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