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 LogicException;
  37 use InvalidArgumentException;
  38 use UnexpectedValueException;
  39 use Exception;
  40 use RuntimeException;
  41
  42 /**
  43  * Relational database abstraction object
  44  *
  45  * @ingroup Database
  46  * @since 1.28
  47  */
  48 abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAwareInterface {
  49         /** Number of times to re-try an operation in case of deadlock */
  50         const DEADLOCK_TRIES = 4;
  51         /** Minimum time to wait before retry, in microseconds */
  52         const DEADLOCK_DELAY_MIN = 500000;
  53         /** Maximum time to wait before retry */
  54         const DEADLOCK_DELAY_MAX = 1500000;
  55
  56         /** How long before it is worth doing a dummy query to test the connection */
  57         const PING_TTL = 1.0;
  58         const PING_QUERY = 'SELECT 1 AS ping';
  59
  60         const TINY_WRITE_SEC = 0.010;
  61         const SLOW_WRITE_SEC = 0.500;
  62         const SMALL_WRITE_ROWS = 100;
  63
  64         /** @var string Whether lock granularity is on the level of the entire database */
  65         const ATTR_DB_LEVEL_LOCKING = 'db-level-locking';
  66
  67         /** @var int New Database instance will not be connected yet when returned */
  68         const NEW_UNCONNECTED = 0;
  69         /** @var int New Database instance will already be connected when returned */
  70         const NEW_CONNECTED = 1;
  71
  72         /** @var string SQL query */
  73         protected $lastQuery = '';
  74         /** @var float|bool UNIX timestamp of last write query */
  75         protected $lastWriteTime = false;
  76         /** @var string|bool */
  77         protected $phpError = false;
  78         /** @var string Server that this instance is currently connected to */
  79         protected $server;
  80         /** @var string User that this instance is currently connected under the name of */
  81         protected $user;
  82         /** @var string Password used to establish the current connection */
  83         protected $password;
  84         /** @var array[] Map of (table => (dbname, schema, prefix) map) */
  85         protected $tableAliases = [];
  86         /** @var string[] Map of (index alias => index) */
  87         protected $indexAliases = [];
  88         /** @var bool Whether this PHP instance is for a CLI script */
  89         protected $cliMode;
  90         /** @var string Agent name for query profiling */
  91         protected $agent;
  92         /** @var array Parameters used by initConnection() to establish a connection */
  93         protected $connectionParams = [];
  94         /** @var BagOStuff APC cache */
  95         protected $srvCache;
  96         /** @var LoggerInterface */
  97         protected $connLogger;
  98         /** @var LoggerInterface */
  99         protected $queryLogger;
 100         /** @var callback Error logging callback */
 101         protected $errorLogger;
 102         /** @var callback Deprecation logging callback */
 103         protected $deprecationLogger;
 104
 105         /** @var resource|null Database connection */
 106         protected $conn = null;
 107         /** @var bool */
 108         protected $opened = false;
 109
 110         /** @var array[] List of (callable, method name, atomic section id) */
 111         protected $trxIdleCallbacks = [];
 112         /** @var array[] List of (callable, method name, atomic section id) */
 113         protected $trxPreCommitCallbacks = [];
 114         /** @var array[] List of (callable, method name, atomic section id) */
 115         protected $trxEndCallbacks = [];
 116         /** @var callable[] Map of (name => callable) */
 117         protected $trxRecurringCallbacks = [];
 118         /** @var bool Whether to suppress triggering of transaction end callbacks */
 119         protected $trxEndCallbacksSuppressed = false;
 120
 121         /** @var int */
 122         protected $flags;
 123         /** @var array */
 124         protected $lbInfo = [];
 125         /** @var array|bool */
 126         protected $schemaVars = false;
 127         /** @var array */
 128         protected $sessionVars = [];
 129         /** @var array|null */
 130         protected $preparedArgs;
 131         /** @var string|bool|null Stashed value of html_errors INI setting */
 132         protected $htmlErrors;
 133         /** @var string */
 134         protected $delimiter = ';';
 135         /** @var DatabaseDomain */
 136         protected $currentDomain;
 137         /** @var integer|null Rows affected by the last query to query() or its CRUD wrappers */
 138         protected $affectedRowCount;
 139
 140         /**
 141          * @var int Transaction status
 142          */
 143         protected $trxStatus = self::STATUS_TRX_NONE;
 144         /**
 145          * @var Exception|null The last error that caused the status to become STATUS_TRX_ERROR
 146          */
 147         protected $trxStatusCause;
 148         /**
 149          * @var array|null If wasKnownStatementRollbackError() prevented trxStatus from being set,
 150          *  the relevant details are stored here.
 151          */
 152         protected $trxStatusIgnoredCause;
 153         /**
 154          * Either 1 if a transaction is active or 0 otherwise.
 155          * The other Trx fields may not be meaningfull if this is 0.
 156          *
 157          * @var int
 158          */
 159         protected $trxLevel = 0;
 160         /**
 161          * Either a short hexidecimal string if a transaction is active or ""
 162          *
 163          * @var string
 164          * @see Database::trxLevel
 165          */
 166         protected $trxShortId = '';
 167         /**
 168          * The UNIX time that the transaction started. Callers can assume that if
 169          * snapshot isolation is used, then the data is *at least* up to date to that
 170          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 171          *
 172          * @var float|null
 173          * @see Database::trxLevel
 174          */
 175         private $trxTimestamp = null;
 176         /** @var float Lag estimate at the time of BEGIN */
 177         private $trxReplicaLag = null;
 178         /**
 179          * Remembers the function name given for starting the most recent transaction via begin().
 180          * Used to provide additional context for error reporting.
 181          *
 182          * @var string
 183          * @see Database::trxLevel
 184          */
 185         private $trxFname = null;
 186         /**
 187          * Record if possible write queries were done in the last transaction started
 188          *
 189          * @var bool
 190          * @see Database::trxLevel
 191          */
 192         private $trxDoneWrites = false;
 193         /**
 194          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 195          *
 196          * @var bool
 197          * @see Database::trxLevel
 198          */
 199         private $trxAutomatic = false;
 200         /**
 201          * Counter for atomic savepoint identifiers. Reset when a new transaction begins.
 202          *
 203          * @var int
 204          */
 205         private $trxAtomicCounter = 0;
 206         /**
 207          * Array of levels of atomicity within transactions
 208          *
 209          * @var array List of (name, unique ID, savepoint ID)
 210          */
 211         private $trxAtomicLevels = [];
 212         /**
 213          * Record if the current transaction was started implicitly by Database::startAtomic
 214          *
 215          * @var bool
 216          */
 217         private $trxAutomaticAtomic = false;
 218         /**
 219          * Track the write query callers of the current transaction
 220          *
 221          * @var string[]
 222          */
 223         private $trxWriteCallers = [];
 224         /**
 225          * @var float Seconds spent in write queries for the current transaction
 226          */
 227         private $trxWriteDuration = 0.0;
 228         /**
 229          * @var int Number of write queries for the current transaction
 230          */
 231         private $trxWriteQueryCount = 0;
 232         /**
 233          * @var int Number of rows affected by write queries for the current transaction
 234          */
 235         private $trxWriteAffectedRows = 0;
 236         /**
 237          * @var float Like trxWriteQueryCount but excludes lock-bound, easy to replicate, queries
 238          */
 239         private $trxWriteAdjDuration = 0.0;
 240         /**
 241          * @var int Number of write queries counted in trxWriteAdjDuration
 242          */
 243         private $trxWriteAdjQueryCount = 0;
 244         /**
 245          * @var float RTT time estimate
 246          */
 247         private $rttEstimate = 0.0;
 248
 249         /** @var array Map of (name => 1) for locks obtained via lock() */
 250         private $namedLocksHeld = [];
 251         /** @var array Map of (table name => 1) for TEMPORARY tables */
 252         protected $sessionTempTables = [];
 253
 254         /** @var IDatabase|null Lazy handle to the master DB this server replicates from */
 255         private $lazyMasterHandle;
 256
 257         /** @var float UNIX timestamp */
 258         protected $lastPing = 0.0;
 259
 260         /** @var int[] Prior flags member variable values */
 261         private $priorFlags = [];
 262
 263         /** @var mixed Class name or object With profileIn/profileOut methods */
 264         protected $profiler;
 265         /** @var TransactionProfiler */
 266         protected $trxProfiler;
 267
 268         /** @var int */
 269         protected $nonNativeInsertSelectBatchSize = 10000;
 270
 271         /** @var string Idiom used when a cancelable atomic section started the transaction */
 272         private static $NOT_APPLICABLE = 'n/a';
 273         /** @var string Prefix to the atomic section counter used to make savepoint IDs */
 274         private static $SAVEPOINT_PREFIX = 'wikimedia_rdbms_atomic';
 275
 276         /** @var int Transaction is in a error state requiring a full or savepoint rollback */
 277         const STATUS_TRX_ERROR = 1;
 278         /** @var int Transaction is active and in a normal state */
 279         const STATUS_TRX_OK = 2;
 280         /** @var int No transaction is active */
 281         const STATUS_TRX_NONE = 3;
 282
 283         /**
 284          * @note exceptions for missing libraries/drivers should be thrown in initConnection()
 285          * @param array $params Parameters passed from Database::factory()
 286          */
 287         protected function __construct( array $params ) {
 288                 foreach ( [ 'host', 'user', 'password', 'dbname', 'schema', 'tablePrefix' ] as $name ) {
 289                         $this->connectionParams[$name] = $params[$name];
 290                 }
 291
 292                 $this->cliMode = $params['cliMode'];
 293                 // Agent name is added to SQL queries in a comment, so make sure it can't break out
 294                 $this->agent = str_replace( '/', '-', $params['agent'] );
 295
 296                 $this->flags = $params['flags'];
 297                 if ( $this->flags & self::DBO_DEFAULT ) {
 298                         if ( $this->cliMode ) {
 299                                 $this->flags &= ~self::DBO_TRX;
 300                         } else {
 301                                 $this->flags |= self::DBO_TRX;
 302                         }
 303                 }
 304                 // Disregard deprecated DBO_IGNORE flag (T189999)
 305                 $this->flags &= ~self::DBO_IGNORE;
 306
 307                 $this->sessionVars = $params['variables'];
 308
 309                 $this->srvCache = $params['srvCache'] ?? new HashBagOStuff();
 310
 311                 $this->profiler = $params['profiler'];
 312                 $this->trxProfiler = $params['trxProfiler'];
 313                 $this->connLogger = $params['connLogger'];
 314                 $this->queryLogger = $params['queryLogger'];
 315                 $this->errorLogger = $params['errorLogger'];
 316                 $this->deprecationLogger = $params['deprecationLogger'];
 317
 318                 if ( isset( $params['nonNativeInsertSelectBatchSize'] ) ) {
 319                         $this->nonNativeInsertSelectBatchSize = $params['nonNativeInsertSelectBatchSize'];
 320                 }
 321
 322                 // Set initial dummy domain until open() sets the final DB/prefix
 323                 $this->currentDomain = new DatabaseDomain(
 324                         $params['dbname'] != '' ? $params['dbname'] : null,
 325                         $params['schema'] != '' ? $params['schema'] : null,
 326                         $params['tablePrefix']
 327                 );
 328         }
 329
 330         /**
 331          * Initialize the connection to the database over the wire (or to local files)
 332          *
 333          * @throws LogicException
 334          * @throws InvalidArgumentException
 335          * @throws DBConnectionError
 336          * @since 1.31
 337          */
 338         final public function initConnection() {
 339                 if ( $this->isOpen() ) {
 340                         throw new LogicException( __METHOD__ . ': already connected.' );
 341                 }
 342                 // Establish the connection
 343                 $this->doInitConnection();
 344         }
 345
 346         /**
 347          * Actually connect to the database over the wire (or to local files)
 348          *
 349          * @throws InvalidArgumentException
 350          * @throws DBConnectionError
 351          * @since 1.31
 352          */
 353         protected function doInitConnection() {
 354                 if ( strlen( $this->connectionParams['user'] ) ) {
 355                         $this->open(
 356                                 $this->connectionParams['host'],
 357                                 $this->connectionParams['user'],
 358                                 $this->connectionParams['password'],
 359                                 $this->connectionParams['dbname'],
 360                                 $this->connectionParams['schema'],
 361                                 $this->connectionParams['tablePrefix']
 362                         );
 363                 } else {
 364                         throw new InvalidArgumentException( "No database user provided." );
 365                 }
 366         }
 367
 368         /**
 369          * Open a new connection to the database (closing any existing one)
 370          *
 371          * @param string $server Database server host
 372          * @param string $user Database user name
 373          * @param string $password Database user password
 374          * @param string $dbName Database name
 375          * @param string|null $schema Database schema name
 376          * @param string $tablePrefix Table prefix
 377          * @return bool
 378          * @throws DBConnectionError
 379          */
 380         abstract protected function open( $server, $user, $password, $dbName, $schema, $tablePrefix );
 381
 382         /**
 383          * Construct a Database subclass instance given a database type and parameters
 384          *
 385          * This also connects to the database immediately upon object construction
 386          *
 387          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 388          * @param array $p Parameter map with keys:
 389          *   - host : The hostname of the DB server
 390          *   - user : The name of the database user the client operates under
 391          *   - password : The password for the database user
 392          *   - dbname : The name of the database to use where queries do not specify one.
 393          *      The database must exist or an error might be thrown. Setting this to the empty string
 394          *      will avoid any such errors and make the handle have no implicit database scope. This is
 395          *      useful for queries like SHOW STATUS, CREATE DATABASE, or DROP DATABASE. Note that a
 396          *      "database" in Postgres is rougly equivalent to an entire MySQL server. This the domain
 397          *      in which user names and such are defined, e.g. users are database-specific in Postgres.
 398          *   - schema : The database schema to use (if supported). A "schema" in Postgres is roughly
 399          *      equivalent to a "database" in MySQL. Note that MySQL and SQLite do not use schemas.
 400          *   - tablePrefix : Optional table prefix that is implicitly added on to all table names
 401          *      recognized in queries. This can be used in place of schemas for handle site farms.
 402          *   - flags : Optional bitfield of DBO_* constants that define connection, protocol,
 403          *      buffering, and transaction behavior. It is STRONGLY adviced to leave the DBO_DEFAULT
 404          *      flag in place UNLESS this this database simply acts as a key/value store.
 405          *   - driver: Optional name of a specific DB client driver. For MySQL, there is only the
 406          *      'mysqli' driver; the old one 'mysql' has been removed.
 407          *   - variables: Optional map of session variables to set after connecting. This can be
 408          *      used to adjust lock timeouts or encoding modes and the like.
 409          *   - connLogger: Optional PSR-3 logger interface instance.
 410          *   - queryLogger: Optional PSR-3 logger interface instance.
 411          *   - profiler: Optional class name or object with profileIn()/profileOut() methods.
 412          *      These will be called in query(), using a simplified version of the SQL that also
 413          *      includes the agent as a SQL comment.
 414          *   - trxProfiler: Optional TransactionProfiler instance.
 415          *   - errorLogger: Optional callback that takes an Exception and logs it.
 416          *   - deprecationLogger: Optional callback that takes a string and logs it.
 417          *   - cliMode: Whether to consider the execution context that of a CLI script.
 418          *   - agent: Optional name used to identify the end-user in query profiling/logging.
 419          *   - srvCache: Optional BagOStuff instance to an APC-style cache.
 420          *   - nonNativeInsertSelectBatchSize: Optional batch size for non-native INSERT SELECT emulation.
 421          * @param int $connect One of the class constants (NEW_CONNECTED, NEW_UNCONNECTED) [optional]
 422          * @return Database|null If the database driver or extension cannot be found
 423          * @throws InvalidArgumentException If the database driver or extension cannot be found
 424          * @since 1.18
 425          */
 426         final public static function factory( $dbType, $p = [], $connect = self::NEW_CONNECTED ) {
 427                 $class = self::getClass( $dbType, $p['driver'] ?? null );
 428
 429                 if ( class_exists( $class ) && is_subclass_of( $class, IDatabase::class ) ) {
 430                         // Resolve some defaults for b/c
 431                         $p['host'] = $p['host'] ?? false;
 432                         $p['user'] = $p['user'] ?? false;
 433                         $p['password'] = $p['password'] ?? false;
 434                         $p['dbname'] = $p['dbname'] ?? false;
 435                         $p['flags'] = $p['flags'] ?? 0;
 436                         $p['variables'] = $p['variables'] ?? [];
 437                         $p['tablePrefix'] = $p['tablePrefix'] ?? '';
 438                         $p['schema'] = $p['schema'] ?? null;
 439                         $p['cliMode'] = $p['cliMode'] ?? ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 440                         $p['agent'] = $p['agent'] ?? '';
 441                         if ( !isset( $p['connLogger'] ) ) {
 442                                 $p['connLogger'] = new NullLogger();
 443                         }
 444                         if ( !isset( $p['queryLogger'] ) ) {
 445                                 $p['queryLogger'] = new NullLogger();
 446                         }
 447                         $p['profiler'] = $p['profiler'] ?? null;
 448                         if ( !isset( $p['trxProfiler'] ) ) {
 449                                 $p['trxProfiler'] = new TransactionProfiler();
 450                         }
 451                         if ( !isset( $p['errorLogger'] ) ) {
 452                                 $p['errorLogger'] = function ( Exception $e ) {
 453                                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 454                                 };
 455                         }
 456                         if ( !isset( $p['deprecationLogger'] ) ) {
 457                                 $p['deprecationLogger'] = function ( $msg ) {
 458                                         trigger_error( $msg, E_USER_DEPRECATED );
 459                                 };
 460                         }
 461
 462                         /** @var Database $conn */
 463                         $conn = new $class( $p );
 464                         if ( $connect == self::NEW_CONNECTED ) {
 465                                 $conn->initConnection();
 466                         }
 467                 } else {
 468                         $conn = null;
 469                 }
 470
 471                 return $conn;
 472         }
 473
 474         /**
 475          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 476          * @param string|null $driver Optional name of a specific DB client driver
 477          * @return array Map of (Database::ATTRIBUTE_* constant => value) for all such constants
 478          * @throws InvalidArgumentException
 479          * @since 1.31
 480          */
 481         final public static function attributesFromType( $dbType, $driver = null ) {
 482                 static $defaults = [ self::ATTR_DB_LEVEL_LOCKING => false ];
 483
 484                 $class = self::getClass( $dbType, $driver );
 485
 486                 return call_user_func( [ $class, 'getAttributes' ] ) + $defaults;
 487         }
 488
 489         /**
 490          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 491          * @param string|null $driver Optional name of a specific DB client driver
 492          * @return string Database subclass name to use
 493          * @throws InvalidArgumentException
 494          */
 495         private static function getClass( $dbType, $driver = null ) {
 496                 // For database types with built-in support, the below maps type to IDatabase
 497                 // implementations. For types with multipe driver implementations (PHP extensions),
 498                 // an array can be used, keyed by extension name. In case of an array, the
 499                 // optional 'driver' parameter can be used to force a specific driver. Otherwise,
 500                 // we auto-detect the first available driver. For types without built-in support,
 501                 // an class named "Database<Type>" us used, eg. DatabaseFoo for type 'foo'.
 502                 static $builtinTypes = [
 503                         'mssql' => DatabaseMssql::class,
 504                         'mysql' => [ 'mysqli' => DatabaseMysqli::class ],
 505                         'sqlite' => DatabaseSqlite::class,
 506                         'postgres' => DatabasePostgres::class,
 507                 ];
 508
 509                 $dbType = strtolower( $dbType );
 510                 $class = false;
 511
 512                 if ( isset( $builtinTypes[$dbType] ) ) {
 513                         $possibleDrivers = $builtinTypes[$dbType];
 514                         if ( is_string( $possibleDrivers ) ) {
 515                                 $class = $possibleDrivers;
 516                         } else {
 517                                 if ( (string)$driver !== '' ) {
 518                                         if ( !isset( $possibleDrivers[$driver] ) ) {
 519                                                 throw new InvalidArgumentException( __METHOD__ .
 520                                                         " type '$dbType' does not support driver '{$driver}'" );
 521                                         } else {
 522                                                 $class = $possibleDrivers[$driver];
 523                                         }
 524                                 } else {
 525                                         foreach ( $possibleDrivers as $posDriver => $possibleClass ) {
 526                                                 if ( extension_loaded( $posDriver ) ) {
 527                                                         $class = $possibleClass;
 528                                                         break;
 529                                                 }
 530                                         }
 531                                 }
 532                         }
 533                 } else {
 534                         $class = 'Database' . ucfirst( $dbType );
 535                 }
 536
 537                 if ( $class === false ) {
 538                         throw new InvalidArgumentException( __METHOD__ .
 539                                 " no viable database extension found for type '$dbType'" );
 540                 }
 541
 542                 return $class;
 543         }
 544
 545         /**
 546          * @return array Map of (Database::ATTRIBUTE_* constant => value
 547          * @since 1.31
 548          */
 549         protected static function getAttributes() {
 550                 return [];
 551         }
 552
 553         /**
 554          * Set the PSR-3 logger interface to use for query logging. (The logger
 555          * interfaces for connection logging and error logging can be set with the
 556          * constructor.)
 557          *
 558          * @param LoggerInterface $logger
 559          */
 560         public function setLogger( LoggerInterface $logger ) {
 561                 $this->queryLogger = $logger;
 562         }
 563
 564         public function getServerInfo() {
 565                 return $this->getServerVersion();
 566         }
 567
 568         public function bufferResults( $buffer = null ) {
 569                 $res = !$this->getFlag( self::DBO_NOBUFFER );
 570                 if ( $buffer !== null ) {
 571                         $buffer
 572                                 ? $this->clearFlag( self::DBO_NOBUFFER )
 573                                 : $this->setFlag( self::DBO_NOBUFFER );
 574                 }
 575
 576                 return $res;
 577         }
 578
 579         public function trxLevel() {
 580                 return $this->trxLevel;
 581         }
 582
 583         public function trxTimestamp() {
 584                 return $this->trxLevel ? $this->trxTimestamp : null;
 585         }
 586
 587         /**
 588          * @return int One of the STATUS_TRX_* class constants
 589          * @since 1.31
 590          */
 591         public function trxStatus() {
 592                 return $this->trxStatus;
 593         }
 594
 595         public function tablePrefix( $prefix = null ) {
 596                 $old = $this->currentDomain->getTablePrefix();
 597                 if ( $prefix !== null ) {
 598                         $this->currentDomain = new DatabaseDomain(
 599                                 $this->currentDomain->getDatabase(),
 600                                 $this->currentDomain->getSchema(),
 601                                 $prefix
 602                         );
 603                 }
 604
 605                 return $old;
 606         }
 607
 608         public function dbSchema( $schema = null ) {
 609                 $old = $this->currentDomain->getSchema();
 610                 if ( $schema !== null ) {
 611                         $this->currentDomain = new DatabaseDomain(
 612                                 $this->currentDomain->getDatabase(),
 613                                 // DatabaseDomain uses null for unspecified schemas
 614                                 strlen( $schema ) ? $schema : null,
 615                                 $this->currentDomain->getTablePrefix()
 616                         );
 617                 }
 618
 619                 return (string)$old;
 620         }
 621
 622         /**
 623          * @return string Schema to use to qualify relations in queries
 624          */
 625         protected function relationSchemaQualifier() {
 626                 return $this->dbSchema();
 627         }
 628
 629         public function getLBInfo( $name = null ) {
 630                 if ( is_null( $name ) ) {
 631                         return $this->lbInfo;
 632                 } else {
 633                         if ( array_key_exists( $name, $this->lbInfo ) ) {
 634                                 return $this->lbInfo[$name];
 635                         } else {
 636                                 return null;
 637                         }
 638                 }
 639         }
 640
 641         public function setLBInfo( $name, $value = null ) {
 642                 if ( is_null( $value ) ) {
 643                         $this->lbInfo = $name;
 644                 } else {
 645                         $this->lbInfo[$name] = $value;
 646                 }
 647         }
 648
 649         public function setLazyMasterHandle( IDatabase $conn ) {
 650                 $this->lazyMasterHandle = $conn;
 651         }
 652
 653         /**
 654          * @return IDatabase|null
 655          * @see setLazyMasterHandle()
 656          * @since 1.27
 657          */
 658         protected function getLazyMasterHandle() {
 659                 return $this->lazyMasterHandle;
 660         }
 661
 662         public function implicitGroupby() {
 663                 return true;
 664         }
 665
 666         public function implicitOrderby() {
 667                 return true;
 668         }
 669
 670         public function lastQuery() {
 671                 return $this->lastQuery;
 672         }
 673
 674         public function doneWrites() {
 675                 return (bool)$this->lastWriteTime;
 676         }
 677
 678         public function lastDoneWrites() {
 679                 return $this->lastWriteTime ?: false;
 680         }
 681
 682         public function writesPending() {
 683                 return $this->trxLevel && $this->trxDoneWrites;
 684         }
 685
 686         public function writesOrCallbacksPending() {
 687                 return $this->trxLevel && (
 688                         $this->trxDoneWrites ||
 689                         $this->trxIdleCallbacks ||
 690                         $this->trxPreCommitCallbacks ||
 691                         $this->trxEndCallbacks
 692                 );
 693         }
 694
 695         public function preCommitCallbacksPending() {
 696                 return $this->trxLevel && $this->trxPreCommitCallbacks;
 697         }
 698
 699         /**
 700          * @return string|null
 701          */
 702         final protected function getTransactionRoundId() {
 703                 // If transaction round participation is enabled, see if one is active
 704                 if ( $this->getFlag( self::DBO_TRX ) ) {
 705                         $id = $this->getLBInfo( 'trxRoundId' );
 706
 707                         return is_string( $id ) ? $id : null;
 708                 }
 709
 710                 return null;
 711         }
 712
 713         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 714                 if ( !$this->trxLevel ) {
 715                         return false;
 716                 } elseif ( !$this->trxDoneWrites ) {
 717                         return 0.0;
 718                 }
 719
 720                 switch ( $type ) {
 721                         case self::ESTIMATE_DB_APPLY:
 722                                 return $this->pingAndCalculateLastTrxApplyTime();
 723                         default: // everything
 724                                 return $this->trxWriteDuration;
 725                 }
 726         }
 727
 728         /**
 729          * @return float Time to apply writes to replicas based on trxWrite* fields
 730          */
 731         private function pingAndCalculateLastTrxApplyTime() {
 732                 $this->ping( $rtt );
 733
 734                 $rttAdjTotal = $this->trxWriteAdjQueryCount * $rtt;
 735                 $applyTime = max( $this->trxWriteAdjDuration - $rttAdjTotal, 0 );
 736                 // For omitted queries, make them count as something at least
 737                 $omitted = $this->trxWriteQueryCount - $this->trxWriteAdjQueryCount;
 738                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 739
 740                 return $applyTime;
 741         }
 742
 743         public function pendingWriteCallers() {
 744                 return $this->trxLevel ? $this->trxWriteCallers : [];
 745         }
 746
 747         public function pendingWriteRowsAffected() {
 748                 return $this->trxWriteAffectedRows;
 749         }
 750
 751         /**
 752          * List the methods that have write queries or callbacks for the current transaction
 753          *
 754          * This method should not be used outside of Database/LoadBalancer
 755          *
 756          * @return string[]
 757          * @since 1.32
 758          */
 759         public function pendingWriteAndCallbackCallers() {
 760                 $fnames = $this->pendingWriteCallers();
 761                 foreach ( [
 762                         $this->trxIdleCallbacks,
 763                         $this->trxPreCommitCallbacks,
 764                         $this->trxEndCallbacks
 765                 ] as $callbacks ) {
 766                         foreach ( $callbacks as $callback ) {
 767                                 $fnames[] = $callback[1];
 768                         }
 769                 }
 770
 771                 return $fnames;
 772         }
 773
 774         /**
 775          * @return string
 776          */
 777         private function flatAtomicSectionList() {
 778                 return array_reduce( $this->trxAtomicLevels, function ( $accum, $v ) {
 779                         return $accum === null ? $v[0] : "$accum, " . $v[0];
 780                 } );
 781         }
 782
 783         public function isOpen() {
 784                 return $this->opened;
 785         }
 786
 787         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 788                 if ( ( $flag & self::DBO_IGNORE ) ) {
 789                         throw new UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 790                 }
 791
 792                 if ( $remember === self::REMEMBER_PRIOR ) {
 793                         array_push( $this->priorFlags, $this->flags );
 794                 }
 795                 $this->flags |= $flag;
 796         }
 797
 798         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 799                 if ( ( $flag & self::DBO_IGNORE ) ) {
 800                         throw new UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 801                 }
 802
 803                 if ( $remember === self::REMEMBER_PRIOR ) {
 804                         array_push( $this->priorFlags, $this->flags );
 805                 }
 806                 $this->flags &= ~$flag;
 807         }
 808
 809         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 810                 if ( !$this->priorFlags ) {
 811                         return;
 812                 }
 813
 814                 if ( $state === self::RESTORE_INITIAL ) {
 815                         $this->flags = reset( $this->priorFlags );
 816                         $this->priorFlags = [];
 817                 } else {
 818                         $this->flags = array_pop( $this->priorFlags );
 819                 }
 820         }
 821
 822         public function getFlag( $flag ) {
 823                 return !!( $this->flags & $flag );
 824         }
 825
 826         /**
 827          * @param string $name Class field name
 828          * @return mixed
 829          * @deprecated Since 1.28
 830          */
 831         public function getProperty( $name ) {
 832                 return $this->$name;
 833         }
 834
 835         public function getDomainID() {
 836                 return $this->currentDomain->getId();
 837         }
 838
 839         final public function getWikiID() {
 840                 return $this->getDomainID();
 841         }
 842
 843         /**
 844          * Get information about an index into an object
 845          * @param string $table Table name
 846          * @param string $index Index name
 847          * @param string $fname Calling function name
 848          * @return mixed Database-specific index description class or false if the index does not exist
 849          */
 850         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 851
 852         /**
 853          * Wrapper for addslashes()
 854          *
 855          * @param string $s String to be slashed.
 856          * @return string Slashed string.
 857          */
 858         abstract function strencode( $s );
 859
 860         /**
 861          * Set a custom error handler for logging errors during database connection
 862          */
 863         protected function installErrorHandler() {
 864                 $this->phpError = false;
 865                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 866                 set_error_handler( [ $this, 'connectionErrorLogger' ] );
 867         }
 868
 869         /**
 870          * Restore the previous error handler and return the last PHP error for this DB
 871          *
 872          * @return bool|string
 873          */
 874         protected function restoreErrorHandler() {
 875                 restore_error_handler();
 876                 if ( $this->htmlErrors !== false ) {
 877                         ini_set( 'html_errors', $this->htmlErrors );
 878                 }
 879
 880                 return $this->getLastPHPError();
 881         }
 882
 883         /**
 884          * @return string|bool Last PHP error for this DB (typically connection errors)
 885          */
 886         protected function getLastPHPError() {
 887                 if ( $this->phpError ) {
 888                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->phpError );
 889                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 890
 891                         return $error;
 892                 }
 893
 894                 return false;
 895         }
 896
 897         /**
 898          * Error handler for logging errors during database connection
 899          * This method should not be used outside of Database classes
 900          *
 901          * @param int $errno
 902          * @param string $errstr
 903          */
 904         public function connectionErrorLogger( $errno, $errstr ) {
 905                 $this->phpError = $errstr;
 906         }
 907
 908         /**
 909          * Create a log context to pass to PSR-3 logger functions.
 910          *
 911          * @param array $extras Additional data to add to context
 912          * @return array
 913          */
 914         protected function getLogContext( array $extras = [] ) {
 915                 return array_merge(
 916                         [
 917                                 'db_server' => $this->server,
 918                                 'db_name' => $this->getDBname(),
 919                                 'db_user' => $this->user,
 920                         ],
 921                         $extras
 922                 );
 923         }
 924
 925         final public function close() {
 926                 $exception = null; // error to throw after disconnecting
 927
 928                 if ( $this->conn ) {
 929                         // Roll back any dangling transaction first
 930                         if ( $this->trxLevel ) {
 931                                 if ( $this->trxAtomicLevels ) {
 932                                         // Cannot let incomplete atomic sections be committed
 933                                         $levels = $this->flatAtomicSectionList();
 934                                         $exception = new DBUnexpectedError(
 935                                                 $this,
 936                                                 __METHOD__ . ": atomic sections $levels are still open."
 937                                         );
 938                                 } elseif ( $this->trxAutomatic ) {
 939                                         // Only the connection manager can commit non-empty DBO_TRX transactions
 940                                         // (empty ones we can silently roll back)
 941                                         if ( $this->writesOrCallbacksPending() ) {
 942                                                 $exception = new DBUnexpectedError(
 943                                                         $this,
 944                                                         __METHOD__ .
 945                                                         ": mass commit/rollback of peer transaction required (DBO_TRX set)."
 946                                                 );
 947                                         }
 948                                 } else {
 949                                         // Manual transactions should have been committed or rolled
 950                                         // back, even if empty.
 951                                         $exception = new DBUnexpectedError(
 952                                                 $this,
 953                                                 __METHOD__ . ": transaction is still open (from {$this->trxFname})."
 954                                         );
 955                                 }
 956
 957                                 if ( $this->trxEndCallbacksSuppressed ) {
 958                                         $exception = $exception ?: new DBUnexpectedError(
 959                                                 $this,
 960                                                 __METHOD__ . ': callbacks are suppressed; cannot properly commit.'
 961                                         );
 962                                 }
 963
 964                                 // Rollback the changes and run any callbacks as needed
 965                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
 966                         }
 967
 968                         // Close the actual connection in the binding handle
 969                         $closed = $this->closeConnection();
 970                         $this->conn = false;
 971                 } else {
 972                         $closed = true; // already closed; nothing to do
 973                 }
 974
 975                 $this->opened = false;
 976
 977                 // Throw any unexpected errors after having disconnected
 978                 if ( $exception instanceof Exception ) {
 979                         throw $exception;
 980                 }
 981
 982                 // Sanity check that no callbacks are dangling
 983                 $fnames = $this->pendingWriteAndCallbackCallers();
 984                 if ( $fnames ) {
 985                         throw new RuntimeException(
 986                                 "Transaction callbacks are still pending:\n" . implode( ', ', $fnames )
 987                         );
 988                 }
 989
 990                 return $closed;
 991         }
 992
 993         /**
 994          * Make sure isOpen() returns true as a sanity check
 995          *
 996          * @throws DBUnexpectedError
 997          */
 998         protected function assertOpen() {
 999                 if ( !$this->isOpen() ) {
1000                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
1001                 }
1002         }
1003
1004         /**
1005          * Closes underlying database connection
1006          * @since 1.20
1007          * @return bool Whether connection was closed successfully
1008          */
1009         abstract protected function closeConnection();
1010
1011         /**
1012          * @deprecated since 1.32
1013          * @param string $error Fallback message, if none is given by DB
1014          * @throws DBConnectionError
1015          */
1016         public function reportConnectionError( $error = 'Unknown error' ) {
1017                 call_user_func( $this->deprecationLogger, 'Use of ' . __METHOD__ . ' is deprecated.' );
1018                 throw new DBConnectionError( $this, $this->lastError() ?: $error );
1019         }
1020
1021         /**
1022          * Run a query and return a DBMS-dependent wrapper (that has all IResultWrapper methods)
1023          *
1024          * This might return things, such as mysqli_result, that do not formally implement
1025          * IResultWrapper, but nonetheless implement all of its methods correctly
1026          *
1027          * @param string $sql SQL query.
1028          * @return IResultWrapper|bool Iterator to feed to fetchObject/fetchRow; false on failure
1029          */
1030         abstract protected function doQuery( $sql );
1031
1032         /**
1033          * Determine whether a query writes to the DB. When in doubt, this returns true.
1034          *
1035          * Main use cases:
1036          *
1037          * - Subsequent web requests should not need to wait for replication from
1038          *   the master position seen by this web request, unless this request made
1039          *   changes to the master. This is handled by ChronologyProtector by checking
1040          *   doneWrites() at the end of the request. doneWrites() returns true if any
1041          *   query set lastWriteTime; which query() does based on isWriteQuery().
1042          *
1043          * - Reject write queries to replica DBs, in query().
1044          *
1045          * @param string $sql
1046          * @return bool
1047          */
1048         protected function isWriteQuery( $sql ) {
1049                 // BEGIN and COMMIT queries are considered read queries here.
1050                 // Database backends and drivers (MySQL, MariaDB, php-mysqli) generally
1051                 // treat these as write queries, in that their results have "affected rows"
1052                 // as meta data as from writes, instead of "num rows" as from reads.
1053                 // But, we treat them as read queries because when reading data (from
1054                 // either replica or master) we use transactions to enable repeatable-read
1055                 // snapshots, which ensures we get consistent results from the same snapshot
1056                 // for all queries within a request. Use cases:
1057                 // - Treating these as writes would trigger ChronologyProtector (see method doc).
1058                 // - We use this method to reject writes to replicas, but we need to allow
1059                 //   use of transactions on replicas for read snapshots. This fine given
1060                 //   that transactions by themselves don't make changes, only actual writes
1061                 //   within the transaction matter, which we still detect.
1062                 return !preg_match(
1063                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SAVEPOINT|RELEASE|SET|SHOW|EXPLAIN|\(SELECT)\b/i',
1064                         $sql
1065                 );
1066         }
1067
1068         /**
1069          * @param string $sql
1070          * @return string|null
1071          */
1072         protected function getQueryVerb( $sql ) {
1073                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
1074         }
1075
1076         /**
1077          * Determine whether a SQL statement is sensitive to isolation level.
1078          *
1079          * A SQL statement is considered transactable if its result could vary
1080          * depending on the transaction isolation level. Operational commands
1081          * such as 'SET' and 'SHOW' are not considered to be transactable.
1082          *
1083          * Main purpose: Used by query() to decide whether to begin a transaction
1084          * before the current query (in DBO_TRX mode, on by default).
1085          *
1086          * @param string $sql
1087          * @return bool
1088          */
1089         protected function isTransactableQuery( $sql ) {
1090                 return !in_array(
1091                         $this->getQueryVerb( $sql ),
1092                         [ 'BEGIN', 'ROLLBACK', 'COMMIT', 'SET', 'SHOW', 'CREATE', 'ALTER' ],
1093                         true
1094                 );
1095         }
1096
1097         /**
1098          * @param string $sql A SQL query
1099          * @return bool Whether $sql is SQL for TEMPORARY table operation
1100          */
1101         protected function registerTempTableOperation( $sql ) {
1102                 if ( preg_match(
1103                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1104                         $sql,
1105                         $matches
1106                 ) ) {
1107                         $this->sessionTempTables[$matches[1]] = 1;
1108
1109                         return true;
1110                 } elseif ( preg_match(
1111                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1112                         $sql,
1113                         $matches
1114                 ) ) {
1115                         $isTemp = isset( $this->sessionTempTables[$matches[1]] );
1116                         unset( $this->sessionTempTables[$matches[1]] );
1117
1118                         return $isTemp;
1119                 } elseif ( preg_match(
1120                         '/^TRUNCATE\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1121                         $sql,
1122                         $matches
1123                 ) ) {
1124                         return isset( $this->sessionTempTables[$matches[1]] );
1125                 } elseif ( preg_match(
1126                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
1127                         $sql,
1128                         $matches
1129                 ) ) {
1130                         return isset( $this->sessionTempTables[$matches[1]] );
1131                 }
1132
1133                 return false;
1134         }
1135
1136         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
1137                 $this->assertTransactionStatus( $sql, $fname );
1138
1139                 # Avoid fatals if close() was called
1140                 $this->assertOpen();
1141
1142                 $priorWritesPending = $this->writesOrCallbacksPending();
1143                 $this->lastQuery = $sql;
1144
1145                 $isWrite = $this->isWriteQuery( $sql );
1146                 if ( $isWrite ) {
1147                         $isNonTempWrite = !$this->registerTempTableOperation( $sql );
1148                 } else {
1149                         $isNonTempWrite = false;
1150                 }
1151
1152                 if ( $isWrite ) {
1153                         if ( $this->getLBInfo( 'replica' ) === true ) {
1154                                 throw new DBError(
1155                                         $this,
1156                                         'Write operations are not allowed on replica database connections.'
1157                                 );
1158                         }
1159                         # In theory, non-persistent writes are allowed in read-only mode, but due to things
1160                         # like https://bugs.mysql.com/bug.php?id=33669 that might not work anyway...
1161                         $reason = $this->getReadOnlyReason();
1162                         if ( $reason !== false ) {
1163                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
1164                         }
1165                         # Set a flag indicating that writes have been done
1166                         $this->lastWriteTime = microtime( true );
1167                 }
1168
1169                 # Add trace comment to the begin of the sql string, right after the operator.
1170                 # Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598)
1171                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
1172
1173                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
1174                 if ( !$this->trxLevel && $this->getFlag( self::DBO_TRX )
1175                         && $this->isTransactableQuery( $sql )
1176                 ) {
1177                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
1178                         $this->trxAutomatic = true;
1179                 }
1180
1181                 # Keep track of whether the transaction has write queries pending
1182                 if ( $this->trxLevel && !$this->trxDoneWrites && $isWrite ) {
1183                         $this->trxDoneWrites = true;
1184                         $this->trxProfiler->transactionWritingIn(
1185                                 $this->server, $this->getDomainID(), $this->trxShortId );
1186                 }
1187
1188                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
1189                         $this->queryLogger->debug( "{$this->getDomainID()} {$commentedSql}" );
1190                 }
1191
1192                 # Send the query to the server and fetch any corresponding errors
1193                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1194                 $lastError = $this->lastError();
1195                 $lastErrno = $this->lastErrno();
1196
1197                 # Try reconnecting if the connection was lost
1198                 if ( $ret === false && $this->wasConnectionLoss() ) {
1199                         # Check if any meaningful session state was lost
1200                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
1201                         # Update session state tracking and try to restore the connection
1202                         $reconnected = $this->replaceLostConnection( __METHOD__ );
1203                         # Silently resend the query to the server if it is safe and possible
1204                         if ( $reconnected && $recoverable ) {
1205                                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1206                                 $lastError = $this->lastError();
1207                                 $lastErrno = $this->lastErrno();
1208
1209                                 if ( $ret === false && $this->wasConnectionLoss() ) {
1210                                         # Query probably causes disconnects; reconnect and do not re-run it
1211                                         $this->replaceLostConnection( __METHOD__ );
1212                                 }
1213                         }
1214                 }
1215
1216                 if ( $ret === false ) {
1217                         if ( $this->trxLevel ) {
1218                                 if ( $this->wasKnownStatementRollbackError() ) {
1219                                         # We're ignoring an error that caused just the current query to be aborted.
1220                                         # But log the cause so we can log a deprecation notice if a caller actually
1221                                         # does ignore it.
1222                                         $this->trxStatusIgnoredCause = [ $lastError, $lastErrno, $fname ];
1223                                 } else {
1224                                         # Either the query was aborted or all queries after BEGIN where aborted.
1225                                         # In the first case, the only options going forward are (a) ROLLBACK, or
1226                                         # (b) ROLLBACK TO SAVEPOINT (if one was set). If the later case, the only
1227                                         # option is ROLLBACK, since the snapshots would have been released.
1228                                         $this->trxStatus = self::STATUS_TRX_ERROR;
1229                                         $this->trxStatusCause =
1230                                                 $this->makeQueryException( $lastError, $lastErrno, $sql, $fname );
1231                                         $tempIgnore = false; // cannot recover
1232                                         $this->trxStatusIgnoredCause = null;
1233                                 }
1234                         }
1235
1236                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname, $tempIgnore );
1237                 }
1238
1239                 return $this->resultObject( $ret );
1240         }
1241
1242         /**
1243          * Wrapper for query() that also handles profiling, logging, and affected row count updates
1244          *
1245          * @param string $sql Original SQL query
1246          * @param string $commentedSql SQL query with debugging/trace comment
1247          * @param bool $isWrite Whether the query is a (non-temporary) write operation
1248          * @param string $fname Name of the calling function
1249          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
1250          *     object for a successful read query, or false on failure
1251          */
1252         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
1253                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1254                 # generalizeSQL() will probably cut down the query to reasonable
1255                 # logging size most of the time. The substr is really just a sanity check.
1256                 if ( $isMaster ) {
1257                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1258                 } else {
1259                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1260                 }
1261
1262                 # Include query transaction state
1263                 $queryProf .= $this->trxShortId ? " [TRX#{$this->trxShortId}]" : "";
1264
1265                 $startTime = microtime( true );
1266                 if ( $this->profiler ) {
1267                         $this->profiler->profileIn( $queryProf );
1268                 }
1269                 $this->affectedRowCount = null;
1270                 $ret = $this->doQuery( $commentedSql );
1271                 $this->affectedRowCount = $this->affectedRows();
1272                 if ( $this->profiler ) {
1273                         $this->profiler->profileOut( $queryProf );
1274                 }
1275                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1276
1277                 unset( $queryProfSection ); // profile out (if set)
1278
1279                 if ( $ret !== false ) {
1280                         $this->lastPing = $startTime;
1281                         if ( $isWrite && $this->trxLevel ) {
1282                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1283                                 $this->trxWriteCallers[] = $fname;
1284                         }
1285                 }
1286
1287                 if ( $sql === self::PING_QUERY ) {
1288                         $this->rttEstimate = $queryRuntime;
1289                 }
1290
1291                 $this->trxProfiler->recordQueryCompletion(
1292                         $queryProf,
1293                         $startTime,
1294                         $isWrite,
1295                         $isWrite ? $this->affectedRows() : $this->numRows( $ret )
1296                 );
1297                 $this->queryLogger->debug( $sql, [
1298                         'method' => $fname,
1299                         'master' => $isMaster,
1300                         'runtime' => $queryRuntime,
1301                 ] );
1302
1303                 return $ret;
1304         }
1305
1306         /**
1307          * Update the estimated run-time of a query, not counting large row lock times
1308          *
1309          * LoadBalancer can be set to rollback transactions that will create huge replication
1310          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1311          * queries, like inserting a row can take a long time due to row locking. This method
1312          * uses some simple heuristics to discount those cases.
1313          *
1314          * @param string $sql A SQL write query
1315          * @param float $runtime Total runtime, including RTT
1316          * @param int $affected Affected row count
1317          */
1318         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1319                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1320                 $indicativeOfReplicaRuntime = true;
1321                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1322                         $verb = $this->getQueryVerb( $sql );
1323                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1324                         if ( $verb === 'INSERT' ) {
1325                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1326                         } elseif ( $verb === 'REPLACE' ) {
1327                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1328                         }
1329                 }
1330
1331                 $this->trxWriteDuration += $runtime;
1332                 $this->trxWriteQueryCount += 1;
1333                 $this->trxWriteAffectedRows += $affected;
1334                 if ( $indicativeOfReplicaRuntime ) {
1335                         $this->trxWriteAdjDuration += $runtime;
1336                         $this->trxWriteAdjQueryCount += 1;
1337                 }
1338         }
1339
1340         /**
1341          * @param string $sql
1342          * @param string $fname
1343          * @throws DBTransactionStateError
1344          */
1345         private function assertTransactionStatus( $sql, $fname ) {
1346                 if ( $this->getQueryVerb( $sql ) === 'ROLLBACK' ) { // transaction/savepoint
1347                         return;
1348                 }
1349
1350                 if ( $this->trxStatus < self::STATUS_TRX_OK ) {
1351                         throw new DBTransactionStateError(
1352                                 $this,
1353                                 "Cannot execute query from $fname while transaction status is ERROR.",
1354                                 [],
1355                                 $this->trxStatusCause
1356                         );
1357                 } elseif ( $this->trxStatus === self::STATUS_TRX_OK && $this->trxStatusIgnoredCause ) {
1358                         list( $iLastError, $iLastErrno, $iFname ) = $this->trxStatusIgnoredCause;
1359                         call_user_func( $this->deprecationLogger,
1360                                 "Caller from $fname ignored an error originally raised from $iFname: " .
1361                                 "[$iLastErrno] $iLastError"
1362                         );
1363                         $this->trxStatusIgnoredCause = null;
1364                 }
1365         }
1366
1367         public function assertNoOpenTransactions() {
1368                 if ( $this->explicitTrxActive() ) {
1369                         throw new DBTransactionError(
1370                                 $this,
1371                                 "Explicit transaction still active. A caller may have caught an error. "
1372                                 . "Open transactions: " . $this->flatAtomicSectionList()
1373                         );
1374                 }
1375         }
1376
1377         /**
1378          * Determine whether or not it is safe to retry queries after a database
1379          * connection is lost
1380          *
1381          * @param string $sql SQL query
1382          * @param bool $priorWritesPending Whether there is a transaction open with
1383          *     possible write queries or transaction pre-commit/idle callbacks
1384          *     waiting on it to finish.
1385          * @return bool True if it is safe to retry the query, false otherwise
1386          */
1387         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1388                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1389                 # Dropped connections also mean that named locks are automatically released.
1390                 # Only allow error suppression in autocommit mode or when the lost transaction
1391                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1392                 if ( $this->namedLocksHeld ) {
1393                         return false; // possible critical section violation
1394                 } elseif ( $this->sessionTempTables ) {
1395                         return false; // tables might be queried latter
1396                 } elseif ( $sql === 'COMMIT' ) {
1397                         return !$priorWritesPending; // nothing written anyway? (T127428)
1398                 } elseif ( $sql === 'ROLLBACK' ) {
1399                         return true; // transaction lost...which is also what was requested :)
1400                 } elseif ( $this->explicitTrxActive() ) {
1401                         return false; // don't drop atomocity and explicit snapshots
1402                 } elseif ( $priorWritesPending ) {
1403                         return false; // prior writes lost from implicit transaction
1404                 }
1405
1406                 return true;
1407         }
1408
1409         /**
1410          * Clean things up after session (and thus transaction) loss
1411          */
1412         private function handleSessionLoss() {
1413                 // Clean up tracking of session-level things...
1414                 // https://dev.mysql.com/doc/refman/5.7/en/implicit-commit.html
1415                 // https://www.postgresql.org/docs/9.2/static/sql-createtable.html (ignoring ON COMMIT)
1416                 $this->sessionTempTables = [];
1417                 // https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
1418                 // https://www.postgresql.org/docs/9.4/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
1419                 $this->namedLocksHeld = [];
1420                 // Session loss implies transaction loss
1421                 $this->handleTransactionLoss();
1422         }
1423
1424         /**
1425          * Clean things up after transaction loss
1426          */
1427         private function handleTransactionLoss() {
1428                 $this->trxLevel = 0;
1429                 $this->trxAtomicCounter = 0;
1430                 $this->trxIdleCallbacks = []; // T67263; transaction already lost
1431                 $this->trxPreCommitCallbacks = []; // T67263; transaction already lost
1432                 try {
1433                         // Handle callbacks in trxEndCallbacks, e.g. onTransactionResolution().
1434                         // If callback suppression is set then the array will remain unhandled.
1435                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1436                 } catch ( Exception $ex ) {
1437                         // Already logged; move on...
1438                 }
1439                 try {
1440                         // Handle callbacks in trxRecurringCallbacks, e.g. setTransactionListener()
1441                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1442                 } catch ( Exception $ex ) {
1443                         // Already logged; move on...
1444                 }
1445         }
1446
1447         /**
1448          * Checks whether the cause of the error is detected to be a timeout.
1449          *
1450          * It returns false by default, and not all engines support detecting this yet.
1451          * If this returns false, it will be treated as a generic query error.
1452          *
1453          * @param string $error Error text
1454          * @param int $errno Error number
1455          * @return bool
1456          */
1457         protected function wasQueryTimeout( $error, $errno ) {
1458                 return false;
1459         }
1460
1461         /**
1462          * Report a query error. Log the error, and if neither the object ignore
1463          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1464          *
1465          * @param string $error
1466          * @param int $errno
1467          * @param string $sql
1468          * @param string $fname
1469          * @param bool $tempIgnore
1470          * @throws DBQueryError
1471          */
1472         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1473                 if ( $tempIgnore ) {
1474                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1475                 } else {
1476                         $exception = $this->makeQueryException( $error, $errno, $sql, $fname );
1477
1478                         throw $exception;
1479                 }
1480         }
1481
1482         /**
1483          * @param string $error
1484          * @param string|int $errno
1485          * @param string $sql
1486          * @param string $fname
1487          * @return DBError
1488          */
1489         private function makeQueryException( $error, $errno, $sql, $fname ) {
1490                 $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1491                 $this->queryLogger->error(
1492                         "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1493                         $this->getLogContext( [
1494                                 'method' => __METHOD__,
1495                                 'errno' => $errno,
1496                                 'error' => $error,
1497                                 'sql1line' => $sql1line,
1498                                 'fname' => $fname,
1499                         ] )
1500                 );
1501                 $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1502                 $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1503                 if ( $wasQueryTimeout ) {
1504                         $e = new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1505                 } else {
1506                         $e = new DBQueryError( $this, $error, $errno, $sql, $fname );
1507                 }
1508
1509                 return $e;
1510         }
1511
1512         public function freeResult( $res ) {
1513         }
1514
1515         public function selectField(
1516                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1517         ) {
1518                 if ( $var === '*' ) { // sanity
1519                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1520                 }
1521
1522                 if ( !is_array( $options ) ) {
1523                         $options = [ $options ];
1524                 }
1525
1526                 $options['LIMIT'] = 1;
1527
1528                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1529                 if ( $res === false || !$this->numRows( $res ) ) {
1530                         return false;
1531                 }
1532
1533                 $row = $this->fetchRow( $res );
1534
1535                 if ( $row !== false ) {
1536                         return reset( $row );
1537                 } else {
1538                         return false;
1539                 }
1540         }
1541
1542         public function selectFieldValues(
1543                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1544         ) {
1545                 if ( $var === '*' ) { // sanity
1546                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1547                 } elseif ( !is_string( $var ) ) { // sanity
1548                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1549                 }
1550
1551                 if ( !is_array( $options ) ) {
1552                         $options = [ $options ];
1553                 }
1554
1555                 $res = $this->select( $table, [ 'value' => $var ], $cond, $fname, $options, $join_conds );
1556                 if ( $res === false ) {
1557                         return false;
1558                 }
1559
1560                 $values = [];
1561                 foreach ( $res as $row ) {
1562                         $values[] = $row->value;
1563                 }
1564
1565                 return $values;
1566         }
1567
1568         /**
1569          * Returns an optional USE INDEX clause to go after the table, and a
1570          * string to go at the end of the query.
1571          *
1572          * @param array $options Associative array of options to be turned into
1573          *   an SQL query, valid keys are listed in the function.
1574          * @return array
1575          * @see Database::select()
1576          */
1577         protected function makeSelectOptions( $options ) {
1578                 $preLimitTail = $postLimitTail = '';
1579                 $startOpts = '';
1580
1581                 $noKeyOptions = [];
1582
1583                 foreach ( $options as $key => $option ) {
1584                         if ( is_numeric( $key ) ) {
1585                                 $noKeyOptions[$option] = true;
1586                         }
1587                 }
1588
1589                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1590
1591                 $preLimitTail .= $this->makeOrderBy( $options );
1592
1593                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1594                         $postLimitTail .= ' FOR UPDATE';
1595                 }
1596
1597                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1598                         $postLimitTail .= ' LOCK IN SHARE MODE';
1599                 }
1600
1601                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1602                         $startOpts .= 'DISTINCT';
1603                 }
1604
1605                 # Various MySQL extensions
1606                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1607                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1608                 }
1609
1610                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1611                         $startOpts .= ' HIGH_PRIORITY';
1612                 }
1613
1614                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1615                         $startOpts .= ' SQL_BIG_RESULT';
1616                 }
1617
1618                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1619                         $startOpts .= ' SQL_BUFFER_RESULT';
1620                 }
1621
1622                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1623                         $startOpts .= ' SQL_SMALL_RESULT';
1624                 }
1625
1626                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1627                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1628                 }
1629
1630                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1631                         $startOpts .= ' SQL_CACHE';
1632                 }
1633
1634                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1635                         $startOpts .= ' SQL_NO_CACHE';
1636                 }
1637
1638                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1639                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1640                 } else {
1641                         $useIndex = '';
1642                 }
1643                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1644                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1645                 } else {
1646                         $ignoreIndex = '';
1647                 }
1648
1649                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1650         }
1651
1652         /**
1653          * Returns an optional GROUP BY with an optional HAVING
1654          *
1655          * @param array $options Associative array of options
1656          * @return string
1657          * @see Database::select()
1658          * @since 1.21
1659          */
1660         protected function makeGroupByWithHaving( $options ) {
1661                 $sql = '';
1662                 if ( isset( $options['GROUP BY'] ) ) {
1663                         $gb = is_array( $options['GROUP BY'] )
1664                                 ? implode( ',', $options['GROUP BY'] )
1665                                 : $options['GROUP BY'];
1666                         $sql .= ' GROUP BY ' . $gb;
1667                 }
1668                 if ( isset( $options['HAVING'] ) ) {
1669                         $having = is_array( $options['HAVING'] )
1670                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1671                                 : $options['HAVING'];
1672                         $sql .= ' HAVING ' . $having;
1673                 }
1674
1675                 return $sql;
1676         }
1677
1678         /**
1679          * Returns an optional ORDER BY
1680          *
1681          * @param array $options Associative array of options
1682          * @return string
1683          * @see Database::select()
1684          * @since 1.21
1685          */
1686         protected function makeOrderBy( $options ) {
1687                 if ( isset( $options['ORDER BY'] ) ) {
1688                         $ob = is_array( $options['ORDER BY'] )
1689                                 ? implode( ',', $options['ORDER BY'] )
1690                                 : $options['ORDER BY'];
1691
1692                         return ' ORDER BY ' . $ob;
1693                 }
1694
1695                 return '';
1696         }
1697
1698         public function select(
1699                 $table, $vars, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1700         ) {
1701                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1702
1703                 return $this->query( $sql, $fname );
1704         }
1705
1706         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1707                 $options = [], $join_conds = []
1708         ) {
1709                 if ( is_array( $vars ) ) {
1710                         $fields = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1711                 } else {
1712                         $fields = $vars;
1713                 }
1714
1715                 $options = (array)$options;
1716                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1717                         ? $options['USE INDEX']
1718                         : [];
1719                 $ignoreIndexes = (
1720                         isset( $options['IGNORE INDEX'] ) &&
1721                         is_array( $options['IGNORE INDEX'] )
1722                 )
1723                         ? $options['IGNORE INDEX']
1724                         : [];
1725
1726                 if (
1727                         $this->selectOptionsIncludeLocking( $options ) &&
1728                         $this->selectFieldsOrOptionsAggregate( $vars, $options )
1729                 ) {
1730                         // Some DB types (postgres/oracle) disallow FOR UPDATE with aggregate
1731                         // functions. Discourage use of such queries to encourage compatibility.
1732                         call_user_func(
1733                                 $this->deprecationLogger,
1734                                 __METHOD__ . ": aggregation used with a locking SELECT ($fname)."
1735                         );
1736                 }
1737
1738                 if ( is_array( $table ) ) {
1739                         $from = ' FROM ' .
1740                                 $this->tableNamesWithIndexClauseOrJOIN(
1741                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1742                 } elseif ( $table != '' ) {
1743                         $from = ' FROM ' .
1744                                 $this->tableNamesWithIndexClauseOrJOIN(
1745                                         [ $table ], $useIndexes, $ignoreIndexes, [] );
1746                 } else {
1747                         $from = '';
1748                 }
1749
1750                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1751                         $this->makeSelectOptions( $options );
1752
1753                 if ( is_array( $conds ) ) {
1754                         $conds = $this->makeList( $conds, self::LIST_AND );
1755                 }
1756
1757                 if ( $conds === null || $conds === false ) {
1758                         $this->queryLogger->warning(
1759                                 __METHOD__
1760                                 . ' called from '
1761                                 . $fname
1762                                 . ' with incorrect parameters: $conds must be a string or an array'
1763                         );
1764                         $conds = '';
1765                 }
1766
1767                 if ( $conds === '' || $conds === '*' ) {
1768                         $sql = "SELECT $startOpts $fields $from $useIndex $ignoreIndex $preLimitTail";
1769                 } elseif ( is_string( $conds ) ) {
1770                         $sql = "SELECT $startOpts $fields $from $useIndex $ignoreIndex " .
1771                                 "WHERE $conds $preLimitTail";
1772                 } else {
1773                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1774                 }
1775
1776                 if ( isset( $options['LIMIT'] ) ) {
1777                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1778                                 $options['OFFSET'] ?? false );
1779                 }
1780                 $sql = "$sql $postLimitTail";
1781
1782                 if ( isset( $options['EXPLAIN'] ) ) {
1783                         $sql = 'EXPLAIN ' . $sql;
1784                 }
1785
1786                 return $sql;
1787         }
1788
1789         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1790                 $options = [], $join_conds = []
1791         ) {
1792                 $options = (array)$options;
1793                 $options['LIMIT'] = 1;
1794                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1795
1796                 if ( $res === false ) {
1797                         return false;
1798                 }
1799
1800                 if ( !$this->numRows( $res ) ) {
1801                         return false;
1802                 }
1803
1804                 $obj = $this->fetchObject( $res );
1805
1806                 return $obj;
1807         }
1808
1809         public function estimateRowCount(
1810                 $table, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1811         ) {
1812                 $conds = $this->normalizeConditions( $conds, $fname );
1813                 $column = $this->extractSingleFieldFromList( $var );
1814                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1815                         $conds[] = "$column IS NOT NULL";
1816                 }
1817
1818                 $res = $this->select(
1819                         $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options, $join_conds
1820                 );
1821                 $row = $res ? $this->fetchRow( $res ) : [];
1822
1823                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1824         }
1825
1826         public function selectRowCount(
1827                 $tables, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1828         ) {
1829                 $conds = $this->normalizeConditions( $conds, $fname );
1830                 $column = $this->extractSingleFieldFromList( $var );
1831                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1832                         $conds[] = "$column IS NOT NULL";
1833                 }
1834
1835                 $res = $this->select(
1836                         [
1837                                 'tmp_count' => $this->buildSelectSubquery(
1838                                         $tables,
1839                                         '1',
1840                                         $conds,
1841                                         $fname,
1842                                         $options,
1843                                         $join_conds
1844                                 )
1845                         ],
1846                         [ 'rowcount' => 'COUNT(*)' ],
1847                         [],
1848                         $fname
1849                 );
1850                 $row = $res ? $this->fetchRow( $res ) : [];
1851
1852                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1853         }
1854
1855         /**
1856          * @param string|array $options
1857          * @return bool
1858          */
1859         private function selectOptionsIncludeLocking( $options ) {
1860                 $options = (array)$options;
1861                 foreach ( [ 'FOR UPDATE', 'LOCK IN SHARE MODE' ] as $lock ) {
1862                         if ( in_array( $lock, $options, true ) ) {
1863                                 return true;
1864                         }
1865                 }
1866
1867                 return false;
1868         }
1869
1870         /**
1871          * @param array|string $fields
1872          * @param array|string $options
1873          * @return bool
1874          */
1875         private function selectFieldsOrOptionsAggregate( $fields, $options ) {
1876                 foreach ( (array)$options as $key => $value ) {
1877                         if ( is_string( $key ) ) {
1878                                 if ( preg_match( '/^(?:GROUP BY|HAVING)$/i', $key ) ) {
1879                                         return true;
1880                                 }
1881                         } elseif ( is_string( $value ) ) {
1882                                 if ( preg_match( '/^(?:DISTINCT|DISTINCTROW)$/i', $value ) ) {
1883                                         return true;
1884                                 }
1885                         }
1886                 }
1887
1888                 $regex = '/^(?:COUNT|MIN|MAX|SUM|GROUP_CONCAT|LISTAGG|ARRAY_AGG)\s*\\(/i';
1889                 foreach ( (array)$fields as $field ) {
1890                         if ( is_string( $field ) && preg_match( $regex, $field ) ) {
1891                                 return true;
1892                         }
1893                 }
1894
1895                 return false;
1896         }
1897
1898         /**
1899          * @param array|string $conds
1900          * @param string $fname
1901          * @return array
1902          */
1903         final protected function normalizeConditions( $conds, $fname ) {
1904                 if ( $conds === null || $conds === false ) {
1905                         $this->queryLogger->warning(
1906                                 __METHOD__
1907                                 . ' called from '
1908                                 . $fname
1909                                 . ' with incorrect parameters: $conds must be a string or an array'
1910                         );
1911                         $conds = '';
1912                 }
1913
1914                 if ( !is_array( $conds ) ) {
1915                         $conds = ( $conds === '' ) ? [] : [ $conds ];
1916                 }
1917
1918                 return $conds;
1919         }
1920
1921         /**
1922          * @param array|string $var Field parameter in the style of select()
1923          * @return string|null Column name or null; ignores aliases
1924          * @throws DBUnexpectedError Errors out if multiple columns are given
1925          */
1926         final protected function extractSingleFieldFromList( $var ) {
1927                 if ( is_array( $var ) ) {
1928                         if ( !$var ) {
1929                                 $column = null;
1930                         } elseif ( count( $var ) == 1 ) {
1931                                 $column = $var[0] ?? reset( $var );
1932                         } else {
1933                                 throw new DBUnexpectedError( $this, __METHOD__ . ': got multiple columns.' );
1934                         }
1935                 } else {
1936                         $column = $var;
1937                 }
1938
1939                 return $column;
1940         }
1941
1942         public function lockForUpdate(
1943                 $table, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1944         ) {
1945                 if ( !$this->trxLevel && !$this->getFlag( self::DBO_TRX ) ) {
1946                         throw new DBUnexpectedError(
1947                                 $this,
1948                                 __METHOD__ . ': no transaction is active nor is DBO_TRX set'
1949                         );
1950                 }
1951
1952                 $options = (array)$options;
1953                 $options[] = 'FOR UPDATE';
1954
1955                 return $this->selectRowCount( $table, '*', $conds, $fname, $options, $join_conds );
1956         }
1957
1958         /**
1959          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1960          * It's only slightly flawed. Don't use for anything important.
1961          *
1962          * @param string $sql A SQL Query
1963          *
1964          * @return string
1965          */
1966         protected static function generalizeSQL( $sql ) {
1967                 # This does the same as the regexp below would do, but in such a way
1968                 # as to avoid crashing php on some large strings.
1969                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1970
1971                 $sql = str_replace( "\\\\", '', $sql );
1972                 $sql = str_replace( "\\'", '', $sql );
1973                 $sql = str_replace( "\\\"", '', $sql );
1974                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1975                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1976
1977                 # All newlines, tabs, etc replaced by single space
1978                 $sql = preg_replace( '/\s+/', ' ', $sql );
1979
1980                 # All numbers => N,
1981                 # except the ones surrounded by characters, e.g. l10n
1982                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1983                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1984
1985                 return $sql;
1986         }
1987
1988         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1989                 $info = $this->fieldInfo( $table, $field );
1990
1991                 return (bool)$info;
1992         }
1993
1994         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1995                 if ( !$this->tableExists( $table ) ) {
1996                         return null;
1997                 }
1998
1999                 $info = $this->indexInfo( $table, $index, $fname );
2000                 if ( is_null( $info ) ) {
2001                         return null;
2002                 } else {
2003                         return $info !== false;
2004                 }
2005         }
2006
2007         abstract public function tableExists( $table, $fname = __METHOD__ );
2008
2009         public function indexUnique( $table, $index ) {
2010                 $indexInfo = $this->indexInfo( $table, $index );
2011
2012                 if ( !$indexInfo ) {
2013                         return null;
2014                 }
2015
2016                 return !$indexInfo[0]->Non_unique;
2017         }
2018
2019         /**
2020          * Helper for Database::insert().
2021          *
2022          * @param array $options
2023          * @return string
2024          */
2025         protected function makeInsertOptions( $options ) {
2026                 return implode( ' ', $options );
2027         }
2028
2029         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
2030                 # No rows to insert, easy just return now
2031                 if ( !count( $a ) ) {
2032                         return true;
2033                 }
2034
2035                 $table = $this->tableName( $table );
2036
2037                 if ( !is_array( $options ) ) {
2038                         $options = [ $options ];
2039                 }
2040
2041                 $fh = null;
2042                 if ( isset( $options['fileHandle'] ) ) {
2043                         $fh = $options['fileHandle'];
2044                 }
2045                 $options = $this->makeInsertOptions( $options );
2046
2047                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
2048                         $multi = true;
2049                         $keys = array_keys( $a[0] );
2050                 } else {
2051                         $multi = false;
2052                         $keys = array_keys( $a );
2053                 }
2054
2055                 $sql = 'INSERT ' . $options .
2056                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
2057
2058                 if ( $multi ) {
2059                         $first = true;
2060                         foreach ( $a as $row ) {
2061                                 if ( $first ) {
2062                                         $first = false;
2063                                 } else {
2064                                         $sql .= ',';
2065                                 }
2066                                 $sql .= '(' . $this->makeList( $row ) . ')';
2067                         }
2068                 } else {
2069                         $sql .= '(' . $this->makeList( $a ) . ')';
2070                 }
2071
2072                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
2073                         return false;
2074                 } elseif ( $fh !== null ) {
2075                         return true;
2076                 }
2077
2078                 return (bool)$this->query( $sql, $fname );
2079         }
2080
2081         /**
2082          * Make UPDATE options array for Database::makeUpdateOptions
2083          *
2084          * @param array $options
2085          * @return array
2086          */
2087         protected function makeUpdateOptionsArray( $options ) {
2088                 if ( !is_array( $options ) ) {
2089                         $options = [ $options ];
2090                 }
2091
2092                 $opts = [];
2093
2094                 if ( in_array( 'IGNORE', $options ) ) {
2095                         $opts[] = 'IGNORE';
2096                 }
2097
2098                 return $opts;
2099         }
2100
2101         /**
2102          * Make UPDATE options for the Database::update function
2103          *
2104          * @param array $options The options passed to Database::update
2105          * @return string
2106          */
2107         protected function makeUpdateOptions( $options ) {
2108                 $opts = $this->makeUpdateOptionsArray( $options );
2109
2110                 return implode( ' ', $opts );
2111         }
2112
2113         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
2114                 $table = $this->tableName( $table );
2115                 $opts = $this->makeUpdateOptions( $options );
2116                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
2117
2118                 if ( $conds !== [] && $conds !== '*' ) {
2119                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
2120                 }
2121
2122                 return (bool)$this->query( $sql, $fname );
2123         }
2124
2125         public function makeList( $a, $mode = self::LIST_COMMA ) {
2126                 if ( !is_array( $a ) ) {
2127                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
2128                 }
2129
2130                 $first = true;
2131                 $list = '';
2132
2133                 foreach ( $a as $field => $value ) {
2134                         if ( !$first ) {
2135                                 if ( $mode == self::LIST_AND ) {
2136                                         $list .= ' AND ';
2137                                 } elseif ( $mode == self::LIST_OR ) {
2138                                         $list .= ' OR ';
2139                                 } else {
2140                                         $list .= ',';
2141                                 }
2142                         } else {
2143                                 $first = false;
2144                         }
2145
2146                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
2147                                 $list .= "($value)";
2148                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
2149                                 $list .= "$value";
2150                         } elseif (
2151                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
2152                         ) {
2153                                 // Remove null from array to be handled separately if found
2154                                 $includeNull = false;
2155                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
2156                                         $includeNull = true;
2157                                         unset( $value[$nullKey] );
2158                                 }
2159                                 if ( count( $value ) == 0 && !$includeNull ) {
2160                                         throw new InvalidArgumentException(
2161                                                 __METHOD__ . ": empty input for field $field" );
2162                                 } elseif ( count( $value ) == 0 ) {
2163                                         // only check if $field is null
2164                                         $list .= "$field IS NULL";
2165                                 } else {
2166                                         // IN clause contains at least one valid element
2167                                         if ( $includeNull ) {
2168                                                 // Group subconditions to ensure correct precedence
2169                                                 $list .= '(';
2170                                         }
2171                                         if ( count( $value ) == 1 ) {
2172                                                 // Special-case single values, as IN isn't terribly efficient
2173                                                 // Don't necessarily assume the single key is 0; we don't
2174                                                 // enforce linear numeric ordering on other arrays here.
2175                                                 $value = array_values( $value )[0];
2176                                                 $list .= $field . " = " . $this->addQuotes( $value );
2177                                         } else {
2178                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
2179                                         }
2180                                         // if null present in array, append IS NULL
2181                                         if ( $includeNull ) {
2182                                                 $list .= " OR $field IS NULL)";
2183                                         }
2184                                 }
2185                         } elseif ( $value === null ) {
2186                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
2187                                         $list .= "$field IS ";
2188                                 } elseif ( $mode == self::LIST_SET ) {
2189                                         $list .= "$field = ";
2190                                 }
2191                                 $list .= 'NULL';
2192                         } else {
2193                                 if (
2194                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
2195                                 ) {
2196                                         $list .= "$field = ";
2197                                 }
2198                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
2199                         }
2200                 }
2201
2202                 return $list;
2203         }
2204
2205         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2206                 $conds = [];
2207
2208                 foreach ( $data as $base => $sub ) {
2209                         if ( count( $sub ) ) {
2210                                 $conds[] = $this->makeList(
2211                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
2212                                         self::LIST_AND );
2213                         }
2214                 }
2215
2216                 if ( $conds ) {
2217                         return $this->makeList( $conds, self::LIST_OR );
2218                 } else {
2219                         // Nothing to search for...
2220                         return false;
2221                 }
2222         }
2223
2224         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2225                 return $valuename;
2226         }
2227
2228         public function bitNot( $field ) {
2229                 return "(~$field)";
2230         }
2231
2232         public function bitAnd( $fieldLeft, $fieldRight ) {
2233                 return "($fieldLeft & $fieldRight)";
2234         }
2235
2236         public function bitOr( $fieldLeft, $fieldRight ) {
2237                 return "($fieldLeft | $fieldRight)";
2238         }
2239
2240         public function buildConcat( $stringList ) {
2241                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2242         }
2243
2244         public function buildGroupConcatField(
2245                 $delim, $table, $field, $conds = '', $join_conds = []
2246         ) {
2247                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
2248
2249                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
2250         }
2251
2252         public function buildSubstring( $input, $startPosition, $length = null ) {
2253                 $this->assertBuildSubstringParams( $startPosition, $length );
2254                 $functionBody = "$input FROM $startPosition";
2255                 if ( $length !== null ) {
2256                         $functionBody .= " FOR $length";
2257                 }
2258                 return 'SUBSTRING(' . $functionBody . ')';
2259         }
2260
2261         /**
2262          * Check type and bounds for parameters to self::buildSubstring()
2263          *
2264          * All supported databases have substring functions that behave the same for
2265          * positive $startPosition and non-negative $length, but behaviors differ when
2266          * given 0 or negative $startPosition or negative $length. The simplest
2267          * solution to that is to just forbid those values.
2268          *
2269          * @param int $startPosition
2270          * @param int|null $length
2271          * @since 1.31
2272          */
2273         protected function assertBuildSubstringParams( $startPosition, $length ) {
2274                 if ( !is_int( $startPosition ) || $startPosition <= 0 ) {
2275                         throw new InvalidArgumentException(
2276                                 '$startPosition must be a positive integer'
2277                         );
2278                 }
2279                 if ( !( is_int( $length ) && $length >= 0 || $length === null ) ) {
2280                         throw new InvalidArgumentException(
2281                                 '$length must be null or an integer greater than or equal to 0'
2282                         );
2283                 }
2284         }
2285
2286         public function buildStringCast( $field ) {
2287                 return $field;
2288         }
2289
2290         public function buildIntegerCast( $field ) {
2291                 return 'CAST( ' . $field . ' AS INTEGER )';
2292         }
2293
2294         public function buildSelectSubquery(
2295                 $table, $vars, $conds = '', $fname = __METHOD__,
2296                 $options = [], $join_conds = []
2297         ) {
2298                 return new Subquery(
2299                         $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds )
2300                 );
2301         }
2302
2303         public function databasesAreIndependent() {
2304                 return false;
2305         }
2306
2307         final public function selectDB( $db ) {
2308                 $this->selectDomain( new DatabaseDomain(
2309                         $db,
2310                         $this->currentDomain->getSchema(),
2311                         $this->currentDomain->getTablePrefix()
2312                 ) );
2313
2314                 return true;
2315         }
2316
2317         final public function selectDomain( $domain ) {
2318                 $this->doSelectDomain( DatabaseDomain::newFromId( $domain ) );
2319         }
2320
2321         protected function doSelectDomain( DatabaseDomain $domain ) {
2322                 $this->currentDomain = $domain;
2323         }
2324
2325         public function getDBname() {
2326                 return $this->currentDomain->getDatabase();
2327         }
2328
2329         public function getServer() {
2330                 return $this->server;
2331         }
2332
2333         public function tableName( $name, $format = 'quoted' ) {
2334                 if ( $name instanceof Subquery ) {
2335                         throw new DBUnexpectedError(
2336                                 $this,
2337                                 __METHOD__ . ': got Subquery instance when expecting a string.'
2338                         );
2339                 }
2340
2341                 # Skip the entire process when we have a string quoted on both ends.
2342                 # Note that we check the end so that we will still quote any use of
2343                 # use of `database`.table. But won't break things if someone wants
2344                 # to query a database table with a dot in the name.
2345                 if ( $this->isQuotedIdentifier( $name ) ) {
2346                         return $name;
2347                 }
2348
2349                 # Lets test for any bits of text that should never show up in a table
2350                 # name. Basically anything like JOIN or ON which are actually part of
2351                 # SQL queries, but may end up inside of the table value to combine
2352                 # sql. Such as how the API is doing.
2353                 # Note that we use a whitespace test rather than a \b test to avoid
2354                 # any remote case where a word like on may be inside of a table name
2355                 # surrounded by symbols which may be considered word breaks.
2356                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2357                         $this->queryLogger->warning(
2358                                 __METHOD__ . ": use of subqueries is not supported this way.",
2359                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
2360                         );
2361
2362                         return $name;
2363                 }
2364
2365                 # Split database and table into proper variables.
2366                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
2367
2368                 # Quote $table and apply the prefix if not quoted.
2369                 # $tableName might be empty if this is called from Database::replaceVars()
2370                 $tableName = "{$prefix}{$table}";
2371                 if ( $format === 'quoted'
2372                         && !$this->isQuotedIdentifier( $tableName )
2373                         && $tableName !== ''
2374                 ) {
2375                         $tableName = $this->addIdentifierQuotes( $tableName );
2376                 }
2377
2378                 # Quote $schema and $database and merge them with the table name if needed
2379                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
2380                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
2381
2382                 return $tableName;
2383         }
2384
2385         /**
2386          * Get the table components needed for a query given the currently selected database
2387          *
2388          * @param string $name Table name in the form of db.schema.table, db.table, or table
2389          * @return array (DB name or "" for default, schema name, table prefix, table name)
2390          */
2391         protected function qualifiedTableComponents( $name ) {
2392                 # We reverse the explode so that database.table and table both output the correct table.
2393                 $dbDetails = explode( '.', $name, 3 );
2394                 if ( count( $dbDetails ) == 3 ) {
2395                         list( $database, $schema, $table ) = $dbDetails;
2396                         # We don't want any prefix added in this case
2397                         $prefix = '';
2398                 } elseif ( count( $dbDetails ) == 2 ) {
2399                         list( $database, $table ) = $dbDetails;
2400                         # We don't want any prefix added in this case
2401                         $prefix = '';
2402                         # In dbs that support it, $database may actually be the schema
2403                         # but that doesn't affect any of the functionality here
2404                         $schema = '';
2405                 } else {
2406                         list( $table ) = $dbDetails;
2407                         if ( isset( $this->tableAliases[$table] ) ) {
2408                                 $database = $this->tableAliases[$table]['dbname'];
2409                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
2410                                         ? $this->tableAliases[$table]['schema']
2411                                         : $this->relationSchemaQualifier();
2412                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
2413                                         ? $this->tableAliases[$table]['prefix']
2414                                         : $this->tablePrefix();
2415                         } else {
2416                                 $database = '';
2417                                 $schema = $this->relationSchemaQualifier(); # Default schema
2418                                 $prefix = $this->tablePrefix(); # Default prefix
2419                         }
2420                 }
2421
2422                 return [ $database, $schema, $prefix, $table ];
2423         }
2424
2425         /**
2426          * @param string|null $namespace Database or schema
2427          * @param string $relation Name of table, view, sequence, etc...
2428          * @param string $format One of (raw, quoted)
2429          * @return string Relation name with quoted and merged $namespace as needed
2430          */
2431         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
2432                 if ( strlen( $namespace ) ) {
2433                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
2434                                 $namespace = $this->addIdentifierQuotes( $namespace );
2435                         }
2436                         $relation = $namespace . '.' . $relation;
2437                 }
2438
2439                 return $relation;
2440         }
2441
2442         public function tableNames() {
2443                 $inArray = func_get_args();
2444                 $retVal = [];
2445
2446                 foreach ( $inArray as $name ) {
2447                         $retVal[$name] = $this->tableName( $name );
2448                 }
2449
2450                 return $retVal;
2451         }
2452
2453         public function tableNamesN() {
2454                 $inArray = func_get_args();
2455                 $retVal = [];
2456
2457                 foreach ( $inArray as $name ) {
2458                         $retVal[] = $this->tableName( $name );
2459                 }
2460
2461                 return $retVal;
2462         }
2463
2464         /**
2465          * Get an aliased table name
2466          *
2467          * This returns strings like "tableName AS newTableName" for aliased tables
2468          * and "(SELECT * from tableA) newTablename" for subqueries (e.g. derived tables)
2469          *
2470          * @see Database::tableName()
2471          * @param string|Subquery $table Table name or object with a 'sql' field
2472          * @param string|bool $alias Table alias (optional)
2473          * @return string SQL name for aliased table. Will not alias a table to its own name
2474          */
2475         protected function tableNameWithAlias( $table, $alias = false ) {
2476                 if ( is_string( $table ) ) {
2477                         $quotedTable = $this->tableName( $table );
2478                 } elseif ( $table instanceof Subquery ) {
2479                         $quotedTable = (string)$table;
2480                 } else {
2481                         throw new InvalidArgumentException( "Table must be a string or Subquery." );
2482                 }
2483
2484                 if ( !strlen( $alias ) || $alias === $table ) {
2485                         if ( $table instanceof Subquery ) {
2486                                 throw new InvalidArgumentException( "Subquery table missing alias." );
2487                         }
2488
2489                         return $quotedTable;
2490                 } else {
2491                         return $quotedTable . ' ' . $this->addIdentifierQuotes( $alias );
2492                 }
2493         }
2494
2495         /**
2496          * Gets an array of aliased table names
2497          *
2498          * @param array $tables [ [alias] => table ]
2499          * @return string[] See tableNameWithAlias()
2500          */
2501         protected function tableNamesWithAlias( $tables ) {
2502                 $retval = [];
2503                 foreach ( $tables as $alias => $table ) {
2504                         if ( is_numeric( $alias ) ) {
2505                                 $alias = $table;
2506                         }
2507                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2508                 }
2509
2510                 return $retval;
2511         }
2512
2513         /**
2514          * Get an aliased field name
2515          * e.g. fieldName AS newFieldName
2516          *
2517          * @param string $name Field name
2518          * @param string|bool $alias Alias (optional)
2519          * @return string SQL name for aliased field. Will not alias a field to its own name
2520          */
2521         protected function fieldNameWithAlias( $name, $alias = false ) {
2522                 if ( !$alias || (string)$alias === (string)$name ) {
2523                         return $name;
2524                 } else {
2525                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
2526                 }
2527         }
2528
2529         /**
2530          * Gets an array of aliased field names
2531          *
2532          * @param array $fields [ [alias] => field ]
2533          * @return string[] See fieldNameWithAlias()
2534          */
2535         protected function fieldNamesWithAlias( $fields ) {
2536                 $retval = [];
2537                 foreach ( $fields as $alias => $field ) {
2538                         if ( is_numeric( $alias ) ) {
2539                                 $alias = $field;
2540                         }
2541                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2542                 }
2543
2544                 return $retval;
2545         }
2546
2547         /**
2548          * Get the aliased table name clause for a FROM clause
2549          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2550          *
2551          * @param array $tables ( [alias] => table )
2552          * @param array $use_index Same as for select()
2553          * @param array $ignore_index Same as for select()
2554          * @param array $join_conds Same as for select()
2555          * @return string
2556          */
2557         protected function tableNamesWithIndexClauseOrJOIN(
2558                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2559         ) {
2560                 $ret = [];
2561                 $retJOIN = [];
2562                 $use_index = (array)$use_index;
2563                 $ignore_index = (array)$ignore_index;
2564                 $join_conds = (array)$join_conds;
2565
2566                 foreach ( $tables as $alias => $table ) {
2567                         if ( !is_string( $alias ) ) {
2568                                 // No alias? Set it equal to the table name
2569                                 $alias = $table;
2570                         }
2571
2572                         if ( is_array( $table ) ) {
2573                                 // A parenthesized group
2574                                 if ( count( $table ) > 1 ) {
2575                                         $joinedTable = '(' .
2576                                                 $this->tableNamesWithIndexClauseOrJOIN(
2577                                                         $table, $use_index, $ignore_index, $join_conds ) . ')';
2578                                 } else {
2579                                         // Degenerate case
2580                                         $innerTable = reset( $table );
2581                                         $innerAlias = key( $table );
2582                                         $joinedTable = $this->tableNameWithAlias(
2583                                                 $innerTable,
2584                                                 is_string( $innerAlias ) ? $innerAlias : $innerTable
2585                                         );
2586                                 }
2587                         } else {
2588                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2589                         }
2590
2591                         // Is there a JOIN clause for this table?
2592                         if ( isset( $join_conds[$alias] ) ) {
2593                                 list( $joinType, $conds ) = $join_conds[$alias];
2594                                 $tableClause = $joinType;
2595                                 $tableClause .= ' ' . $joinedTable;
2596                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2597                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2598                                         if ( $use != '' ) {
2599                                                 $tableClause .= ' ' . $use;
2600                                         }
2601                                 }
2602                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2603                                         $ignore = $this->ignoreIndexClause(
2604                                                 implode( ',', (array)$ignore_index[$alias] ) );
2605                                         if ( $ignore != '' ) {
2606                                                 $tableClause .= ' ' . $ignore;
2607                                         }
2608                                 }
2609                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2610                                 if ( $on != '' ) {
2611                                         $tableClause .= ' ON (' . $on . ')';
2612                                 }
2613
2614                                 $retJOIN[] = $tableClause;
2615                         } elseif ( isset( $use_index[$alias] ) ) {
2616                                 // Is there an INDEX clause for this table?
2617                                 $tableClause = $joinedTable;
2618                                 $tableClause .= ' ' . $this->useIndexClause(
2619                                                 implode( ',', (array)$use_index[$alias] )
2620                                         );
2621
2622                                 $ret[] = $tableClause;
2623                         } elseif ( isset( $ignore_index[$alias] ) ) {
2624                                 // Is there an INDEX clause for this table?
2625                                 $tableClause = $joinedTable;
2626                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2627                                                 implode( ',', (array)$ignore_index[$alias] )
2628                                         );
2629
2630                                 $ret[] = $tableClause;
2631                         } else {
2632                                 $tableClause = $joinedTable;
2633
2634                                 $ret[] = $tableClause;
2635                         }
2636                 }
2637
2638                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2639                 $implicitJoins = $ret ? implode( ',', $ret ) : "";
2640                 $explicitJoins = $retJOIN ? implode( ' ', $retJOIN ) : "";
2641
2642                 // Compile our final table clause
2643                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2644         }
2645
2646         /**
2647          * Allows for index remapping in queries where this is not consistent across DBMS
2648          *
2649          * @param string $index
2650          * @return string
2651          */
2652         protected function indexName( $index ) {
2653                 return $this->indexAliases[$index] ?? $index;
2654         }
2655
2656         public function addQuotes( $s ) {
2657                 if ( $s instanceof Blob ) {
2658                         $s = $s->fetch();
2659                 }
2660                 if ( $s === null ) {
2661                         return 'NULL';
2662                 } elseif ( is_bool( $s ) ) {
2663                         return (int)$s;
2664                 } else {
2665                         # This will also quote numeric values. This should be harmless,
2666                         # and protects against weird problems that occur when they really
2667                         # _are_ strings such as article titles and string->number->string
2668                         # conversion is not 1:1.
2669                         return "'" . $this->strencode( $s ) . "'";
2670                 }
2671         }
2672
2673         /**
2674          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2675          * MySQL uses `backticks` while basically everything else uses double quotes.
2676          * Since MySQL is the odd one out here the double quotes are our generic
2677          * and we implement backticks in DatabaseMysqlBase.
2678          *
2679          * @param string $s
2680          * @return string
2681          */
2682         public function addIdentifierQuotes( $s ) {
2683                 return '"' . str_replace( '"', '""', $s ) . '"';
2684         }
2685
2686         /**
2687          * Returns if the given identifier looks quoted or not according to
2688          * the database convention for quoting identifiers .
2689          *
2690          * @note Do not use this to determine if untrusted input is safe.
2691          *   A malicious user can trick this function.
2692          * @param string $name
2693          * @return bool
2694          */
2695         public function isQuotedIdentifier( $name ) {
2696                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2697         }
2698
2699         /**
2700          * @param string $s
2701          * @param string $escapeChar
2702          * @return string
2703          */
2704         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2705                 return str_replace( [ $escapeChar, '%', '_' ],
2706                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2707                         $s );
2708         }
2709
2710         public function buildLike() {
2711                 $params = func_get_args();
2712
2713                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2714                         $params = $params[0];
2715                 }
2716
2717                 $s = '';
2718
2719                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2720                 // may escape backslashes, creating problems of double escaping. The `
2721                 // character has good cross-DBMS compatibility, avoiding special operators
2722                 // in MS SQL like ^ and %
2723                 $escapeChar = '`';
2724
2725                 foreach ( $params as $value ) {
2726                         if ( $value instanceof LikeMatch ) {
2727                                 $s .= $value->toString();
2728                         } else {
2729                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2730                         }
2731                 }
2732
2733                 return ' LIKE ' .
2734                         $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2735         }
2736
2737         public function anyChar() {
2738                 return new LikeMatch( '_' );
2739         }
2740
2741         public function anyString() {
2742                 return new LikeMatch( '%' );
2743         }
2744
2745         public function nextSequenceValue( $seqName ) {
2746                 return null;
2747         }
2748
2749         /**
2750          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2751          * is only needed because a) MySQL must be as efficient as possible due to
2752          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2753          * which index to pick. Anyway, other databases might have different
2754          * indexes on a given table. So don't bother overriding this unless you're
2755          * MySQL.
2756          * @param string $index
2757          * @return string
2758          */
2759         public function useIndexClause( $index ) {
2760                 return '';
2761         }
2762
2763         /**
2764          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2765          * is only needed because a) MySQL must be as efficient as possible due to
2766          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2767          * which index to pick. Anyway, other databases might have different
2768          * indexes on a given table. So don't bother overriding this unless you're
2769          * MySQL.
2770          * @param string $index
2771          * @return string
2772          */
2773         public function ignoreIndexClause( $index ) {
2774                 return '';
2775         }
2776
2777         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2778                 if ( count( $rows ) == 0 ) {
2779                         return;
2780                 }
2781
2782                 // Single row case
2783                 if ( !is_array( reset( $rows ) ) ) {
2784                         $rows = [ $rows ];
2785                 }
2786
2787                 try {
2788                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2789                         $affectedRowCount = 0;
2790                         foreach ( $rows as $row ) {
2791                                 // Delete rows which collide with this one
2792                                 $indexWhereClauses = [];
2793                                 foreach ( $uniqueIndexes as $index ) {
2794                                         $indexColumns = (array)$index;
2795                                         $indexRowValues = array_intersect_key( $row, array_flip( $indexColumns ) );
2796                                         if ( count( $indexRowValues ) != count( $indexColumns ) ) {
2797                                                 throw new DBUnexpectedError(
2798                                                         $this,
2799                                                         'New record does not provide all values for unique key (' .
2800                                                         implode( ', ', $indexColumns ) . ')'
2801                                                 );
2802                                         } elseif ( in_array( null, $indexRowValues, true ) ) {
2803                                                 throw new DBUnexpectedError(
2804                                                         $this,
2805                                                         'New record has a null value for unique key (' .
2806                                                         implode( ', ', $indexColumns ) . ')'
2807                                                 );
2808                                         }
2809                                         $indexWhereClauses[] = $this->makeList( $indexRowValues, LIST_AND );
2810                                 }
2811
2812                                 if ( $indexWhereClauses ) {
2813                                         $this->delete( $table, $this->makeList( $indexWhereClauses, LIST_OR ), $fname );
2814                                         $affectedRowCount += $this->affectedRows();
2815                                 }
2816
2817                                 // Now insert the row
2818                                 $this->insert( $table, $row, $fname );
2819                                 $affectedRowCount += $this->affectedRows();
2820                         }
2821                         $this->endAtomic( $fname );
2822                         $this->affectedRowCount = $affectedRowCount;
2823                 } catch ( Exception $e ) {
2824                         $this->cancelAtomic( $fname );
2825                         throw $e;
2826                 }
2827         }
2828
2829         /**
2830          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2831          * statement.
2832          *
2833          * @param string $table Table name
2834          * @param array|string $rows Row(s) to insert
2835          * @param string $fname Caller function name
2836          *
2837          * @return ResultWrapper
2838          */
2839         protected function nativeReplace( $table, $rows, $fname ) {
2840                 $table = $this->tableName( $table );
2841
2842                 # Single row case
2843                 if ( !is_array( reset( $rows ) ) ) {
2844                         $rows = [ $rows ];
2845                 }
2846
2847                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2848                 $first = true;
2849
2850                 foreach ( $rows as $row ) {
2851                         if ( $first ) {
2852                                 $first = false;
2853                         } else {
2854                                 $sql .= ',';
2855                         }
2856
2857                         $sql .= '(' . $this->makeList( $row ) . ')';
2858                 }
2859
2860                 return $this->query( $sql, $fname );
2861         }
2862
2863         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2864                 $fname = __METHOD__
2865         ) {
2866                 if ( !count( $rows ) ) {
2867                         return true; // nothing to do
2868                 }
2869
2870                 if ( !is_array( reset( $rows ) ) ) {
2871                         $rows = [ $rows ];
2872                 }
2873
2874                 if ( count( $uniqueIndexes ) ) {
2875                         $clauses = []; // list WHERE clauses that each identify a single row
2876                         foreach ( $rows as $row ) {
2877                                 foreach ( $uniqueIndexes as $index ) {
2878                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2879                                         $rowKey = []; // unique key to this row
2880                                         foreach ( $index as $column ) {
2881                                                 $rowKey[$column] = $row[$column];
2882                                         }
2883                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2884                                 }
2885                         }
2886                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2887                 } else {
2888                         $where = false;
2889                 }
2890
2891                 $affectedRowCount = 0;
2892                 try {
2893                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2894                         # Update any existing conflicting row(s)
2895                         if ( $where !== false ) {
2896                                 $ok = $this->update( $table, $set, $where, $fname );
2897                                 $affectedRowCount += $this->affectedRows();
2898                         } else {
2899                                 $ok = true;
2900                         }
2901                         # Now insert any non-conflicting row(s)
2902                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2903                         $affectedRowCount += $this->affectedRows();
2904                         $this->endAtomic( $fname );
2905                         $this->affectedRowCount = $affectedRowCount;
2906                 } catch ( Exception $e ) {
2907                         $this->cancelAtomic( $fname );
2908                         throw $e;
2909                 }
2910
2911                 return $ok;
2912         }
2913
2914         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2915                 $fname = __METHOD__
2916         ) {
2917                 if ( !$conds ) {
2918                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2919                 }
2920
2921                 $delTable = $this->tableName( $delTable );
2922                 $joinTable = $this->tableName( $joinTable );
2923                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2924                 if ( $conds != '*' ) {
2925                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2926                 }
2927                 $sql .= ')';
2928
2929                 $this->query( $sql, $fname );
2930         }
2931
2932         public function textFieldSize( $table, $field ) {
2933                 $table = $this->tableName( $table );
2934                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2935                 $res = $this->query( $sql, __METHOD__ );
2936                 $row = $this->fetchObject( $res );
2937
2938                 $m = [];
2939
2940                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2941                         $size = $m[1];
2942                 } else {
2943                         $size = -1;
2944                 }
2945
2946                 return $size;
2947         }
2948
2949         public function delete( $table, $conds, $fname = __METHOD__ ) {
2950                 if ( !$conds ) {
2951                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2952                 }
2953
2954                 $table = $this->tableName( $table );
2955                 $sql = "DELETE FROM $table";
2956
2957                 if ( $conds != '*' ) {
2958                         if ( is_array( $conds ) ) {
2959                                 $conds = $this->makeList( $conds, self::LIST_AND );
2960                         }
2961                         $sql .= ' WHERE ' . $conds;
2962                 }
2963
2964                 return $this->query( $sql, $fname );
2965         }
2966
2967         final public function insertSelect(
2968                 $destTable, $srcTable, $varMap, $conds,
2969                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2970         ) {
2971                 static $hints = [ 'NO_AUTO_COLUMNS' ];
2972
2973                 $insertOptions = (array)$insertOptions;
2974                 $selectOptions = (array)$selectOptions;
2975
2976                 if ( $this->cliMode && $this->isInsertSelectSafe( $insertOptions, $selectOptions ) ) {
2977                         // For massive migrations with downtime, we don't want to select everything
2978                         // into memory and OOM, so do all this native on the server side if possible.
2979                         return $this->nativeInsertSelect(
2980                                 $destTable,
2981                                 $srcTable,
2982                                 $varMap,
2983                                 $conds,
2984                                 $fname,
2985                                 array_diff( $insertOptions, $hints ),
2986                                 $selectOptions,
2987                                 $selectJoinConds
2988                         );
2989                 }
2990
2991                 return $this->nonNativeInsertSelect(
2992                         $destTable,
2993                         $srcTable,
2994                         $varMap,
2995                         $conds,
2996                         $fname,
2997                         array_diff( $insertOptions, $hints ),
2998                         $selectOptions,
2999                         $selectJoinConds
3000                 );
3001         }
3002
3003         /**
3004          * @param array $insertOptions INSERT options
3005          * @param array $selectOptions SELECT options
3006          * @return bool Whether an INSERT SELECT with these options will be replication safe
3007          * @since 1.31
3008          */
3009         protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
3010                 return true;
3011         }
3012
3013         /**
3014          * Implementation of insertSelect() based on select() and insert()
3015          *
3016          * @see IDatabase::insertSelect()
3017          * @since 1.30
3018          * @param string $destTable
3019          * @param string|array $srcTable
3020          * @param array $varMap
3021          * @param array $conds
3022          * @param string $fname
3023          * @param array $insertOptions
3024          * @param array $selectOptions
3025          * @param array $selectJoinConds
3026          * @return bool
3027          */
3028         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
3029                 $fname = __METHOD__,
3030                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
3031         ) {
3032                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
3033                 // on only the master (without needing row-based-replication). It also makes it easy to
3034                 // know how big the INSERT is going to be.
3035                 $fields = [];
3036                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
3037                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
3038                 }
3039                 $selectOptions[] = 'FOR UPDATE';
3040                 $res = $this->select(
3041                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
3042                 );
3043                 if ( !$res ) {
3044                         return false;
3045                 }
3046
3047                 try {
3048                         $affectedRowCount = 0;
3049                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
3050                         $rows = [];
3051                         $ok = true;
3052                         foreach ( $res as $row ) {
3053                                 $rows[] = (array)$row;
3054
3055                                 // Avoid inserts that are too huge
3056                                 if ( count( $rows ) >= $this->nonNativeInsertSelectBatchSize ) {
3057                                         $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
3058                                         if ( !$ok ) {
3059                                                 break;
3060                                         }
3061                                         $affectedRowCount += $this->affectedRows();
3062                                         $rows = [];
3063                                 }
3064                         }
3065                         if ( $rows && $ok ) {
3066                                 $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
3067                                 if ( $ok ) {
3068                                         $affectedRowCount += $this->affectedRows();
3069                                 }
3070                         }
3071                         if ( $ok ) {
3072                                 $this->endAtomic( $fname );
3073                                 $this->affectedRowCount = $affectedRowCount;
3074                         } else {
3075                                 $this->cancelAtomic( $fname );
3076                         }
3077                         return $ok;
3078                 } catch ( Exception $e ) {
3079                         $this->cancelAtomic( $fname );
3080                         throw $e;
3081                 }
3082         }
3083
3084         /**
3085          * Native server-side implementation of insertSelect() for situations where
3086          * we don't want to select everything into memory
3087          *
3088          * @see IDatabase::insertSelect()
3089          * @param string $destTable
3090          * @param string|array $srcTable
3091          * @param array $varMap
3092          * @param array $conds
3093          * @param string $fname
3094          * @param array $insertOptions
3095          * @param array $selectOptions
3096          * @param array $selectJoinConds
3097          * @return bool
3098          */
3099         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
3100                 $fname = __METHOD__,
3101                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
3102         ) {
3103                 $destTable = $this->tableName( $destTable );
3104
3105                 if ( !is_array( $insertOptions ) ) {
3106                         $insertOptions = [ $insertOptions ];
3107                 }
3108
3109                 $insertOptions = $this->makeInsertOptions( $insertOptions );
3110
3111                 $selectSql = $this->selectSQLText(
3112                         $srcTable,
3113                         array_values( $varMap ),
3114                         $conds,
3115                         $fname,
3116                         $selectOptions,
3117                         $selectJoinConds
3118                 );
3119
3120                 $sql = "INSERT $insertOptions" .
3121                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
3122                         $selectSql;
3123
3124                 return $this->query( $sql, $fname );
3125         }
3126
3127         /**
3128          * Construct a LIMIT query with optional offset. This is used for query
3129          * pages. The SQL should be adjusted so that only the first $limit rows
3130          * are returned. If $offset is provided as well, then the first $offset
3131          * rows should be discarded, and the next $limit rows should be returned.
3132          * If the result of the query is not ordered, then the rows to be returned
3133          * are theoretically arbitrary.
3134          *
3135          * $sql is expected to be a SELECT, if that makes a difference.
3136          *
3137          * The version provided by default works in MySQL and SQLite. It will very
3138          * likely need to be overridden for most other DBMSes.
3139          *
3140          * @param string $sql SQL query we will append the limit too
3141          * @param int $limit The SQL limit
3142          * @param int|bool $offset The SQL offset (default false)
3143          * @throws DBUnexpectedError
3144          * @return string
3145          */
3146         public function limitResult( $sql, $limit, $offset = false ) {
3147                 if ( !is_numeric( $limit ) ) {
3148                         throw new DBUnexpectedError( $this,
3149                                 "Invalid non-numeric limit passed to limitResult()\n" );
3150                 }
3151
3152                 return "$sql LIMIT "
3153                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
3154                 . "{$limit} ";
3155         }
3156
3157         public function unionSupportsOrderAndLimit() {
3158                 return true; // True for almost every DB supported
3159         }
3160
3161         public function unionQueries( $sqls, $all ) {
3162                 $glue = $all ? ') UNION ALL (' : ') UNION (';
3163
3164                 return '(' . implode( $glue, $sqls ) . ')';
3165         }
3166
3167         public function unionConditionPermutations(
3168                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
3169                 $options = [], $join_conds = []
3170         ) {
3171                 // First, build the Cartesian product of $permute_conds
3172                 $conds = [ [] ];
3173                 foreach ( $permute_conds as $field => $values ) {
3174                         if ( !$values ) {
3175                                 // Skip empty $values
3176                                 continue;
3177                         }
3178                         $values = array_unique( $values ); // For sanity
3179                         $newConds = [];
3180                         foreach ( $conds as $cond ) {
3181                                 foreach ( $values as $value ) {
3182                                         $cond[$field] = $value;
3183                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
3184                                 }
3185                         }
3186                         $conds = $newConds;
3187                 }
3188
3189                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
3190
3191                 // If there's just one condition and no subordering, hand off to
3192                 // selectSQLText directly.
3193                 if ( count( $conds ) === 1 &&
3194                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
3195                 ) {
3196                         return $this->selectSQLText(
3197                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
3198                         );
3199                 }
3200
3201                 // Otherwise, we need to pull out the order and limit to apply after
3202                 // the union. Then build the SQL queries for each set of conditions in
3203                 // $conds. Then union them together (using UNION ALL, because the
3204                 // product *should* already be distinct).
3205                 $orderBy = $this->makeOrderBy( $options );
3206                 $limit = $options['LIMIT'] ?? null;
3207                 $offset = $options['OFFSET'] ?? false;
3208                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
3209                 if ( !$this->unionSupportsOrderAndLimit() ) {
3210                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
3211                 } else {
3212                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
3213                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
3214                         }
3215                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
3216                                 // We need to increase the limit by the offset rather than
3217                                 // using the offset directly, otherwise it'll skip incorrectly
3218                                 // in the subqueries.
3219                                 $options['LIMIT'] = $limit + $offset;
3220                                 unset( $options['OFFSET'] );
3221                         }
3222                 }
3223
3224                 $sqls = [];
3225                 foreach ( $conds as $cond ) {
3226                         $sqls[] = $this->selectSQLText(
3227                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
3228                         );
3229                 }
3230                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
3231                 if ( $limit !== null ) {
3232                         $sql = $this->limitResult( $sql, $limit, $offset );
3233                 }
3234
3235                 return $sql;
3236         }
3237
3238         public function conditional( $cond, $trueVal, $falseVal ) {
3239                 if ( is_array( $cond ) ) {
3240                         $cond = $this->makeList( $cond, self::LIST_AND );
3241                 }
3242
3243                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
3244         }
3245
3246         public function strreplace( $orig, $old, $new ) {
3247                 return "REPLACE({$orig}, {$old}, {$new})";
3248         }
3249
3250         public function getServerUptime() {
3251                 return 0;
3252         }
3253
3254         public function wasDeadlock() {
3255                 return false;
3256         }
3257
3258         public function wasLockTimeout() {
3259                 return false;
3260         }
3261
3262         public function wasConnectionLoss() {
3263                 return $this->wasConnectionError( $this->lastErrno() );
3264         }
3265
3266         public function wasReadOnlyError() {
3267                 return false;
3268         }
3269
3270         public function wasErrorReissuable() {
3271                 return (
3272                         $this->wasDeadlock() ||
3273                         $this->wasLockTimeout() ||
3274                         $this->wasConnectionLoss()
3275                 );
3276         }
3277
3278         /**
3279          * Do not use this method outside of Database/DBError classes
3280          *
3281          * @param int|string $errno
3282          * @return bool Whether the given query error was a connection drop
3283          */
3284         public function wasConnectionError( $errno ) {
3285                 return false;
3286         }
3287
3288         /**
3289          * @return bool Whether it is safe to assume the given error only caused statement rollback
3290          * @note This is for backwards compatibility for callers catching DBError exceptions in
3291          *   order to ignore problems like duplicate key errors or foriegn key violations
3292          * @since 1.31
3293          */
3294         protected function wasKnownStatementRollbackError() {
3295                 return false; // don't know; it could have caused a transaction rollback
3296         }
3297
3298         public function deadlockLoop() {
3299                 $args = func_get_args();
3300                 $function = array_shift( $args );
3301                 $tries = self::DEADLOCK_TRIES;
3302
3303                 $this->begin( __METHOD__ );
3304
3305                 $retVal = null;
3306                 /** @var Exception $e */
3307                 $e = null;
3308                 do {
3309                         try {
3310                                 $retVal = $function( ...$args );
3311                                 break;
3312                         } catch ( DBQueryError $e ) {
3313                                 if ( $this->wasDeadlock() ) {
3314                                         // Retry after a randomized delay
3315                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3316                                 } else {
3317                                         // Throw the error back up
3318                                         throw $e;
3319                                 }
3320                         }
3321                 } while ( --$tries > 0 );
3322
3323                 if ( $tries <= 0 ) {
3324                         // Too many deadlocks; give up
3325                         $this->rollback( __METHOD__ );
3326                         throw $e;
3327                 } else {
3328                         $this->commit( __METHOD__ );
3329
3330                         return $retVal;
3331                 }
3332         }
3333
3334         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3335                 # Real waits are implemented in the subclass.
3336                 return 0;
3337         }
3338
3339         public function getReplicaPos() {
3340                 # Stub
3341                 return false;
3342         }
3343
3344         public function getMasterPos() {
3345                 # Stub
3346                 return false;
3347         }
3348
3349         public function serverIsReadOnly() {
3350                 return false;
3351         }
3352
3353         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
3354                 if ( !$this->trxLevel ) {
3355                         throw new DBUnexpectedError( $this, "No transaction is active." );
3356                 }
3357                 $this->trxEndCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3358         }
3359
3360         final public function onTransactionCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
3361                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3362                         // Start an implicit transaction similar to how query() does
3363                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3364                         $this->trxAutomatic = true;
3365                 }
3366
3367                 $this->trxIdleCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3368                 if ( !$this->trxLevel ) {
3369                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
3370                 }
3371         }
3372
3373         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
3374                 $this->onTransactionCommitOrIdle( $callback, $fname );
3375         }
3376
3377         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
3378                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3379                         // Start an implicit transaction similar to how query() does
3380                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3381                         $this->trxAutomatic = true;
3382                 }
3383
3384                 if ( $this->trxLevel ) {
3385                         $this->trxPreCommitCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3386                 } else {
3387                         // No transaction is active nor will start implicitly, so make one for this callback
3388                         $this->startAtomic( __METHOD__, self::ATOMIC_CANCELABLE );
3389                         try {
3390                                 $callback( $this );
3391                                 $this->endAtomic( __METHOD__ );
3392                         } catch ( Exception $e ) {
3393                                 $this->cancelAtomic( __METHOD__ );
3394                                 throw $e;
3395                         }
3396                 }
3397         }
3398
3399         /**
3400          * @return AtomicSectionIdentifier|null ID of the topmost atomic section level
3401          */
3402         private function currentAtomicSectionId() {
3403                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3404                         $levelInfo = end( $this->trxAtomicLevels );
3405
3406                         return $levelInfo[1];
3407                 }
3408
3409                 return null;
3410         }
3411
3412         /**
3413          * @param AtomicSectionIdentifier $old
3414          * @param AtomicSectionIdentifier $new
3415          */
3416         private function reassignCallbacksForSection(
3417                 AtomicSectionIdentifier $old, AtomicSectionIdentifier $new
3418         ) {
3419                 foreach ( $this->trxPreCommitCallbacks as $key => $info ) {
3420                         if ( $info[2] === $old ) {
3421                                 $this->trxPreCommitCallbacks[$key][2] = $new;
3422                         }
3423                 }
3424                 foreach ( $this->trxIdleCallbacks as $key => $info ) {
3425                         if ( $info[2] === $old ) {
3426                                 $this->trxIdleCallbacks[$key][2] = $new;
3427                         }
3428                 }
3429                 foreach ( $this->trxEndCallbacks as $key => $info ) {
3430                         if ( $info[2] === $old ) {
3431                                 $this->trxEndCallbacks[$key][2] = $new;
3432                         }
3433                 }
3434         }
3435
3436         /**
3437          * @param AtomicSectionIdentifier[] $sectionIds ID of an actual savepoint
3438          * @throws UnexpectedValueException
3439          */
3440         private function modifyCallbacksForCancel( array $sectionIds ) {
3441                 // Cancel the "on commit" callbacks owned by this savepoint
3442                 $this->trxIdleCallbacks = array_filter(
3443                         $this->trxIdleCallbacks,
3444                         function ( $entry ) use ( $sectionIds ) {
3445                                 return !in_array( $entry[2], $sectionIds, true );
3446                         }
3447                 );
3448                 $this->trxPreCommitCallbacks = array_filter(
3449                         $this->trxPreCommitCallbacks,
3450                         function ( $entry ) use ( $sectionIds ) {
3451                                 return !in_array( $entry[2], $sectionIds, true );
3452                         }
3453                 );
3454                 // Make "on resolution" callbacks owned by this savepoint to perceive a rollback
3455                 foreach ( $this->trxEndCallbacks as $key => $entry ) {
3456                         if ( in_array( $entry[2], $sectionIds, true ) ) {
3457                                 $callback = $entry[0];
3458                                 $this->trxEndCallbacks[$key][0] = function () use ( $callback ) {
3459                                         return $callback( self::TRIGGER_ROLLBACK, $this );
3460                                 };
3461                         }
3462                 }
3463         }
3464
3465         final public function setTransactionListener( $name, callable $callback = null ) {
3466                 if ( $callback ) {
3467                         $this->trxRecurringCallbacks[$name] = $callback;
3468                 } else {
3469                         unset( $this->trxRecurringCallbacks[$name] );
3470                 }
3471         }
3472
3473         /**
3474          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
3475          *
3476          * This method should not be used outside of Database/LoadBalancer
3477          *
3478          * @param bool $suppress
3479          * @since 1.28
3480          */
3481         final public function setTrxEndCallbackSuppression( $suppress ) {
3482                 $this->trxEndCallbacksSuppressed = $suppress;
3483         }
3484
3485         /**
3486          * Actually consume and run any "on transaction idle/resolution" callbacks.
3487          *
3488          * This method should not be used outside of Database/LoadBalancer
3489          *
3490          * @param int $trigger IDatabase::TRIGGER_* constant
3491          * @return int Number of callbacks attempted
3492          * @since 1.20
3493          * @throws Exception
3494          */
3495         public function runOnTransactionIdleCallbacks( $trigger ) {
3496                 if ( $this->trxLevel ) { // sanity
3497                         throw new DBUnexpectedError( $this, __METHOD__ . ': a transaction is still open.' );
3498                 }
3499
3500                 if ( $this->trxEndCallbacksSuppressed ) {
3501                         return 0;
3502                 }
3503
3504                 $count = 0;
3505                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
3506                 /** @var Exception $e */
3507                 $e = null; // first exception
3508                 do { // callbacks may add callbacks :)
3509                         $callbacks = array_merge(
3510                                 $this->trxIdleCallbacks,
3511                                 $this->trxEndCallbacks // include "transaction resolution" callbacks
3512                         );
3513                         $this->trxIdleCallbacks = []; // consumed (and recursion guard)
3514                         $this->trxEndCallbacks = []; // consumed (recursion guard)
3515                         foreach ( $callbacks as $callback ) {
3516                                 ++$count;
3517                                 list( $phpCallback ) = $callback;
3518                                 $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
3519                                 try {
3520                                         call_user_func( $phpCallback, $trigger, $this );
3521                                 } catch ( Exception $ex ) {
3522                                         call_user_func( $this->errorLogger, $ex );
3523                                         $e = $e ?: $ex;
3524                                         // Some callbacks may use startAtomic/endAtomic, so make sure
3525                                         // their transactions are ended so other callbacks don't fail
3526                                         if ( $this->trxLevel() ) {
3527                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
3528                                         }
3529                                 } finally {
3530                                         if ( $autoTrx ) {
3531                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
3532                                         } else {
3533                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
3534                                         }
3535                                 }
3536                         }
3537                 } while ( count( $this->trxIdleCallbacks ) );
3538
3539                 if ( $e instanceof Exception ) {
3540                         throw $e; // re-throw any first exception
3541                 }
3542
3543                 return $count;
3544         }
3545
3546         /**
3547          * Actually consume and run any "on transaction pre-commit" callbacks.
3548          *
3549          * This method should not be used outside of Database/LoadBalancer
3550          *
3551          * @since 1.22
3552          * @return int Number of callbacks attempted
3553          * @throws Exception
3554          */
3555         public function runOnTransactionPreCommitCallbacks() {
3556                 $count = 0;
3557
3558                 $e = null; // first exception
3559                 do { // callbacks may add callbacks :)
3560                         $callbacks = $this->trxPreCommitCallbacks;
3561                         $this->trxPreCommitCallbacks = []; // consumed (and recursion guard)
3562                         foreach ( $callbacks as $callback ) {
3563                                 try {
3564                                         ++$count;
3565                                         list( $phpCallback ) = $callback;
3566                                         $phpCallback( $this );
3567                                 } catch ( Exception $ex ) {
3568                                         ( $this->errorLogger )( $ex );
3569                                         $e = $e ?: $ex;
3570                                 }
3571                         }
3572                 } while ( count( $this->trxPreCommitCallbacks ) );
3573
3574                 if ( $e instanceof Exception ) {
3575                         throw $e; // re-throw any first exception
3576                 }
3577
3578                 return $count;
3579         }
3580
3581         /**
3582          * Actually run any "transaction listener" callbacks.
3583          *
3584          * This method should not be used outside of Database/LoadBalancer
3585          *
3586          * @param int $trigger IDatabase::TRIGGER_* constant
3587          * @throws Exception
3588          * @since 1.20
3589          */
3590         public function runTransactionListenerCallbacks( $trigger ) {
3591                 if ( $this->trxEndCallbacksSuppressed ) {
3592                         return;
3593                 }
3594
3595                 /** @var Exception $e */
3596                 $e = null; // first exception
3597
3598                 foreach ( $this->trxRecurringCallbacks as $phpCallback ) {
3599                         try {
3600                                 $phpCallback( $trigger, $this );
3601                         } catch ( Exception $ex ) {
3602                                 ( $this->errorLogger )( $ex );
3603                                 $e = $e ?: $ex;
3604                         }
3605                 }
3606
3607                 if ( $e instanceof Exception ) {
3608                         throw $e; // re-throw any first exception
3609                 }
3610         }
3611
3612         /**
3613          * Create a savepoint
3614          *
3615          * This is used internally to implement atomic sections. It should not be
3616          * used otherwise.
3617          *
3618          * @since 1.31
3619          * @param string $identifier Identifier for the savepoint
3620          * @param string $fname Calling function name
3621          */
3622         protected function doSavepoint( $identifier, $fname ) {
3623                 $this->query( 'SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3624         }
3625
3626         /**
3627          * Release a savepoint
3628          *
3629          * This is used internally to implement atomic sections. It should not be
3630          * used otherwise.
3631          *
3632          * @since 1.31
3633          * @param string $identifier Identifier for the savepoint
3634          * @param string $fname Calling function name
3635          */
3636         protected function doReleaseSavepoint( $identifier, $fname ) {
3637                 $this->query( 'RELEASE SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3638         }
3639
3640         /**
3641          * Rollback to a savepoint
3642          *
3643          * This is used internally to implement atomic sections. It should not be
3644          * used otherwise.
3645          *
3646          * @since 1.31
3647          * @param string $identifier Identifier for the savepoint
3648          * @param string $fname Calling function name
3649          */
3650         protected function doRollbackToSavepoint( $identifier, $fname ) {
3651                 $this->query( 'ROLLBACK TO SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3652         }
3653
3654         /**
3655          * @param string $fname
3656          * @return string
3657          */
3658         private function nextSavepointId( $fname ) {
3659                 $savepointId = self::$SAVEPOINT_PREFIX . ++$this->trxAtomicCounter;
3660                 if ( strlen( $savepointId ) > 30 ) {
3661                         // 30 == Oracle's identifier length limit (pre 12c)
3662                         // With a 22 character prefix, that puts the highest number at 99999999.
3663                         throw new DBUnexpectedError(
3664                                 $this,
3665                                 'There have been an excessively large number of atomic sections in a transaction'
3666                                 . " started by $this->trxFname (at $fname)"
3667                         );
3668                 }
3669
3670                 return $savepointId;
3671         }
3672
3673         final public function startAtomic(
3674                 $fname = __METHOD__, $cancelable = self::ATOMIC_NOT_CANCELABLE
3675         ) {
3676                 $savepointId = $cancelable === self::ATOMIC_CANCELABLE ? self::$NOT_APPLICABLE : null;
3677
3678                 if ( !$this->trxLevel ) {
3679                         $this->begin( $fname, self::TRANSACTION_INTERNAL ); // sets trxAutomatic
3680                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
3681                         // in all changes being in one transaction to keep requests transactional.
3682                         if ( $this->getFlag( self::DBO_TRX ) ) {
3683                                 // Since writes could happen in between the topmost atomic sections as part
3684                                 // of the transaction, those sections will need savepoints.
3685                                 $savepointId = $this->nextSavepointId( $fname );
3686                                 $this->doSavepoint( $savepointId, $fname );
3687                         } else {
3688                                 $this->trxAutomaticAtomic = true;
3689                         }
3690                 } elseif ( $cancelable === self::ATOMIC_CANCELABLE ) {
3691                         $savepointId = $this->nextSavepointId( $fname );
3692                         $this->doSavepoint( $savepointId, $fname );
3693                 }
3694
3695                 $sectionId = new AtomicSectionIdentifier;
3696                 $this->trxAtomicLevels[] = [ $fname, $sectionId, $savepointId ];
3697                 $this->queryLogger->debug( 'startAtomic: entering level ' .
3698                         ( count( $this->trxAtomicLevels ) - 1 ) . " ($fname)" );
3699
3700                 return $sectionId;
3701         }
3702
3703         final public function endAtomic( $fname = __METHOD__ ) {
3704                 if ( !$this->trxLevel || !$this->trxAtomicLevels ) {
3705                         throw new DBUnexpectedError( $this, "No atomic section is open (got $fname)." );
3706                 }
3707
3708                 // Check if the current section matches $fname
3709                 $pos = count( $this->trxAtomicLevels ) - 1;
3710                 list( $savedFname, $sectionId, $savepointId ) = $this->trxAtomicLevels[$pos];
3711                 $this->queryLogger->debug( "endAtomic: leaving level $pos ($fname)" );
3712
3713                 if ( $savedFname !== $fname ) {
3714                         throw new DBUnexpectedError(
3715                                 $this,
3716                                 "Invalid atomic section ended (got $fname but expected $savedFname)."
3717                         );
3718                 }
3719
3720                 // Remove the last section (no need to re-index the array)
3721                 array_pop( $this->trxAtomicLevels );
3722
3723                 if ( !$this->trxAtomicLevels && $this->trxAutomaticAtomic ) {
3724                         $this->commit( $fname, self::FLUSHING_INTERNAL );
3725                 } elseif ( $savepointId !== null && $savepointId !== self::$NOT_APPLICABLE ) {
3726                         $this->doReleaseSavepoint( $savepointId, $fname );
3727                 }
3728
3729                 // Hoist callback ownership for callbacks in the section that just ended;
3730                 // all callbacks should have an owner that is present in trxAtomicLevels.
3731                 $currentSectionId = $this->currentAtomicSectionId();
3732                 if ( $currentSectionId ) {
3733                         $this->reassignCallbacksForSection( $sectionId, $currentSectionId );
3734                 }
3735         }
3736
3737         final public function cancelAtomic(
3738                 $fname = __METHOD__, AtomicSectionIdentifier $sectionId = null
3739         ) {
3740                 if ( !$this->trxLevel || !$this->trxAtomicLevels ) {
3741                         throw new DBUnexpectedError( $this, "No atomic section is open (got $fname)." );
3742                 }
3743
3744                 $excisedFnames = [];
3745                 if ( $sectionId !== null ) {
3746                         // Find the (last) section with the given $sectionId
3747                         $pos = -1;
3748                         foreach ( $this->trxAtomicLevels as $i => list( $asFname, $asId, $spId ) ) {
3749                                 if ( $asId === $sectionId ) {
3750                                         $pos = $i;
3751                                 }
3752                         }
3753                         if ( $pos < 0 ) {
3754                                 throw new DBUnexpectedError( "Atomic section not found (for $fname)" );
3755                         }
3756                         // Remove all descendant sections and re-index the array
3757                         $excisedIds = [];
3758                         $len = count( $this->trxAtomicLevels );
3759                         for ( $i = $pos + 1; $i < $len; ++$i ) {
3760                                 $excisedFnames[] = $this->trxAtomicLevels[$i][0];
3761                                 $excisedIds[] = $this->trxAtomicLevels[$i][1];
3762                         }
3763                         $this->trxAtomicLevels = array_slice( $this->trxAtomicLevels, 0, $pos + 1 );
3764                         $this->modifyCallbacksForCancel( $excisedIds );
3765                 }
3766
3767                 // Check if the current section matches $fname
3768                 $pos = count( $this->trxAtomicLevels ) - 1;
3769                 list( $savedFname, $savedSectionId, $savepointId ) = $this->trxAtomicLevels[$pos];
3770
3771                 if ( $excisedFnames ) {
3772                         $this->queryLogger->debug( "cancelAtomic: canceling level $pos ($savedFname) " .
3773                                 "and descendants " . implode( ', ', $excisedFnames ) );
3774                 } else {
3775                         $this->queryLogger->debug( "cancelAtomic: canceling level $pos ($savedFname)" );
3776                 }
3777
3778                 if ( $savedFname !== $fname ) {
3779                         throw new DBUnexpectedError(
3780                                 $this,
3781                                 "Invalid atomic section ended (got $fname but expected $savedFname)."
3782                         );
3783                 }
3784
3785                 // Remove the last section (no need to re-index the array)
3786                 array_pop( $this->trxAtomicLevels );
3787                 $this->modifyCallbacksForCancel( [ $savedSectionId ] );
3788
3789                 if ( $savepointId !== null ) {
3790                         // Rollback the transaction to the state just before this atomic section
3791                         if ( $savepointId === self::$NOT_APPLICABLE ) {
3792                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
3793                         } else {
3794                                 $this->doRollbackToSavepoint( $savepointId, $fname );
3795                                 $this->trxStatus = self::STATUS_TRX_OK; // no exception; recovered
3796                                 $this->trxStatusIgnoredCause = null;
3797                         }
3798                 } elseif ( $this->trxStatus > self::STATUS_TRX_ERROR ) {
3799                         // Put the transaction into an error state if it's not already in one
3800                         $this->trxStatus = self::STATUS_TRX_ERROR;
3801                         $this->trxStatusCause = new DBUnexpectedError(
3802                                 $this,
3803                                 "Uncancelable atomic section canceled (got $fname)."
3804                         );
3805                 }
3806
3807                 $this->affectedRowCount = 0; // for the sake of consistency
3808         }
3809
3810         final public function doAtomicSection(
3811                 $fname, callable $callback, $cancelable = self::ATOMIC_NOT_CANCELABLE
3812         ) {
3813                 $sectionId = $this->startAtomic( $fname, $cancelable );
3814                 try {
3815                         $res = $callback( $this, $fname );
3816                 } catch ( Exception $e ) {
3817                         $this->cancelAtomic( $fname, $sectionId );
3818
3819                         throw $e;
3820                 }
3821                 $this->endAtomic( $fname );
3822
3823                 return $res;
3824         }
3825
3826         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
3827                 static $modes = [ self::TRANSACTION_EXPLICIT, self::TRANSACTION_INTERNAL ];
3828                 if ( !in_array( $mode, $modes, true ) ) {
3829                         throw new DBUnexpectedError( $this, "$fname: invalid mode parameter '$mode'." );
3830                 }
3831
3832                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
3833                 if ( $this->trxLevel ) {
3834                         if ( $this->trxAtomicLevels ) {
3835                                 $levels = $this->flatAtomicSectionList();
3836                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
3837                                 throw new DBUnexpectedError( $this, $msg );
3838                         } elseif ( !$this->trxAutomatic ) {
3839                                 $msg = "$fname: Explicit transaction already active (from {$this->trxFname}).";
3840                                 throw new DBUnexpectedError( $this, $msg );
3841                         } else {
3842                                 $msg = "$fname: Implicit transaction already active (from {$this->trxFname}).";
3843                                 throw new DBUnexpectedError( $this, $msg );
3844                         }
3845                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
3846                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
3847                         throw new DBUnexpectedError( $this, $msg );
3848                 }
3849
3850                 // Avoid fatals if close() was called
3851                 $this->assertOpen();
3852
3853                 $this->doBegin( $fname );
3854                 $this->trxStatus = self::STATUS_TRX_OK;
3855                 $this->trxStatusIgnoredCause = null;
3856                 $this->trxAtomicCounter = 0;
3857                 $this->trxTimestamp = microtime( true );
3858                 $this->trxFname = $fname;
3859                 $this->trxDoneWrites = false;
3860                 $this->trxAutomaticAtomic = false;
3861                 $this->trxAtomicLevels = [];
3862                 $this->trxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
3863                 $this->trxWriteDuration = 0.0;
3864                 $this->trxWriteQueryCount = 0;
3865                 $this->trxWriteAffectedRows = 0;
3866                 $this->trxWriteAdjDuration = 0.0;
3867                 $this->trxWriteAdjQueryCount = 0;
3868                 $this->trxWriteCallers = [];
3869                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
3870                 // Get an estimate of the replication lag before any such queries.
3871                 $this->trxReplicaLag = null; // clear cached value first
3872                 $this->trxReplicaLag = $this->getApproximateLagStatus()['lag'];
3873                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
3874                 // caller will think its OK to muck around with the transaction just because startAtomic()
3875                 // has not yet completed (e.g. setting trxAtomicLevels).
3876                 $this->trxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
3877         }
3878
3879         /**
3880          * Issues the BEGIN command to the database server.
3881          *
3882          * @see Database::begin()
3883          * @param string $fname
3884          */
3885         protected function doBegin( $fname ) {
3886                 $this->query( 'BEGIN', $fname );
3887                 $this->trxLevel = 1;
3888         }
3889
3890         final public function commit( $fname = __METHOD__, $flush = self::FLUSHING_ONE ) {
3891                 static $modes = [ self::FLUSHING_ONE, self::FLUSHING_ALL_PEERS, self::FLUSHING_INTERNAL ];
3892                 if ( !in_array( $flush, $modes, true ) ) {
3893                         throw new DBUnexpectedError( $this, "$fname: invalid flush parameter '$flush'." );
3894                 }
3895
3896                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3897                         // There are still atomic sections open; this cannot be ignored
3898                         $levels = $this->flatAtomicSectionList();
3899                         throw new DBUnexpectedError(
3900                                 $this,
3901                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3902                         );
3903                 }
3904
3905                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3906                         if ( !$this->trxLevel ) {
3907                                 return; // nothing to do
3908                         } elseif ( !$this->trxAutomatic ) {
3909                                 throw new DBUnexpectedError(
3910                                         $this,
3911                                         "$fname: Flushing an explicit transaction, getting out of sync."
3912                                 );
3913                         }
3914                 } else {
3915                         if ( !$this->trxLevel ) {
3916                                 $this->queryLogger->error(
3917                                         "$fname: No transaction to commit, something got out of sync." );
3918                                 return; // nothing to do
3919                         } elseif ( $this->trxAutomatic ) {
3920                                 throw new DBUnexpectedError(
3921                                         $this,
3922                                         "$fname: Expected mass commit of all peer transactions (DBO_TRX set)."
3923                                 );
3924                         }
3925                 }
3926
3927                 // Avoid fatals if close() was called
3928                 $this->assertOpen();
3929
3930                 $this->runOnTransactionPreCommitCallbacks();
3931
3932                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3933                 $this->doCommit( $fname );
3934                 $this->trxStatus = self::STATUS_TRX_NONE;
3935
3936                 if ( $this->trxDoneWrites ) {
3937                         $this->lastWriteTime = microtime( true );
3938                         $this->trxProfiler->transactionWritingOut(
3939                                 $this->server,
3940                                 $this->getDomainID(),
3941                                 $this->trxShortId,
3942                                 $writeTime,
3943                                 $this->trxWriteAffectedRows
3944                         );
3945                 }
3946
3947                 // With FLUSHING_ALL_PEERS, callbacks will be explicitly run later
3948                 if ( $flush !== self::FLUSHING_ALL_PEERS ) {
3949                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3950                         $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3951                 }
3952         }
3953
3954         /**
3955          * Issues the COMMIT command to the database server.
3956          *
3957          * @see Database::commit()
3958          * @param string $fname
3959          */
3960         protected function doCommit( $fname ) {
3961                 if ( $this->trxLevel ) {
3962                         $this->query( 'COMMIT', $fname );
3963                         $this->trxLevel = 0;
3964                 }
3965         }
3966
3967         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3968                 $trxActive = $this->trxLevel;
3969
3970                 if ( $flush !== self::FLUSHING_INTERNAL && $flush !== self::FLUSHING_ALL_PEERS ) {
3971                         if ( $this->getFlag( self::DBO_TRX ) ) {
3972                                 throw new DBUnexpectedError(
3973                                         $this,
3974                                         "$fname: Expected mass rollback of all peer transactions (DBO_TRX set)."
3975                                 );
3976                         }
3977                 }
3978
3979                 if ( $trxActive ) {
3980                         // Avoid fatals if close() was called
3981                         $this->assertOpen();
3982
3983                         $this->doRollback( $fname );
3984                         $this->trxStatus = self::STATUS_TRX_NONE;
3985                         $this->trxAtomicLevels = [];
3986                         // Estimate the RTT via a query now that trxStatus is OK
3987                         $writeTime = $this->pingAndCalculateLastTrxApplyTime();
3988
3989                         if ( $this->trxDoneWrites ) {
3990                                 $this->trxProfiler->transactionWritingOut(
3991                                         $this->server,
3992                                         $this->getDomainID(),
3993                                         $this->trxShortId,
3994                                         $writeTime,
3995                                         $this->trxWriteAffectedRows
3996                                 );
3997                         }
3998                 }
3999
4000                 // Clear any commit-dependant callbacks. They might even be present
4001                 // only due to transaction rounds, with no SQL transaction being active
4002                 $this->trxIdleCallbacks = [];
4003                 $this->trxPreCommitCallbacks = [];
4004
4005                 // With FLUSHING_ALL_PEERS, callbacks will be explicitly run later
4006                 if ( $trxActive && $flush !== self::FLUSHING_ALL_PEERS ) {
4007                         try {
4008                                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
4009                         } catch ( Exception $e ) {
4010                                 // already logged; finish and let LoadBalancer move on during mass-rollback
4011                         }
4012                         try {
4013                                 $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
4014                         } catch ( Exception $e ) {
4015                                 // already logged; let LoadBalancer move on during mass-rollback
4016                         }
4017
4018                         $this->affectedRowCount = 0; // for the sake of consistency
4019                 }
4020         }
4021
4022         /**
4023          * Issues the ROLLBACK command to the database server.
4024          *
4025          * @see Database::rollback()
4026          * @param string $fname
4027          */
4028         protected function doRollback( $fname ) {
4029                 if ( $this->trxLevel ) {
4030                         # Disconnects cause rollback anyway, so ignore those errors
4031                         $ignoreErrors = true;
4032                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
4033                         $this->trxLevel = 0;
4034                 }
4035         }
4036
4037         public function flushSnapshot( $fname = __METHOD__ ) {
4038                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
4039                         // This only flushes transactions to clear snapshots, not to write data
4040                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
4041                         throw new DBUnexpectedError(
4042                                 $this,
4043                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
4044                         );
4045                 }
4046
4047                 $this->commit( $fname, self::FLUSHING_INTERNAL );
4048         }
4049
4050         public function explicitTrxActive() {
4051                 return $this->trxLevel && ( $this->trxAtomicLevels || !$this->trxAutomatic );
4052         }
4053
4054         public function duplicateTableStructure(
4055                 $oldName, $newName, $temporary = false, $fname = __METHOD__
4056         ) {
4057                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4058         }
4059
4060         public function listTables( $prefix = null, $fname = __METHOD__ ) {
4061                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4062         }
4063
4064         public function listViews( $prefix = null, $fname = __METHOD__ ) {
4065                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4066         }
4067
4068         public function timestamp( $ts = 0 ) {
4069                 $t = new ConvertibleTimestamp( $ts );
4070                 // Let errors bubble up to avoid putting garbage in the DB
4071                 return $t->getTimestamp( TS_MW );
4072         }
4073
4074         public function timestampOrNull( $ts = null ) {
4075                 if ( is_null( $ts ) ) {
4076                         return null;
4077                 } else {
4078                         return $this->timestamp( $ts );
4079                 }
4080         }
4081
4082         public function affectedRows() {
4083                 return ( $this->affectedRowCount === null )
4084                         ? $this->fetchAffectedRowCount() // default to driver value
4085                         : $this->affectedRowCount;
4086         }
4087
4088         /**
4089          * @return int Number of retrieved rows according to the driver
4090          */
4091         abstract protected function fetchAffectedRowCount();
4092
4093         /**
4094          * Take the result from a query, and wrap it in a ResultWrapper if
4095          * necessary. Boolean values are passed through as is, to indicate success
4096          * of write queries or failure.
4097          *
4098          * Once upon a time, Database::query() returned a bare MySQL result
4099          * resource, and it was necessary to call this function to convert it to
4100          * a wrapper. Nowadays, raw database objects are never exposed to external
4101          * callers, so this is unnecessary in external code.
4102          *
4103          * @param bool|ResultWrapper|resource $result
4104          * @return bool|ResultWrapper
4105          */
4106         protected function resultObject( $result ) {
4107                 if ( !$result ) {
4108                         return false;
4109                 } elseif ( $result instanceof ResultWrapper ) {
4110                         return $result;
4111                 } elseif ( $result === true ) {
4112                         // Successful write query
4113                         return $result;
4114                 } else {
4115                         return new ResultWrapper( $this, $result );
4116                 }
4117         }
4118
4119         public function ping( &$rtt = null ) {
4120                 // Avoid hitting the server if it was hit recently
4121                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
4122                         if ( !func_num_args() || $this->rttEstimate > 0 ) {
4123                                 $rtt = $this->rttEstimate;
4124                                 return true; // don't care about $rtt
4125                         }
4126                 }
4127
4128                 // This will reconnect if possible or return false if not
4129                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
4130                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
4131                 $this->restoreFlags( self::RESTORE_PRIOR );
4132
4133                 if ( $ok ) {
4134                         $rtt = $this->rttEstimate;
4135                 }
4136
4137                 return $ok;
4138         }
4139
4140         /**
4141          * Close any existing (dead) database connection and open a new connection
4142          *
4143          * @param string $fname
4144          * @return bool True if new connection is opened successfully, false if error
4145          */
4146         protected function replaceLostConnection( $fname ) {
4147                 $this->closeConnection();
4148                 $this->opened = false;
4149                 $this->conn = false;
4150                 try {
4151                         $this->open(
4152                                 $this->server,
4153                                 $this->user,
4154                                 $this->password,
4155                                 $this->getDBname(),
4156                                 $this->dbSchema(),
4157                                 $this->tablePrefix()
4158                         );
4159                         $this->lastPing = microtime( true );
4160                         $ok = true;
4161
4162                         $this->connLogger->warning(
4163                                 $fname . ': lost connection to {dbserver}; reconnected',
4164                                 [
4165                                         'dbserver' => $this->getServer(),
4166                                         'trace' => ( new RuntimeException() )->getTraceAsString()
4167                                 ]
4168                         );
4169                 } catch ( DBConnectionError $e ) {
4170                         $ok = false;
4171
4172                         $this->connLogger->error(
4173                                 $fname . ': lost connection to {dbserver} permanently',
4174                                 [ 'dbserver' => $this->getServer() ]
4175                         );
4176                 }
4177
4178                 $this->handleSessionLoss();
4179
4180                 return $ok;
4181         }
4182
4183         public function getSessionLagStatus() {
4184                 return $this->getRecordedTransactionLagStatus() ?: $this->getApproximateLagStatus();
4185         }
4186
4187         /**
4188          * Get the replica DB lag when the current transaction started
4189          *
4190          * This is useful when transactions might use snapshot isolation
4191          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
4192          * is this lag plus transaction duration. If they don't, it is still
4193          * safe to be pessimistic. This returns null if there is no transaction.
4194          *
4195          * This returns null if the lag status for this transaction was not yet recorded.
4196          *
4197          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
4198          * @since 1.27
4199          */
4200         final protected function getRecordedTransactionLagStatus() {
4201                 return ( $this->trxLevel && $this->trxReplicaLag !== null )
4202                         ? [ 'lag' => $this->trxReplicaLag, 'since' => $this->trxTimestamp() ]
4203                         : null;
4204         }
4205
4206         /**
4207          * Get a replica DB lag estimate for this server
4208          *
4209          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
4210          * @since 1.27
4211          */
4212         protected function getApproximateLagStatus() {
4213                 return [
4214                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
4215                         'since' => microtime( true )
4216                 ];
4217         }
4218
4219         /**
4220          * Merge the result of getSessionLagStatus() for several DBs
4221          * using the most pessimistic values to estimate the lag of
4222          * any data derived from them in combination
4223          *
4224          * This is information is useful for caching modules
4225          *
4226          * @see WANObjectCache::set()
4227          * @see WANObjectCache::getWithSetCallback()
4228          *
4229          * @param IDatabase $db1
4230          * @param IDatabase|null $db2 [optional]
4231          * @return array Map of values:
4232          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
4233          *   - since: oldest UNIX timestamp of any of the DB lag estimates
4234          *   - pending: whether any of the DBs have uncommitted changes
4235          * @throws DBError
4236          * @since 1.27
4237          */
4238         public static function getCacheSetOptions( IDatabase $db1, IDatabase $db2 = null ) {
4239                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
4240                 foreach ( func_get_args() as $db ) {
4241                         /** @var IDatabase $db */
4242                         $status = $db->getSessionLagStatus();
4243                         if ( $status['lag'] === false ) {
4244                                 $res['lag'] = false;
4245                         } elseif ( $res['lag'] !== false ) {
4246                                 $res['lag'] = max( $res['lag'], $status['lag'] );
4247                         }
4248                         $res['since'] = min( $res['since'], $status['since'] );
4249                         $res['pending'] = $res['pending'] ?: $db->writesPending();
4250                 }
4251
4252                 return $res;
4253         }
4254
4255         public function getLag() {
4256                 return 0;
4257         }
4258
4259         public function maxListLen() {
4260                 return 0;
4261         }
4262
4263         public function encodeBlob( $b ) {
4264                 return $b;
4265         }
4266
4267         public function decodeBlob( $b ) {
4268                 if ( $b instanceof Blob ) {
4269                         $b = $b->fetch();
4270                 }
4271                 return $b;
4272         }
4273
4274         public function setSessionOptions( array $options ) {
4275         }
4276
4277         public function sourceFile(
4278                 $filename,
4279                 callable $lineCallback = null,
4280                 callable $resultCallback = null,
4281                 $fname = false,
4282                 callable $inputCallback = null
4283         ) {
4284                 Wikimedia\suppressWarnings();
4285                 $fp = fopen( $filename, 'r' );
4286                 Wikimedia\restoreWarnings();
4287
4288                 if ( false === $fp ) {
4289                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
4290                 }
4291
4292                 if ( !$fname ) {
4293                         $fname = __METHOD__ . "( $filename )";
4294                 }
4295
4296                 try {
4297                         $error = $this->sourceStream(
4298                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
4299                 } catch ( Exception $e ) {
4300                         fclose( $fp );
4301                         throw $e;
4302                 }
4303
4304                 fclose( $fp );
4305
4306                 return $error;
4307         }
4308
4309         public function setSchemaVars( $vars ) {
4310                 $this->schemaVars = $vars;
4311         }
4312
4313         public function sourceStream(
4314                 $fp,
4315                 callable $lineCallback = null,
4316                 callable $resultCallback = null,
4317                 $fname = __METHOD__,
4318                 callable $inputCallback = null
4319         ) {
4320                 $delimiterReset = new ScopedCallback(
4321                         function ( $delimiter ) {
4322                                 $this->delimiter = $delimiter;
4323                         },
4324                         [ $this->delimiter ]
4325                 );
4326                 $cmd = '';
4327
4328                 while ( !feof( $fp ) ) {
4329                         if ( $lineCallback ) {
4330                                 call_user_func( $lineCallback );
4331                         }
4332
4333                         $line = trim( fgets( $fp ) );
4334
4335                         if ( $line == '' ) {
4336                                 continue;
4337                         }
4338
4339                         if ( '-' == $line[0] && '-' == $line[1] ) {
4340                                 continue;
4341                         }
4342
4343                         if ( $cmd != '' ) {
4344                                 $cmd .= ' ';
4345                         }
4346
4347                         $done = $this->streamStatementEnd( $cmd, $line );
4348
4349                         $cmd .= "$line\n";
4350
4351                         if ( $done || feof( $fp ) ) {
4352                                 $cmd = $this->replaceVars( $cmd );
4353
4354                                 if ( $inputCallback ) {
4355                                         $callbackResult = $inputCallback( $cmd );
4356
4357                                         if ( is_string( $callbackResult ) || !$callbackResult ) {
4358                                                 $cmd = $callbackResult;
4359                                         }
4360                                 }
4361
4362                                 if ( $cmd ) {
4363                                         $res = $this->query( $cmd, $fname );
4364
4365                                         if ( $resultCallback ) {
4366                                                 $resultCallback( $res, $this );
4367                                         }
4368
4369                                         if ( false === $res ) {
4370                                                 $err = $this->lastError();
4371
4372                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
4373                                         }
4374                                 }
4375                                 $cmd = '';
4376                         }
4377                 }
4378
4379                 ScopedCallback::consume( $delimiterReset );
4380                 return true;
4381         }
4382
4383         /**
4384          * Called by sourceStream() to check if we've reached a statement end
4385          *
4386          * @param string &$sql SQL assembled so far
4387          * @param string &$newLine New line about to be added to $sql
4388          * @return bool Whether $newLine contains end of the statement
4389          */
4390         public function streamStatementEnd( &$sql, &$newLine ) {
4391                 if ( $this->delimiter ) {
4392                         $prev = $newLine;
4393                         $newLine = preg_replace(
4394                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
4395                         if ( $newLine != $prev ) {
4396                                 return true;
4397                         }
4398                 }
4399
4400                 return false;
4401         }
4402
4403         /**
4404          * Database independent variable replacement. Replaces a set of variables
4405          * in an SQL statement with their contents as given by $this->getSchemaVars().
4406          *
4407          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
4408          *
4409          * - '{$var}' should be used for text and is passed through the database's
4410          *   addQuotes method.
4411          * - `{$var}` should be used for identifiers (e.g. table and database names).
4412          *   It is passed through the database's addIdentifierQuotes method which
4413          *   can be overridden if the database uses something other than backticks.
4414          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
4415          *   database's tableName method.
4416          * - / *i* / passes the name that follows through the database's indexName method.
4417          * - In all other cases, / *$var* / is left unencoded. Except for table options,
4418          *   its use should be avoided. In 1.24 and older, string encoding was applied.
4419          *
4420          * @param string $ins SQL statement to replace variables in
4421          * @return string The new SQL statement with variables replaced
4422          */
4423         protected function replaceVars( $ins ) {
4424                 $vars = $this->getSchemaVars();
4425                 return preg_replace_callback(
4426                         '!
4427                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
4428                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
4429                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
4430                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
4431                         !x',
4432                         function ( $m ) use ( $vars ) {
4433                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
4434                                 // check for both nonexistent keys *and* the empty string.
4435                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
4436                                         if ( $m[1] === 'i' ) {
4437                                                 return $this->indexName( $m[2] );
4438                                         } else {
4439                                                 return $this->tableName( $m[2] );
4440                                         }
4441                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
4442                                         return $this->addQuotes( $vars[$m[3]] );
4443                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
4444                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
4445                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
4446                                         return $vars[$m[5]];
4447                                 } else {
4448                                         return $m[0];
4449                                 }
4450                         },
4451                         $ins
4452                 );
4453         }
4454
4455         /**
4456          * Get schema variables. If none have been set via setSchemaVars(), then
4457          * use some defaults from the current object.
4458          *
4459          * @return array
4460          */
4461         protected function getSchemaVars() {
4462                 if ( $this->schemaVars ) {
4463                         return $this->schemaVars;
4464                 } else {
4465                         return $this->getDefaultSchemaVars();
4466                 }
4467         }
4468
4469         /**
4470          * Get schema variables to use if none have been set via setSchemaVars().
4471          *
4472          * Override this in derived classes to provide variables for tables.sql
4473          * and SQL patch files.
4474          *
4475          * @return array
4476          */
4477         protected function getDefaultSchemaVars() {
4478                 return [];
4479         }
4480
4481         public function lockIsFree( $lockName, $method ) {
4482                 // RDBMs methods for checking named locks may or may not count this thread itself.
4483                 // In MySQL, IS_FREE_LOCK() returns 0 if the thread already has the lock. This is
4484                 // the behavior choosen by the interface for this method.
4485                 return !isset( $this->namedLocksHeld[$lockName] );
4486         }
4487
4488         public function lock( $lockName, $method, $timeout = 5 ) {
4489                 $this->namedLocksHeld[$lockName] = 1;
4490
4491                 return true;
4492         }
4493
4494         public function unlock( $lockName, $method ) {
4495                 unset( $this->namedLocksHeld[$lockName] );
4496
4497                 return true;
4498         }
4499
4500         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
4501                 if ( $this->writesOrCallbacksPending() ) {
4502                         // This only flushes transactions to clear snapshots, not to write data
4503                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
4504                         throw new DBUnexpectedError(
4505                                 $this,
4506                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
4507                         );
4508                 }
4509
4510                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
4511                         return null;
4512                 }
4513
4514                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
4515                         if ( $this->trxLevel() ) {
4516                                 // There is a good chance an exception was thrown, causing any early return
4517                                 // from the caller. Let any error handler get a chance to issue rollback().
4518                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
4519                                 $this->onTransactionResolution(
4520                                         function () use ( $lockKey, $fname ) {
4521                                                 $this->unlock( $lockKey, $fname );
4522                                         },
4523                                         $fname
4524                                 );
4525                         } else {
4526                                 $this->unlock( $lockKey, $fname );
4527                         }
4528                 } );
4529
4530                 $this->commit( $fname, self::FLUSHING_INTERNAL );
4531
4532                 return $unlocker;
4533         }
4534
4535         public function namedLocksEnqueue() {
4536                 return false;
4537         }
4538
4539         public function tableLocksHaveTransactionScope() {
4540                 return true;
4541         }
4542
4543         final public function lockTables( array $read, array $write, $method ) {
4544                 if ( $this->writesOrCallbacksPending() ) {
4545                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
4546                 }
4547
4548                 if ( $this->tableLocksHaveTransactionScope() ) {
4549                         $this->startAtomic( $method );
4550                 }
4551
4552                 return $this->doLockTables( $read, $write, $method );
4553         }
4554
4555         /**
4556          * Helper function for lockTables() that handles the actual table locking
4557          *
4558          * @param array $read Array of tables to lock for read access
4559          * @param array $write Array of tables to lock for write access
4560          * @param string $method Name of caller
4561          * @return true
4562          */
4563         protected function doLockTables( array $read, array $write, $method ) {
4564                 return true;
4565         }
4566
4567         final public function unlockTables( $method ) {
4568                 if ( $this->tableLocksHaveTransactionScope() ) {
4569                         $this->endAtomic( $method );
4570
4571                         return true; // locks released on COMMIT/ROLLBACK
4572                 }
4573
4574                 return $this->doUnlockTables( $method );
4575         }
4576
4577         /**
4578          * Helper function for unlockTables() that handles the actual table unlocking
4579          *
4580          * @param string $method Name of caller
4581          * @return true
4582          */
4583         protected function doUnlockTables( $method ) {
4584                 return true;
4585         }
4586
4587         /**
4588          * Delete a table
4589          * @param string $tableName
4590          * @param string $fName
4591          * @return bool|ResultWrapper
4592          * @since 1.18
4593          */
4594         public function dropTable( $tableName, $fName = __METHOD__ ) {
4595                 if ( !$this->tableExists( $tableName, $fName ) ) {
4596                         return false;
4597                 }
4598                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
4599
4600                 return $this->query( $sql, $fName );
4601         }
4602
4603         public function getInfinity() {
4604                 return 'infinity';
4605         }
4606
4607         public function encodeExpiry( $expiry ) {
4608                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4609                         ? $this->getInfinity()
4610                         : $this->timestamp( $expiry );
4611         }
4612
4613         public function decodeExpiry( $expiry, $format = TS_MW ) {
4614                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
4615                         return 'infinity';
4616                 }
4617
4618                 return ConvertibleTimestamp::convert( $format, $expiry );
4619         }
4620
4621         public function setBigSelects( $value = true ) {
4622                 // no-op
4623         }
4624
4625         public function isReadOnly() {
4626                 return ( $this->getReadOnlyReason() !== false );
4627         }
4628
4629         /**
4630          * @return string|bool Reason this DB is read-only or false if it is not
4631          */
4632         protected function getReadOnlyReason() {
4633                 $reason = $this->getLBInfo( 'readOnlyReason' );
4634
4635                 return is_string( $reason ) ? $reason : false;
4636         }
4637
4638         public function setTableAliases( array $aliases ) {
4639                 $this->tableAliases = $aliases;
4640         }
4641
4642         public function setIndexAliases( array $aliases ) {
4643                 $this->indexAliases = $aliases;
4644         }
4645
4646         /**
4647          * Get the underlying binding connection handle
4648          *
4649          * Makes sure the connection resource is set (disconnects and ping() failure can unset it).
4650          * This catches broken callers than catch and ignore disconnection exceptions.
4651          * Unlike checking isOpen(), this is safe to call inside of open().
4652          *
4653          * @return mixed
4654          * @throws DBUnexpectedError
4655          * @since 1.26
4656          */
4657         protected function getBindingHandle() {
4658                 if ( !$this->conn ) {
4659                         throw new DBUnexpectedError(
4660                                 $this,
4661                                 'DB connection was already closed or the connection dropped.'
4662                         );
4663                 }
4664
4665                 return $this->conn;
4666         }
4667
4668         /**
4669          * @since 1.19
4670          * @return string
4671          */
4672         public function __toString() {
4673                 return (string)$this->conn;
4674         }
4675
4676         /**
4677          * Make sure that copies do not share the same client binding handle
4678          * @throws DBConnectionError
4679          */
4680         public function __clone() {
4681                 $this->connLogger->warning(
4682                         "Cloning " . static::class . " is not recommended; forking connection:\n" .
4683                         ( new RuntimeException() )->getTraceAsString()
4684                 );
4685
4686                 if ( $this->isOpen() ) {
4687                         // Open a new connection resource without messing with the old one
4688                         $this->opened = false;
4689                         $this->conn = false;
4690                         $this->trxEndCallbacks = []; // don't copy
4691                         $this->handleSessionLoss(); // no trx or locks anymore
4692                         $this->open(
4693                                 $this->server,
4694                                 $this->user,
4695                                 $this->password,
4696                                 $this->getDBname(),
4697                                 $this->dbSchema(),
4698                                 $this->tablePrefix()
4699                         );
4700                         $this->lastPing = microtime( true );
4701                 }
4702         }
4703
4704         /**
4705          * Called by serialize. Throw an exception when DB connection is serialized.
4706          * This causes problems on some database engines because the connection is
4707          * not restored on unserialize.
4708          */
4709         public function __sleep() {
4710                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
4711                         'the connection is not restored on wakeup.' );
4712         }
4713
4714         /**
4715          * Run a few simple sanity checks and close dangling connections
4716          */
4717         public function __destruct() {
4718                 if ( $this->trxLevel && $this->trxDoneWrites ) {
4719                         trigger_error( "Uncommitted DB writes (transaction from {$this->trxFname})." );
4720                 }
4721
4722                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
4723                 if ( $danglingWriters ) {
4724                         $fnames = implode( ', ', $danglingWriters );
4725                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
4726                 }
4727
4728                 if ( $this->conn ) {
4729                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
4730                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
4731                         Wikimedia\suppressWarnings();
4732                         $this->closeConnection();
4733                         Wikimedia\restoreWarnings();
4734                         $this->conn = false;
4735                         $this->opened = false;
4736                 }
4737         }
4738 }
4739
4740 /**
4741  * @deprecated since 1.28
4742  */
4743 class_alias( Database::class, 'DatabaseBase' );
4744
4745 /**
4746  * @deprecated since 1.29
4747  */
4748 class_alias( Database::class, 'Database' );