includes/libs/rdbms/database/Database.php

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