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