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