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 callable|null */
 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 = is_callable( $params['profiler'] ) ? $params['profiler'] : null;
 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 callback that takes a section name argument and returns
 412          *      a ScopedCallback instance that ends the profile section in its destructor.
 413          *      These will be called in query(), using a simplified version of the SQL that
 414          *      also includes the agent as a SQL comment.
 415          *   - trxProfiler: Optional TransactionProfiler instance.
 416          *   - errorLogger: Optional callback that takes an Exception and logs it.
 417          *   - deprecationLogger: Optional callback that takes a string and logs it.
 418          *   - cliMode: Whether to consider the execution context that of a CLI script.
 419          *   - agent: Optional name used to identify the end-user in query profiling/logging.
 420          *   - srvCache: Optional BagOStuff instance to an APC-style cache.
 421          *   - nonNativeInsertSelectBatchSize: Optional batch size for non-native INSERT SELECT emulation.
 422          * @param int $connect One of the class constants (NEW_CONNECTED, NEW_UNCONNECTED) [optional]
 423          * @return Database|null If the database driver or extension cannot be found
 424          * @throws InvalidArgumentException If the database driver or extension cannot be found
 425          * @since 1.18
 426          */
 427         final public static function factory( $dbType, $p = [], $connect = self::NEW_CONNECTED ) {
 428                 $class = self::getClass( $dbType, $p['driver'] ?? null );
 429
 430                 if ( class_exists( $class ) && is_subclass_of( $class, IDatabase::class ) ) {
 431                         // Resolve some defaults for b/c
 432                         $p['host'] = $p['host'] ?? false;
 433                         $p['user'] = $p['user'] ?? false;
 434                         $p['password'] = $p['password'] ?? false;
 435                         $p['dbname'] = $p['dbname'] ?? false;
 436                         $p['flags'] = $p['flags'] ?? 0;
 437                         $p['variables'] = $p['variables'] ?? [];
 438                         $p['tablePrefix'] = $p['tablePrefix'] ?? '';
 439                         $p['schema'] = $p['schema'] ?? null;
 440                         $p['cliMode'] = $p['cliMode'] ?? ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 441                         $p['agent'] = $p['agent'] ?? '';
 442                         if ( !isset( $p['connLogger'] ) ) {
 443                                 $p['connLogger'] = new NullLogger();
 444                         }
 445                         if ( !isset( $p['queryLogger'] ) ) {
 446                                 $p['queryLogger'] = new NullLogger();
 447                         }
 448                         $p['profiler'] = $p['profiler'] ?? null;
 449                         if ( !isset( $p['trxProfiler'] ) ) {
 450                                 $p['trxProfiler'] = new TransactionProfiler();
 451                         }
 452                         if ( !isset( $p['errorLogger'] ) ) {
 453                                 $p['errorLogger'] = function ( Exception $e ) {
 454                                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 455                                 };
 456                         }
 457                         if ( !isset( $p['deprecationLogger'] ) ) {
 458                                 $p['deprecationLogger'] = function ( $msg ) {
 459                                         trigger_error( $msg, E_USER_DEPRECATED );
 460                                 };
 461                         }
 462
 463                         /** @var Database $conn */
 464                         $conn = new $class( $p );
 465                         if ( $connect == self::NEW_CONNECTED ) {
 466                                 $conn->initConnection();
 467                         }
 468                 } else {
 469                         $conn = null;
 470                 }
 471
 472                 return $conn;
 473         }
 474
 475         /**
 476          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 477          * @param string|null $driver Optional name of a specific DB client driver
 478          * @return array Map of (Database::ATTRIBUTE_* constant => value) for all such constants
 479          * @throws InvalidArgumentException
 480          * @since 1.31
 481          */
 482         final public static function attributesFromType( $dbType, $driver = null ) {
 483                 static $defaults = [ self::ATTR_DB_LEVEL_LOCKING => false ];
 484
 485                 $class = self::getClass( $dbType, $driver );
 486
 487                 return call_user_func( [ $class, 'getAttributes' ] ) + $defaults;
 488         }
 489
 490         /**
 491          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 492          * @param string|null $driver Optional name of a specific DB client driver
 493          * @return string Database subclass name to use
 494          * @throws InvalidArgumentException
 495          */
 496         private static function getClass( $dbType, $driver = null ) {
 497                 // For database types with built-in support, the below maps type to IDatabase
 498                 // implementations. For types with multipe driver implementations (PHP extensions),
 499                 // an array can be used, keyed by extension name. In case of an array, the
 500                 // optional 'driver' parameter can be used to force a specific driver. Otherwise,
 501                 // we auto-detect the first available driver. For types without built-in support,
 502                 // an class named "Database<Type>" us used, eg. DatabaseFoo for type 'foo'.
 503                 static $builtinTypes = [
 504                         'mssql' => DatabaseMssql::class,
 505                         'mysql' => [ 'mysqli' => DatabaseMysqli::class ],
 506                         'sqlite' => DatabaseSqlite::class,
 507                         'postgres' => DatabasePostgres::class,
 508                 ];
 509
 510                 $dbType = strtolower( $dbType );
 511                 $class = false;
 512
 513                 if ( isset( $builtinTypes[$dbType] ) ) {
 514                         $possibleDrivers = $builtinTypes[$dbType];
 515                         if ( is_string( $possibleDrivers ) ) {
 516                                 $class = $possibleDrivers;
 517                         } else {
 518                                 if ( (string)$driver !== '' ) {
 519                                         if ( !isset( $possibleDrivers[$driver] ) ) {
 520                                                 throw new InvalidArgumentException( __METHOD__ .
 521                                                         " type '$dbType' does not support driver '{$driver}'" );
 522                                         } else {
 523                                                 $class = $possibleDrivers[$driver];
 524                                         }
 525                                 } else {
 526                                         foreach ( $possibleDrivers as $posDriver => $possibleClass ) {
 527                                                 if ( extension_loaded( $posDriver ) ) {
 528                                                         $class = $possibleClass;
 529                                                         break;
 530                                                 }
 531                                         }
 532                                 }
 533                         }
 534                 } else {
 535                         $class = 'Database' . ucfirst( $dbType );
 536                 }
 537
 538                 if ( $class === false ) {
 539                         throw new InvalidArgumentException( __METHOD__ .
 540                                 " no viable database extension found for type '$dbType'" );
 541                 }
 542
 543                 return $class;
 544         }
 545
 546         /**
 547          * @return array Map of (Database::ATTRIBUTE_* constant => value
 548          * @since 1.31
 549          */
 550         protected static function getAttributes() {
 551                 return [];
 552         }
 553
 554         /**
 555          * Set the PSR-3 logger interface to use for query logging. (The logger
 556          * interfaces for connection logging and error logging can be set with the
 557          * constructor.)
 558          *
 559          * @param LoggerInterface $logger
 560          */
 561         public function setLogger( LoggerInterface $logger ) {
 562                 $this->queryLogger = $logger;
 563         }
 564
 565         public function getServerInfo() {
 566                 return $this->getServerVersion();
 567         }
 568
 569         public function bufferResults( $buffer = null ) {
 570                 $res = !$this->getFlag( self::DBO_NOBUFFER );
 571                 if ( $buffer !== null ) {
 572                         $buffer
 573                                 ? $this->clearFlag( self::DBO_NOBUFFER )
 574                                 : $this->setFlag( self::DBO_NOBUFFER );
 575                 }
 576
 577                 return $res;
 578         }
 579
 580         public function trxLevel() {
 581                 return $this->trxLevel;
 582         }
 583
 584         public function trxTimestamp() {
 585                 return $this->trxLevel ? $this->trxTimestamp : null;
 586         }
 587
 588         /**
 589          * @return int One of the STATUS_TRX_* class constants
 590          * @since 1.31
 591          */
 592         public function trxStatus() {
 593                 return $this->trxStatus;
 594         }
 595
 596         public function tablePrefix( $prefix = null ) {
 597                 $old = $this->currentDomain->getTablePrefix();
 598                 if ( $prefix !== null ) {
 599                         $this->currentDomain = new DatabaseDomain(
 600                                 $this->currentDomain->getDatabase(),
 601                                 $this->currentDomain->getSchema(),
 602                                 $prefix
 603                         );
 604                 }
 605
 606                 return $old;
 607         }
 608
 609         public function dbSchema( $schema = null ) {
 610                 $old = $this->currentDomain->getSchema();
 611                 if ( $schema !== null ) {
 612                         $this->currentDomain = new DatabaseDomain(
 613                                 $this->currentDomain->getDatabase(),
 614                                 // DatabaseDomain uses null for unspecified schemas
 615                                 strlen( $schema ) ? $schema : null,
 616                                 $this->currentDomain->getTablePrefix()
 617                         );
 618                 }
 619
 620                 return (string)$old;
 621         }
 622
 623         /**
 624          * @return string Schema to use to qualify relations in queries
 625          */
 626         protected function relationSchemaQualifier() {
 627                 return $this->dbSchema();
 628         }
 629
 630         public function getLBInfo( $name = null ) {
 631                 if ( is_null( $name ) ) {
 632                         return $this->lbInfo;
 633                 } else {
 634                         if ( array_key_exists( $name, $this->lbInfo ) ) {
 635                                 return $this->lbInfo[$name];
 636                         } else {
 637                                 return null;
 638                         }
 639                 }
 640         }
 641
 642         public function setLBInfo( $name, $value = null ) {
 643                 if ( is_null( $value ) ) {
 644                         $this->lbInfo = $name;
 645                 } else {
 646                         $this->lbInfo[$name] = $value;
 647                 }
 648         }
 649
 650         public function setLazyMasterHandle( IDatabase $conn ) {
 651                 $this->lazyMasterHandle = $conn;
 652         }
 653
 654         /**
 655          * @return IDatabase|null
 656          * @see setLazyMasterHandle()
 657          * @since 1.27
 658          */
 659         protected function getLazyMasterHandle() {
 660                 return $this->lazyMasterHandle;
 661         }
 662
 663         public function implicitGroupby() {
 664                 return true;
 665         }
 666
 667         public function implicitOrderby() {
 668                 return true;
 669         }
 670
 671         public function lastQuery() {
 672                 return $this->lastQuery;
 673         }
 674
 675         public function doneWrites() {
 676                 return (bool)$this->lastWriteTime;
 677         }
 678
 679         public function lastDoneWrites() {
 680                 return $this->lastWriteTime ?: false;
 681         }
 682
 683         public function writesPending() {
 684                 return $this->trxLevel && $this->trxDoneWrites;
 685         }
 686
 687         public function writesOrCallbacksPending() {
 688                 return $this->trxLevel && (
 689                         $this->trxDoneWrites ||
 690                         $this->trxIdleCallbacks ||
 691                         $this->trxPreCommitCallbacks ||
 692                         $this->trxEndCallbacks
 693                 );
 694         }
 695
 696         public function preCommitCallbacksPending() {
 697                 return $this->trxLevel && $this->trxPreCommitCallbacks;
 698         }
 699
 700         /**
 701          * @return string|null
 702          */
 703         final protected function getTransactionRoundId() {
 704                 // If transaction round participation is enabled, see if one is active
 705                 if ( $this->getFlag( self::DBO_TRX ) ) {
 706                         $id = $this->getLBInfo( 'trxRoundId' );
 707
 708                         return is_string( $id ) ? $id : null;
 709                 }
 710
 711                 return null;
 712         }
 713
 714         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 715                 if ( !$this->trxLevel ) {
 716                         return false;
 717                 } elseif ( !$this->trxDoneWrites ) {
 718                         return 0.0;
 719                 }
 720
 721                 switch ( $type ) {
 722                         case self::ESTIMATE_DB_APPLY:
 723                                 return $this->pingAndCalculateLastTrxApplyTime();
 724                         default: // everything
 725                                 return $this->trxWriteDuration;
 726                 }
 727         }
 728
 729         /**
 730          * @return float Time to apply writes to replicas based on trxWrite* fields
 731          */
 732         private function pingAndCalculateLastTrxApplyTime() {
 733                 $this->ping( $rtt );
 734
 735                 $rttAdjTotal = $this->trxWriteAdjQueryCount * $rtt;
 736                 $applyTime = max( $this->trxWriteAdjDuration - $rttAdjTotal, 0 );
 737                 // For omitted queries, make them count as something at least
 738                 $omitted = $this->trxWriteQueryCount - $this->trxWriteAdjQueryCount;
 739                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 740
 741                 return $applyTime;
 742         }
 743
 744         public function pendingWriteCallers() {
 745                 return $this->trxLevel ? $this->trxWriteCallers : [];
 746         }
 747
 748         public function pendingWriteRowsAffected() {
 749                 return $this->trxWriteAffectedRows;
 750         }
 751
 752         /**
 753          * List the methods that have write queries or callbacks for the current transaction
 754          *
 755          * This method should not be used outside of Database/LoadBalancer
 756          *
 757          * @return string[]
 758          * @since 1.32
 759          */
 760         public function pendingWriteAndCallbackCallers() {
 761                 $fnames = $this->pendingWriteCallers();
 762                 foreach ( [
 763                         $this->trxIdleCallbacks,
 764                         $this->trxPreCommitCallbacks,
 765                         $this->trxEndCallbacks
 766                 ] as $callbacks ) {
 767                         foreach ( $callbacks as $callback ) {
 768                                 $fnames[] = $callback[1];
 769                         }
 770                 }
 771
 772                 return $fnames;
 773         }
 774
 775         /**
 776          * @return string
 777          */
 778         private function flatAtomicSectionList() {
 779                 return array_reduce( $this->trxAtomicLevels, function ( $accum, $v ) {
 780                         return $accum === null ? $v[0] : "$accum, " . $v[0];
 781                 } );
 782         }
 783
 784         public function isOpen() {
 785                 return $this->opened;
 786         }
 787
 788         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 789                 if ( ( $flag & self::DBO_IGNORE ) ) {
 790                         throw new UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 791                 }
 792
 793                 if ( $remember === self::REMEMBER_PRIOR ) {
 794                         array_push( $this->priorFlags, $this->flags );
 795                 }
 796                 $this->flags |= $flag;
 797         }
 798
 799         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 800                 if ( ( $flag & self::DBO_IGNORE ) ) {
 801                         throw new UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 802                 }
 803
 804                 if ( $remember === self::REMEMBER_PRIOR ) {
 805                         array_push( $this->priorFlags, $this->flags );
 806                 }
 807                 $this->flags &= ~$flag;
 808         }
 809
 810         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 811                 if ( !$this->priorFlags ) {
 812                         return;
 813                 }
 814
 815                 if ( $state === self::RESTORE_INITIAL ) {
 816                         $this->flags = reset( $this->priorFlags );
 817                         $this->priorFlags = [];
 818                 } else {
 819                         $this->flags = array_pop( $this->priorFlags );
 820                 }
 821         }
 822
 823         public function getFlag( $flag ) {
 824                 return (bool)( $this->flags & $flag );
 825         }
 826
 827         /**
 828          * @param string $name Class field name
 829          * @return mixed
 830          * @deprecated Since 1.28
 831          */
 832         public function getProperty( $name ) {
 833                 return $this->$name;
 834         }
 835
 836         public function getDomainID() {
 837                 return $this->currentDomain->getId();
 838         }
 839
 840         final public function getWikiID() {
 841                 return $this->getDomainID();
 842         }
 843
 844         /**
 845          * Get information about an index into an object
 846          * @param string $table Table name
 847          * @param string $index Index name
 848          * @param string $fname Calling function name
 849          * @return mixed Database-specific index description class or false if the index does not exist
 850          */
 851         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 852
 853         /**
 854          * Wrapper for addslashes()
 855          *
 856          * @param string $s String to be slashed.
 857          * @return string Slashed string.
 858          */
 859         abstract function strencode( $s );
 860
 861         /**
 862          * Set a custom error handler for logging errors during database connection
 863          */
 864         protected function installErrorHandler() {
 865                 $this->phpError = false;
 866                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 867                 set_error_handler( [ $this, 'connectionErrorLogger' ] );
 868         }
 869
 870         /**
 871          * Restore the previous error handler and return the last PHP error for this DB
 872          *
 873          * @return bool|string
 874          */
 875         protected function restoreErrorHandler() {
 876                 restore_error_handler();
 877                 if ( $this->htmlErrors !== false ) {
 878                         ini_set( 'html_errors', $this->htmlErrors );
 879                 }
 880
 881                 return $this->getLastPHPError();
 882         }
 883
 884         /**
 885          * @return string|bool Last PHP error for this DB (typically connection errors)
 886          */
 887         protected function getLastPHPError() {
 888                 if ( $this->phpError ) {
 889                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->phpError );
 890                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 891
 892                         return $error;
 893                 }
 894
 895                 return false;
 896         }
 897
 898         /**
 899          * Error handler for logging errors during database connection
 900          * This method should not be used outside of Database classes
 901          *
 902          * @param int $errno
 903          * @param string $errstr
 904          */
 905         public function connectionErrorLogger( $errno, $errstr ) {
 906                 $this->phpError = $errstr;
 907         }
 908
 909         /**
 910          * Create a log context to pass to PSR-3 logger functions.
 911          *
 912          * @param array $extras Additional data to add to context
 913          * @return array
 914          */
 915         protected function getLogContext( array $extras = [] ) {
 916                 return array_merge(
 917                         [
 918                                 'db_server' => $this->server,
 919                                 'db_name' => $this->getDBname(),
 920                                 'db_user' => $this->user,
 921                         ],
 922                         $extras
 923                 );
 924         }
 925
 926         final public function close() {
 927                 $exception = null; // error to throw after disconnecting
 928
 929                 $wasOpen = $this->opened;
 930                 // This should mostly do nothing if the connection is already closed
 931                 if ( $this->conn ) {
 932                         // Roll back any dangling transaction first
 933                         if ( $this->trxLevel ) {
 934                                 if ( $this->trxAtomicLevels ) {
 935                                         // Cannot let incomplete atomic sections be committed
 936                                         $levels = $this->flatAtomicSectionList();
 937                                         $exception = new DBUnexpectedError(
 938                                                 $this,
 939                                                 __METHOD__ . ": atomic sections $levels are still open."
 940                                         );
 941                                 } elseif ( $this->trxAutomatic ) {
 942                                         // Only the connection manager can commit non-empty DBO_TRX transactions
 943                                         // (empty ones we can silently roll back)
 944                                         if ( $this->writesOrCallbacksPending() ) {
 945                                                 $exception = new DBUnexpectedError(
 946                                                         $this,
 947                                                         __METHOD__ .
 948                                                         ": mass commit/rollback of peer transaction required (DBO_TRX set)."
 949                                                 );
 950                                         }
 951                                 } else {
 952                                         // Manual transactions should have been committed or rolled
 953                                         // back, even if empty.
 954                                         $exception = new DBUnexpectedError(
 955                                                 $this,
 956                                                 __METHOD__ . ": transaction is still open (from {$this->trxFname})."
 957                                         );
 958                                 }
 959
 960                                 if ( $this->trxEndCallbacksSuppressed ) {
 961                                         $exception = $exception ?: new DBUnexpectedError(
 962                                                 $this,
 963                                                 __METHOD__ . ': callbacks are suppressed; cannot properly commit.'
 964                                         );
 965                                 }
 966
 967                                 // Rollback the changes and run any callbacks as needed
 968                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
 969                         }
 970
 971                         // Close the actual connection in the binding handle
 972                         $closed = $this->closeConnection();
 973                 } else {
 974                         $closed = true; // already closed; nothing to do
 975                 }
 976
 977                 $this->conn = false;
 978                 $this->opened = false;
 979
 980                 // Throw any unexpected errors after having disconnected
 981                 if ( $exception instanceof Exception ) {
 982                         throw $exception;
 983                 }
 984
 985                 // Note that various subclasses call close() at the start of open(), which itself is
 986                 // called by replaceLostConnection(). In that case, just because onTransactionResolution()
 987                 // callbacks are pending does not mean that an exception should be thrown. Rather, they
 988                 // will be executed after the reconnection step.
 989                 if ( $wasOpen ) {
 990                         // Sanity check that no callbacks are dangling
 991                         $fnames = $this->pendingWriteAndCallbackCallers();
 992                         if ( $fnames ) {
 993                                 throw new RuntimeException(
 994                                         "Transaction callbacks are still pending:\n" . implode( ', ', $fnames )
 995                                 );
 996                         }
 997                 }
 998
 999                 return $closed;
1000         }
1001
1002         /**
1003          * Make sure there is an open connection handle (alive or not) as a sanity check
1004          *
1005          * This guards against fatal errors to the binding handle not being defined
1006          * in cases where open() was never called or close() was already called
1007          *
1008          * @throws DBUnexpectedError
1009          */
1010         protected function assertHasConnectionHandle() {
1011                 if ( !$this->isOpen() ) {
1012                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
1013                 }
1014         }
1015
1016         /**
1017          * Make sure that this server is not marked as a replica nor read-only as a sanity check
1018          *
1019          * @throws DBUnexpectedError
1020          */
1021         protected function assertIsWritableMaster() {
1022                 if ( $this->getLBInfo( 'replica' ) === true ) {
1023                         throw new DBUnexpectedError(
1024                                 $this,
1025                                 'Write operations are not allowed on replica database connections.'
1026                         );
1027                 }
1028                 $reason = $this->getReadOnlyReason();
1029                 if ( $reason !== false ) {
1030                         throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
1031                 }
1032         }
1033
1034         /**
1035          * Closes underlying database connection
1036          * @since 1.20
1037          * @return bool Whether connection was closed successfully
1038          */
1039         abstract protected function closeConnection();
1040
1041         /**
1042          * @deprecated since 1.32
1043          * @param string $error Fallback message, if none is given by DB
1044          * @throws DBConnectionError
1045          */
1046         public function reportConnectionError( $error = 'Unknown error' ) {
1047                 call_user_func( $this->deprecationLogger, 'Use of ' . __METHOD__ . ' is deprecated.' );
1048                 throw new DBConnectionError( $this, $this->lastError() ?: $error );
1049         }
1050
1051         /**
1052          * Run a query and return a DBMS-dependent wrapper or boolean
1053          *
1054          * For SELECT queries, this returns either:
1055          *   - a) A driver-specific value/resource, only on success. This can be iterated
1056          *        over by calling fetchObject()/fetchRow() until there are no more rows.
1057          *        Alternatively, the result can be passed to resultObject() to obtain a
1058          *        ResultWrapper instance which can then be iterated over via "foreach".
1059          *   - b) False, on any query failure
1060          *
1061          * For non-SELECT queries, this returns either:
1062          *   - a) A driver-specific value/resource, only on success
1063          *   - b) True, only on success (e.g. no meaningful result other than "OK")
1064          *   - c) False, on any query failure
1065          *
1066          * @param string $sql SQL query
1067          * @return mixed|bool An object, resource, or true on success; false on failure
1068          */
1069         abstract protected function doQuery( $sql );
1070
1071         /**
1072          * Determine whether a query writes to the DB. When in doubt, this returns true.
1073          *
1074          * Main use cases:
1075          *
1076          * - Subsequent web requests should not need to wait for replication from
1077          *   the master position seen by this web request, unless this request made
1078          *   changes to the master. This is handled by ChronologyProtector by checking
1079          *   doneWrites() at the end of the request. doneWrites() returns true if any
1080          *   query set lastWriteTime; which query() does based on isWriteQuery().
1081          *
1082          * - Reject write queries to replica DBs, in query().
1083          *
1084          * @param string $sql
1085          * @return bool
1086          */
1087         protected function isWriteQuery( $sql ) {
1088                 // BEGIN and COMMIT queries are considered read queries here.
1089                 // Database backends and drivers (MySQL, MariaDB, php-mysqli) generally
1090                 // treat these as write queries, in that their results have "affected rows"
1091                 // as meta data as from writes, instead of "num rows" as from reads.
1092                 // But, we treat them as read queries because when reading data (from
1093                 // either replica or master) we use transactions to enable repeatable-read
1094                 // snapshots, which ensures we get consistent results from the same snapshot
1095                 // for all queries within a request. Use cases:
1096                 // - Treating these as writes would trigger ChronologyProtector (see method doc).
1097                 // - We use this method to reject writes to replicas, but we need to allow
1098                 //   use of transactions on replicas for read snapshots. This fine given
1099                 //   that transactions by themselves don't make changes, only actual writes
1100                 //   within the transaction matter, which we still detect.
1101                 return !preg_match(
1102                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SAVEPOINT|RELEASE|SET|SHOW|EXPLAIN|\(SELECT)\b/i',
1103                         $sql
1104                 );
1105         }
1106
1107         /**
1108          * @param string $sql
1109          * @return string|null
1110          */
1111         protected function getQueryVerb( $sql ) {
1112                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
1113         }
1114
1115         /**
1116          * Determine whether a SQL statement is sensitive to isolation level.
1117          *
1118          * A SQL statement is considered transactable if its result could vary
1119          * depending on the transaction isolation level. Operational commands
1120          * such as 'SET' and 'SHOW' are not considered to be transactable.
1121          *
1122          * Main purpose: Used by query() to decide whether to begin a transaction
1123          * before the current query (in DBO_TRX mode, on by default).
1124          *
1125          * @param string $sql
1126          * @return bool
1127          */
1128         protected function isTransactableQuery( $sql ) {
1129                 return !in_array(
1130                         $this->getQueryVerb( $sql ),
1131                         [ 'BEGIN', 'ROLLBACK', 'COMMIT', 'SET', 'SHOW', 'CREATE', 'ALTER' ],
1132                         true
1133                 );
1134         }
1135
1136         /**
1137          * @param string $sql A SQL query
1138          * @return bool Whether $sql is SQL for TEMPORARY table operation
1139          */
1140         protected function registerTempTableOperation( $sql ) {
1141                 if ( preg_match(
1142                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1143                         $sql,
1144                         $matches
1145                 ) ) {
1146                         $this->sessionTempTables[$matches[1]] = 1;
1147
1148                         return true;
1149                 } elseif ( preg_match(
1150                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1151                         $sql,
1152                         $matches
1153                 ) ) {
1154                         $isTemp = isset( $this->sessionTempTables[$matches[1]] );
1155                         unset( $this->sessionTempTables[$matches[1]] );
1156
1157                         return $isTemp;
1158                 } elseif ( preg_match(
1159                         '/^TRUNCATE\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1160                         $sql,
1161                         $matches
1162                 ) ) {
1163                         return isset( $this->sessionTempTables[$matches[1]] );
1164                 } elseif ( preg_match(
1165                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
1166                         $sql,
1167                         $matches
1168                 ) ) {
1169                         return isset( $this->sessionTempTables[$matches[1]] );
1170                 }
1171
1172                 return false;
1173         }
1174
1175         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
1176                 $this->assertTransactionStatus( $sql, $fname );
1177                 $this->assertHasConnectionHandle();
1178
1179                 $priorTransaction = $this->trxLevel;
1180                 $priorWritesPending = $this->writesOrCallbacksPending();
1181                 $this->lastQuery = $sql;
1182
1183                 if ( $this->isWriteQuery( $sql ) ) {
1184                         # In theory, non-persistent writes are allowed in read-only mode, but due to things
1185                         # like https://bugs.mysql.com/bug.php?id=33669 that might not work anyway...
1186                         $this->assertIsWritableMaster();
1187                         # Avoid treating temporary table operations as meaningful "writes"
1188                         $isEffectiveWrite = !$this->registerTempTableOperation( $sql );
1189                 } else {
1190                         $isEffectiveWrite = false;
1191                 }
1192
1193                 # Add trace comment to the begin of the sql string, right after the operator.
1194                 # Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598)
1195                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
1196
1197                 # Send the query to the server and fetch any corresponding errors
1198                 $ret = $this->attemptQuery( $sql, $commentedSql, $isEffectiveWrite, $fname );
1199                 $lastError = $this->lastError();
1200                 $lastErrno = $this->lastErrno();
1201
1202                 $recoverableSR = false; // recoverable statement rollback?
1203                 $recoverableCL = false; // recoverable connection loss?
1204
1205                 if ( $ret === false && $this->wasConnectionLoss() ) {
1206                         # Check if no meaningful session state was lost
1207                         $recoverableCL = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
1208                         # Update session state tracking and try to restore the connection
1209                         $reconnected = $this->replaceLostConnection( __METHOD__ );
1210                         # Silently resend the query to the server if it is safe and possible
1211                         if ( $recoverableCL && $reconnected ) {
1212                                 $ret = $this->attemptQuery( $sql, $commentedSql, $isEffectiveWrite, $fname );
1213                                 $lastError = $this->lastError();
1214                                 $lastErrno = $this->lastErrno();
1215
1216                                 if ( $ret === false && $this->wasConnectionLoss() ) {
1217                                         # Query probably causes disconnects; reconnect and do not re-run it
1218                                         $this->replaceLostConnection( __METHOD__ );
1219                                 } else {
1220                                         $recoverableCL = false; // connection does not need recovering
1221                                         $recoverableSR = $this->wasKnownStatementRollbackError();
1222                                 }
1223                         }
1224                 } else {
1225                         $recoverableSR = $this->wasKnownStatementRollbackError();
1226                 }
1227
1228                 if ( $ret === false ) {
1229                         if ( $priorTransaction ) {
1230                                 if ( $recoverableSR ) {
1231                                         # We're ignoring an error that caused just the current query to be aborted.
1232                                         # But log the cause so we can log a deprecation notice if a caller actually
1233                                         # does ignore it.
1234                                         $this->trxStatusIgnoredCause = [ $lastError, $lastErrno, $fname ];
1235                                 } elseif ( !$recoverableCL ) {
1236                                         # Either the query was aborted or all queries after BEGIN where aborted.
1237                                         # In the first case, the only options going forward are (a) ROLLBACK, or
1238                                         # (b) ROLLBACK TO SAVEPOINT (if one was set). If the later case, the only
1239                                         # option is ROLLBACK, since the snapshots would have been released.
1240                                         $this->trxStatus = self::STATUS_TRX_ERROR;
1241                                         $this->trxStatusCause =
1242                                                 $this->getQueryExceptionAndLog( $lastError, $lastErrno, $sql, $fname );
1243                                         $tempIgnore = false; // cannot recover
1244                                         $this->trxStatusIgnoredCause = null;
1245                                 }
1246                         }
1247
1248                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname, $tempIgnore );
1249                 }
1250
1251                 return $this->resultObject( $ret );
1252         }
1253
1254         /**
1255          * Wrapper for query() that also handles profiling, logging, and affected row count updates
1256          *
1257          * @param string $sql Original SQL query
1258          * @param string $commentedSql SQL query with debugging/trace comment
1259          * @param bool $isEffectiveWrite Whether the query is a (non-temporary table) write
1260          * @param string $fname Name of the calling function
1261          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
1262          *     object for a successful read query, or false on failure
1263          */
1264         private function attemptQuery( $sql, $commentedSql, $isEffectiveWrite, $fname ) {
1265                 $this->beginIfImplied( $sql, $fname );
1266
1267                 # Keep track of whether the transaction has write queries pending
1268                 if ( $isEffectiveWrite ) {
1269                         $this->lastWriteTime = microtime( true );
1270                         if ( $this->trxLevel && !$this->trxDoneWrites ) {
1271                                 $this->trxDoneWrites = true;
1272                                 $this->trxProfiler->transactionWritingIn(
1273                                         $this->server, $this->getDomainID(), $this->trxShortId );
1274                         }
1275                 }
1276
1277                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
1278                         $this->queryLogger->debug( "{$this->getDomainID()} {$commentedSql}" );
1279                 }
1280
1281                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1282                 # generalizeSQL() will probably cut down the query to reasonable
1283                 # logging size most of the time. The substr is really just a sanity check.
1284                 if ( $isMaster ) {
1285                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1286                 } else {
1287                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1288                 }
1289
1290                 # Include query transaction state
1291                 $queryProf .= $this->trxShortId ? " [TRX#{$this->trxShortId}]" : "";
1292
1293                 $startTime = microtime( true );
1294                 $ps = $this->profiler ? ( $this->profiler )( $queryProf ) : null;
1295                 $this->affectedRowCount = null;
1296                 $ret = $this->doQuery( $commentedSql );
1297                 $this->affectedRowCount = $this->affectedRows();
1298                 unset( $ps ); // profile out (if set)
1299                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1300
1301                 if ( $ret !== false ) {
1302                         $this->lastPing = $startTime;
1303                         if ( $isEffectiveWrite && $this->trxLevel ) {
1304                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1305                                 $this->trxWriteCallers[] = $fname;
1306                         }
1307                 }
1308
1309                 if ( $sql === self::PING_QUERY ) {
1310                         $this->rttEstimate = $queryRuntime;
1311                 }
1312
1313                 $this->trxProfiler->recordQueryCompletion(
1314                         $queryProf,
1315                         $startTime,
1316                         $isEffectiveWrite,
1317                         $isEffectiveWrite ? $this->affectedRows() : $this->numRows( $ret )
1318                 );
1319                 $this->queryLogger->debug( $sql, [
1320                         'method' => $fname,
1321                         'master' => $isMaster,
1322                         'runtime' => $queryRuntime,
1323                 ] );
1324
1325                 return $ret;
1326         }
1327
1328         /**
1329          * Start an implicit transaction if DBO_TRX is enabled and no transaction is active
1330          *
1331          * @param string $sql
1332          * @param string $fname
1333          */
1334         private function beginIfImplied( $sql, $fname ) {
1335                 if (
1336                         !$this->trxLevel &&
1337                         $this->getFlag( self::DBO_TRX ) &&
1338                         $this->isTransactableQuery( $sql )
1339                 ) {
1340                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
1341                         $this->trxAutomatic = true;
1342                 }
1343         }
1344
1345         /**
1346          * Update the estimated run-time of a query, not counting large row lock times
1347          *
1348          * LoadBalancer can be set to rollback transactions that will create huge replication
1349          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1350          * queries, like inserting a row can take a long time due to row locking. This method
1351          * uses some simple heuristics to discount those cases.
1352          *
1353          * @param string $sql A SQL write query
1354          * @param float $runtime Total runtime, including RTT
1355          * @param int $affected Affected row count
1356          */
1357         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1358                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1359                 $indicativeOfReplicaRuntime = true;
1360                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1361                         $verb = $this->getQueryVerb( $sql );
1362                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1363                         if ( $verb === 'INSERT' ) {
1364                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1365                         } elseif ( $verb === 'REPLACE' ) {
1366                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1367                         }
1368                 }
1369
1370                 $this->trxWriteDuration += $runtime;
1371                 $this->trxWriteQueryCount += 1;
1372                 $this->trxWriteAffectedRows += $affected;
1373                 if ( $indicativeOfReplicaRuntime ) {
1374                         $this->trxWriteAdjDuration += $runtime;
1375                         $this->trxWriteAdjQueryCount += 1;
1376                 }
1377         }
1378
1379         /**
1380          * Error out if the DB is not in a valid state for a query via query()
1381          *
1382          * @param string $sql
1383          * @param string $fname
1384          * @throws DBTransactionStateError
1385          */
1386         private function assertTransactionStatus( $sql, $fname ) {
1387                 $verb = $this->getQueryVerb( $sql );
1388                 if ( $verb === 'USE' ) {
1389                         throw new DBUnexpectedError( $this, "Got USE query; use selectDomain() instead." );
1390                 }
1391
1392                 if ( $verb === 'ROLLBACK' ) { // transaction/savepoint
1393                         return;
1394                 }
1395
1396                 if ( $this->trxStatus < self::STATUS_TRX_OK ) {
1397                         throw new DBTransactionStateError(
1398                                 $this,
1399                                 "Cannot execute query from $fname while transaction status is ERROR.",
1400                                 [],
1401                                 $this->trxStatusCause
1402                         );
1403                 } elseif ( $this->trxStatus === self::STATUS_TRX_OK && $this->trxStatusIgnoredCause ) {
1404                         list( $iLastError, $iLastErrno, $iFname ) = $this->trxStatusIgnoredCause;
1405                         call_user_func( $this->deprecationLogger,
1406                                 "Caller from $fname ignored an error originally raised from $iFname: " .
1407                                 "[$iLastErrno] $iLastError"
1408                         );
1409                         $this->trxStatusIgnoredCause = null;
1410                 }
1411         }
1412
1413         public function assertNoOpenTransactions() {
1414                 if ( $this->explicitTrxActive() ) {
1415                         throw new DBTransactionError(
1416                                 $this,
1417                                 "Explicit transaction still active. A caller may have caught an error. "
1418                                 . "Open transactions: " . $this->flatAtomicSectionList()
1419                         );
1420                 }
1421         }
1422
1423         /**
1424          * Determine whether it is safe to retry queries after a database connection is lost
1425          *
1426          * @param string $sql SQL query
1427          * @param bool $priorWritesPending Whether there is a transaction open with
1428          *     possible write queries or transaction pre-commit/idle callbacks
1429          *     waiting on it to finish.
1430          * @return bool True if it is safe to retry the query, false otherwise
1431          */
1432         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1433                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1434                 # Dropped connections also mean that named locks are automatically released.
1435                 # Only allow error suppression in autocommit mode or when the lost transaction
1436                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1437                 if ( $this->namedLocksHeld ) {
1438                         return false; // possible critical section violation
1439                 } elseif ( $this->sessionTempTables ) {
1440                         return false; // tables might be queried latter
1441                 } elseif ( $sql === 'COMMIT' ) {
1442                         return !$priorWritesPending; // nothing written anyway? (T127428)
1443                 } elseif ( $sql === 'ROLLBACK' ) {
1444                         return true; // transaction lost...which is also what was requested :)
1445                 } elseif ( $this->explicitTrxActive() ) {
1446                         return false; // don't drop atomocity and explicit snapshots
1447                 } elseif ( $priorWritesPending ) {
1448                         return false; // prior writes lost from implicit transaction
1449                 }
1450
1451                 return true;
1452         }
1453
1454         /**
1455          * Clean things up after session (and thus transaction) loss before reconnect
1456          */
1457         private function handleSessionLossPreconnect() {
1458                 // Clean up tracking of session-level things...
1459                 // https://dev.mysql.com/doc/refman/5.7/en/implicit-commit.html
1460                 // https://www.postgresql.org/docs/9.2/static/sql-createtable.html (ignoring ON COMMIT)
1461                 $this->sessionTempTables = [];
1462                 // https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
1463                 // https://www.postgresql.org/docs/9.4/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
1464                 $this->namedLocksHeld = [];
1465                 // Session loss implies transaction loss
1466                 $this->trxLevel = 0;
1467                 $this->trxAtomicCounter = 0;
1468                 $this->trxIdleCallbacks = []; // T67263; transaction already lost
1469                 $this->trxPreCommitCallbacks = []; // T67263; transaction already lost
1470                 // @note: leave trxRecurringCallbacks in place
1471                 if ( $this->trxDoneWrites ) {
1472                         $this->trxProfiler->transactionWritingOut(
1473                                 $this->server,
1474                                 $this->getDomainID(),
1475                                 $this->trxShortId,
1476                                 $this->pendingWriteQueryDuration( self::ESTIMATE_TOTAL ),
1477                                 $this->trxWriteAffectedRows
1478                         );
1479                 }
1480         }
1481
1482         /**
1483          * Clean things up after session (and thus transaction) loss after reconnect
1484          */
1485         private function handleSessionLossPostconnect() {
1486                 try {
1487                         // Handle callbacks in trxEndCallbacks, e.g. onTransactionResolution().
1488                         // If callback suppression is set then the array will remain unhandled.
1489                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1490                 } catch ( Exception $ex ) {
1491                         // Already logged; move on...
1492                 }
1493                 try {
1494                         // Handle callbacks in trxRecurringCallbacks, e.g. setTransactionListener()
1495                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1496                 } catch ( Exception $ex ) {
1497                         // Already logged; move on...
1498                 }
1499         }
1500
1501         /**
1502          * Checks whether the cause of the error is detected to be a timeout.
1503          *
1504          * It returns false by default, and not all engines support detecting this yet.
1505          * If this returns false, it will be treated as a generic query error.
1506          *
1507          * @param string $error Error text
1508          * @param int $errno Error number
1509          * @return bool
1510          */
1511         protected function wasQueryTimeout( $error, $errno ) {
1512                 return false;
1513         }
1514
1515         /**
1516          * Report a query error. Log the error, and if neither the object ignore
1517          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1518          *
1519          * @param string $error
1520          * @param int $errno
1521          * @param string $sql
1522          * @param string $fname
1523          * @param bool $tempIgnore
1524          * @throws DBQueryError
1525          */
1526         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1527                 if ( $tempIgnore ) {
1528                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1529                 } else {
1530                         $exception = $this->getQueryExceptionAndLog( $error, $errno, $sql, $fname );
1531
1532                         throw $exception;
1533                 }
1534         }
1535
1536         /**
1537          * @param string $error
1538          * @param string|int $errno
1539          * @param string $sql
1540          * @param string $fname
1541          * @return DBError
1542          */
1543         private function getQueryExceptionAndLog( $error, $errno, $sql, $fname ) {
1544                 $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1545                 $this->queryLogger->error(
1546                         "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1547                         $this->getLogContext( [
1548                                 'method' => __METHOD__,
1549                                 'errno' => $errno,
1550                                 'error' => $error,
1551                                 'sql1line' => $sql1line,
1552                                 'fname' => $fname,
1553                                 'trace' => ( new RuntimeException() )->getTraceAsString()
1554                         ] )
1555                 );
1556                 $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1557                 $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1558                 if ( $wasQueryTimeout ) {
1559                         $e = new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1560                 } else {
1561                         $e = new DBQueryError( $this, $error, $errno, $sql, $fname );
1562                 }
1563
1564                 return $e;
1565         }
1566
1567         public function freeResult( $res ) {
1568         }
1569
1570         public function selectField(
1571                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1572         ) {
1573                 if ( $var === '*' ) { // sanity
1574                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1575                 }
1576
1577                 if ( !is_array( $options ) ) {
1578                         $options = [ $options ];
1579                 }
1580
1581                 $options['LIMIT'] = 1;
1582
1583                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1584                 if ( $res === false || !$this->numRows( $res ) ) {
1585                         return false;
1586                 }
1587
1588                 $row = $this->fetchRow( $res );
1589
1590                 if ( $row !== false ) {
1591                         return reset( $row );
1592                 } else {
1593                         return false;
1594                 }
1595         }
1596
1597         public function selectFieldValues(
1598                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1599         ) {
1600                 if ( $var === '*' ) { // sanity
1601                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1602                 } elseif ( !is_string( $var ) ) { // sanity
1603                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1604                 }
1605
1606                 if ( !is_array( $options ) ) {
1607                         $options = [ $options ];
1608                 }
1609
1610                 $res = $this->select( $table, [ 'value' => $var ], $cond, $fname, $options, $join_conds );
1611                 if ( $res === false ) {
1612                         return false;
1613                 }
1614
1615                 $values = [];
1616                 foreach ( $res as $row ) {
1617                         $values[] = $row->value;
1618                 }
1619
1620                 return $values;
1621         }
1622
1623         /**
1624          * Returns an optional USE INDEX clause to go after the table, and a
1625          * string to go at the end of the query.
1626          *
1627          * @param array $options Associative array of options to be turned into
1628          *   an SQL query, valid keys are listed in the function.
1629          * @return array
1630          * @see Database::select()
1631          */
1632         protected function makeSelectOptions( $options ) {
1633                 $preLimitTail = $postLimitTail = '';
1634                 $startOpts = '';
1635
1636                 $noKeyOptions = [];
1637
1638                 foreach ( $options as $key => $option ) {
1639                         if ( is_numeric( $key ) ) {
1640                                 $noKeyOptions[$option] = true;
1641                         }
1642                 }
1643
1644                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1645
1646                 $preLimitTail .= $this->makeOrderBy( $options );
1647
1648                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1649                         $postLimitTail .= ' FOR UPDATE';
1650                 }
1651
1652                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1653                         $postLimitTail .= ' LOCK IN SHARE MODE';
1654                 }
1655
1656                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1657                         $startOpts .= 'DISTINCT';
1658                 }
1659
1660                 # Various MySQL extensions
1661                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1662                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1663                 }
1664
1665                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1666                         $startOpts .= ' HIGH_PRIORITY';
1667                 }
1668
1669                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1670                         $startOpts .= ' SQL_BIG_RESULT';
1671                 }
1672
1673                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1674                         $startOpts .= ' SQL_BUFFER_RESULT';
1675                 }
1676
1677                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1678                         $startOpts .= ' SQL_SMALL_RESULT';
1679                 }
1680
1681                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1682                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1683                 }
1684
1685                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1686                         $startOpts .= ' SQL_CACHE';
1687                 }
1688
1689                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1690                         $startOpts .= ' SQL_NO_CACHE';
1691                 }
1692
1693                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1694                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1695                 } else {
1696                         $useIndex = '';
1697                 }
1698                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1699                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1700                 } else {
1701                         $ignoreIndex = '';
1702                 }
1703
1704                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1705         }
1706
1707         /**
1708          * Returns an optional GROUP BY with an optional HAVING
1709          *
1710          * @param array $options Associative array of options
1711          * @return string
1712          * @see Database::select()
1713          * @since 1.21
1714          */
1715         protected function makeGroupByWithHaving( $options ) {
1716                 $sql = '';
1717                 if ( isset( $options['GROUP BY'] ) ) {
1718                         $gb = is_array( $options['GROUP BY'] )
1719                                 ? implode( ',', $options['GROUP BY'] )
1720                                 : $options['GROUP BY'];
1721                         $sql .= ' GROUP BY ' . $gb;
1722                 }
1723                 if ( isset( $options['HAVING'] ) ) {
1724                         $having = is_array( $options['HAVING'] )
1725                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1726                                 : $options['HAVING'];
1727                         $sql .= ' HAVING ' . $having;
1728                 }
1729
1730                 return $sql;
1731         }
1732
1733         /**
1734          * Returns an optional ORDER BY
1735          *
1736          * @param array $options Associative array of options
1737          * @return string
1738          * @see Database::select()
1739          * @since 1.21
1740          */
1741         protected function makeOrderBy( $options ) {
1742                 if ( isset( $options['ORDER BY'] ) ) {
1743                         $ob = is_array( $options['ORDER BY'] )
1744                                 ? implode( ',', $options['ORDER BY'] )
1745                                 : $options['ORDER BY'];
1746
1747                         return ' ORDER BY ' . $ob;
1748                 }
1749
1750                 return '';
1751         }
1752
1753         public function select(
1754                 $table, $vars, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1755         ) {
1756                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1757
1758                 return $this->query( $sql, $fname );
1759         }
1760
1761         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1762                 $options = [], $join_conds = []
1763         ) {
1764                 if ( is_array( $vars ) ) {
1765                         $fields = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1766                 } else {
1767                         $fields = $vars;
1768                 }
1769
1770                 $options = (array)$options;
1771                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1772                         ? $options['USE INDEX']
1773                         : [];
1774                 $ignoreIndexes = (
1775                         isset( $options['IGNORE INDEX'] ) &&
1776                         is_array( $options['IGNORE INDEX'] )
1777                 )
1778                         ? $options['IGNORE INDEX']
1779                         : [];
1780
1781                 if (
1782                         $this->selectOptionsIncludeLocking( $options ) &&
1783                         $this->selectFieldsOrOptionsAggregate( $vars, $options )
1784                 ) {
1785                         // Some DB types (postgres/oracle) disallow FOR UPDATE with aggregate
1786                         // functions. Discourage use of such queries to encourage compatibility.
1787                         call_user_func(
1788                                 $this->deprecationLogger,
1789                                 __METHOD__ . ": aggregation used with a locking SELECT ($fname)."
1790                         );
1791                 }
1792
1793                 if ( is_array( $table ) ) {
1794                         $from = ' FROM ' .
1795                                 $this->tableNamesWithIndexClauseOrJOIN(
1796                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1797                 } elseif ( $table != '' ) {
1798                         $from = ' FROM ' .
1799                                 $this->tableNamesWithIndexClauseOrJOIN(
1800                                         [ $table ], $useIndexes, $ignoreIndexes, [] );
1801                 } else {
1802                         $from = '';
1803                 }
1804
1805                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1806                         $this->makeSelectOptions( $options );
1807
1808                 if ( is_array( $conds ) ) {
1809                         $conds = $this->makeList( $conds, self::LIST_AND );
1810                 }
1811
1812                 if ( $conds === null || $conds === false ) {
1813                         $this->queryLogger->warning(
1814                                 __METHOD__
1815                                 . ' called from '
1816                                 . $fname
1817                                 . ' with incorrect parameters: $conds must be a string or an array'
1818                         );
1819                         $conds = '';
1820                 }
1821
1822                 if ( $conds === '' || $conds === '*' ) {
1823                         $sql = "SELECT $startOpts $fields $from $useIndex $ignoreIndex $preLimitTail";
1824                 } elseif ( is_string( $conds ) ) {
1825                         $sql = "SELECT $startOpts $fields $from $useIndex $ignoreIndex " .
1826                                 "WHERE $conds $preLimitTail";
1827                 } else {
1828                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1829                 }
1830
1831                 if ( isset( $options['LIMIT'] ) ) {
1832                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1833                                 $options['OFFSET'] ?? false );
1834                 }
1835                 $sql = "$sql $postLimitTail";
1836
1837                 if ( isset( $options['EXPLAIN'] ) ) {
1838                         $sql = 'EXPLAIN ' . $sql;
1839                 }
1840
1841                 return $sql;
1842         }
1843
1844         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1845                 $options = [], $join_conds = []
1846         ) {
1847                 $options = (array)$options;
1848                 $options['LIMIT'] = 1;
1849                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1850
1851                 if ( $res === false ) {
1852                         return false;
1853                 }
1854
1855                 if ( !$this->numRows( $res ) ) {
1856                         return false;
1857                 }
1858
1859                 $obj = $this->fetchObject( $res );
1860
1861                 return $obj;
1862         }
1863
1864         public function estimateRowCount(
1865                 $table, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1866         ) {
1867                 $conds = $this->normalizeConditions( $conds, $fname );
1868                 $column = $this->extractSingleFieldFromList( $var );
1869                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1870                         $conds[] = "$column IS NOT NULL";
1871                 }
1872
1873                 $res = $this->select(
1874                         $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options, $join_conds
1875                 );
1876                 $row = $res ? $this->fetchRow( $res ) : [];
1877
1878                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1879         }
1880
1881         public function selectRowCount(
1882                 $tables, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1883         ) {
1884                 $conds = $this->normalizeConditions( $conds, $fname );
1885                 $column = $this->extractSingleFieldFromList( $var );
1886                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1887                         $conds[] = "$column IS NOT NULL";
1888                 }
1889
1890                 $res = $this->select(
1891                         [
1892                                 'tmp_count' => $this->buildSelectSubquery(
1893                                         $tables,
1894                                         '1',
1895                                         $conds,
1896                                         $fname,
1897                                         $options,
1898                                         $join_conds
1899                                 )
1900                         ],
1901                         [ 'rowcount' => 'COUNT(*)' ],
1902                         [],
1903                         $fname
1904                 );
1905                 $row = $res ? $this->fetchRow( $res ) : [];
1906
1907                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1908         }
1909
1910         /**
1911          * @param string|array $options
1912          * @return bool
1913          */
1914         private function selectOptionsIncludeLocking( $options ) {
1915                 $options = (array)$options;
1916                 foreach ( [ 'FOR UPDATE', 'LOCK IN SHARE MODE' ] as $lock ) {
1917                         if ( in_array( $lock, $options, true ) ) {
1918                                 return true;
1919                         }
1920                 }
1921
1922                 return false;
1923         }
1924
1925         /**
1926          * @param array|string $fields
1927          * @param array|string $options
1928          * @return bool
1929          */
1930         private function selectFieldsOrOptionsAggregate( $fields, $options ) {
1931                 foreach ( (array)$options as $key => $value ) {
1932                         if ( is_string( $key ) ) {
1933                                 if ( preg_match( '/^(?:GROUP BY|HAVING)$/i', $key ) ) {
1934                                         return true;
1935                                 }
1936                         } elseif ( is_string( $value ) ) {
1937                                 if ( preg_match( '/^(?:DISTINCT|DISTINCTROW)$/i', $value ) ) {
1938                                         return true;
1939                                 }
1940                         }
1941                 }
1942
1943                 $regex = '/^(?:COUNT|MIN|MAX|SUM|GROUP_CONCAT|LISTAGG|ARRAY_AGG)\s*\\(/i';
1944                 foreach ( (array)$fields as $field ) {
1945                         if ( is_string( $field ) && preg_match( $regex, $field ) ) {
1946                                 return true;
1947                         }
1948                 }
1949
1950                 return false;
1951         }
1952
1953         /**
1954          * @param array|string $conds
1955          * @param string $fname
1956          * @return array
1957          */
1958         final protected function normalizeConditions( $conds, $fname ) {
1959                 if ( $conds === null || $conds === false ) {
1960                         $this->queryLogger->warning(
1961                                 __METHOD__
1962                                 . ' called from '
1963                                 . $fname
1964                                 . ' with incorrect parameters: $conds must be a string or an array'
1965                         );
1966                         $conds = '';
1967                 }
1968
1969                 if ( !is_array( $conds ) ) {
1970                         $conds = ( $conds === '' ) ? [] : [ $conds ];
1971                 }
1972
1973                 return $conds;
1974         }
1975
1976         /**
1977          * @param array|string $var Field parameter in the style of select()
1978          * @return string|null Column name or null; ignores aliases
1979          * @throws DBUnexpectedError Errors out if multiple columns are given
1980          */
1981         final protected function extractSingleFieldFromList( $var ) {
1982                 if ( is_array( $var ) ) {
1983                         if ( !$var ) {
1984                                 $column = null;
1985                         } elseif ( count( $var ) == 1 ) {
1986                                 $column = $var[0] ?? reset( $var );
1987                         } else {
1988                                 throw new DBUnexpectedError( $this, __METHOD__ . ': got multiple columns.' );
1989                         }
1990                 } else {
1991                         $column = $var;
1992                 }
1993
1994                 return $column;
1995         }
1996
1997         public function lockForUpdate(
1998                 $table, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1999         ) {
2000                 if ( !$this->trxLevel && !$this->getFlag( self::DBO_TRX ) ) {
2001                         throw new DBUnexpectedError(
2002                                 $this,
2003                                 __METHOD__ . ': no transaction is active nor is DBO_TRX set'
2004                         );
2005                 }
2006
2007                 $options = (array)$options;
2008                 $options[] = 'FOR UPDATE';
2009
2010                 return $this->selectRowCount( $table, '*', $conds, $fname, $options, $join_conds );
2011         }
2012
2013         /**
2014          * Removes most variables from an SQL query and replaces them with X or N for numbers.
2015          * It's only slightly flawed. Don't use for anything important.
2016          *
2017          * @param string $sql A SQL Query
2018          *
2019          * @return string
2020          */
2021         protected static function generalizeSQL( $sql ) {
2022                 # This does the same as the regexp below would do, but in such a way
2023                 # as to avoid crashing php on some large strings.
2024                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
2025
2026                 $sql = str_replace( "\\\\", '', $sql );
2027                 $sql = str_replace( "\\'", '', $sql );
2028                 $sql = str_replace( "\\\"", '', $sql );
2029                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
2030                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
2031
2032                 # All newlines, tabs, etc replaced by single space
2033                 $sql = preg_replace( '/\s+/', ' ', $sql );
2034
2035                 # All numbers => N,
2036                 # except the ones surrounded by characters, e.g. l10n
2037                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
2038                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
2039
2040                 return $sql;
2041         }
2042
2043         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
2044                 $info = $this->fieldInfo( $table, $field );
2045
2046                 return (bool)$info;
2047         }
2048
2049         public function indexExists( $table, $index, $fname = __METHOD__ ) {
2050                 if ( !$this->tableExists( $table ) ) {
2051                         return null;
2052                 }
2053
2054                 $info = $this->indexInfo( $table, $index, $fname );
2055                 if ( is_null( $info ) ) {
2056                         return null;
2057                 } else {
2058                         return $info !== false;
2059                 }
2060         }
2061
2062         abstract public function tableExists( $table, $fname = __METHOD__ );
2063
2064         public function indexUnique( $table, $index ) {
2065                 $indexInfo = $this->indexInfo( $table, $index );
2066
2067                 if ( !$indexInfo ) {
2068                         return null;
2069                 }
2070
2071                 return !$indexInfo[0]->Non_unique;
2072         }
2073
2074         /**
2075          * Helper for Database::insert().
2076          *
2077          * @param array $options
2078          * @return string
2079          */
2080         protected function makeInsertOptions( $options ) {
2081                 return implode( ' ', $options );
2082         }
2083
2084         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
2085                 # No rows to insert, easy just return now
2086                 if ( !count( $a ) ) {
2087                         return true;
2088                 }
2089
2090                 $table = $this->tableName( $table );
2091
2092                 if ( !is_array( $options ) ) {
2093                         $options = [ $options ];
2094                 }
2095
2096                 $options = $this->makeInsertOptions( $options );
2097
2098                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
2099                         $multi = true;
2100                         $keys = array_keys( $a[0] );
2101                 } else {
2102                         $multi = false;
2103                         $keys = array_keys( $a );
2104                 }
2105
2106                 $sql = 'INSERT ' . $options .
2107                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
2108
2109                 if ( $multi ) {
2110                         $first = true;
2111                         foreach ( $a as $row ) {
2112                                 if ( $first ) {
2113                                         $first = false;
2114                                 } else {
2115                                         $sql .= ',';
2116                                 }
2117                                 $sql .= '(' . $this->makeList( $row ) . ')';
2118                         }
2119                 } else {
2120                         $sql .= '(' . $this->makeList( $a ) . ')';
2121                 }
2122
2123                 $this->query( $sql, $fname );
2124
2125                 return true;
2126         }
2127
2128         /**
2129          * Make UPDATE options array for Database::makeUpdateOptions
2130          *
2131          * @param array $options
2132          * @return array
2133          */
2134         protected function makeUpdateOptionsArray( $options ) {
2135                 if ( !is_array( $options ) ) {
2136                         $options = [ $options ];
2137                 }
2138
2139                 $opts = [];
2140
2141                 if ( in_array( 'IGNORE', $options ) ) {
2142                         $opts[] = 'IGNORE';
2143                 }
2144
2145                 return $opts;
2146         }
2147
2148         /**
2149          * Make UPDATE options for the Database::update function
2150          *
2151          * @param array $options The options passed to Database::update
2152          * @return string
2153          */
2154         protected function makeUpdateOptions( $options ) {
2155                 $opts = $this->makeUpdateOptionsArray( $options );
2156
2157                 return implode( ' ', $opts );
2158         }
2159
2160         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
2161                 $table = $this->tableName( $table );
2162                 $opts = $this->makeUpdateOptions( $options );
2163                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
2164
2165                 if ( $conds !== [] && $conds !== '*' ) {
2166                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
2167                 }
2168
2169                 $this->query( $sql, $fname );
2170
2171                 return true;
2172         }
2173
2174         public function makeList( $a, $mode = self::LIST_COMMA ) {
2175                 if ( !is_array( $a ) ) {
2176                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
2177                 }
2178
2179                 $first = true;
2180                 $list = '';
2181
2182                 foreach ( $a as $field => $value ) {
2183                         if ( !$first ) {
2184                                 if ( $mode == self::LIST_AND ) {
2185                                         $list .= ' AND ';
2186                                 } elseif ( $mode == self::LIST_OR ) {
2187                                         $list .= ' OR ';
2188                                 } else {
2189                                         $list .= ',';
2190                                 }
2191                         } else {
2192                                 $first = false;
2193                         }
2194
2195                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
2196                                 $list .= "($value)";
2197                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
2198                                 $list .= "$value";
2199                         } elseif (
2200                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
2201                         ) {
2202                                 // Remove null from array to be handled separately if found
2203                                 $includeNull = false;
2204                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
2205                                         $includeNull = true;
2206                                         unset( $value[$nullKey] );
2207                                 }
2208                                 if ( count( $value ) == 0 && !$includeNull ) {
2209                                         throw new InvalidArgumentException(
2210                                                 __METHOD__ . ": empty input for field $field" );
2211                                 } elseif ( count( $value ) == 0 ) {
2212                                         // only check if $field is null
2213                                         $list .= "$field IS NULL";
2214                                 } else {
2215                                         // IN clause contains at least one valid element
2216                                         if ( $includeNull ) {
2217                                                 // Group subconditions to ensure correct precedence
2218                                                 $list .= '(';
2219                                         }
2220                                         if ( count( $value ) == 1 ) {
2221                                                 // Special-case single values, as IN isn't terribly efficient
2222                                                 // Don't necessarily assume the single key is 0; we don't
2223                                                 // enforce linear numeric ordering on other arrays here.
2224                                                 $value = array_values( $value )[0];
2225                                                 $list .= $field . " = " . $this->addQuotes( $value );
2226                                         } else {
2227                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
2228                                         }
2229                                         // if null present in array, append IS NULL
2230                                         if ( $includeNull ) {
2231                                                 $list .= " OR $field IS NULL)";
2232                                         }
2233                                 }
2234                         } elseif ( $value === null ) {
2235                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
2236                                         $list .= "$field IS ";
2237                                 } elseif ( $mode == self::LIST_SET ) {
2238                                         $list .= "$field = ";
2239                                 }
2240                                 $list .= 'NULL';
2241                         } else {
2242                                 if (
2243                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
2244                                 ) {
2245                                         $list .= "$field = ";
2246                                 }
2247                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
2248                         }
2249                 }
2250
2251                 return $list;
2252         }
2253
2254         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2255                 $conds = [];
2256
2257                 foreach ( $data as $base => $sub ) {
2258                         if ( count( $sub ) ) {
2259                                 $conds[] = $this->makeList(
2260                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
2261                                         self::LIST_AND );
2262                         }
2263                 }
2264
2265                 if ( $conds ) {
2266                         return $this->makeList( $conds, self::LIST_OR );
2267                 } else {
2268                         // Nothing to search for...
2269                         return false;
2270                 }
2271         }
2272
2273         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2274                 return $valuename;
2275         }
2276
2277         public function bitNot( $field ) {
2278                 return "(~$field)";
2279         }
2280
2281         public function bitAnd( $fieldLeft, $fieldRight ) {
2282                 return "($fieldLeft & $fieldRight)";
2283         }
2284
2285         public function bitOr( $fieldLeft, $fieldRight ) {
2286                 return "($fieldLeft | $fieldRight)";
2287         }
2288
2289         public function buildConcat( $stringList ) {
2290                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2291         }
2292
2293         public function buildGroupConcatField(
2294                 $delim, $table, $field, $conds = '', $join_conds = []
2295         ) {
2296                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
2297
2298                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
2299         }
2300
2301         public function buildSubstring( $input, $startPosition, $length = null ) {
2302                 $this->assertBuildSubstringParams( $startPosition, $length );
2303                 $functionBody = "$input FROM $startPosition";
2304                 if ( $length !== null ) {
2305                         $functionBody .= " FOR $length";
2306                 }
2307                 return 'SUBSTRING(' . $functionBody . ')';
2308         }
2309
2310         /**
2311          * Check type and bounds for parameters to self::buildSubstring()
2312          *
2313          * All supported databases have substring functions that behave the same for
2314          * positive $startPosition and non-negative $length, but behaviors differ when
2315          * given 0 or negative $startPosition or negative $length. The simplest
2316          * solution to that is to just forbid those values.
2317          *
2318          * @param int $startPosition
2319          * @param int|null $length
2320          * @since 1.31
2321          */
2322         protected function assertBuildSubstringParams( $startPosition, $length ) {
2323                 if ( !is_int( $startPosition ) || $startPosition <= 0 ) {
2324                         throw new InvalidArgumentException(
2325                                 '$startPosition must be a positive integer'
2326                         );
2327                 }
2328                 if ( !( is_int( $length ) && $length >= 0 || $length === null ) ) {
2329                         throw new InvalidArgumentException(
2330                                 '$length must be null or an integer greater than or equal to 0'
2331                         );
2332                 }
2333         }
2334
2335         public function buildStringCast( $field ) {
2336                 // In theory this should work for any standards-compliant
2337                 // SQL implementation, although it may not be the best way to do it.
2338                 return "CAST( $field AS CHARACTER )";
2339         }
2340
2341         public function buildIntegerCast( $field ) {
2342                 return 'CAST( ' . $field . ' AS INTEGER )';
2343         }
2344
2345         public function buildSelectSubquery(
2346                 $table, $vars, $conds = '', $fname = __METHOD__,
2347                 $options = [], $join_conds = []
2348         ) {
2349                 return new Subquery(
2350                         $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds )
2351                 );
2352         }
2353
2354         public function databasesAreIndependent() {
2355                 return false;
2356         }
2357
2358         final public function selectDB( $db ) {
2359                 $this->selectDomain( new DatabaseDomain(
2360                         $db,
2361                         $this->currentDomain->getSchema(),
2362                         $this->currentDomain->getTablePrefix()
2363                 ) );
2364
2365                 return true;
2366         }
2367
2368         final public function selectDomain( $domain ) {
2369                 $this->doSelectDomain( DatabaseDomain::newFromId( $domain ) );
2370         }
2371
2372         protected function doSelectDomain( DatabaseDomain $domain ) {
2373                 $this->currentDomain = $domain;
2374         }
2375
2376         public function getDBname() {
2377                 return $this->currentDomain->getDatabase();
2378         }
2379
2380         public function getServer() {
2381                 return $this->server;
2382         }
2383
2384         public function tableName( $name, $format = 'quoted' ) {
2385                 if ( $name instanceof Subquery ) {
2386                         throw new DBUnexpectedError(
2387                                 $this,
2388                                 __METHOD__ . ': got Subquery instance when expecting a string.'
2389                         );
2390                 }
2391
2392                 # Skip the entire process when we have a string quoted on both ends.
2393                 # Note that we check the end so that we will still quote any use of
2394                 # use of `database`.table. But won't break things if someone wants
2395                 # to query a database table with a dot in the name.
2396                 if ( $this->isQuotedIdentifier( $name ) ) {
2397                         return $name;
2398                 }
2399
2400                 # Lets test for any bits of text that should never show up in a table
2401                 # name. Basically anything like JOIN or ON which are actually part of
2402                 # SQL queries, but may end up inside of the table value to combine
2403                 # sql. Such as how the API is doing.
2404                 # Note that we use a whitespace test rather than a \b test to avoid
2405                 # any remote case where a word like on may be inside of a table name
2406                 # surrounded by symbols which may be considered word breaks.
2407                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2408                         $this->queryLogger->warning(
2409                                 __METHOD__ . ": use of subqueries is not supported this way.",
2410                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
2411                         );
2412
2413                         return $name;
2414                 }
2415
2416                 # Split database and table into proper variables.
2417                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
2418
2419                 # Quote $table and apply the prefix if not quoted.
2420                 # $tableName might be empty if this is called from Database::replaceVars()
2421                 $tableName = "{$prefix}{$table}";
2422                 if ( $format === 'quoted'
2423                         && !$this->isQuotedIdentifier( $tableName )
2424                         && $tableName !== ''
2425                 ) {
2426                         $tableName = $this->addIdentifierQuotes( $tableName );
2427                 }
2428
2429                 # Quote $schema and $database and merge them with the table name if needed
2430                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
2431                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
2432
2433                 return $tableName;
2434         }
2435
2436         /**
2437          * Get the table components needed for a query given the currently selected database
2438          *
2439          * @param string $name Table name in the form of db.schema.table, db.table, or table
2440          * @return array (DB name or "" for default, schema name, table prefix, table name)
2441          */
2442         protected function qualifiedTableComponents( $name ) {
2443                 # We reverse the explode so that database.table and table both output the correct table.
2444                 $dbDetails = explode( '.', $name, 3 );
2445                 if ( count( $dbDetails ) == 3 ) {
2446                         list( $database, $schema, $table ) = $dbDetails;
2447                         # We don't want any prefix added in this case
2448                         $prefix = '';
2449                 } elseif ( count( $dbDetails ) == 2 ) {
2450                         list( $database, $table ) = $dbDetails;
2451                         # We don't want any prefix added in this case
2452                         $prefix = '';
2453                         # In dbs that support it, $database may actually be the schema
2454                         # but that doesn't affect any of the functionality here
2455                         $schema = '';
2456                 } else {
2457                         list( $table ) = $dbDetails;
2458                         if ( isset( $this->tableAliases[$table] ) ) {
2459                                 $database = $this->tableAliases[$table]['dbname'];
2460                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
2461                                         ? $this->tableAliases[$table]['schema']
2462                                         : $this->relationSchemaQualifier();
2463                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
2464                                         ? $this->tableAliases[$table]['prefix']
2465                                         : $this->tablePrefix();
2466                         } else {
2467                                 $database = '';
2468                                 $schema = $this->relationSchemaQualifier(); # Default schema
2469                                 $prefix = $this->tablePrefix(); # Default prefix
2470                         }
2471                 }
2472
2473                 return [ $database, $schema, $prefix, $table ];
2474         }
2475
2476         /**
2477          * @param string|null $namespace Database or schema
2478          * @param string $relation Name of table, view, sequence, etc...
2479          * @param string $format One of (raw, quoted)
2480          * @return string Relation name with quoted and merged $namespace as needed
2481          */
2482         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
2483                 if ( strlen( $namespace ) ) {
2484                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
2485                                 $namespace = $this->addIdentifierQuotes( $namespace );
2486                         }
2487                         $relation = $namespace . '.' . $relation;
2488                 }
2489
2490                 return $relation;
2491         }
2492
2493         public function tableNames() {
2494                 $inArray = func_get_args();
2495                 $retVal = [];
2496
2497                 foreach ( $inArray as $name ) {
2498                         $retVal[$name] = $this->tableName( $name );
2499                 }
2500
2501                 return $retVal;
2502         }
2503
2504         public function tableNamesN() {
2505                 $inArray = func_get_args();
2506                 $retVal = [];
2507
2508                 foreach ( $inArray as $name ) {
2509                         $retVal[] = $this->tableName( $name );
2510                 }
2511
2512                 return $retVal;
2513         }
2514
2515         /**
2516          * Get an aliased table name
2517          *
2518          * This returns strings like "tableName AS newTableName" for aliased tables
2519          * and "(SELECT * from tableA) newTablename" for subqueries (e.g. derived tables)
2520          *
2521          * @see Database::tableName()
2522          * @param string|Subquery $table Table name or object with a 'sql' field
2523          * @param string|bool $alias Table alias (optional)
2524          * @return string SQL name for aliased table. Will not alias a table to its own name
2525          */
2526         protected function tableNameWithAlias( $table, $alias = false ) {
2527                 if ( is_string( $table ) ) {
2528                         $quotedTable = $this->tableName( $table );
2529                 } elseif ( $table instanceof Subquery ) {
2530                         $quotedTable = (string)$table;
2531                 } else {
2532                         throw new InvalidArgumentException( "Table must be a string or Subquery." );
2533                 }
2534
2535                 if ( !strlen( $alias ) || $alias === $table ) {
2536                         if ( $table instanceof Subquery ) {
2537                                 throw new InvalidArgumentException( "Subquery table missing alias." );
2538                         }
2539
2540                         return $quotedTable;
2541                 } else {
2542                         return $quotedTable . ' ' . $this->addIdentifierQuotes( $alias );
2543                 }
2544         }
2545
2546         /**
2547          * Gets an array of aliased table names
2548          *
2549          * @param array $tables [ [alias] => table ]
2550          * @return string[] See tableNameWithAlias()
2551          */
2552         protected function tableNamesWithAlias( $tables ) {
2553                 $retval = [];
2554                 foreach ( $tables as $alias => $table ) {
2555                         if ( is_numeric( $alias ) ) {
2556                                 $alias = $table;
2557                         }
2558                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2559                 }
2560
2561                 return $retval;
2562         }
2563
2564         /**
2565          * Get an aliased field name
2566          * e.g. fieldName AS newFieldName
2567          *
2568          * @param string $name Field name
2569          * @param string|bool $alias Alias (optional)
2570          * @return string SQL name for aliased field. Will not alias a field to its own name
2571          */
2572         protected function fieldNameWithAlias( $name, $alias = false ) {
2573                 if ( !$alias || (string)$alias === (string)$name ) {
2574                         return $name;
2575                 } else {
2576                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
2577                 }
2578         }
2579
2580         /**
2581          * Gets an array of aliased field names
2582          *
2583          * @param array $fields [ [alias] => field ]
2584          * @return string[] See fieldNameWithAlias()
2585          */
2586         protected function fieldNamesWithAlias( $fields ) {
2587                 $retval = [];
2588                 foreach ( $fields as $alias => $field ) {
2589                         if ( is_numeric( $alias ) ) {
2590                                 $alias = $field;
2591                         }
2592                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2593                 }
2594
2595                 return $retval;
2596         }
2597
2598         /**
2599          * Get the aliased table name clause for a FROM clause
2600          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2601          *
2602          * @param array $tables ( [alias] => table )
2603          * @param array $use_index Same as for select()
2604          * @param array $ignore_index Same as for select()
2605          * @param array $join_conds Same as for select()
2606          * @return string
2607          */
2608         protected function tableNamesWithIndexClauseOrJOIN(
2609                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2610         ) {
2611                 $ret = [];
2612                 $retJOIN = [];
2613                 $use_index = (array)$use_index;
2614                 $ignore_index = (array)$ignore_index;
2615                 $join_conds = (array)$join_conds;
2616
2617                 foreach ( $tables as $alias => $table ) {
2618                         if ( !is_string( $alias ) ) {
2619                                 // No alias? Set it equal to the table name
2620                                 $alias = $table;
2621                         }
2622
2623                         if ( is_array( $table ) ) {
2624                                 // A parenthesized group
2625                                 if ( count( $table ) > 1 ) {
2626                                         $joinedTable = '(' .
2627                                                 $this->tableNamesWithIndexClauseOrJOIN(
2628                                                         $table, $use_index, $ignore_index, $join_conds ) . ')';
2629                                 } else {
2630                                         // Degenerate case
2631                                         $innerTable = reset( $table );
2632                                         $innerAlias = key( $table );
2633                                         $joinedTable = $this->tableNameWithAlias(
2634                                                 $innerTable,
2635                                                 is_string( $innerAlias ) ? $innerAlias : $innerTable
2636                                         );
2637                                 }
2638                         } else {
2639                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2640                         }
2641
2642                         // Is there a JOIN clause for this table?
2643                         if ( isset( $join_conds[$alias] ) ) {
2644                                 list( $joinType, $conds ) = $join_conds[$alias];
2645                                 $tableClause = $joinType;
2646                                 $tableClause .= ' ' . $joinedTable;
2647                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2648                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2649                                         if ( $use != '' ) {
2650                                                 $tableClause .= ' ' . $use;
2651                                         }
2652                                 }
2653                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2654                                         $ignore = $this->ignoreIndexClause(
2655                                                 implode( ',', (array)$ignore_index[$alias] ) );
2656                                         if ( $ignore != '' ) {
2657                                                 $tableClause .= ' ' . $ignore;
2658                                         }
2659                                 }
2660                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2661                                 if ( $on != '' ) {
2662                                         $tableClause .= ' ON (' . $on . ')';
2663                                 }
2664
2665                                 $retJOIN[] = $tableClause;
2666                         } elseif ( isset( $use_index[$alias] ) ) {
2667                                 // Is there an INDEX clause for this table?
2668                                 $tableClause = $joinedTable;
2669                                 $tableClause .= ' ' . $this->useIndexClause(
2670                                                 implode( ',', (array)$use_index[$alias] )
2671                                         );
2672
2673                                 $ret[] = $tableClause;
2674                         } elseif ( isset( $ignore_index[$alias] ) ) {
2675                                 // Is there an INDEX clause for this table?
2676                                 $tableClause = $joinedTable;
2677                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2678                                                 implode( ',', (array)$ignore_index[$alias] )
2679                                         );
2680
2681                                 $ret[] = $tableClause;
2682                         } else {
2683                                 $tableClause = $joinedTable;
2684
2685                                 $ret[] = $tableClause;
2686                         }
2687                 }
2688
2689                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2690                 $implicitJoins = $ret ? implode( ',', $ret ) : "";
2691                 $explicitJoins = $retJOIN ? implode( ' ', $retJOIN ) : "";
2692
2693                 // Compile our final table clause
2694                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2695         }
2696
2697         /**
2698          * Allows for index remapping in queries where this is not consistent across DBMS
2699          *
2700          * @param string $index
2701          * @return string
2702          */
2703         protected function indexName( $index ) {
2704                 return $this->indexAliases[$index] ?? $index;
2705         }
2706
2707         public function addQuotes( $s ) {
2708                 if ( $s instanceof Blob ) {
2709                         $s = $s->fetch();
2710                 }
2711                 if ( $s === null ) {
2712                         return 'NULL';
2713                 } elseif ( is_bool( $s ) ) {
2714                         return (int)$s;
2715                 } else {
2716                         # This will also quote numeric values. This should be harmless,
2717                         # and protects against weird problems that occur when they really
2718                         # _are_ strings such as article titles and string->number->string
2719                         # conversion is not 1:1.
2720                         return "'" . $this->strencode( $s ) . "'";
2721                 }
2722         }
2723
2724         public function addIdentifierQuotes( $s ) {
2725                 return '"' . str_replace( '"', '""', $s ) . '"';
2726         }
2727
2728         /**
2729          * Returns if the given identifier looks quoted or not according to
2730          * the database convention for quoting identifiers .
2731          *
2732          * @note Do not use this to determine if untrusted input is safe.
2733          *   A malicious user can trick this function.
2734          * @param string $name
2735          * @return bool
2736          */
2737         public function isQuotedIdentifier( $name ) {
2738                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2739         }
2740
2741         /**
2742          * @param string $s
2743          * @param string $escapeChar
2744          * @return string
2745          */
2746         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2747                 return str_replace( [ $escapeChar, '%', '_' ],
2748                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2749                         $s );
2750         }
2751
2752         public function buildLike() {
2753                 $params = func_get_args();
2754
2755                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2756                         $params = $params[0];
2757                 }
2758
2759                 $s = '';
2760
2761                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2762                 // may escape backslashes, creating problems of double escaping. The `
2763                 // character has good cross-DBMS compatibility, avoiding special operators
2764                 // in MS SQL like ^ and %
2765                 $escapeChar = '`';
2766
2767                 foreach ( $params as $value ) {
2768                         if ( $value instanceof LikeMatch ) {
2769                                 $s .= $value->toString();
2770                         } else {
2771                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2772                         }
2773                 }
2774
2775                 return ' LIKE ' .
2776                         $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2777         }
2778
2779         public function anyChar() {
2780                 return new LikeMatch( '_' );
2781         }
2782
2783         public function anyString() {
2784                 return new LikeMatch( '%' );
2785         }
2786
2787         public function nextSequenceValue( $seqName ) {
2788                 return null;
2789         }
2790
2791         /**
2792          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2793          * is only needed because a) MySQL must be as efficient as possible due to
2794          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2795          * which index to pick. Anyway, other databases might have different
2796          * indexes on a given table. So don't bother overriding this unless you're
2797          * MySQL.
2798          * @param string $index
2799          * @return string
2800          */
2801         public function useIndexClause( $index ) {
2802                 return '';
2803         }
2804
2805         /**
2806          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2807          * is only needed because a) MySQL must be as efficient as possible due to
2808          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2809          * which index to pick. Anyway, other databases might have different
2810          * indexes on a given table. So don't bother overriding this unless you're
2811          * MySQL.
2812          * @param string $index
2813          * @return string
2814          */
2815         public function ignoreIndexClause( $index ) {
2816                 return '';
2817         }
2818
2819         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2820                 if ( count( $rows ) == 0 ) {
2821                         return;
2822                 }
2823
2824                 $uniqueIndexes = (array)$uniqueIndexes;
2825                 // Single row case
2826                 if ( !is_array( reset( $rows ) ) ) {
2827                         $rows = [ $rows ];
2828                 }
2829
2830                 try {
2831                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2832                         $affectedRowCount = 0;
2833                         foreach ( $rows as $row ) {
2834                                 // Delete rows which collide with this one
2835                                 $indexWhereClauses = [];
2836                                 foreach ( $uniqueIndexes as $index ) {
2837                                         $indexColumns = (array)$index;
2838                                         $indexRowValues = array_intersect_key( $row, array_flip( $indexColumns ) );
2839                                         if ( count( $indexRowValues ) != count( $indexColumns ) ) {
2840                                                 throw new DBUnexpectedError(
2841                                                         $this,
2842                                                         'New record does not provide all values for unique key (' .
2843                                                         implode( ', ', $indexColumns ) . ')'
2844                                                 );
2845                                         } elseif ( in_array( null, $indexRowValues, true ) ) {
2846                                                 throw new DBUnexpectedError(
2847                                                         $this,
2848                                                         'New record has a null value for unique key (' .
2849                                                         implode( ', ', $indexColumns ) . ')'
2850                                                 );
2851                                         }
2852                                         $indexWhereClauses[] = $this->makeList( $indexRowValues, LIST_AND );
2853                                 }
2854
2855                                 if ( $indexWhereClauses ) {
2856                                         $this->delete( $table, $this->makeList( $indexWhereClauses, LIST_OR ), $fname );
2857                                         $affectedRowCount += $this->affectedRows();
2858                                 }
2859
2860                                 // Now insert the row
2861                                 $this->insert( $table, $row, $fname );
2862                                 $affectedRowCount += $this->affectedRows();
2863                         }
2864                         $this->endAtomic( $fname );
2865                         $this->affectedRowCount = $affectedRowCount;
2866                 } catch ( Exception $e ) {
2867                         $this->cancelAtomic( $fname );
2868                         throw $e;
2869                 }
2870         }
2871
2872         /**
2873          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2874          * statement.
2875          *
2876          * @param string $table Table name
2877          * @param array|string $rows Row(s) to insert
2878          * @param string $fname Caller function name
2879          */
2880         protected function nativeReplace( $table, $rows, $fname ) {
2881                 $table = $this->tableName( $table );
2882
2883                 # Single row case
2884                 if ( !is_array( reset( $rows ) ) ) {
2885                         $rows = [ $rows ];
2886                 }
2887
2888                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2889                 $first = true;
2890
2891                 foreach ( $rows as $row ) {
2892                         if ( $first ) {
2893                                 $first = false;
2894                         } else {
2895                                 $sql .= ',';
2896                         }
2897
2898                         $sql .= '(' . $this->makeList( $row ) . ')';
2899                 }
2900
2901                 $this->query( $sql, $fname );
2902         }
2903
2904         public function upsert( $table, array $rows, $uniqueIndexes, array $set,
2905                 $fname = __METHOD__
2906         ) {
2907                 if ( $rows === [] ) {
2908                         return true; // nothing to do
2909                 }
2910
2911                 $uniqueIndexes = (array)$uniqueIndexes;
2912                 if ( !is_array( reset( $rows ) ) ) {
2913                         $rows = [ $rows ];
2914                 }
2915
2916                 if ( count( $uniqueIndexes ) ) {
2917                         $clauses = []; // list WHERE clauses that each identify a single row
2918                         foreach ( $rows as $row ) {
2919                                 foreach ( $uniqueIndexes as $index ) {
2920                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2921                                         $rowKey = []; // unique key to this row
2922                                         foreach ( $index as $column ) {
2923                                                 $rowKey[$column] = $row[$column];
2924                                         }
2925                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2926                                 }
2927                         }
2928                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2929                 } else {
2930                         $where = false;
2931                 }
2932
2933                 $affectedRowCount = 0;
2934                 try {
2935                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2936                         # Update any existing conflicting row(s)
2937                         if ( $where !== false ) {
2938                                 $this->update( $table, $set, $where, $fname );
2939                                 $affectedRowCount += $this->affectedRows();
2940                         }
2941                         # Now insert any non-conflicting row(s)
2942                         $this->insert( $table, $rows, $fname, [ 'IGNORE' ] );
2943                         $affectedRowCount += $this->affectedRows();
2944                         $this->endAtomic( $fname );
2945                         $this->affectedRowCount = $affectedRowCount;
2946                 } catch ( Exception $e ) {
2947                         $this->cancelAtomic( $fname );
2948                         throw $e;
2949                 }
2950
2951                 return true;
2952         }
2953
2954         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2955                 $fname = __METHOD__
2956         ) {
2957                 if ( !$conds ) {
2958                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2959                 }
2960
2961                 $delTable = $this->tableName( $delTable );
2962                 $joinTable = $this->tableName( $joinTable );
2963                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2964                 if ( $conds != '*' ) {
2965                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2966                 }
2967                 $sql .= ')';
2968
2969                 $this->query( $sql, $fname );
2970         }
2971
2972         public function textFieldSize( $table, $field ) {
2973                 $table = $this->tableName( $table );
2974                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2975                 $res = $this->query( $sql, __METHOD__ );
2976                 $row = $this->fetchObject( $res );
2977
2978                 $m = [];
2979
2980                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2981                         $size = $m[1];
2982                 } else {
2983                         $size = -1;
2984                 }
2985
2986                 return $size;
2987         }
2988
2989         public function delete( $table, $conds, $fname = __METHOD__ ) {
2990                 if ( !$conds ) {
2991                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2992                 }
2993
2994                 $table = $this->tableName( $table );
2995                 $sql = "DELETE FROM $table";
2996
2997                 if ( $conds != '*' ) {
2998                         if ( is_array( $conds ) ) {
2999                                 $conds = $this->makeList( $conds, self::LIST_AND );
3000                         }
3001                         $sql .= ' WHERE ' . $conds;
3002                 }
3003
3004                 $this->query( $sql, $fname );
3005
3006                 return true;
3007         }
3008
3009         final public function insertSelect(
3010                 $destTable, $srcTable, $varMap, $conds,
3011                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
3012         ) {
3013                 static $hints = [ 'NO_AUTO_COLUMNS' ];
3014
3015                 $insertOptions = (array)$insertOptions;
3016                 $selectOptions = (array)$selectOptions;
3017
3018                 if ( $this->cliMode && $this->isInsertSelectSafe( $insertOptions, $selectOptions ) ) {
3019                         // For massive migrations with downtime, we don't want to select everything
3020                         // into memory and OOM, so do all this native on the server side if possible.
3021                         $this->nativeInsertSelect(
3022                                 $destTable,
3023                                 $srcTable,
3024                                 $varMap,
3025                                 $conds,
3026                                 $fname,
3027                                 array_diff( $insertOptions, $hints ),
3028                                 $selectOptions,
3029                                 $selectJoinConds
3030                         );
3031                 } else {
3032                         $this->nonNativeInsertSelect(
3033                                 $destTable,
3034                                 $srcTable,
3035                                 $varMap,
3036                                 $conds,
3037                                 $fname,
3038                                 array_diff( $insertOptions, $hints ),
3039                                 $selectOptions,
3040                                 $selectJoinConds
3041                         );
3042                 }
3043
3044                 return true;
3045         }
3046
3047         /**
3048          * @param array $insertOptions INSERT options
3049          * @param array $selectOptions SELECT options
3050          * @return bool Whether an INSERT SELECT with these options will be replication safe
3051          * @since 1.31
3052          */
3053         protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
3054                 return true;
3055         }
3056
3057         /**
3058          * Implementation of insertSelect() based on select() and insert()
3059          *
3060          * @see IDatabase::insertSelect()
3061          * @since 1.30
3062          * @param string $destTable
3063          * @param string|array $srcTable
3064          * @param array $varMap
3065          * @param array $conds
3066          * @param string $fname
3067          * @param array $insertOptions
3068          * @param array $selectOptions
3069          * @param array $selectJoinConds
3070          */
3071         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
3072                 $fname = __METHOD__,
3073                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
3074         ) {
3075                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
3076                 // on only the master (without needing row-based-replication). It also makes it easy to
3077                 // know how big the INSERT is going to be.
3078                 $fields = [];
3079                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
3080                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
3081                 }
3082                 $selectOptions[] = 'FOR UPDATE';
3083                 $res = $this->select(
3084                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
3085                 );
3086                 if ( !$res ) {
3087                         return;
3088                 }
3089
3090                 try {
3091                         $affectedRowCount = 0;
3092                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
3093                         $rows = [];
3094                         $ok = true;
3095                         foreach ( $res as $row ) {
3096                                 $rows[] = (array)$row;
3097
3098                                 // Avoid inserts that are too huge
3099                                 if ( count( $rows ) >= $this->nonNativeInsertSelectBatchSize ) {
3100                                         $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
3101                                         if ( !$ok ) {
3102                                                 break;
3103                                         }
3104                                         $affectedRowCount += $this->affectedRows();
3105                                         $rows = [];
3106                                 }
3107                         }
3108                         if ( $rows && $ok ) {
3109                                 $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
3110                                 if ( $ok ) {
3111                                         $affectedRowCount += $this->affectedRows();
3112                                 }
3113                         }
3114                         if ( $ok ) {
3115                                 $this->endAtomic( $fname );
3116                                 $this->affectedRowCount = $affectedRowCount;
3117                         } else {
3118                                 $this->cancelAtomic( $fname );
3119                         }
3120                 } catch ( Exception $e ) {
3121                         $this->cancelAtomic( $fname );
3122                         throw $e;
3123                 }
3124         }
3125
3126         /**
3127          * Native server-side implementation of insertSelect() for situations where
3128          * we don't want to select everything into memory
3129          *
3130          * @see IDatabase::insertSelect()
3131          * @param string $destTable
3132          * @param string|array $srcTable
3133          * @param array $varMap
3134          * @param array $conds
3135          * @param string $fname
3136          * @param array $insertOptions
3137          * @param array $selectOptions
3138          * @param array $selectJoinConds
3139          */
3140         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
3141                 $fname = __METHOD__,
3142                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
3143         ) {
3144                 $destTable = $this->tableName( $destTable );
3145
3146                 if ( !is_array( $insertOptions ) ) {
3147                         $insertOptions = [ $insertOptions ];
3148                 }
3149
3150                 $insertOptions = $this->makeInsertOptions( $insertOptions );
3151
3152                 $selectSql = $this->selectSQLText(
3153                         $srcTable,
3154                         array_values( $varMap ),
3155                         $conds,
3156                         $fname,
3157                         $selectOptions,
3158                         $selectJoinConds
3159                 );
3160
3161                 $sql = "INSERT $insertOptions" .
3162                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
3163                         $selectSql;
3164
3165                 $this->query( $sql, $fname );
3166         }
3167
3168         /**
3169          * Construct a LIMIT query with optional offset. This is used for query
3170          * pages. The SQL should be adjusted so that only the first $limit rows
3171          * are returned. If $offset is provided as well, then the first $offset
3172          * rows should be discarded, and the next $limit rows should be returned.
3173          * If the result of the query is not ordered, then the rows to be returned
3174          * are theoretically arbitrary.
3175          *
3176          * $sql is expected to be a SELECT, if that makes a difference.
3177          *
3178          * The version provided by default works in MySQL and SQLite. It will very
3179          * likely need to be overridden for most other DBMSes.
3180          *
3181          * @param string $sql SQL query we will append the limit too
3182          * @param int $limit The SQL limit
3183          * @param int|bool $offset The SQL offset (default false)
3184          * @throws DBUnexpectedError
3185          * @return string
3186          */
3187         public function limitResult( $sql, $limit, $offset = false ) {
3188                 if ( !is_numeric( $limit ) ) {
3189                         throw new DBUnexpectedError( $this,
3190                                 "Invalid non-numeric limit passed to limitResult()\n" );
3191                 }
3192
3193                 return "$sql LIMIT "
3194                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
3195                 . "{$limit} ";
3196         }
3197
3198         public function unionSupportsOrderAndLimit() {
3199                 return true; // True for almost every DB supported
3200         }
3201
3202         public function unionQueries( $sqls, $all ) {
3203                 $glue = $all ? ') UNION ALL (' : ') UNION (';
3204
3205                 return '(' . implode( $glue, $sqls ) . ')';
3206         }
3207
3208         public function unionConditionPermutations(
3209                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
3210                 $options = [], $join_conds = []
3211         ) {
3212                 // First, build the Cartesian product of $permute_conds
3213                 $conds = [ [] ];
3214                 foreach ( $permute_conds as $field => $values ) {
3215                         if ( !$values ) {
3216                                 // Skip empty $values
3217                                 continue;
3218                         }
3219                         $values = array_unique( $values ); // For sanity
3220                         $newConds = [];
3221                         foreach ( $conds as $cond ) {
3222                                 foreach ( $values as $value ) {
3223                                         $cond[$field] = $value;
3224                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
3225                                 }
3226                         }
3227                         $conds = $newConds;
3228                 }
3229
3230                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
3231
3232                 // If there's just one condition and no subordering, hand off to
3233                 // selectSQLText directly.
3234                 if ( count( $conds ) === 1 &&
3235                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
3236                 ) {
3237                         return $this->selectSQLText(
3238                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
3239                         );
3240                 }
3241
3242                 // Otherwise, we need to pull out the order and limit to apply after
3243                 // the union. Then build the SQL queries for each set of conditions in
3244                 // $conds. Then union them together (using UNION ALL, because the
3245                 // product *should* already be distinct).
3246                 $orderBy = $this->makeOrderBy( $options );
3247                 $limit = $options['LIMIT'] ?? null;
3248                 $offset = $options['OFFSET'] ?? false;
3249                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
3250                 if ( !$this->unionSupportsOrderAndLimit() ) {
3251                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
3252                 } else {
3253                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
3254                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
3255                         }
3256                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
3257                                 // We need to increase the limit by the offset rather than
3258                                 // using the offset directly, otherwise it'll skip incorrectly
3259                                 // in the subqueries.
3260                                 $options['LIMIT'] = $limit + $offset;
3261                                 unset( $options['OFFSET'] );
3262                         }
3263                 }
3264
3265                 $sqls = [];
3266                 foreach ( $conds as $cond ) {
3267                         $sqls[] = $this->selectSQLText(
3268                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
3269                         );
3270                 }
3271                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
3272                 if ( $limit !== null ) {
3273                         $sql = $this->limitResult( $sql, $limit, $offset );
3274                 }
3275
3276                 return $sql;
3277         }
3278
3279         public function conditional( $cond, $trueVal, $falseVal ) {
3280                 if ( is_array( $cond ) ) {
3281                         $cond = $this->makeList( $cond, self::LIST_AND );
3282                 }
3283
3284                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
3285         }
3286
3287         public function strreplace( $orig, $old, $new ) {
3288                 return "REPLACE({$orig}, {$old}, {$new})";
3289         }
3290
3291         public function getServerUptime() {
3292                 return 0;
3293         }
3294
3295         public function wasDeadlock() {
3296                 return false;
3297         }
3298
3299         public function wasLockTimeout() {
3300                 return false;
3301         }
3302
3303         public function wasConnectionLoss() {
3304                 return $this->wasConnectionError( $this->lastErrno() );
3305         }
3306
3307         public function wasReadOnlyError() {
3308                 return false;
3309         }
3310
3311         public function wasErrorReissuable() {
3312                 return (
3313                         $this->wasDeadlock() ||
3314                         $this->wasLockTimeout() ||
3315                         $this->wasConnectionLoss()
3316                 );
3317         }
3318
3319         /**
3320          * Do not use this method outside of Database/DBError classes
3321          *
3322          * @param int|string $errno
3323          * @return bool Whether the given query error was a connection drop
3324          */
3325         public function wasConnectionError( $errno ) {
3326                 return false;
3327         }
3328
3329         /**
3330          * @return bool Whether it is known that the last query error only caused statement rollback
3331          * @note This is for backwards compatibility for callers catching DBError exceptions in
3332          *   order to ignore problems like duplicate key errors or foriegn key violations
3333          * @since 1.31
3334          */
3335         protected function wasKnownStatementRollbackError() {
3336                 return false; // don't know; it could have caused a transaction rollback
3337         }
3338
3339         public function deadlockLoop() {
3340                 $args = func_get_args();
3341                 $function = array_shift( $args );
3342                 $tries = self::DEADLOCK_TRIES;
3343
3344                 $this->begin( __METHOD__ );
3345
3346                 $retVal = null;
3347                 /** @var Exception $e */
3348                 $e = null;
3349                 do {
3350                         try {
3351                                 $retVal = $function( ...$args );
3352                                 break;
3353                         } catch ( DBQueryError $e ) {
3354                                 if ( $this->wasDeadlock() ) {
3355                                         // Retry after a randomized delay
3356                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3357                                 } else {
3358                                         // Throw the error back up
3359                                         throw $e;
3360                                 }
3361                         }
3362                 } while ( --$tries > 0 );
3363
3364                 if ( $tries <= 0 ) {
3365                         // Too many deadlocks; give up
3366                         $this->rollback( __METHOD__ );
3367                         throw $e;
3368                 } else {
3369                         $this->commit( __METHOD__ );
3370
3371                         return $retVal;
3372                 }
3373         }
3374
3375         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3376                 # Real waits are implemented in the subclass.
3377                 return 0;
3378         }
3379
3380         public function getReplicaPos() {
3381                 # Stub
3382                 return false;
3383         }
3384
3385         public function getMasterPos() {
3386                 # Stub
3387                 return false;
3388         }
3389
3390         public function serverIsReadOnly() {
3391                 return false;
3392         }
3393
3394         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
3395                 if ( !$this->trxLevel ) {
3396                         throw new DBUnexpectedError( $this, "No transaction is active." );
3397                 }
3398                 $this->trxEndCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3399         }
3400
3401         final public function onTransactionCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
3402                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3403                         // Start an implicit transaction similar to how query() does
3404                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3405                         $this->trxAutomatic = true;
3406                 }
3407
3408                 $this->trxIdleCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3409                 if ( !$this->trxLevel ) {
3410                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
3411                 }
3412         }
3413
3414         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
3415                 $this->onTransactionCommitOrIdle( $callback, $fname );
3416         }
3417
3418         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
3419                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3420                         // Start an implicit transaction similar to how query() does
3421                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3422                         $this->trxAutomatic = true;
3423                 }
3424
3425                 if ( $this->trxLevel ) {
3426                         $this->trxPreCommitCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3427                 } else {
3428                         // No transaction is active nor will start implicitly, so make one for this callback
3429                         $this->startAtomic( __METHOD__, self::ATOMIC_CANCELABLE );
3430                         try {
3431                                 $callback( $this );
3432                                 $this->endAtomic( __METHOD__ );
3433                         } catch ( Exception $e ) {
3434                                 $this->cancelAtomic( __METHOD__ );
3435                                 throw $e;
3436                         }
3437                 }
3438         }
3439
3440         /**
3441          * @return AtomicSectionIdentifier|null ID of the topmost atomic section level
3442          */
3443         private function currentAtomicSectionId() {
3444                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3445                         $levelInfo = end( $this->trxAtomicLevels );
3446
3447                         return $levelInfo[1];
3448                 }
3449
3450                 return null;
3451         }
3452
3453         /**
3454          * @param AtomicSectionIdentifier $old
3455          * @param AtomicSectionIdentifier $new
3456          */
3457         private function reassignCallbacksForSection(
3458                 AtomicSectionIdentifier $old, AtomicSectionIdentifier $new
3459         ) {
3460                 foreach ( $this->trxPreCommitCallbacks as $key => $info ) {
3461                         if ( $info[2] === $old ) {
3462                                 $this->trxPreCommitCallbacks[$key][2] = $new;
3463                         }
3464                 }
3465                 foreach ( $this->trxIdleCallbacks as $key => $info ) {
3466                         if ( $info[2] === $old ) {
3467                                 $this->trxIdleCallbacks[$key][2] = $new;
3468                         }
3469                 }
3470                 foreach ( $this->trxEndCallbacks as $key => $info ) {
3471                         if ( $info[2] === $old ) {
3472                                 $this->trxEndCallbacks[$key][2] = $new;
3473                         }
3474                 }
3475         }
3476
3477         /**
3478          * @param AtomicSectionIdentifier[] $sectionIds ID of an actual savepoint
3479          * @throws UnexpectedValueException
3480          */
3481         private function modifyCallbacksForCancel( array $sectionIds ) {
3482                 // Cancel the "on commit" callbacks owned by this savepoint
3483                 $this->trxIdleCallbacks = array_filter(
3484                         $this->trxIdleCallbacks,
3485                         function ( $entry ) use ( $sectionIds ) {
3486                                 return !in_array( $entry[2], $sectionIds, true );
3487                         }
3488                 );
3489                 $this->trxPreCommitCallbacks = array_filter(
3490                         $this->trxPreCommitCallbacks,
3491                         function ( $entry ) use ( $sectionIds ) {
3492                                 return !in_array( $entry[2], $sectionIds, true );
3493                         }
3494                 );
3495                 // Make "on resolution" callbacks owned by this savepoint to perceive a rollback
3496                 foreach ( $this->trxEndCallbacks as $key => $entry ) {
3497                         if ( in_array( $entry[2], $sectionIds, true ) ) {
3498                                 $callback = $entry[0];
3499                                 $this->trxEndCallbacks[$key][0] = function () use ( $callback ) {
3500                                         return $callback( self::TRIGGER_ROLLBACK, $this );
3501                                 };
3502                         }
3503                 }
3504         }
3505
3506         final public function setTransactionListener( $name, callable $callback = null ) {
3507                 if ( $callback ) {
3508                         $this->trxRecurringCallbacks[$name] = $callback;
3509                 } else {
3510                         unset( $this->trxRecurringCallbacks[$name] );
3511                 }
3512         }
3513
3514         /**
3515          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
3516          *
3517          * This method should not be used outside of Database/LoadBalancer
3518          *
3519          * @param bool $suppress
3520          * @since 1.28
3521          */
3522         final public function setTrxEndCallbackSuppression( $suppress ) {
3523                 $this->trxEndCallbacksSuppressed = $suppress;
3524         }
3525
3526         /**
3527          * Actually consume and run any "on transaction idle/resolution" callbacks.
3528          *
3529          * This method should not be used outside of Database/LoadBalancer
3530          *
3531          * @param int $trigger IDatabase::TRIGGER_* constant
3532          * @return int Number of callbacks attempted
3533          * @since 1.20
3534          * @throws Exception
3535          */
3536         public function runOnTransactionIdleCallbacks( $trigger ) {
3537                 if ( $this->trxLevel ) { // sanity
3538                         throw new DBUnexpectedError( $this, __METHOD__ . ': a transaction is still open.' );
3539                 }
3540
3541                 if ( $this->trxEndCallbacksSuppressed ) {
3542                         return 0;
3543                 }
3544
3545                 $count = 0;
3546                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
3547                 /** @var Exception $e */
3548                 $e = null; // first exception
3549                 do { // callbacks may add callbacks :)
3550                         $callbacks = array_merge(
3551                                 $this->trxIdleCallbacks,
3552                                 $this->trxEndCallbacks // include "transaction resolution" callbacks
3553                         );
3554                         $this->trxIdleCallbacks = []; // consumed (and recursion guard)
3555                         $this->trxEndCallbacks = []; // consumed (recursion guard)
3556                         foreach ( $callbacks as $callback ) {
3557                                 ++$count;
3558                                 list( $phpCallback ) = $callback;
3559                                 $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
3560                                 try {
3561                                         call_user_func( $phpCallback, $trigger, $this );
3562                                 } catch ( Exception $ex ) {
3563                                         call_user_func( $this->errorLogger, $ex );
3564                                         $e = $e ?: $ex;
3565                                         // Some callbacks may use startAtomic/endAtomic, so make sure
3566                                         // their transactions are ended so other callbacks don't fail
3567                                         if ( $this->trxLevel() ) {
3568                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
3569                                         }
3570                                 } finally {
3571                                         if ( $autoTrx ) {
3572                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
3573                                         } else {
3574                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
3575                                         }
3576                                 }
3577                         }
3578                 } while ( count( $this->trxIdleCallbacks ) );
3579
3580                 if ( $e instanceof Exception ) {
3581                         throw $e; // re-throw any first exception
3582                 }
3583
3584                 return $count;
3585         }
3586
3587         /**
3588          * Actually consume and run any "on transaction pre-commit" callbacks.
3589          *
3590          * This method should not be used outside of Database/LoadBalancer
3591          *
3592          * @since 1.22
3593          * @return int Number of callbacks attempted
3594          * @throws Exception
3595          */
3596         public function runOnTransactionPreCommitCallbacks() {
3597                 $count = 0;
3598
3599                 $e = null; // first exception
3600                 do { // callbacks may add callbacks :)
3601                         $callbacks = $this->trxPreCommitCallbacks;
3602                         $this->trxPreCommitCallbacks = []; // consumed (and recursion guard)
3603                         foreach ( $callbacks as $callback ) {
3604                                 try {
3605                                         ++$count;
3606                                         list( $phpCallback ) = $callback;
3607                                         $phpCallback( $this );
3608                                 } catch ( Exception $ex ) {
3609                                         ( $this->errorLogger )( $ex );
3610                                         $e = $e ?: $ex;
3611                                 }
3612                         }
3613                 } while ( count( $this->trxPreCommitCallbacks ) );
3614
3615                 if ( $e instanceof Exception ) {
3616                         throw $e; // re-throw any first exception
3617                 }
3618
3619                 return $count;
3620         }
3621
3622         /**
3623          * Actually run any "transaction listener" callbacks.
3624          *
3625          * This method should not be used outside of Database/LoadBalancer
3626          *
3627          * @param int $trigger IDatabase::TRIGGER_* constant
3628          * @throws Exception
3629          * @since 1.20
3630          */
3631         public function runTransactionListenerCallbacks( $trigger ) {
3632                 if ( $this->trxEndCallbacksSuppressed ) {
3633                         return;
3634                 }
3635
3636                 /** @var Exception $e */
3637                 $e = null; // first exception
3638
3639                 foreach ( $this->trxRecurringCallbacks as $phpCallback ) {
3640                         try {
3641                                 $phpCallback( $trigger, $this );
3642                         } catch ( Exception $ex ) {
3643                                 ( $this->errorLogger )( $ex );
3644                                 $e = $e ?: $ex;
3645                         }
3646                 }
3647
3648                 if ( $e instanceof Exception ) {
3649                         throw $e; // re-throw any first exception
3650                 }
3651         }
3652
3653         /**
3654          * Create a savepoint
3655          *
3656          * This is used internally to implement atomic sections. It should not be
3657          * used otherwise.
3658          *
3659          * @since 1.31
3660          * @param string $identifier Identifier for the savepoint
3661          * @param string $fname Calling function name
3662          */
3663         protected function doSavepoint( $identifier, $fname ) {
3664                 $this->query( 'SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3665         }
3666
3667         /**
3668          * Release a savepoint
3669          *
3670          * This is used internally to implement atomic sections. It should not be
3671          * used otherwise.
3672          *
3673          * @since 1.31
3674          * @param string $identifier Identifier for the savepoint
3675          * @param string $fname Calling function name
3676          */
3677         protected function doReleaseSavepoint( $identifier, $fname ) {
3678                 $this->query( 'RELEASE SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3679         }
3680
3681         /**
3682          * Rollback to a savepoint
3683          *
3684          * This is used internally to implement atomic sections. It should not be
3685          * used otherwise.
3686          *
3687          * @since 1.31
3688          * @param string $identifier Identifier for the savepoint
3689          * @param string $fname Calling function name
3690          */
3691         protected function doRollbackToSavepoint( $identifier, $fname ) {
3692                 $this->query( 'ROLLBACK TO SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3693         }
3694
3695         /**
3696          * @param string $fname
3697          * @return string
3698          */
3699         private function nextSavepointId( $fname ) {
3700                 $savepointId = self::$SAVEPOINT_PREFIX . ++$this->trxAtomicCounter;
3701                 if ( strlen( $savepointId ) > 30 ) {
3702                         // 30 == Oracle's identifier length limit (pre 12c)
3703                         // With a 22 character prefix, that puts the highest number at 99999999.
3704                         throw new DBUnexpectedError(
3705                                 $this,
3706                                 'There have been an excessively large number of atomic sections in a transaction'
3707                                 . " started by $this->trxFname (at $fname)"
3708                         );
3709                 }
3710
3711                 return $savepointId;
3712         }
3713
3714         final public function startAtomic(
3715                 $fname = __METHOD__, $cancelable = self::ATOMIC_NOT_CANCELABLE
3716         ) {
3717                 $savepointId = $cancelable === self::ATOMIC_CANCELABLE ? self::$NOT_APPLICABLE : null;
3718
3719                 if ( !$this->trxLevel ) {
3720                         $this->begin( $fname, self::TRANSACTION_INTERNAL ); // sets trxAutomatic
3721                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
3722                         // in all changes being in one transaction to keep requests transactional.
3723                         if ( $this->getFlag( self::DBO_TRX ) ) {
3724                                 // Since writes could happen in between the topmost atomic sections as part
3725                                 // of the transaction, those sections will need savepoints.
3726                                 $savepointId = $this->nextSavepointId( $fname );
3727                                 $this->doSavepoint( $savepointId, $fname );
3728                         } else {
3729                                 $this->trxAutomaticAtomic = true;
3730                         }
3731                 } elseif ( $cancelable === self::ATOMIC_CANCELABLE ) {
3732                         $savepointId = $this->nextSavepointId( $fname );
3733                         $this->doSavepoint( $savepointId, $fname );
3734                 }
3735
3736                 $sectionId = new AtomicSectionIdentifier;
3737                 $this->trxAtomicLevels[] = [ $fname, $sectionId, $savepointId ];
3738                 $this->queryLogger->debug( 'startAtomic: entering level ' .
3739                         ( count( $this->trxAtomicLevels ) - 1 ) . " ($fname)" );
3740
3741                 return $sectionId;
3742         }
3743
3744         final public function endAtomic( $fname = __METHOD__ ) {
3745                 if ( !$this->trxLevel || !$this->trxAtomicLevels ) {
3746                         throw new DBUnexpectedError( $this, "No atomic section is open (got $fname)." );
3747                 }
3748
3749                 // Check if the current section matches $fname
3750                 $pos = count( $this->trxAtomicLevels ) - 1;
3751                 list( $savedFname, $sectionId, $savepointId ) = $this->trxAtomicLevels[$pos];
3752                 $this->queryLogger->debug( "endAtomic: leaving level $pos ($fname)" );
3753
3754                 if ( $savedFname !== $fname ) {
3755                         throw new DBUnexpectedError(
3756                                 $this,
3757                                 "Invalid atomic section ended (got $fname but expected $savedFname)."
3758                         );
3759                 }
3760
3761                 // Remove the last section (no need to re-index the array)
3762                 array_pop( $this->trxAtomicLevels );
3763
3764                 if ( !$this->trxAtomicLevels && $this->trxAutomaticAtomic ) {
3765                         $this->commit( $fname, self::FLUSHING_INTERNAL );
3766                 } elseif ( $savepointId !== null && $savepointId !== self::$NOT_APPLICABLE ) {
3767                         $this->doReleaseSavepoint( $savepointId, $fname );
3768                 }
3769
3770                 // Hoist callback ownership for callbacks in the section that just ended;
3771                 // all callbacks should have an owner that is present in trxAtomicLevels.
3772                 $currentSectionId = $this->currentAtomicSectionId();
3773                 if ( $currentSectionId ) {
3774                         $this->reassignCallbacksForSection( $sectionId, $currentSectionId );
3775                 }
3776         }
3777
3778         final public function cancelAtomic(
3779                 $fname = __METHOD__, AtomicSectionIdentifier $sectionId = null
3780         ) {
3781                 if ( !$this->trxLevel || !$this->trxAtomicLevels ) {
3782                         throw new DBUnexpectedError( $this, "No atomic section is open (got $fname)." );
3783                 }
3784
3785                 $excisedFnames = [];
3786                 if ( $sectionId !== null ) {
3787                         // Find the (last) section with the given $sectionId
3788                         $pos = -1;
3789                         foreach ( $this->trxAtomicLevels as $i => list( $asFname, $asId, $spId ) ) {
3790                                 if ( $asId === $sectionId ) {
3791                                         $pos = $i;
3792                                 }
3793                         }
3794                         if ( $pos < 0 ) {
3795                                 throw new DBUnexpectedError( $this, "Atomic section not found (for $fname)" );
3796                         }
3797                         // Remove all descendant sections and re-index the array
3798                         $excisedIds = [];
3799                         $len = count( $this->trxAtomicLevels );
3800                         for ( $i = $pos + 1; $i < $len; ++$i ) {
3801                                 $excisedFnames[] = $this->trxAtomicLevels[$i][0];
3802                                 $excisedIds[] = $this->trxAtomicLevels[$i][1];
3803                         }
3804                         $this->trxAtomicLevels = array_slice( $this->trxAtomicLevels, 0, $pos + 1 );
3805                         $this->modifyCallbacksForCancel( $excisedIds );
3806                 }
3807
3808                 // Check if the current section matches $fname
3809                 $pos = count( $this->trxAtomicLevels ) - 1;
3810                 list( $savedFname, $savedSectionId, $savepointId ) = $this->trxAtomicLevels[$pos];
3811
3812                 if ( $excisedFnames ) {
3813                         $this->queryLogger->debug( "cancelAtomic: canceling level $pos ($savedFname) " .
3814                                 "and descendants " . implode( ', ', $excisedFnames ) );
3815                 } else {
3816                         $this->queryLogger->debug( "cancelAtomic: canceling level $pos ($savedFname)" );
3817                 }
3818
3819                 if ( $savedFname !== $fname ) {
3820                         throw new DBUnexpectedError(
3821                                 $this,
3822                                 "Invalid atomic section ended (got $fname but expected $savedFname)."
3823                         );
3824                 }
3825
3826                 // Remove the last section (no need to re-index the array)
3827                 array_pop( $this->trxAtomicLevels );
3828                 $this->modifyCallbacksForCancel( [ $savedSectionId ] );
3829
3830                 if ( $savepointId !== null ) {
3831                         // Rollback the transaction to the state just before this atomic section
3832                         if ( $savepointId === self::$NOT_APPLICABLE ) {
3833                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
3834                         } else {
3835                                 $this->doRollbackToSavepoint( $savepointId, $fname );
3836                                 $this->trxStatus = self::STATUS_TRX_OK; // no exception; recovered
3837                                 $this->trxStatusIgnoredCause = null;
3838                         }
3839                 } elseif ( $this->trxStatus > self::STATUS_TRX_ERROR ) {
3840                         // Put the transaction into an error state if it's not already in one
3841                         $this->trxStatus = self::STATUS_TRX_ERROR;
3842                         $this->trxStatusCause = new DBUnexpectedError(
3843                                 $this,
3844                                 "Uncancelable atomic section canceled (got $fname)."
3845                         );
3846                 }
3847
3848                 $this->affectedRowCount = 0; // for the sake of consistency
3849         }
3850
3851         final public function doAtomicSection(
3852                 $fname, callable $callback, $cancelable = self::ATOMIC_NOT_CANCELABLE
3853         ) {
3854                 $sectionId = $this->startAtomic( $fname, $cancelable );
3855                 try {
3856                         $res = $callback( $this, $fname );
3857                 } catch ( Exception $e ) {
3858                         $this->cancelAtomic( $fname, $sectionId );
3859
3860                         throw $e;
3861                 }
3862                 $this->endAtomic( $fname );
3863
3864                 return $res;
3865         }
3866
3867         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
3868                 static $modes = [ self::TRANSACTION_EXPLICIT, self::TRANSACTION_INTERNAL ];
3869                 if ( !in_array( $mode, $modes, true ) ) {
3870                         throw new DBUnexpectedError( $this, "$fname: invalid mode parameter '$mode'." );
3871                 }
3872
3873                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
3874                 if ( $this->trxLevel ) {
3875                         if ( $this->trxAtomicLevels ) {
3876                                 $levels = $this->flatAtomicSectionList();
3877                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
3878                                 throw new DBUnexpectedError( $this, $msg );
3879                         } elseif ( !$this->trxAutomatic ) {
3880                                 $msg = "$fname: Explicit transaction already active (from {$this->trxFname}).";
3881                                 throw new DBUnexpectedError( $this, $msg );
3882                         } else {
3883                                 $msg = "$fname: Implicit transaction already active (from {$this->trxFname}).";
3884                                 throw new DBUnexpectedError( $this, $msg );
3885                         }
3886                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
3887                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
3888                         throw new DBUnexpectedError( $this, $msg );
3889                 }
3890
3891                 $this->assertHasConnectionHandle();
3892
3893                 $this->doBegin( $fname );
3894                 $this->trxStatus = self::STATUS_TRX_OK;
3895                 $this->trxStatusIgnoredCause = null;
3896                 $this->trxAtomicCounter = 0;
3897                 $this->trxTimestamp = microtime( true );
3898                 $this->trxFname = $fname;
3899                 $this->trxDoneWrites = false;
3900                 $this->trxAutomaticAtomic = false;
3901                 $this->trxAtomicLevels = [];
3902                 $this->trxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
3903                 $this->trxWriteDuration = 0.0;
3904                 $this->trxWriteQueryCount = 0;
3905                 $this->trxWriteAffectedRows = 0;
3906                 $this->trxWriteAdjDuration = 0.0;
3907                 $this->trxWriteAdjQueryCount = 0;
3908                 $this->trxWriteCallers = [];
3909                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
3910                 // Get an estimate of the replication lag before any such queries.
3911                 $this->trxReplicaLag = null; // clear cached value first
3912                 $this->trxReplicaLag = $this->getApproximateLagStatus()['lag'];
3913                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
3914                 // caller will think its OK to muck around with the transaction just because startAtomic()
3915                 // has not yet completed (e.g. setting trxAtomicLevels).
3916                 $this->trxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
3917         }
3918
3919         /**
3920          * Issues the BEGIN command to the database server.
3921          *
3922          * @see Database::begin()
3923          * @param string $fname
3924          */
3925         protected function doBegin( $fname ) {
3926                 $this->query( 'BEGIN', $fname );
3927                 $this->trxLevel = 1;
3928         }
3929
3930         final public function commit( $fname = __METHOD__, $flush = self::FLUSHING_ONE ) {
3931                 static $modes = [ self::FLUSHING_ONE, self::FLUSHING_ALL_PEERS, self::FLUSHING_INTERNAL ];
3932                 if ( !in_array( $flush, $modes, true ) ) {
3933                         throw new DBUnexpectedError( $this, "$fname: invalid flush parameter '$flush'." );
3934                 }
3935
3936                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3937                         // There are still atomic sections open; this cannot be ignored
3938                         $levels = $this->flatAtomicSectionList();
3939                         throw new DBUnexpectedError(
3940                                 $this,
3941                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3942                         );
3943                 }
3944
3945                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3946                         if ( !$this->trxLevel ) {
3947                                 return; // nothing to do
3948                         } elseif ( !$this->trxAutomatic ) {
3949                                 throw new DBUnexpectedError(
3950                                         $this,
3951                                         "$fname: Flushing an explicit transaction, getting out of sync."
3952                                 );
3953                         }
3954                 } else {
3955                         if ( !$this->trxLevel ) {
3956                                 $this->queryLogger->error(
3957                                         "$fname: No transaction to commit, something got out of sync." );
3958                                 return; // nothing to do
3959                         } elseif ( $this->trxAutomatic ) {
3960                                 throw new DBUnexpectedError(
3961                                         $this,
3962                                         "$fname: Expected mass commit of all peer transactions (DBO_TRX set)."
3963                                 );
3964                         }
3965                 }
3966
3967                 $this->assertHasConnectionHandle();
3968
3969                 $this->runOnTransactionPreCommitCallbacks();
3970
3971                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3972                 $this->doCommit( $fname );
3973                 $this->trxStatus = self::STATUS_TRX_NONE;
3974
3975                 if ( $this->trxDoneWrites ) {
3976                         $this->lastWriteTime = microtime( true );
3977                         $this->trxProfiler->transactionWritingOut(
3978                                 $this->server,
3979                                 $this->getDomainID(),
3980                                 $this->trxShortId,
3981                                 $writeTime,
3982                                 $this->trxWriteAffectedRows
3983                         );
3984                 }
3985
3986                 // With FLUSHING_ALL_PEERS, callbacks will be explicitly run later
3987                 if ( $flush !== self::FLUSHING_ALL_PEERS ) {
3988                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3989                         $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3990                 }
3991         }
3992
3993         /**
3994          * Issues the COMMIT command to the database server.
3995          *
3996          * @see Database::commit()
3997          * @param string $fname
3998          */
3999         protected function doCommit( $fname ) {
4000                 if ( $this->trxLevel ) {
4001                         $this->query( 'COMMIT', $fname );
4002                         $this->trxLevel = 0;
4003                 }
4004         }
4005
4006         final public function rollback( $fname = __METHOD__, $flush = '' ) {
4007                 $trxActive = $this->trxLevel;
4008
4009                 if ( $flush !== self::FLUSHING_INTERNAL && $flush !== self::FLUSHING_ALL_PEERS ) {
4010                         if ( $this->getFlag( self::DBO_TRX ) ) {
4011                                 throw new DBUnexpectedError(
4012                                         $this,
4013                                         "$fname: Expected mass rollback of all peer transactions (DBO_TRX set)."
4014                                 );
4015                         }
4016                 }
4017
4018                 if ( $trxActive ) {
4019                         $this->assertHasConnectionHandle();
4020
4021                         $this->doRollback( $fname );
4022                         $this->trxStatus = self::STATUS_TRX_NONE;
4023                         $this->trxAtomicLevels = [];
4024                         // Estimate the RTT via a query now that trxStatus is OK
4025                         $writeTime = $this->pingAndCalculateLastTrxApplyTime();
4026
4027                         if ( $this->trxDoneWrites ) {
4028                                 $this->trxProfiler->transactionWritingOut(
4029                                         $this->server,
4030                                         $this->getDomainID(),
4031                                         $this->trxShortId,
4032                                         $writeTime,
4033                                         $this->trxWriteAffectedRows
4034                                 );
4035                         }
4036                 }
4037
4038                 // Clear any commit-dependant callbacks. They might even be present
4039                 // only due to transaction rounds, with no SQL transaction being active
4040                 $this->trxIdleCallbacks = [];
4041                 $this->trxPreCommitCallbacks = [];
4042
4043                 // With FLUSHING_ALL_PEERS, callbacks will be explicitly run later
4044                 if ( $trxActive && $flush !== self::FLUSHING_ALL_PEERS ) {
4045                         try {
4046                                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
4047                         } catch ( Exception $e ) {
4048                                 // already logged; finish and let LoadBalancer move on during mass-rollback
4049                         }
4050                         try {
4051                                 $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
4052                         } catch ( Exception $e ) {
4053                                 // already logged; let LoadBalancer move on during mass-rollback
4054                         }
4055
4056                         $this->affectedRowCount = 0; // for the sake of consistency
4057                 }
4058         }
4059
4060         /**
4061          * Issues the ROLLBACK command to the database server.
4062          *
4063          * @see Database::rollback()
4064          * @param string $fname
4065          */
4066         protected function doRollback( $fname ) {
4067                 if ( $this->trxLevel ) {
4068                         # Disconnects cause rollback anyway, so ignore those errors
4069                         $ignoreErrors = true;
4070                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
4071                         $this->trxLevel = 0;
4072                 }
4073         }
4074
4075         public function flushSnapshot( $fname = __METHOD__ ) {
4076                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
4077                         // This only flushes transactions to clear snapshots, not to write data
4078                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
4079                         throw new DBUnexpectedError(
4080                                 $this,
4081                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
4082                         );
4083                 }
4084
4085                 $this->commit( $fname, self::FLUSHING_INTERNAL );
4086         }
4087
4088         public function explicitTrxActive() {
4089                 return $this->trxLevel && ( $this->trxAtomicLevels || !$this->trxAutomatic );
4090         }
4091
4092         public function duplicateTableStructure(
4093                 $oldName, $newName, $temporary = false, $fname = __METHOD__
4094         ) {
4095                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4096         }
4097
4098         public function listTables( $prefix = null, $fname = __METHOD__ ) {
4099                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4100         }
4101
4102         public function listViews( $prefix = null, $fname = __METHOD__ ) {
4103                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4104         }
4105
4106         public function timestamp( $ts = 0 ) {
4107                 $t = new ConvertibleTimestamp( $ts );
4108                 // Let errors bubble up to avoid putting garbage in the DB
4109                 return $t->getTimestamp( TS_MW );
4110         }
4111
4112         public function timestampOrNull( $ts = null ) {
4113                 if ( is_null( $ts ) ) {
4114                         return null;
4115                 } else {
4116                         return $this->timestamp( $ts );
4117                 }
4118         }
4119
4120         public function affectedRows() {
4121                 return ( $this->affectedRowCount === null )
4122                         ? $this->fetchAffectedRowCount() // default to driver value
4123                         : $this->affectedRowCount;
4124         }
4125
4126         /**
4127          * @return int Number of retrieved rows according to the driver
4128          */
4129         abstract protected function fetchAffectedRowCount();
4130
4131         /**
4132          * Take the result from a query, and wrap it in a ResultWrapper if
4133          * necessary. Boolean values are passed through as is, to indicate success
4134          * of write queries or failure.
4135          *
4136          * Once upon a time, Database::query() returned a bare MySQL result
4137          * resource, and it was necessary to call this function to convert it to
4138          * a wrapper. Nowadays, raw database objects are never exposed to external
4139          * callers, so this is unnecessary in external code.
4140          *
4141          * @param bool|ResultWrapper|resource $result
4142          * @return bool|ResultWrapper
4143          */
4144         protected function resultObject( $result ) {
4145                 if ( !$result ) {
4146                         return false;
4147                 } elseif ( $result instanceof ResultWrapper ) {
4148                         return $result;
4149                 } elseif ( $result === true ) {
4150                         // Successful write query
4151                         return $result;
4152                 } else {
4153                         return new ResultWrapper( $this, $result );
4154                 }
4155         }
4156
4157         public function ping( &$rtt = null ) {
4158                 // Avoid hitting the server if it was hit recently
4159                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
4160                         if ( !func_num_args() || $this->rttEstimate > 0 ) {
4161                                 $rtt = $this->rttEstimate;
4162                                 return true; // don't care about $rtt
4163                         }
4164                 }
4165
4166                 // This will reconnect if possible or return false if not
4167                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
4168                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
4169                 $this->restoreFlags( self::RESTORE_PRIOR );
4170
4171                 if ( $ok ) {
4172                         $rtt = $this->rttEstimate;
4173                 }
4174
4175                 return $ok;
4176         }
4177
4178         /**
4179          * Close any existing (dead) database connection and open a new connection
4180          *
4181          * @param string $fname
4182          * @return bool True if new connection is opened successfully, false if error
4183          */
4184         protected function replaceLostConnection( $fname ) {
4185                 $this->closeConnection();
4186                 $this->opened = false;
4187                 $this->conn = false;
4188
4189                 $this->handleSessionLossPreconnect();
4190
4191                 try {
4192                         $this->open(
4193                                 $this->server,
4194                                 $this->user,
4195                                 $this->password,
4196                                 $this->getDBname(),
4197                                 $this->dbSchema(),
4198                                 $this->tablePrefix()
4199                         );
4200                         $this->lastPing = microtime( true );
4201                         $ok = true;
4202
4203                         $this->connLogger->warning(
4204                                 $fname . ': lost connection to {dbserver}; reconnected',
4205                                 [
4206                                         'dbserver' => $this->getServer(),
4207                                         'trace' => ( new RuntimeException() )->getTraceAsString()
4208                                 ]
4209                         );
4210                 } catch ( DBConnectionError $e ) {
4211                         $ok = false;
4212
4213                         $this->connLogger->error(
4214                                 $fname . ': lost connection to {dbserver} permanently',
4215                                 [ 'dbserver' => $this->getServer() ]
4216                         );
4217                 }
4218
4219                 $this->handleSessionLossPostconnect();
4220
4221                 return $ok;
4222         }
4223
4224         public function getSessionLagStatus() {
4225                 return $this->getRecordedTransactionLagStatus() ?: $this->getApproximateLagStatus();
4226         }
4227
4228         /**
4229          * Get the replica DB lag when the current transaction started
4230          *
4231          * This is useful when transactions might use snapshot isolation
4232          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
4233          * is this lag plus transaction duration. If they don't, it is still
4234          * safe to be pessimistic. This returns null if there is no transaction.
4235          *
4236          * This returns null if the lag status for this transaction was not yet recorded.
4237          *
4238          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
4239          * @since 1.27
4240          */
4241         final protected function getRecordedTransactionLagStatus() {
4242                 return ( $this->trxLevel && $this->trxReplicaLag !== null )
4243                         ? [ 'lag' => $this->trxReplicaLag, 'since' => $this->trxTimestamp() ]
4244                         : null;
4245         }
4246
4247         /**
4248          * Get a replica DB lag estimate for this server
4249          *
4250          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
4251          * @since 1.27
4252          */
4253         protected function getApproximateLagStatus() {
4254                 return [
4255                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
4256                         'since' => microtime( true )
4257                 ];
4258         }
4259
4260         /**
4261          * Merge the result of getSessionLagStatus() for several DBs
4262          * using the most pessimistic values to estimate the lag of
4263          * any data derived from them in combination
4264          *
4265          * This is information is useful for caching modules
4266          *
4267          * @see WANObjectCache::set()
4268          * @see WANObjectCache::getWithSetCallback()
4269          *
4270          * @param IDatabase $db1
4271          * @param IDatabase|null $db2 [optional]
4272          * @return array Map of values:
4273          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
4274          *   - since: oldest UNIX timestamp of any of the DB lag estimates
4275          *   - pending: whether any of the DBs have uncommitted changes
4276          * @throws DBError
4277          * @since 1.27
4278          */
4279         public static function getCacheSetOptions( IDatabase $db1, IDatabase $db2 = null ) {
4280                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
4281                 foreach ( func_get_args() as $db ) {
4282                         /** @var IDatabase $db */
4283                         $status = $db->getSessionLagStatus();
4284                         if ( $status['lag'] === false ) {
4285                                 $res['lag'] = false;
4286                         } elseif ( $res['lag'] !== false ) {
4287                                 $res['lag'] = max( $res['lag'], $status['lag'] );
4288                         }
4289                         $res['since'] = min( $res['since'], $status['since'] );
4290                         $res['pending'] = $res['pending'] ?: $db->writesPending();
4291                 }
4292
4293                 return $res;
4294         }
4295
4296         public function getLag() {
4297                 return 0;
4298         }
4299
4300         public function maxListLen() {
4301                 return 0;
4302         }
4303
4304         public function encodeBlob( $b ) {
4305                 return $b;
4306         }
4307
4308         public function decodeBlob( $b ) {
4309                 if ( $b instanceof Blob ) {
4310                         $b = $b->fetch();
4311                 }
4312                 return $b;
4313         }
4314
4315         public function setSessionOptions( array $options ) {
4316         }
4317
4318         public function sourceFile(
4319                 $filename,
4320                 callable $lineCallback = null,
4321                 callable $resultCallback = null,
4322                 $fname = false,
4323                 callable $inputCallback = null
4324         ) {
4325                 Wikimedia\suppressWarnings();
4326                 $fp = fopen( $filename, 'r' );
4327                 Wikimedia\restoreWarnings();
4328
4329                 if ( $fp === false ) {
4330                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
4331                 }
4332
4333                 if ( !$fname ) {
4334                         $fname = __METHOD__ . "( $filename )";
4335                 }
4336
4337                 try {
4338                         $error = $this->sourceStream(
4339                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
4340                 } catch ( Exception $e ) {
4341                         fclose( $fp );
4342                         throw $e;
4343                 }
4344
4345                 fclose( $fp );
4346
4347                 return $error;
4348         }
4349
4350         public function setSchemaVars( $vars ) {
4351                 $this->schemaVars = $vars;
4352         }
4353
4354         public function sourceStream(
4355                 $fp,
4356                 callable $lineCallback = null,
4357                 callable $resultCallback = null,
4358                 $fname = __METHOD__,
4359                 callable $inputCallback = null
4360         ) {
4361                 $delimiterReset = new ScopedCallback(
4362                         function ( $delimiter ) {
4363                                 $this->delimiter = $delimiter;
4364                         },
4365                         [ $this->delimiter ]
4366                 );
4367                 $cmd = '';
4368
4369                 while ( !feof( $fp ) ) {
4370                         if ( $lineCallback ) {
4371                                 call_user_func( $lineCallback );
4372                         }
4373
4374                         $line = trim( fgets( $fp ) );
4375
4376                         if ( $line == '' ) {
4377                                 continue;
4378                         }
4379
4380                         if ( $line[0] == '-' && $line[1] == '-' ) {
4381                                 continue;
4382                         }
4383
4384                         if ( $cmd != '' ) {
4385                                 $cmd .= ' ';
4386                         }
4387
4388                         $done = $this->streamStatementEnd( $cmd, $line );
4389
4390                         $cmd .= "$line\n";
4391
4392                         if ( $done || feof( $fp ) ) {
4393                                 $cmd = $this->replaceVars( $cmd );
4394
4395                                 if ( $inputCallback ) {
4396                                         $callbackResult = $inputCallback( $cmd );
4397
4398                                         if ( is_string( $callbackResult ) || !$callbackResult ) {
4399                                                 $cmd = $callbackResult;
4400                                         }
4401                                 }
4402
4403                                 if ( $cmd ) {
4404                                         $res = $this->query( $cmd, $fname );
4405
4406                                         if ( $resultCallback ) {
4407                                                 $resultCallback( $res, $this );
4408                                         }
4409
4410                                         if ( $res === false ) {
4411                                                 $err = $this->lastError();
4412
4413                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
4414                                         }
4415                                 }
4416                                 $cmd = '';
4417                         }
4418                 }
4419
4420                 ScopedCallback::consume( $delimiterReset );
4421                 return true;
4422         }
4423
4424         /**
4425          * Called by sourceStream() to check if we've reached a statement end
4426          *
4427          * @param string &$sql SQL assembled so far
4428          * @param string &$newLine New line about to be added to $sql
4429          * @return bool Whether $newLine contains end of the statement
4430          */
4431         public function streamStatementEnd( &$sql, &$newLine ) {
4432                 if ( $this->delimiter ) {
4433                         $prev = $newLine;
4434                         $newLine = preg_replace(
4435                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
4436                         if ( $newLine != $prev ) {
4437                                 return true;
4438                         }
4439                 }
4440
4441                 return false;
4442         }
4443
4444         /**
4445          * Database independent variable replacement. Replaces a set of variables
4446          * in an SQL statement with their contents as given by $this->getSchemaVars().
4447          *
4448          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
4449          *
4450          * - '{$var}' should be used for text and is passed through the database's
4451          *   addQuotes method.
4452          * - `{$var}` should be used for identifiers (e.g. table and database names).
4453          *   It is passed through the database's addIdentifierQuotes method which
4454          *   can be overridden if the database uses something other than backticks.
4455          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
4456          *   database's tableName method.
4457          * - / *i* / passes the name that follows through the database's indexName method.
4458          * - In all other cases, / *$var* / is left unencoded. Except for table options,
4459          *   its use should be avoided. In 1.24 and older, string encoding was applied.
4460          *
4461          * @param string $ins SQL statement to replace variables in
4462          * @return string The new SQL statement with variables replaced
4463          */
4464         protected function replaceVars( $ins ) {
4465                 $vars = $this->getSchemaVars();
4466                 return preg_replace_callback(
4467                         '!
4468                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
4469                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
4470                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
4471                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
4472                         !x',
4473                         function ( $m ) use ( $vars ) {
4474                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
4475                                 // check for both nonexistent keys *and* the empty string.
4476                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
4477                                         if ( $m[1] === 'i' ) {
4478                                                 return $this->indexName( $m[2] );
4479                                         } else {
4480                                                 return $this->tableName( $m[2] );
4481                                         }
4482                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
4483                                         return $this->addQuotes( $vars[$m[3]] );
4484                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
4485                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
4486                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
4487                                         return $vars[$m[5]];
4488                                 } else {
4489                                         return $m[0];
4490                                 }
4491                         },
4492                         $ins
4493                 );
4494         }
4495
4496         /**
4497          * Get schema variables. If none have been set via setSchemaVars(), then
4498          * use some defaults from the current object.
4499          *
4500          * @return array
4501          */
4502         protected function getSchemaVars() {
4503                 if ( $this->schemaVars ) {
4504                         return $this->schemaVars;
4505                 } else {
4506                         return $this->getDefaultSchemaVars();
4507                 }
4508         }
4509
4510         /**
4511          * Get schema variables to use if none have been set via setSchemaVars().
4512          *
4513          * Override this in derived classes to provide variables for tables.sql
4514          * and SQL patch files.
4515          *
4516          * @return array
4517          */
4518         protected function getDefaultSchemaVars() {
4519                 return [];
4520         }
4521
4522         public function lockIsFree( $lockName, $method ) {
4523                 // RDBMs methods for checking named locks may or may not count this thread itself.
4524                 // In MySQL, IS_FREE_LOCK() returns 0 if the thread already has the lock. This is
4525                 // the behavior choosen by the interface for this method.
4526                 return !isset( $this->namedLocksHeld[$lockName] );
4527         }
4528
4529         public function lock( $lockName, $method, $timeout = 5 ) {
4530                 $this->namedLocksHeld[$lockName] = 1;
4531
4532                 return true;
4533         }
4534
4535         public function unlock( $lockName, $method ) {
4536                 unset( $this->namedLocksHeld[$lockName] );
4537
4538                 return true;
4539         }
4540
4541         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
4542                 if ( $this->writesOrCallbacksPending() ) {
4543                         // This only flushes transactions to clear snapshots, not to write data
4544                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
4545                         throw new DBUnexpectedError(
4546                                 $this,
4547                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
4548                         );
4549                 }
4550
4551                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
4552                         return null;
4553                 }
4554
4555                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
4556                         if ( $this->trxLevel() ) {
4557                                 // There is a good chance an exception was thrown, causing any early return
4558                                 // from the caller. Let any error handler get a chance to issue rollback().
4559                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
4560                                 $this->onTransactionResolution(
4561                                         function () use ( $lockKey, $fname ) {
4562                                                 $this->unlock( $lockKey, $fname );
4563                                         },
4564                                         $fname
4565                                 );
4566                         } else {
4567                                 $this->unlock( $lockKey, $fname );
4568                         }
4569                 } );
4570
4571                 $this->commit( $fname, self::FLUSHING_INTERNAL );
4572
4573                 return $unlocker;
4574         }
4575
4576         public function namedLocksEnqueue() {
4577                 return false;
4578         }
4579
4580         public function tableLocksHaveTransactionScope() {
4581                 return true;
4582         }
4583
4584         final public function lockTables( array $read, array $write, $method ) {
4585                 if ( $this->writesOrCallbacksPending() ) {
4586                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
4587                 }
4588
4589                 if ( $this->tableLocksHaveTransactionScope() ) {
4590                         $this->startAtomic( $method );
4591                 }
4592
4593                 return $this->doLockTables( $read, $write, $method );
4594         }
4595
4596         /**
4597          * Helper function for lockTables() that handles the actual table locking
4598          *
4599          * @param array $read Array of tables to lock for read access
4600          * @param array $write Array of tables to lock for write access
4601          * @param string $method Name of caller
4602          * @return true
4603          */
4604         protected function doLockTables( array $read, array $write, $method ) {
4605                 return true;
4606         }
4607
4608         final public function unlockTables( $method ) {
4609                 if ( $this->tableLocksHaveTransactionScope() ) {
4610                         $this->endAtomic( $method );
4611
4612                         return true; // locks released on COMMIT/ROLLBACK
4613                 }
4614
4615                 return $this->doUnlockTables( $method );
4616         }
4617
4618         /**
4619          * Helper function for unlockTables() that handles the actual table unlocking
4620          *
4621          * @param string $method Name of caller
4622          * @return true
4623          */
4624         protected function doUnlockTables( $method ) {
4625                 return true;
4626         }
4627
4628         /**
4629          * Delete a table
4630          * @param string $tableName
4631          * @param string $fName
4632          * @return bool|ResultWrapper
4633          * @since 1.18
4634          */
4635         public function dropTable( $tableName, $fName = __METHOD__ ) {
4636                 if ( !$this->tableExists( $tableName, $fName ) ) {
4637                         return false;
4638                 }
4639                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
4640
4641                 return $this->query( $sql, $fName );
4642         }
4643
4644         public function getInfinity() {
4645                 return 'infinity';
4646         }
4647
4648         public function encodeExpiry( $expiry ) {
4649                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4650                         ? $this->getInfinity()
4651                         : $this->timestamp( $expiry );
4652         }
4653
4654         public function decodeExpiry( $expiry, $format = TS_MW ) {
4655                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
4656                         return 'infinity';
4657                 }
4658
4659                 return ConvertibleTimestamp::convert( $format, $expiry );
4660         }
4661
4662         public function setBigSelects( $value = true ) {
4663                 // no-op
4664         }
4665
4666         public function isReadOnly() {
4667                 return ( $this->getReadOnlyReason() !== false );
4668         }
4669
4670         /**
4671          * @return string|bool Reason this DB is read-only or false if it is not
4672          */
4673         protected function getReadOnlyReason() {
4674                 $reason = $this->getLBInfo( 'readOnlyReason' );
4675
4676                 return is_string( $reason ) ? $reason : false;
4677         }
4678
4679         public function setTableAliases( array $aliases ) {
4680                 $this->tableAliases = $aliases;
4681         }
4682
4683         public function setIndexAliases( array $aliases ) {
4684                 $this->indexAliases = $aliases;
4685         }
4686
4687         /**
4688          * Get the underlying binding connection handle
4689          *
4690          * Makes sure the connection resource is set (disconnects and ping() failure can unset it).
4691          * This catches broken callers than catch and ignore disconnection exceptions.
4692          * Unlike checking isOpen(), this is safe to call inside of open().
4693          *
4694          * @return mixed
4695          * @throws DBUnexpectedError
4696          * @since 1.26
4697          */
4698         protected function getBindingHandle() {
4699                 if ( !$this->conn ) {
4700                         throw new DBUnexpectedError(
4701                                 $this,
4702                                 'DB connection was already closed or the connection dropped.'
4703                         );
4704                 }
4705
4706                 return $this->conn;
4707         }
4708
4709         /**
4710          * @since 1.19
4711          * @return string
4712          */
4713         public function __toString() {
4714                 return (string)$this->conn;
4715         }
4716
4717         /**
4718          * Make sure that copies do not share the same client binding handle
4719          * @throws DBConnectionError
4720          */
4721         public function __clone() {
4722                 $this->connLogger->warning(
4723                         "Cloning " . static::class . " is not recommended; forking connection:\n" .
4724                         ( new RuntimeException() )->getTraceAsString()
4725                 );
4726
4727                 if ( $this->isOpen() ) {
4728                         // Open a new connection resource without messing with the old one
4729                         $this->opened = false;
4730                         $this->conn = false;
4731                         $this->trxEndCallbacks = []; // don't copy
4732                         $this->handleSessionLossPreconnect(); // no trx or locks anymore
4733                         $this->open(
4734                                 $this->server,
4735                                 $this->user,
4736                                 $this->password,
4737                                 $this->getDBname(),
4738                                 $this->dbSchema(),
4739                                 $this->tablePrefix()
4740                         );
4741                         $this->lastPing = microtime( true );
4742                 }
4743         }
4744
4745         /**
4746          * Called by serialize. Throw an exception when DB connection is serialized.
4747          * This causes problems on some database engines because the connection is
4748          * not restored on unserialize.
4749          */
4750         public function __sleep() {
4751                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
4752                         'the connection is not restored on wakeup.' );
4753         }
4754
4755         /**
4756          * Run a few simple sanity checks and close dangling connections
4757          */
4758         public function __destruct() {
4759                 if ( $this->trxLevel && $this->trxDoneWrites ) {
4760                         trigger_error( "Uncommitted DB writes (transaction from {$this->trxFname})." );
4761                 }
4762
4763                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
4764                 if ( $danglingWriters ) {
4765                         $fnames = implode( ', ', $danglingWriters );
4766                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
4767                 }
4768
4769                 if ( $this->conn ) {
4770                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
4771                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
4772                         Wikimedia\suppressWarnings();
4773                         $this->closeConnection();
4774                         Wikimedia\restoreWarnings();
4775                         $this->conn = false;
4776                         $this->opened = false;
4777                 }
4778         }
4779 }
4780
4781 /**
4782  * @deprecated since 1.28
4783  */
4784 class_alias( Database::class, 'DatabaseBase' );
4785
4786 /**
4787  * @deprecated since 1.29
4788  */
4789 class_alias( Database::class, 'Database' );