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 callable Error logging callback */
 101         protected $errorLogger;
 102         /** @var callable 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 (bool)( $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 $closed;
 991         }
 992
 993         /**
 994          * Make sure there is an open connection handle (alive or not) as a sanity check
 995          *
 996          * This guards against fatal errors to the binding handle not being defined
 997          * in cases where open() was never called or close() was already called
 998          *
 999          * @throws DBUnexpectedError
1000          */
1001         protected function assertHasConnectionHandle() {
1002                 if ( !$this->isOpen() ) {
1003                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
1004                 }
1005         }
1006
1007         /**
1008          * Make sure that this server is not marked as a replica nor read-only as a sanity check
1009          *
1010          * @throws DBUnexpectedError
1011          */
1012         protected function assertIsWritableMaster() {
1013                 if ( $this->getLBInfo( 'replica' ) === true ) {
1014                         throw new DBUnexpectedError(
1015                                 $this,
1016                                 'Write operations are not allowed on replica database connections.'
1017                         );
1018                 }
1019                 $reason = $this->getReadOnlyReason();
1020                 if ( $reason !== false ) {
1021                         throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
1022                 }
1023         }
1024
1025         /**
1026          * Closes underlying database connection
1027          * @since 1.20
1028          * @return bool Whether connection was closed successfully
1029          */
1030         abstract protected function closeConnection();
1031
1032         /**
1033          * @deprecated since 1.32
1034          * @param string $error Fallback message, if none is given by DB
1035          * @throws DBConnectionError
1036          */
1037         public function reportConnectionError( $error = 'Unknown error' ) {
1038                 call_user_func( $this->deprecationLogger, 'Use of ' . __METHOD__ . ' is deprecated.' );
1039                 throw new DBConnectionError( $this, $this->lastError() ?: $error );
1040         }
1041
1042         /**
1043          * Run a query and return a DBMS-dependent wrapper or boolean
1044          *
1045          * For SELECT queries, this returns either:
1046          *   - a) A driver-specific value/resource, only on success. This can be iterated
1047          *        over by calling fetchObject()/fetchRow() until there are no more rows.
1048          *        Alternatively, the result can be passed to resultObject() to obtain a
1049          *        ResultWrapper instance which can then be iterated over via "foreach".
1050          *   - b) False, on any query failure
1051          *
1052          * For non-SELECT queries, this returns either:
1053          *   - a) A driver-specific value/resource, only on success
1054          *   - b) True, only on success (e.g. no meaningful result other than "OK")
1055          *   - c) False, on any query failure
1056          *
1057          * @param string $sql SQL query
1058          * @return mixed|bool An object, resource, or true on success; false on failure
1059          */
1060         abstract protected function doQuery( $sql );
1061
1062         /**
1063          * Determine whether a query writes to the DB. When in doubt, this returns true.
1064          *
1065          * Main use cases:
1066          *
1067          * - Subsequent web requests should not need to wait for replication from
1068          *   the master position seen by this web request, unless this request made
1069          *   changes to the master. This is handled by ChronologyProtector by checking
1070          *   doneWrites() at the end of the request. doneWrites() returns true if any
1071          *   query set lastWriteTime; which query() does based on isWriteQuery().
1072          *
1073          * - Reject write queries to replica DBs, in query().
1074          *
1075          * @param string $sql
1076          * @return bool
1077          */
1078         protected function isWriteQuery( $sql ) {
1079                 // BEGIN and COMMIT queries are considered read queries here.
1080                 // Database backends and drivers (MySQL, MariaDB, php-mysqli) generally
1081                 // treat these as write queries, in that their results have "affected rows"
1082                 // as meta data as from writes, instead of "num rows" as from reads.
1083                 // But, we treat them as read queries because when reading data (from
1084                 // either replica or master) we use transactions to enable repeatable-read
1085                 // snapshots, which ensures we get consistent results from the same snapshot
1086                 // for all queries within a request. Use cases:
1087                 // - Treating these as writes would trigger ChronologyProtector (see method doc).
1088                 // - We use this method to reject writes to replicas, but we need to allow
1089                 //   use of transactions on replicas for read snapshots. This fine given
1090                 //   that transactions by themselves don't make changes, only actual writes
1091                 //   within the transaction matter, which we still detect.
1092                 return !preg_match(
1093                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SAVEPOINT|RELEASE|SET|SHOW|EXPLAIN|\(SELECT)\b/i',
1094                         $sql
1095                 );
1096         }
1097
1098         /**
1099          * @param string $sql
1100          * @return string|null
1101          */
1102         protected function getQueryVerb( $sql ) {
1103                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
1104         }
1105
1106         /**
1107          * Determine whether a SQL statement is sensitive to isolation level.
1108          *
1109          * A SQL statement is considered transactable if its result could vary
1110          * depending on the transaction isolation level. Operational commands
1111          * such as 'SET' and 'SHOW' are not considered to be transactable.
1112          *
1113          * Main purpose: Used by query() to decide whether to begin a transaction
1114          * before the current query (in DBO_TRX mode, on by default).
1115          *
1116          * @param string $sql
1117          * @return bool
1118          */
1119         protected function isTransactableQuery( $sql ) {
1120                 return !in_array(
1121                         $this->getQueryVerb( $sql ),
1122                         [ 'BEGIN', 'ROLLBACK', 'COMMIT', 'SET', 'SHOW', 'CREATE', 'ALTER' ],
1123                         true
1124                 );
1125         }
1126
1127         /**
1128          * @param string $sql A SQL query
1129          * @return bool Whether $sql is SQL for TEMPORARY table operation
1130          */
1131         protected function registerTempTableOperation( $sql ) {
1132                 if ( preg_match(
1133                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1134                         $sql,
1135                         $matches
1136                 ) ) {
1137                         $this->sessionTempTables[$matches[1]] = 1;
1138
1139                         return true;
1140                 } elseif ( preg_match(
1141                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1142                         $sql,
1143                         $matches
1144                 ) ) {
1145                         $isTemp = isset( $this->sessionTempTables[$matches[1]] );
1146                         unset( $this->sessionTempTables[$matches[1]] );
1147
1148                         return $isTemp;
1149                 } elseif ( preg_match(
1150                         '/^TRUNCATE\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1151                         $sql,
1152                         $matches
1153                 ) ) {
1154                         return isset( $this->sessionTempTables[$matches[1]] );
1155                 } elseif ( preg_match(
1156                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
1157                         $sql,
1158                         $matches
1159                 ) ) {
1160                         return isset( $this->sessionTempTables[$matches[1]] );
1161                 }
1162
1163                 return false;
1164         }
1165
1166         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
1167                 $this->assertTransactionStatus( $sql, $fname );
1168                 $this->assertHasConnectionHandle();
1169
1170                 $priorTransaction = $this->trxLevel;
1171                 $priorWritesPending = $this->writesOrCallbacksPending();
1172                 $this->lastQuery = $sql;
1173
1174                 if ( $this->isWriteQuery( $sql ) ) {
1175                         # In theory, non-persistent writes are allowed in read-only mode, but due to things
1176                         # like https://bugs.mysql.com/bug.php?id=33669 that might not work anyway...
1177                         $this->assertIsWritableMaster();
1178                         # Avoid treating temporary table operations as meaningful "writes"
1179                         $isEffectiveWrite = !$this->registerTempTableOperation( $sql );
1180                 } else {
1181                         $isEffectiveWrite = false;
1182                 }
1183
1184                 # Add trace comment to the begin of the sql string, right after the operator.
1185                 # Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598)
1186                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
1187
1188                 # Send the query to the server and fetch any corresponding errors
1189                 $ret = $this->attemptQuery( $sql, $commentedSql, $isEffectiveWrite, $fname );
1190                 $lastError = $this->lastError();
1191                 $lastErrno = $this->lastErrno();
1192
1193                 $recoverableSR = false; // recoverable statement rollback?
1194                 $recoverableCL = false; // recoverable connection loss?
1195
1196                 if ( $ret === false && $this->wasConnectionLoss() ) {
1197                         # Check if no meaningful session state was lost
1198                         $recoverableCL = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
1199                         # Update session state tracking and try to restore the connection
1200                         $reconnected = $this->replaceLostConnection( __METHOD__ );
1201                         # Silently resend the query to the server if it is safe and possible
1202                         if ( $recoverableCL && $reconnected ) {
1203                                 $ret = $this->attemptQuery( $sql, $commentedSql, $isEffectiveWrite, $fname );
1204                                 $lastError = $this->lastError();
1205                                 $lastErrno = $this->lastErrno();
1206
1207                                 if ( $ret === false && $this->wasConnectionLoss() ) {
1208                                         # Query probably causes disconnects; reconnect and do not re-run it
1209                                         $this->replaceLostConnection( __METHOD__ );
1210                                 } else {
1211                                         $recoverableCL = false; // connection does not need recovering
1212                                         $recoverableSR = $this->wasKnownStatementRollbackError();
1213                                 }
1214                         }
1215                 } else {
1216                         $recoverableSR = $this->wasKnownStatementRollbackError();
1217                 }
1218
1219                 if ( $ret === false ) {
1220                         if ( $priorTransaction ) {
1221                                 if ( $recoverableSR ) {
1222                                         # We're ignoring an error that caused just the current query to be aborted.
1223                                         # But log the cause so we can log a deprecation notice if a caller actually
1224                                         # does ignore it.
1225                                         $this->trxStatusIgnoredCause = [ $lastError, $lastErrno, $fname ];
1226                                 } elseif ( !$recoverableCL ) {
1227                                         # Either the query was aborted or all queries after BEGIN where aborted.
1228                                         # In the first case, the only options going forward are (a) ROLLBACK, or
1229                                         # (b) ROLLBACK TO SAVEPOINT (if one was set). If the later case, the only
1230                                         # option is ROLLBACK, since the snapshots would have been released.
1231                                         $this->trxStatus = self::STATUS_TRX_ERROR;
1232                                         $this->trxStatusCause =
1233                                                 $this->getQueryExceptionAndLog( $lastError, $lastErrno, $sql, $fname );
1234                                         $tempIgnore = false; // cannot recover
1235                                         $this->trxStatusIgnoredCause = null;
1236                                 }
1237                         }
1238
1239                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname, $tempIgnore );
1240                 }
1241
1242                 return $this->resultObject( $ret );
1243         }
1244
1245         /**
1246          * Wrapper for query() that also handles profiling, logging, and affected row count updates
1247          *
1248          * @param string $sql Original SQL query
1249          * @param string $commentedSql SQL query with debugging/trace comment
1250          * @param bool $isEffectiveWrite Whether the query is a (non-temporary table) write
1251          * @param string $fname Name of the calling function
1252          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
1253          *     object for a successful read query, or false on failure
1254          */
1255         private function attemptQuery( $sql, $commentedSql, $isEffectiveWrite, $fname ) {
1256                 $this->beginIfImplied( $sql, $fname );
1257
1258                 # Keep track of whether the transaction has write queries pending
1259                 if ( $isEffectiveWrite ) {
1260                         $this->lastWriteTime = microtime( true );
1261                         if ( $this->trxLevel && !$this->trxDoneWrites ) {
1262                                 $this->trxDoneWrites = true;
1263                                 $this->trxProfiler->transactionWritingIn(
1264                                         $this->server, $this->getDomainID(), $this->trxShortId );
1265                         }
1266                 }
1267
1268                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
1269                         $this->queryLogger->debug( "{$this->getDomainID()} {$commentedSql}" );
1270                 }
1271
1272                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1273                 # generalizeSQL() will probably cut down the query to reasonable
1274                 # logging size most of the time. The substr is really just a sanity check.
1275                 if ( $isMaster ) {
1276                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1277                 } else {
1278                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1279                 }
1280
1281                 # Include query transaction state
1282                 $queryProf .= $this->trxShortId ? " [TRX#{$this->trxShortId}]" : "";
1283
1284                 $startTime = microtime( true );
1285                 if ( $this->profiler ) {
1286                         $this->profiler->profileIn( $queryProf );
1287                 }
1288                 $this->affectedRowCount = null;
1289                 $ret = $this->doQuery( $commentedSql );
1290                 $this->affectedRowCount = $this->affectedRows();
1291                 if ( $this->profiler ) {
1292                         $this->profiler->profileOut( $queryProf );
1293                 }
1294                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1295
1296                 unset( $queryProfSection ); // profile out (if set)
1297
1298                 if ( $ret !== false ) {
1299                         $this->lastPing = $startTime;
1300                         if ( $isEffectiveWrite && $this->trxLevel ) {
1301                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1302                                 $this->trxWriteCallers[] = $fname;
1303                         }
1304                 }
1305
1306                 if ( $sql === self::PING_QUERY ) {
1307                         $this->rttEstimate = $queryRuntime;
1308                 }
1309
1310                 $this->trxProfiler->recordQueryCompletion(
1311                         $queryProf,
1312                         $startTime,
1313                         $isEffectiveWrite,
1314                         $isEffectiveWrite ? $this->affectedRows() : $this->numRows( $ret )
1315                 );
1316                 $this->queryLogger->debug( $sql, [
1317                         'method' => $fname,
1318                         'master' => $isMaster,
1319                         'runtime' => $queryRuntime,
1320                 ] );
1321
1322                 return $ret;
1323         }
1324
1325         /**
1326          * Start an implicit transaction if DBO_TRX is enabled and no transaction is active
1327          *
1328          * @param string $sql
1329          * @param string $fname
1330          */
1331         private function beginIfImplied( $sql, $fname ) {
1332                 if (
1333                         !$this->trxLevel &&
1334                         $this->getFlag( self::DBO_TRX ) &&
1335                         $this->isTransactableQuery( $sql )
1336                 ) {
1337                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
1338                         $this->trxAutomatic = true;
1339                 }
1340         }
1341
1342         /**
1343          * Update the estimated run-time of a query, not counting large row lock times
1344          *
1345          * LoadBalancer can be set to rollback transactions that will create huge replication
1346          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1347          * queries, like inserting a row can take a long time due to row locking. This method
1348          * uses some simple heuristics to discount those cases.
1349          *
1350          * @param string $sql A SQL write query
1351          * @param float $runtime Total runtime, including RTT
1352          * @param int $affected Affected row count
1353          */
1354         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1355                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1356                 $indicativeOfReplicaRuntime = true;
1357                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1358                         $verb = $this->getQueryVerb( $sql );
1359                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1360                         if ( $verb === 'INSERT' ) {
1361                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1362                         } elseif ( $verb === 'REPLACE' ) {
1363                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1364                         }
1365                 }
1366
1367                 $this->trxWriteDuration += $runtime;
1368                 $this->trxWriteQueryCount += 1;
1369                 $this->trxWriteAffectedRows += $affected;
1370                 if ( $indicativeOfReplicaRuntime ) {
1371                         $this->trxWriteAdjDuration += $runtime;
1372                         $this->trxWriteAdjQueryCount += 1;
1373                 }
1374         }
1375
1376         /**
1377          * Error out if the DB is not in a valid state for a query via query()
1378          *
1379          * @param string $sql
1380          * @param string $fname
1381          * @throws DBTransactionStateError
1382          */
1383         private function assertTransactionStatus( $sql, $fname ) {
1384                 $verb = $this->getQueryVerb( $sql );
1385                 if ( $verb === 'USE' ) {
1386                         throw new DBUnexpectedError( $this, "Got USE query; use selectDomain() instead." );
1387                 }
1388
1389                 if ( $verb === 'ROLLBACK' ) { // transaction/savepoint
1390                         return;
1391                 }
1392
1393                 if ( $this->trxStatus < self::STATUS_TRX_OK ) {
1394                         throw new DBTransactionStateError(
1395                                 $this,
1396                                 "Cannot execute query from $fname while transaction status is ERROR.",
1397                                 [],
1398                                 $this->trxStatusCause
1399                         );
1400                 } elseif ( $this->trxStatus === self::STATUS_TRX_OK && $this->trxStatusIgnoredCause ) {
1401                         list( $iLastError, $iLastErrno, $iFname ) = $this->trxStatusIgnoredCause;
1402                         call_user_func( $this->deprecationLogger,
1403                                 "Caller from $fname ignored an error originally raised from $iFname: " .
1404                                 "[$iLastErrno] $iLastError"
1405                         );
1406                         $this->trxStatusIgnoredCause = null;
1407                 }
1408         }
1409
1410         public function assertNoOpenTransactions() {
1411                 if ( $this->explicitTrxActive() ) {
1412                         throw new DBTransactionError(
1413                                 $this,
1414                                 "Explicit transaction still active. A caller may have caught an error. "
1415                                 . "Open transactions: " . $this->flatAtomicSectionList()
1416                         );
1417                 }
1418         }
1419
1420         /**
1421          * Determine whether it is safe to retry queries after a database connection is lost
1422          *
1423          * @param string $sql SQL query
1424          * @param bool $priorWritesPending Whether there is a transaction open with
1425          *     possible write queries or transaction pre-commit/idle callbacks
1426          *     waiting on it to finish.
1427          * @return bool True if it is safe to retry the query, false otherwise
1428          */
1429         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1430                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1431                 # Dropped connections also mean that named locks are automatically released.
1432                 # Only allow error suppression in autocommit mode or when the lost transaction
1433                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1434                 if ( $this->namedLocksHeld ) {
1435                         return false; // possible critical section violation
1436                 } elseif ( $this->sessionTempTables ) {
1437                         return false; // tables might be queried latter
1438                 } elseif ( $sql === 'COMMIT' ) {
1439                         return !$priorWritesPending; // nothing written anyway? (T127428)
1440                 } elseif ( $sql === 'ROLLBACK' ) {
1441                         return true; // transaction lost...which is also what was requested :)
1442                 } elseif ( $this->explicitTrxActive() ) {
1443                         return false; // don't drop atomocity and explicit snapshots
1444                 } elseif ( $priorWritesPending ) {
1445                         return false; // prior writes lost from implicit transaction
1446                 }
1447
1448                 return true;
1449         }
1450
1451         /**
1452          * Clean things up after session (and thus transaction) loss
1453          */
1454         private function handleSessionLoss() {
1455                 // Clean up tracking of session-level things...
1456                 // https://dev.mysql.com/doc/refman/5.7/en/implicit-commit.html
1457                 // https://www.postgresql.org/docs/9.2/static/sql-createtable.html (ignoring ON COMMIT)
1458                 $this->sessionTempTables = [];
1459                 // https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
1460                 // https://www.postgresql.org/docs/9.4/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
1461                 $this->namedLocksHeld = [];
1462                 // Session loss implies transaction loss
1463                 $this->handleTransactionLoss();
1464         }
1465
1466         /**
1467          * Clean things up after transaction loss
1468          */
1469         private function handleTransactionLoss() {
1470                 if ( $this->trxDoneWrites ) {
1471                         $this->trxProfiler->transactionWritingOut(
1472                                 $this->server,
1473                                 $this->getDomainID(),
1474                                 $this->trxShortId,
1475                                 $this->pendingWriteQueryDuration( self::ESTIMATE_TOTAL ),
1476                                 $this->trxWriteAffectedRows
1477                         );
1478                 }
1479                 $this->trxLevel = 0;
1480                 $this->trxAtomicCounter = 0;
1481                 $this->trxIdleCallbacks = []; // T67263; transaction already lost
1482                 $this->trxPreCommitCallbacks = []; // T67263; transaction already lost
1483                 try {
1484                         // Handle callbacks in trxEndCallbacks, e.g. onTransactionResolution().
1485                         // If callback suppression is set then the array will remain unhandled.
1486                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1487                 } catch ( Exception $ex ) {
1488                         // Already logged; move on...
1489                 }
1490                 try {
1491                         // Handle callbacks in trxRecurringCallbacks, e.g. setTransactionListener()
1492                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1493                 } catch ( Exception $ex ) {
1494                         // Already logged; move on...
1495                 }
1496         }
1497
1498         /**
1499          * Checks whether the cause of the error is detected to be a timeout.
1500          *
1501          * It returns false by default, and not all engines support detecting this yet.
1502          * If this returns false, it will be treated as a generic query error.
1503          *
1504          * @param string $error Error text
1505          * @param int $errno Error number
1506          * @return bool
1507          */
1508         protected function wasQueryTimeout( $error, $errno ) {
1509                 return false;
1510         }
1511
1512         /**
1513          * Report a query error. Log the error, and if neither the object ignore
1514          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1515          *
1516          * @param string $error
1517          * @param int $errno
1518          * @param string $sql
1519          * @param string $fname
1520          * @param bool $tempIgnore
1521          * @throws DBQueryError
1522          */
1523         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1524                 if ( $tempIgnore ) {
1525                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1526                 } else {
1527                         $exception = $this->getQueryExceptionAndLog( $error, $errno, $sql, $fname );
1528
1529                         throw $exception;
1530                 }
1531         }
1532
1533         /**
1534          * @param string $error
1535          * @param string|int $errno
1536          * @param string $sql
1537          * @param string $fname
1538          * @return DBError
1539          */
1540         private function getQueryExceptionAndLog( $error, $errno, $sql, $fname ) {
1541                 $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1542                 $this->queryLogger->error(
1543                         "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1544                         $this->getLogContext( [
1545                                 'method' => __METHOD__,
1546                                 'errno' => $errno,
1547                                 'error' => $error,
1548                                 'sql1line' => $sql1line,
1549                                 'fname' => $fname,
1550                                 'trace' => ( new RuntimeException() )->getTraceAsString()
1551                         ] )
1552                 );
1553                 $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1554                 $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1555                 if ( $wasQueryTimeout ) {
1556                         $e = new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1557                 } else {
1558                         $e = new DBQueryError( $this, $error, $errno, $sql, $fname );
1559                 }
1560
1561                 return $e;
1562         }
1563
1564         public function freeResult( $res ) {
1565         }
1566
1567         public function selectField(
1568                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1569         ) {
1570                 if ( $var === '*' ) { // sanity
1571                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1572                 }
1573
1574                 if ( !is_array( $options ) ) {
1575                         $options = [ $options ];
1576                 }
1577
1578                 $options['LIMIT'] = 1;
1579
1580                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1581                 if ( $res === false || !$this->numRows( $res ) ) {
1582                         return false;
1583                 }
1584
1585                 $row = $this->fetchRow( $res );
1586
1587                 if ( $row !== false ) {
1588                         return reset( $row );
1589                 } else {
1590                         return false;
1591                 }
1592         }
1593
1594         public function selectFieldValues(
1595                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1596         ) {
1597                 if ( $var === '*' ) { // sanity
1598                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1599                 } elseif ( !is_string( $var ) ) { // sanity
1600                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1601                 }
1602
1603                 if ( !is_array( $options ) ) {
1604                         $options = [ $options ];
1605                 }
1606
1607                 $res = $this->select( $table, [ 'value' => $var ], $cond, $fname, $options, $join_conds );
1608                 if ( $res === false ) {
1609                         return false;
1610                 }
1611
1612                 $values = [];
1613                 foreach ( $res as $row ) {
1614                         $values[] = $row->value;
1615                 }
1616
1617                 return $values;
1618         }
1619
1620         /**
1621          * Returns an optional USE INDEX clause to go after the table, and a
1622          * string to go at the end of the query.
1623          *
1624          * @param array $options Associative array of options to be turned into
1625          *   an SQL query, valid keys are listed in the function.
1626          * @return array
1627          * @see Database::select()
1628          */
1629         protected function makeSelectOptions( $options ) {
1630                 $preLimitTail = $postLimitTail = '';
1631                 $startOpts = '';
1632
1633                 $noKeyOptions = [];
1634
1635                 foreach ( $options as $key => $option ) {
1636                         if ( is_numeric( $key ) ) {
1637                                 $noKeyOptions[$option] = true;
1638                         }
1639                 }
1640
1641                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1642
1643                 $preLimitTail .= $this->makeOrderBy( $options );
1644
1645                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1646                         $postLimitTail .= ' FOR UPDATE';
1647                 }
1648
1649                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1650                         $postLimitTail .= ' LOCK IN SHARE MODE';
1651                 }
1652
1653                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1654                         $startOpts .= 'DISTINCT';
1655                 }
1656
1657                 # Various MySQL extensions
1658                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1659                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1660                 }
1661
1662                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1663                         $startOpts .= ' HIGH_PRIORITY';
1664                 }
1665
1666                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1667                         $startOpts .= ' SQL_BIG_RESULT';
1668                 }
1669
1670                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1671                         $startOpts .= ' SQL_BUFFER_RESULT';
1672                 }
1673
1674                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1675                         $startOpts .= ' SQL_SMALL_RESULT';
1676                 }
1677
1678                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1679                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1680                 }
1681
1682                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1683                         $startOpts .= ' SQL_CACHE';
1684                 }
1685
1686                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1687                         $startOpts .= ' SQL_NO_CACHE';
1688                 }
1689
1690                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1691                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1692                 } else {
1693                         $useIndex = '';
1694                 }
1695                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1696                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1697                 } else {
1698                         $ignoreIndex = '';
1699                 }
1700
1701                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1702         }
1703
1704         /**
1705          * Returns an optional GROUP BY with an optional HAVING
1706          *
1707          * @param array $options Associative array of options
1708          * @return string
1709          * @see Database::select()
1710          * @since 1.21
1711          */
1712         protected function makeGroupByWithHaving( $options ) {
1713                 $sql = '';
1714                 if ( isset( $options['GROUP BY'] ) ) {
1715                         $gb = is_array( $options['GROUP BY'] )
1716                                 ? implode( ',', $options['GROUP BY'] )
1717                                 : $options['GROUP BY'];
1718                         $sql .= ' GROUP BY ' . $gb;
1719                 }
1720                 if ( isset( $options['HAVING'] ) ) {
1721                         $having = is_array( $options['HAVING'] )
1722                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1723                                 : $options['HAVING'];
1724                         $sql .= ' HAVING ' . $having;
1725                 }
1726
1727                 return $sql;
1728         }
1729
1730         /**
1731          * Returns an optional ORDER BY
1732          *
1733          * @param array $options Associative array of options
1734          * @return string
1735          * @see Database::select()
1736          * @since 1.21
1737          */
1738         protected function makeOrderBy( $options ) {
1739                 if ( isset( $options['ORDER BY'] ) ) {
1740                         $ob = is_array( $options['ORDER BY'] )
1741                                 ? implode( ',', $options['ORDER BY'] )
1742                                 : $options['ORDER BY'];
1743
1744                         return ' ORDER BY ' . $ob;
1745                 }
1746
1747                 return '';
1748         }
1749
1750         public function select(
1751                 $table, $vars, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1752         ) {
1753                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1754
1755                 return $this->query( $sql, $fname );
1756         }
1757
1758         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1759                 $options = [], $join_conds = []
1760         ) {
1761                 if ( is_array( $vars ) ) {
1762                         $fields = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1763                 } else {
1764                         $fields = $vars;
1765                 }
1766
1767                 $options = (array)$options;
1768                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1769                         ? $options['USE INDEX']
1770                         : [];
1771                 $ignoreIndexes = (
1772                         isset( $options['IGNORE INDEX'] ) &&
1773                         is_array( $options['IGNORE INDEX'] )
1774                 )
1775                         ? $options['IGNORE INDEX']
1776                         : [];
1777
1778                 if (
1779                         $this->selectOptionsIncludeLocking( $options ) &&
1780                         $this->selectFieldsOrOptionsAggregate( $vars, $options )
1781                 ) {
1782                         // Some DB types (postgres/oracle) disallow FOR UPDATE with aggregate
1783                         // functions. Discourage use of such queries to encourage compatibility.
1784                         call_user_func(
1785                                 $this->deprecationLogger,
1786                                 __METHOD__ . ": aggregation used with a locking SELECT ($fname)."
1787                         );
1788                 }
1789
1790                 if ( is_array( $table ) ) {
1791                         $from = ' FROM ' .
1792                                 $this->tableNamesWithIndexClauseOrJOIN(
1793                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1794                 } elseif ( $table != '' ) {
1795                         $from = ' FROM ' .
1796                                 $this->tableNamesWithIndexClauseOrJOIN(
1797                                         [ $table ], $useIndexes, $ignoreIndexes, [] );
1798                 } else {
1799                         $from = '';
1800                 }
1801
1802                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1803                         $this->makeSelectOptions( $options );
1804
1805                 if ( is_array( $conds ) ) {
1806                         $conds = $this->makeList( $conds, self::LIST_AND );
1807                 }
1808
1809                 if ( $conds === null || $conds === false ) {
1810                         $this->queryLogger->warning(
1811                                 __METHOD__
1812                                 . ' called from '
1813                                 . $fname
1814                                 . ' with incorrect parameters: $conds must be a string or an array'
1815                         );
1816                         $conds = '';
1817                 }
1818
1819                 if ( $conds === '' || $conds === '*' ) {
1820                         $sql = "SELECT $startOpts $fields $from $useIndex $ignoreIndex $preLimitTail";
1821                 } elseif ( is_string( $conds ) ) {
1822                         $sql = "SELECT $startOpts $fields $from $useIndex $ignoreIndex " .
1823                                 "WHERE $conds $preLimitTail";
1824                 } else {
1825                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1826                 }
1827
1828                 if ( isset( $options['LIMIT'] ) ) {
1829                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1830                                 $options['OFFSET'] ?? false );
1831                 }
1832                 $sql = "$sql $postLimitTail";
1833
1834                 if ( isset( $options['EXPLAIN'] ) ) {
1835                         $sql = 'EXPLAIN ' . $sql;
1836                 }
1837
1838                 return $sql;
1839         }
1840
1841         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1842                 $options = [], $join_conds = []
1843         ) {
1844                 $options = (array)$options;
1845                 $options['LIMIT'] = 1;
1846                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1847
1848                 if ( $res === false ) {
1849                         return false;
1850                 }
1851
1852                 if ( !$this->numRows( $res ) ) {
1853                         return false;
1854                 }
1855
1856                 $obj = $this->fetchObject( $res );
1857
1858                 return $obj;
1859         }
1860
1861         public function estimateRowCount(
1862                 $table, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1863         ) {
1864                 $conds = $this->normalizeConditions( $conds, $fname );
1865                 $column = $this->extractSingleFieldFromList( $var );
1866                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1867                         $conds[] = "$column IS NOT NULL";
1868                 }
1869
1870                 $res = $this->select(
1871                         $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options, $join_conds
1872                 );
1873                 $row = $res ? $this->fetchRow( $res ) : [];
1874
1875                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1876         }
1877
1878         public function selectRowCount(
1879                 $tables, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1880         ) {
1881                 $conds = $this->normalizeConditions( $conds, $fname );
1882                 $column = $this->extractSingleFieldFromList( $var );
1883                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1884                         $conds[] = "$column IS NOT NULL";
1885                 }
1886
1887                 $res = $this->select(
1888                         [
1889                                 'tmp_count' => $this->buildSelectSubquery(
1890                                         $tables,
1891                                         '1',
1892                                         $conds,
1893                                         $fname,
1894                                         $options,
1895                                         $join_conds
1896                                 )
1897                         ],
1898                         [ 'rowcount' => 'COUNT(*)' ],
1899                         [],
1900                         $fname
1901                 );
1902                 $row = $res ? $this->fetchRow( $res ) : [];
1903
1904                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1905         }
1906
1907         /**
1908          * @param string|array $options
1909          * @return bool
1910          */
1911         private function selectOptionsIncludeLocking( $options ) {
1912                 $options = (array)$options;
1913                 foreach ( [ 'FOR UPDATE', 'LOCK IN SHARE MODE' ] as $lock ) {
1914                         if ( in_array( $lock, $options, true ) ) {
1915                                 return true;
1916                         }
1917                 }
1918
1919                 return false;
1920         }
1921
1922         /**
1923          * @param array|string $fields
1924          * @param array|string $options
1925          * @return bool
1926          */
1927         private function selectFieldsOrOptionsAggregate( $fields, $options ) {
1928                 foreach ( (array)$options as $key => $value ) {
1929                         if ( is_string( $key ) ) {
1930                                 if ( preg_match( '/^(?:GROUP BY|HAVING)$/i', $key ) ) {
1931                                         return true;
1932                                 }
1933                         } elseif ( is_string( $value ) ) {
1934                                 if ( preg_match( '/^(?:DISTINCT|DISTINCTROW)$/i', $value ) ) {
1935                                         return true;
1936                                 }
1937                         }
1938                 }
1939
1940                 $regex = '/^(?:COUNT|MIN|MAX|SUM|GROUP_CONCAT|LISTAGG|ARRAY_AGG)\s*\\(/i';
1941                 foreach ( (array)$fields as $field ) {
1942                         if ( is_string( $field ) && preg_match( $regex, $field ) ) {
1943                                 return true;
1944                         }
1945                 }
1946
1947                 return false;
1948         }
1949
1950         /**
1951          * @param array|string $conds
1952          * @param string $fname
1953          * @return array
1954          */
1955         final protected function normalizeConditions( $conds, $fname ) {
1956                 if ( $conds === null || $conds === false ) {
1957                         $this->queryLogger->warning(
1958                                 __METHOD__
1959                                 . ' called from '
1960                                 . $fname
1961                                 . ' with incorrect parameters: $conds must be a string or an array'
1962                         );
1963                         $conds = '';
1964                 }
1965
1966                 if ( !is_array( $conds ) ) {
1967                         $conds = ( $conds === '' ) ? [] : [ $conds ];
1968                 }
1969
1970                 return $conds;
1971         }
1972
1973         /**
1974          * @param array|string $var Field parameter in the style of select()
1975          * @return string|null Column name or null; ignores aliases
1976          * @throws DBUnexpectedError Errors out if multiple columns are given
1977          */
1978         final protected function extractSingleFieldFromList( $var ) {
1979                 if ( is_array( $var ) ) {
1980                         if ( !$var ) {
1981                                 $column = null;
1982                         } elseif ( count( $var ) == 1 ) {
1983                                 $column = $var[0] ?? reset( $var );
1984                         } else {
1985                                 throw new DBUnexpectedError( $this, __METHOD__ . ': got multiple columns.' );
1986                         }
1987                 } else {
1988                         $column = $var;
1989                 }
1990
1991                 return $column;
1992         }
1993
1994         public function lockForUpdate(
1995                 $table, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1996         ) {
1997                 if ( !$this->trxLevel && !$this->getFlag( self::DBO_TRX ) ) {
1998                         throw new DBUnexpectedError(
1999                                 $this,
2000                                 __METHOD__ . ': no transaction is active nor is DBO_TRX set'
2001                         );
2002                 }
2003
2004                 $options = (array)$options;
2005                 $options[] = 'FOR UPDATE';
2006
2007                 return $this->selectRowCount( $table, '*', $conds, $fname, $options, $join_conds );
2008         }
2009
2010         /**
2011          * Removes most variables from an SQL query and replaces them with X or N for numbers.
2012          * It's only slightly flawed. Don't use for anything important.
2013          *
2014          * @param string $sql A SQL Query
2015          *
2016          * @return string
2017          */
2018         protected static function generalizeSQL( $sql ) {
2019                 # This does the same as the regexp below would do, but in such a way
2020                 # as to avoid crashing php on some large strings.
2021                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
2022
2023                 $sql = str_replace( "\\\\", '', $sql );
2024                 $sql = str_replace( "\\'", '', $sql );
2025                 $sql = str_replace( "\\\"", '', $sql );
2026                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
2027                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
2028
2029                 # All newlines, tabs, etc replaced by single space
2030                 $sql = preg_replace( '/\s+/', ' ', $sql );
2031
2032                 # All numbers => N,
2033                 # except the ones surrounded by characters, e.g. l10n
2034                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
2035                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
2036
2037                 return $sql;
2038         }
2039
2040         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
2041                 $info = $this->fieldInfo( $table, $field );
2042
2043                 return (bool)$info;
2044         }
2045
2046         public function indexExists( $table, $index, $fname = __METHOD__ ) {
2047                 if ( !$this->tableExists( $table ) ) {
2048                         return null;
2049                 }
2050
2051                 $info = $this->indexInfo( $table, $index, $fname );
2052                 if ( is_null( $info ) ) {
2053                         return null;
2054                 } else {
2055                         return $info !== false;
2056                 }
2057         }
2058
2059         abstract public function tableExists( $table, $fname = __METHOD__ );
2060
2061         public function indexUnique( $table, $index ) {
2062                 $indexInfo = $this->indexInfo( $table, $index );
2063
2064                 if ( !$indexInfo ) {
2065                         return null;
2066                 }
2067
2068                 return !$indexInfo[0]->Non_unique;
2069         }
2070
2071         /**
2072          * Helper for Database::insert().
2073          *
2074          * @param array $options
2075          * @return string
2076          */
2077         protected function makeInsertOptions( $options ) {
2078                 return implode( ' ', $options );
2079         }
2080
2081         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
2082                 # No rows to insert, easy just return now
2083                 if ( !count( $a ) ) {
2084                         return true;
2085                 }
2086
2087                 $table = $this->tableName( $table );
2088
2089                 if ( !is_array( $options ) ) {
2090                         $options = [ $options ];
2091                 }
2092
2093                 $options = $this->makeInsertOptions( $options );
2094
2095                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
2096                         $multi = true;
2097                         $keys = array_keys( $a[0] );
2098                 } else {
2099                         $multi = false;
2100                         $keys = array_keys( $a );
2101                 }
2102
2103                 $sql = 'INSERT ' . $options .
2104                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
2105
2106                 if ( $multi ) {
2107                         $first = true;
2108                         foreach ( $a as $row ) {
2109                                 if ( $first ) {
2110                                         $first = false;
2111                                 } else {
2112                                         $sql .= ',';
2113                                 }
2114                                 $sql .= '(' . $this->makeList( $row ) . ')';
2115                         }
2116                 } else {
2117                         $sql .= '(' . $this->makeList( $a ) . ')';
2118                 }
2119
2120                 $this->query( $sql, $fname );
2121
2122                 return true;
2123         }
2124
2125         /**
2126          * Make UPDATE options array for Database::makeUpdateOptions
2127          *
2128          * @param array $options
2129          * @return array
2130          */
2131         protected function makeUpdateOptionsArray( $options ) {
2132                 if ( !is_array( $options ) ) {
2133                         $options = [ $options ];
2134                 }
2135
2136                 $opts = [];
2137
2138                 if ( in_array( 'IGNORE', $options ) ) {
2139                         $opts[] = 'IGNORE';
2140                 }
2141
2142                 return $opts;
2143         }
2144
2145         /**
2146          * Make UPDATE options for the Database::update function
2147          *
2148          * @param array $options The options passed to Database::update
2149          * @return string
2150          */
2151         protected function makeUpdateOptions( $options ) {
2152                 $opts = $this->makeUpdateOptionsArray( $options );
2153
2154                 return implode( ' ', $opts );
2155         }
2156
2157         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
2158                 $table = $this->tableName( $table );
2159                 $opts = $this->makeUpdateOptions( $options );
2160                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
2161
2162                 if ( $conds !== [] && $conds !== '*' ) {
2163                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
2164                 }
2165
2166                 $this->query( $sql, $fname );
2167
2168                 return true;
2169         }
2170
2171         public function makeList( $a, $mode = self::LIST_COMMA ) {
2172                 if ( !is_array( $a ) ) {
2173                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
2174                 }
2175
2176                 $first = true;
2177                 $list = '';
2178
2179                 foreach ( $a as $field => $value ) {
2180                         if ( !$first ) {
2181                                 if ( $mode == self::LIST_AND ) {
2182                                         $list .= ' AND ';
2183                                 } elseif ( $mode == self::LIST_OR ) {
2184                                         $list .= ' OR ';
2185                                 } else {
2186                                         $list .= ',';
2187                                 }
2188                         } else {
2189                                 $first = false;
2190                         }
2191
2192                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
2193                                 $list .= "($value)";
2194                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
2195                                 $list .= "$value";
2196                         } elseif (
2197                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
2198                         ) {
2199                                 // Remove null from array to be handled separately if found
2200                                 $includeNull = false;
2201                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
2202                                         $includeNull = true;
2203                                         unset( $value[$nullKey] );
2204                                 }
2205                                 if ( count( $value ) == 0 && !$includeNull ) {
2206                                         throw new InvalidArgumentException(
2207                                                 __METHOD__ . ": empty input for field $field" );
2208                                 } elseif ( count( $value ) == 0 ) {
2209                                         // only check if $field is null
2210                                         $list .= "$field IS NULL";
2211                                 } else {
2212                                         // IN clause contains at least one valid element
2213                                         if ( $includeNull ) {
2214                                                 // Group subconditions to ensure correct precedence
2215                                                 $list .= '(';
2216                                         }
2217                                         if ( count( $value ) == 1 ) {
2218                                                 // Special-case single values, as IN isn't terribly efficient
2219                                                 // Don't necessarily assume the single key is 0; we don't
2220                                                 // enforce linear numeric ordering on other arrays here.
2221                                                 $value = array_values( $value )[0];
2222                                                 $list .= $field . " = " . $this->addQuotes( $value );
2223                                         } else {
2224                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
2225                                         }
2226                                         // if null present in array, append IS NULL
2227                                         if ( $includeNull ) {
2228                                                 $list .= " OR $field IS NULL)";
2229                                         }
2230                                 }
2231                         } elseif ( $value === null ) {
2232                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
2233                                         $list .= "$field IS ";
2234                                 } elseif ( $mode == self::LIST_SET ) {
2235                                         $list .= "$field = ";
2236                                 }
2237                                 $list .= 'NULL';
2238                         } else {
2239                                 if (
2240                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
2241                                 ) {
2242                                         $list .= "$field = ";
2243                                 }
2244                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
2245                         }
2246                 }
2247
2248                 return $list;
2249         }
2250
2251         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2252                 $conds = [];
2253
2254                 foreach ( $data as $base => $sub ) {
2255                         if ( count( $sub ) ) {
2256                                 $conds[] = $this->makeList(
2257                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
2258                                         self::LIST_AND );
2259                         }
2260                 }
2261
2262                 if ( $conds ) {
2263                         return $this->makeList( $conds, self::LIST_OR );
2264                 } else {
2265                         // Nothing to search for...
2266                         return false;
2267                 }
2268         }
2269
2270         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2271                 return $valuename;
2272         }
2273
2274         public function bitNot( $field ) {
2275                 return "(~$field)";
2276         }
2277
2278         public function bitAnd( $fieldLeft, $fieldRight ) {
2279                 return "($fieldLeft & $fieldRight)";
2280         }
2281
2282         public function bitOr( $fieldLeft, $fieldRight ) {
2283                 return "($fieldLeft | $fieldRight)";
2284         }
2285
2286         public function buildConcat( $stringList ) {
2287                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2288         }
2289
2290         public function buildGroupConcatField(
2291                 $delim, $table, $field, $conds = '', $join_conds = []
2292         ) {
2293                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
2294
2295                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
2296         }
2297
2298         public function buildSubstring( $input, $startPosition, $length = null ) {
2299                 $this->assertBuildSubstringParams( $startPosition, $length );
2300                 $functionBody = "$input FROM $startPosition";
2301                 if ( $length !== null ) {
2302                         $functionBody .= " FOR $length";
2303                 }
2304                 return 'SUBSTRING(' . $functionBody . ')';
2305         }
2306
2307         /**
2308          * Check type and bounds for parameters to self::buildSubstring()
2309          *
2310          * All supported databases have substring functions that behave the same for
2311          * positive $startPosition and non-negative $length, but behaviors differ when
2312          * given 0 or negative $startPosition or negative $length. The simplest
2313          * solution to that is to just forbid those values.
2314          *
2315          * @param int $startPosition
2316          * @param int|null $length
2317          * @since 1.31
2318          */
2319         protected function assertBuildSubstringParams( $startPosition, $length ) {
2320                 if ( !is_int( $startPosition ) || $startPosition <= 0 ) {
2321                         throw new InvalidArgumentException(
2322                                 '$startPosition must be a positive integer'
2323                         );
2324                 }
2325                 if ( !( is_int( $length ) && $length >= 0 || $length === null ) ) {
2326                         throw new InvalidArgumentException(
2327                                 '$length must be null or an integer greater than or equal to 0'
2328                         );
2329                 }
2330         }
2331
2332         public function buildStringCast( $field ) {
2333                 // In theory this should work for any standards-compliant
2334                 // SQL implementation, although it may not be the best way to do it.
2335                 return "CAST( $field AS CHARACTER )";
2336         }
2337
2338         public function buildIntegerCast( $field ) {
2339                 return 'CAST( ' . $field . ' AS INTEGER )';
2340         }
2341
2342         public function buildSelectSubquery(
2343                 $table, $vars, $conds = '', $fname = __METHOD__,
2344                 $options = [], $join_conds = []
2345         ) {
2346                 return new Subquery(
2347                         $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds )
2348                 );
2349         }
2350
2351         public function databasesAreIndependent() {
2352                 return false;
2353         }
2354
2355         final public function selectDB( $db ) {
2356                 $this->selectDomain( new DatabaseDomain(
2357                         $db,
2358                         $this->currentDomain->getSchema(),
2359                         $this->currentDomain->getTablePrefix()
2360                 ) );
2361
2362                 return true;
2363         }
2364
2365         final public function selectDomain( $domain ) {
2366                 $this->doSelectDomain( DatabaseDomain::newFromId( $domain ) );
2367         }
2368
2369         protected function doSelectDomain( DatabaseDomain $domain ) {
2370                 $this->currentDomain = $domain;
2371         }
2372
2373         public function getDBname() {
2374                 return $this->currentDomain->getDatabase();
2375         }
2376
2377         public function getServer() {
2378                 return $this->server;
2379         }
2380
2381         public function tableName( $name, $format = 'quoted' ) {
2382                 if ( $name instanceof Subquery ) {
2383                         throw new DBUnexpectedError(
2384                                 $this,
2385                                 __METHOD__ . ': got Subquery instance when expecting a string.'
2386                         );
2387                 }
2388
2389                 # Skip the entire process when we have a string quoted on both ends.
2390                 # Note that we check the end so that we will still quote any use of
2391                 # use of `database`.table. But won't break things if someone wants
2392                 # to query a database table with a dot in the name.
2393                 if ( $this->isQuotedIdentifier( $name ) ) {
2394                         return $name;
2395                 }
2396
2397                 # Lets test for any bits of text that should never show up in a table
2398                 # name. Basically anything like JOIN or ON which are actually part of
2399                 # SQL queries, but may end up inside of the table value to combine
2400                 # sql. Such as how the API is doing.
2401                 # Note that we use a whitespace test rather than a \b test to avoid
2402                 # any remote case where a word like on may be inside of a table name
2403                 # surrounded by symbols which may be considered word breaks.
2404                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2405                         $this->queryLogger->warning(
2406                                 __METHOD__ . ": use of subqueries is not supported this way.",
2407                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
2408                         );
2409
2410                         return $name;
2411                 }
2412
2413                 # Split database and table into proper variables.
2414                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
2415
2416                 # Quote $table and apply the prefix if not quoted.
2417                 # $tableName might be empty if this is called from Database::replaceVars()
2418                 $tableName = "{$prefix}{$table}";
2419                 if ( $format === 'quoted'
2420                         && !$this->isQuotedIdentifier( $tableName )
2421                         && $tableName !== ''
2422                 ) {
2423                         $tableName = $this->addIdentifierQuotes( $tableName );
2424                 }
2425
2426                 # Quote $schema and $database and merge them with the table name if needed
2427                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
2428                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
2429
2430                 return $tableName;
2431         }
2432
2433         /**
2434          * Get the table components needed for a query given the currently selected database
2435          *
2436          * @param string $name Table name in the form of db.schema.table, db.table, or table
2437          * @return array (DB name or "" for default, schema name, table prefix, table name)
2438          */
2439         protected function qualifiedTableComponents( $name ) {
2440                 # We reverse the explode so that database.table and table both output the correct table.
2441                 $dbDetails = explode( '.', $name, 3 );
2442                 if ( count( $dbDetails ) == 3 ) {
2443                         list( $database, $schema, $table ) = $dbDetails;
2444                         # We don't want any prefix added in this case
2445                         $prefix = '';
2446                 } elseif ( count( $dbDetails ) == 2 ) {
2447                         list( $database, $table ) = $dbDetails;
2448                         # We don't want any prefix added in this case
2449                         $prefix = '';
2450                         # In dbs that support it, $database may actually be the schema
2451                         # but that doesn't affect any of the functionality here
2452                         $schema = '';
2453                 } else {
2454                         list( $table ) = $dbDetails;
2455                         if ( isset( $this->tableAliases[$table] ) ) {
2456                                 $database = $this->tableAliases[$table]['dbname'];
2457                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
2458                                         ? $this->tableAliases[$table]['schema']
2459                                         : $this->relationSchemaQualifier();
2460                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
2461                                         ? $this->tableAliases[$table]['prefix']
2462                                         : $this->tablePrefix();
2463                         } else {
2464                                 $database = '';
2465                                 $schema = $this->relationSchemaQualifier(); # Default schema
2466                                 $prefix = $this->tablePrefix(); # Default prefix
2467                         }
2468                 }
2469
2470                 return [ $database, $schema, $prefix, $table ];
2471         }
2472
2473         /**
2474          * @param string|null $namespace Database or schema
2475          * @param string $relation Name of table, view, sequence, etc...
2476          * @param string $format One of (raw, quoted)
2477          * @return string Relation name with quoted and merged $namespace as needed
2478          */
2479         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
2480                 if ( strlen( $namespace ) ) {
2481                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
2482                                 $namespace = $this->addIdentifierQuotes( $namespace );
2483                         }
2484                         $relation = $namespace . '.' . $relation;
2485                 }
2486
2487                 return $relation;
2488         }
2489
2490         public function tableNames() {
2491                 $inArray = func_get_args();
2492                 $retVal = [];
2493
2494                 foreach ( $inArray as $name ) {
2495                         $retVal[$name] = $this->tableName( $name );
2496                 }
2497
2498                 return $retVal;
2499         }
2500
2501         public function tableNamesN() {
2502                 $inArray = func_get_args();
2503                 $retVal = [];
2504
2505                 foreach ( $inArray as $name ) {
2506                         $retVal[] = $this->tableName( $name );
2507                 }
2508
2509                 return $retVal;
2510         }
2511
2512         /**
2513          * Get an aliased table name
2514          *
2515          * This returns strings like "tableName AS newTableName" for aliased tables
2516          * and "(SELECT * from tableA) newTablename" for subqueries (e.g. derived tables)
2517          *
2518          * @see Database::tableName()
2519          * @param string|Subquery $table Table name or object with a 'sql' field
2520          * @param string|bool $alias Table alias (optional)
2521          * @return string SQL name for aliased table. Will not alias a table to its own name
2522          */
2523         protected function tableNameWithAlias( $table, $alias = false ) {
2524                 if ( is_string( $table ) ) {
2525                         $quotedTable = $this->tableName( $table );
2526                 } elseif ( $table instanceof Subquery ) {
2527                         $quotedTable = (string)$table;
2528                 } else {
2529                         throw new InvalidArgumentException( "Table must be a string or Subquery." );
2530                 }
2531
2532                 if ( !strlen( $alias ) || $alias === $table ) {
2533                         if ( $table instanceof Subquery ) {
2534                                 throw new InvalidArgumentException( "Subquery table missing alias." );
2535                         }
2536
2537                         return $quotedTable;
2538                 } else {
2539                         return $quotedTable . ' ' . $this->addIdentifierQuotes( $alias );
2540                 }
2541         }
2542
2543         /**
2544          * Gets an array of aliased table names
2545          *
2546          * @param array $tables [ [alias] => table ]
2547          * @return string[] See tableNameWithAlias()
2548          */
2549         protected function tableNamesWithAlias( $tables ) {
2550                 $retval = [];
2551                 foreach ( $tables as $alias => $table ) {
2552                         if ( is_numeric( $alias ) ) {
2553                                 $alias = $table;
2554                         }
2555                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2556                 }
2557
2558                 return $retval;
2559         }
2560
2561         /**
2562          * Get an aliased field name
2563          * e.g. fieldName AS newFieldName
2564          *
2565          * @param string $name Field name
2566          * @param string|bool $alias Alias (optional)
2567          * @return string SQL name for aliased field. Will not alias a field to its own name
2568          */
2569         protected function fieldNameWithAlias( $name, $alias = false ) {
2570                 if ( !$alias || (string)$alias === (string)$name ) {
2571                         return $name;
2572                 } else {
2573                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
2574                 }
2575         }
2576
2577         /**
2578          * Gets an array of aliased field names
2579          *
2580          * @param array $fields [ [alias] => field ]
2581          * @return string[] See fieldNameWithAlias()
2582          */
2583         protected function fieldNamesWithAlias( $fields ) {
2584                 $retval = [];
2585                 foreach ( $fields as $alias => $field ) {
2586                         if ( is_numeric( $alias ) ) {
2587                                 $alias = $field;
2588                         }
2589                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2590                 }
2591
2592                 return $retval;
2593         }
2594
2595         /**
2596          * Get the aliased table name clause for a FROM clause
2597          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2598          *
2599          * @param array $tables ( [alias] => table )
2600          * @param array $use_index Same as for select()
2601          * @param array $ignore_index Same as for select()
2602          * @param array $join_conds Same as for select()
2603          * @return string
2604          */
2605         protected function tableNamesWithIndexClauseOrJOIN(
2606                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2607         ) {
2608                 $ret = [];
2609                 $retJOIN = [];
2610                 $use_index = (array)$use_index;
2611                 $ignore_index = (array)$ignore_index;
2612                 $join_conds = (array)$join_conds;
2613
2614                 foreach ( $tables as $alias => $table ) {
2615                         if ( !is_string( $alias ) ) {
2616                                 // No alias? Set it equal to the table name
2617                                 $alias = $table;
2618                         }
2619
2620                         if ( is_array( $table ) ) {
2621                                 // A parenthesized group
2622                                 if ( count( $table ) > 1 ) {
2623                                         $joinedTable = '(' .
2624                                                 $this->tableNamesWithIndexClauseOrJOIN(
2625                                                         $table, $use_index, $ignore_index, $join_conds ) . ')';
2626                                 } else {
2627                                         // Degenerate case
2628                                         $innerTable = reset( $table );
2629                                         $innerAlias = key( $table );
2630                                         $joinedTable = $this->tableNameWithAlias(
2631                                                 $innerTable,
2632                                                 is_string( $innerAlias ) ? $innerAlias : $innerTable
2633                                         );
2634                                 }
2635                         } else {
2636                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2637                         }
2638
2639                         // Is there a JOIN clause for this table?
2640                         if ( isset( $join_conds[$alias] ) ) {
2641                                 list( $joinType, $conds ) = $join_conds[$alias];
2642                                 $tableClause = $joinType;
2643                                 $tableClause .= ' ' . $joinedTable;
2644                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2645                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2646                                         if ( $use != '' ) {
2647                                                 $tableClause .= ' ' . $use;
2648                                         }
2649                                 }
2650                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2651                                         $ignore = $this->ignoreIndexClause(
2652                                                 implode( ',', (array)$ignore_index[$alias] ) );
2653                                         if ( $ignore != '' ) {
2654                                                 $tableClause .= ' ' . $ignore;
2655                                         }
2656                                 }
2657                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2658                                 if ( $on != '' ) {
2659                                         $tableClause .= ' ON (' . $on . ')';
2660                                 }
2661
2662                                 $retJOIN[] = $tableClause;
2663                         } elseif ( isset( $use_index[$alias] ) ) {
2664                                 // Is there an INDEX clause for this table?
2665                                 $tableClause = $joinedTable;
2666                                 $tableClause .= ' ' . $this->useIndexClause(
2667                                                 implode( ',', (array)$use_index[$alias] )
2668                                         );
2669
2670                                 $ret[] = $tableClause;
2671                         } elseif ( isset( $ignore_index[$alias] ) ) {
2672                                 // Is there an INDEX clause for this table?
2673                                 $tableClause = $joinedTable;
2674                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2675                                                 implode( ',', (array)$ignore_index[$alias] )
2676                                         );
2677
2678                                 $ret[] = $tableClause;
2679                         } else {
2680                                 $tableClause = $joinedTable;
2681
2682                                 $ret[] = $tableClause;
2683                         }
2684                 }
2685
2686                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2687                 $implicitJoins = $ret ? implode( ',', $ret ) : "";
2688                 $explicitJoins = $retJOIN ? implode( ' ', $retJOIN ) : "";
2689
2690                 // Compile our final table clause
2691                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2692         }
2693
2694         /**
2695          * Allows for index remapping in queries where this is not consistent across DBMS
2696          *
2697          * @param string $index
2698          * @return string
2699          */
2700         protected function indexName( $index ) {
2701                 return $this->indexAliases[$index] ?? $index;
2702         }
2703
2704         public function addQuotes( $s ) {
2705                 if ( $s instanceof Blob ) {
2706                         $s = $s->fetch();
2707                 }
2708                 if ( $s === null ) {
2709                         return 'NULL';
2710                 } elseif ( is_bool( $s ) ) {
2711                         return (int)$s;
2712                 } else {
2713                         # This will also quote numeric values. This should be harmless,
2714                         # and protects against weird problems that occur when they really
2715                         # _are_ strings such as article titles and string->number->string
2716                         # conversion is not 1:1.
2717                         return "'" . $this->strencode( $s ) . "'";
2718                 }
2719         }
2720
2721         public function addIdentifierQuotes( $s ) {
2722                 return '"' . str_replace( '"', '""', $s ) . '"';
2723         }
2724
2725         /**
2726          * Returns if the given identifier looks quoted or not according to
2727          * the database convention for quoting identifiers .
2728          *
2729          * @note Do not use this to determine if untrusted input is safe.
2730          *   A malicious user can trick this function.
2731          * @param string $name
2732          * @return bool
2733          */
2734         public function isQuotedIdentifier( $name ) {
2735                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2736         }
2737
2738         /**
2739          * @param string $s
2740          * @param string $escapeChar
2741          * @return string
2742          */
2743         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2744                 return str_replace( [ $escapeChar, '%', '_' ],
2745                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2746                         $s );
2747         }
2748
2749         public function buildLike() {
2750                 $params = func_get_args();
2751
2752                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2753                         $params = $params[0];
2754                 }
2755
2756                 $s = '';
2757
2758                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2759                 // may escape backslashes, creating problems of double escaping. The `
2760                 // character has good cross-DBMS compatibility, avoiding special operators
2761                 // in MS SQL like ^ and %
2762                 $escapeChar = '`';
2763
2764                 foreach ( $params as $value ) {
2765                         if ( $value instanceof LikeMatch ) {
2766                                 $s .= $value->toString();
2767                         } else {
2768                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2769                         }
2770                 }
2771
2772                 return ' LIKE ' .
2773                         $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2774         }
2775
2776         public function anyChar() {
2777                 return new LikeMatch( '_' );
2778         }
2779
2780         public function anyString() {
2781                 return new LikeMatch( '%' );
2782         }
2783
2784         public function nextSequenceValue( $seqName ) {
2785                 return null;
2786         }
2787
2788         /**
2789          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2790          * is only needed because a) MySQL must be as efficient as possible due to
2791          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2792          * which index to pick. Anyway, other databases might have different
2793          * indexes on a given table. So don't bother overriding this unless you're
2794          * MySQL.
2795          * @param string $index
2796          * @return string
2797          */
2798         public function useIndexClause( $index ) {
2799                 return '';
2800         }
2801
2802         /**
2803          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2804          * is only needed because a) MySQL must be as efficient as possible due to
2805          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2806          * which index to pick. Anyway, other databases might have different
2807          * indexes on a given table. So don't bother overriding this unless you're
2808          * MySQL.
2809          * @param string $index
2810          * @return string
2811          */
2812         public function ignoreIndexClause( $index ) {
2813                 return '';
2814         }
2815
2816         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2817                 if ( count( $rows ) == 0 ) {
2818                         return;
2819                 }
2820
2821                 $uniqueIndexes = (array)$uniqueIndexes;
2822                 // Single row case
2823                 if ( !is_array( reset( $rows ) ) ) {
2824                         $rows = [ $rows ];
2825                 }
2826
2827                 try {
2828                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2829                         $affectedRowCount = 0;
2830                         foreach ( $rows as $row ) {
2831                                 // Delete rows which collide with this one
2832                                 $indexWhereClauses = [];
2833                                 foreach ( $uniqueIndexes as $index ) {
2834                                         $indexColumns = (array)$index;
2835                                         $indexRowValues = array_intersect_key( $row, array_flip( $indexColumns ) );
2836                                         if ( count( $indexRowValues ) != count( $indexColumns ) ) {
2837                                                 throw new DBUnexpectedError(
2838                                                         $this,
2839                                                         'New record does not provide all values for unique key (' .
2840                                                         implode( ', ', $indexColumns ) . ')'
2841                                                 );
2842                                         } elseif ( in_array( null, $indexRowValues, true ) ) {
2843                                                 throw new DBUnexpectedError(
2844                                                         $this,
2845                                                         'New record has a null value for unique key (' .
2846                                                         implode( ', ', $indexColumns ) . ')'
2847                                                 );
2848                                         }
2849                                         $indexWhereClauses[] = $this->makeList( $indexRowValues, LIST_AND );
2850                                 }
2851
2852                                 if ( $indexWhereClauses ) {
2853                                         $this->delete( $table, $this->makeList( $indexWhereClauses, LIST_OR ), $fname );
2854                                         $affectedRowCount += $this->affectedRows();
2855                                 }
2856
2857                                 // Now insert the row
2858                                 $this->insert( $table, $row, $fname );
2859                                 $affectedRowCount += $this->affectedRows();
2860                         }
2861                         $this->endAtomic( $fname );
2862                         $this->affectedRowCount = $affectedRowCount;
2863                 } catch ( Exception $e ) {
2864                         $this->cancelAtomic( $fname );
2865                         throw $e;
2866                 }
2867         }
2868
2869         /**
2870          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2871          * statement.
2872          *
2873          * @param string $table Table name
2874          * @param array|string $rows Row(s) to insert
2875          * @param string $fname Caller function name
2876          */
2877         protected function nativeReplace( $table, $rows, $fname ) {
2878                 $table = $this->tableName( $table );
2879
2880                 # Single row case
2881                 if ( !is_array( reset( $rows ) ) ) {
2882                         $rows = [ $rows ];
2883                 }
2884
2885                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2886                 $first = true;
2887
2888                 foreach ( $rows as $row ) {
2889                         if ( $first ) {
2890                                 $first = false;
2891                         } else {
2892                                 $sql .= ',';
2893                         }
2894
2895                         $sql .= '(' . $this->makeList( $row ) . ')';
2896                 }
2897
2898                 $this->query( $sql, $fname );
2899         }
2900
2901         public function upsert( $table, array $rows, $uniqueIndexes, array $set,
2902                 $fname = __METHOD__
2903         ) {
2904                 if ( $rows === [] ) {
2905                         return true; // nothing to do
2906                 }
2907
2908                 $uniqueIndexes = (array)$uniqueIndexes;
2909                 if ( !is_array( reset( $rows ) ) ) {
2910                         $rows = [ $rows ];
2911                 }
2912
2913                 if ( count( $uniqueIndexes ) ) {
2914                         $clauses = []; // list WHERE clauses that each identify a single row
2915                         foreach ( $rows as $row ) {
2916                                 foreach ( $uniqueIndexes as $index ) {
2917                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2918                                         $rowKey = []; // unique key to this row
2919                                         foreach ( $index as $column ) {
2920                                                 $rowKey[$column] = $row[$column];
2921                                         }
2922                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2923                                 }
2924                         }
2925                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2926                 } else {
2927                         $where = false;
2928                 }
2929
2930                 $affectedRowCount = 0;
2931                 try {
2932                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2933                         # Update any existing conflicting row(s)
2934                         if ( $where !== false ) {
2935                                 $this->update( $table, $set, $where, $fname );
2936                                 $affectedRowCount += $this->affectedRows();
2937                         }
2938                         # Now insert any non-conflicting row(s)
2939                         $this->insert( $table, $rows, $fname, [ 'IGNORE' ] );
2940                         $affectedRowCount += $this->affectedRows();
2941                         $this->endAtomic( $fname );
2942                         $this->affectedRowCount = $affectedRowCount;
2943                 } catch ( Exception $e ) {
2944                         $this->cancelAtomic( $fname );
2945                         throw $e;
2946                 }
2947
2948                 return true;
2949         }
2950
2951         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2952                 $fname = __METHOD__
2953         ) {
2954                 if ( !$conds ) {
2955                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2956                 }
2957
2958                 $delTable = $this->tableName( $delTable );
2959                 $joinTable = $this->tableName( $joinTable );
2960                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2961                 if ( $conds != '*' ) {
2962                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2963                 }
2964                 $sql .= ')';
2965
2966                 $this->query( $sql, $fname );
2967         }
2968
2969         public function textFieldSize( $table, $field ) {
2970                 $table = $this->tableName( $table );
2971                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2972                 $res = $this->query( $sql, __METHOD__ );
2973                 $row = $this->fetchObject( $res );
2974
2975                 $m = [];
2976
2977                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2978                         $size = $m[1];
2979                 } else {
2980                         $size = -1;
2981                 }
2982
2983                 return $size;
2984         }
2985
2986         public function delete( $table, $conds, $fname = __METHOD__ ) {
2987                 if ( !$conds ) {
2988                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2989                 }
2990
2991                 $table = $this->tableName( $table );
2992                 $sql = "DELETE FROM $table";
2993
2994                 if ( $conds != '*' ) {
2995                         if ( is_array( $conds ) ) {
2996                                 $conds = $this->makeList( $conds, self::LIST_AND );
2997                         }
2998                         $sql .= ' WHERE ' . $conds;
2999                 }
3000
3001                 $this->query( $sql, $fname );
3002
3003                 return true;
3004         }
3005
3006         final public function insertSelect(
3007                 $destTable, $srcTable, $varMap, $conds,
3008                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
3009         ) {
3010                 static $hints = [ 'NO_AUTO_COLUMNS' ];
3011
3012                 $insertOptions = (array)$insertOptions;
3013                 $selectOptions = (array)$selectOptions;
3014
3015                 if ( $this->cliMode && $this->isInsertSelectSafe( $insertOptions, $selectOptions ) ) {
3016                         // For massive migrations with downtime, we don't want to select everything
3017                         // into memory and OOM, so do all this native on the server side if possible.
3018                         $this->nativeInsertSelect(
3019                                 $destTable,
3020                                 $srcTable,
3021                                 $varMap,
3022                                 $conds,
3023                                 $fname,
3024                                 array_diff( $insertOptions, $hints ),
3025                                 $selectOptions,
3026                                 $selectJoinConds
3027                         );
3028                 } else {
3029                         $this->nonNativeInsertSelect(
3030                                 $destTable,
3031                                 $srcTable,
3032                                 $varMap,
3033                                 $conds,
3034                                 $fname,
3035                                 array_diff( $insertOptions, $hints ),
3036                                 $selectOptions,
3037                                 $selectJoinConds
3038                         );
3039                 }
3040
3041                 return true;
3042         }
3043
3044         /**
3045          * @param array $insertOptions INSERT options
3046          * @param array $selectOptions SELECT options
3047          * @return bool Whether an INSERT SELECT with these options will be replication safe
3048          * @since 1.31
3049          */
3050         protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
3051                 return true;
3052         }
3053
3054         /**
3055          * Implementation of insertSelect() based on select() and insert()
3056          *
3057          * @see IDatabase::insertSelect()
3058          * @since 1.30
3059          * @param string $destTable
3060          * @param string|array $srcTable
3061          * @param array $varMap
3062          * @param array $conds
3063          * @param string $fname
3064          * @param array $insertOptions
3065          * @param array $selectOptions
3066          * @param array $selectJoinConds
3067          */
3068         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
3069                 $fname = __METHOD__,
3070                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
3071         ) {
3072                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
3073                 // on only the master (without needing row-based-replication). It also makes it easy to
3074                 // know how big the INSERT is going to be.
3075                 $fields = [];
3076                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
3077                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
3078                 }
3079                 $selectOptions[] = 'FOR UPDATE';
3080                 $res = $this->select(
3081                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
3082                 );
3083                 if ( !$res ) {
3084                         return;
3085                 }
3086
3087                 try {
3088                         $affectedRowCount = 0;
3089                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
3090                         $rows = [];
3091                         $ok = true;
3092                         foreach ( $res as $row ) {
3093                                 $rows[] = (array)$row;
3094
3095                                 // Avoid inserts that are too huge
3096                                 if ( count( $rows ) >= $this->nonNativeInsertSelectBatchSize ) {
3097                                         $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
3098                                         if ( !$ok ) {
3099                                                 break;
3100                                         }
3101                                         $affectedRowCount += $this->affectedRows();
3102                                         $rows = [];
3103                                 }
3104                         }
3105                         if ( $rows && $ok ) {
3106                                 $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
3107                                 if ( $ok ) {
3108                                         $affectedRowCount += $this->affectedRows();
3109                                 }
3110                         }
3111                         if ( $ok ) {
3112                                 $this->endAtomic( $fname );
3113                                 $this->affectedRowCount = $affectedRowCount;
3114                         } else {
3115                                 $this->cancelAtomic( $fname );
3116                         }
3117                 } catch ( Exception $e ) {
3118                         $this->cancelAtomic( $fname );
3119                         throw $e;
3120                 }
3121         }
3122
3123         /**
3124          * Native server-side implementation of insertSelect() for situations where
3125          * we don't want to select everything into memory
3126          *
3127          * @see IDatabase::insertSelect()
3128          * @param string $destTable
3129          * @param string|array $srcTable
3130          * @param array $varMap
3131          * @param array $conds
3132          * @param string $fname
3133          * @param array $insertOptions
3134          * @param array $selectOptions
3135          * @param array $selectJoinConds
3136          */
3137         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
3138                 $fname = __METHOD__,
3139                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
3140         ) {
3141                 $destTable = $this->tableName( $destTable );
3142
3143                 if ( !is_array( $insertOptions ) ) {
3144                         $insertOptions = [ $insertOptions ];
3145                 }
3146
3147                 $insertOptions = $this->makeInsertOptions( $insertOptions );
3148
3149                 $selectSql = $this->selectSQLText(
3150                         $srcTable,
3151                         array_values( $varMap ),
3152                         $conds,
3153                         $fname,
3154                         $selectOptions,
3155                         $selectJoinConds
3156                 );
3157
3158                 $sql = "INSERT $insertOptions" .
3159                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
3160                         $selectSql;
3161
3162                 $this->query( $sql, $fname );
3163         }
3164
3165         /**
3166          * Construct a LIMIT query with optional offset. This is used for query
3167          * pages. The SQL should be adjusted so that only the first $limit rows
3168          * are returned. If $offset is provided as well, then the first $offset
3169          * rows should be discarded, and the next $limit rows should be returned.
3170          * If the result of the query is not ordered, then the rows to be returned
3171          * are theoretically arbitrary.
3172          *
3173          * $sql is expected to be a SELECT, if that makes a difference.
3174          *
3175          * The version provided by default works in MySQL and SQLite. It will very
3176          * likely need to be overridden for most other DBMSes.
3177          *
3178          * @param string $sql SQL query we will append the limit too
3179          * @param int $limit The SQL limit
3180          * @param int|bool $offset The SQL offset (default false)
3181          * @throws DBUnexpectedError
3182          * @return string
3183          */
3184         public function limitResult( $sql, $limit, $offset = false ) {
3185                 if ( !is_numeric( $limit ) ) {
3186                         throw new DBUnexpectedError( $this,
3187                                 "Invalid non-numeric limit passed to limitResult()\n" );
3188                 }
3189
3190                 return "$sql LIMIT "
3191                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
3192                 . "{$limit} ";
3193         }
3194
3195         public function unionSupportsOrderAndLimit() {
3196                 return true; // True for almost every DB supported
3197         }
3198
3199         public function unionQueries( $sqls, $all ) {
3200                 $glue = $all ? ') UNION ALL (' : ') UNION (';
3201
3202                 return '(' . implode( $glue, $sqls ) . ')';
3203         }
3204
3205         public function unionConditionPermutations(
3206                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
3207                 $options = [], $join_conds = []
3208         ) {
3209                 // First, build the Cartesian product of $permute_conds
3210                 $conds = [ [] ];
3211                 foreach ( $permute_conds as $field => $values ) {
3212                         if ( !$values ) {
3213                                 // Skip empty $values
3214                                 continue;
3215                         }
3216                         $values = array_unique( $values ); // For sanity
3217                         $newConds = [];
3218                         foreach ( $conds as $cond ) {
3219                                 foreach ( $values as $value ) {
3220                                         $cond[$field] = $value;
3221                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
3222                                 }
3223                         }
3224                         $conds = $newConds;
3225                 }
3226
3227                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
3228
3229                 // If there's just one condition and no subordering, hand off to
3230                 // selectSQLText directly.
3231                 if ( count( $conds ) === 1 &&
3232                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
3233                 ) {
3234                         return $this->selectSQLText(
3235                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
3236                         );
3237                 }
3238
3239                 // Otherwise, we need to pull out the order and limit to apply after
3240                 // the union. Then build the SQL queries for each set of conditions in
3241                 // $conds. Then union them together (using UNION ALL, because the
3242                 // product *should* already be distinct).
3243                 $orderBy = $this->makeOrderBy( $options );
3244                 $limit = $options['LIMIT'] ?? null;
3245                 $offset = $options['OFFSET'] ?? false;
3246                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
3247                 if ( !$this->unionSupportsOrderAndLimit() ) {
3248                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
3249                 } else {
3250                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
3251                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
3252                         }
3253                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
3254                                 // We need to increase the limit by the offset rather than
3255                                 // using the offset directly, otherwise it'll skip incorrectly
3256                                 // in the subqueries.
3257                                 $options['LIMIT'] = $limit + $offset;
3258                                 unset( $options['OFFSET'] );
3259                         }
3260                 }
3261
3262                 $sqls = [];
3263                 foreach ( $conds as $cond ) {
3264                         $sqls[] = $this->selectSQLText(
3265                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
3266                         );
3267                 }
3268                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
3269                 if ( $limit !== null ) {
3270                         $sql = $this->limitResult( $sql, $limit, $offset );
3271                 }
3272
3273                 return $sql;
3274         }
3275
3276         public function conditional( $cond, $trueVal, $falseVal ) {
3277                 if ( is_array( $cond ) ) {
3278                         $cond = $this->makeList( $cond, self::LIST_AND );
3279                 }
3280
3281                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
3282         }
3283
3284         public function strreplace( $orig, $old, $new ) {
3285                 return "REPLACE({$orig}, {$old}, {$new})";
3286         }
3287
3288         public function getServerUptime() {
3289                 return 0;
3290         }
3291
3292         public function wasDeadlock() {
3293                 return false;
3294         }
3295
3296         public function wasLockTimeout() {
3297                 return false;
3298         }
3299
3300         public function wasConnectionLoss() {
3301                 return $this->wasConnectionError( $this->lastErrno() );
3302         }
3303
3304         public function wasReadOnlyError() {
3305                 return false;
3306         }
3307
3308         public function wasErrorReissuable() {
3309                 return (
3310                         $this->wasDeadlock() ||
3311                         $this->wasLockTimeout() ||
3312                         $this->wasConnectionLoss()
3313                 );
3314         }
3315
3316         /**
3317          * Do not use this method outside of Database/DBError classes
3318          *
3319          * @param int|string $errno
3320          * @return bool Whether the given query error was a connection drop
3321          */
3322         public function wasConnectionError( $errno ) {
3323                 return false;
3324         }
3325
3326         /**
3327          * @return bool Whether it is known that the last query error only caused statement rollback
3328          * @note This is for backwards compatibility for callers catching DBError exceptions in
3329          *   order to ignore problems like duplicate key errors or foriegn key violations
3330          * @since 1.31
3331          */
3332         protected function wasKnownStatementRollbackError() {
3333                 return false; // don't know; it could have caused a transaction rollback
3334         }
3335
3336         public function deadlockLoop() {
3337                 $args = func_get_args();
3338                 $function = array_shift( $args );
3339                 $tries = self::DEADLOCK_TRIES;
3340
3341                 $this->begin( __METHOD__ );
3342
3343                 $retVal = null;
3344                 /** @var Exception $e */
3345                 $e = null;
3346                 do {
3347                         try {
3348                                 $retVal = $function( ...$args );
3349                                 break;
3350                         } catch ( DBQueryError $e ) {
3351                                 if ( $this->wasDeadlock() ) {
3352                                         // Retry after a randomized delay
3353                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3354                                 } else {
3355                                         // Throw the error back up
3356                                         throw $e;
3357                                 }
3358                         }
3359                 } while ( --$tries > 0 );
3360
3361                 if ( $tries <= 0 ) {
3362                         // Too many deadlocks; give up
3363                         $this->rollback( __METHOD__ );
3364                         throw $e;
3365                 } else {
3366                         $this->commit( __METHOD__ );
3367
3368                         return $retVal;
3369                 }
3370         }
3371
3372         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3373                 # Real waits are implemented in the subclass.
3374                 return 0;
3375         }
3376
3377         public function getReplicaPos() {
3378                 # Stub
3379                 return false;
3380         }
3381
3382         public function getMasterPos() {
3383                 # Stub
3384                 return false;
3385         }
3386
3387         public function serverIsReadOnly() {
3388                 return false;
3389         }
3390
3391         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
3392                 if ( !$this->trxLevel ) {
3393                         throw new DBUnexpectedError( $this, "No transaction is active." );
3394                 }
3395                 $this->trxEndCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3396         }
3397
3398         final public function onTransactionCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
3399                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3400                         // Start an implicit transaction similar to how query() does
3401                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3402                         $this->trxAutomatic = true;
3403                 }
3404
3405                 $this->trxIdleCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3406                 if ( !$this->trxLevel ) {
3407                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
3408                 }
3409         }
3410
3411         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
3412                 $this->onTransactionCommitOrIdle( $callback, $fname );
3413         }
3414
3415         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
3416                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3417                         // Start an implicit transaction similar to how query() does
3418                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3419                         $this->trxAutomatic = true;
3420                 }
3421
3422                 if ( $this->trxLevel ) {
3423                         $this->trxPreCommitCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3424                 } else {
3425                         // No transaction is active nor will start implicitly, so make one for this callback
3426                         $this->startAtomic( __METHOD__, self::ATOMIC_CANCELABLE );
3427                         try {
3428                                 $callback( $this );
3429                                 $this->endAtomic( __METHOD__ );
3430                         } catch ( Exception $e ) {
3431                                 $this->cancelAtomic( __METHOD__ );
3432                                 throw $e;
3433                         }
3434                 }
3435         }
3436
3437         /**
3438          * @return AtomicSectionIdentifier|null ID of the topmost atomic section level
3439          */
3440         private function currentAtomicSectionId() {
3441                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3442                         $levelInfo = end( $this->trxAtomicLevels );
3443
3444                         return $levelInfo[1];
3445                 }
3446
3447                 return null;
3448         }
3449
3450         /**
3451          * @param AtomicSectionIdentifier $old
3452          * @param AtomicSectionIdentifier $new
3453          */
3454         private function reassignCallbacksForSection(
3455                 AtomicSectionIdentifier $old, AtomicSectionIdentifier $new
3456         ) {
3457                 foreach ( $this->trxPreCommitCallbacks as $key => $info ) {
3458                         if ( $info[2] === $old ) {
3459                                 $this->trxPreCommitCallbacks[$key][2] = $new;
3460                         }
3461                 }
3462                 foreach ( $this->trxIdleCallbacks as $key => $info ) {
3463                         if ( $info[2] === $old ) {
3464                                 $this->trxIdleCallbacks[$key][2] = $new;
3465                         }
3466                 }
3467                 foreach ( $this->trxEndCallbacks as $key => $info ) {
3468                         if ( $info[2] === $old ) {
3469                                 $this->trxEndCallbacks[$key][2] = $new;
3470                         }
3471                 }
3472         }
3473
3474         /**
3475          * @param AtomicSectionIdentifier[] $sectionIds ID of an actual savepoint
3476          * @throws UnexpectedValueException
3477          */
3478         private function modifyCallbacksForCancel( array $sectionIds ) {
3479                 // Cancel the "on commit" callbacks owned by this savepoint
3480                 $this->trxIdleCallbacks = array_filter(
3481                         $this->trxIdleCallbacks,
3482                         function ( $entry ) use ( $sectionIds ) {
3483                                 return !in_array( $entry[2], $sectionIds, true );
3484                         }
3485                 );
3486                 $this->trxPreCommitCallbacks = array_filter(
3487                         $this->trxPreCommitCallbacks,
3488                         function ( $entry ) use ( $sectionIds ) {
3489                                 return !in_array( $entry[2], $sectionIds, true );
3490                         }
3491                 );
3492                 // Make "on resolution" callbacks owned by this savepoint to perceive a rollback
3493                 foreach ( $this->trxEndCallbacks as $key => $entry ) {
3494                         if ( in_array( $entry[2], $sectionIds, true ) ) {
3495                                 $callback = $entry[0];
3496                                 $this->trxEndCallbacks[$key][0] = function () use ( $callback ) {
3497                                         return $callback( self::TRIGGER_ROLLBACK, $this );
3498                                 };
3499                         }
3500                 }
3501         }
3502
3503         final public function setTransactionListener( $name, callable $callback = null ) {
3504                 if ( $callback ) {
3505                         $this->trxRecurringCallbacks[$name] = $callback;
3506                 } else {
3507                         unset( $this->trxRecurringCallbacks[$name] );
3508                 }
3509         }
3510
3511         /**
3512          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
3513          *
3514          * This method should not be used outside of Database/LoadBalancer
3515          *
3516          * @param bool $suppress
3517          * @since 1.28
3518          */
3519         final public function setTrxEndCallbackSuppression( $suppress ) {
3520                 $this->trxEndCallbacksSuppressed = $suppress;
3521         }
3522
3523         /**
3524          * Actually consume and run any "on transaction idle/resolution" callbacks.
3525          *
3526          * This method should not be used outside of Database/LoadBalancer
3527          *
3528          * @param int $trigger IDatabase::TRIGGER_* constant
3529          * @return int Number of callbacks attempted
3530          * @since 1.20
3531          * @throws Exception
3532          */
3533         public function runOnTransactionIdleCallbacks( $trigger ) {
3534                 if ( $this->trxLevel ) { // sanity
3535                         throw new DBUnexpectedError( $this, __METHOD__ . ': a transaction is still open.' );
3536                 }
3537
3538                 if ( $this->trxEndCallbacksSuppressed ) {
3539                         return 0;
3540                 }
3541
3542                 $count = 0;
3543                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
3544                 /** @var Exception $e */
3545                 $e = null; // first exception
3546                 do { // callbacks may add callbacks :)
3547                         $callbacks = array_merge(
3548                                 $this->trxIdleCallbacks,
3549                                 $this->trxEndCallbacks // include "transaction resolution" callbacks
3550                         );
3551                         $this->trxIdleCallbacks = []; // consumed (and recursion guard)
3552                         $this->trxEndCallbacks = []; // consumed (recursion guard)
3553                         foreach ( $callbacks as $callback ) {
3554                                 ++$count;
3555                                 list( $phpCallback ) = $callback;
3556                                 $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
3557                                 try {
3558                                         call_user_func( $phpCallback, $trigger, $this );
3559                                 } catch ( Exception $ex ) {
3560                                         call_user_func( $this->errorLogger, $ex );
3561                                         $e = $e ?: $ex;
3562                                         // Some callbacks may use startAtomic/endAtomic, so make sure
3563                                         // their transactions are ended so other callbacks don't fail
3564                                         if ( $this->trxLevel() ) {
3565                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
3566                                         }
3567                                 } finally {
3568                                         if ( $autoTrx ) {
3569                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
3570                                         } else {
3571                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
3572                                         }
3573                                 }
3574                         }
3575                 } while ( count( $this->trxIdleCallbacks ) );
3576
3577                 if ( $e instanceof Exception ) {
3578                         throw $e; // re-throw any first exception
3579                 }
3580
3581                 return $count;
3582         }
3583
3584         /**
3585          * Actually consume and run any "on transaction pre-commit" callbacks.
3586          *
3587          * This method should not be used outside of Database/LoadBalancer
3588          *
3589          * @since 1.22
3590          * @return int Number of callbacks attempted
3591          * @throws Exception
3592          */
3593         public function runOnTransactionPreCommitCallbacks() {
3594                 $count = 0;
3595
3596                 $e = null; // first exception
3597                 do { // callbacks may add callbacks :)
3598                         $callbacks = $this->trxPreCommitCallbacks;
3599                         $this->trxPreCommitCallbacks = []; // consumed (and recursion guard)
3600                         foreach ( $callbacks as $callback ) {
3601                                 try {
3602                                         ++$count;
3603                                         list( $phpCallback ) = $callback;
3604                                         $phpCallback( $this );
3605                                 } catch ( Exception $ex ) {
3606                                         ( $this->errorLogger )( $ex );
3607                                         $e = $e ?: $ex;
3608                                 }
3609                         }
3610                 } while ( count( $this->trxPreCommitCallbacks ) );
3611
3612                 if ( $e instanceof Exception ) {
3613                         throw $e; // re-throw any first exception
3614                 }
3615
3616                 return $count;
3617         }
3618
3619         /**
3620          * Actually run any "transaction listener" callbacks.
3621          *
3622          * This method should not be used outside of Database/LoadBalancer
3623          *
3624          * @param int $trigger IDatabase::TRIGGER_* constant
3625          * @throws Exception
3626          * @since 1.20
3627          */
3628         public function runTransactionListenerCallbacks( $trigger ) {
3629                 if ( $this->trxEndCallbacksSuppressed ) {
3630                         return;
3631                 }
3632
3633                 /** @var Exception $e */
3634                 $e = null; // first exception
3635
3636                 foreach ( $this->trxRecurringCallbacks as $phpCallback ) {
3637                         try {
3638                                 $phpCallback( $trigger, $this );
3639                         } catch ( Exception $ex ) {
3640                                 ( $this->errorLogger )( $ex );
3641                                 $e = $e ?: $ex;
3642                         }
3643                 }
3644
3645                 if ( $e instanceof Exception ) {
3646                         throw $e; // re-throw any first exception
3647                 }
3648         }
3649
3650         /**
3651          * Create a savepoint
3652          *
3653          * This is used internally to implement atomic sections. It should not be
3654          * used otherwise.
3655          *
3656          * @since 1.31
3657          * @param string $identifier Identifier for the savepoint
3658          * @param string $fname Calling function name
3659          */
3660         protected function doSavepoint( $identifier, $fname ) {
3661                 $this->query( 'SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3662         }
3663
3664         /**
3665          * Release a savepoint
3666          *
3667          * This is used internally to implement atomic sections. It should not be
3668          * used otherwise.
3669          *
3670          * @since 1.31
3671          * @param string $identifier Identifier for the savepoint
3672          * @param string $fname Calling function name
3673          */
3674         protected function doReleaseSavepoint( $identifier, $fname ) {
3675                 $this->query( 'RELEASE SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3676         }
3677
3678         /**
3679          * Rollback to a savepoint
3680          *
3681          * This is used internally to implement atomic sections. It should not be
3682          * used otherwise.
3683          *
3684          * @since 1.31
3685          * @param string $identifier Identifier for the savepoint
3686          * @param string $fname Calling function name
3687          */
3688         protected function doRollbackToSavepoint( $identifier, $fname ) {
3689                 $this->query( 'ROLLBACK TO SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3690         }
3691
3692         /**
3693          * @param string $fname
3694          * @return string
3695          */
3696         private function nextSavepointId( $fname ) {
3697                 $savepointId = self::$SAVEPOINT_PREFIX . ++$this->trxAtomicCounter;
3698                 if ( strlen( $savepointId ) > 30 ) {
3699                         // 30 == Oracle's identifier length limit (pre 12c)
3700                         // With a 22 character prefix, that puts the highest number at 99999999.
3701                         throw new DBUnexpectedError(
3702                                 $this,
3703                                 'There have been an excessively large number of atomic sections in a transaction'
3704                                 . " started by $this->trxFname (at $fname)"
3705                         );
3706                 }
3707
3708                 return $savepointId;
3709         }
3710
3711         final public function startAtomic(
3712                 $fname = __METHOD__, $cancelable = self::ATOMIC_NOT_CANCELABLE
3713         ) {
3714                 $savepointId = $cancelable === self::ATOMIC_CANCELABLE ? self::$NOT_APPLICABLE : null;
3715
3716                 if ( !$this->trxLevel ) {
3717                         $this->begin( $fname, self::TRANSACTION_INTERNAL ); // sets trxAutomatic
3718                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
3719                         // in all changes being in one transaction to keep requests transactional.
3720                         if ( $this->getFlag( self::DBO_TRX ) ) {
3721                                 // Since writes could happen in between the topmost atomic sections as part
3722                                 // of the transaction, those sections will need savepoints.
3723                                 $savepointId = $this->nextSavepointId( $fname );
3724                                 $this->doSavepoint( $savepointId, $fname );
3725                         } else {
3726                                 $this->trxAutomaticAtomic = true;
3727                         }
3728                 } elseif ( $cancelable === self::ATOMIC_CANCELABLE ) {
3729                         $savepointId = $this->nextSavepointId( $fname );
3730                         $this->doSavepoint( $savepointId, $fname );
3731                 }
3732
3733                 $sectionId = new AtomicSectionIdentifier;
3734                 $this->trxAtomicLevels[] = [ $fname, $sectionId, $savepointId ];
3735                 $this->queryLogger->debug( 'startAtomic: entering level ' .
3736                         ( count( $this->trxAtomicLevels ) - 1 ) . " ($fname)" );
3737
3738                 return $sectionId;
3739         }
3740
3741         final public function endAtomic( $fname = __METHOD__ ) {
3742                 if ( !$this->trxLevel || !$this->trxAtomicLevels ) {
3743                         throw new DBUnexpectedError( $this, "No atomic section is open (got $fname)." );
3744                 }
3745
3746                 // Check if the current section matches $fname
3747                 $pos = count( $this->trxAtomicLevels ) - 1;
3748                 list( $savedFname, $sectionId, $savepointId ) = $this->trxAtomicLevels[$pos];
3749                 $this->queryLogger->debug( "endAtomic: leaving level $pos ($fname)" );
3750
3751                 if ( $savedFname !== $fname ) {
3752                         throw new DBUnexpectedError(
3753                                 $this,
3754                                 "Invalid atomic section ended (got $fname but expected $savedFname)."
3755                         );
3756                 }
3757
3758                 // Remove the last section (no need to re-index the array)
3759                 array_pop( $this->trxAtomicLevels );
3760
3761                 if ( !$this->trxAtomicLevels && $this->trxAutomaticAtomic ) {
3762                         $this->commit( $fname, self::FLUSHING_INTERNAL );
3763                 } elseif ( $savepointId !== null && $savepointId !== self::$NOT_APPLICABLE ) {
3764                         $this->doReleaseSavepoint( $savepointId, $fname );
3765                 }
3766
3767                 // Hoist callback ownership for callbacks in the section that just ended;
3768                 // all callbacks should have an owner that is present in trxAtomicLevels.
3769                 $currentSectionId = $this->currentAtomicSectionId();
3770                 if ( $currentSectionId ) {
3771                         $this->reassignCallbacksForSection( $sectionId, $currentSectionId );
3772                 }
3773         }
3774
3775         final public function cancelAtomic(
3776                 $fname = __METHOD__, AtomicSectionIdentifier $sectionId = null
3777         ) {
3778                 if ( !$this->trxLevel || !$this->trxAtomicLevels ) {
3779                         throw new DBUnexpectedError( $this, "No atomic section is open (got $fname)." );
3780                 }
3781
3782                 $excisedFnames = [];
3783                 if ( $sectionId !== null ) {
3784                         // Find the (last) section with the given $sectionId
3785                         $pos = -1;
3786                         foreach ( $this->trxAtomicLevels as $i => list( $asFname, $asId, $spId ) ) {
3787                                 if ( $asId === $sectionId ) {
3788                                         $pos = $i;
3789                                 }
3790                         }
3791                         if ( $pos < 0 ) {
3792                                 throw new DBUnexpectedError( $this, "Atomic section not found (for $fname)" );
3793                         }
3794                         // Remove all descendant sections and re-index the array
3795                         $excisedIds = [];
3796                         $len = count( $this->trxAtomicLevels );
3797                         for ( $i = $pos + 1; $i < $len; ++$i ) {
3798                                 $excisedFnames[] = $this->trxAtomicLevels[$i][0];
3799                                 $excisedIds[] = $this->trxAtomicLevels[$i][1];
3800                         }
3801                         $this->trxAtomicLevels = array_slice( $this->trxAtomicLevels, 0, $pos + 1 );
3802                         $this->modifyCallbacksForCancel( $excisedIds );
3803                 }
3804
3805                 // Check if the current section matches $fname
3806                 $pos = count( $this->trxAtomicLevels ) - 1;
3807                 list( $savedFname, $savedSectionId, $savepointId ) = $this->trxAtomicLevels[$pos];
3808
3809                 if ( $excisedFnames ) {
3810                         $this->queryLogger->debug( "cancelAtomic: canceling level $pos ($savedFname) " .
3811                                 "and descendants " . implode( ', ', $excisedFnames ) );
3812                 } else {
3813                         $this->queryLogger->debug( "cancelAtomic: canceling level $pos ($savedFname)" );
3814                 }
3815
3816                 if ( $savedFname !== $fname ) {
3817                         throw new DBUnexpectedError(
3818                                 $this,
3819                                 "Invalid atomic section ended (got $fname but expected $savedFname)."
3820                         );
3821                 }
3822
3823                 // Remove the last section (no need to re-index the array)
3824                 array_pop( $this->trxAtomicLevels );
3825                 $this->modifyCallbacksForCancel( [ $savedSectionId ] );
3826
3827                 if ( $savepointId !== null ) {
3828                         // Rollback the transaction to the state just before this atomic section
3829                         if ( $savepointId === self::$NOT_APPLICABLE ) {
3830                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
3831                         } else {
3832                                 $this->doRollbackToSavepoint( $savepointId, $fname );
3833                                 $this->trxStatus = self::STATUS_TRX_OK; // no exception; recovered
3834                                 $this->trxStatusIgnoredCause = null;
3835                         }
3836                 } elseif ( $this->trxStatus > self::STATUS_TRX_ERROR ) {
3837                         // Put the transaction into an error state if it's not already in one
3838                         $this->trxStatus = self::STATUS_TRX_ERROR;
3839                         $this->trxStatusCause = new DBUnexpectedError(
3840                                 $this,
3841                                 "Uncancelable atomic section canceled (got $fname)."
3842                         );
3843                 }
3844
3845                 $this->affectedRowCount = 0; // for the sake of consistency
3846         }
3847
3848         final public function doAtomicSection(
3849                 $fname, callable $callback, $cancelable = self::ATOMIC_NOT_CANCELABLE
3850         ) {
3851                 $sectionId = $this->startAtomic( $fname, $cancelable );
3852                 try {
3853                         $res = $callback( $this, $fname );
3854                 } catch ( Exception $e ) {
3855                         $this->cancelAtomic( $fname, $sectionId );
3856
3857                         throw $e;
3858                 }
3859                 $this->endAtomic( $fname );
3860
3861                 return $res;
3862         }
3863
3864         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
3865                 static $modes = [ self::TRANSACTION_EXPLICIT, self::TRANSACTION_INTERNAL ];
3866                 if ( !in_array( $mode, $modes, true ) ) {
3867                         throw new DBUnexpectedError( $this, "$fname: invalid mode parameter '$mode'." );
3868                 }
3869
3870                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
3871                 if ( $this->trxLevel ) {
3872                         if ( $this->trxAtomicLevels ) {
3873                                 $levels = $this->flatAtomicSectionList();
3874                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
3875                                 throw new DBUnexpectedError( $this, $msg );
3876                         } elseif ( !$this->trxAutomatic ) {
3877                                 $msg = "$fname: Explicit transaction already active (from {$this->trxFname}).";
3878                                 throw new DBUnexpectedError( $this, $msg );
3879                         } else {
3880                                 $msg = "$fname: Implicit transaction already active (from {$this->trxFname}).";
3881                                 throw new DBUnexpectedError( $this, $msg );
3882                         }
3883                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
3884                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
3885                         throw new DBUnexpectedError( $this, $msg );
3886                 }
3887
3888                 $this->assertHasConnectionHandle();
3889
3890                 $this->doBegin( $fname );
3891                 $this->trxStatus = self::STATUS_TRX_OK;
3892                 $this->trxStatusIgnoredCause = null;
3893                 $this->trxAtomicCounter = 0;
3894                 $this->trxTimestamp = microtime( true );
3895                 $this->trxFname = $fname;
3896                 $this->trxDoneWrites = false;
3897                 $this->trxAutomaticAtomic = false;
3898                 $this->trxAtomicLevels = [];
3899                 $this->trxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
3900                 $this->trxWriteDuration = 0.0;
3901                 $this->trxWriteQueryCount = 0;
3902                 $this->trxWriteAffectedRows = 0;
3903                 $this->trxWriteAdjDuration = 0.0;
3904                 $this->trxWriteAdjQueryCount = 0;
3905                 $this->trxWriteCallers = [];
3906                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
3907                 // Get an estimate of the replication lag before any such queries.
3908                 $this->trxReplicaLag = null; // clear cached value first
3909                 $this->trxReplicaLag = $this->getApproximateLagStatus()['lag'];
3910                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
3911                 // caller will think its OK to muck around with the transaction just because startAtomic()
3912                 // has not yet completed (e.g. setting trxAtomicLevels).
3913                 $this->trxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
3914         }
3915
3916         /**
3917          * Issues the BEGIN command to the database server.
3918          *
3919          * @see Database::begin()
3920          * @param string $fname
3921          */
3922         protected function doBegin( $fname ) {
3923                 $this->query( 'BEGIN', $fname );
3924                 $this->trxLevel = 1;
3925         }
3926
3927         final public function commit( $fname = __METHOD__, $flush = self::FLUSHING_ONE ) {
3928                 static $modes = [ self::FLUSHING_ONE, self::FLUSHING_ALL_PEERS, self::FLUSHING_INTERNAL ];
3929                 if ( !in_array( $flush, $modes, true ) ) {
3930                         throw new DBUnexpectedError( $this, "$fname: invalid flush parameter '$flush'." );
3931                 }
3932
3933                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3934                         // There are still atomic sections open; this cannot be ignored
3935                         $levels = $this->flatAtomicSectionList();
3936                         throw new DBUnexpectedError(
3937                                 $this,
3938                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3939                         );
3940                 }
3941
3942                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3943                         if ( !$this->trxLevel ) {
3944                                 return; // nothing to do
3945                         } elseif ( !$this->trxAutomatic ) {
3946                                 throw new DBUnexpectedError(
3947                                         $this,
3948                                         "$fname: Flushing an explicit transaction, getting out of sync."
3949                                 );
3950                         }
3951                 } else {
3952                         if ( !$this->trxLevel ) {
3953                                 $this->queryLogger->error(
3954                                         "$fname: No transaction to commit, something got out of sync." );
3955                                 return; // nothing to do
3956                         } elseif ( $this->trxAutomatic ) {
3957                                 throw new DBUnexpectedError(
3958                                         $this,
3959                                         "$fname: Expected mass commit of all peer transactions (DBO_TRX set)."
3960                                 );
3961                         }
3962                 }
3963
3964                 $this->assertHasConnectionHandle();
3965
3966                 $this->runOnTransactionPreCommitCallbacks();
3967
3968                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3969                 $this->doCommit( $fname );
3970                 $this->trxStatus = self::STATUS_TRX_NONE;
3971
3972                 if ( $this->trxDoneWrites ) {
3973                         $this->lastWriteTime = microtime( true );
3974                         $this->trxProfiler->transactionWritingOut(
3975                                 $this->server,
3976                                 $this->getDomainID(),
3977                                 $this->trxShortId,
3978                                 $writeTime,
3979                                 $this->trxWriteAffectedRows
3980                         );
3981                 }
3982
3983                 // With FLUSHING_ALL_PEERS, callbacks will be explicitly run later
3984                 if ( $flush !== self::FLUSHING_ALL_PEERS ) {
3985                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3986                         $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3987                 }
3988         }
3989
3990         /**
3991          * Issues the COMMIT command to the database server.
3992          *
3993          * @see Database::commit()
3994          * @param string $fname
3995          */
3996         protected function doCommit( $fname ) {
3997                 if ( $this->trxLevel ) {
3998                         $this->query( 'COMMIT', $fname );
3999                         $this->trxLevel = 0;
4000                 }
4001         }
4002
4003         final public function rollback( $fname = __METHOD__, $flush = '' ) {
4004                 $trxActive = $this->trxLevel;
4005
4006                 if ( $flush !== self::FLUSHING_INTERNAL && $flush !== self::FLUSHING_ALL_PEERS ) {
4007                         if ( $this->getFlag( self::DBO_TRX ) ) {
4008                                 throw new DBUnexpectedError(
4009                                         $this,
4010                                         "$fname: Expected mass rollback of all peer transactions (DBO_TRX set)."
4011                                 );
4012                         }
4013                 }
4014
4015                 if ( $trxActive ) {
4016                         $this->assertHasConnectionHandle();
4017
4018                         $this->doRollback( $fname );
4019                         $this->trxStatus = self::STATUS_TRX_NONE;
4020                         $this->trxAtomicLevels = [];
4021                         // Estimate the RTT via a query now that trxStatus is OK
4022                         $writeTime = $this->pingAndCalculateLastTrxApplyTime();
4023
4024                         if ( $this->trxDoneWrites ) {
4025                                 $this->trxProfiler->transactionWritingOut(
4026                                         $this->server,
4027                                         $this->getDomainID(),
4028                                         $this->trxShortId,
4029                                         $writeTime,
4030                                         $this->trxWriteAffectedRows
4031                                 );
4032                         }
4033                 }
4034
4035                 // Clear any commit-dependant callbacks. They might even be present
4036                 // only due to transaction rounds, with no SQL transaction being active
4037                 $this->trxIdleCallbacks = [];
4038                 $this->trxPreCommitCallbacks = [];
4039
4040                 // With FLUSHING_ALL_PEERS, callbacks will be explicitly run later
4041                 if ( $trxActive && $flush !== self::FLUSHING_ALL_PEERS ) {
4042                         try {
4043                                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
4044                         } catch ( Exception $e ) {
4045                                 // already logged; finish and let LoadBalancer move on during mass-rollback
4046                         }
4047                         try {
4048                                 $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
4049                         } catch ( Exception $e ) {
4050                                 // already logged; let LoadBalancer move on during mass-rollback
4051                         }
4052
4053                         $this->affectedRowCount = 0; // for the sake of consistency
4054                 }
4055         }
4056
4057         /**
4058          * Issues the ROLLBACK command to the database server.
4059          *
4060          * @see Database::rollback()
4061          * @param string $fname
4062          */
4063         protected function doRollback( $fname ) {
4064                 if ( $this->trxLevel ) {
4065                         # Disconnects cause rollback anyway, so ignore those errors
4066                         $ignoreErrors = true;
4067                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
4068                         $this->trxLevel = 0;
4069                 }
4070         }
4071
4072         public function flushSnapshot( $fname = __METHOD__ ) {
4073                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
4074                         // This only flushes transactions to clear snapshots, not to write data
4075                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
4076                         throw new DBUnexpectedError(
4077                                 $this,
4078                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
4079                         );
4080                 }
4081
4082                 $this->commit( $fname, self::FLUSHING_INTERNAL );
4083         }
4084
4085         public function explicitTrxActive() {
4086                 return $this->trxLevel && ( $this->trxAtomicLevels || !$this->trxAutomatic );
4087         }
4088
4089         public function duplicateTableStructure(
4090                 $oldName, $newName, $temporary = false, $fname = __METHOD__
4091         ) {
4092                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4093         }
4094
4095         public function listTables( $prefix = null, $fname = __METHOD__ ) {
4096                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4097         }
4098
4099         public function listViews( $prefix = null, $fname = __METHOD__ ) {
4100                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4101         }
4102
4103         public function timestamp( $ts = 0 ) {
4104                 $t = new ConvertibleTimestamp( $ts );
4105                 // Let errors bubble up to avoid putting garbage in the DB
4106                 return $t->getTimestamp( TS_MW );
4107         }
4108
4109         public function timestampOrNull( $ts = null ) {
4110                 if ( is_null( $ts ) ) {
4111                         return null;
4112                 } else {
4113                         return $this->timestamp( $ts );
4114                 }
4115         }
4116
4117         public function affectedRows() {
4118                 return ( $this->affectedRowCount === null )
4119                         ? $this->fetchAffectedRowCount() // default to driver value
4120                         : $this->affectedRowCount;
4121         }
4122
4123         /**
4124          * @return int Number of retrieved rows according to the driver
4125          */
4126         abstract protected function fetchAffectedRowCount();
4127
4128         /**
4129          * Take the result from a query, and wrap it in a ResultWrapper if
4130          * necessary. Boolean values are passed through as is, to indicate success
4131          * of write queries or failure.
4132          *
4133          * Once upon a time, Database::query() returned a bare MySQL result
4134          * resource, and it was necessary to call this function to convert it to
4135          * a wrapper. Nowadays, raw database objects are never exposed to external
4136          * callers, so this is unnecessary in external code.
4137          *
4138          * @param bool|ResultWrapper|resource $result
4139          * @return bool|ResultWrapper
4140          */
4141         protected function resultObject( $result ) {
4142                 if ( !$result ) {
4143                         return false;
4144                 } elseif ( $result instanceof ResultWrapper ) {
4145                         return $result;
4146                 } elseif ( $result === true ) {
4147                         // Successful write query
4148                         return $result;
4149                 } else {
4150                         return new ResultWrapper( $this, $result );
4151                 }
4152         }
4153
4154         public function ping( &$rtt = null ) {
4155                 // Avoid hitting the server if it was hit recently
4156                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
4157                         if ( !func_num_args() || $this->rttEstimate > 0 ) {
4158                                 $rtt = $this->rttEstimate;
4159                                 return true; // don't care about $rtt
4160                         }
4161                 }
4162
4163                 // This will reconnect if possible or return false if not
4164                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
4165                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
4166                 $this->restoreFlags( self::RESTORE_PRIOR );
4167
4168                 if ( $ok ) {
4169                         $rtt = $this->rttEstimate;
4170                 }
4171
4172                 return $ok;
4173         }
4174
4175         /**
4176          * Close any existing (dead) database connection and open a new connection
4177          *
4178          * @param string $fname
4179          * @return bool True if new connection is opened successfully, false if error
4180          */
4181         protected function replaceLostConnection( $fname ) {
4182                 $this->closeConnection();
4183                 $this->opened = false;
4184                 $this->conn = false;
4185                 try {
4186                         $this->open(
4187                                 $this->server,
4188                                 $this->user,
4189                                 $this->password,
4190                                 $this->getDBname(),
4191                                 $this->dbSchema(),
4192                                 $this->tablePrefix()
4193                         );
4194                         $this->lastPing = microtime( true );
4195                         $ok = true;
4196
4197                         $this->connLogger->warning(
4198                                 $fname . ': lost connection to {dbserver}; reconnected',
4199                                 [
4200                                         'dbserver' => $this->getServer(),
4201                                         'trace' => ( new RuntimeException() )->getTraceAsString()
4202                                 ]
4203                         );
4204                 } catch ( DBConnectionError $e ) {
4205                         $ok = false;
4206
4207                         $this->connLogger->error(
4208                                 $fname . ': lost connection to {dbserver} permanently',
4209                                 [ 'dbserver' => $this->getServer() ]
4210                         );
4211                 }
4212
4213                 $this->handleSessionLoss();
4214
4215                 return $ok;
4216         }
4217
4218         public function getSessionLagStatus() {
4219                 return $this->getRecordedTransactionLagStatus() ?: $this->getApproximateLagStatus();
4220         }
4221
4222         /**
4223          * Get the replica DB lag when the current transaction started
4224          *
4225          * This is useful when transactions might use snapshot isolation
4226          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
4227          * is this lag plus transaction duration. If they don't, it is still
4228          * safe to be pessimistic. This returns null if there is no transaction.
4229          *
4230          * This returns null if the lag status for this transaction was not yet recorded.
4231          *
4232          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
4233          * @since 1.27
4234          */
4235         final protected function getRecordedTransactionLagStatus() {
4236                 return ( $this->trxLevel && $this->trxReplicaLag !== null )
4237                         ? [ 'lag' => $this->trxReplicaLag, 'since' => $this->trxTimestamp() ]
4238                         : null;
4239         }
4240
4241         /**
4242          * Get a replica DB lag estimate for this server
4243          *
4244          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
4245          * @since 1.27
4246          */
4247         protected function getApproximateLagStatus() {
4248                 return [
4249                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
4250                         'since' => microtime( true )
4251                 ];
4252         }
4253
4254         /**
4255          * Merge the result of getSessionLagStatus() for several DBs
4256          * using the most pessimistic values to estimate the lag of
4257          * any data derived from them in combination
4258          *
4259          * This is information is useful for caching modules
4260          *
4261          * @see WANObjectCache::set()
4262          * @see WANObjectCache::getWithSetCallback()
4263          *
4264          * @param IDatabase $db1
4265          * @param IDatabase|null $db2 [optional]
4266          * @return array Map of values:
4267          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
4268          *   - since: oldest UNIX timestamp of any of the DB lag estimates
4269          *   - pending: whether any of the DBs have uncommitted changes
4270          * @throws DBError
4271          * @since 1.27
4272          */
4273         public static function getCacheSetOptions( IDatabase $db1, IDatabase $db2 = null ) {
4274                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
4275                 foreach ( func_get_args() as $db ) {
4276                         /** @var IDatabase $db */
4277                         $status = $db->getSessionLagStatus();
4278                         if ( $status['lag'] === false ) {
4279                                 $res['lag'] = false;
4280                         } elseif ( $res['lag'] !== false ) {
4281                                 $res['lag'] = max( $res['lag'], $status['lag'] );
4282                         }
4283                         $res['since'] = min( $res['since'], $status['since'] );
4284                         $res['pending'] = $res['pending'] ?: $db->writesPending();
4285                 }
4286
4287                 return $res;
4288         }
4289
4290         public function getLag() {
4291                 return 0;
4292         }
4293
4294         public function maxListLen() {
4295                 return 0;
4296         }
4297
4298         public function encodeBlob( $b ) {
4299                 return $b;
4300         }
4301
4302         public function decodeBlob( $b ) {
4303                 if ( $b instanceof Blob ) {
4304                         $b = $b->fetch();
4305                 }
4306                 return $b;
4307         }
4308
4309         public function setSessionOptions( array $options ) {
4310         }
4311
4312         public function sourceFile(
4313                 $filename,
4314                 callable $lineCallback = null,
4315                 callable $resultCallback = null,
4316                 $fname = false,
4317                 callable $inputCallback = null
4318         ) {
4319                 Wikimedia\suppressWarnings();
4320                 $fp = fopen( $filename, 'r' );
4321                 Wikimedia\restoreWarnings();
4322
4323                 if ( $fp === false ) {
4324                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
4325                 }
4326
4327                 if ( !$fname ) {
4328                         $fname = __METHOD__ . "( $filename )";
4329                 }
4330
4331                 try {
4332                         $error = $this->sourceStream(
4333                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
4334                 } catch ( Exception $e ) {
4335                         fclose( $fp );
4336                         throw $e;
4337                 }
4338
4339                 fclose( $fp );
4340
4341                 return $error;
4342         }
4343
4344         public function setSchemaVars( $vars ) {
4345                 $this->schemaVars = $vars;
4346         }
4347
4348         public function sourceStream(
4349                 $fp,
4350                 callable $lineCallback = null,
4351                 callable $resultCallback = null,
4352                 $fname = __METHOD__,
4353                 callable $inputCallback = null
4354         ) {
4355                 $delimiterReset = new ScopedCallback(
4356                         function ( $delimiter ) {
4357                                 $this->delimiter = $delimiter;
4358                         },
4359                         [ $this->delimiter ]
4360                 );
4361                 $cmd = '';
4362
4363                 while ( !feof( $fp ) ) {
4364                         if ( $lineCallback ) {
4365                                 call_user_func( $lineCallback );
4366                         }
4367
4368                         $line = trim( fgets( $fp ) );
4369
4370                         if ( $line == '' ) {
4371                                 continue;
4372                         }
4373
4374                         if ( $line[0] == '-' && $line[1] == '-' ) {
4375                                 continue;
4376                         }
4377
4378                         if ( $cmd != '' ) {
4379                                 $cmd .= ' ';
4380                         }
4381
4382                         $done = $this->streamStatementEnd( $cmd, $line );
4383
4384                         $cmd .= "$line\n";
4385
4386                         if ( $done || feof( $fp ) ) {
4387                                 $cmd = $this->replaceVars( $cmd );
4388
4389                                 if ( $inputCallback ) {
4390                                         $callbackResult = $inputCallback( $cmd );
4391
4392                                         if ( is_string( $callbackResult ) || !$callbackResult ) {
4393                                                 $cmd = $callbackResult;
4394                                         }
4395                                 }
4396
4397                                 if ( $cmd ) {
4398                                         $res = $this->query( $cmd, $fname );
4399
4400                                         if ( $resultCallback ) {
4401                                                 $resultCallback( $res, $this );
4402                                         }
4403
4404                                         if ( $res === false ) {
4405                                                 $err = $this->lastError();
4406
4407                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
4408                                         }
4409                                 }
4410                                 $cmd = '';
4411                         }
4412                 }
4413
4414                 ScopedCallback::consume( $delimiterReset );
4415                 return true;
4416         }
4417
4418         /**
4419          * Called by sourceStream() to check if we've reached a statement end
4420          *
4421          * @param string &$sql SQL assembled so far
4422          * @param string &$newLine New line about to be added to $sql
4423          * @return bool Whether $newLine contains end of the statement
4424          */
4425         public function streamStatementEnd( &$sql, &$newLine ) {
4426                 if ( $this->delimiter ) {
4427                         $prev = $newLine;
4428                         $newLine = preg_replace(
4429                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
4430                         if ( $newLine != $prev ) {
4431                                 return true;
4432                         }
4433                 }
4434
4435                 return false;
4436         }
4437
4438         /**
4439          * Database independent variable replacement. Replaces a set of variables
4440          * in an SQL statement with their contents as given by $this->getSchemaVars().
4441          *
4442          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
4443          *
4444          * - '{$var}' should be used for text and is passed through the database's
4445          *   addQuotes method.
4446          * - `{$var}` should be used for identifiers (e.g. table and database names).
4447          *   It is passed through the database's addIdentifierQuotes method which
4448          *   can be overridden if the database uses something other than backticks.
4449          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
4450          *   database's tableName method.
4451          * - / *i* / passes the name that follows through the database's indexName method.
4452          * - In all other cases, / *$var* / is left unencoded. Except for table options,
4453          *   its use should be avoided. In 1.24 and older, string encoding was applied.
4454          *
4455          * @param string $ins SQL statement to replace variables in
4456          * @return string The new SQL statement with variables replaced
4457          */
4458         protected function replaceVars( $ins ) {
4459                 $vars = $this->getSchemaVars();
4460                 return preg_replace_callback(
4461                         '!
4462                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
4463                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
4464                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
4465                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
4466                         !x',
4467                         function ( $m ) use ( $vars ) {
4468                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
4469                                 // check for both nonexistent keys *and* the empty string.
4470                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
4471                                         if ( $m[1] === 'i' ) {
4472                                                 return $this->indexName( $m[2] );
4473                                         } else {
4474                                                 return $this->tableName( $m[2] );
4475                                         }
4476                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
4477                                         return $this->addQuotes( $vars[$m[3]] );
4478                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
4479                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
4480                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
4481                                         return $vars[$m[5]];
4482                                 } else {
4483                                         return $m[0];
4484                                 }
4485                         },
4486                         $ins
4487                 );
4488         }
4489
4490         /**
4491          * Get schema variables. If none have been set via setSchemaVars(), then
4492          * use some defaults from the current object.
4493          *
4494          * @return array
4495          */
4496         protected function getSchemaVars() {
4497                 if ( $this->schemaVars ) {
4498                         return $this->schemaVars;
4499                 } else {
4500                         return $this->getDefaultSchemaVars();
4501                 }
4502         }
4503
4504         /**
4505          * Get schema variables to use if none have been set via setSchemaVars().
4506          *
4507          * Override this in derived classes to provide variables for tables.sql
4508          * and SQL patch files.
4509          *
4510          * @return array
4511          */
4512         protected function getDefaultSchemaVars() {
4513                 return [];
4514         }
4515
4516         public function lockIsFree( $lockName, $method ) {
4517                 // RDBMs methods for checking named locks may or may not count this thread itself.
4518                 // In MySQL, IS_FREE_LOCK() returns 0 if the thread already has the lock. This is
4519                 // the behavior choosen by the interface for this method.
4520                 return !isset( $this->namedLocksHeld[$lockName] );
4521         }
4522
4523         public function lock( $lockName, $method, $timeout = 5 ) {
4524                 $this->namedLocksHeld[$lockName] = 1;
4525
4526                 return true;
4527         }
4528
4529         public function unlock( $lockName, $method ) {
4530                 unset( $this->namedLocksHeld[$lockName] );
4531
4532                 return true;
4533         }
4534
4535         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
4536                 if ( $this->writesOrCallbacksPending() ) {
4537                         // This only flushes transactions to clear snapshots, not to write data
4538                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
4539                         throw new DBUnexpectedError(
4540                                 $this,
4541                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
4542                         );
4543                 }
4544
4545                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
4546                         return null;
4547                 }
4548
4549                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
4550                         if ( $this->trxLevel() ) {
4551                                 // There is a good chance an exception was thrown, causing any early return
4552                                 // from the caller. Let any error handler get a chance to issue rollback().
4553                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
4554                                 $this->onTransactionResolution(
4555                                         function () use ( $lockKey, $fname ) {
4556                                                 $this->unlock( $lockKey, $fname );
4557                                         },
4558                                         $fname
4559                                 );
4560                         } else {
4561                                 $this->unlock( $lockKey, $fname );
4562                         }
4563                 } );
4564
4565                 $this->commit( $fname, self::FLUSHING_INTERNAL );
4566
4567                 return $unlocker;
4568         }
4569
4570         public function namedLocksEnqueue() {
4571                 return false;
4572         }
4573
4574         public function tableLocksHaveTransactionScope() {
4575                 return true;
4576         }
4577
4578         final public function lockTables( array $read, array $write, $method ) {
4579                 if ( $this->writesOrCallbacksPending() ) {
4580                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
4581                 }
4582
4583                 if ( $this->tableLocksHaveTransactionScope() ) {
4584                         $this->startAtomic( $method );
4585                 }
4586
4587                 return $this->doLockTables( $read, $write, $method );
4588         }
4589
4590         /**
4591          * Helper function for lockTables() that handles the actual table locking
4592          *
4593          * @param array $read Array of tables to lock for read access
4594          * @param array $write Array of tables to lock for write access
4595          * @param string $method Name of caller
4596          * @return true
4597          */
4598         protected function doLockTables( array $read, array $write, $method ) {
4599                 return true;
4600         }
4601
4602         final public function unlockTables( $method ) {
4603                 if ( $this->tableLocksHaveTransactionScope() ) {
4604                         $this->endAtomic( $method );
4605
4606                         return true; // locks released on COMMIT/ROLLBACK
4607                 }
4608
4609                 return $this->doUnlockTables( $method );
4610         }
4611
4612         /**
4613          * Helper function for unlockTables() that handles the actual table unlocking
4614          *
4615          * @param string $method Name of caller
4616          * @return true
4617          */
4618         protected function doUnlockTables( $method ) {
4619                 return true;
4620         }
4621
4622         /**
4623          * Delete a table
4624          * @param string $tableName
4625          * @param string $fName
4626          * @return bool|ResultWrapper
4627          * @since 1.18
4628          */
4629         public function dropTable( $tableName, $fName = __METHOD__ ) {
4630                 if ( !$this->tableExists( $tableName, $fName ) ) {
4631                         return false;
4632                 }
4633                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
4634
4635                 return $this->query( $sql, $fName );
4636         }
4637
4638         public function getInfinity() {
4639                 return 'infinity';
4640         }
4641
4642         public function encodeExpiry( $expiry ) {
4643                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4644                         ? $this->getInfinity()
4645                         : $this->timestamp( $expiry );
4646         }
4647
4648         public function decodeExpiry( $expiry, $format = TS_MW ) {
4649                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
4650                         return 'infinity';
4651                 }
4652
4653                 return ConvertibleTimestamp::convert( $format, $expiry );
4654         }
4655
4656         public function setBigSelects( $value = true ) {
4657                 // no-op
4658         }
4659
4660         public function isReadOnly() {
4661                 return ( $this->getReadOnlyReason() !== false );
4662         }
4663
4664         /**
4665          * @return string|bool Reason this DB is read-only or false if it is not
4666          */
4667         protected function getReadOnlyReason() {
4668                 $reason = $this->getLBInfo( 'readOnlyReason' );
4669
4670                 return is_string( $reason ) ? $reason : false;
4671         }
4672
4673         public function setTableAliases( array $aliases ) {
4674                 $this->tableAliases = $aliases;
4675         }
4676
4677         public function setIndexAliases( array $aliases ) {
4678                 $this->indexAliases = $aliases;
4679         }
4680
4681         /**
4682          * Get the underlying binding connection handle
4683          *
4684          * Makes sure the connection resource is set (disconnects and ping() failure can unset it).
4685          * This catches broken callers than catch and ignore disconnection exceptions.
4686          * Unlike checking isOpen(), this is safe to call inside of open().
4687          *
4688          * @return mixed
4689          * @throws DBUnexpectedError
4690          * @since 1.26
4691          */
4692         protected function getBindingHandle() {
4693                 if ( !$this->conn ) {
4694                         throw new DBUnexpectedError(
4695                                 $this,
4696                                 'DB connection was already closed or the connection dropped.'
4697                         );
4698                 }
4699
4700                 return $this->conn;
4701         }
4702
4703         /**
4704          * @since 1.19
4705          * @return string
4706          */
4707         public function __toString() {
4708                 return (string)$this->conn;
4709         }
4710
4711         /**
4712          * Make sure that copies do not share the same client binding handle
4713          * @throws DBConnectionError
4714          */
4715         public function __clone() {
4716                 $this->connLogger->warning(
4717                         "Cloning " . static::class . " is not recommended; forking connection:\n" .
4718                         ( new RuntimeException() )->getTraceAsString()
4719                 );
4720
4721                 if ( $this->isOpen() ) {
4722                         // Open a new connection resource without messing with the old one
4723                         $this->opened = false;
4724                         $this->conn = false;
4725                         $this->trxEndCallbacks = []; // don't copy
4726                         $this->handleSessionLoss(); // no trx or locks anymore
4727                         $this->open(
4728                                 $this->server,
4729                                 $this->user,
4730                                 $this->password,
4731                                 $this->getDBname(),
4732                                 $this->dbSchema(),
4733                                 $this->tablePrefix()
4734                         );
4735                         $this->lastPing = microtime( true );
4736                 }
4737         }
4738
4739         /**
4740          * Called by serialize. Throw an exception when DB connection is serialized.
4741          * This causes problems on some database engines because the connection is
4742          * not restored on unserialize.
4743          */
4744         public function __sleep() {
4745                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
4746                         'the connection is not restored on wakeup.' );
4747         }
4748
4749         /**
4750          * Run a few simple sanity checks and close dangling connections
4751          */
4752         public function __destruct() {
4753                 if ( $this->trxLevel && $this->trxDoneWrites ) {
4754                         trigger_error( "Uncommitted DB writes (transaction from {$this->trxFname})." );
4755                 }
4756
4757                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
4758                 if ( $danglingWriters ) {
4759                         $fnames = implode( ', ', $danglingWriters );
4760                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
4761                 }
4762
4763                 if ( $this->conn ) {
4764                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
4765                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
4766                         Wikimedia\suppressWarnings();
4767                         $this->closeConnection();
4768                         Wikimedia\restoreWarnings();
4769                         $this->conn = false;
4770                         $this->opened = false;
4771                 }
4772         }
4773 }
4774
4775 /**
4776  * @deprecated since 1.28
4777  */
4778 class_alias( Database::class, 'DatabaseBase' );
4779
4780 /**
4781  * @deprecated since 1.29
4782  */
4783 class_alias( Database::class, 'Database' );