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