( $rows ) ) ) {
2433                         $rows = [ $rows ];
2434                 }
2435
2436                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2437                 $first = true;
2438
2439                 foreach ( $rows as $row ) {
2440                         if ( $first ) {
2441                                 $first = false;
2442                         } else {
2443                                 $sql .= ',';
2444                         }
2445
2446                         $sql .= '(' . $this->makeList( $row ) . ')';
2447                 }
2448
2449                 return $this->query( $sql, $fname );
2450         }
2451
2452         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2453                 $fname = __METHOD__
2454         ) {
2455                 if ( !count( $rows ) ) {
2456                         return true; // nothing to do
2457                 }
2458
2459                 if ( !is_array( reset( $rows ) ) ) {
2460                         $rows = [ $rows ];
2461                 }
2462
2463                 if ( count( $uniqueIndexes ) ) {
2464                         $clauses = []; // list WHERE clauses that each identify a single row
2465                         foreach ( $rows as $row ) {
2466                                 foreach ( $uniqueIndexes as $index ) {
2467                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2468                                         $rowKey = []; // unique key to this row
2469                                         foreach ( $index as $column ) {
2470                                                 $rowKey[$column] = $row[$column];
2471                                         }
2472                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2473                                 }
2474                         }
2475                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2476                 } else {
2477                         $where = false;
2478                 }
2479
2480                 $affectedRowCount = 0;
2481                 try {
2482                         $this->startAtomic( $fname );
2483                         # Update any existing conflicting row(s)
2484                         if ( $where !== false ) {
2485                                 $ok = $this->update( $table, $set, $where, $fname );
2486                                 $affectedRowCount += $this->affectedRows();
2487                         } else {
2488                                 $ok = true;
2489                         }
2490                         # Now insert any non-conflicting row(s)
2491                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2492                         $affectedRowCount += $this->affectedRows();
2493                         $this->endAtomic( $fname );
2494                         $this->affectedRowCount = $affectedRowCount;
2495                 } catch ( Exception $e ) {
2496                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2497                         throw $e;
2498                 }
2499
2500                 return $ok;
2501         }
2502
2503         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2504                 $fname = __METHOD__
2505         ) {
2506                 if ( !$conds ) {
2507                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2508                 }
2509
2510                 $delTable = $this->tableName( $delTable );
2511                 $joinTable = $this->tableName( $joinTable );
2512                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2513                 if ( $conds != '*' ) {
2514                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2515                 }
2516                 $sql .= ')';
2517
2518                 $this->query( $sql, $fname );
2519         }
2520
2521         public function textFieldSize( $table, $field ) {
2522                 $table = $this->tableName( $table );
2523                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2524                 $res = $this->query( $sql, __METHOD__ );
2525                 $row = $this->fetchObject( $res );
2526
2527                 $m = [];
2528
2529                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2530                         $size = $m[1];
2531                 } else {
2532                         $size = -1;
2533                 }
2534
2535                 return $size;
2536         }
2537
2538         public function delete( $table, $conds, $fname = __METHOD__ ) {
2539                 if ( !$conds ) {
2540                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2541                 }
2542
2543                 $table = $this->tableName( $table );
2544                 $sql = "DELETE FROM $table";
2545
2546                 if ( $conds != '*' ) {
2547                         if ( is_array( $conds ) ) {
2548                                 $conds = $this->makeList( $conds, self::LIST_AND );
2549                         }
2550                         $sql .= ' WHERE ' . $conds;
2551                 }
2552
2553                 return $this->query( $sql, $fname );
2554         }
2555
2556         final public function insertSelect(
2557                 $destTable, $srcTable, $varMap, $conds,
2558                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2559         ) {
2560                 static $hints = [ 'NO_AUTO_COLUMNS' ];
2561
2562                 $insertOptions = (array)$insertOptions;
2563                 $selectOptions = (array)$selectOptions;
2564
2565                 if ( $this->cliMode && $this->isInsertSelectSafe( $insertOptions, $selectOptions ) ) {
2566                         // For massive migrations with downtime, we don't want to select everything
2567                         // into memory and OOM, so do all this native on the server side if possible.
2568                         return $this->nativeInsertSelect(
2569                                 $destTable,
2570                                 $srcTable,
2571                                 $varMap,
2572                                 $conds,
2573                                 $fname,
2574                                 array_diff( $insertOptions, $hints ),
2575                                 $selectOptions,
2576                                 $selectJoinConds
2577                         );
2578                 }
2579
2580                 return $this->nonNativeInsertSelect(
2581                         $destTable,
2582                         $srcTable,
2583                         $varMap,
2584                         $conds,
2585                         $fname,
2586                         array_diff( $insertOptions, $hints ),
2587                         $selectOptions,
2588                         $selectJoinConds
2589                 );
2590         }
2591
2592         /**
2593          * @param array $insertOptions INSERT options
2594          * @param array $selectOptions SELECT options
2595          * @return bool Whether an INSERT SELECT with these options will be replication safe
2596          * @since 1.31
2597          */
2598         protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
2599                 return true;
2600         }
2601
2602         /**
2603          * Implementation of insertSelect() based on select() and insert()
2604          *
2605          * @see IDatabase::insertSelect()
2606          * @since 1.30
2607          * @param string $destTable
2608          * @param string|array $srcTable
2609          * @param array $varMap
2610          * @param array $conds
2611          * @param string $fname
2612          * @param array $insertOptions
2613          * @param array $selectOptions
2614          * @param array $selectJoinConds
2615          * @return bool
2616          */
2617         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2618                 $fname = __METHOD__,
2619                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2620         ) {
2621                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
2622                 // on only the master (without needing row-based-replication). It also makes it easy to
2623                 // know how big the INSERT is going to be.
2624                 $fields = [];
2625                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
2626                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
2627                 }
2628                 $selectOptions[] = 'FOR UPDATE';
2629                 $res = $this->select(
2630                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
2631                 );
2632                 if ( !$res ) {
2633                         return false;
2634                 }
2635
2636                 try {
2637                         $affectedRowCount = 0;
2638                         $this->startAtomic( $fname );
2639                         $rows = [];
2640                         $ok = true;
2641                         foreach ( $res as $row ) {
2642                                 $rows[] = (array)$row;
2643
2644                                 // Avoid inserts that are too huge
2645                                 if ( count( $rows ) >= $this->nonNativeInsertSelectBatchSize ) {
2646                                         $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
2647                                         if ( !$ok ) {
2648                                                 break;
2649                                         }
2650                                         $affectedRowCount += $this->affectedRows();
2651                                         $rows = [];
2652                                 }
2653                         }
2654                         if ( $rows && $ok ) {
2655                                 $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
2656                                 if ( $ok ) {
2657                                         $affectedRowCount += $this->affectedRows();
2658                                 }
2659                         }
2660                         if ( $ok ) {
2661                                 $this->endAtomic( $fname );
2662                                 $this->affectedRowCount = $affectedRowCount;
2663                         } else {
2664                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
2665                         }
2666                         return $ok;
2667                 } catch ( Exception $e ) {
2668                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2669                         throw $e;
2670                 }
2671         }
2672
2673         /**
2674          * Native server-side implementation of insertSelect() for situations where
2675          * we don't want to select everything into memory
2676          *
2677          * @see IDatabase::insertSelect()
2678          * @param string $destTable
2679          * @param string|array $srcTable
2680          * @param array $varMap
2681          * @param array $conds
2682          * @param string $fname
2683          * @param array $insertOptions
2684          * @param array $selectOptions
2685          * @param array $selectJoinConds
2686          * @return bool
2687          */
2688         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2689                 $fname = __METHOD__,
2690                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2691         ) {
2692                 $destTable = $this->tableName( $destTable );
2693
2694                 if ( !is_array( $insertOptions ) ) {
2695                         $insertOptions = [ $insertOptions ];
2696                 }
2697
2698                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2699
2700                 $selectSql = $this->selectSQLText(
2701                         $srcTable,
2702                         array_values( $varMap ),
2703                         $conds,
2704                         $fname,
2705                         $selectOptions,
2706                         $selectJoinConds
2707                 );
2708
2709                 $sql = "INSERT $insertOptions" .
2710                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
2711                         $selectSql;
2712
2713                 return $this->query( $sql, $fname );
2714         }
2715
2716         /**
2717          * Construct a LIMIT query with optional offset. This is used for query
2718          * pages. The SQL should be adjusted so that only the first $limit rows
2719          * are returned. If $offset is provided as well, then the first $offset
2720          * rows should be discarded, and the next $limit rows should be returned.
2721          * If the result of the query is not ordered, then the rows to be returned
2722          * are theoretically arbitrary.
2723          *
2724          * $sql is expected to be a SELECT, if that makes a difference.
2725          *
2726          * The version provided by default works in MySQL and SQLite. It will very
2727          * likely need to be overridden for most other DBMSes.
2728          *
2729          * @param string $sql SQL query we will append the limit too
2730          * @param int $limit The SQL limit
2731          * @param int|bool $offset The SQL offset (default false)
2732          * @throws DBUnexpectedError
2733          * @return string
2734          */
2735         public function limitResult( $sql, $limit, $offset = false ) {
2736                 if ( !is_numeric( $limit ) ) {
2737                         throw new DBUnexpectedError( $this,
2738                                 "Invalid non-numeric limit passed to limitResult()\n" );
2739                 }
2740
2741                 return "$sql LIMIT "
2742                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2743                 . "{$limit} ";
2744         }
2745
2746         public function unionSupportsOrderAndLimit() {
2747                 return true; // True for almost every DB supported
2748         }
2749
2750         public function unionQueries( $sqls, $all ) {
2751                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2752
2753                 return '(' . implode( $glue, $sqls ) . ')';
2754         }
2755
2756         public function unionConditionPermutations(
2757                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
2758                 $options = [], $join_conds = []
2759         ) {
2760                 // First, build the Cartesian product of $permute_conds
2761                 $conds = [ [] ];
2762                 foreach ( $permute_conds as $field => $values ) {
2763                         if ( !$values ) {
2764                                 // Skip empty $values
2765                                 continue;
2766                         }
2767                         $values = array_unique( $values ); // For sanity
2768                         $newConds = [];
2769                         foreach ( $conds as $cond ) {
2770                                 foreach ( $values as $value ) {
2771                                         $cond[$field] = $value;
2772                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
2773                                 }
2774                         }
2775                         $conds = $newConds;
2776                 }
2777
2778                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
2779
2780                 // If there's just one condition and no subordering, hand off to
2781                 // selectSQLText directly.
2782                 if ( count( $conds ) === 1 &&
2783                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
2784                 ) {
2785                         return $this->selectSQLText(
2786                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
2787                         );
2788                 }
2789
2790                 // Otherwise, we need to pull out the order and limit to apply after
2791                 // the union. Then build the SQL queries for each set of conditions in
2792                 // $conds. Then union them together (using UNION ALL, because the
2793                 // product *should* already be distinct).
2794                 $orderBy = $this->makeOrderBy( $options );
2795                 $limit = isset( $options['LIMIT'] ) ? $options['LIMIT'] : null;
2796                 $offset = isset( $options['OFFSET'] ) ? $options['OFFSET'] : false;
2797                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
2798                 if ( !$this->unionSupportsOrderAndLimit() ) {
2799                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
2800                 } else {
2801                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
2802                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
2803                         }
2804                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
2805                                 // We need to increase the limit by the offset rather than
2806                                 // using the offset directly, otherwise it'll skip incorrectly
2807                                 // in the subqueries.
2808                                 $options['LIMIT'] = $limit + $offset;
2809                                 unset( $options['OFFSET'] );
2810                         }
2811                 }
2812
2813                 $sqls = [];
2814                 foreach ( $conds as $cond ) {
2815                         $sqls[] = $this->selectSQLText(
2816                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
2817                         );
2818                 }
2819                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
2820                 if ( $limit !== null ) {
2821                         $sql = $this->limitResult( $sql, $limit, $offset );
2822                 }
2823
2824                 return $sql;
2825         }
2826
2827         public function conditional( $cond, $trueVal, $falseVal ) {
2828                 if ( is_array( $cond ) ) {
2829                         $cond = $this->makeList( $cond, self::LIST_AND );
2830                 }
2831
2832                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2833         }
2834
2835         public function strreplace( $orig, $old, $new ) {
2836                 return "REPLACE({$orig}, {$old}, {$new})";
2837         }
2838
2839         public function getServerUptime() {
2840                 return 0;
2841         }
2842
2843         public function wasDeadlock() {
2844                 return false;
2845         }
2846
2847         public function wasLockTimeout() {
2848                 return false;
2849         }
2850
2851         public function wasErrorReissuable() {
2852                 return false;
2853         }
2854
2855         public function wasReadOnlyError() {
2856                 return false;
2857         }
2858
2859         /**
2860          * Do not use this method outside of Database/DBError classes
2861          *
2862          * @param int|string $errno
2863          * @return bool Whether the given query error was a connection drop
2864          */
2865         public function wasConnectionError( $errno ) {
2866                 return false;
2867         }
2868
2869         public function deadlockLoop() {
2870                 $args = func_get_args();
2871                 $function = array_shift( $args );
2872                 $tries = self::DEADLOCK_TRIES;
2873
2874                 $this->begin( __METHOD__ );
2875
2876                 $retVal = null;
2877                 /** @var Exception $e */
2878                 $e = null;
2879                 do {
2880                         try {
2881                                 $retVal = call_user_func_array( $function, $args );
2882                                 break;
2883                         } catch ( DBQueryError $e ) {
2884                                 if ( $this->wasDeadlock() ) {
2885                                         // Retry after a randomized delay
2886                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
2887                                 } else {
2888                                         // Throw the error back up
2889                                         throw $e;
2890                                 }
2891                         }
2892                 } while ( --$tries > 0 );
2893
2894                 if ( $tries <= 0 ) {
2895                         // Too many deadlocks; give up
2896                         $this->rollback( __METHOD__ );
2897                         throw $e;
2898                 } else {
2899                         $this->commit( __METHOD__ );
2900
2901                         return $retVal;
2902                 }
2903         }
2904
2905         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2906                 # Real waits are implemented in the subclass.
2907                 return 0;
2908         }
2909
2910         public function getReplicaPos() {
2911                 # Stub
2912                 return false;
2913         }
2914
2915         public function getMasterPos() {
2916                 # Stub
2917                 return false;
2918         }
2919
2920         public function serverIsReadOnly() {
2921                 return false;
2922         }
2923
2924         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
2925                 if ( !$this->trxLevel ) {
2926                         throw new DBUnexpectedError( $this, "No transaction is active." );
2927                 }
2928                 $this->trxEndCallbacks[] = [ $callback, $fname ];
2929         }
2930
2931         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
2932                 $this->trxIdleCallbacks[] = [ $callback, $fname ];
2933                 if ( !$this->trxLevel ) {
2934                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
2935                 }
2936         }
2937
2938         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
2939                 if ( $this->trxLevel || $this->getFlag( self::DBO_TRX ) ) {
2940                         // As long as DBO_TRX is set, writes will accumulate until the load balancer issues
2941                         // an implicit commit of all peer databases. This is true even if a transaction has
2942                         // not yet been triggered by writes; make sure $callback runs *after* any such writes.
2943                         $this->trxPreCommitCallbacks[] = [ $callback, $fname ];
2944                 } else {
2945                         // No transaction is active nor will start implicitly, so make one for this callback
2946                         $this->startAtomic( __METHOD__ );
2947                         try {
2948                                 call_user_func( $callback );
2949                                 $this->endAtomic( __METHOD__ );
2950                         } catch ( Exception $e ) {
2951                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2952                                 throw $e;
2953                         }
2954                 }
2955         }
2956
2957         final public function setTransactionListener( $name, callable $callback = null ) {
2958                 if ( $callback ) {
2959                         $this->trxRecurringCallbacks[$name] = $callback;
2960                 } else {
2961                         unset( $this->trxRecurringCallbacks[$name] );
2962                 }
2963         }
2964
2965         /**
2966          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
2967          *
2968          * This method should not be used outside of Database/LoadBalancer
2969          *
2970          * @param bool $suppress
2971          * @since 1.28
2972          */
2973         final public function setTrxEndCallbackSuppression( $suppress ) {
2974                 $this->trxEndCallbacksSuppressed = $suppress;
2975         }
2976
2977         /**
2978          * Actually run and consume any "on transaction idle/resolution" callbacks.
2979          *
2980          * This method should not be used outside of Database/LoadBalancer
2981          *
2982          * @param int $trigger IDatabase::TRIGGER_* constant
2983          * @since 1.20
2984          * @throws Exception
2985          */
2986         public function runOnTransactionIdleCallbacks( $trigger ) {
2987                 if ( $this->trxEndCallbacksSuppressed ) {
2988                         return;
2989                 }
2990
2991                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
2992                 /** @var Exception $e */
2993                 $e = null; // first exception
2994                 do { // callbacks may add callbacks :)
2995                         $callbacks = array_merge(
2996                                 $this->trxIdleCallbacks,
2997                                 $this->trxEndCallbacks // include "transaction resolution" callbacks
2998                         );
2999                         $this->trxIdleCallbacks = []; // consumed (and recursion guard)
3000                         $this->trxEndCallbacks = []; // consumed (recursion guard)
3001                         foreach ( $callbacks as $callback ) {
3002                                 try {
3003                                         list( $phpCallback ) = $callback;
3004                                         $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
3005                                         call_user_func_array( $phpCallback, [ $trigger ] );
3006                                         if ( $autoTrx ) {
3007                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
3008                                         } else {
3009                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
3010                                         }
3011                                 } catch ( Exception $ex ) {
3012                                         call_user_func( $this->errorLogger, $ex );
3013                                         $e = $e ?: $ex;
3014                                         // Some callbacks may use startAtomic/endAtomic, so make sure
3015                                         // their transactions are ended so other callbacks don't fail
3016                                         if ( $this->trxLevel() ) {
3017                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
3018                                         }
3019                                 }
3020                         }
3021                 } while ( count( $this->trxIdleCallbacks ) );
3022
3023                 if ( $e instanceof Exception ) {
3024                         throw $e; // re-throw any first exception
3025                 }
3026         }
3027
3028         /**
3029          * Actually run and consume any "on transaction pre-commit" callbacks.
3030          *
3031          * This method should not be used outside of Database/LoadBalancer
3032          *
3033          * @since 1.22
3034          * @throws Exception
3035          */
3036         public function runOnTransactionPreCommitCallbacks() {
3037                 $e = null; // first exception
3038                 do { // callbacks may add callbacks :)
3039                         $callbacks = $this->trxPreCommitCallbacks;
3040                         $this->trxPreCommitCallbacks = []; // consumed (and recursion guard)
3041                         foreach ( $callbacks as $callback ) {
3042                                 try {
3043                                         list( $phpCallback ) = $callback;
3044                                         call_user_func( $phpCallback );
3045                                 } catch ( Exception $ex ) {
3046                                         call_user_func( $this->errorLogger, $ex );
3047                                         $e = $e ?: $ex;
3048                                 }
3049                         }
3050                 } while ( count( $this->trxPreCommitCallbacks ) );
3051
3052                 if ( $e instanceof Exception ) {
3053                         throw $e; // re-throw any first exception
3054                 }
3055         }
3056
3057         /**
3058          * Actually run any "transaction listener" callbacks.
3059          *
3060          * This method should not be used outside of Database/LoadBalancer
3061          *
3062          * @param int $trigger IDatabase::TRIGGER_* constant
3063          * @throws Exception
3064          * @since 1.20
3065          */
3066         public function runTransactionListenerCallbacks( $trigger ) {
3067                 if ( $this->trxEndCallbacksSuppressed ) {
3068                         return;
3069                 }
3070
3071                 /** @var Exception $e */
3072                 $e = null; // first exception
3073
3074                 foreach ( $this->trxRecurringCallbacks as $phpCallback ) {
3075                         try {
3076                                 $phpCallback( $trigger, $this );
3077                         } catch ( Exception $ex ) {
3078                                 call_user_func( $this->errorLogger, $ex );
3079                                 $e = $e ?: $ex;
3080                         }
3081                 }
3082
3083                 if ( $e instanceof Exception ) {
3084                         throw $e; // re-throw any first exception
3085                 }
3086         }
3087
3088         final public function startAtomic( $fname = __METHOD__ ) {
3089                 if ( !$this->trxLevel ) {
3090                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
3091                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
3092                         // in all changes being in one transaction to keep requests transactional.
3093                         if ( !$this->getFlag( self::DBO_TRX ) ) {
3094                                 $this->trxAutomaticAtomic = true;
3095                         }
3096                 }
3097
3098                 $this->trxAtomicLevels[] = $fname;
3099         }
3100
3101         final public function endAtomic( $fname = __METHOD__ ) {
3102                 if ( !$this->trxLevel ) {
3103                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
3104                 }
3105                 if ( !$this->trxAtomicLevels ||
3106                         array_pop( $this->trxAtomicLevels ) !== $fname
3107                 ) {
3108                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
3109                 }
3110
3111                 if ( !$this->trxAtomicLevels && $this->trxAutomaticAtomic ) {
3112                         $this->commit( $fname, self::FLUSHING_INTERNAL );
3113                 }
3114         }
3115
3116         final public function doAtomicSection( $fname, callable $callback ) {
3117                 $this->startAtomic( $fname );
3118                 try {
3119                         $res = call_user_func_array( $callback, [ $this, $fname ] );
3120                 } catch ( Exception $e ) {
3121                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
3122                         throw $e;
3123                 }
3124                 $this->endAtomic( $fname );
3125
3126                 return $res;
3127         }
3128
3129         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
3130                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
3131                 if ( $this->trxLevel ) {
3132                         if ( $this->trxAtomicLevels ) {
3133                                 $levels = implode( ', ', $this->trxAtomicLevels );
3134                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
3135                                 throw new DBUnexpectedError( $this, $msg );
3136                         } elseif ( !$this->trxAutomatic ) {
3137                                 $msg = "$fname: Explicit transaction already active (from {$this->trxFname}).";
3138                                 throw new DBUnexpectedError( $this, $msg );
3139                         } else {
3140                                 // @TODO: make this an exception at some point
3141                                 $msg = "$fname: Implicit transaction already active (from {$this->trxFname}).";
3142                                 $this->queryLogger->error( $msg );
3143                                 return; // join the main transaction set
3144                         }
3145                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
3146                         // @TODO: make this an exception at some point
3147                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
3148                         $this->queryLogger->error( $msg );
3149                         return; // let any writes be in the main transaction
3150                 }
3151
3152                 // Avoid fatals if close() was called
3153                 $this->assertOpen();
3154
3155                 $this->doBegin( $fname );
3156                 $this->trxTimestamp = microtime( true );
3157                 $this->trxFname = $fname;
3158                 $this->trxDoneWrites = false;
3159                 $this->trxAutomaticAtomic = false;
3160                 $this->trxAtomicLevels = [];
3161                 $this->trxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
3162                 $this->trxWriteDuration = 0.0;
3163                 $this->trxWriteQueryCount = 0;
3164                 $this->trxWriteAffectedRows = 0;
3165                 $this->trxWriteAdjDuration = 0.0;
3166                 $this->trxWriteAdjQueryCount = 0;
3167                 $this->trxWriteCallers = [];
3168                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
3169                 // Get an estimate of the replica DB lag before then, treating estimate staleness
3170                 // as lag itself just to be safe
3171                 $status = $this->getApproximateLagStatus();
3172                 $this->trxReplicaLag = $status['lag'] + ( microtime( true ) - $status['since'] );
3173                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
3174                 // caller will think its OK to muck around with the transaction just because startAtomic()
3175                 // has not yet completed (e.g. setting trxAtomicLevels).
3176                 $this->trxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
3177         }
3178
3179         /**
3180          * Issues the BEGIN command to the database server.
3181          *
3182          * @see Database::begin()
3183          * @param string $fname
3184          */
3185         protected function doBegin( $fname ) {
3186                 $this->query( 'BEGIN', $fname );
3187                 $this->trxLevel = 1;
3188         }
3189
3190         final public function commit( $fname = __METHOD__, $flush = '' ) {
3191                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3192                         // There are still atomic sections open. This cannot be ignored
3193                         $levels = implode( ', ', $this->trxAtomicLevels );
3194                         throw new DBUnexpectedError(
3195                                 $this,
3196                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3197                         );
3198                 }
3199
3200                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3201                         if ( !$this->trxLevel ) {
3202                                 return; // nothing to do
3203                         } elseif ( !$this->trxAutomatic ) {
3204                                 throw new DBUnexpectedError(
3205                                         $this,
3206                                         "$fname: Flushing an explicit transaction, getting out of sync."
3207                                 );
3208                         }
3209                 } else {
3210                         if ( !$this->trxLevel ) {
3211                                 $this->queryLogger->error(
3212                                         "$fname: No transaction to commit, something got out of sync." );
3213                                 return; // nothing to do
3214                         } elseif ( $this->trxAutomatic ) {
3215                                 // @TODO: make this an exception at some point
3216                                 $msg = "$fname: Explicit commit of implicit transaction.";
3217                                 $this->queryLogger->error( $msg );
3218                                 return; // wait for the main transaction set commit round
3219                         }
3220                 }
3221
3222                 // Avoid fatals if close() was called
3223                 $this->assertOpen();
3224
3225                 $this->runOnTransactionPreCommitCallbacks();
3226                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3227                 $this->doCommit( $fname );
3228                 if ( $this->trxDoneWrites ) {
3229                         $this->lastWriteTime = microtime( true );
3230                         $this->trxProfiler->transactionWritingOut(
3231                                 $this->server,
3232                                 $this->dbName,
3233                                 $this->trxShortId,
3234                                 $writeTime,
3235                                 $this->trxWriteAffectedRows
3236                         );
3237                 }
3238
3239                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3240                 $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3241         }
3242
3243         /**
3244          * Issues the COMMIT command to the database server.
3245          *
3246          * @see Database::commit()
3247          * @param string $fname
3248          */
3249         protected function doCommit( $fname ) {
3250                 if ( $this->trxLevel ) {
3251                         $this->query( 'COMMIT', $fname );
3252                         $this->trxLevel = 0;
3253                 }
3254         }
3255
3256         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3257                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3258                         if ( !$this->trxLevel ) {
3259                                 return; // nothing to do
3260                         }
3261                 } else {
3262                         if ( !$this->trxLevel ) {
3263                                 $this->queryLogger->error(
3264                                         "$fname: No transaction to rollback, something got out of sync." );
3265                                 return; // nothing to do
3266                         } elseif ( $this->getFlag( self::DBO_TRX ) ) {
3267                                 throw new DBUnexpectedError(
3268                                         $this,
3269                                         "$fname: Expected mass rollback of all peer databases (DBO_TRX set)."
3270                                 );
3271                         }
3272                 }
3273
3274                 // Avoid fatals if close() was called
3275                 $this->assertOpen();
3276
3277                 $this->doRollback( $fname );
3278                 $this->trxAtomicLevels = [];
3279                 if ( $this->trxDoneWrites ) {
3280                         $this->trxProfiler->transactionWritingOut(
3281                                 $this->server,
3282                                 $this->dbName,
3283                                 $this->trxShortId
3284                         );
3285                 }
3286
3287                 $this->trxIdleCallbacks = []; // clear
3288                 $this->trxPreCommitCallbacks = []; // clear
3289                 try {
3290                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
3291                 } catch ( Exception $e ) {
3292                         // already logged; finish and let LoadBalancer move on during mass-rollback
3293                 }
3294                 try {
3295                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
3296                 } catch ( Exception $e ) {
3297                         // already logged; let LoadBalancer move on during mass-rollback
3298                 }
3299
3300                 $this->affectedRowCount = 0; // for the sake of consistency
3301         }
3302
3303         /**
3304          * Issues the ROLLBACK command to the database server.
3305          *
3306          * @see Database::rollback()
3307          * @param string $fname
3308          */
3309         protected function doRollback( $fname ) {
3310                 if ( $this->trxLevel ) {
3311                         # Disconnects cause rollback anyway, so ignore those errors
3312                         $ignoreErrors = true;
3313                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
3314                         $this->trxLevel = 0;
3315                 }
3316         }
3317
3318         public function flushSnapshot( $fname = __METHOD__ ) {
3319                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
3320                         // This only flushes transactions to clear snapshots, not to write data
3321                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3322                         throw new DBUnexpectedError(
3323                                 $this,
3324                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
3325                         );
3326                 }
3327
3328                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3329         }
3330
3331         public function explicitTrxActive() {
3332                 return $this->trxLevel && ( $this->trxAtomicLevels || !$this->trxAutomatic );
3333         }
3334
3335         public function duplicateTableStructure(
3336                 $oldName, $newName, $temporary = false, $fname = __METHOD__
3337         ) {
3338                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3339         }
3340
3341         public function listTables( $prefix = null, $fname = __METHOD__ ) {
3342                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3343         }
3344
3345         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3346                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3347         }
3348
3349         public function timestamp( $ts = 0 ) {
3350                 $t = new ConvertibleTimestamp( $ts );
3351                 // Let errors bubble up to avoid putting garbage in the DB
3352                 return $t->getTimestamp( TS_MW );
3353         }
3354
3355         public function timestampOrNull( $ts = null ) {
3356                 if ( is_null( $ts ) ) {
3357                         return null;
3358                 } else {
3359                         return $this->timestamp( $ts );
3360                 }
3361         }
3362
3363         public function affectedRows() {
3364                 return ( $this->affectedRowCount === null )
3365                         ? $this->fetchAffectedRowCount() // default to driver value
3366                         : $this->affectedRowCount;
3367         }
3368
3369         /**
3370          * @return int Number of retrieved rows according to the driver
3371          */
3372         abstract protected function fetchAffectedRowCount();
3373
3374         /**
3375          * Take the result from a query, and wrap it in a ResultWrapper if
3376          * necessary. Boolean values are passed through as is, to indicate success
3377          * of write queries or failure.
3378          *
3379          * Once upon a time, Database::query() returned a bare MySQL result
3380          * resource, and it was necessary to call this function to convert it to
3381          * a wrapper. Nowadays, raw database objects are never exposed to external
3382          * callers, so this is unnecessary in external code.
3383          *
3384          * @param bool|ResultWrapper|resource|object $result
3385          * @return bool|ResultWrapper
3386          */
3387         protected function resultObject( $result ) {
3388                 if ( !$result ) {
3389                         return false;
3390                 } elseif ( $result instanceof ResultWrapper ) {
3391                         return $result;
3392                 } elseif ( $result === true ) {
3393                         // Successful write query
3394                         return $result;
3395                 } else {
3396                         return new ResultWrapper( $this, $result );
3397                 }
3398         }
3399
3400         public function ping( &$rtt = null ) {
3401                 // Avoid hitting the server if it was hit recently
3402                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
3403                         if ( !func_num_args() || $this->rttEstimate > 0 ) {
3404                                 $rtt = $this->rttEstimate;
3405                                 return true; // don't care about $rtt
3406                         }
3407                 }
3408
3409                 // This will reconnect if possible or return false if not
3410                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
3411                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
3412                 $this->restoreFlags( self::RESTORE_PRIOR );
3413
3414                 if ( $ok ) {
3415                         $rtt = $this->rttEstimate;
3416                 }
3417
3418                 return $ok;
3419         }
3420
3421         /**
3422          * Close existing database connection and open a new connection
3423          *
3424          * @return bool True if new connection is opened successfully, false if error
3425          */
3426         protected function reconnect() {
3427                 $this->closeConnection();
3428                 $this->opened = false;
3429                 $this->conn = false;
3430                 try {
3431                         $this->open( $this->server, $this->user, $this->password, $this->dbName );
3432                         $this->lastPing = microtime( true );
3433                         $ok = true;
3434                 } catch ( DBConnectionError $e ) {
3435                         $ok = false;
3436                 }
3437
3438                 return $ok;
3439         }
3440
3441         public function getSessionLagStatus() {
3442                 return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
3443         }
3444
3445         /**
3446          * Get the replica DB lag when the current transaction started
3447          *
3448          * This is useful when transactions might use snapshot isolation
3449          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
3450          * is this lag plus transaction duration. If they don't, it is still
3451          * safe to be pessimistic. This returns null if there is no transaction.
3452          *
3453          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
3454          * @since 1.27
3455          */
3456         protected function getTransactionLagStatus() {
3457                 return $this->trxLevel
3458                         ? [ 'lag' => $this->trxReplicaLag, 'since' => $this->trxTimestamp() ]
3459                         : null;
3460         }
3461
3462         /**
3463          * Get a replica DB lag estimate for this server
3464          *
3465          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
3466          * @since 1.27
3467          */
3468         protected function getApproximateLagStatus() {
3469                 return [
3470                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
3471                         'since' => microtime( true )
3472                 ];
3473         }
3474
3475         /**
3476          * Merge the result of getSessionLagStatus() for several DBs
3477          * using the most pessimistic values to estimate the lag of
3478          * any data derived from them in combination
3479          *
3480          * This is information is useful for caching modules
3481          *
3482          * @see WANObjectCache::set()
3483          * @see WANObjectCache::getWithSetCallback()
3484          *
3485          * @param IDatabase $db1
3486          * @param IDatabase $db2 [optional]
3487          * @return array Map of values:
3488          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3489          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3490          *   - pending: whether any of the DBs have uncommitted changes
3491          * @throws DBError
3492          * @since 1.27
3493          */
3494         public static function getCacheSetOptions( IDatabase $db1, IDatabase $db2 = null ) {
3495                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3496                 foreach ( func_get_args() as $db ) {
3497                         /** @var IDatabase $db */
3498                         $status = $db->getSessionLagStatus();
3499                         if ( $status['lag'] === false ) {
3500                                 $res['lag'] = false;
3501                         } elseif ( $res['lag'] !== false ) {
3502                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3503                         }
3504                         $res['since'] = min( $res['since'], $status['since'] );
3505                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3506                 }
3507
3508                 return $res;
3509         }
3510
3511         public function getLag() {
3512                 return 0;
3513         }
3514
3515         public function maxListLen() {
3516                 return 0;
3517         }
3518
3519         public function encodeBlob( $b ) {
3520                 return $b;
3521         }
3522
3523         public function decodeBlob( $b ) {
3524                 if ( $b instanceof Blob ) {
3525                         $b = $b->fetch();
3526                 }
3527                 return $b;
3528         }
3529
3530         public function setSessionOptions( array $options ) {
3531         }
3532
3533         public function sourceFile(
3534                 $filename,
3535                 callable $lineCallback = null,
3536                 callable $resultCallback = null,
3537                 $fname = false,
3538                 callable $inputCallback = null
3539         ) {
3540                 Wikimedia\suppressWarnings();
3541                 $fp = fopen( $filename, 'r' );
3542                 Wikimedia\restoreWarnings();
3543
3544                 if ( false === $fp ) {
3545                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
3546                 }
3547
3548                 if ( !$fname ) {
3549                         $fname = __METHOD__ . "( $filename )";
3550                 }
3551
3552                 try {
3553                         $error = $this->sourceStream(
3554                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3555                 } catch ( Exception $e ) {
3556                         fclose( $fp );
3557                         throw $e;
3558                 }
3559
3560                 fclose( $fp );
3561
3562                 return $error;
3563         }
3564
3565         public function setSchemaVars( $vars ) {
3566                 $this->schemaVars = $vars;
3567         }
3568
3569         public function sourceStream(
3570                 $fp,
3571                 callable $lineCallback = null,
3572                 callable $resultCallback = null,
3573                 $fname = __METHOD__,
3574                 callable $inputCallback = null
3575         ) {
3576                 $delimiterReset = new ScopedCallback(
3577                         function ( $delimiter ) {
3578                                 $this->delimiter = $delimiter;
3579                         },
3580                         [ $this->delimiter ]
3581                 );
3582                 $cmd = '';
3583
3584                 while ( !feof( $fp ) ) {
3585                         if ( $lineCallback ) {
3586                                 call_user_func( $lineCallback );
3587                         }
3588
3589                         $line = trim( fgets( $fp ) );
3590
3591                         if ( $line == '' ) {
3592                                 continue;
3593                         }
3594
3595                         if ( '-' == $line[0] && '-' == $line[1] ) {
3596                                 continue;
3597                         }
3598
3599                         if ( $cmd != '' ) {
3600                                 $cmd .= ' ';
3601                         }
3602
3603                         $done = $this->streamStatementEnd( $cmd, $line );
3604
3605                         $cmd .= "$line\n";
3606
3607                         if ( $done || feof( $fp ) ) {
3608                                 $cmd = $this->replaceVars( $cmd );
3609
3610                                 if ( $inputCallback ) {
3611                                         $callbackResult = call_user_func( $inputCallback, $cmd );
3612
3613                                         if ( is_string( $callbackResult ) || !$callbackResult ) {
3614                                                 $cmd = $callbackResult;
3615                                         }
3616                                 }
3617
3618                                 if ( $cmd ) {
3619                                         $res = $this->query( $cmd, $fname );
3620
3621                                         if ( $resultCallback ) {
3622                                                 call_user_func( $resultCallback, $res, $this );
3623                                         }
3624
3625                                         if ( false === $res ) {
3626                                                 $err = $this->lastError();
3627
3628                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3629                                         }
3630                                 }
3631                                 $cmd = '';
3632                         }
3633                 }
3634
3635                 ScopedCallback::consume( $delimiterReset );
3636                 return true;
3637         }
3638
3639         /**
3640          * Called by sourceStream() to check if we've reached a statement end
3641          *
3642          * @param string &$sql SQL assembled so far
3643          * @param string &$newLine New line about to be added to $sql
3644          * @return bool Whether $newLine contains end of the statement
3645          */
3646         public function streamStatementEnd( &$sql, &$newLine ) {
3647                 if ( $this->delimiter ) {
3648                         $prev = $newLine;
3649                         $newLine = preg_replace(
3650                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3651                         if ( $newLine != $prev ) {
3652                                 return true;
3653                         }
3654                 }
3655
3656                 return false;
3657         }
3658
3659         /**
3660          * Database independent variable replacement. Replaces a set of variables
3661          * in an SQL statement with their contents as given by $this->getSchemaVars().
3662          *
3663          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3664          *
3665          * - '{$var}' should be used for text and is passed through the database's
3666          *   addQuotes method.
3667          * - `{$var}` should be used for identifiers (e.g. table and database names).
3668          *   It is passed through the database's addIdentifierQuotes method which
3669          *   can be overridden if the database uses something other than backticks.
3670          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
3671          *   database's tableName method.
3672          * - / *i* / passes the name that follows through the database's indexName method.
3673          * - In all other cases, / *$var* / is left unencoded. Except for table options,
3674          *   its use should be avoided. In 1.24 and older, string encoding was applied.
3675          *
3676          * @param string $ins SQL statement to replace variables in
3677          * @return string The new SQL statement with variables replaced
3678          */
3679         protected function replaceVars( $ins ) {
3680                 $vars = $this->getSchemaVars();
3681                 return preg_replace_callback(
3682                         '!
3683                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
3684                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
3685                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
3686                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
3687                         !x',
3688                         function ( $m ) use ( $vars ) {
3689                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
3690                                 // check for both nonexistent keys *and* the empty string.
3691                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
3692                                         if ( $m[1] === 'i' ) {
3693                                                 return $this->indexName( $m[2] );
3694                                         } else {
3695                                                 return $this->tableName( $m[2] );
3696                                         }
3697                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
3698                                         return $this->addQuotes( $vars[$m[3]] );
3699                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
3700                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
3701                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
3702                                         return $vars[$m[5]];
3703                                 } else {
3704                                         return $m[0];
3705                                 }
3706                         },
3707                         $ins
3708                 );
3709         }
3710
3711         /**
3712          * Get schema variables. If none have been set via setSchemaVars(), then
3713          * use some defaults from the current object.
3714          *
3715          * @return array
3716          */
3717         protected function getSchemaVars() {
3718                 if ( $this->schemaVars ) {
3719                         return $this->schemaVars;
3720                 } else {
3721                         return $this->getDefaultSchemaVars();
3722                 }
3723         }
3724
3725         /**
3726          * Get schema variables to use if none have been set via setSchemaVars().
3727          *
3728          * Override this in derived classes to provide variables for tables.sql
3729          * and SQL patch files.
3730          *
3731          * @return array
3732          */
3733         protected function getDefaultSchemaVars() {
3734                 return [];
3735         }
3736
3737         public function lockIsFree( $lockName, $method ) {
3738                 // RDBMs methods for checking named locks may or may not count this thread itself.
3739                 // In MySQL, IS_FREE_LOCK() returns 0 if the thread already has the lock. This is
3740                 // the behavior choosen by the interface for this method.
3741                 return !isset( $this->namedLocksHeld[$lockName] );
3742         }
3743
3744         public function lock( $lockName, $method, $timeout = 5 ) {
3745                 $this->namedLocksHeld[$lockName] = 1;
3746
3747                 return true;
3748         }
3749
3750         public function unlock( $lockName, $method ) {
3751                 unset( $this->namedLocksHeld[$lockName] );
3752
3753                 return true;
3754         }
3755
3756         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
3757                 if ( $this->writesOrCallbacksPending() ) {
3758                         // This only flushes transactions to clear snapshots, not to write data
3759                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3760                         throw new DBUnexpectedError(
3761                                 $this,
3762                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
3763                         );
3764                 }
3765
3766                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
3767                         return null;
3768                 }
3769
3770                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
3771                         if ( $this->trxLevel() ) {
3772                                 // There is a good chance an exception was thrown, causing any early return
3773                                 // from the caller. Let any error handler get a chance to issue rollback().
3774                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
3775                                 $this->onTransactionResolution(
3776                                         function () use ( $lockKey, $fname ) {
3777                                                 $this->unlock( $lockKey, $fname );
3778                                         },
3779                                         $fname
3780                                 );
3781                         } else {
3782                                 $this->unlock( $lockKey, $fname );
3783                         }
3784                 } );
3785
3786                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3787
3788                 return $unlocker;
3789         }
3790
3791         public function namedLocksEnqueue() {
3792                 return false;
3793         }
3794
3795         public function tableLocksHaveTransactionScope() {
3796                 return true;
3797         }
3798
3799         final public function lockTables( array $read, array $write, $method ) {
3800                 if ( $this->writesOrCallbacksPending() ) {
3801                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
3802                 }
3803
3804                 if ( $this->tableLocksHaveTransactionScope() ) {
3805                         $this->startAtomic( $method );
3806                 }
3807
3808                 return $this->doLockTables( $read, $write, $method );
3809         }
3810
3811         /**
3812          * Helper function for lockTables() that handles the actual table locking
3813          *
3814          * @param array $read Array of tables to lock for read access
3815          * @param array $write Array of tables to lock for write access
3816          * @param string $method Name of caller
3817          * @return true
3818          */
3819         protected function doLockTables( array $read, array $write, $method ) {
3820                 return true;
3821         }
3822
3823         final public function unlockTables( $method ) {
3824                 if ( $this->tableLocksHaveTransactionScope() ) {
3825                         $this->endAtomic( $method );
3826
3827                         return true; // locks released on COMMIT/ROLLBACK
3828                 }
3829
3830                 return $this->doUnlockTables( $method );
3831         }
3832
3833         /**
3834          * Helper function for unlockTables() that handles the actual table unlocking
3835          *
3836          * @param string $method Name of caller
3837          * @return true
3838          */
3839         protected function doUnlockTables( $method ) {
3840                 return true;
3841         }
3842
3843         /**
3844          * Delete a table
3845          * @param string $tableName
3846          * @param string $fName
3847          * @return bool|ResultWrapper
3848          * @since 1.18
3849          */
3850         public function dropTable( $tableName, $fName = __METHOD__ ) {
3851                 if ( !$this->tableExists( $tableName, $fName ) ) {
3852                         return false;
3853                 }
3854                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
3855
3856                 return $this->query( $sql, $fName );
3857         }
3858
3859         public function getInfinity() {
3860                 return 'infinity';
3861         }
3862
3863         public function encodeExpiry( $expiry ) {
3864                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3865                         ? $this->getInfinity()
3866                         : $this->timestamp( $expiry );
3867         }
3868
3869         public function decodeExpiry( $expiry, $format = TS_MW ) {
3870                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
3871                         return 'infinity';
3872                 }
3873
3874                 return ConvertibleTimestamp::convert( $format, $expiry );
3875         }
3876
3877         public function setBigSelects( $value = true ) {
3878                 // no-op
3879         }
3880
3881         public function isReadOnly() {
3882                 return ( $this->getReadOnlyReason() !== false );
3883         }
3884
3885         /**
3886          * @return string|bool Reason this DB is read-only or false if it is not
3887          */
3888         protected function getReadOnlyReason() {
3889                 $reason = $this->getLBInfo( 'readOnlyReason' );
3890
3891                 return is_string( $reason ) ? $reason : false;
3892         }
3893
3894         public function setTableAliases( array $aliases ) {
3895                 $this->tableAliases = $aliases;
3896         }
3897
3898         /**
3899          * @return bool Whether a DB user is required to access the DB
3900          * @since 1.28
3901          */
3902         protected function requiresDatabaseUser() {
3903                 return true;
3904         }
3905
3906         /**
3907          * Get the underlying binding connection handle
3908          *
3909          * Makes sure the connection resource is set (disconnects and ping() failure can unset it).
3910          * This catches broken callers than catch and ignore disconnection exceptions.
3911          * Unlike checking isOpen(), this is safe to call inside of open().
3912          *
3913          * @return resource|object
3914          * @throws DBUnexpectedError
3915          * @since 1.26
3916          */
3917         protected function getBindingHandle() {
3918                 if ( !$this->conn ) {
3919                         throw new DBUnexpectedError(
3920                                 $this,
3921                                 'DB connection was already closed or the connection dropped.'
3922                         );
3923                 }
3924
3925                 return $this->conn;
3926         }
3927
3928         /**
3929          * @since 1.19
3930          * @return string
3931          */
3932         public function __toString() {
3933                 return (string)$this->conn;
3934         }
3935
3936         /**
3937          * Make sure that copies do not share the same client binding handle
3938          * @throws DBConnectionError
3939          */
3940         public function __clone() {
3941                 $this->connLogger->warning(
3942                         "Cloning " . static::class . " is not recomended; forking connection:\n" .
3943                         ( new RuntimeException() )->getTraceAsString()
3944                 );
3945
3946                 if ( $this->isOpen() ) {
3947                         // Open a new connection resource without messing with the old one
3948                         $this->opened = false;
3949                         $this->conn = false;
3950                         $this->trxEndCallbacks = []; // don't copy
3951                         $this->handleSessionLoss(); // no trx or locks anymore
3952                         $this->open( $this->server, $this->user, $this->password, $this->dbName );
3953                         $this->lastPing = microtime( true );
3954                 }
3955         }
3956
3957         /**
3958          * Called by serialize. Throw an exception when DB connection is serialized.
3959          * This causes problems on some database engines because the connection is
3960          * not restored on unserialize.
3961          */
3962         public function __sleep() {
3963                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
3964                         'the connection is not restored on wakeup.' );
3965         }
3966
3967         /**
3968          * Run a few simple sanity checks and close dangling connections
3969          */
3970         public function __destruct() {
3971                 if ( $this->trxLevel && $this->trxDoneWrites ) {
3972                         trigger_error( "Uncommitted DB writes (transaction from {$this->trxFname})." );
3973                 }
3974
3975                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
3976                 if ( $danglingWriters ) {
3977                         $fnames = implode( ', ', $danglingWriters );
3978                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
3979                 }
3980
3981                 if ( $this->conn ) {
3982                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
3983                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
3984                         Wikimedia\suppressWarnings();
3985                         $this->closeConnection();
3986                         Wikimedia\restoreWarnings();
3987                         $this->conn = false;
3988                         $this->opened = false;
3989                 }
3990         }
3991 }
3992
3993 class_alias( Database::class, 'DatabaseBase' ); // b/c for old name
3994 class_alias( Database::class, 'Database' ); // b/c global alias