includes/libs/rdbms/database/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * This file deals with database interface functions
   6  * and query specifics/optimisations.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Database
  25  */
  26 namespace Wikimedia\Rdbms;
  27
  28 use Psr\Log\LoggerAwareInterface;
  29 use Psr\Log\LoggerInterface;
  30 use Psr\Log\NullLogger;
  31 use Wikimedia\ScopedCallback;
  32 use Wikimedia\Timestamp\ConvertibleTimestamp;
  33 use Wikimedia;
  34 use BagOStuff;
  35 use HashBagOStuff;
  36 use LogicException;
  37 use InvalidArgumentException;
  38 use UnexpectedValueException;
  39 use Exception;
  40 use RuntimeException;
  41
  42 /**
  43  * Relational database abstraction object
  44  *
  45  * @ingroup Database
  46  * @since 1.28
  47  */
  48 abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAwareInterface {
  49         /** Number of times to re-try an operation in case of deadlock */
  50         const DEADLOCK_TRIES = 4;
  51         /** Minimum time to wait before retry, in microseconds */
  52         const DEADLOCK_DELAY_MIN = 500000;
  53         /** Maximum time to wait before retry */
  54         const DEADLOCK_DELAY_MAX = 1500000;
  55
  56         /** How long before it is worth doing a dummy query to test the connection */
  57         const PING_TTL = 1.0;
  58         const PING_QUERY = 'SELECT 1 AS ping';
  59
  60         const TINY_WRITE_SEC = 0.010;
  61         const SLOW_WRITE_SEC = 0.500;
  62         const SMALL_WRITE_ROWS = 100;
  63
  64         /** @var string Whether lock granularity is on the level of the entire database */
  65         const ATTR_DB_LEVEL_LOCKING = 'db-level-locking';
  66
  67         /** @var int New Database instance will not be connected yet when returned */
  68         const NEW_UNCONNECTED = 0;
  69         /** @var int New Database instance will already be connected when returned */
  70         const NEW_CONNECTED = 1;
  71
  72         /** @var string SQL query */
  73         protected $lastQuery = '';
  74         /** @var float|bool UNIX timestamp of last write query */
  75         protected $lastWriteTime = false;
  76         /** @var string|bool */
  77         protected $phpError = false;
  78         /** @var string Server that this instance is currently connected to */
  79         protected $server;
  80         /** @var string User that this instance is currently connected under the name of */
  81         protected $user;
  82         /** @var string Password used to establish the current connection */
  83         protected $password;
  84         /** @var array[] Map of (table => (dbname, schema, prefix) map) */
  85         protected $tableAliases = [];
  86         /** @var string[] Map of (index alias => index) */
  87         protected $indexAliases = [];
  88         /** @var bool Whether this PHP instance is for a CLI script */
  89         protected $cliMode;
  90         /** @var string Agent name for query profiling */
  91         protected $agent;
  92         /** @var array Parameters used by initConnection() to establish a connection */
  93         protected $connectionParams = [];
  94         /** @var BagOStuff APC cache */
  95         protected $srvCache;
  96         /** @var LoggerInterface */
  97         protected $connLogger;
  98         /** @var LoggerInterface */
  99         protected $queryLogger;
 100         /** @var callable Error logging callback */
 101         protected $errorLogger;
 102         /** @var callable Deprecation logging callback */
 103         protected $deprecationLogger;
 104
 105         /** @var resource|null Database connection */
 106         protected $conn = null;
 107         /** @var bool */
 108         protected $opened = false;
 109
 110         /** @var array[] List of (callable, method name, atomic section id) */
 111         protected $trxIdleCallbacks = [];
 112         /** @var array[] List of (callable, method name, atomic section id) */
 113         protected $trxPreCommitCallbacks = [];
 114         /** @var array[] List of (callable, method name, atomic section id) */
 115         protected $trxEndCallbacks = [];
 116         /** @var callable[] Map of (name => callable) */
 117         protected $trxRecurringCallbacks = [];
 118         /** @var bool Whether to suppress triggering of transaction end callbacks */
 119         protected $trxEndCallbacksSuppressed = false;
 120
 121         /** @var int */
 122         protected $flags;
 123         /** @var array */
 124         protected $lbInfo = [];
 125         /** @var array|bool */
 126         protected $schemaVars = false;
 127         /** @var array */
 128         protected $sessionVars = [];
 129         /** @var array|null */
 130         protected $preparedArgs;
 131         /** @var string|bool|null Stashed value of html_errors INI setting */
 132         protected $htmlErrors;
 133         /** @var string */
 134         protected $delimiter = ';';
 135         /** @var DatabaseDomain */
 136         protected $currentDomain;
 137         /** @var integer|null Rows affected by the last query to query() or its CRUD wrappers */
 138         protected $affectedRowCount;
 139
 140         /**
 141          * @var int Transaction status
 142          */
 143         protected $trxStatus = self::STATUS_TRX_NONE;
 144         /**
 145          * @var Exception|null The last error that caused the status to become STATUS_TRX_ERROR
 146          */
 147         protected $trxStatusCause;
 148         /**
 149          * @var array|null If wasKnownStatementRollbackError() prevented trxStatus from being set,
 150          *  the relevant details are stored here.
 151          */
 152         protected $trxStatusIgnoredCause;
 153         /**
 154          * Either 1 if a transaction is active or 0 otherwise.
 155          * The other Trx fields may not be meaningfull if this is 0.
 156          *
 157          * @var int
 158          */
 159         protected $trxLevel = 0;
 160         /**
 161          * Either a short hexidecimal string if a transaction is active or ""
 162          *
 163          * @var string
 164          * @see Database::trxLevel
 165          */
 166         protected $trxShortId = '';
 167         /**
 168          * The UNIX time that the transaction started. Callers can assume that if
 169          * snapshot isolation is used, then the data is *at least* up to date to that
 170          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 171          *
 172          * @var float|null
 173          * @see Database::trxLevel
 174          */
 175         private $trxTimestamp = null;
 176         /** @var float Lag estimate at the time of BEGIN */
 177         private $trxReplicaLag = null;
 178         /**
 179          * Remembers the function name given for starting the most recent transaction via begin().
 180          * Used to provide additional context for error reporting.
 181          *
 182          * @var string
 183          * @see Database::trxLevel
 184          */
 185         private $trxFname = null;
 186         /**
 187          * Record if possible write queries were done in the last transaction started
 188          *
 189          * @var bool
 190          * @see Database::trxLevel
 191          */
 192         private $trxDoneWrites = false;
 193         /**
 194          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 195          *
 196          * @var bool
 197          * @see Database::trxLevel
 198          */
 199         private $trxAutomatic = false;
 200         /**
 201          * Counter for atomic savepoint identifiers. Reset when a new transaction begins.
 202          *
 203          * @var int
 204          */
 205         private $trxAtomicCounter = 0;
 206         /**
 207          * Array of levels of atomicity within transactions
 208          *
 209          * @var array List of (name, unique ID, savepoint ID)
 210          */
 211         private $trxAtomicLevels = [];
 212         /**
 213          * Record if the current transaction was started implicitly by Database::startAtomic
 214          *
 215          * @var bool
 216          */
 217         private $trxAutomaticAtomic = false;
 218         /**
 219          * Track the write query callers of the current transaction
 220          *
 221          * @var string[]
 222          */
 223         private $trxWriteCallers = [];
 224         /**
 225          * @var float Seconds spent in write queries for the current transaction
 226          */
 227         private $trxWriteDuration = 0.0;
 228         /**
 229          * @var int Number of write queries for the current transaction
 230          */
 231         private $trxWriteQueryCount = 0;
 232         /**
 233          * @var int Number of rows affected by write queries for the current transaction
 234          */
 235         private $trxWriteAffectedRows = 0;
 236         /**
 237          * @var float Like trxWriteQueryCount but excludes lock-bound, easy to replicate, queries
 238          */
 239         private $trxWriteAdjDuration = 0.0;
 240         /**
 241          * @var int Number of write queries counted in trxWriteAdjDuration
 242          */
 243         private $trxWriteAdjQueryCount = 0;
 244         /**
 245          * @var float RTT time estimate
 246          */
 247         private $rttEstimate = 0.0;
 248
 249         /** @var array Map of (name => 1) for locks obtained via lock() */
 250         private $namedLocksHeld = [];
 251         /** @var array Map of (table name => 1) for TEMPORARY tables */
 252         protected $sessionTempTables = [];
 253
 254         /** @var IDatabase|null Lazy handle to the master DB this server replicates from */
 255         private $lazyMasterHandle;
 256
 257         /** @var float UNIX timestamp */
 258         protected $lastPing = 0.0;
 259
 260         /** @var int[] Prior flags member variable values */
 261         private $priorFlags = [];
 262
 263         /** @var mixed Class name or object With profileIn/profileOut methods */
 264         protected $profiler;
 265         /** @var TransactionProfiler */
 266         protected $trxProfiler;
 267
 268         /** @var int */
 269         protected $nonNativeInsertSelectBatchSize = 10000;
 270
 271         /** @var string Idiom used when a cancelable atomic section started the transaction */
 272         private static $NOT_APPLICABLE = 'n/a';
 273         /** @var string Prefix to the atomic section counter used to make savepoint IDs */
 274         private static $SAVEPOINT_PREFIX = 'wikimedia_rdbms_atomic';
 275
 276         /** @var int Transaction is in a error state requiring a full or savepoint rollback */
 277         const STATUS_TRX_ERROR = 1;
 278         /** @var int Transaction is active and in a normal state */
 279         const STATUS_TRX_OK = 2;
 280         /** @var int No transaction is active */
 281         const STATUS_TRX_NONE = 3;
 282
 283         /**
 284          * @note exceptions for missing libraries/drivers should be thrown in initConnection()
 285          * @param array $params Parameters passed from Database::factory()
 286          */
 287         protected function __construct( array $params ) {
 288                 foreach ( [ 'host', 'user', 'password', 'dbname', 'schema', 'tablePrefix' ] as $name ) {
 289                         $this->connectionParams[$name] = $params[$name];
 290                 }
 291
 292                 $this->cliMode = $params['cliMode'];
 293                 // Agent name is added to SQL queries in a comment, so make sure it can't break out
 294                 $this->agent = str_replace( '/', '-', $params['agent'] );
 295
 296                 $this->flags = $params['flags'];
 297                 if ( $this->flags & self::DBO_DEFAULT ) {
 298                         if ( $this->cliMode ) {
 299                                 $this->flags &= ~self::DBO_TRX;
 300                         } else {
 301                                 $this->flags |= self::DBO_TRX;
 302                         }
 303                 }
 304                 // Disregard deprecated DBO_IGNORE flag (T189999)
 305                 $this->flags &= ~self::DBO_IGNORE;
 306
 307                 $this->sessionVars = $params['variables'];
 308
 309                 $this->srvCache = $params['srvCache'] ?? new HashBagOStuff();
 310
 311                 $this->profiler = $params['profiler'];
 312                 $this->trxProfiler = $params['trxProfiler'];
 313                 $this->connLogger = $params['connLogger'];
 314                 $this->queryLogger = $params['queryLogger'];
 315                 $this->errorLogger = $params['errorLogger'];
 316                 $this->deprecationLogger = $params['deprecationLogger'];
 317
 318                 if ( isset( $params['nonNativeInsertSelectBatchSize'] ) ) {
 319                         $this->nonNativeInsertSelectBatchSize = $params['nonNativeInsertSelectBatchSize'];
 320                 }
 321
 322                 // Set initial dummy domain until open() sets the final DB/prefix
 323                 $this->currentDomain = new DatabaseDomain(
 324                         $params['dbname'] != '' ? $params['dbname'] : null,
 325                         $params['schema'] != '' ? $params['schema'] : null,
 326                         $params['tablePrefix']
 327                 );
 328         }
 329
 330         /**
 331          * Initialize the connection to the database over the wire (or to local files)
 332          *
 333          * @throws LogicException
 334          * @throws InvalidArgumentException
 335          * @throws DBConnectionError
 336          * @since 1.31
 337          */
 338         final public function initConnection() {
 339                 if ( $this->isOpen() ) {
 340                         throw new LogicException( __METHOD__ . ': already connected.' );
 341                 }
 342                 // Establish the connection
 343                 $this->doInitConnection();
 344         }
 345
 346         /**
 347          * Actually connect to the database over the wire (or to local files)
 348          *
 349          * @throws InvalidArgumentException
 350          * @throws DBConnectionError
 351          * @since 1.31
 352          */
 353         protected function doInitConnection() {
 354                 if ( strlen( $this->connectionParams['user'] ) ) {
 355                         $this->open(
 356                                 $this->connectionParams['host'],
 357                                 $this->connectionParams['user'],
 358                                 $this->connectionParams['password'],
 359                                 $this->connectionParams['dbname'],
 360                                 $this->connectionParams['schema'],
 361                                 $this->connectionParams['tablePrefix']
 362                         );
 363                 } else {
 364                         throw new InvalidArgumentException( "No database user provided." );
 365                 }
 366         }
 367
 368         /**
 369          * Open a new connection to the database (closing any existing one)
 370          *
 371          * @param string $server Database server host
 372          * @param string $user Database user name
 373          * @param string $password Database user password
 374          * @param string $dbName Database name
 375          * @param string|null $schema Database schema name
 376          * @param string $tablePrefix Table prefix
 377          * @return bool
 378          * @throws DBConnectionError
 379          */
 380         abstract protected function open( $server, $user, $password, $dbName, $schema, $tablePrefix );
 381
 382         /**
 383          * Construct a Database subclass instance given a database type and parameters
 384          *
 385          * This also connects to the database immediately upon object construction
 386          *
 387          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 388          * @param array $p Parameter map with keys:
 389          *   - host : The hostname of the DB server
 390          *   - user : The name of the database user the client operates under
 391          *   - password : The password for the database user
 392          *   - dbname : The name of the database to use where queries do not specify one.
 393          *      The database must exist or an error might be thrown. Setting this to the empty string
 394          *      will avoid any such errors and make the handle have no implicit database scope. This is
 395          *      useful for queries like SHOW STATUS, CREATE DATABASE, or DROP DATABASE. Note that a
 396          *      "database" in Postgres is rougly equivalent to an entire MySQL server. This the domain
 397          *      in which user names and such are defined, e.g. users are database-specific in Postgres.
 398          *   - schema : The database schema to use (if supported). A "schema" in Postgres is roughly
 399          *      equivalent to a "database" in MySQL. Note that MySQL and SQLite do not use schemas.
 400          *   - tablePrefix : Optional table prefix that is implicitly added on to all table names
 401          *      recognized in queries. This can be used in place of schemas for handle site farms.
 402          *   - flags : Optional bitfield of DBO_* constants that define connection, protocol,
 403          *      buffering, and transaction behavior. It is STRONGLY adviced to leave the DBO_DEFAULT
 404          *      flag in place UNLESS this this database simply acts as a key/value store.
 405          *   - driver: Optional name of a specific DB client driver. For MySQL, there is only the
 406          *      'mysqli' driver; the old one 'mysql' has been removed.
 407          *   - variables: Optional map of session variables to set after connecting. This can be
 408          *      used to adjust lock timeouts or encoding modes and the like.
 409          *   - connLogger: Optional PSR-3 logger interface instance.
 410          *   - queryLogger: Optional PSR-3 logger interface instance.
 411          *   - profiler: Optional class name or object with profileIn()/profileOut() methods.
 412          *      These will be called in query(), using a simplified version of the SQL that also
 413          *      includes the agent as a SQL comment.
 414          *   - trxProfiler: Optional TransactionProfiler instance.
 415          *   - errorLogger: Optional callback that takes an Exception and logs it.
 416          *   - deprecationLogger: Optional callback that takes a string and logs it.
 417          *   - cliMode: Whether to consider the execution context that of a CLI script.
 418          *   - agent: Optional name used to identify the end-user in query profiling/logging.
 419          *   - srvCache: Optional BagOStuff instance to an APC-style cache.
 420          *   - nonNativeInsertSelectBatchSize: Optional batch size for non-native INSERT SELECT emulation.
 421          * @param int $connect One of the class constants (NEW_CONNECTED, NEW_UNCONNECTED) [optional]
 422          * @return Database|null If the database driver or extension cannot be found
 423          * @throws InvalidArgumentException If the database driver or extension cannot be found
 424          * @since 1.18
 425          */
 426         final public static function factory( $dbType, $p = [], $connect = self::NEW_CONNECTED ) {
 427                 $class = self::getClass( $dbType, $p['driver'] ?? null );
 428
 429                 if ( class_exists( $class ) && is_subclass_of( $class, IDatabase::class ) ) {
 430                         // Resolve some defaults for b/c
 431                         $p['host'] = $p['host'] ?? false;
 432                         $p['user'] = $p['user'] ?? false;
 433                         $p['password'] = $p['password'] ?? false;
 434                         $p['dbname'] = $p['dbname'] ?? false;
 435                         $p['flags'] = $p['flags'] ?? 0;
 436                         $p['variables'] = $p['variables'] ?? [];
 437                         $p['tablePrefix'] = $p['tablePrefix'] ?? '';
 438                         $p['schema'] = $p['schema'] ?? null;
 439                         $p['cliMode'] = $p['cliMode'] ?? ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 440                         $p['agent'] = $p['agent'] ?? '';
 441                         if ( !isset( $p['connLogger'] ) ) {
 442                                 $p['connLogger'] = new NullLogger();
 443                         }
 444                         if ( !isset( $p['queryLogger'] ) ) {
 445                                 $p['queryLogger'] = new NullLogger();
 446                         }
 447                         $p['profiler'] = $p['profiler'] ?? null;
 448                         if ( !isset( $p['trxProfiler'] ) ) {
 449                                 $p['trxProfiler'] = new TransactionProfiler();
 450                         }
 451                         if ( !isset( $p['errorLogger'] ) ) {
 452                                 $p['errorLogger'] = function ( Exception $e ) {
 453                                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 454                                 };
 455                         }
 456                         if ( !isset( $p['deprecationLogger'] ) ) {
 457                                 $p['deprecationLogger'] = function ( $msg ) {
 458                                         trigger_error( $msg, E_USER_DEPRECATED );
 459                                 };
 460                         }
 461
 462                         /** @var Database $conn */
 463                         $conn = new $class( $p );
 464                         if ( $connect == self::NEW_CONNECTED ) {
 465                                 $conn->initConnection();
 466                         }
 467                 } else {
 468                         $conn = null;
 469                 }
 470
 471                 return $conn;
 472         }
 473
 474         /**
 475          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 476          * @param string|null $driver Optional name of a specific DB client driver
 477          * @return array Map of (Database::ATTRIBUTE_* constant => value) for all such constants
 478          * @throws InvalidArgumentException
 479          * @since 1.31
 480          */
 481         final public static function attributesFromType( $dbType, $driver = null ) {
 482                 static $defaults = [ self::ATTR_DB_LEVEL_LOCKING => false ];
 483
 484                 $class = self::getClass( $dbType, $driver );
 485
 486                 return call_user_func( [ $class, 'getAttributes' ] ) + $defaults;
 487         }
 488
 489         /**
 490          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 491          * @param string|null $driver Optional name of a specific DB client driver
 492          * @return string Database subclass name to use
 493          * @throws InvalidArgumentException
 494          */
 495         private static function getClass( $dbType, $driver = null ) {
 496                 // For database types with built-in support, the below maps type to IDatabase
 497                 // implementations. For types with multipe driver implementations (PHP extensions),
 498                 // an array can be used, keyed by extension name. In case of an array, the
 499                 // optional 'driver' parameter can be used to force a specific driver. Otherwise,
 500                 // we auto-detect the first available driver. For types without built-in support,
 501                 // an class named "Database<Type>" us used, eg. DatabaseFoo for type 'foo'.
 502                 static $builtinTypes = [
 503                         'mssql' => DatabaseMssql::class,
 504                         'mysql' => [ 'mysqli' => DatabaseMysqli::class ],
 505                         'sqlite' => DatabaseSqlite::class,
 506                         'postgres' => DatabasePostgres::class,
 507                 ];
 508
 509                 $dbType = strtolower( $dbType );
 510                 $class = false;
 511
 512                 if ( isset( $builtinTypes[$dbType] ) ) {
 513                         $possibleDrivers = $builtinTypes[$dbType];
 514                         if ( is_string( $possibleDrivers ) ) {
 515                                 $class = $possibleDrivers;
 516                         } else {
 517                                 if ( (string)$driver !== '' ) {
 518                                         if ( !isset( $possibleDrivers[$driver] ) ) {
 519                                                 throw new InvalidArgumentException( __METHOD__ .
 520                                                         " type '$dbType' does not support driver '{$driver}'" );
 521                                         } else {
 522                                                 $class = $possibleDrivers[$driver];
 523                                         }
 524                                 } else {
 525                                         foreach ( $possibleDrivers as $posDriver => $possibleClass ) {
 526                                                 if ( extension_loaded( $posDriver ) ) {
 527                                                         $class = $possibleClass;
 528                                                         break;
 529                                                 }
 530                                         }
 531                                 }
 532                         }
 533                 } else {
 534                         $class = 'Database' . ucfirst( $dbType );
 535                 }
 536
 537                 if ( $class === false ) {
 538                         throw new InvalidArgumentException( __METHOD__ .
 539                                 " no viable database extension found for type '$dbType'" );
 540                 }
 541
 542                 return $class;
 543         }
 544
 545         /**
 546          * @return array Map of (Database::ATTRIBUTE_* constant => value
 547          * @since 1.31
 548          */
 549         protected static function getAttributes() {
 550                 return [];
 551         }
 552
 553         /**
 554          * Set the PSR-3 logger interface to use for query logging. (The logger
 555          * interfaces for connection logging and error logging can be set with the
 556          * constructor.)
 557          *
 558          * @param LoggerInterface $logger
 559          */
 560         public function setLogger( LoggerInterface $logger ) {
 561                 $this->queryLogger = $logger;
 562         }
 563
 564         public function getServerInfo() {
 565                 return $this->getServerVersion();
 566         }
 567
 568         public function bufferResults( $buffer = null ) {
 569                 $res = !$this->getFlag( self::DBO_NOBUFFER );
 570                 if ( $buffer !== null ) {
 571                         $buffer
 572                                 ? $this->clearFlag( self::DBO_NOBUFFER )
 573                                 : $this->setFlag( self::DBO_NOBUFFER );
 574                 }
 575
 576                 return $res;
 577         }
 578
 579         public function trxLevel() {
 580                 return $this->trxLevel;
 581         }
 582
 583         public function trxTimestamp() {
 584                 return $this->trxLevel ? $this->trxTimestamp : null;
 585         }
 586
 587         /**
 588          * @return int One of the STATUS_TRX_* class constants
 589          * @since 1.31
 590          */
 591         public function trxStatus() {
 592                 return $this->trxStatus;
 593         }
 594
 595         public function tablePrefix( $prefix = null ) {
 596                 $old = $this->currentDomain->getTablePrefix();
 597                 if ( $prefix !== null ) {
 598                         $this->currentDomain = new DatabaseDomain(
 599                                 $this->currentDomain->getDatabase(),
 600                                 $this->currentDomain->getSchema(),
 601                                 $prefix
 602                         );
 603                 }
 604
 605                 return $old;
 606         }
 607
 608         public function dbSchema( $schema = null ) {
 609                 $old = $this->currentDomain->getSchema();
 610                 if ( $schema !== null ) {
 611                         $this->currentDomain = new DatabaseDomain(
 612                                 $this->currentDomain->getDatabase(),
 613                                 // DatabaseDomain uses null for unspecified schemas
 614                                 strlen( $schema ) ? $schema : null,
 615                                 $this->currentDomain->getTablePrefix()
 616                         );
 617                 }
 618
 619                 return (string)$old;
 620         }
 621
 622         /**
 623          * @return string Schema to use to qualify relations in queries
 624          */
 625         protected function relationSchemaQualifier() {
 626                 return $this->dbSchema();
 627         }
 628
 629         public function getLBInfo( $name = null ) {
 630                 if ( is_null( $name ) ) {
 631                         return $this->lbInfo;
 632                 } else {
 633                         if ( array_key_exists( $name, $this->lbInfo ) ) {
 634                                 return $this->lbInfo[$name];
 635                         } else {
 636                                 return null;
 637                         }
 638                 }
 639         }
 640
 641         public function setLBInfo( $name, $value = null ) {
 642                 if ( is_null( $value ) ) {
 643                         $this->lbInfo = $name;
 644                 } else {
 645                         $this->lbInfo[$name] = $value;
 646                 }
 647         }
 648
 649         public function setLazyMasterHandle( IDatabase $conn ) {
 650                 $this->lazyMasterHandle = $conn;
 651         }
 652
 653         /**
 654          * @return IDatabase|null
 655          * @see setLazyMasterHandle()
 656          * @since 1.27
 657          */
 658         protected function getLazyMasterHandle() {
 659                 return $this->lazyMasterHandle;
 660         }
 661
 662         public function implicitGroupby() {
 663                 return true;
 664         }
 665
 666         public function implicitOrderby() {
 667                 return true;
 668         }
 669
 670         public function lastQuery() {
 671                 return $this->lastQuery;
 672         }
 673
 674         public function doneWrites() {
 675                 return (bool)$this->lastWriteTime;
 676         }
 677
 678         public function lastDoneWrites() {
 679                 return $this->lastWriteTime ?: false;
 680         }
 681
 682         public function writesPending() {
 683                 return $this->trxLevel && $this->trxDoneWrites;
 684         }
 685
 686         public function writesOrCallbacksPending() {
 687                 return $this->trxLevel && (
 688                         $this->trxDoneWrites ||
 689                         $this->trxIdleCallbacks ||
 690                         $this->trxPreCommitCallbacks ||
 691                         $this->trxEndCallbacks
 692                 );
 693         }
 694
 695         public function preCommitCallbacksPending() {
 696                 return $this->trxLevel && $this->trxPreCommitCallbacks;
 697         }
 698
 699         /**
 700          * @return string|null
 701          */
 702         final protected function getTransactionRoundId() {
 703                 // If transaction round participation is enabled, see if one is active
 704                 if ( $this->getFlag( self::DBO_TRX ) ) {
 705                         $id = $this->getLBInfo( 'trxRoundId' );
 706
 707                         return is_string( $id ) ? $id : null;
 708                 }
 709
 710                 return null;
 711         }
 712
 713         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 714                 if ( !$this->trxLevel ) {
 715                         return false;
 716                 } elseif ( !$this->trxDoneWrites ) {
 717                         return 0.0;
 718                 }
 719
 720                 switch ( $type ) {
 721                         case self::ESTIMATE_DB_APPLY:
 722                                 return $this->pingAndCalculateLastTrxApplyTime();
 723                         default: // everything
 724                                 return $this->trxWriteDuration;
 725                 }
 726         }
 727
 728         /**
 729          * @return float Time to apply writes to replicas based on trxWrite* fields
 730          */
 731         private function pingAndCalculateLastTrxApplyTime() {
 732                 $this->ping( $rtt );
 733
 734                 $rttAdjTotal = $this->trxWriteAdjQueryCount * $rtt;
 735                 $applyTime = max( $this->trxWriteAdjDuration - $rttAdjTotal, 0 );
 736                 // For omitted queries, make them count as something at least
 737                 $omitted = $this->trxWriteQueryCount - $this->trxWriteAdjQueryCount;
 738                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 739
 740                 return $applyTime;
 741         }
 742
 743         public function pendingWriteCallers() {
 744                 return $this->trxLevel ? $this->trxWriteCallers : [];
 745         }
 746
 747         public function pendingWriteRowsAffected() {
 748                 return $this->trxWriteAffectedRows;
 749         }
 750
 751         /**
 752          * List the methods that have write queries or callbacks for the current transaction
 753          *
 754          * This method should not be used outside of Database/LoadBalancer
 755          *
 756          * @return string[]
 757          * @since 1.32
 758          */
 759         public function pendingWriteAndCallbackCallers() {
 760                 $fnames = $this->pendingWriteCallers();
 761                 foreach ( [
 762                         $this->trxIdleCallbacks,
 763                         $this->trxPreCommitCallbacks,
 764                         $this->trxEndCallbacks
 765                 ] as $callbacks ) {
 766                         foreach ( $callbacks as $callback ) {
 767                                 $fnames[] = $callback[1];
 768                         }
 769                 }
 770
 771                 return $fnames;
 772         }
 773
 774         /**
 775          * @return string
 776          */
 777         private function flatAtomicSectionList() {
 778                 return array_reduce( $this->trxAtomicLevels, function ( $accum, $v ) {
 779                         return $accum === null ? $v[0] : "$accum, " . $v[0];
 780                 } );
 781         }
 782
 783         public function isOpen() {
 784                 return $this->opened;
 785         }
 786
 787         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 788                 if ( ( $flag & self::DBO_IGNORE ) ) {
 789                         throw new UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 790                 }
 791
 792                 if ( $remember === self::REMEMBER_PRIOR ) {
 793                         array_push( $this->priorFlags, $this->flags );
 794                 }
 795                 $this->flags |= $flag;
 796         }
 797
 798         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 799                 if ( ( $flag & self::DBO_IGNORE ) ) {
 800                         throw new UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 801                 }
 802
 803                 if ( $remember === self::REMEMBER_PRIOR ) {
 804                         array_push( $this->priorFlags, $this->flags );
 805                 }
 806                 $this->flags &= ~$flag;
 807         }
 808
 809         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 810                 if ( !$this->priorFlags ) {
 811                         return;
 812                 }
 813
 814                 if ( $state === self::RESTORE_INITIAL ) {
 815                         $this->flags = reset( $this->priorFlags );
 816                         $this->priorFlags = [];
 817                 } else {
 818                         $this->flags = array_pop( $this->priorFlags );
 819                 }
 820         }
 821
 822         public function getFlag( $flag ) {
 823                 return (bool)( $this->flags & $flag );
 824         }
 825
 826         /**
 827          * @param string $name Class field name
 828          * @return mixed
 829          * @deprecated Since 1.28
 830          */
 831         public function getProperty( $name ) {
 832                 return $this->$name;
 833         }
 834
 835         public function getDomainID() {
 836                 return $this->currentDomain->getId();
 837         }
 838
 839         final public function getWikiID() {
 840                 return $this->getDomainID();
 841         }
 842
 843         /**
 844          * Get information about an index into an object
 845          * @param string $table Table name
 846          * @param string $index Index name
 847          * @param string $fname Calling function name
 848          * @return mixed Database-specific index description class or false if the index does not exist
 849          */
 850         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 851
 852         /**
 853          * Wrapper for addslashes()
 854          *
 855          * @param string $s String to be slashed.
 856          * @return string Slashed string.
 857          */
 858         abstract function strencode( $s );
 859
 860         /**
 861          * Set a custom error handler for logging errors during database connection
 862          */
 863         protected function installErrorHandler() {
 864                 $this->phpError = false;
 865                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 866                 set_error_handler( [ $this, 'connectionErrorLogger' ] );
 867         }
 868
 869         /**
 870          * Restore the previous error handler and return the last PHP error for this DB
 871          *
 872          * @return bool|string
 873          */
 874         protected function restoreErrorHandler() {
 875                 restore_error_handler();
 876                 if ( $this->htmlErrors !== false ) {
 877                         ini_set( 'html_errors', $this->htmlErrors );
 878                 }
 879
 880                 return $this->getLastPHPError();
 881         }
 882
 883         /**
 884          * @return string|bool Last PHP error for this DB (typically connection errors)
 885          */
 886         protected function getLastPHPError() {
 887                 if ( $this->phpError ) {
 888                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->phpError );
 889                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 890
 891                         return $error;
 892                 }
 893
 894                 return false;
 895         }
 896
 897         /**
 898          * Error handler for logging errors during database connection
 899          * This method should not be used outside of Database classes
 900          *
 901          * @param int $errno
 902          * @param string $errstr
 903          */
 904         public function connectionErrorLogger( $errno, $errstr ) {
 905                 $this->phpError = $errstr;
 906         }
 907
 908         /**
 909          * Create a log context to pass to PSR-3 logger functions.
 910          *
 911          * @param array $extras Additional data to add to context
 912          * @return array
 913          */
 914         protected function getLogContext( array $extras = [] ) {
 915                 return array_merge(
 916                         [
 917                                 'db_server' => $this->server,
 918                                 'db_name' => $this->getDBname(),
 919                                 'db_user' => $this->user,
 920                         ],
 921                         $extras
 922                 );
 923         }
 924
 925         final public function close() {
 926                 $exception = null; // error to throw after disconnecting
 927
 928                 if ( $this->conn ) {
 929                         // Roll back any dangling transaction first
 930                         if ( $this->trxLevel ) {
 931                                 if ( $this->trxAtomicLevels ) {
 932                                         // Cannot let incomplete atomic sections be committed
 933                                         $levels = $this->flatAtomicSectionList();
 934                                         $exception = new DBUnexpectedError(
 935                                                 $this,
 936                                                 __METHOD__ . ": atomic sections $levels are still open."
 937                                         );
 938                                 } elseif ( $this->trxAutomatic ) {
 939                                         // Only the connection manager can commit non-empty DBO_TRX transactions
 940                                         // (empty ones we can silently roll back)
 941                                         if ( $this->writesOrCallbacksPending() ) {
 942                                                 $exception = new DBUnexpectedError(
 943                                                         $this,
 944                                                         __METHOD__ .
 945                                                         ": mass commit/rollback of peer transaction required (DBO_TRX set)."
 946                                                 );
 947                                         }
 948                                 } else {
 949                                         // Manual transactions should have been committed or rolled
 950                                         // back, even if empty.
 951                                         $exception = new DBUnexpectedError(
 952                                                 $this,
 953                                                 __METHOD__ . ": transaction is still open (from {$this->trxFname})."
 954                                         );
 955                                 }
 956
 957                                 if ( $this->trxEndCallbacksSuppressed ) {
 958                                         $exception = $exception ?: new DBUnexpectedError(
 959                                                 $this,
 960                                                 __METHOD__ . ': callbacks are suppressed; cannot properly commit.'
 961                                         );
 962                                 }
 963
 964                                 // Rollback the changes and run any callbacks as needed
 965                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
 966                         }
 967
 968                         // Close the actual connection in the binding handle
 969                         $closed = $this->closeConnection();
 970                         $this->conn = false;
 971                 } else {
 972                         $closed = true; // already closed; nothing to do
 973                 }
 974
 975                 $this->opened = false;
 976
 977                 // Throw any unexpected errors after having disconnected
 978                 if ( $exception instanceof Exception ) {
 979                         throw $exception;
 980                 }
 981
 982                 // Sanity check that no callbacks are dangling
 983                 $fnames = $this->pendingWriteAndCallbackCallers();
 984                 if ( $fnames ) {
 985                         throw new RuntimeException(
 986                                 "Transaction callbacks are still pending:\n" . implode( ', ', $fnames )
 987                         );
 988                 }
 989
 990                 return $closed;
 991         }
 992
 993         /**
 994          * Make sure isOpen() returns true as a sanity check
 995          *
 996          * @throws DBUnexpectedError
 997          */
 998         protected function assertOpen() {
 999                 if ( !$this->isOpen() ) {
1000                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
1001                 }
1002         }
1003
1004         /**
1005          * Closes underlying database connection
1006          * @since 1.20
1007          * @return bool Whether connection was closed successfully
1008          */
1009         abstract protected function closeConnection();
1010
1011         /**
1012          * @deprecated since 1.32
1013          * @param string $error Fallback message, if none is given by DB
1014          * @throws DBConnectionError
1015          */
1016         public function reportConnectionError( $error = 'Unknown error' ) {
1017                 call_user_func( $this->deprecationLogger, 'Use of ' . __METHOD__ . ' is deprecated.' );
1018                 throw new DBConnectionError( $this, $this->lastError() ?: $error );
1019         }
1020
1021         /**
1022          * Run a query and return a DBMS-dependent wrapper or boolean
1023          *
1024          * For SELECT queries, this returns either:
1025          *   - a) A driver-specific value/resource, only on success. This can be iterated
1026          *        over by calling fetchObject()/fetchRow() until there are no more rows.
1027          *        Alternatively, the result can be passed to resultObject() to obtain a
1028          *        ResultWrapper instance which can then be iterated over via "foreach".
1029          *   - b) False, on any query failure
1030          *
1031          * For non-SELECT queries, this returns either:
1032          *   - a) A driver-specific value/resource, only on success
1033          *   - b) True, only on success (e.g. no meaningful result other than "OK")
1034          *   - c) False, on any query failure
1035          *
1036          * @param string $sql SQL query
1037          * @return mixed|bool An object, resource, or true on success; false on failure
1038          */
1039         abstract protected function doQuery( $sql );
1040
1041         /**
1042          * Determine whether a query writes to the DB. When in doubt, this returns true.
1043          *
1044          * Main use cases:
1045          *
1046          * - Subsequent web requests should not need to wait for replication from
1047          *   the master position seen by this web request, unless this request made
1048          *   changes to the master. This is handled by ChronologyProtector by checking
1049          *   doneWrites() at the end of the request. doneWrites() returns true if any
1050          *   query set lastWriteTime; which query() does based on isWriteQuery().
1051          *
1052          * - Reject write queries to replica DBs, in query().
1053          *
1054          * @param string $sql
1055          * @return bool
1056          */
1057         protected function isWriteQuery( $sql ) {
1058                 // BEGIN and COMMIT queries are considered read queries here.
1059                 // Database backends and drivers (MySQL, MariaDB, php-mysqli) generally
1060                 // treat these as write queries, in that their results have "affected rows"
1061                 // as meta data as from writes, instead of "num rows" as from reads.
1062                 // But, we treat them as read queries because when reading data (from
1063                 // either replica or master) we use transactions to enable repeatable-read
1064                 // snapshots, which ensures we get consistent results from the same snapshot
1065                 // for all queries within a request. Use cases:
1066                 // - Treating these as writes would trigger ChronologyProtector (see method doc).
1067                 // - We use this method to reject writes to replicas, but we need to allow
1068                 //   use of transactions on replicas for read snapshots. This fine given
1069                 //   that transactions by themselves don't make changes, only actual writes
1070                 //   within the transaction matter, which we still detect.
1071                 return !preg_match(
1072                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SAVEPOINT|RELEASE|SET|SHOW|EXPLAIN|\(SELECT)\b/i',
1073                         $sql
1074                 );
1075         }
1076
1077         /**
1078          * @param string $sql
1079          * @return string|null
1080          */
1081         protected function getQueryVerb( $sql ) {
1082                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
1083         }
1084
1085         /**
1086          * Determine whether a SQL statement is sensitive to isolation level.
1087          *
1088          * A SQL statement is considered transactable if its result could vary
1089          * depending on the transaction isolation level. Operational commands
1090          * such as 'SET' and 'SHOW' are not considered to be transactable.
1091          *
1092          * Main purpose: Used by query() to decide whether to begin a transaction
1093          * before the current query (in DBO_TRX mode, on by default).
1094          *
1095          * @param string $sql
1096          * @return bool
1097          */
1098         protected function isTransactableQuery( $sql ) {
1099                 return !in_array(
1100                         $this->getQueryVerb( $sql ),
1101                         [ 'BEGIN', 'ROLLBACK', 'COMMIT', 'SET', 'SHOW', 'CREATE', 'ALTER' ],
1102                         true
1103                 );
1104         }
1105
1106         /**
1107          * @param string $sql A SQL query
1108          * @return bool Whether $sql is SQL for TEMPORARY table operation
1109          */
1110         protected function registerTempTableOperation( $sql ) {
1111                 if ( preg_match(
1112                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1113                         $sql,
1114                         $matches
1115                 ) ) {
1116                         $this->sessionTempTables[$matches[1]] = 1;
1117
1118                         return true;
1119                 } elseif ( preg_match(
1120                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1121                         $sql,
1122                         $matches
1123                 ) ) {
1124                         $isTemp = isset( $this->sessionTempTables[$matches[1]] );
1125                         unset( $this->sessionTempTables[$matches[1]] );
1126
1127                         return $isTemp;
1128                 } elseif ( preg_match(
1129                         '/^TRUNCATE\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1130                         $sql,
1131                         $matches
1132                 ) ) {
1133                         return isset( $this->sessionTempTables[$matches[1]] );
1134                 } elseif ( preg_match(
1135                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
1136                         $sql,
1137                         $matches
1138                 ) ) {
1139                         return isset( $this->sessionTempTables[$matches[1]] );
1140                 }
1141
1142                 return false;
1143         }
1144
1145         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
1146                 $this->assertTransactionStatus( $sql, $fname );
1147
1148                 # Avoid fatals if close() was called
1149                 $this->assertOpen();
1150
1151                 $priorWritesPending = $this->writesOrCallbacksPending();
1152                 $this->lastQuery = $sql;
1153
1154                 $isWrite = $this->isWriteQuery( $sql );
1155                 if ( $isWrite ) {
1156                         $isNonTempWrite = !$this->registerTempTableOperation( $sql );
1157                 } else {
1158                         $isNonTempWrite = false;
1159                 }
1160
1161                 if ( $isWrite ) {
1162                         if ( $this->getLBInfo( 'replica' ) === true ) {
1163                                 throw new DBError(
1164                                         $this,
1165                                         'Write operations are not allowed on replica database connections.'
1166                                 );
1167                         }
1168                         # In theory, non-persistent writes are allowed in read-only mode, but due to things
1169                         # like https://bugs.mysql.com/bug.php?id=33669 that might not work anyway...
1170                         $reason = $this->getReadOnlyReason();
1171                         if ( $reason !== false ) {
1172                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
1173                         }
1174                         # Set a flag indicating that writes have been done
1175                         $this->lastWriteTime = microtime( true );
1176                 }
1177
1178                 # Add trace comment to the begin of the sql string, right after the operator.
1179                 # Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598)
1180                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
1181
1182                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
1183                 if ( !$this->trxLevel && $this->getFlag( self::DBO_TRX )
1184                         && $this->isTransactableQuery( $sql )
1185                 ) {
1186                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
1187                         $this->trxAutomatic = true;
1188                 }
1189
1190                 # Keep track of whether the transaction has write queries pending
1191                 if ( $this->trxLevel && !$this->trxDoneWrites && $isWrite ) {
1192                         $this->trxDoneWrites = true;
1193                         $this->trxProfiler->transactionWritingIn(
1194                                 $this->server, $this->getDomainID(), $this->trxShortId );
1195                 }
1196
1197                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
1198                         $this->queryLogger->debug( "{$this->getDomainID()} {$commentedSql}" );
1199                 }
1200
1201                 # Send the query to the server and fetch any corresponding errors
1202                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1203                 $lastError = $this->lastError();
1204                 $lastErrno = $this->lastErrno();
1205
1206                 # Try reconnecting if the connection was lost
1207                 if ( $ret === false && $this->wasConnectionLoss() ) {
1208                         # Check if any meaningful session state was lost
1209                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
1210                         # Update session state tracking and try to restore the connection
1211                         $reconnected = $this->replaceLostConnection( __METHOD__ );
1212                         # Silently resend the query to the server if it is safe and possible
1213                         if ( $reconnected && $recoverable ) {
1214                                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1215                                 $lastError = $this->lastError();
1216                                 $lastErrno = $this->lastErrno();
1217
1218                                 if ( $ret === false && $this->wasConnectionLoss() ) {
1219                                         # Query probably causes disconnects; reconnect and do not re-run it
1220                                         $this->replaceLostConnection( __METHOD__ );
1221                                 }
1222                         }
1223                 }
1224
1225                 if ( $ret === false ) {
1226                         if ( $this->trxLevel ) {
1227                                 if ( $this->wasKnownStatementRollbackError() ) {
1228                                         # We're ignoring an error that caused just the current query to be aborted.
1229                                         # But log the cause so we can log a deprecation notice if a caller actually
1230                                         # does ignore it.
1231                                         $this->trxStatusIgnoredCause = [ $lastError, $lastErrno, $fname ];
1232                                 } else {
1233                                         # Either the query was aborted or all queries after BEGIN where aborted.
1234                                         # In the first case, the only options going forward are (a) ROLLBACK, or
1235                                         # (b) ROLLBACK TO SAVEPOINT (if one was set). If the later case, the only
1236                                         # option is ROLLBACK, since the snapshots would have been released.
1237                                         $this->trxStatus = self::STATUS_TRX_ERROR;
1238                                         $this->trxStatusCause =
1239                                                 $this->makeQueryException( $lastError, $lastErrno, $sql, $fname );
1240                                         $tempIgnore = false; // cannot recover
1241                                         $this->trxStatusIgnoredCause = null;
1242                                 }
1243                         }
1244
1245                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname, $tempIgnore );
1246                 }
1247
1248                 return $this->resultObject( $ret );
1249         }
1250
1251         /**
1252          * Wrapper for query() that also handles profiling, logging, and affected row count updates
1253          *
1254          * @param string $sql Original SQL query
1255          * @param string $commentedSql SQL query with debugging/trace comment
1256          * @param bool $isWrite Whether the query is a (non-temporary) write operation
1257          * @param string $fname Name of the calling function
1258          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
1259          *     object for a successful read query, or false on failure
1260          */
1261         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
1262                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1263                 # generalizeSQL() will probably cut down the query to reasonable
1264                 # logging size most of the time. The substr is really just a sanity check.
1265                 if ( $isMaster ) {
1266                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1267                 } else {
1268                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1269                 }
1270
1271                 # Include query transaction state
1272                 $queryProf .= $this->trxShortId ? " [TRX#{$this->trxShortId}]" : "";
1273
1274                 $startTime = microtime( true );
1275                 if ( $this->profiler ) {
1276                         $this->profiler->profileIn( $queryProf );
1277                 }
1278                 $this->affectedRowCount = null;
1279                 $ret = $this->doQuery( $commentedSql );
1280                 $this->affectedRowCount = $this->affectedRows();
1281                 if ( $this->profiler ) {
1282                         $this->profiler->profileOut( $queryProf );
1283                 }
1284                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1285
1286                 unset( $queryProfSection ); // profile out (if set)
1287
1288                 if ( $ret !== false ) {
1289                         $this->lastPing = $startTime;
1290                         if ( $isWrite && $this->trxLevel ) {
1291                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1292                                 $this->trxWriteCallers[] = $fname;
1293                         }
1294                 }
1295
1296                 if ( $sql === self::PING_QUERY ) {
1297                         $this->rttEstimate = $queryRuntime;
1298                 }
1299
1300                 $this->trxProfiler->recordQueryCompletion(
1301                         $queryProf,
1302                         $startTime,
1303                         $isWrite,
1304                         $isWrite ? $this->affectedRows() : $this->numRows( $ret )
1305                 );
1306                 $this->queryLogger->debug( $sql, [
1307                         'method' => $fname,
1308                         'master' => $isMaster,
1309                         'runtime' => $queryRuntime,
1310                 ] );
1311
1312                 return $ret;
1313         }
1314
1315         /**
1316          * Update the estimated run-time of a query, not counting large row lock times
1317          *
1318          * LoadBalancer can be set to rollback transactions that will create huge replication
1319          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1320          * queries, like inserting a row can take a long time due to row locking. This method
1321          * uses some simple heuristics to discount those cases.
1322          *
1323          * @param string $sql A SQL write query
1324          * @param float $runtime Total runtime, including RTT
1325          * @param int $affected Affected row count
1326          */
1327         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1328                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1329                 $indicativeOfReplicaRuntime = true;
1330                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1331                         $verb = $this->getQueryVerb( $sql );
1332                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1333                         if ( $verb === 'INSERT' ) {
1334                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1335                         } elseif ( $verb === 'REPLACE' ) {
1336                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1337                         }
1338                 }
1339
1340                 $this->trxWriteDuration += $runtime;
1341                 $this->trxWriteQueryCount += 1;
1342                 $this->trxWriteAffectedRows += $affected;
1343                 if ( $indicativeOfReplicaRuntime ) {
1344                         $this->trxWriteAdjDuration += $runtime;
1345                         $this->trxWriteAdjQueryCount += 1;
1346                 }
1347         }
1348
1349         /**
1350          * @param string $sql
1351          * @param string $fname
1352          * @throws DBTransactionStateError
1353          */
1354         private function assertTransactionStatus( $sql, $fname ) {
1355                 if ( $this->getQueryVerb( $sql ) === 'ROLLBACK' ) { // transaction/savepoint
1356                         return;
1357                 }
1358
1359                 if ( $this->trxStatus < self::STATUS_TRX_OK ) {
1360                         throw new DBTransactionStateError(
1361                                 $this,
1362                                 "Cannot execute query from $fname while transaction status is ERROR.",
1363                                 [],
1364                                 $this->trxStatusCause
1365                         );
1366                 } elseif ( $this->trxStatus === self::STATUS_TRX_OK && $this->trxStatusIgnoredCause ) {
1367                         list( $iLastError, $iLastErrno, $iFname ) = $this->trxStatusIgnoredCause;
1368                         call_user_func( $this->deprecationLogger,
1369                                 "Caller from $fname ignored an error originally raised from $iFname: " .
1370                                 "[$iLastErrno] $iLastError"
1371                         );
1372                         $this->trxStatusIgnoredCause = null;
1373                 }
1374         }
1375
1376         public function assertNoOpenTransactions() {
1377                 if ( $this->explicitTrxActive() ) {
1378                         throw new DBTransactionError(
1379                                 $this,
1380                                 "Explicit transaction still active. A caller may have caught an error. "
1381                                 . "Open transactions: " . $this->flatAtomicSectionList()
1382                         );
1383                 }
1384         }
1385
1386         /**
1387          * Determine whether or not it is safe to retry queries after a database
1388          * connection is lost
1389          *
1390          * @param string $sql SQL query
1391          * @param bool $priorWritesPending Whether there is a transaction open with
1392          *     possible write queries or transaction pre-commit/idle callbacks
1393          *     waiting on it to finish.
1394          * @return bool True if it is safe to retry the query, false otherwise
1395          */
1396         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1397                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1398                 # Dropped connections also mean that named locks are automatically released.
1399                 # Only allow error suppression in autocommit mode or when the lost transaction
1400                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1401                 if ( $this->namedLocksHeld ) {
1402                         return false; // possible critical section violation
1403                 } elseif ( $this->sessionTempTables ) {
1404                         return false; // tables might be queried latter
1405                 } elseif ( $sql === 'COMMIT' ) {
1406                         return !$priorWritesPending; // nothing written anyway? (T127428)
1407                 } elseif ( $sql === 'ROLLBACK' ) {
1408                         return true; // transaction lost...which is also what was requested :)
1409                 } elseif ( $this->explicitTrxActive() ) {
1410                         return false; // don't drop atomocity and explicit snapshots
1411                 } elseif ( $priorWritesPending ) {
1412                         return false; // prior writes lost from implicit transaction
1413                 }
1414
1415                 return true;
1416         }
1417
1418         /**
1419          * Clean things up after session (and thus transaction) loss
1420          */
1421         private function handleSessionLoss() {
1422                 // Clean up tracking of session-level things...
1423                 // https://dev.mysql.com/doc/refman/5.7/en/implicit-commit.html
1424                 // https://www.postgresql.org/docs/9.2/static/sql-createtable.html (ignoring ON COMMIT)
1425                 $this->sessionTempTables = [];
1426                 // https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
1427                 // https://www.postgresql.org/docs/9.4/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
1428                 $this->namedLocksHeld = [];
1429                 // Session loss implies transaction loss
1430                 $this->handleTransactionLoss();
1431         }
1432
1433         /**
1434          * Clean things up after transaction loss
1435          */
1436         private function handleTransactionLoss() {
1437                 $this->trxLevel = 0;
1438                 $this->trxAtomicCounter = 0;
1439                 $this->trxIdleCallbacks = []; // T67263; transaction already lost
1440                 $this->trxPreCommitCallbacks = []; // T67263; transaction already lost
1441                 try {
1442                         // Handle callbacks in trxEndCallbacks, e.g. onTransactionResolution().
1443                         // If callback suppression is set then the array will remain unhandled.
1444                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1445                 } catch ( Exception $ex ) {
1446                         // Already logged; move on...
1447                 }
1448                 try {
1449                         // Handle callbacks in trxRecurringCallbacks, e.g. setTransactionListener()
1450                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1451                 } catch ( Exception $ex ) {
1452                         // Already logged; move on...
1453                 }
1454         }
1455
1456         /**
1457          * Checks whether the cause of the error is detected to be a timeout.
1458          *
1459          * It returns false by default, and not all engines support detecting this yet.
1460          * If this returns false, it will be treated as a generic query error.
1461          *
1462          * @param string $error Error text
1463          * @param int $errno Error number
1464          * @return bool
1465          */
1466         protected function wasQueryTimeout( $error, $errno ) {
1467                 return false;
1468         }
1469
1470         /**
1471          * Report a query error. Log the error, and if neither the object ignore
1472          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1473          *
1474          * @param string $error
1475          * @param int $errno
1476          * @param string $sql
1477          * @param string $fname
1478          * @param bool $tempIgnore
1479          * @throws DBQueryError
1480          */
1481         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1482                 if ( $tempIgnore ) {
1483                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1484                 } else {
1485                         $exception = $this->makeQueryException( $error, $errno, $sql, $fname );
1486
1487                         throw $exception;
1488                 }
1489         }
1490
1491         /**
1492          * @param string $error
1493          * @param string|int $errno
1494          * @param string $sql
1495          * @param string $fname
1496          * @return DBError
1497          */
1498         private function makeQueryException( $error, $errno, $sql, $fname ) {
1499                 $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1500                 $this->queryLogger->error(
1501                         "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1502                         $this->getLogContext( [
1503                                 'method' => __METHOD__,
1504                                 'errno' => $errno,
1505                                 'error' => $error,
1506                                 'sql1line' => $sql1line,
1507                                 'fname' => $fname,
1508                         ] )
1509                 );
1510                 $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1511                 $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1512                 if ( $wasQueryTimeout ) {
1513                         $e = new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1514                 } else {
1515                         $e = new DBQueryError( $this, $error, $errno, $sql, $fname );
1516                 }
1517
1518                 return $e;
1519         }
1520
1521         public function freeResult( $res ) {
1522         }
1523
1524         public function selectField(
1525                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1526         ) {
1527                 if ( $var === '*' ) { // sanity
1528                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1529                 }
1530
1531                 if ( !is_array( $options ) ) {
1532                         $options = [ $options ];
1533                 }
1534
1535                 $options['LIMIT'] = 1;
1536
1537                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1538                 if ( $res === false || !$this->numRows( $res ) ) {
1539                         return false;
1540                 }
1541
1542                 $row = $this->fetchRow( $res );
1543
1544                 if ( $row !== false ) {
1545                         return reset( $row );
1546                 } else {
1547                         return false;
1548                 }
1549         }
1550
1551         public function selectFieldValues(
1552                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1553         ) {
1554                 if ( $var === '*' ) { // sanity
1555                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1556                 } elseif ( !is_string( $var ) ) { // sanity
1557                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1558                 }
1559
1560                 if ( !is_array( $options ) ) {
1561                         $options = [ $options ];
1562                 }
1563
1564                 $res = $this->select( $table, [ 'value' => $var ], $cond, $fname, $options, $join_conds );
1565                 if ( $res === false ) {
1566                         return false;
1567                 }
1568
1569                 $values = [];
1570                 foreach ( $res as $row ) {
1571                         $values[] = $row->value;
1572                 }
1573
1574                 return $values;
1575         }
1576
1577         /**
1578          * Returns an optional USE INDEX clause to go after the table, and a
1579          * string to go at the end of the query.
1580          *
1581          * @param array $options Associative array of options to be turned into
1582          *   an SQL query, valid keys are listed in the function.
1583          * @return array
1584          * @see Database::select()
1585          */
1586         protected function makeSelectOptions( $options ) {
1587                 $preLimitTail = $postLimitTail = '';
1588                 $startOpts = '';
1589
1590                 $noKeyOptions = [];
1591
1592                 foreach ( $options as $key => $option ) {
1593                         if ( is_numeric( $key ) ) {
1594                                 $noKeyOptions[$option] = true;
1595                         }
1596                 }
1597
1598                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1599
1600                 $preLimitTail .= $this->makeOrderBy( $options );
1601
1602                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1603                         $postLimitTail .= ' FOR UPDATE';
1604                 }
1605
1606                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1607                         $postLimitTail .= ' LOCK IN SHARE MODE';
1608                 }
1609
1610                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1611                         $startOpts .= 'DISTINCT';
1612                 }
1613
1614                 # Various MySQL extensions
1615                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1616                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1617                 }
1618
1619                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1620                         $startOpts .= ' HIGH_PRIORITY';
1621                 }
1622
1623                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1624                         $startOpts .= ' SQL_BIG_RESULT';
1625                 }
1626
1627                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1628                         $startOpts .= ' SQL_BUFFER_RESULT';
1629                 }
1630
1631                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1632                         $startOpts .= ' SQL_SMALL_RESULT';
1633                 }
1634
1635                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1636                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1637                 }
1638
1639                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1640                         $startOpts .= ' SQL_CACHE';
1641                 }
1642
1643                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1644                         $startOpts .= ' SQL_NO_CACHE';
1645                 }
1646
1647                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1648                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1649                 } else {
1650                         $useIndex = '';
1651                 }
1652                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1653                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1654                 } else {
1655                         $ignoreIndex = '';
1656                 }
1657
1658                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1659         }
1660
1661         /**
1662          * Returns an optional GROUP BY with an optional HAVING
1663          *
1664          * @param array $options Associative array of options
1665          * @return string
1666          * @see Database::select()
1667          * @since 1.21
1668          */
1669         protected function makeGroupByWithHaving( $options ) {
1670                 $sql = '';
1671                 if ( isset( $options['GROUP BY'] ) ) {
1672                         $gb = is_array( $options['GROUP BY'] )
1673                                 ? implode( ',', $options['GROUP BY'] )
1674                                 : $options['GROUP BY'];
1675                         $sql .= ' GROUP BY ' . $gb;
1676                 }
1677                 if ( isset( $options['HAVING'] ) ) {
1678                         $having = is_array( $options['HAVING'] )
1679                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1680                                 : $options['HAVING'];
1681                         $sql .= ' HAVING ' . $having;
1682                 }
1683
1684                 return $sql;
1685         }
1686
1687         /**
1688          * Returns an optional ORDER BY
1689          *
1690          * @param array $options Associative array of options
1691          * @return string
1692          * @see Database::select()
1693          * @since 1.21
1694          */
1695         protected function makeOrderBy( $options ) {
1696                 if ( isset( $options['ORDER BY'] ) ) {
1697                         $ob = is_array( $options['ORDER BY'] )
1698                                 ? implode( ',', $options['ORDER BY'] )
1699                                 : $options['ORDER BY'];
1700
1701                         return ' ORDER BY ' . $ob;
1702                 }
1703
1704                 return '';
1705         }
1706
1707         public function select(
1708                 $table, $vars, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1709         ) {
1710                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1711
1712                 return $this->query( $sql, $fname );
1713         }
1714
1715         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1716                 $options = [], $join_conds = []
1717         ) {
1718                 if ( is_array( $vars ) ) {
1719                         $fields = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1720                 } else {
1721                         $fields = $vars;
1722                 }
1723
1724                 $options = (array)$options;
1725                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1726                         ? $options['USE INDEX']
1727                         : [];
1728                 $ignoreIndexes = (
1729                         isset( $options['IGNORE INDEX'] ) &&
1730                         is_array( $options['IGNORE INDEX'] )
1731                 )
1732                         ? $options['IGNORE INDEX']
1733                         : [];
1734
1735                 if (
1736                         $this->selectOptionsIncludeLocking( $options ) &&
1737                         $this->selectFieldsOrOptionsAggregate( $vars, $options )
1738                 ) {
1739                         // Some DB types (postgres/oracle) disallow FOR UPDATE with aggregate
1740                         // functions. Discourage use of such queries to encourage compatibility.
1741                         call_user_func(
1742                                 $this->deprecationLogger,
1743                                 __METHOD__ . ": aggregation used with a locking SELECT ($fname)."
1744                         );
1745                 }
1746
1747                 if ( is_array( $table ) ) {
1748                         $from = ' FROM ' .
1749                                 $this->tableNamesWithIndexClauseOrJOIN(
1750                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1751                 } elseif ( $table != '' ) {
1752                         $from = ' FROM ' .
1753                                 $this->tableNamesWithIndexClauseOrJOIN(
1754                                         [ $table ], $useIndexes, $ignoreIndexes, [] );
1755                 } else {
1756                         $from = '';
1757                 }
1758
1759                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1760                         $this->makeSelectOptions( $options );
1761
1762                 if ( is_array( $conds ) ) {
1763                         $conds = $this->makeList( $conds, self::LIST_AND );
1764                 }
1765
1766                 if ( $conds === null || $conds === false ) {
1767                         $this->queryLogger->warning(
1768                                 __METHOD__
1769                                 . ' called from '
1770                                 . $fname
1771                                 . ' with incorrect parameters: $conds must be a string or an array'
1772                         );
1773                         $conds = '';
1774                 }
1775
1776                 if ( $conds === '' || $conds === '*' ) {
1777                         $sql = "SELECT $startOpts $fields $from $useIndex $ignoreIndex $preLimitTail";
1778                 } elseif ( is_string( $conds ) ) {
1779                         $sql = "SELECT $startOpts $fields $from $useIndex $ignoreIndex " .
1780                                 "WHERE $conds $preLimitTail";
1781                 } else {
1782                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1783                 }
1784
1785                 if ( isset( $options['LIMIT'] ) ) {
1786                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1787                                 $options['OFFSET'] ?? false );
1788                 }
1789                 $sql = "$sql $postLimitTail";
1790
1791                 if ( isset( $options['EXPLAIN'] ) ) {
1792                         $sql = 'EXPLAIN ' . $sql;
1793                 }
1794
1795                 return $sql;
1796         }
1797
1798         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1799                 $options = [], $join_conds = []
1800         ) {
1801                 $options = (array)$options;
1802                 $options['LIMIT'] = 1;
1803                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1804
1805                 if ( $res === false ) {
1806                         return false;
1807                 }
1808
1809                 if ( !$this->numRows( $res ) ) {
1810                         return false;
1811                 }
1812
1813                 $obj = $this->fetchObject( $res );
1814
1815                 return $obj;
1816         }
1817
1818         public function estimateRowCount(
1819                 $table, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1820         ) {
1821                 $conds = $this->normalizeConditions( $conds, $fname );
1822                 $column = $this->extractSingleFieldFromList( $var );
1823                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1824                         $conds[] = "$column IS NOT NULL";
1825                 }
1826
1827                 $res = $this->select(
1828                         $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options, $join_conds
1829                 );
1830                 $row = $res ? $this->fetchRow( $res ) : [];
1831
1832                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1833         }
1834
1835         public function selectRowCount(
1836                 $tables, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1837         ) {
1838                 $conds = $this->normalizeConditions( $conds, $fname );
1839                 $column = $this->extractSingleFieldFromList( $var );
1840                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1841                         $conds[] = "$column IS NOT NULL";
1842                 }
1843
1844                 $res = $this->select(
1845                         [
1846                                 'tmp_count' => $this->buildSelectSubquery(
1847                                         $tables,
1848                                         '1',
1849                                         $conds,
1850                                         $fname,
1851                                         $options,
1852                                         $join_conds
1853                                 )
1854                         ],
1855                         [ 'rowcount' => 'COUNT(*)' ],
1856                         [],
1857                         $fname
1858                 );
1859                 $row = $res ? $this->fetchRow( $res ) : [];
1860
1861                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1862         }
1863
1864         /**
1865          * @param string|array $options
1866          * @return bool
1867          */
1868         private function selectOptionsIncludeLocking( $options ) {
1869                 $options = (array)$options;
1870                 foreach ( [ 'FOR UPDATE', 'LOCK IN SHARE MODE' ] as $lock ) {
1871                         if ( in_array( $lock, $options, true ) ) {
1872                                 return true;
1873                         }
1874                 }
1875
1876                 return false;
1877         }
1878
1879         /**
1880          * @param array|string $fields
1881          * @param array|string $options
1882          * @return bool
1883          */
1884         private function selectFieldsOrOptionsAggregate( $fields, $options ) {
1885                 foreach ( (array)$options as $key => $value ) {
1886                         if ( is_string( $key ) ) {
1887                                 if ( preg_match( '/^(?:GROUP BY|HAVING)$/i', $key ) ) {
1888                                         return true;
1889                                 }
1890                         } elseif ( is_string( $value ) ) {
1891                                 if ( preg_match( '/^(?:DISTINCT|DISTINCTROW)$/i', $value ) ) {
1892                                         return true;
1893                                 }
1894                         }
1895                 }
1896
1897                 $regex = '/^(?:COUNT|MIN|MAX|SUM|GROUP_CONCAT|LISTAGG|ARRAY_AGG)\s*\\(/i';
1898                 foreach ( (array)$fields as $field ) {
1899                         if ( is_string( $field ) && preg_match( $regex, $field ) ) {
1900                                 return true;
1901                         }
1902                 }
1903
1904                 return false;
1905         }
1906
1907         /**
1908          * @param array|string $conds
1909          * @param string $fname
1910          * @return array
1911          */
1912         final protected function normalizeConditions( $conds, $fname ) {
1913                 if ( $conds === null || $conds === false ) {
1914                         $this->queryLogger->warning(
1915                                 __METHOD__
1916                                 . ' called from '
1917                                 . $fname
1918                                 . ' with incorrect parameters: $conds must be a string or an array'
1919                         );
1920                         $conds = '';
1921                 }
1922
1923                 if ( !is_array( $conds ) ) {
1924                         $conds = ( $conds === '' ) ? [] : [ $conds ];
1925                 }
1926
1927                 return $conds;
1928         }
1929
1930         /**
1931          * @param array|string $var Field parameter in the style of select()
1932          * @return string|null Column name or null; ignores aliases
1933          * @throws DBUnexpectedError Errors out if multiple columns are given
1934          */
1935         final protected function extractSingleFieldFromList( $var ) {
1936                 if ( is_array( $var ) ) {
1937                         if ( !$var ) {
1938                                 $column = null;
1939                         } elseif ( count( $var ) == 1 ) {
1940                                 $column = $var[0] ?? reset( $var );
1941                         } else {
1942                                 throw new DBUnexpectedError( $this, __METHOD__ . ': got multiple columns.' );
1943                         }
1944                 } else {
1945                         $column = $var;
1946                 }
1947
1948                 return $column;
1949         }
1950
1951         public function lockForUpdate(
1952                 $table, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1953         ) {
1954                 if ( !$this->trxLevel && !$this->getFlag( self::DBO_TRX ) ) {
1955                         throw new DBUnexpectedError(
1956                                 $this,
1957                                 __METHOD__ . ': no transaction is active nor is DBO_TRX set'
1958                         );
1959                 }
1960
1961                 $options = (array)$options;
1962                 $options[] = 'FOR UPDATE';
1963
1964                 return $this->selectRowCount( $table, '*', $conds, $fname, $options, $join_conds );
1965         }
1966
1967         /**
1968          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1969          * It's only slightly flawed. Don't use for anything important.
1970          *
1971          * @param string $sql A SQL Query
1972          *
1973          * @return string
1974          */
1975         protected static function generalizeSQL( $sql ) {
1976                 # This does the same as the regexp below would do, but in such a way
1977                 # as to avoid crashing php on some large strings.
1978                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1979
1980                 $sql = str_replace( "\\\\", '', $sql );
1981                 $sql = str_replace( "\\'", '', $sql );
1982                 $sql = str_replace( "\\\"", '', $sql );
1983                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1984                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1985
1986                 # All newlines, tabs, etc replaced by single space
1987                 $sql = preg_replace( '/\s+/', ' ', $sql );
1988
1989                 # All numbers => N,
1990                 # except the ones surrounded by characters, e.g. l10n
1991                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1992                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1993
1994                 return $sql;
1995         }
1996
1997         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1998                 $info = $this->fieldInfo( $table, $field );
1999
2000                 return (bool)$info;
2001         }
2002
2003         public function indexExists( $table, $index, $fname = __METHOD__ ) {
2004                 if ( !$this->tableExists( $table ) ) {
2005                         return null;
2006                 }
2007
2008                 $info = $this->indexInfo( $table, $index, $fname );
2009                 if ( is_null( $info ) ) {
2010                         return null;
2011                 } else {
2012                         return $info !== false;
2013                 }
2014         }
2015
2016         abstract public function tableExists( $table, $fname = __METHOD__ );
2017
2018         public function indexUnique( $table, $index ) {
2019                 $indexInfo = $this->indexInfo( $table, $index );
2020
2021                 if ( !$indexInfo ) {
2022                         return null;
2023                 }
2024
2025                 return !$indexInfo[0]->Non_unique;
2026         }
2027
2028         /**
2029          * Helper for Database::insert().
2030          *
2031          * @param array $options
2032          * @return string
2033          */
2034         protected function makeInsertOptions( $options ) {
2035                 return implode( ' ', $options );
2036         }
2037
2038         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
2039                 # No rows to insert, easy just return now
2040                 if ( !count( $a ) ) {
2041                         return true;
2042                 }
2043
2044                 $table = $this->tableName( $table );
2045
2046                 if ( !is_array( $options ) ) {
2047                         $options = [ $options ];
2048                 }
2049
2050                 $options = $this->makeInsertOptions( $options );
2051
2052                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
2053                         $multi = true;
2054                         $keys = array_keys( $a[0] );
2055                 } else {
2056                         $multi = false;
2057                         $keys = array_keys( $a );
2058                 }
2059
2060                 $sql = 'INSERT ' . $options .
2061                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
2062
2063                 if ( $multi ) {
2064                         $first = true;
2065                         foreach ( $a as $row ) {
2066                                 if ( $first ) {
2067                                         $first = false;
2068                                 } else {
2069                                         $sql .= ',';
2070                                 }
2071                                 $sql .= '(' . $this->makeList( $row ) . ')';
2072                         }
2073                 } else {
2074                         $sql .= '(' . $this->makeList( $a ) . ')';
2075                 }
2076
2077                 $this->query( $sql, $fname );
2078
2079                 return true;
2080         }
2081
2082         /**
2083          * Make UPDATE options array for Database::makeUpdateOptions
2084          *
2085          * @param array $options
2086          * @return array
2087          */
2088         protected function makeUpdateOptionsArray( $options ) {
2089                 if ( !is_array( $options ) ) {
2090                         $options = [ $options ];
2091                 }
2092
2093                 $opts = [];
2094
2095                 if ( in_array( 'IGNORE', $options ) ) {
2096                         $opts[] = 'IGNORE';
2097                 }
2098
2099                 return $opts;
2100         }
2101
2102         /**
2103          * Make UPDATE options for the Database::update function
2104          *
2105          * @param array $options The options passed to Database::update
2106          * @return string
2107          */
2108         protected function makeUpdateOptions( $options ) {
2109                 $opts = $this->makeUpdateOptionsArray( $options );
2110
2111                 return implode( ' ', $opts );
2112         }
2113
2114         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
2115                 $table = $this->tableName( $table );
2116                 $opts = $this->makeUpdateOptions( $options );
2117                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
2118
2119                 if ( $conds !== [] && $conds !== '*' ) {
2120                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
2121                 }
2122
2123                 $this->query( $sql, $fname );
2124
2125                 return true;
2126         }
2127
2128         public function makeList( $a, $mode = self::LIST_COMMA ) {
2129                 if ( !is_array( $a ) ) {
2130                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
2131                 }
2132
2133                 $first = true;
2134                 $list = '';
2135
2136                 foreach ( $a as $field => $value ) {
2137                         if ( !$first ) {
2138                                 if ( $mode == self::LIST_AND ) {
2139                                         $list .= ' AND ';
2140                                 } elseif ( $mode == self::LIST_OR ) {
2141                                         $list .= ' OR ';
2142                                 } else {
2143                                         $list .= ',';
2144                                 }
2145                         } else {
2146                                 $first = false;
2147                         }
2148
2149                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
2150                                 $list .= "($value)";
2151                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
2152                                 $list .= "$value";
2153                         } elseif (
2154                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
2155                         ) {
2156                                 // Remove null from array to be handled separately if found
2157                                 $includeNull = false;
2158                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
2159                                         $includeNull = true;
2160                                         unset( $value[$nullKey] );
2161                                 }
2162                                 if ( count( $value ) == 0 && !$includeNull ) {
2163                                         throw new InvalidArgumentException(
2164                                                 __METHOD__ . ": empty input for field $field" );
2165                                 } elseif ( count( $value ) == 0 ) {
2166                                         // only check if $field is null
2167                                         $list .= "$field IS NULL";
2168                                 } else {
2169                                         // IN clause contains at least one valid element
2170                                         if ( $includeNull ) {
2171                                                 // Group subconditions to ensure correct precedence
2172                                                 $list .= '(';
2173                                         }
2174                                         if ( count( $value ) == 1 ) {
2175                                                 // Special-case single values, as IN isn't terribly efficient
2176                                                 // Don't necessarily assume the single key is 0; we don't
2177                                                 // enforce linear numeric ordering on other arrays here.
2178                                                 $value = array_values( $value )[0];
2179                                                 $list .= $field . " = " . $this->addQuotes( $value );
2180                                         } else {
2181                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
2182                                         }
2183                                         // if null present in array, append IS NULL
2184                                         if ( $includeNull ) {
2185                                                 $list .= " OR $field IS NULL)";
2186                                         }
2187                                 }
2188                         } elseif ( $value === null ) {
2189                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
2190                                         $list .= "$field IS ";
2191                                 } elseif ( $mode == self::LIST_SET ) {
2192                                         $list .= "$field = ";
2193                                 }
2194                                 $list .= 'NULL';
2195                         } else {
2196                                 if (
2197                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
2198                                 ) {
2199                                         $list .= "$field = ";
2200                                 }
2201                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
2202                         }
2203                 }
2204
2205                 return $list;
2206         }
2207
2208         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2209                 $conds = [];
2210
2211                 foreach ( $data as $base => $sub ) {
2212                         if ( count( $sub ) ) {
2213                                 $conds[] = $this->makeList(
2214                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
2215                                         self::LIST_AND );
2216                         }
2217                 }
2218
2219                 if ( $conds ) {
2220                         return $this->makeList( $conds, self::LIST_OR );
2221                 } else {
2222                         // Nothing to search for...
2223                         return false;
2224                 }
2225         }
2226
2227         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2228                 return $valuename;
2229         }
2230
2231         public function bitNot( $field ) {
2232                 return "(~$field)";
2233         }
2234
2235         public function bitAnd( $fieldLeft, $fieldRight ) {
2236                 return "($fieldLeft & $fieldRight)";
2237         }
2238
2239         public function bitOr( $fieldLeft, $fieldRight ) {
2240                 return "($fieldLeft | $fieldRight)";
2241         }
2242
2243         public function buildConcat( $stringList ) {
2244                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2245         }
2246
2247         public function buildGroupConcatField(
2248                 $delim, $table, $field, $conds = '', $join_conds = []
2249         ) {
2250                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
2251
2252                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
2253         }
2254
2255         public function buildSubstring( $input, $startPosition, $length = null ) {
2256                 $this->assertBuildSubstringParams( $startPosition, $length );
2257                 $functionBody = "$input FROM $startPosition";
2258                 if ( $length !== null ) {
2259                         $functionBody .= " FOR $length";
2260                 }
2261                 return 'SUBSTRING(' . $functionBody . ')';
2262         }
2263
2264         /**
2265          * Check type and bounds for parameters to self::buildSubstring()
2266          *
2267          * All supported databases have substring functions that behave the same for
2268          * positive $startPosition and non-negative $length, but behaviors differ when
2269          * given 0 or negative $startPosition or negative $length. The simplest
2270          * solution to that is to just forbid those values.
2271          *
2272          * @param int $startPosition
2273          * @param int|null $length
2274          * @since 1.31
2275          */
2276         protected function assertBuildSubstringParams( $startPosition, $length ) {
2277                 if ( !is_int( $startPosition ) || $startPosition <= 0 ) {
2278                         throw new InvalidArgumentException(
2279                                 '$startPosition must be a positive integer'
2280                         );
2281                 }
2282                 if ( !( is_int( $length ) && $length >= 0 || $length === null ) ) {
2283                         throw new InvalidArgumentException(
2284                                 '$length must be null or an integer greater than or equal to 0'
2285                         );
2286                 }
2287         }
2288
2289         public function buildStringCast( $field ) {
2290                 // In theory this should work for any standards-compliant
2291                 // SQL implementation, although it may not be the best way to do it.
2292                 return "CAST( $field AS CHARACTER )";
2293         }
2294
2295         public function buildIntegerCast( $field ) {
2296                 return 'CAST( ' . $field . ' AS INTEGER )';
2297         }
2298
2299         public function buildSelectSubquery(
2300                 $table, $vars, $conds = '', $fname = __METHOD__,
2301                 $options = [], $join_conds = []
2302         ) {
2303                 return new Subquery(
2304                         $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds )
2305                 );
2306         }
2307
2308         public function databasesAreIndependent() {
2309                 return false;
2310         }
2311
2312         final public function selectDB( $db ) {
2313                 $this->selectDomain( new DatabaseDomain(
2314                         $db,
2315                         $this->currentDomain->getSchema(),
2316                         $this->currentDomain->getTablePrefix()
2317                 ) );
2318
2319                 return true;
2320         }
2321
2322         final public function selectDomain( $domain ) {
2323                 $this->doSelectDomain( DatabaseDomain::newFromId( $domain ) );
2324         }
2325
2326         protected function doSelectDomain( DatabaseDomain $domain ) {
2327                 $this->currentDomain = $domain;
2328         }
2329
2330         public function getDBname() {
2331                 return $this->currentDomain->getDatabase();
2332         }
2333
2334         public function getServer() {
2335                 return $this->server;
2336         }
2337
2338         public function tableName( $name, $format = 'quoted' ) {
2339                 if ( $name instanceof Subquery ) {
2340                         throw new DBUnexpectedError(
2341                                 $this,
2342                                 __METHOD__ . ': got Subquery instance when expecting a string.'
2343                         );
2344                 }
2345
2346                 # Skip the entire process when we have a string quoted on both ends.
2347                 # Note that we check the end so that we will still quote any use of
2348                 # use of `database`.table. But won't break things if someone wants
2349                 # to query a database table with a dot in the name.
2350                 if ( $this->isQuotedIdentifier( $name ) ) {
2351                         return $name;
2352                 }
2353
2354                 # Lets test for any bits of text that should never show up in a table
2355                 # name. Basically anything like JOIN or ON which are actually part of
2356                 # SQL queries, but may end up inside of the table value to combine
2357                 # sql. Such as how the API is doing.
2358                 # Note that we use a whitespace test rather than a \b test to avoid
2359                 # any remote case where a word like on may be inside of a table name
2360                 # surrounded by symbols which may be considered word breaks.
2361                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2362                         $this->queryLogger->warning(
2363                                 __METHOD__ . ": use of subqueries is not supported this way.",
2364                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
2365                         );
2366
2367                         return $name;
2368                 }
2369
2370                 # Split database and table into proper variables.
2371                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
2372
2373                 # Quote $table and apply the prefix if not quoted.
2374                 # $tableName might be empty if this is called from Database::replaceVars()
2375                 $tableName = "{$prefix}{$table}";
2376                 if ( $format === 'quoted'
2377                         && !$this->isQuotedIdentifier( $tableName )
2378                         && $tableName !== ''
2379                 ) {
2380                         $tableName = $this->addIdentifierQuotes( $tableName );
2381                 }
2382
2383                 # Quote $schema and $database and merge them with the table name if needed
2384                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
2385                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
2386
2387                 return $tableName;
2388         }
2389
2390         /**
2391          * Get the table components needed for a query given the currently selected database
2392          *
2393          * @param string $name Table name in the form of db.schema.table, db.table, or table
2394          * @return array (DB name or "" for default, schema name, table prefix, table name)
2395          */
2396         protected function qualifiedTableComponents( $name ) {
2397                 # We reverse the explode so that database.table and table both output the correct table.
2398                 $dbDetails = explode( '.', $name, 3 );
2399                 if ( count( $dbDetails ) == 3 ) {
2400                         list( $database, $schema, $table ) = $dbDetails;
2401                         # We don't want any prefix added in this case
2402                         $prefix = '';
2403                 } elseif ( count( $dbDetails ) == 2 ) {
2404                         list( $database, $table ) = $dbDetails;
2405                         # We don't want any prefix added in this case
2406                         $prefix = '';
2407                         # In dbs that support it, $database may actually be the schema
2408                         # but that doesn't affect any of the functionality here
2409                         $schema = '';
2410                 } else {
2411                         list( $table ) = $dbDetails;
2412                         if ( isset( $this->tableAliases[$table] ) ) {
2413                                 $database = $this->tableAliases[$table]['dbname'];
2414                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
2415                                         ? $this->tableAliases[$table]['schema']
2416                                         : $this->relationSchemaQualifier();
2417                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
2418                                         ? $this->tableAliases[$table]['prefix']
2419                                         : $this->tablePrefix();
2420                         } else {
2421                                 $database = '';
2422                                 $schema = $this->relationSchemaQualifier(); # Default schema
2423                                 $prefix = $this->tablePrefix(); # Default prefix
2424                         }
2425                 }
2426
2427                 return [ $database, $schema, $prefix, $table ];
2428         }
2429
2430         /**
2431          * @param string|null $namespace Database or schema
2432          * @param string $relation Name of table, view, sequence, etc...
2433          * @param string $format One of (raw, quoted)
2434          * @return string Relation name with quoted and merged $namespace as needed
2435          */
2436         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
2437                 if ( strlen( $namespace ) ) {
2438                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
2439                                 $namespace = $this->addIdentifierQuotes( $namespace );
2440                         }
2441                         $relation = $namespace . '.' . $relation;
2442                 }
2443
2444                 return $relation;
2445         }
2446
2447         public function tableNames() {
2448                 $inArray = func_get_args();
2449                 $retVal = [];
2450
2451                 foreach ( $inArray as $name ) {
2452                         $retVal[$name] = $this->tableName( $name );
2453                 }
2454
2455                 return $retVal;
2456         }
2457
2458         public function tableNamesN() {
2459                 $inArray = func_get_args();
2460                 $retVal = [];
2461
2462                 foreach ( $inArray as $name ) {
2463                         $retVal[] = $this->tableName( $name );
2464                 }
2465
2466                 return $retVal;
2467         }
2468
2469         /**
2470          * Get an aliased table name
2471          *
2472          * This returns strings like "tableName AS newTableName" for aliased tables
2473          * and "(SELECT * from tableA) newTablename" for subqueries (e.g. derived tables)
2474          *
2475          * @see Database::tableName()
2476          * @param string|Subquery $table Table name or object with a 'sql' field
2477          * @param string|bool $alias Table alias (optional)
2478          * @return string SQL name for aliased table. Will not alias a table to its own name
2479          */
2480         protected function tableNameWithAlias( $table, $alias = false ) {
2481                 if ( is_string( $table ) ) {
2482                         $quotedTable = $this->tableName( $table );
2483                 } elseif ( $table instanceof Subquery ) {
2484                         $quotedTable = (string)$table;
2485                 } else {
2486                         throw new InvalidArgumentException( "Table must be a string or Subquery." );
2487                 }
2488
2489                 if ( !strlen( $alias ) || $alias === $table ) {
2490                         if ( $table instanceof Subquery ) {
2491                                 throw new InvalidArgumentException( "Subquery table missing alias." );
2492                         }
2493
2494                         return $quotedTable;
2495                 } else {
2496                         return $quotedTable . ' ' . $this->addIdentifierQuotes( $alias );
2497                 }
2498         }
2499
2500         /**
2501          * Gets an array of aliased table names
2502          *
2503          * @param array $tables [ [alias] => table ]
2504          * @return string[] See tableNameWithAlias()
2505          */
2506         protected function tableNamesWithAlias( $tables ) {
2507                 $retval = [];
2508                 foreach ( $tables as $alias => $table ) {
2509                         if ( is_numeric( $alias ) ) {
2510                                 $alias = $table;
2511                         }
2512                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2513                 }
2514
2515                 return $retval;
2516         }
2517
2518         /**
2519          * Get an aliased field name
2520          * e.g. fieldName AS newFieldName
2521          *
2522          * @param string $name Field name
2523          * @param string|bool $alias Alias (optional)
2524          * @return string SQL name for aliased field. Will not alias a field to its own name
2525          */
2526         protected function fieldNameWithAlias( $name, $alias = false ) {
2527                 if ( !$alias || (string)$alias === (string)$name ) {
2528                         return $name;
2529                 } else {
2530                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
2531                 }
2532         }
2533
2534         /**
2535          * Gets an array of aliased field names
2536          *
2537          * @param array $fields [ [alias] => field ]
2538          * @return string[] See fieldNameWithAlias()
2539          */
2540         protected function fieldNamesWithAlias( $fields ) {
2541                 $retval = [];
2542                 foreach ( $fields as $alias => $field ) {
2543                         if ( is_numeric( $alias ) ) {
2544                                 $alias = $field;
2545                         }
2546                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2547                 }
2548
2549                 return $retval;
2550         }
2551
2552         /**
2553          * Get the aliased table name clause for a FROM clause
2554          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2555          *
2556          * @param array $tables ( [alias] => table )
2557          * @param array $use_index Same as for select()
2558          * @param array $ignore_index Same as for select()
2559          * @param array $join_conds Same as for select()
2560          * @return string
2561          */
2562         protected function tableNamesWithIndexClauseOrJOIN(
2563                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2564         ) {
2565                 $ret = [];
2566                 $retJOIN = [];
2567                 $use_index = (array)$use_index;
2568                 $ignore_index = (array)$ignore_index;
2569                 $join_conds = (array)$join_conds;
2570
2571                 foreach ( $tables as $alias => $table ) {
2572                         if ( !is_string( $alias ) ) {
2573                                 // No alias? Set it equal to the table name
2574                                 $alias = $table;
2575                         }
2576
2577                         if ( is_array( $table ) ) {
2578                                 // A parenthesized group
2579                                 if ( count( $table ) > 1 ) {
2580                                         $joinedTable = '(' .
2581                                                 $this->tableNamesWithIndexClauseOrJOIN(
2582                                                         $table, $use_index, $ignore_index, $join_conds ) . ')';
2583                                 } else {
2584                                         // Degenerate case
2585                                         $innerTable = reset( $table );
2586                                         $innerAlias = key( $table );
2587                                         $joinedTable = $this->tableNameWithAlias(
2588                                                 $innerTable,
2589                                                 is_string( $innerAlias ) ? $innerAlias : $innerTable
2590                                         );
2591                                 }
2592                         } else {
2593                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2594                         }
2595
2596                         // Is there a JOIN clause for this table?
2597                         if ( isset( $join_conds[$alias] ) ) {
2598                                 list( $joinType, $conds ) = $join_conds[$alias];
2599                                 $tableClause = $joinType;
2600                                 $tableClause .= ' ' . $joinedTable;
2601                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2602                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2603                                         if ( $use != '' ) {
2604                                                 $tableClause .= ' ' . $use;
2605                                         }
2606                                 }
2607                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2608                                         $ignore = $this->ignoreIndexClause(
2609                                                 implode( ',', (array)$ignore_index[$alias] ) );
2610                                         if ( $ignore != '' ) {
2611                                                 $tableClause .= ' ' . $ignore;
2612                                         }
2613                                 }
2614                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2615                                 if ( $on != '' ) {
2616                                         $tableClause .= ' ON (' . $on . ')';
2617                                 }
2618
2619                                 $retJOIN[] = $tableClause;
2620                         } elseif ( isset( $use_index[$alias] ) ) {
2621                                 // Is there an INDEX clause for this table?
2622                                 $tableClause = $joinedTable;
2623                                 $tableClause .= ' ' . $this->useIndexClause(
2624                                                 implode( ',', (array)$use_index[$alias] )
2625                                         );
2626
2627                                 $ret[] = $tableClause;
2628                         } elseif ( isset( $ignore_index[$alias] ) ) {
2629                                 // Is there an INDEX clause for this table?
2630                                 $tableClause = $joinedTable;
2631                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2632                                                 implode( ',', (array)$ignore_index[$alias] )
2633                                         );
2634
2635                                 $ret[] = $tableClause;
2636                         } else {
2637                                 $tableClause = $joinedTable;
2638
2639                                 $ret[] = $tableClause;
2640                         }
2641                 }
2642
2643                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2644                 $implicitJoins = $ret ? implode( ',', $ret ) : "";
2645                 $explicitJoins = $retJOIN ? implode( ' ', $retJOIN ) : "";
2646
2647                 // Compile our final table clause
2648                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2649         }
2650
2651         /**
2652          * Allows for index remapping in queries where this is not consistent across DBMS
2653          *
2654          * @param string $index
2655          * @return string
2656          */
2657         protected function indexName( $index ) {
2658                 return $this->indexAliases[$index] ?? $index;
2659         }
2660
2661         public function addQuotes( $s ) {
2662                 if ( $s instanceof Blob ) {
2663                         $s = $s->fetch();
2664                 }
2665                 if ( $s === null ) {
2666                         return 'NULL';
2667                 } elseif ( is_bool( $s ) ) {
2668                         return (int)$s;
2669                 } else {
2670                         # This will also quote numeric values. This should be harmless,
2671                         # and protects against weird problems that occur when they really
2672                         # _are_ strings such as article titles and string->number->string
2673                         # conversion is not 1:1.
2674                         return "'" . $this->strencode( $s ) . "'";
2675                 }
2676         }
2677
2678         /**
2679          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2680          * MySQL uses `backticks` while basically everything else uses double quotes.
2681          * Since MySQL is the odd one out here the double quotes are our generic
2682          * and we implement backticks in DatabaseMysqlBase.
2683          *
2684          * @param string $s
2685          * @return string
2686          */
2687         public function addIdentifierQuotes( $s ) {
2688                 return '"' . str_replace( '"', '""', $s ) . '"';
2689         }
2690
2691         /**
2692          * Returns if the given identifier looks quoted or not according to
2693          * the database convention for quoting identifiers .
2694          *
2695          * @note Do not use this to determine if untrusted input is safe.
2696          *   A malicious user can trick this function.
2697          * @param string $name
2698          * @return bool
2699          */
2700         public function isQuotedIdentifier( $name ) {
2701                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2702         }
2703
2704         /**
2705          * @param string $s
2706          * @param string $escapeChar
2707          * @return string
2708          */
2709         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2710                 return str_replace( [ $escapeChar, '%', '_' ],
2711                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2712                         $s );
2713         }
2714
2715         public function buildLike() {
2716                 $params = func_get_args();
2717
2718                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2719                         $params = $params[0];
2720                 }
2721
2722                 $s = '';
2723
2724                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2725                 // may escape backslashes, creating problems of double escaping. The `
2726                 // character has good cross-DBMS compatibility, avoiding special operators
2727                 // in MS SQL like ^ and %
2728                 $escapeChar = '`';
2729
2730                 foreach ( $params as $value ) {
2731                         if ( $value instanceof LikeMatch ) {
2732                                 $s .= $value->toString();
2733                         } else {
2734                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2735                         }
2736                 }
2737
2738                 return ' LIKE ' .
2739                         $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2740         }
2741
2742         public function anyChar() {
2743                 return new LikeMatch( '_' );
2744         }
2745
2746         public function anyString() {
2747                 return new LikeMatch( '%' );
2748         }
2749
2750         public function nextSequenceValue( $seqName ) {
2751                 return null;
2752         }
2753
2754         /**
2755          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2756          * is only needed because a) MySQL must be as efficient as possible due to
2757          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2758          * which index to pick. Anyway, other databases might have different
2759          * indexes on a given table. So don't bother overriding this unless you're
2760          * MySQL.
2761          * @param string $index
2762          * @return string
2763          */
2764         public function useIndexClause( $index ) {
2765                 return '';
2766         }
2767
2768         /**
2769          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2770          * is only needed because a) MySQL must be as efficient as possible due to
2771          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2772          * which index to pick. Anyway, other databases might have different
2773          * indexes on a given table. So don't bother overriding this unless you're
2774          * MySQL.
2775          * @param string $index
2776          * @return string
2777          */
2778         public function ignoreIndexClause( $index ) {
2779                 return '';
2780         }
2781
2782         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2783                 if ( count( $rows ) == 0 ) {
2784                         return;
2785                 }
2786
2787                 // Single row case
2788                 if ( !is_array( reset( $rows ) ) ) {
2789                         $rows = [ $rows ];
2790                 }
2791
2792                 try {
2793                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2794                         $affectedRowCount = 0;
2795                         foreach ( $rows as $row ) {
2796                                 // Delete rows which collide with this one
2797                                 $indexWhereClauses = [];
2798                                 foreach ( $uniqueIndexes as $index ) {
2799                                         $indexColumns = (array)$index;
2800                                         $indexRowValues = array_intersect_key( $row, array_flip( $indexColumns ) );
2801                                         if ( count( $indexRowValues ) != count( $indexColumns ) ) {
2802                                                 throw new DBUnexpectedError(
2803                                                         $this,
2804                                                         'New record does not provide all values for unique key (' .
2805                                                         implode( ', ', $indexColumns ) . ')'
2806                                                 );
2807                                         } elseif ( in_array( null, $indexRowValues, true ) ) {
2808                                                 throw new DBUnexpectedError(
2809                                                         $this,
2810                                                         'New record has a null value for unique key (' .
2811                                                         implode( ', ', $indexColumns ) . ')'
2812                                                 );
2813                                         }
2814                                         $indexWhereClauses[] = $this->makeList( $indexRowValues, LIST_AND );
2815                                 }
2816
2817                                 if ( $indexWhereClauses ) {
2818                                         $this->delete( $table, $this->makeList( $indexWhereClauses, LIST_OR ), $fname );
2819                                         $affectedRowCount += $this->affectedRows();
2820                                 }
2821
2822                                 // Now insert the row
2823                                 $this->insert( $table, $row, $fname );
2824                                 $affectedRowCount += $this->affectedRows();
2825                         }
2826                         $this->endAtomic( $fname );
2827                         $this->affectedRowCount = $affectedRowCount;
2828                 } catch ( Exception $e ) {
2829                         $this->cancelAtomic( $fname );
2830                         throw $e;
2831                 }
2832         }
2833
2834         /**
2835          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2836          * statement.
2837          *
2838          * @param string $table Table name
2839          * @param array|string $rows Row(s) to insert
2840          * @param string $fname Caller function name
2841          */
2842         protected function nativeReplace( $table, $rows, $fname ) {
2843                 $table = $this->tableName( $table );
2844
2845                 # Single row case
2846                 if ( !is_array( reset( $rows ) ) ) {
2847                         $rows = [ $rows ];
2848                 }
2849
2850                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2851                 $first = true;
2852
2853                 foreach ( $rows as $row ) {
2854                         if ( $first ) {
2855                                 $first = false;
2856                         } else {
2857                                 $sql .= ',';
2858                         }
2859
2860                         $sql .= '(' . $this->makeList( $row ) . ')';
2861                 }
2862
2863                 $this->query( $sql, $fname );
2864         }
2865
2866         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2867                 $fname = __METHOD__
2868         ) {
2869                 if ( $rows === [] ) {
2870                         return true; // nothing to do
2871                 }
2872
2873                 if ( !is_array( reset( $rows ) ) ) {
2874                         $rows = [ $rows ];
2875                 }
2876
2877                 if ( count( $uniqueIndexes ) ) {
2878                         $clauses = []; // list WHERE clauses that each identify a single row
2879                         foreach ( $rows as $row ) {
2880                                 foreach ( $uniqueIndexes as $index ) {
2881                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2882                                         $rowKey = []; // unique key to this row
2883                                         foreach ( $index as $column ) {
2884                                                 $rowKey[$column] = $row[$column];
2885                                         }
2886                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2887                                 }
2888                         }
2889                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2890                 } else {
2891                         $where = false;
2892                 }
2893
2894                 $affectedRowCount = 0;
2895                 try {
2896                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2897                         # Update any existing conflicting row(s)
2898                         if ( $where !== false ) {
2899                                 $this->update( $table, $set, $where, $fname );
2900                                 $affectedRowCount += $this->affectedRows();
2901                         }
2902                         # Now insert any non-conflicting row(s)
2903                         $this->insert( $table, $rows, $fname, [ 'IGNORE' ] );
2904                         $affectedRowCount += $this->affectedRows();
2905                         $this->endAtomic( $fname );
2906                         $this->affectedRowCount = $affectedRowCount;
2907                 } catch ( Exception $e ) {
2908                         $this->cancelAtomic( $fname );
2909                         throw $e;
2910                 }
2911
2912                 return true;
2913         }
2914
2915         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2916                 $fname = __METHOD__
2917         ) {
2918                 if ( !$conds ) {
2919                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2920                 }
2921
2922                 $delTable = $this->tableName( $delTable );
2923                 $joinTable = $this->tableName( $joinTable );
2924                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2925                 if ( $conds != '*' ) {
2926                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2927                 }
2928                 $sql .= ')';
2929
2930                 $this->query( $sql, $fname );
2931         }
2932
2933         public function textFieldSize( $table, $field ) {
2934                 $table = $this->tableName( $table );
2935                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2936                 $res = $this->query( $sql, __METHOD__ );
2937                 $row = $this->fetchObject( $res );
2938
2939                 $m = [];
2940
2941                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2942                         $size = $m[1];
2943                 } else {
2944                         $size = -1;
2945                 }
2946
2947                 return $size;
2948         }
2949
2950         public function delete( $table, $conds, $fname = __METHOD__ ) {
2951                 if ( !$conds ) {
2952                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2953                 }
2954
2955                 $table = $this->tableName( $table );
2956                 $sql = "DELETE FROM $table";
2957
2958                 if ( $conds != '*' ) {
2959                         if ( is_array( $conds ) ) {
2960                                 $conds = $this->makeList( $conds, self::LIST_AND );
2961                         }
2962                         $sql .= ' WHERE ' . $conds;
2963                 }
2964
2965                 $this->query( $sql, $fname );
2966
2967                 return true;
2968         }
2969
2970         final public function insertSelect(
2971                 $destTable, $srcTable, $varMap, $conds,
2972                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2973         ) {
2974                 static $hints = [ 'NO_AUTO_COLUMNS' ];
2975
2976                 $insertOptions = (array)$insertOptions;
2977                 $selectOptions = (array)$selectOptions;
2978
2979                 if ( $this->cliMode && $this->isInsertSelectSafe( $insertOptions, $selectOptions ) ) {
2980                         // For massive migrations with downtime, we don't want to select everything
2981                         // into memory and OOM, so do all this native on the server side if possible.
2982                         $this->nativeInsertSelect(
2983                                 $destTable,
2984                                 $srcTable,
2985                                 $varMap,
2986                                 $conds,
2987                                 $fname,
2988                                 array_diff( $insertOptions, $hints ),
2989                                 $selectOptions,
2990                                 $selectJoinConds
2991                         );
2992                 } else {
2993                         $this->nonNativeInsertSelect(
2994                                 $destTable,
2995                                 $srcTable,
2996                                 $varMap,
2997                                 $conds,
2998                                 $fname,
2999                                 array_diff( $insertOptions, $hints ),
3000                                 $selectOptions,
3001                                 $selectJoinConds
3002                         );
3003                 }
3004
3005                 return true;
3006         }
3007
3008         /**
3009          * @param array $insertOptions INSERT options
3010          * @param array $selectOptions SELECT options
3011          * @return bool Whether an INSERT SELECT with these options will be replication safe
3012          * @since 1.31
3013          */
3014         protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
3015                 return true;
3016         }
3017
3018         /**
3019          * Implementation of insertSelect() based on select() and insert()
3020          *
3021          * @see IDatabase::insertSelect()
3022          * @since 1.30
3023          * @param string $destTable
3024          * @param string|array $srcTable
3025          * @param array $varMap
3026          * @param array $conds
3027          * @param string $fname
3028          * @param array $insertOptions
3029          * @param array $selectOptions
3030          * @param array $selectJoinConds
3031          */
3032         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
3033                 $fname = __METHOD__,
3034                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
3035         ) {
3036                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
3037                 // on only the master (without needing row-based-replication). It also makes it easy to
3038                 // know how big the INSERT is going to be.
3039                 $fields = [];
3040                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
3041                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
3042                 }
3043                 $selectOptions[] = 'FOR UPDATE';
3044                 $res = $this->select(
3045                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
3046                 );
3047                 if ( !$res ) {
3048                         return;
3049                 }
3050
3051                 try {
3052                         $affectedRowCount = 0;
3053                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
3054                         $rows = [];
3055                         $ok = true;
3056                         foreach ( $res as $row ) {
3057                                 $rows[] = (array)$row;
3058
3059                                 // Avoid inserts that are too huge
3060                                 if ( count( $rows ) >= $this->nonNativeInsertSelectBatchSize ) {
3061                                         $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
3062                                         if ( !$ok ) {
3063                                                 break;
3064                                         }
3065                                         $affectedRowCount += $this->affectedRows();
3066                                         $rows = [];
3067                                 }
3068                         }
3069                         if ( $rows && $ok ) {
3070                                 $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
3071                                 if ( $ok ) {
3072                                         $affectedRowCount += $this->affectedRows();
3073                                 }
3074                         }
3075                         if ( $ok ) {
3076                                 $this->endAtomic( $fname );
3077                                 $this->affectedRowCount = $affectedRowCount;
3078                         } else {
3079                                 $this->cancelAtomic( $fname );
3080                         }
3081                 } catch ( Exception $e ) {
3082                         $this->cancelAtomic( $fname );
3083                         throw $e;
3084                 }
3085         }
3086
3087         /**
3088          * Native server-side implementation of insertSelect() for situations where
3089          * we don't want to select everything into memory
3090          *
3091          * @see IDatabase::insertSelect()
3092          * @param string $destTable
3093          * @param string|array $srcTable
3094          * @param array $varMap
3095          * @param array $conds
3096          * @param string $fname
3097          * @param array $insertOptions
3098          * @param array $selectOptions
3099          * @param array $selectJoinConds
3100          */
3101         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
3102                 $fname = __METHOD__,
3103                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
3104         ) {
3105                 $destTable = $this->tableName( $destTable );
3106
3107                 if ( !is_array( $insertOptions ) ) {
3108                         $insertOptions = [ $insertOptions ];
3109                 }
3110
3111                 $insertOptions = $this->makeInsertOptions( $insertOptions );
3112
3113                 $selectSql = $this->selectSQLText(
3114                         $srcTable,
3115                         array_values( $varMap ),
3116                         $conds,
3117                         $fname,
3118                         $selectOptions,
3119                         $selectJoinConds
3120                 );
3121
3122                 $sql = "INSERT $insertOptions" .
3123                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
3124                         $selectSql;
3125
3126                 $this->query( $sql, $fname );
3127         }
3128
3129         /**
3130          * Construct a LIMIT query with optional offset. This is used for query
3131          * pages. The SQL should be adjusted so that only the first $limit rows
3132          * are returned. If $offset is provided as well, then the first $offset
3133          * rows should be discarded, and the next $limit rows should be returned.
3134          * If the result of the query is not ordered, then the rows to be returned
3135          * are theoretically arbitrary.
3136          *
3137          * $sql is expected to be a SELECT, if that makes a difference.
3138          *
3139          * The version provided by default works in MySQL and SQLite. It will very
3140          * likely need to be overridden for most other DBMSes.
3141          *
3142          * @param string $sql SQL query we will append the limit too
3143          * @param int $limit The SQL limit
3144          * @param int|bool $offset The SQL offset (default false)
3145          * @throws DBUnexpectedError
3146          * @return string
3147          */
3148         public function limitResult( $sql, $limit, $offset = false ) {
3149                 if ( !is_numeric( $limit ) ) {
3150                         throw new DBUnexpectedError( $this,
3151                                 "Invalid non-numeric limit passed to limitResult()\n" );
3152                 }
3153
3154                 return "$sql LIMIT "
3155                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
3156                 . "{$limit} ";
3157         }
3158
3159         public function unionSupportsOrderAndLimit() {
3160                 return true; // True for almost every DB supported
3161         }
3162
3163         public function unionQueries( $sqls, $all ) {
3164                 $glue = $all ? ') UNION ALL (' : ') UNION (';
3165
3166                 return '(' . implode( $glue, $sqls ) . ')';
3167         }
3168
3169         public function unionConditionPermutations(
3170                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
3171                 $options = [], $join_conds = []
3172         ) {
3173                 // First, build the Cartesian product of $permute_conds
3174                 $conds = [ [] ];
3175                 foreach ( $permute_conds as $field => $values ) {
3176                         if ( !$values ) {
3177                                 // Skip empty $values
3178                                 continue;
3179                         }
3180                         $values = array_unique( $values ); // For sanity
3181                         $newConds = [];
3182                         foreach ( $conds as $cond ) {
3183                                 foreach ( $values as $value ) {
3184                                         $cond[$field] = $value;
3185                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
3186                                 }
3187                         }
3188                         $conds = $newConds;
3189                 }
3190
3191                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
3192
3193                 // If there's just one condition and no subordering, hand off to
3194                 // selectSQLText directly.
3195                 if ( count( $conds ) === 1 &&
3196                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
3197                 ) {
3198                         return $this->selectSQLText(
3199                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
3200                         );
3201                 }
3202
3203                 // Otherwise, we need to pull out the order and limit to apply after
3204                 // the union. Then build the SQL queries for each set of conditions in
3205                 // $conds. Then union them together (using UNION ALL, because the
3206                 // product *should* already be distinct).
3207                 $orderBy = $this->makeOrderBy( $options );
3208                 $limit = $options['LIMIT'] ?? null;
3209                 $offset = $options['OFFSET'] ?? false;
3210                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
3211                 if ( !$this->unionSupportsOrderAndLimit() ) {
3212                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
3213                 } else {
3214                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
3215                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
3216                         }
3217                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
3218                                 // We need to increase the limit by the offset rather than
3219                                 // using the offset directly, otherwise it'll skip incorrectly
3220                                 // in the subqueries.
3221                                 $options['LIMIT'] = $limit + $offset;
3222                                 unset( $options['OFFSET'] );
3223                         }
3224                 }
3225
3226                 $sqls = [];
3227                 foreach ( $conds as $cond ) {
3228                         $sqls[] = $this->selectSQLText(
3229                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
3230                         );
3231                 }
3232                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
3233                 if ( $limit !== null ) {
3234                         $sql = $this->limitResult( $sql, $limit, $offset );
3235                 }
3236
3237                 return $sql;
3238         }
3239
3240         public function conditional( $cond, $trueVal, $falseVal ) {
3241                 if ( is_array( $cond ) ) {
3242                         $cond = $this->makeList( $cond, self::LIST_AND );
3243                 }
3244
3245                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
3246         }
3247
3248         public function strreplace( $orig, $old, $new ) {
3249                 return "REPLACE({$orig}, {$old}, {$new})";
3250         }
3251
3252         public function getServerUptime() {
3253                 return 0;
3254         }
3255
3256         public function wasDeadlock() {
3257                 return false;
3258         }
3259
3260         public function wasLockTimeout() {
3261                 return false;
3262         }
3263
3264         public function wasConnectionLoss() {
3265                 return $this->wasConnectionError( $this->lastErrno() );
3266         }
3267
3268         public function wasReadOnlyError() {
3269                 return false;
3270         }
3271
3272         public function wasErrorReissuable() {
3273                 return (
3274                         $this->wasDeadlock() ||
3275                         $this->wasLockTimeout() ||
3276                         $this->wasConnectionLoss()
3277                 );
3278         }
3279
3280         /**
3281          * Do not use this method outside of Database/DBError classes
3282          *
3283          * @param int|string $errno
3284          * @return bool Whether the given query error was a connection drop
3285          */
3286         public function wasConnectionError( $errno ) {
3287                 return false;
3288         }
3289
3290         /**
3291          * @return bool Whether it is safe to assume the given error only caused statement rollback
3292          * @note This is for backwards compatibility for callers catching DBError exceptions in
3293          *   order to ignore problems like duplicate key errors or foriegn key violations
3294          * @since 1.31
3295          */
3296         protected function wasKnownStatementRollbackError() {
3297                 return false; // don't know; it could have caused a transaction rollback
3298         }
3299
3300         public function deadlockLoop() {
3301                 $args = func_get_args();
3302                 $function = array_shift( $args );
3303                 $tries = self::DEADLOCK_TRIES;
3304
3305                 $this->begin( __METHOD__ );
3306
3307                 $retVal = null;
3308                 /** @var Exception $e */
3309                 $e = null;
3310                 do {
3311                         try {
3312                                 $retVal = $function( ...$args );
3313                                 break;
3314                         } catch ( DBQueryError $e ) {
3315                                 if ( $this->wasDeadlock() ) {
3316                                         // Retry after a randomized delay
3317                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3318                                 } else {
3319                                         // Throw the error back up
3320                                         throw $e;
3321                                 }
3322                         }
3323                 } while ( --$tries > 0 );
3324
3325                 if ( $tries <= 0 ) {
3326                         // Too many deadlocks; give up
3327                         $this->rollback( __METHOD__ );
3328                         throw $e;
3329                 } else {
3330                         $this->commit( __METHOD__ );
3331
3332                         return $retVal;
3333                 }
3334         }
3335
3336         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3337                 # Real waits are implemented in the subclass.
3338                 return 0;
3339         }
3340
3341         public function getReplicaPos() {
3342                 # Stub
3343                 return false;
3344         }
3345
3346         public function getMasterPos() {
3347                 # Stub
3348                 return false;
3349         }
3350
3351         public function serverIsReadOnly() {
3352                 return false;
3353         }
3354
3355         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
3356                 if ( !$this->trxLevel ) {
3357                         throw new DBUnexpectedError( $this, "No transaction is active." );
3358                 }
3359                 $this->trxEndCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3360         }
3361
3362         final public function onTransactionCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
3363                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3364                         // Start an implicit transaction similar to how query() does
3365                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3366                         $this->trxAutomatic = true;
3367                 }
3368
3369                 $this->trxIdleCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3370                 if ( !$this->trxLevel ) {
3371                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
3372                 }
3373         }
3374
3375         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
3376                 $this->onTransactionCommitOrIdle( $callback, $fname );
3377         }
3378
3379         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
3380                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3381                         // Start an implicit transaction similar to how query() does
3382                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3383                         $this->trxAutomatic = true;
3384                 }
3385
3386                 if ( $this->trxLevel ) {
3387                         $this->trxPreCommitCallbacks[] = [ $callback, $fname, $this->currentAtomicSectionId() ];
3388                 } else {
3389                         // No transaction is active nor will start implicitly, so make one for this callback
3390                         $this->startAtomic( __METHOD__, self::ATOMIC_CANCELABLE );
3391                         try {
3392                                 $callback( $this );
3393                                 $this->endAtomic( __METHOD__ );
3394                         } catch ( Exception $e ) {
3395                                 $this->cancelAtomic( __METHOD__ );
3396                                 throw $e;
3397                         }
3398                 }
3399         }
3400
3401         /**
3402          * @return AtomicSectionIdentifier|null ID of the topmost atomic section level
3403          */
3404         private function currentAtomicSectionId() {
3405                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3406                         $levelInfo = end( $this->trxAtomicLevels );
3407
3408                         return $levelInfo[1];
3409                 }
3410
3411                 return null;
3412         }
3413
3414         /**
3415          * @param AtomicSectionIdentifier $old
3416          * @param AtomicSectionIdentifier $new
3417          */
3418         private function reassignCallbacksForSection(
3419                 AtomicSectionIdentifier $old, AtomicSectionIdentifier $new
3420         ) {
3421                 foreach ( $this->trxPreCommitCallbacks as $key => $info ) {
3422                         if ( $info[2] === $old ) {
3423                                 $this->trxPreCommitCallbacks[$key][2] = $new;
3424                         }
3425                 }
3426                 foreach ( $this->trxIdleCallbacks as $key => $info ) {
3427                         if ( $info[2] === $old ) {
3428                                 $this->trxIdleCallbacks[$key][2] = $new;
3429                         }
3430                 }
3431                 foreach ( $this->trxEndCallbacks as $key => $info ) {
3432                         if ( $info[2] === $old ) {
3433                                 $this->trxEndCallbacks[$key][2] = $new;
3434                         }
3435                 }
3436         }
3437
3438         /**
3439          * @param AtomicSectionIdentifier[] $sectionIds ID of an actual savepoint
3440          * @throws UnexpectedValueException
3441          */
3442         private function modifyCallbacksForCancel( array $sectionIds ) {
3443                 // Cancel the "on commit" callbacks owned by this savepoint
3444                 $this->trxIdleCallbacks = array_filter(
3445                         $this->trxIdleCallbacks,
3446                         function ( $entry ) use ( $sectionIds ) {
3447                                 return !in_array( $entry[2], $sectionIds, true );
3448                         }
3449                 );
3450                 $this->trxPreCommitCallbacks = array_filter(
3451                         $this->trxPreCommitCallbacks,
3452                         function ( $entry ) use ( $sectionIds ) {
3453                                 return !in_array( $entry[2], $sectionIds, true );
3454                         }
3455                 );
3456                 // Make "on resolution" callbacks owned by this savepoint to perceive a rollback
3457                 foreach ( $this->trxEndCallbacks as $key => $entry ) {
3458                         if ( in_array( $entry[2], $sectionIds, true ) ) {
3459                                 $callback = $entry[0];
3460                                 $this->trxEndCallbacks[$key][0] = function () use ( $callback ) {
3461                                         return $callback( self::TRIGGER_ROLLBACK, $this );
3462                                 };
3463                         }
3464                 }
3465         }
3466
3467         final public function setTransactionListener( $name, callable $callback = null ) {
3468                 if ( $callback ) {
3469                         $this->trxRecurringCallbacks[$name] = $callback;
3470                 } else {
3471                         unset( $this->trxRecurringCallbacks[$name] );
3472                 }
3473         }
3474
3475         /**
3476          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
3477          *
3478          * This method should not be used outside of Database/LoadBalancer
3479          *
3480          * @param bool $suppress
3481          * @since 1.28
3482          */
3483         final public function setTrxEndCallbackSuppression( $suppress ) {
3484                 $this->trxEndCallbacksSuppressed = $suppress;
3485         }
3486
3487         /**
3488          * Actually consume and run any "on transaction idle/resolution" callbacks.
3489          *
3490          * This method should not be used outside of Database/LoadBalancer
3491          *
3492          * @param int $trigger IDatabase::TRIGGER_* constant
3493          * @return int Number of callbacks attempted
3494          * @since 1.20
3495          * @throws Exception
3496          */
3497         public function runOnTransactionIdleCallbacks( $trigger ) {
3498                 if ( $this->trxLevel ) { // sanity
3499                         throw new DBUnexpectedError( $this, __METHOD__ . ': a transaction is still open.' );
3500                 }
3501
3502                 if ( $this->trxEndCallbacksSuppressed ) {
3503                         return 0;
3504                 }
3505
3506                 $count = 0;
3507                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
3508                 /** @var Exception $e */
3509                 $e = null; // first exception
3510                 do { // callbacks may add callbacks :)
3511                         $callbacks = array_merge(
3512                                 $this->trxIdleCallbacks,
3513                                 $this->trxEndCallbacks // include "transaction resolution" callbacks
3514                         );
3515                         $this->trxIdleCallbacks = []; // consumed (and recursion guard)
3516                         $this->trxEndCallbacks = []; // consumed (recursion guard)
3517                         foreach ( $callbacks as $callback ) {
3518                                 ++$count;
3519                                 list( $phpCallback ) = $callback;
3520                                 $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
3521                                 try {
3522                                         call_user_func( $phpCallback, $trigger, $this );
3523                                 } catch ( Exception $ex ) {
3524                                         call_user_func( $this->errorLogger, $ex );
3525                                         $e = $e ?: $ex;
3526                                         // Some callbacks may use startAtomic/endAtomic, so make sure
3527                                         // their transactions are ended so other callbacks don't fail
3528                                         if ( $this->trxLevel() ) {
3529                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
3530                                         }
3531                                 } finally {
3532                                         if ( $autoTrx ) {
3533                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
3534                                         } else {
3535                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
3536                                         }
3537                                 }
3538                         }
3539                 } while ( count( $this->trxIdleCallbacks ) );
3540
3541                 if ( $e instanceof Exception ) {
3542                         throw $e; // re-throw any first exception
3543                 }
3544
3545                 return $count;
3546         }
3547
3548         /**
3549          * Actually consume and run any "on transaction pre-commit" callbacks.
3550          *
3551          * This method should not be used outside of Database/LoadBalancer
3552          *
3553          * @since 1.22
3554          * @return int Number of callbacks attempted
3555          * @throws Exception
3556          */
3557         public function runOnTransactionPreCommitCallbacks() {
3558                 $count = 0;
3559
3560                 $e = null; // first exception
3561                 do { // callbacks may add callbacks :)
3562                         $callbacks = $this->trxPreCommitCallbacks;
3563                         $this->trxPreCommitCallbacks = []; // consumed (and recursion guard)
3564                         foreach ( $callbacks as $callback ) {
3565                                 try {
3566                                         ++$count;
3567                                         list( $phpCallback ) = $callback;
3568                                         $phpCallback( $this );
3569                                 } catch ( Exception $ex ) {
3570                                         ( $this->errorLogger )( $ex );
3571                                         $e = $e ?: $ex;
3572                                 }
3573                         }
3574                 } while ( count( $this->trxPreCommitCallbacks ) );
3575
3576                 if ( $e instanceof Exception ) {
3577                         throw $e; // re-throw any first exception
3578                 }
3579
3580                 return $count;
3581         }
3582
3583         /**
3584          * Actually run any "transaction listener" callbacks.
3585          *
3586          * This method should not be used outside of Database/LoadBalancer
3587          *
3588          * @param int $trigger IDatabase::TRIGGER_* constant
3589          * @throws Exception
3590          * @since 1.20
3591          */
3592         public function runTransactionListenerCallbacks( $trigger ) {
3593                 if ( $this->trxEndCallbacksSuppressed ) {
3594                         return;
3595                 }
3596
3597                 /** @var Exception $e */
3598                 $e = null; // first exception
3599
3600                 foreach ( $this->trxRecurringCallbacks as $phpCallback ) {
3601                         try {
3602                                 $phpCallback( $trigger, $this );
3603                         } catch ( Exception $ex ) {
3604                                 ( $this->errorLogger )( $ex );
3605                                 $e = $e ?: $ex;
3606                         }
3607                 }
3608
3609                 if ( $e instanceof Exception ) {
3610                         throw $e; // re-throw any first exception
3611                 }
3612         }
3613
3614         /**
3615          * Create a savepoint
3616          *
3617          * This is used internally to implement atomic sections. It should not be
3618          * used otherwise.
3619          *
3620          * @since 1.31
3621          * @param string $identifier Identifier for the savepoint
3622          * @param string $fname Calling function name
3623          */
3624         protected function doSavepoint( $identifier, $fname ) {
3625                 $this->query( 'SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3626         }
3627
3628         /**
3629          * Release a savepoint
3630          *
3631          * This is used internally to implement atomic sections. It should not be
3632          * used otherwise.
3633          *
3634          * @since 1.31
3635          * @param string $identifier Identifier for the savepoint
3636          * @param string $fname Calling function name
3637          */
3638         protected function doReleaseSavepoint( $identifier, $fname ) {
3639                 $this->query( 'RELEASE SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3640         }
3641
3642         /**
3643          * Rollback to a savepoint
3644          *
3645          * This is used internally to implement atomic sections. It should not be
3646          * used otherwise.
3647          *
3648          * @since 1.31
3649          * @param string $identifier Identifier for the savepoint
3650          * @param string $fname Calling function name
3651          */
3652         protected function doRollbackToSavepoint( $identifier, $fname ) {
3653                 $this->query( 'ROLLBACK TO SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3654         }
3655
3656         /**
3657          * @param string $fname
3658          * @return string
3659          */
3660         private function nextSavepointId( $fname ) {
3661                 $savepointId = self::$SAVEPOINT_PREFIX . ++$this->trxAtomicCounter;
3662                 if ( strlen( $savepointId ) > 30 ) {
3663                         // 30 == Oracle's identifier length limit (pre 12c)
3664                         // With a 22 character prefix, that puts the highest number at 99999999.
3665                         throw new DBUnexpectedError(
3666                                 $this,
3667                                 'There have been an excessively large number of atomic sections in a transaction'
3668                                 . " started by $this->trxFname (at $fname)"
3669                         );
3670                 }
3671
3672                 return $savepointId;
3673         }
3674
3675         final public function startAtomic(
3676                 $fname = __METHOD__, $cancelable = self::ATOMIC_NOT_CANCELABLE
3677         ) {
3678                 $savepointId = $cancelable === self::ATOMIC_CANCELABLE ? self::$NOT_APPLICABLE : null;
3679
3680                 if ( !$this->trxLevel ) {
3681                         $this->begin( $fname, self::TRANSACTION_INTERNAL ); // sets trxAutomatic
3682                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
3683                         // in all changes being in one transaction to keep requests transactional.
3684                         if ( $this->getFlag( self::DBO_TRX ) ) {
3685                                 // Since writes could happen in between the topmost atomic sections as part
3686                                 // of the transaction, those sections will need savepoints.
3687                                 $savepointId = $this->nextSavepointId( $fname );
3688                                 $this->doSavepoint( $savepointId, $fname );
3689                         } else {
3690                                 $this->trxAutomaticAtomic = true;
3691                         }
3692                 } elseif ( $cancelable === self::ATOMIC_CANCELABLE ) {
3693                         $savepointId = $this->nextSavepointId( $fname );
3694                         $this->doSavepoint( $savepointId, $fname );
3695                 }
3696
3697                 $sectionId = new AtomicSectionIdentifier;
3698                 $this->trxAtomicLevels[] = [ $fname, $sectionId, $savepointId ];
3699                 $this->queryLogger->debug( 'startAtomic: entering level ' .
3700                         ( count( $this->trxAtomicLevels ) - 1 ) . " ($fname)" );
3701
3702                 return $sectionId;
3703         }
3704
3705         final public function endAtomic( $fname = __METHOD__ ) {
3706                 if ( !$this->trxLevel || !$this->trxAtomicLevels ) {
3707                         throw new DBUnexpectedError( $this, "No atomic section is open (got $fname)." );
3708                 }
3709
3710                 // Check if the current section matches $fname
3711                 $pos = count( $this->trxAtomicLevels ) - 1;
3712                 list( $savedFname, $sectionId, $savepointId ) = $this->trxAtomicLevels[$pos];
3713                 $this->queryLogger->debug( "endAtomic: leaving level $pos ($fname)" );
3714
3715                 if ( $savedFname !== $fname ) {
3716                         throw new DBUnexpectedError(
3717                                 $this,
3718                                 "Invalid atomic section ended (got $fname but expected $savedFname)."
3719                         );
3720                 }
3721
3722                 // Remove the last section (no need to re-index the array)
3723                 array_pop( $this->trxAtomicLevels );
3724
3725                 if ( !$this->trxAtomicLevels && $this->trxAutomaticAtomic ) {
3726                         $this->commit( $fname, self::FLUSHING_INTERNAL );
3727                 } elseif ( $savepointId !== null && $savepointId !== self::$NOT_APPLICABLE ) {
3728                         $this->doReleaseSavepoint( $savepointId, $fname );
3729                 }
3730
3731                 // Hoist callback ownership for callbacks in the section that just ended;
3732                 // all callbacks should have an owner that is present in trxAtomicLevels.
3733                 $currentSectionId = $this->currentAtomicSectionId();
3734                 if ( $currentSectionId ) {
3735                         $this->reassignCallbacksForSection( $sectionId, $currentSectionId );
3736                 }
3737         }
3738
3739         final public function cancelAtomic(
3740                 $fname = __METHOD__, AtomicSectionIdentifier $sectionId = null
3741         ) {
3742                 if ( !$this->trxLevel || !$this->trxAtomicLevels ) {
3743                         throw new DBUnexpectedError( $this, "No atomic section is open (got $fname)." );
3744                 }
3745
3746                 $excisedFnames = [];
3747                 if ( $sectionId !== null ) {
3748                         // Find the (last) section with the given $sectionId
3749                         $pos = -1;
3750                         foreach ( $this->trxAtomicLevels as $i => list( $asFname, $asId, $spId ) ) {
3751                                 if ( $asId === $sectionId ) {
3752                                         $pos = $i;
3753                                 }
3754                         }
3755                         if ( $pos < 0 ) {
3756                                 throw new DBUnexpectedError( $this, "Atomic section not found (for $fname)" );
3757                         }
3758                         // Remove all descendant sections and re-index the array
3759                         $excisedIds = [];
3760                         $len = count( $this->trxAtomicLevels );
3761                         for ( $i = $pos + 1; $i < $len; ++$i ) {
3762                                 $excisedFnames[] = $this->trxAtomicLevels[$i][0];
3763                                 $excisedIds[] = $this->trxAtomicLevels[$i][1];
3764                         }
3765                         $this->trxAtomicLevels = array_slice( $this->trxAtomicLevels, 0, $pos + 1 );
3766                         $this->modifyCallbacksForCancel( $excisedIds );
3767                 }
3768
3769                 // Check if the current section matches $fname
3770                 $pos = count( $this->trxAtomicLevels ) - 1;
3771                 list( $savedFname, $savedSectionId, $savepointId ) = $this->trxAtomicLevels[$pos];
3772
3773                 if ( $excisedFnames ) {
3774                         $this->queryLogger->debug( "cancelAtomic: canceling level $pos ($savedFname) " .
3775                                 "and descendants " . implode( ', ', $excisedFnames ) );
3776                 } else {
3777                         $this->queryLogger->debug( "cancelAtomic: canceling level $pos ($savedFname)" );
3778                 }
3779
3780                 if ( $savedFname !== $fname ) {
3781                         throw new DBUnexpectedError(
3782                                 $this,
3783                                 "Invalid atomic section ended (got $fname but expected $savedFname)."
3784                         );
3785                 }
3786
3787                 // Remove the last section (no need to re-index the array)
3788                 array_pop( $this->trxAtomicLevels );
3789                 $this->modifyCallbacksForCancel( [ $savedSectionId ] );
3790
3791                 if ( $savepointId !== null ) {
3792                         // Rollback the transaction to the state just before this atomic section
3793                         if ( $savepointId === self::$NOT_APPLICABLE ) {
3794                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
3795                         } else {
3796                                 $this->doRollbackToSavepoint( $savepointId, $fname );
3797                                 $this->trxStatus = self::STATUS_TRX_OK; // no exception; recovered
3798                                 $this->trxStatusIgnoredCause = null;
3799                         }
3800                 } elseif ( $this->trxStatus > self::STATUS_TRX_ERROR ) {
3801                         // Put the transaction into an error state if it's not already in one
3802                         $this->trxStatus = self::STATUS_TRX_ERROR;
3803                         $this->trxStatusCause = new DBUnexpectedError(
3804                                 $this,
3805                                 "Uncancelable atomic section canceled (got $fname)."
3806                         );
3807                 }
3808
3809                 $this->affectedRowCount = 0; // for the sake of consistency
3810         }
3811
3812         final public function doAtomicSection(
3813                 $fname, callable $callback, $cancelable = self::ATOMIC_NOT_CANCELABLE
3814         ) {
3815                 $sectionId = $this->startAtomic( $fname, $cancelable );
3816                 try {
3817                         $res = $callback( $this, $fname );
3818                 } catch ( Exception $e ) {
3819                         $this->cancelAtomic( $fname, $sectionId );
3820
3821                         throw $e;
3822                 }
3823                 $this->endAtomic( $fname );
3824
3825                 return $res;
3826         }
3827
3828         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
3829                 static $modes = [ self::TRANSACTION_EXPLICIT, self::TRANSACTION_INTERNAL ];
3830                 if ( !in_array( $mode, $modes, true ) ) {
3831                         throw new DBUnexpectedError( $this, "$fname: invalid mode parameter '$mode'." );
3832                 }
3833
3834                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
3835                 if ( $this->trxLevel ) {
3836                         if ( $this->trxAtomicLevels ) {
3837                                 $levels = $this->flatAtomicSectionList();
3838                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
3839                                 throw new DBUnexpectedError( $this, $msg );
3840                         } elseif ( !$this->trxAutomatic ) {
3841                                 $msg = "$fname: Explicit transaction already active (from {$this->trxFname}).";
3842                                 throw new DBUnexpectedError( $this, $msg );
3843                         } else {
3844                                 $msg = "$fname: Implicit transaction already active (from {$this->trxFname}).";
3845                                 throw new DBUnexpectedError( $this, $msg );
3846                         }
3847                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
3848                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
3849                         throw new DBUnexpectedError( $this, $msg );
3850                 }
3851
3852                 // Avoid fatals if close() was called
3853                 $this->assertOpen();
3854
3855                 $this->doBegin( $fname );
3856                 $this->trxStatus = self::STATUS_TRX_OK;
3857                 $this->trxStatusIgnoredCause = null;
3858                 $this->trxAtomicCounter = 0;
3859                 $this->trxTimestamp = microtime( true );
3860                 $this->trxFname = $fname;
3861                 $this->trxDoneWrites = false;
3862                 $this->trxAutomaticAtomic = false;
3863                 $this->trxAtomicLevels = [];
3864                 $this->trxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
3865                 $this->trxWriteDuration = 0.0;
3866                 $this->trxWriteQueryCount = 0;
3867                 $this->trxWriteAffectedRows = 0;
3868                 $this->trxWriteAdjDuration = 0.0;
3869                 $this->trxWriteAdjQueryCount = 0;
3870                 $this->trxWriteCallers = [];
3871                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
3872                 // Get an estimate of the replication lag before any such queries.
3873                 $this->trxReplicaLag = null; // clear cached value first
3874                 $this->trxReplicaLag = $this->getApproximateLagStatus()['lag'];
3875                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
3876                 // caller will think its OK to muck around with the transaction just because startAtomic()
3877                 // has not yet completed (e.g. setting trxAtomicLevels).
3878                 $this->trxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
3879         }
3880
3881         /**
3882          * Issues the BEGIN command to the database server.
3883          *
3884          * @see Database::begin()
3885          * @param string $fname
3886          */
3887         protected function doBegin( $fname ) {
3888                 $this->query( 'BEGIN', $fname );
3889                 $this->trxLevel = 1;
3890         }
3891
3892         final public function commit( $fname = __METHOD__, $flush = self::FLUSHING_ONE ) {
3893                 static $modes = [ self::FLUSHING_ONE, self::FLUSHING_ALL_PEERS, self::FLUSHING_INTERNAL ];
3894                 if ( !in_array( $flush, $modes, true ) ) {
3895                         throw new DBUnexpectedError( $this, "$fname: invalid flush parameter '$flush'." );
3896                 }
3897
3898                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3899                         // There are still atomic sections open; this cannot be ignored
3900                         $levels = $this->flatAtomicSectionList();
3901                         throw new DBUnexpectedError(
3902                                 $this,
3903                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3904                         );
3905                 }
3906
3907                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3908                         if ( !$this->trxLevel ) {
3909                                 return; // nothing to do
3910                         } elseif ( !$this->trxAutomatic ) {
3911                                 throw new DBUnexpectedError(
3912                                         $this,
3913                                         "$fname: Flushing an explicit transaction, getting out of sync."
3914                                 );
3915                         }
3916                 } else {
3917                         if ( !$this->trxLevel ) {
3918                                 $this->queryLogger->error(
3919                                         "$fname: No transaction to commit, something got out of sync." );
3920                                 return; // nothing to do
3921                         } elseif ( $this->trxAutomatic ) {
3922                                 throw new DBUnexpectedError(
3923                                         $this,
3924                                         "$fname: Expected mass commit of all peer transactions (DBO_TRX set)."
3925                                 );
3926                         }
3927                 }
3928
3929                 // Avoid fatals if close() was called
3930                 $this->assertOpen();
3931
3932                 $this->runOnTransactionPreCommitCallbacks();
3933
3934                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3935                 $this->doCommit( $fname );
3936                 $this->trxStatus = self::STATUS_TRX_NONE;
3937
3938                 if ( $this->trxDoneWrites ) {
3939                         $this->lastWriteTime = microtime( true );
3940                         $this->trxProfiler->transactionWritingOut(
3941                                 $this->server,
3942                                 $this->getDomainID(),
3943                                 $this->trxShortId,
3944                                 $writeTime,
3945                                 $this->trxWriteAffectedRows
3946                         );
3947                 }
3948
3949                 // With FLUSHING_ALL_PEERS, callbacks will be explicitly run later
3950                 if ( $flush !== self::FLUSHING_ALL_PEERS ) {
3951                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3952                         $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3953                 }
3954         }
3955
3956         /**
3957          * Issues the COMMIT command to the database server.
3958          *
3959          * @see Database::commit()
3960          * @param string $fname
3961          */
3962         protected function doCommit( $fname ) {
3963                 if ( $this->trxLevel ) {
3964                         $this->query( 'COMMIT', $fname );
3965                         $this->trxLevel = 0;
3966                 }
3967         }
3968
3969         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3970                 $trxActive = $this->trxLevel;
3971
3972                 if ( $flush !== self::FLUSHING_INTERNAL && $flush !== self::FLUSHING_ALL_PEERS ) {
3973                         if ( $this->getFlag( self::DBO_TRX ) ) {
3974                                 throw new DBUnexpectedError(
3975                                         $this,
3976                                         "$fname: Expected mass rollback of all peer transactions (DBO_TRX set)."
3977                                 );
3978                         }
3979                 }
3980
3981                 if ( $trxActive ) {
3982                         // Avoid fatals if close() was called
3983                         $this->assertOpen();
3984
3985                         $this->doRollback( $fname );
3986                         $this->trxStatus = self::STATUS_TRX_NONE;
3987                         $this->trxAtomicLevels = [];
3988                         // Estimate the RTT via a query now that trxStatus is OK
3989                         $writeTime = $this->pingAndCalculateLastTrxApplyTime();
3990
3991                         if ( $this->trxDoneWrites ) {
3992                                 $this->trxProfiler->transactionWritingOut(
3993                                         $this->server,
3994                                         $this->getDomainID(),
3995                                         $this->trxShortId,
3996                                         $writeTime,
3997                                         $this->trxWriteAffectedRows
3998                                 );
3999                         }
4000                 }
4001
4002                 // Clear any commit-dependant callbacks. They might even be present
4003                 // only due to transaction rounds, with no SQL transaction being active
4004                 $this->trxIdleCallbacks = [];
4005                 $this->trxPreCommitCallbacks = [];
4006
4007                 // With FLUSHING_ALL_PEERS, callbacks will be explicitly run later
4008                 if ( $trxActive && $flush !== self::FLUSHING_ALL_PEERS ) {
4009                         try {
4010                                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
4011                         } catch ( Exception $e ) {
4012                                 // already logged; finish and let LoadBalancer move on during mass-rollback
4013                         }
4014                         try {
4015                                 $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
4016                         } catch ( Exception $e ) {
4017                                 // already logged; let LoadBalancer move on during mass-rollback
4018                         }
4019
4020                         $this->affectedRowCount = 0; // for the sake of consistency
4021                 }
4022         }
4023
4024         /**
4025          * Issues the ROLLBACK command to the database server.
4026          *
4027          * @see Database::rollback()
4028          * @param string $fname
4029          */
4030         protected function doRollback( $fname ) {
4031                 if ( $this->trxLevel ) {
4032                         # Disconnects cause rollback anyway, so ignore those errors
4033                         $ignoreErrors = true;
4034                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
4035                         $this->trxLevel = 0;
4036                 }
4037         }
4038
4039         public function flushSnapshot( $fname = __METHOD__ ) {
4040                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
4041                         // This only flushes transactions to clear snapshots, not to write data
4042                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
4043                         throw new DBUnexpectedError(
4044                                 $this,
4045                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
4046                         );
4047                 }
4048
4049                 $this->commit( $fname, self::FLUSHING_INTERNAL );
4050         }
4051
4052         public function explicitTrxActive() {
4053                 return $this->trxLevel && ( $this->trxAtomicLevels || !$this->trxAutomatic );
4054         }
4055
4056         public function duplicateTableStructure(
4057                 $oldName, $newName, $temporary = false, $fname = __METHOD__
4058         ) {
4059                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4060         }
4061
4062         public function listTables( $prefix = null, $fname = __METHOD__ ) {
4063                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4064         }
4065
4066         public function listViews( $prefix = null, $fname = __METHOD__ ) {
4067                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
4068         }
4069
4070         public function timestamp( $ts = 0 ) {
4071                 $t = new ConvertibleTimestamp( $ts );
4072                 // Let errors bubble up to avoid putting garbage in the DB
4073                 return $t->getTimestamp( TS_MW );
4074         }
4075
4076         public function timestampOrNull( $ts = null ) {
4077                 if ( is_null( $ts ) ) {
4078                         return null;
4079                 } else {
4080                         return $this->timestamp( $ts );
4081                 }
4082         }
4083
4084         public function affectedRows() {
4085                 return ( $this->affectedRowCount === null )
4086                         ? $this->fetchAffectedRowCount() // default to driver value
4087                         : $this->affectedRowCount;
4088         }
4089
4090         /**
4091          * @return int Number of retrieved rows according to the driver
4092          */
4093         abstract protected function fetchAffectedRowCount();
4094
4095         /**
4096          * Take the result from a query, and wrap it in a ResultWrapper if
4097          * necessary. Boolean values are passed through as is, to indicate success
4098          * of write queries or failure.
4099          *
4100          * Once upon a time, Database::query() returned a bare MySQL result
4101          * resource, and it was necessary to call this function to convert it to
4102          * a wrapper. Nowadays, raw database objects are never exposed to external
4103          * callers, so this is unnecessary in external code.
4104          *
4105          * @param bool|ResultWrapper|resource $result
4106          * @return bool|ResultWrapper
4107          */
4108         protected function resultObject( $result ) {
4109                 if ( !$result ) {
4110                         return false;
4111                 } elseif ( $result instanceof ResultWrapper ) {
4112                         return $result;
4113                 } elseif ( $result === true ) {
4114                         // Successful write query
4115                         return $result;
4116                 } else {
4117                         return new ResultWrapper( $this, $result );
4118                 }
4119         }
4120
4121         public function ping( &$rtt = null ) {
4122                 // Avoid hitting the server if it was hit recently
4123                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
4124                         if ( !func_num_args() || $this->rttEstimate > 0 ) {
4125                                 $rtt = $this->rttEstimate;
4126                                 return true; // don't care about $rtt
4127                         }
4128                 }
4129
4130                 // This will reconnect if possible or return false if not
4131                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
4132                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
4133                 $this->restoreFlags( self::RESTORE_PRIOR );
4134
4135                 if ( $ok ) {
4136                         $rtt = $this->rttEstimate;
4137                 }
4138
4139                 return $ok;
4140         }
4141
4142         /**
4143          * Close any existing (dead) database connection and open a new connection
4144          *
4145          * @param string $fname
4146          * @return bool True if new connection is opened successfully, false if error
4147          */
4148         protected function replaceLostConnection( $fname ) {
4149                 $this->closeConnection();
4150                 $this->opened = false;
4151                 $this->conn = false;
4152                 try {
4153                         $this->open(
4154                                 $this->server,
4155                                 $this->user,
4156                                 $this->password,
4157                                 $this->getDBname(),
4158                                 $this->dbSchema(),
4159                                 $this->tablePrefix()
4160                         );
4161                         $this->lastPing = microtime( true );
4162                         $ok = true;
4163
4164                         $this->connLogger->warning(
4165                                 $fname . ': lost connection to {dbserver}; reconnected',
4166                                 [
4167                                         'dbserver' => $this->getServer(),
4168                                         'trace' => ( new RuntimeException() )->getTraceAsString()
4169                                 ]
4170                         );
4171                 } catch ( DBConnectionError $e ) {
4172                         $ok = false;
4173
4174                         $this->connLogger->error(
4175                                 $fname . ': lost connection to {dbserver} permanently',
4176                                 [ 'dbserver' => $this->getServer() ]
4177                         );
4178                 }
4179
4180                 $this->handleSessionLoss();
4181
4182                 return $ok;
4183         }
4184
4185         public function getSessionLagStatus() {
4186                 return $this->getRecordedTransactionLagStatus() ?: $this->getApproximateLagStatus();
4187         }
4188
4189         /**
4190          * Get the replica DB lag when the current transaction started
4191          *
4192          * This is useful when transactions might use snapshot isolation
4193          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
4194          * is this lag plus transaction duration. If they don't, it is still
4195          * safe to be pessimistic. This returns null if there is no transaction.
4196          *
4197          * This returns null if the lag status for this transaction was not yet recorded.
4198          *
4199          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
4200          * @since 1.27
4201          */
4202         final protected function getRecordedTransactionLagStatus() {
4203                 return ( $this->trxLevel && $this->trxReplicaLag !== null )
4204                         ? [ 'lag' => $this->trxReplicaLag, 'since' => $this->trxTimestamp() ]
4205                         : null;
4206         }
4207
4208         /**
4209          * Get a replica DB lag estimate for this server
4210          *
4211          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
4212          * @since 1.27
4213          */
4214         protected function getApproximateLagStatus() {
4215                 return [
4216                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
4217                         'since' => microtime( true )
4218                 ];
4219         }
4220
4221         /**
4222          * Merge the result of getSessionLagStatus() for several DBs
4223          * using the most pessimistic values to estimate the lag of
4224          * any data derived from them in combination
4225          *
4226          * This is information is useful for caching modules
4227          *
4228          * @see WANObjectCache::set()
4229          * @see WANObjectCache::getWithSetCallback()
4230          *
4231          * @param IDatabase $db1
4232          * @param IDatabase|null $db2 [optional]
4233          * @return array Map of values:
4234          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
4235          *   - since: oldest UNIX timestamp of any of the DB lag estimates
4236          *   - pending: whether any of the DBs have uncommitted changes
4237          * @throws DBError
4238          * @since 1.27
4239          */
4240         public static function getCacheSetOptions( IDatabase $db1, IDatabase $db2 = null ) {
4241                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
4242                 foreach ( func_get_args() as $db ) {
4243                         /** @var IDatabase $db */
4244                         $status = $db->getSessionLagStatus();
4245                         if ( $status['lag'] === false ) {
4246                                 $res['lag'] = false;
4247                         } elseif ( $res['lag'] !== false ) {
4248                                 $res['lag'] = max( $res['lag'], $status['lag'] );
4249                         }
4250                         $res['since'] = min( $res['since'], $status['since'] );
4251                         $res['pending'] = $res['pending'] ?: $db->writesPending();
4252                 }
4253
4254                 return $res;
4255         }
4256
4257         public function getLag() {
4258                 return 0;
4259         }
4260
4261         public function maxListLen() {
4262                 return 0;
4263         }
4264
4265         public function encodeBlob( $b ) {
4266                 return $b;
4267         }
4268
4269         public function decodeBlob( $b ) {
4270                 if ( $b instanceof Blob ) {
4271                         $b = $b->fetch();
4272                 }
4273                 return $b;
4274         }
4275
4276         public function setSessionOptions( array $options ) {
4277         }
4278
4279         public function sourceFile(
4280                 $filename,
4281                 callable $lineCallback = null,
4282                 callable $resultCallback = null,
4283                 $fname = false,
4284                 callable $inputCallback = null
4285         ) {
4286                 Wikimedia\suppressWarnings();
4287                 $fp = fopen( $filename, 'r' );
4288                 Wikimedia\restoreWarnings();
4289
4290                 if ( $fp === false ) {
4291                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
4292                 }
4293
4294                 if ( !$fname ) {
4295                         $fname = __METHOD__ . "( $filename )";
4296                 }
4297
4298                 try {
4299                         $error = $this->sourceStream(
4300                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
4301                 } catch ( Exception $e ) {
4302                         fclose( $fp );
4303                         throw $e;
4304                 }
4305
4306                 fclose( $fp );
4307
4308                 return $error;
4309         }
4310
4311         public function setSchemaVars( $vars ) {
4312                 $this->schemaVars = $vars;
4313         }
4314
4315         public function sourceStream(
4316                 $fp,
4317                 callable $lineCallback = null,
4318                 callable $resultCallback = null,
4319                 $fname = __METHOD__,
4320                 callable $inputCallback = null
4321         ) {
4322                 $delimiterReset = new ScopedCallback(
4323                         function ( $delimiter ) {
4324                                 $this->delimiter = $delimiter;
4325                         },
4326                         [ $this->delimiter ]
4327                 );
4328                 $cmd = '';
4329
4330                 while ( !feof( $fp ) ) {
4331                         if ( $lineCallback ) {
4332                                 call_user_func( $lineCallback );
4333                         }
4334
4335                         $line = trim( fgets( $fp ) );
4336
4337                         if ( $line == '' ) {
4338                                 continue;
4339                         }
4340
4341                         if ( $line[0] == '-' && $line[1] == '-' ) {
4342                                 continue;
4343                         }
4344
4345                         if ( $cmd != '' ) {
4346                                 $cmd .= ' ';
4347                         }
4348
4349                         $done = $this->streamStatementEnd( $cmd, $line );
4350
4351                         $cmd .= "$line\n";
4352
4353                         if ( $done || feof( $fp ) ) {
4354                                 $cmd = $this->replaceVars( $cmd );
4355
4356                                 if ( $inputCallback ) {
4357                                         $callbackResult = $inputCallback( $cmd );
4358
4359                                         if ( is_string( $callbackResult ) || !$callbackResult ) {
4360                                                 $cmd = $callbackResult;
4361                                         }
4362                                 }
4363
4364                                 if ( $cmd ) {
4365                                         $res = $this->query( $cmd, $fname );
4366
4367                                         if ( $resultCallback ) {
4368                                                 $resultCallback( $res, $this );
4369                                         }
4370
4371                                         if ( $res === false ) {
4372                                                 $err = $this->lastError();
4373
4374                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
4375                                         }
4376                                 }
4377                                 $cmd = '';
4378                         }
4379                 }
4380
4381                 ScopedCallback::consume( $delimiterReset );
4382                 return true;
4383         }
4384
4385         /**
4386          * Called by sourceStream() to check if we've reached a statement end
4387          *
4388          * @param string &$sql SQL assembled so far
4389          * @param string &$newLine New line about to be added to $sql
4390          * @return bool Whether $newLine contains end of the statement
4391          */
4392         public function streamStatementEnd( &$sql, &$newLine ) {
4393                 if ( $this->delimiter ) {
4394                         $prev = $newLine;
4395                         $newLine = preg_replace(
4396                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
4397                         if ( $newLine != $prev ) {
4398                                 return true;
4399                         }
4400                 }
4401
4402                 return false;
4403         }
4404
4405         /**
4406          * Database independent variable replacement. Replaces a set of variables
4407          * in an SQL statement with their contents as given by $this->getSchemaVars().
4408          *
4409          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
4410          *
4411          * - '{$var}' should be used for text and is passed through the database's
4412          *   addQuotes method.
4413          * - `{$var}` should be used for identifiers (e.g. table and database names).
4414          *   It is passed through the database's addIdentifierQuotes method which
4415          *   can be overridden if the database uses something other than backticks.
4416          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
4417          *   database's tableName method.
4418          * - / *i* / passes the name that follows through the database's indexName method.
4419          * - In all other cases, / *$var* / is left unencoded. Except for table options,
4420          *   its use should be avoided. In 1.24 and older, string encoding was applied.
4421          *
4422          * @param string $ins SQL statement to replace variables in
4423          * @return string The new SQL statement with variables replaced
4424          */
4425         protected function replaceVars( $ins ) {
4426                 $vars = $this->getSchemaVars();
4427                 return preg_replace_callback(
4428                         '!
4429                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
4430                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
4431                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
4432                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
4433                         !x',
4434                         function ( $m ) use ( $vars ) {
4435                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
4436                                 // check for both nonexistent keys *and* the empty string.
4437                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
4438                                         if ( $m[1] === 'i' ) {
4439                                                 return $this->indexName( $m[2] );
4440                                         } else {
4441                                                 return $this->tableName( $m[2] );
4442                                         }
4443                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
4444                                         return $this->addQuotes( $vars[$m[3]] );
4445                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
4446                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
4447                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
4448                                         return $vars[$m[5]];
4449                                 } else {
4450                                         return $m[0];
4451                                 }
4452                         },
4453                         $ins
4454                 );
4455         }
4456
4457         /**
4458          * Get schema variables. If none have been set via setSchemaVars(), then
4459          * use some defaults from the current object.
4460          *
4461          * @return array
4462          */
4463         protected function getSchemaVars() {
4464                 if ( $this->schemaVars ) {
4465                         return $this->schemaVars;
4466                 } else {
4467                         return $this->getDefaultSchemaVars();
4468                 }
4469         }
4470
4471         /**
4472          * Get schema variables to use if none have been set via setSchemaVars().
4473          *
4474          * Override this in derived classes to provide variables for tables.sql
4475          * and SQL patch files.
4476          *
4477          * @return array
4478          */
4479         protected function getDefaultSchemaVars() {
4480                 return [];
4481         }
4482
4483         public function lockIsFree( $lockName, $method ) {
4484                 // RDBMs methods for checking named locks may or may not count this thread itself.
4485                 // In MySQL, IS_FREE_LOCK() returns 0 if the thread already has the lock. This is
4486                 // the behavior choosen by the interface for this method.
4487                 return !isset( $this->namedLocksHeld[$lockName] );
4488         }
4489
4490         public function lock( $lockName, $method, $timeout = 5 ) {
4491                 $this->namedLocksHeld[$lockName] = 1;
4492
4493                 return true;
4494         }
4495
4496         public function unlock( $lockName, $method ) {
4497                 unset( $this->namedLocksHeld[$lockName] );
4498
4499                 return true;
4500         }
4501
4502         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
4503                 if ( $this->writesOrCallbacksPending() ) {
4504                         // This only flushes transactions to clear snapshots, not to write data
4505                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
4506                         throw new DBUnexpectedError(
4507                                 $this,
4508                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
4509                         );
4510                 }
4511
4512                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
4513                         return null;
4514                 }
4515
4516                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
4517                         if ( $this->trxLevel() ) {
4518                                 // There is a good chance an exception was thrown, causing any early return
4519                                 // from the caller. Let any error handler get a chance to issue rollback().
4520                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
4521                                 $this->onTransactionResolution(
4522                                         function () use ( $lockKey, $fname ) {
4523                                                 $this->unlock( $lockKey, $fname );
4524                                         },
4525                                         $fname
4526                                 );
4527                         } else {
4528                                 $this->unlock( $lockKey, $fname );
4529                         }
4530                 } );
4531
4532                 $this->commit( $fname, self::FLUSHING_INTERNAL );
4533
4534                 return $unlocker;
4535         }
4536
4537         public function namedLocksEnqueue() {
4538                 return false;
4539         }
4540
4541         public function tableLocksHaveTransactionScope() {
4542                 return true;
4543         }
4544
4545         final public function lockTables( array $read, array $write, $method ) {
4546                 if ( $this->writesOrCallbacksPending() ) {
4547                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
4548                 }
4549
4550                 if ( $this->tableLocksHaveTransactionScope() ) {
4551                         $this->startAtomic( $method );
4552                 }
4553
4554                 return $this->doLockTables( $read, $write, $method );
4555         }
4556
4557         /**
4558          * Helper function for lockTables() that handles the actual table locking
4559          *
4560          * @param array $read Array of tables to lock for read access
4561          * @param array $write Array of tables to lock for write access
4562          * @param string $method Name of caller
4563          * @return true
4564          */
4565         protected function doLockTables( array $read, array $write, $method ) {
4566                 return true;
4567         }
4568
4569         final public function unlockTables( $method ) {
4570                 if ( $this->tableLocksHaveTransactionScope() ) {
4571                         $this->endAtomic( $method );
4572
4573                         return true; // locks released on COMMIT/ROLLBACK
4574                 }
4575
4576                 return $this->doUnlockTables( $method );
4577         }
4578
4579         /**
4580          * Helper function for unlockTables() that handles the actual table unlocking
4581          *
4582          * @param string $method Name of caller
4583          * @return true
4584          */
4585         protected function doUnlockTables( $method ) {
4586                 return true;
4587         }
4588
4589         /**
4590          * Delete a table
4591          * @param string $tableName
4592          * @param string $fName
4593          * @return bool|ResultWrapper
4594          * @since 1.18
4595          */
4596         public function dropTable( $tableName, $fName = __METHOD__ ) {
4597                 if ( !$this->tableExists( $tableName, $fName ) ) {
4598                         return false;
4599                 }
4600                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
4601
4602                 return $this->query( $sql, $fName );
4603         }
4604
4605         public function getInfinity() {
4606                 return 'infinity';
4607         }
4608
4609         public function encodeExpiry( $expiry ) {
4610                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4611                         ? $this->getInfinity()
4612                         : $this->timestamp( $expiry );
4613         }
4614
4615         public function decodeExpiry( $expiry, $format = TS_MW ) {
4616                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
4617                         return 'infinity';
4618                 }
4619
4620                 return ConvertibleTimestamp::convert( $format, $expiry );
4621         }
4622
4623         public function setBigSelects( $value = true ) {
4624                 // no-op
4625         }
4626
4627         public function isReadOnly() {
4628                 return ( $this->getReadOnlyReason() !== false );
4629         }
4630
4631         /**
4632          * @return string|bool Reason this DB is read-only or false if it is not
4633          */
4634         protected function getReadOnlyReason() {
4635                 $reason = $this->getLBInfo( 'readOnlyReason' );
4636
4637                 return is_string( $reason ) ? $reason : false;
4638         }
4639
4640         public function setTableAliases( array $aliases ) {
4641                 $this->tableAliases = $aliases;
4642         }
4643
4644         public function setIndexAliases( array $aliases ) {
4645                 $this->indexAliases = $aliases;
4646         }
4647
4648         /**
4649          * Get the underlying binding connection handle
4650          *
4651          * Makes sure the connection resource is set (disconnects and ping() failure can unset it).
4652          * This catches broken callers than catch and ignore disconnection exceptions.
4653          * Unlike checking isOpen(), this is safe to call inside of open().
4654          *
4655          * @return mixed
4656          * @throws DBUnexpectedError
4657          * @since 1.26
4658          */
4659         protected function getBindingHandle() {
4660                 if ( !$this->conn ) {
4661                         throw new DBUnexpectedError(
4662                                 $this,
4663                                 'DB connection was already closed or the connection dropped.'
4664                         );
4665                 }
4666
4667                 return $this->conn;
4668         }
4669
4670         /**
4671          * @since 1.19
4672          * @return string
4673          */
4674         public function __toString() {
4675                 return (string)$this->conn;
4676         }
4677
4678         /**
4679          * Make sure that copies do not share the same client binding handle
4680          * @throws DBConnectionError
4681          */
4682         public function __clone() {
4683                 $this->connLogger->warning(
4684                         "Cloning " . static::class . " is not recommended; forking connection:\n" .
4685                         ( new RuntimeException() )->getTraceAsString()
4686                 );
4687
4688                 if ( $this->isOpen() ) {
4689                         // Open a new connection resource without messing with the old one
4690                         $this->opened = false;
4691                         $this->conn = false;
4692                         $this->trxEndCallbacks = []; // don't copy
4693                         $this->handleSessionLoss(); // no trx or locks anymore
4694                         $this->open(
4695                                 $this->server,
4696                                 $this->user,
4697                                 $this->password,
4698                                 $this->getDBname(),
4699                                 $this->dbSchema(),
4700                                 $this->tablePrefix()
4701                         );
4702                         $this->lastPing = microtime( true );
4703                 }
4704         }
4705
4706         /**
4707          * Called by serialize. Throw an exception when DB connection is serialized.
4708          * This causes problems on some database engines because the connection is
4709          * not restored on unserialize.
4710          */
4711         public function __sleep() {
4712                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
4713                         'the connection is not restored on wakeup.' );
4714         }
4715
4716         /**
4717          * Run a few simple sanity checks and close dangling connections
4718          */
4719         public function __destruct() {
4720                 if ( $this->trxLevel && $this->trxDoneWrites ) {
4721                         trigger_error( "Uncommitted DB writes (transaction from {$this->trxFname})." );
4722                 }
4723
4724                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
4725                 if ( $danglingWriters ) {
4726                         $fnames = implode( ', ', $danglingWriters );
4727                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
4728                 }
4729
4730                 if ( $this->conn ) {
4731                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
4732                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
4733                         Wikimedia\suppressWarnings();
4734                         $this->closeConnection();
4735                         Wikimedia\restoreWarnings();
4736                         $this->conn = false;
4737                         $this->opened = false;
4738                 }
4739         }
4740 }
4741
4742 /**
4743  * @deprecated since 1.28
4744  */
4745 class_alias( Database::class, 'DatabaseBase' );
4746
4747 /**
4748  * @deprecated since 1.29
4749  */
4750 class_alias( Database::class, 'Database' );