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