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