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 InvalidArgumentException;
  37 use Exception;
  38 use RuntimeException;
  39
  40 /**
  41  * Relational database abstraction object
  42  *
  43  * @ingroup Database
  44  * @since 1.28
  45  */
  46 abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAwareInterface {
  47         /** Number of times to re-try an operation in case of deadlock */
  48         const DEADLOCK_TRIES = 4;
  49         /** Minimum time to wait before retry, in microseconds */
  50         const DEADLOCK_DELAY_MIN = 500000;
  51         /** Maximum time to wait before retry */
  52         const DEADLOCK_DELAY_MAX = 1500000;
  53
  54         /** How long before it is worth doing a dummy query to test the connection */
  55         const PING_TTL = 1.0;
  56         const PING_QUERY = 'SELECT 1 AS ping';
  57
  58         const TINY_WRITE_SEC = 0.010;
  59         const SLOW_WRITE_SEC = 0.500;
  60         const SMALL_WRITE_ROWS = 100;
  61
  62         /** @var string Whether lock granularity is on the level of the entire database */
  63         const ATTR_DB_LEVEL_LOCKING = 'db-level-locking';
  64
  65         /** @var string SQL query */
  66         protected $lastQuery = '';
  67         /** @var float|bool UNIX timestamp of last write query */
  68         protected $lastWriteTime = false;
  69         /** @var string|bool */
  70         protected $phpError = false;
  71         /** @var string */
  72         protected $server;
  73         /** @var string */
  74         protected $user;
  75         /** @var string */
  76         protected $password;
  77         /** @var string */
  78         protected $dbName;
  79         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  80         protected $tableAliases = [];
  81         /** @var bool Whether this PHP instance is for a CLI script */
  82         protected $cliMode;
  83         /** @var string Agent name for query profiling */
  84         protected $agent;
  85
  86         /** @var BagOStuff APC cache */
  87         protected $srvCache;
  88         /** @var LoggerInterface */
  89         protected $connLogger;
  90         /** @var LoggerInterface */
  91         protected $queryLogger;
  92         /** @var callback Error logging callback */
  93         protected $errorLogger;
  94
  95         /** @var resource|null Database connection */
  96         protected $conn = null;
  97         /** @var bool */
  98         protected $opened = false;
  99
 100         /** @var array[] List of (callable, method name) */
 101         protected $trxIdleCallbacks = [];
 102         /** @var array[] List of (callable, method name) */
 103         protected $trxPreCommitCallbacks = [];
 104         /** @var array[] List of (callable, method name) */
 105         protected $trxEndCallbacks = [];
 106         /** @var callable[] Map of (name => callable) */
 107         protected $trxRecurringCallbacks = [];
 108         /** @var bool Whether to suppress triggering of transaction end callbacks */
 109         protected $trxEndCallbacksSuppressed = false;
 110
 111         /** @var string */
 112         protected $tablePrefix = '';
 113         /** @var string */
 114         protected $schema = '';
 115         /** @var int */
 116         protected $flags;
 117         /** @var array */
 118         protected $lbInfo = [];
 119         /** @var array|bool */
 120         protected $schemaVars = false;
 121         /** @var array */
 122         protected $sessionVars = [];
 123         /** @var array|null */
 124         protected $preparedArgs;
 125         /** @var string|bool|null Stashed value of html_errors INI setting */
 126         protected $htmlErrors;
 127         /** @var string */
 128         protected $delimiter = ';';
 129         /** @var DatabaseDomain */
 130         protected $currentDomain;
 131         /** @var integer|null Rows affected by the last query to query() or its CRUD wrappers */
 132         protected $affectedRowCount;
 133
 134         /**
 135          * Either 1 if a transaction is active or 0 otherwise.
 136          * The other Trx fields may not be meaningfull if this is 0.
 137          *
 138          * @var int
 139          */
 140         protected $trxLevel = 0;
 141         /**
 142          * Either a short hexidecimal string if a transaction is active or ""
 143          *
 144          * @var string
 145          * @see Database::trxLevel
 146          */
 147         protected $trxShortId = '';
 148         /**
 149          * The UNIX time that the transaction started. Callers can assume that if
 150          * snapshot isolation is used, then the data is *at least* up to date to that
 151          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 152          *
 153          * @var float|null
 154          * @see Database::trxLevel
 155          */
 156         private $trxTimestamp = null;
 157         /** @var float Lag estimate at the time of BEGIN */
 158         private $trxReplicaLag = null;
 159         /**
 160          * Remembers the function name given for starting the most recent transaction via begin().
 161          * Used to provide additional context for error reporting.
 162          *
 163          * @var string
 164          * @see Database::trxLevel
 165          */
 166         private $trxFname = null;
 167         /**
 168          * Record if possible write queries were done in the last transaction started
 169          *
 170          * @var bool
 171          * @see Database::trxLevel
 172          */
 173         private $trxDoneWrites = false;
 174         /**
 175          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 176          *
 177          * @var bool
 178          * @see Database::trxLevel
 179          */
 180         private $trxAutomatic = false;
 181         /**
 182          * Array of levels of atomicity within transactions
 183          *
 184          * @var array
 185          */
 186         private $trxAtomicLevels = [];
 187         /**
 188          * Record if the current transaction was started implicitly by Database::startAtomic
 189          *
 190          * @var bool
 191          */
 192         private $trxAutomaticAtomic = false;
 193         /**
 194          * Track the write query callers of the current transaction
 195          *
 196          * @var string[]
 197          */
 198         private $trxWriteCallers = [];
 199         /**
 200          * @var float Seconds spent in write queries for the current transaction
 201          */
 202         private $trxWriteDuration = 0.0;
 203         /**
 204          * @var int Number of write queries for the current transaction
 205          */
 206         private $trxWriteQueryCount = 0;
 207         /**
 208          * @var int Number of rows affected by write queries for the current transaction
 209          */
 210         private $trxWriteAffectedRows = 0;
 211         /**
 212          * @var float Like trxWriteQueryCount but excludes lock-bound, easy to replicate, queries
 213          */
 214         private $trxWriteAdjDuration = 0.0;
 215         /**
 216          * @var int Number of write queries counted in trxWriteAdjDuration
 217          */
 218         private $trxWriteAdjQueryCount = 0;
 219         /**
 220          * @var float RTT time estimate
 221          */
 222         private $rttEstimate = 0.0;
 223
 224         /** @var array Map of (name => 1) for locks obtained via lock() */
 225         private $namedLocksHeld = [];
 226         /** @var array Map of (table name => 1) for TEMPORARY tables */
 227         protected $sessionTempTables = [];
 228
 229         /** @var IDatabase|null Lazy handle to the master DB this server replicates from */
 230         private $lazyMasterHandle;
 231
 232         /** @var float UNIX timestamp */
 233         protected $lastPing = 0.0;
 234
 235         /** @var int[] Prior flags member variable values */
 236         private $priorFlags = [];
 237
 238         /** @var object|string Class name or object With profileIn/profileOut methods */
 239         protected $profiler;
 240         /** @var TransactionProfiler */
 241         protected $trxProfiler;
 242
 243         /** @var int */
 244         protected $nonNativeInsertSelectBatchSize = 10000;
 245
 246         /**
 247          * Constructor and database handle and attempt to connect to the DB server
 248          *
 249          * IDatabase classes should not be constructed directly in external
 250          * code. Database::factory() should be used instead.
 251          *
 252          * @param array $params Parameters passed from Database::factory()
 253          */
 254         function __construct( array $params ) {
 255                 $server = $params['host'];
 256                 $user = $params['user'];
 257                 $password = $params['password'];
 258                 $dbName = $params['dbname'];
 259
 260                 $this->schema = $params['schema'];
 261                 $this->tablePrefix = $params['tablePrefix'];
 262
 263                 $this->cliMode = $params['cliMode'];
 264                 // Agent name is added to SQL queries in a comment, so make sure it can't break out
 265                 $this->agent = str_replace( '/', '-', $params['agent'] );
 266
 267                 $this->flags = $params['flags'];
 268                 if ( $this->flags & self::DBO_DEFAULT ) {
 269                         if ( $this->cliMode ) {
 270                                 $this->flags &= ~self::DBO_TRX;
 271                         } else {
 272                                 $this->flags |= self::DBO_TRX;
 273                         }
 274                 }
 275
 276                 $this->sessionVars = $params['variables'];
 277
 278                 $this->srvCache = isset( $params['srvCache'] )
 279                         ? $params['srvCache']
 280                         : new HashBagOStuff();
 281
 282                 $this->profiler = $params['profiler'];
 283                 $this->trxProfiler = $params['trxProfiler'];
 284                 $this->connLogger = $params['connLogger'];
 285                 $this->queryLogger = $params['queryLogger'];
 286                 $this->errorLogger = $params['errorLogger'];
 287
 288                 if ( isset( $params['nonNativeInsertSelectBatchSize'] ) ) {
 289                         $this->nonNativeInsertSelectBatchSize = $params['nonNativeInsertSelectBatchSize'];
 290                 }
 291
 292                 // Set initial dummy domain until open() sets the final DB/prefix
 293                 $this->currentDomain = DatabaseDomain::newUnspecified();
 294
 295                 if ( $user ) {
 296                         $this->open( $server, $user, $password, $dbName );
 297                 } elseif ( $this->requiresDatabaseUser() ) {
 298                         throw new InvalidArgumentException( "No database user provided." );
 299                 }
 300
 301                 // Set the domain object after open() sets the relevant fields
 302                 if ( $this->dbName != '' ) {
 303                         // Domains with server scope but a table prefix are not used by IDatabase classes
 304                         $this->currentDomain = new DatabaseDomain( $this->dbName, null, $this->tablePrefix );
 305                 }
 306         }
 307
 308         /**
 309          * Construct a Database subclass instance given a database type and parameters
 310          *
 311          * This also connects to the database immediately upon object construction
 312          *
 313          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 314          * @param array $p Parameter map with keys:
 315          *   - host : The hostname of the DB server
 316          *   - user : The name of the database user the client operates under
 317          *   - password : The password for the database user
 318          *   - dbname : The name of the database to use where queries do not specify one.
 319          *      The database must exist or an error might be thrown. Setting this to the empty string
 320          *      will avoid any such errors and make the handle have no implicit database scope. This is
 321          *      useful for queries like SHOW STATUS, CREATE DATABASE, or DROP DATABASE. Note that a
 322          *      "database" in Postgres is rougly equivalent to an entire MySQL server. This the domain
 323          *      in which user names and such are defined, e.g. users are database-specific in Postgres.
 324          *   - schema : The database schema to use (if supported). A "schema" in Postgres is roughly
 325          *      equivalent to a "database" in MySQL. Note that MySQL and SQLite do not use schemas.
 326          *   - tablePrefix : Optional table prefix that is implicitly added on to all table names
 327          *      recognized in queries. This can be used in place of schemas for handle site farms.
 328          *   - flags : Optional bitfield of DBO_* constants that define connection, protocol,
 329          *      buffering, and transaction behavior. It is STRONGLY adviced to leave the DBO_DEFAULT
 330          *      flag in place UNLESS this this database simply acts as a key/value store.
 331          *   - driver: Optional name of a specific DB client driver. For MySQL, there is only the
 332          *      'mysqli' driver; the old one 'mysql' has been removed.
 333          *   - variables: Optional map of session variables to set after connecting. This can be
 334          *      used to adjust lock timeouts or encoding modes and the like.
 335          *   - connLogger: Optional PSR-3 logger interface instance.
 336          *   - queryLogger: Optional PSR-3 logger interface instance.
 337          *   - profiler: Optional class name or object with profileIn()/profileOut() methods.
 338          *      These will be called in query(), using a simplified version of the SQL that also
 339          *      includes the agent as a SQL comment.
 340          *   - trxProfiler: Optional TransactionProfiler instance.
 341          *   - errorLogger: Optional callback that takes an Exception and logs it.
 342          *   - cliMode: Whether to consider the execution context that of a CLI script.
 343          *   - agent: Optional name used to identify the end-user in query profiling/logging.
 344          *   - srvCache: Optional BagOStuff instance to an APC-style cache.
 345          *   - nonNativeInsertSelectBatchSize: Optional batch size for non-native INSERT SELECT emulation.
 346          * @return Database|null If the database driver or extension cannot be found
 347          * @throws InvalidArgumentException If the database driver or extension cannot be found
 348          * @since 1.18
 349          */
 350         final public static function factory( $dbType, $p = [] ) {
 351                 $class = self::getClass( $dbType, isset( $p['driver'] ) ? $p['driver'] : null );
 352
 353                 if ( class_exists( $class ) && is_subclass_of( $class, IDatabase::class ) ) {
 354                         // Resolve some defaults for b/c
 355                         $p['host'] = isset( $p['host'] ) ? $p['host'] : false;
 356                         $p['user'] = isset( $p['user'] ) ? $p['user'] : false;
 357                         $p['password'] = isset( $p['password'] ) ? $p['password'] : false;
 358                         $p['dbname'] = isset( $p['dbname'] ) ? $p['dbname'] : false;
 359                         $p['flags'] = isset( $p['flags'] ) ? $p['flags'] : 0;
 360                         $p['variables'] = isset( $p['variables'] ) ? $p['variables'] : [];
 361                         $p['tablePrefix'] = isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : '';
 362                         $p['schema'] = isset( $p['schema'] ) ? $p['schema'] : '';
 363                         $p['cliMode'] = isset( $p['cliMode'] )
 364                                 ? $p['cliMode']
 365                                 : ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 366                         $p['agent'] = isset( $p['agent'] ) ? $p['agent'] : '';
 367                         if ( !isset( $p['connLogger'] ) ) {
 368                                 $p['connLogger'] = new NullLogger();
 369                         }
 370                         if ( !isset( $p['queryLogger'] ) ) {
 371                                 $p['queryLogger'] = new NullLogger();
 372                         }
 373                         $p['profiler'] = isset( $p['profiler'] ) ? $p['profiler'] : null;
 374                         if ( !isset( $p['trxProfiler'] ) ) {
 375                                 $p['trxProfiler'] = new TransactionProfiler();
 376                         }
 377                         if ( !isset( $p['errorLogger'] ) ) {
 378                                 $p['errorLogger'] = function ( Exception $e ) {
 379                                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 380                                 };
 381                         }
 382
 383                         $conn = new $class( $p );
 384                 } else {
 385                         $conn = null;
 386                 }
 387
 388                 return $conn;
 389         }
 390
 391         /**
 392          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 393          * @param string|null $driver Optional name of a specific DB client driver
 394          * @return array Map of (Database::ATTRIBUTE_* constant => value) for all such constants
 395          * @throws InvalidArgumentException
 396          * @since 1.31
 397          */
 398         final public static function attributesFromType( $dbType, $driver = null ) {
 399                 static $defaults = [ self::ATTR_DB_LEVEL_LOCKING => false ];
 400
 401                 $class = self::getClass( $dbType, $driver );
 402
 403                 return call_user_func( [ $class, 'getAttributes' ] ) + $defaults;
 404         }
 405
 406         /**
 407          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 408          * @param string|null $driver Optional name of a specific DB client driver
 409          * @return string Database subclass name to use
 410          * @throws InvalidArgumentException
 411          */
 412         private static function getClass( $dbType, $driver = null ) {
 413                 // For database types with built-in support, the below maps type to IDatabase
 414                 // implementations. For types with multipe driver implementations (PHP extensions),
 415                 // an array can be used, keyed by extension name. In case of an array, the
 416                 // optional 'driver' parameter can be used to force a specific driver. Otherwise,
 417                 // we auto-detect the first available driver. For types without built-in support,
 418                 // an class named "Database<Type>" us used, eg. DatabaseFoo for type 'foo'.
 419                 static $builtinTypes = [
 420                         'mssql' => DatabaseMssql::class,
 421                         'mysql' => [ 'mysqli' => DatabaseMysqli::class ],
 422                         'sqlite' => DatabaseSqlite::class,
 423                         'postgres' => DatabasePostgres::class,
 424                 ];
 425
 426                 $dbType = strtolower( $dbType );
 427                 $class = false;
 428
 429                 if ( isset( $builtinTypes[$dbType] ) ) {
 430                         $possibleDrivers = $builtinTypes[$dbType];
 431                         if ( is_string( $possibleDrivers ) ) {
 432                                 $class = $possibleDrivers;
 433                         } else {
 434                                 if ( (string)$driver !== '' ) {
 435                                         if ( !isset( $possibleDrivers[$driver] ) ) {
 436                                                 throw new InvalidArgumentException( __METHOD__ .
 437                                                         " type '$dbType' does not support driver '{$driver}'" );
 438                                         } else {
 439                                                 $class = $possibleDrivers[$driver];
 440                                         }
 441                                 } else {
 442                                         foreach ( $possibleDrivers as $posDriver => $possibleClass ) {
 443                                                 if ( extension_loaded( $posDriver ) ) {
 444                                                         $class = $possibleClass;
 445                                                         break;
 446                                                 }
 447                                         }
 448                                 }
 449                         }
 450                 } else {
 451                         $class = 'Database' . ucfirst( $dbType );
 452                 }
 453
 454                 if ( $class === false ) {
 455                         throw new InvalidArgumentException( __METHOD__ .
 456                                 " no viable database extension found for type '$dbType'" );
 457                 }
 458
 459                 return $class;
 460         }
 461
 462         /**
 463          * @return array Map of (Database::ATTRIBUTE_* constant => value
 464          * @since 1.31
 465          */
 466         protected static function getAttributes() {
 467                 return [];
 468         }
 469
 470         /**
 471          * Set the PSR-3 logger interface to use for query logging. (The logger
 472          * interfaces for connection logging and error logging can be set with the
 473          * constructor.)
 474          *
 475          * @param LoggerInterface $logger
 476          */
 477         public function setLogger( LoggerInterface $logger ) {
 478                 $this->queryLogger = $logger;
 479         }
 480
 481         public function getServerInfo() {
 482                 return $this->getServerVersion();
 483         }
 484
 485         public function bufferResults( $buffer = null ) {
 486                 $res = !$this->getFlag( self::DBO_NOBUFFER );
 487                 if ( $buffer !== null ) {
 488                         $buffer
 489                                 ? $this->clearFlag( self::DBO_NOBUFFER )
 490                                 : $this->setFlag( self::DBO_NOBUFFER );
 491                 }
 492
 493                 return $res;
 494         }
 495
 496         /**
 497          * Turns on (false) or off (true) the automatic generation and sending
 498          * of a "we're sorry, but there has been a database error" page on
 499          * database errors. Default is on (false). When turned off, the
 500          * code should use lastErrno() and lastError() to handle the
 501          * situation as appropriate.
 502          *
 503          * Do not use this function outside of the Database classes.
 504          *
 505          * @param null|bool $ignoreErrors
 506          * @return bool The previous value of the flag.
 507          */
 508         protected function ignoreErrors( $ignoreErrors = null ) {
 509                 $res = $this->getFlag( self::DBO_IGNORE );
 510                 if ( $ignoreErrors !== null ) {
 511                         // setFlag()/clearFlag() do not allow DBO_IGNORE changes for sanity
 512                         if ( $ignoreErrors ) {
 513                                 $this->flags |= self::DBO_IGNORE;
 514                         } else {
 515                                 $this->flags &= ~self::DBO_IGNORE;
 516                         }
 517                 }
 518
 519                 return $res;
 520         }
 521
 522         public function trxLevel() {
 523                 return $this->trxLevel;
 524         }
 525
 526         public function trxTimestamp() {
 527                 return $this->trxLevel ? $this->trxTimestamp : null;
 528         }
 529
 530         public function tablePrefix( $prefix = null ) {
 531                 $old = $this->tablePrefix;
 532                 if ( $prefix !== null ) {
 533                         $this->tablePrefix = $prefix;
 534                         $this->currentDomain = ( $this->dbName != '' )
 535                                 ? new DatabaseDomain( $this->dbName, null, $this->tablePrefix )
 536                                 : DatabaseDomain::newUnspecified();
 537                 }
 538
 539                 return $old;
 540         }
 541
 542         public function dbSchema( $schema = null ) {
 543                 $old = $this->schema;
 544                 if ( $schema !== null ) {
 545                         $this->schema = $schema;
 546                 }
 547
 548                 return $old;
 549         }
 550
 551         public function getLBInfo( $name = null ) {
 552                 if ( is_null( $name ) ) {
 553                         return $this->lbInfo;
 554                 } else {
 555                         if ( array_key_exists( $name, $this->lbInfo ) ) {
 556                                 return $this->lbInfo[$name];
 557                         } else {
 558                                 return null;
 559                         }
 560                 }
 561         }
 562
 563         public function setLBInfo( $name, $value = null ) {
 564                 if ( is_null( $value ) ) {
 565                         $this->lbInfo = $name;
 566                 } else {
 567                         $this->lbInfo[$name] = $value;
 568                 }
 569         }
 570
 571         public function setLazyMasterHandle( IDatabase $conn ) {
 572                 $this->lazyMasterHandle = $conn;
 573         }
 574
 575         /**
 576          * @return IDatabase|null
 577          * @see setLazyMasterHandle()
 578          * @since 1.27
 579          */
 580         protected function getLazyMasterHandle() {
 581                 return $this->lazyMasterHandle;
 582         }
 583
 584         public function implicitGroupby() {
 585                 return true;
 586         }
 587
 588         public function implicitOrderby() {
 589                 return true;
 590         }
 591
 592         public function lastQuery() {
 593                 return $this->lastQuery;
 594         }
 595
 596         public function doneWrites() {
 597                 return (bool)$this->lastWriteTime;
 598         }
 599
 600         public function lastDoneWrites() {
 601                 return $this->lastWriteTime ?: false;
 602         }
 603
 604         public function writesPending() {
 605                 return $this->trxLevel && $this->trxDoneWrites;
 606         }
 607
 608         public function writesOrCallbacksPending() {
 609                 return $this->trxLevel && (
 610                         $this->trxDoneWrites || $this->trxIdleCallbacks || $this->trxPreCommitCallbacks
 611                 );
 612         }
 613
 614         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 615                 if ( !$this->trxLevel ) {
 616                         return false;
 617                 } elseif ( !$this->trxDoneWrites ) {
 618                         return 0.0;
 619                 }
 620
 621                 switch ( $type ) {
 622                         case self::ESTIMATE_DB_APPLY:
 623                                 $this->ping( $rtt );
 624                                 $rttAdjTotal = $this->trxWriteAdjQueryCount * $rtt;
 625                                 $applyTime = max( $this->trxWriteAdjDuration - $rttAdjTotal, 0 );
 626                                 // For omitted queries, make them count as something at least
 627                                 $omitted = $this->trxWriteQueryCount - $this->trxWriteAdjQueryCount;
 628                                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 629
 630                                 return $applyTime;
 631                         default: // everything
 632                                 return $this->trxWriteDuration;
 633                 }
 634         }
 635
 636         public function pendingWriteCallers() {
 637                 return $this->trxLevel ? $this->trxWriteCallers : [];
 638         }
 639
 640         public function pendingWriteRowsAffected() {
 641                 return $this->trxWriteAffectedRows;
 642         }
 643
 644         /**
 645          * Get the list of method names that have pending write queries or callbacks
 646          * for this transaction
 647          *
 648          * @return array
 649          */
 650         protected function pendingWriteAndCallbackCallers() {
 651                 if ( !$this->trxLevel ) {
 652                         return [];
 653                 }
 654
 655                 $fnames = $this->trxWriteCallers;
 656                 foreach ( [
 657                         $this->trxIdleCallbacks,
 658                         $this->trxPreCommitCallbacks,
 659                         $this->trxEndCallbacks
 660                 ] as $callbacks ) {
 661                         foreach ( $callbacks as $callback ) {
 662                                 $fnames[] = $callback[1];
 663                         }
 664                 }
 665
 666                 return $fnames;
 667         }
 668
 669         public function isOpen() {
 670                 return $this->opened;
 671         }
 672
 673         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 674                 if ( ( $flag & self::DBO_IGNORE ) ) {
 675                         throw new \UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 676                 }
 677
 678                 if ( $remember === self::REMEMBER_PRIOR ) {
 679                         array_push( $this->priorFlags, $this->flags );
 680                 }
 681                 $this->flags |= $flag;
 682         }
 683
 684         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 685                 if ( ( $flag & self::DBO_IGNORE ) ) {
 686                         throw new \UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 687                 }
 688
 689                 if ( $remember === self::REMEMBER_PRIOR ) {
 690                         array_push( $this->priorFlags, $this->flags );
 691                 }
 692                 $this->flags &= ~$flag;
 693         }
 694
 695         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 696                 if ( !$this->priorFlags ) {
 697                         return;
 698                 }
 699
 700                 if ( $state === self::RESTORE_INITIAL ) {
 701                         $this->flags = reset( $this->priorFlags );
 702                         $this->priorFlags = [];
 703                 } else {
 704                         $this->flags = array_pop( $this->priorFlags );
 705                 }
 706         }
 707
 708         public function getFlag( $flag ) {
 709                 return !!( $this->flags & $flag );
 710         }
 711
 712         /**
 713          * @param string $name Class field name
 714          * @return mixed
 715          * @deprecated Since 1.28
 716          */
 717         public function getProperty( $name ) {
 718                 return $this->$name;
 719         }
 720
 721         public function getDomainID() {
 722                 return $this->currentDomain->getId();
 723         }
 724
 725         final public function getWikiID() {
 726                 return $this->getDomainID();
 727         }
 728
 729         /**
 730          * Get information about an index into an object
 731          * @param string $table Table name
 732          * @param string $index Index name
 733          * @param string $fname Calling function name
 734          * @return mixed Database-specific index description class or false if the index does not exist
 735          */
 736         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 737
 738         /**
 739          * Wrapper for addslashes()
 740          *
 741          * @param string $s String to be slashed.
 742          * @return string Slashed string.
 743          */
 744         abstract function strencode( $s );
 745
 746         /**
 747          * Set a custom error handler for logging errors during database connection
 748          */
 749         protected function installErrorHandler() {
 750                 $this->phpError = false;
 751                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 752                 set_error_handler( [ $this, 'connectionErrorLogger' ] );
 753         }
 754
 755         /**
 756          * Restore the previous error handler and return the last PHP error for this DB
 757          *
 758          * @return bool|string
 759          */
 760         protected function restoreErrorHandler() {
 761                 restore_error_handler();
 762                 if ( $this->htmlErrors !== false ) {
 763                         ini_set( 'html_errors', $this->htmlErrors );
 764                 }
 765
 766                 return $this->getLastPHPError();
 767         }
 768
 769         /**
 770          * @return string|bool Last PHP error for this DB (typically connection errors)
 771          */
 772         protected function getLastPHPError() {
 773                 if ( $this->phpError ) {
 774                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->phpError );
 775                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 776
 777                         return $error;
 778                 }
 779
 780                 return false;
 781         }
 782
 783         /**
 784          * Error handler for logging errors during database connection
 785          * This method should not be used outside of Database classes
 786          *
 787          * @param int $errno
 788          * @param string $errstr
 789          */
 790         public function connectionErrorLogger( $errno, $errstr ) {
 791                 $this->phpError = $errstr;
 792         }
 793
 794         /**
 795          * Create a log context to pass to PSR-3 logger functions.
 796          *
 797          * @param array $extras Additional data to add to context
 798          * @return array
 799          */
 800         protected function getLogContext( array $extras = [] ) {
 801                 return array_merge(
 802                         [
 803                                 'db_server' => $this->server,
 804                                 'db_name' => $this->dbName,
 805                                 'db_user' => $this->user,
 806                         ],
 807                         $extras
 808                 );
 809         }
 810
 811         public function close() {
 812                 if ( $this->conn ) {
 813                         if ( $this->trxLevel() ) {
 814                                 $this->commit( __METHOD__, self::FLUSHING_INTERNAL );
 815                         }
 816
 817                         $closed = $this->closeConnection();
 818                         $this->conn = false;
 819                 } elseif (
 820                         $this->trxIdleCallbacks ||
 821                         $this->trxPreCommitCallbacks ||
 822                         $this->trxEndCallbacks
 823                 ) { // sanity
 824                         throw new RuntimeException( "Transaction callbacks still pending." );
 825                 } else {
 826                         $closed = true;
 827                 }
 828                 $this->opened = false;
 829
 830                 return $closed;
 831         }
 832
 833         /**
 834          * Make sure isOpen() returns true as a sanity check
 835          *
 836          * @throws DBUnexpectedError
 837          */
 838         protected function assertOpen() {
 839                 if ( !$this->isOpen() ) {
 840                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
 841                 }
 842         }
 843
 844         /**
 845          * Closes underlying database connection
 846          * @since 1.20
 847          * @return bool Whether connection was closed successfully
 848          */
 849         abstract protected function closeConnection();
 850
 851         public function reportConnectionError( $error = 'Unknown error' ) {
 852                 $myError = $this->lastError();
 853                 if ( $myError ) {
 854                         $error = $myError;
 855                 }
 856
 857                 # New method
 858                 throw new DBConnectionError( $this, $error );
 859         }
 860
 861         /**
 862          * The DBMS-dependent part of query()
 863          *
 864          * @param string $sql SQL query.
 865          * @return ResultWrapper|bool Result object to feed to fetchObject,
 866          *   fetchRow, ...; or false on failure
 867          */
 868         abstract protected function doQuery( $sql );
 869
 870         /**
 871          * Determine whether a query writes to the DB.
 872          * Should return true if unsure.
 873          *
 874          * @param string $sql
 875          * @return bool
 876          */
 877         protected function isWriteQuery( $sql ) {
 878                 return !preg_match(
 879                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 880         }
 881
 882         /**
 883          * @param string $sql
 884          * @return string|null
 885          */
 886         protected function getQueryVerb( $sql ) {
 887                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
 888         }
 889
 890         /**
 891          * Determine whether a SQL statement is sensitive to isolation level.
 892          * A SQL statement is considered transactable if its result could vary
 893          * depending on the transaction isolation level. Operational commands
 894          * such as 'SET' and 'SHOW' are not considered to be transactable.
 895          *
 896          * @param string $sql
 897          * @return bool
 898          */
 899         protected function isTransactableQuery( $sql ) {
 900                 return !in_array(
 901                         $this->getQueryVerb( $sql ),
 902                         [ 'BEGIN', 'COMMIT', 'ROLLBACK', 'SHOW', 'SET', 'CREATE', 'ALTER' ],
 903                         true
 904                 );
 905         }
 906
 907         /**
 908          * @param string $sql A SQL query
 909          * @return bool Whether $sql is SQL for TEMPORARY table operation
 910          */
 911         protected function registerTempTableOperation( $sql ) {
 912                 if ( preg_match(
 913                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 914                         $sql,
 915                         $matches
 916                 ) ) {
 917                         $this->sessionTempTables[$matches[1]] = 1;
 918
 919                         return true;
 920                 } elseif ( preg_match(
 921                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 922                         $sql,
 923                         $matches
 924                 ) ) {
 925                         $isTemp = isset( $this->sessionTempTables[$matches[1]] );
 926                         unset( $this->sessionTempTables[$matches[1]] );
 927
 928                         return $isTemp;
 929                 } elseif ( preg_match(
 930                         '/^TRUNCATE\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 931                         $sql,
 932                         $matches
 933                 ) ) {
 934                         return isset( $this->sessionTempTables[$matches[1]] );
 935                 } elseif ( preg_match(
 936                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
 937                         $sql,
 938                         $matches
 939                 ) ) {
 940                         return isset( $this->sessionTempTables[$matches[1]] );
 941                 }
 942
 943                 return false;
 944         }
 945
 946         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 947                 $priorWritesPending = $this->writesOrCallbacksPending();
 948                 $this->lastQuery = $sql;
 949
 950                 $isWrite = $this->isWriteQuery( $sql );
 951                 if ( $isWrite ) {
 952                         $isNonTempWrite = !$this->registerTempTableOperation( $sql );
 953                 } else {
 954                         $isNonTempWrite = false;
 955                 }
 956
 957                 if ( $isWrite ) {
 958                         if ( $this->getLBInfo( 'replica' ) === true ) {
 959                                 throw new DBError(
 960                                         $this,
 961                                         'Write operations are not allowed on replica database connections.'
 962                                 );
 963                         }
 964                         # In theory, non-persistent writes are allowed in read-only mode, but due to things
 965                         # like https://bugs.mysql.com/bug.php?id=33669 that might not work anyway...
 966                         $reason = $this->getReadOnlyReason();
 967                         if ( $reason !== false ) {
 968                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
 969                         }
 970                         # Set a flag indicating that writes have been done
 971                         $this->lastWriteTime = microtime( true );
 972                 }
 973
 974                 # Add trace comment to the begin of the sql string, right after the operator.
 975                 # Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598)
 976                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
 977
 978                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
 979                 if ( !$this->trxLevel && $this->getFlag( self::DBO_TRX )
 980                         && $this->isTransactableQuery( $sql )
 981                 ) {
 982                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
 983                         $this->trxAutomatic = true;
 984                 }
 985
 986                 # Keep track of whether the transaction has write queries pending
 987                 if ( $this->trxLevel && !$this->trxDoneWrites && $isWrite ) {
 988                         $this->trxDoneWrites = true;
 989                         $this->trxProfiler->transactionWritingIn(
 990                                 $this->server, $this->dbName, $this->trxShortId );
 991                 }
 992
 993                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
 994                         $this->queryLogger->debug( "{$this->dbName} {$commentedSql}" );
 995                 }
 996
 997                 # Avoid fatals if close() was called
 998                 $this->assertOpen();
 999
1000                 # Send the query to the server
1001                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1002
1003                 # Try reconnecting if the connection was lost
1004                 if ( false === $ret && $this->wasErrorReissuable() ) {
1005                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
1006                         # Stash the last error values before anything might clear them
1007                         $lastError = $this->lastError();
1008                         $lastErrno = $this->lastErrno();
1009                         # Update state tracking to reflect transaction loss due to disconnection
1010                         $this->handleSessionLoss();
1011                         if ( $this->reconnect() ) {
1012                                 $msg = __METHOD__ . ': lost connection to {dbserver}; reconnected';
1013                                 $params = [ 'dbserver' => $this->getServer() ];
1014                                 $this->connLogger->warning( $msg, $params );
1015                                 $this->queryLogger->warning( $msg, $params +
1016                                         [ 'trace' => ( new RuntimeException() )->getTraceAsString() ] );
1017
1018                                 if ( !$recoverable ) {
1019                                         # Callers may catch the exception and continue to use the DB
1020                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname );
1021                                 } else {
1022                                         # Should be safe to silently retry the query
1023                                         $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1024                                 }
1025                         } else {
1026                                 $msg = __METHOD__ . ': lost connection to {dbserver} permanently';
1027                                 $this->connLogger->error( $msg, [ 'dbserver' => $this->getServer() ] );
1028                         }
1029                 }
1030
1031                 if ( false === $ret ) {
1032                         # Deadlocks cause the entire transaction to abort, not just the statement.
1033                         # https://dev.mysql.com/doc/refman/5.7/en/innodb-error-handling.html
1034                         # https://www.postgresql.org/docs/9.1/static/explicit-locking.html
1035                         if ( $this->wasDeadlock() ) {
1036                                 if ( $this->explicitTrxActive() || $priorWritesPending ) {
1037                                         $tempIgnore = false; // not recoverable
1038                                 }
1039                                 # Update state tracking to reflect transaction loss
1040                                 $this->handleSessionLoss();
1041                         }
1042
1043                         $this->reportQueryError(
1044                                 $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1045                 }
1046
1047                 $res = $this->resultObject( $ret );
1048
1049                 return $res;
1050         }
1051
1052         /**
1053          * Wrapper for query() that also handles profiling, logging, and affected row count updates
1054          *
1055          * @param string $sql Original SQL query
1056          * @param string $commentedSql SQL query with debugging/trace comment
1057          * @param bool $isWrite Whether the query is a (non-temporary) write operation
1058          * @param string $fname Name of the calling function
1059          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
1060          *     object for a successful read query, or false on failure
1061          */
1062         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
1063                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1064                 # generalizeSQL() will probably cut down the query to reasonable
1065                 # logging size most of the time. The substr is really just a sanity check.
1066                 if ( $isMaster ) {
1067                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1068                 } else {
1069                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1070                 }
1071
1072                 # Include query transaction state
1073                 $queryProf .= $this->trxShortId ? " [TRX#{$this->trxShortId}]" : "";
1074
1075                 $startTime = microtime( true );
1076                 if ( $this->profiler ) {
1077                         call_user_func( [ $this->profiler, 'profileIn' ], $queryProf );
1078                 }
1079                 $this->affectedRowCount = null;
1080                 $ret = $this->doQuery( $commentedSql );
1081                 $this->affectedRowCount = $this->affectedRows();
1082                 if ( $this->profiler ) {
1083                         call_user_func( [ $this->profiler, 'profileOut' ], $queryProf );
1084                 }
1085                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1086
1087                 unset( $queryProfSection ); // profile out (if set)
1088
1089                 if ( $ret !== false ) {
1090                         $this->lastPing = $startTime;
1091                         if ( $isWrite && $this->trxLevel ) {
1092                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1093                                 $this->trxWriteCallers[] = $fname;
1094                         }
1095                 }
1096
1097                 if ( $sql === self::PING_QUERY ) {
1098                         $this->rttEstimate = $queryRuntime;
1099                 }
1100
1101                 $this->trxProfiler->recordQueryCompletion(
1102                         $queryProf, $startTime, $isWrite, $this->affectedRows()
1103                 );
1104                 $this->queryLogger->debug( $sql, [
1105                         'method' => $fname,
1106                         'master' => $isMaster,
1107                         'runtime' => $queryRuntime,
1108                 ] );
1109
1110                 return $ret;
1111         }
1112
1113         /**
1114          * Update the estimated run-time of a query, not counting large row lock times
1115          *
1116          * LoadBalancer can be set to rollback transactions that will create huge replication
1117          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1118          * queries, like inserting a row can take a long time due to row locking. This method
1119          * uses some simple heuristics to discount those cases.
1120          *
1121          * @param string $sql A SQL write query
1122          * @param float $runtime Total runtime, including RTT
1123          * @param int $affected Affected row count
1124          */
1125         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1126                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1127                 $indicativeOfReplicaRuntime = true;
1128                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1129                         $verb = $this->getQueryVerb( $sql );
1130                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1131                         if ( $verb === 'INSERT' ) {
1132                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1133                         } elseif ( $verb === 'REPLACE' ) {
1134                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1135                         }
1136                 }
1137
1138                 $this->trxWriteDuration += $runtime;
1139                 $this->trxWriteQueryCount += 1;
1140                 $this->trxWriteAffectedRows += $affected;
1141                 if ( $indicativeOfReplicaRuntime ) {
1142                         $this->trxWriteAdjDuration += $runtime;
1143                         $this->trxWriteAdjQueryCount += 1;
1144                 }
1145         }
1146
1147         /**
1148          * Determine whether or not it is safe to retry queries after a database
1149          * connection is lost
1150          *
1151          * @param string $sql SQL query
1152          * @param bool $priorWritesPending Whether there is a transaction open with
1153          *     possible write queries or transaction pre-commit/idle callbacks
1154          *     waiting on it to finish.
1155          * @return bool True if it is safe to retry the query, false otherwise
1156          */
1157         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1158                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1159                 # Dropped connections also mean that named locks are automatically released.
1160                 # Only allow error suppression in autocommit mode or when the lost transaction
1161                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1162                 if ( $this->namedLocksHeld ) {
1163                         return false; // possible critical section violation
1164                 } elseif ( $sql === 'COMMIT' ) {
1165                         return !$priorWritesPending; // nothing written anyway? (T127428)
1166                 } elseif ( $sql === 'ROLLBACK' ) {
1167                         return true; // transaction lost...which is also what was requested :)
1168                 } elseif ( $this->explicitTrxActive() ) {
1169                         return false; // don't drop atomocity
1170                 } elseif ( $priorWritesPending ) {
1171                         return false; // prior writes lost from implicit transaction
1172                 }
1173
1174                 return true;
1175         }
1176
1177         /**
1178          * Clean things up after transaction loss due to disconnection
1179          *
1180          * @return null|Exception
1181          */
1182         private function handleSessionLoss() {
1183                 $this->trxLevel = 0;
1184                 $this->trxIdleCallbacks = []; // T67263
1185                 $this->trxPreCommitCallbacks = []; // T67263
1186                 $this->sessionTempTables = [];
1187                 $this->namedLocksHeld = [];
1188                 try {
1189                         // Handle callbacks in trxEndCallbacks
1190                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1191                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1192                         return null;
1193                 } catch ( Exception $e ) {
1194                         // Already logged; move on...
1195                         return $e;
1196                 }
1197         }
1198
1199         /**
1200          * Checks whether the cause of the error is detected to be a timeout.
1201          *
1202          * It returns false by default, and not all engines support detecting this yet.
1203          * If this returns false, it will be treated as a generic query error.
1204          *
1205          * @param string $error Error text
1206          * @param int $errno Error number
1207          * @return bool
1208          */
1209         protected function wasQueryTimeout( $error, $errno ) {
1210                 return false;
1211         }
1212
1213         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1214                 if ( $this->ignoreErrors() || $tempIgnore ) {
1215                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1216                 } else {
1217                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1218                         $this->queryLogger->error(
1219                                 "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1220                                 $this->getLogContext( [
1221                                         'method' => __METHOD__,
1222                                         'errno' => $errno,
1223                                         'error' => $error,
1224                                         'sql1line' => $sql1line,
1225                                         'fname' => $fname,
1226                                 ] )
1227                         );
1228                         $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1229                         $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1230                         if ( $wasQueryTimeout ) {
1231                                 throw new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1232                         } else {
1233                                 throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1234                         }
1235                 }
1236         }
1237
1238         public function freeResult( $res ) {
1239         }
1240
1241         public function selectField(
1242                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1243         ) {
1244                 if ( $var === '*' ) { // sanity
1245                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1246                 }
1247
1248                 if ( !is_array( $options ) ) {
1249                         $options = [ $options ];
1250                 }
1251
1252                 $options['LIMIT'] = 1;
1253
1254                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1255                 if ( $res === false || !$this->numRows( $res ) ) {
1256                         return false;
1257                 }
1258
1259                 $row = $this->fetchRow( $res );
1260
1261                 if ( $row !== false ) {
1262                         return reset( $row );
1263                 } else {
1264                         return false;
1265                 }
1266         }
1267
1268         public function selectFieldValues(
1269                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1270         ) {
1271                 if ( $var === '*' ) { // sanity
1272                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1273                 } elseif ( !is_string( $var ) ) { // sanity
1274                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1275                 }
1276
1277                 if ( !is_array( $options ) ) {
1278                         $options = [ $options ];
1279                 }
1280
1281                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1282                 if ( $res === false ) {
1283                         return false;
1284                 }
1285
1286                 $values = [];
1287                 foreach ( $res as $row ) {
1288                         $values[] = $row->$var;
1289                 }
1290
1291                 return $values;
1292         }
1293
1294         /**
1295          * Returns an optional USE INDEX clause to go after the table, and a
1296          * string to go at the end of the query.
1297          *
1298          * @param array $options Associative array of options to be turned into
1299          *   an SQL query, valid keys are listed in the function.
1300          * @return array
1301          * @see Database::select()
1302          */
1303         protected function makeSelectOptions( $options ) {
1304                 $preLimitTail = $postLimitTail = '';
1305                 $startOpts = '';
1306
1307                 $noKeyOptions = [];
1308
1309                 foreach ( $options as $key => $option ) {
1310                         if ( is_numeric( $key ) ) {
1311                                 $noKeyOptions[$option] = true;
1312                         }
1313                 }
1314
1315                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1316
1317                 $preLimitTail .= $this->makeOrderBy( $options );
1318
1319                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1320                         $postLimitTail .= ' FOR UPDATE';
1321                 }
1322
1323                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1324                         $postLimitTail .= ' LOCK IN SHARE MODE';
1325                 }
1326
1327                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1328                         $startOpts .= 'DISTINCT';
1329                 }
1330
1331                 # Various MySQL extensions
1332                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1333                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1334                 }
1335
1336                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1337                         $startOpts .= ' HIGH_PRIORITY';
1338                 }
1339
1340                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1341                         $startOpts .= ' SQL_BIG_RESULT';
1342                 }
1343
1344                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1345                         $startOpts .= ' SQL_BUFFER_RESULT';
1346                 }
1347
1348                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1349                         $startOpts .= ' SQL_SMALL_RESULT';
1350                 }
1351
1352                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1353                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1354                 }
1355
1356                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1357                         $startOpts .= ' SQL_CACHE';
1358                 }
1359
1360                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1361                         $startOpts .= ' SQL_NO_CACHE';
1362                 }
1363
1364                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1365                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1366                 } else {
1367                         $useIndex = '';
1368                 }
1369                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1370                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1371                 } else {
1372                         $ignoreIndex = '';
1373                 }
1374
1375                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1376         }
1377
1378         /**
1379          * Returns an optional GROUP BY with an optional HAVING
1380          *
1381          * @param array $options Associative array of options
1382          * @return string
1383          * @see Database::select()
1384          * @since 1.21
1385          */
1386         protected function makeGroupByWithHaving( $options ) {
1387                 $sql = '';
1388                 if ( isset( $options['GROUP BY'] ) ) {
1389                         $gb = is_array( $options['GROUP BY'] )
1390                                 ? implode( ',', $options['GROUP BY'] )
1391                                 : $options['GROUP BY'];
1392                         $sql .= ' GROUP BY ' . $gb;
1393                 }
1394                 if ( isset( $options['HAVING'] ) ) {
1395                         $having = is_array( $options['HAVING'] )
1396                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1397                                 : $options['HAVING'];
1398                         $sql .= ' HAVING ' . $having;
1399                 }
1400
1401                 return $sql;
1402         }
1403
1404         /**
1405          * Returns an optional ORDER BY
1406          *
1407          * @param array $options Associative array of options
1408          * @return string
1409          * @see Database::select()
1410          * @since 1.21
1411          */
1412         protected function makeOrderBy( $options ) {
1413                 if ( isset( $options['ORDER BY'] ) ) {
1414                         $ob = is_array( $options['ORDER BY'] )
1415                                 ? implode( ',', $options['ORDER BY'] )
1416                                 : $options['ORDER BY'];
1417
1418                         return ' ORDER BY ' . $ob;
1419                 }
1420
1421                 return '';
1422         }
1423
1424         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1425                 $options = [], $join_conds = [] ) {
1426                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1427
1428                 return $this->query( $sql, $fname );
1429         }
1430
1431         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1432                 $options = [], $join_conds = []
1433         ) {
1434                 if ( is_array( $vars ) ) {
1435                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1436                 }
1437
1438                 $options = (array)$options;
1439                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1440                         ? $options['USE INDEX']
1441                         : [];
1442                 $ignoreIndexes = (
1443                         isset( $options['IGNORE INDEX'] ) &&
1444                         is_array( $options['IGNORE INDEX'] )
1445                 )
1446                         ? $options['IGNORE INDEX']
1447                         : [];
1448
1449                 if ( is_array( $table ) ) {
1450                         $from = ' FROM ' .
1451                                 $this->tableNamesWithIndexClauseOrJOIN(
1452                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1453                 } elseif ( $table != '' ) {
1454                         $from = ' FROM ' .
1455                                 $this->tableNamesWithIndexClauseOrJOIN(
1456                                         [ $table ], $useIndexes, $ignoreIndexes, [] );
1457                 } else {
1458                         $from = '';
1459                 }
1460
1461                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1462                         $this->makeSelectOptions( $options );
1463
1464                 if ( is_array( $conds ) ) {
1465                         $conds = $this->makeList( $conds, self::LIST_AND );
1466                 }
1467
1468                 if ( $conds === null || $conds === false ) {
1469                         $this->queryLogger->warning(
1470                                 __METHOD__
1471                                 . ' called from '
1472                                 . $fname
1473                                 . ' with incorrect parameters: $conds must be a string or an array'
1474                         );
1475                         $conds = '';
1476                 }
1477
1478                 if ( $conds === '' ) {
1479                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex $preLimitTail";
1480                 } elseif ( is_string( $conds ) ) {
1481                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex " .
1482                                 "WHERE $conds $preLimitTail";
1483                 } else {
1484                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1485                 }
1486
1487                 if ( isset( $options['LIMIT'] ) ) {
1488                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1489                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1490                 }
1491                 $sql = "$sql $postLimitTail";
1492
1493                 if ( isset( $options['EXPLAIN'] ) ) {
1494                         $sql = 'EXPLAIN ' . $sql;
1495                 }
1496
1497                 return $sql;
1498         }
1499
1500         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1501                 $options = [], $join_conds = []
1502         ) {
1503                 $options = (array)$options;
1504                 $options['LIMIT'] = 1;
1505                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1506
1507                 if ( $res === false ) {
1508                         return false;
1509                 }
1510
1511                 if ( !$this->numRows( $res ) ) {
1512                         return false;
1513                 }
1514
1515                 $obj = $this->fetchObject( $res );
1516
1517                 return $obj;
1518         }
1519
1520         public function estimateRowCount(
1521                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
1522         ) {
1523                 $rows = 0;
1524                 $res = $this->select( $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options );
1525
1526                 if ( $res ) {
1527                         $row = $this->fetchRow( $res );
1528                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1529                 }
1530
1531                 return $rows;
1532         }
1533
1534         public function selectRowCount(
1535                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1536         ) {
1537                 $rows = 0;
1538                 $sql = $this->selectSQLText( $tables, '1', $conds, $fname, $options, $join_conds );
1539                 // The identifier quotes is primarily for MSSQL.
1540                 $rowCountCol = $this->addIdentifierQuotes( "rowcount" );
1541                 $tableName = $this->addIdentifierQuotes( "tmp_count" );
1542                 $res = $this->query( "SELECT COUNT(*) AS $rowCountCol FROM ($sql) $tableName", $fname );
1543
1544                 if ( $res ) {
1545                         $row = $this->fetchRow( $res );
1546                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1547                 }
1548
1549                 return $rows;
1550         }
1551
1552         /**
1553          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1554          * It's only slightly flawed. Don't use for anything important.
1555          *
1556          * @param string $sql A SQL Query
1557          *
1558          * @return string
1559          */
1560         protected static function generalizeSQL( $sql ) {
1561                 # This does the same as the regexp below would do, but in such a way
1562                 # as to avoid crashing php on some large strings.
1563                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1564
1565                 $sql = str_replace( "\\\\", '', $sql );
1566                 $sql = str_replace( "\\'", '', $sql );
1567                 $sql = str_replace( "\\\"", '', $sql );
1568                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1569                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1570
1571                 # All newlines, tabs, etc replaced by single space
1572                 $sql = preg_replace( '/\s+/', ' ', $sql );
1573
1574                 # All numbers => N,
1575                 # except the ones surrounded by characters, e.g. l10n
1576                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1577                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1578
1579                 return $sql;
1580         }
1581
1582         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1583                 $info = $this->fieldInfo( $table, $field );
1584
1585                 return (bool)$info;
1586         }
1587
1588         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1589                 if ( !$this->tableExists( $table ) ) {
1590                         return null;
1591                 }
1592
1593                 $info = $this->indexInfo( $table, $index, $fname );
1594                 if ( is_null( $info ) ) {
1595                         return null;
1596                 } else {
1597                         return $info !== false;
1598                 }
1599         }
1600
1601         public function tableExists( $table, $fname = __METHOD__ ) {
1602                 $tableRaw = $this->tableName( $table, 'raw' );
1603                 if ( isset( $this->sessionTempTables[$tableRaw] ) ) {
1604                         return true; // already known to exist
1605                 }
1606
1607                 $table = $this->tableName( $table );
1608                 $ignoreErrors = true;
1609                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname, $ignoreErrors );
1610
1611                 return (bool)$res;
1612         }
1613
1614         public function indexUnique( $table, $index ) {
1615                 $indexInfo = $this->indexInfo( $table, $index );
1616
1617                 if ( !$indexInfo ) {
1618                         return null;
1619                 }
1620
1621                 return !$indexInfo[0]->Non_unique;
1622         }
1623
1624         /**
1625          * Helper for Database::insert().
1626          *
1627          * @param array $options
1628          * @return string
1629          */
1630         protected function makeInsertOptions( $options ) {
1631                 return implode( ' ', $options );
1632         }
1633
1634         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1635                 # No rows to insert, easy just return now
1636                 if ( !count( $a ) ) {
1637                         return true;
1638                 }
1639
1640                 $table = $this->tableName( $table );
1641
1642                 if ( !is_array( $options ) ) {
1643                         $options = [ $options ];
1644                 }
1645
1646                 $fh = null;
1647                 if ( isset( $options['fileHandle'] ) ) {
1648                         $fh = $options['fileHandle'];
1649                 }
1650                 $options = $this->makeInsertOptions( $options );
1651
1652                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1653                         $multi = true;
1654                         $keys = array_keys( $a[0] );
1655                 } else {
1656                         $multi = false;
1657                         $keys = array_keys( $a );
1658                 }
1659
1660                 $sql = 'INSERT ' . $options .
1661                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1662
1663                 if ( $multi ) {
1664                         $first = true;
1665                         foreach ( $a as $row ) {
1666                                 if ( $first ) {
1667                                         $first = false;
1668                                 } else {
1669                                         $sql .= ',';
1670                                 }
1671                                 $sql .= '(' . $this->makeList( $row ) . ')';
1672                         }
1673                 } else {
1674                         $sql .= '(' . $this->makeList( $a ) . ')';
1675                 }
1676
1677                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1678                         return false;
1679                 } elseif ( $fh !== null ) {
1680                         return true;
1681                 }
1682
1683                 return (bool)$this->query( $sql, $fname );
1684         }
1685
1686         /**
1687          * Make UPDATE options array for Database::makeUpdateOptions
1688          *
1689          * @param array $options
1690          * @return array
1691          */
1692         protected function makeUpdateOptionsArray( $options ) {
1693                 if ( !is_array( $options ) ) {
1694                         $options = [ $options ];
1695                 }
1696
1697                 $opts = [];
1698
1699                 if ( in_array( 'IGNORE', $options ) ) {
1700                         $opts[] = 'IGNORE';
1701                 }
1702
1703                 return $opts;
1704         }
1705
1706         /**
1707          * Make UPDATE options for the Database::update function
1708          *
1709          * @param array $options The options passed to Database::update
1710          * @return string
1711          */
1712         protected function makeUpdateOptions( $options ) {
1713                 $opts = $this->makeUpdateOptionsArray( $options );
1714
1715                 return implode( ' ', $opts );
1716         }
1717
1718         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1719                 $table = $this->tableName( $table );
1720                 $opts = $this->makeUpdateOptions( $options );
1721                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
1722
1723                 if ( $conds !== [] && $conds !== '*' ) {
1724                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
1725                 }
1726
1727                 return (bool)$this->query( $sql, $fname );
1728         }
1729
1730         public function makeList( $a, $mode = self::LIST_COMMA ) {
1731                 if ( !is_array( $a ) ) {
1732                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1733                 }
1734
1735                 $first = true;
1736                 $list = '';
1737
1738                 foreach ( $a as $field => $value ) {
1739                         if ( !$first ) {
1740                                 if ( $mode == self::LIST_AND ) {
1741                                         $list .= ' AND ';
1742                                 } elseif ( $mode == self::LIST_OR ) {
1743                                         $list .= ' OR ';
1744                                 } else {
1745                                         $list .= ',';
1746                                 }
1747                         } else {
1748                                 $first = false;
1749                         }
1750
1751                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
1752                                 $list .= "($value)";
1753                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
1754                                 $list .= "$value";
1755                         } elseif (
1756                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
1757                         ) {
1758                                 // Remove null from array to be handled separately if found
1759                                 $includeNull = false;
1760                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
1761                                         $includeNull = true;
1762                                         unset( $value[$nullKey] );
1763                                 }
1764                                 if ( count( $value ) == 0 && !$includeNull ) {
1765                                         throw new InvalidArgumentException(
1766                                                 __METHOD__ . ": empty input for field $field" );
1767                                 } elseif ( count( $value ) == 0 ) {
1768                                         // only check if $field is null
1769                                         $list .= "$field IS NULL";
1770                                 } else {
1771                                         // IN clause contains at least one valid element
1772                                         if ( $includeNull ) {
1773                                                 // Group subconditions to ensure correct precedence
1774                                                 $list .= '(';
1775                                         }
1776                                         if ( count( $value ) == 1 ) {
1777                                                 // Special-case single values, as IN isn't terribly efficient
1778                                                 // Don't necessarily assume the single key is 0; we don't
1779                                                 // enforce linear numeric ordering on other arrays here.
1780                                                 $value = array_values( $value )[0];
1781                                                 $list .= $field . " = " . $this->addQuotes( $value );
1782                                         } else {
1783                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1784                                         }
1785                                         // if null present in array, append IS NULL
1786                                         if ( $includeNull ) {
1787                                                 $list .= " OR $field IS NULL)";
1788                                         }
1789                                 }
1790                         } elseif ( $value === null ) {
1791                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
1792                                         $list .= "$field IS ";
1793                                 } elseif ( $mode == self::LIST_SET ) {
1794                                         $list .= "$field = ";
1795                                 }
1796                                 $list .= 'NULL';
1797                         } else {
1798                                 if (
1799                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
1800                                 ) {
1801                                         $list .= "$field = ";
1802                                 }
1803                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
1804                         }
1805                 }
1806
1807                 return $list;
1808         }
1809
1810         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1811                 $conds = [];
1812
1813                 foreach ( $data as $base => $sub ) {
1814                         if ( count( $sub ) ) {
1815                                 $conds[] = $this->makeList(
1816                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
1817                                         self::LIST_AND );
1818                         }
1819                 }
1820
1821                 if ( $conds ) {
1822                         return $this->makeList( $conds, self::LIST_OR );
1823                 } else {
1824                         // Nothing to search for...
1825                         return false;
1826                 }
1827         }
1828
1829         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1830                 return $valuename;
1831         }
1832
1833         public function bitNot( $field ) {
1834                 return "(~$field)";
1835         }
1836
1837         public function bitAnd( $fieldLeft, $fieldRight ) {
1838                 return "($fieldLeft & $fieldRight)";
1839         }
1840
1841         public function bitOr( $fieldLeft, $fieldRight ) {
1842                 return "($fieldLeft | $fieldRight)";
1843         }
1844
1845         public function buildConcat( $stringList ) {
1846                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1847         }
1848
1849         public function buildGroupConcatField(
1850                 $delim, $table, $field, $conds = '', $join_conds = []
1851         ) {
1852                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
1853
1854                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
1855         }
1856
1857         public function buildSubstring( $input, $startPosition, $length = null ) {
1858                 $this->assertBuildSubstringParams( $startPosition, $length );
1859                 $functionBody = "$input FROM $startPosition";
1860                 if ( $length !== null ) {
1861                         $functionBody .= " FOR $length";
1862                 }
1863                 return 'SUBSTRING(' . $functionBody . ')';
1864         }
1865
1866         /**
1867          * Check type and bounds for parameters to self::buildSubstring()
1868          *
1869          * All supported databases have substring functions that behave the same for
1870          * positive $startPosition and non-negative $length, but behaviors differ when
1871          * given 0 or negative $startPosition or negative $length. The simplest
1872          * solution to that is to just forbid those values.
1873          *
1874          * @param int $startPosition
1875          * @param int|null $length
1876          * @since 1.31
1877          */
1878         protected function assertBuildSubstringParams( $startPosition, $length ) {
1879                 if ( !is_int( $startPosition ) || $startPosition <= 0 ) {
1880                         throw new InvalidArgumentException(
1881                                 '$startPosition must be a positive integer'
1882                         );
1883                 }
1884                 if ( !( is_int( $length ) && $length >= 0 || $length === null ) ) {
1885                         throw new InvalidArgumentException(
1886                                 '$length must be null or an integer greater than or equal to 0'
1887                         );
1888                 }
1889         }
1890
1891         public function buildStringCast( $field ) {
1892                 return $field;
1893         }
1894
1895         public function databasesAreIndependent() {
1896                 return false;
1897         }
1898
1899         public function selectDB( $db ) {
1900                 # Stub. Shouldn't cause serious problems if it's not overridden, but
1901                 # if your database engine supports a concept similar to MySQL's
1902                 # databases you may as well.
1903                 $this->dbName = $db;
1904
1905                 return true;
1906         }
1907
1908         public function getDBname() {
1909                 return $this->dbName;
1910         }
1911
1912         public function getServer() {
1913                 return $this->server;
1914         }
1915
1916         public function tableName( $name, $format = 'quoted' ) {
1917                 # Skip the entire process when we have a string quoted on both ends.
1918                 # Note that we check the end so that we will still quote any use of
1919                 # use of `database`.table. But won't break things if someone wants
1920                 # to query a database table with a dot in the name.
1921                 if ( $this->isQuotedIdentifier( $name ) ) {
1922                         return $name;
1923                 }
1924
1925                 # Lets test for any bits of text that should never show up in a table
1926                 # name. Basically anything like JOIN or ON which are actually part of
1927                 # SQL queries, but may end up inside of the table value to combine
1928                 # sql. Such as how the API is doing.
1929                 # Note that we use a whitespace test rather than a \b test to avoid
1930                 # any remote case where a word like on may be inside of a table name
1931                 # surrounded by symbols which may be considered word breaks.
1932                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1933                         return $name;
1934                 }
1935
1936                 # Split database and table into proper variables.
1937                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
1938
1939                 # Quote $table and apply the prefix if not quoted.
1940                 # $tableName might be empty if this is called from Database::replaceVars()
1941                 $tableName = "{$prefix}{$table}";
1942                 if ( $format === 'quoted'
1943                         && !$this->isQuotedIdentifier( $tableName )
1944                         && $tableName !== ''
1945                 ) {
1946                         $tableName = $this->addIdentifierQuotes( $tableName );
1947                 }
1948
1949                 # Quote $schema and $database and merge them with the table name if needed
1950                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
1951                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
1952
1953                 return $tableName;
1954         }
1955
1956         /**
1957          * Get the table components needed for a query given the currently selected database
1958          *
1959          * @param string $name Table name in the form of db.schema.table, db.table, or table
1960          * @return array (DB name or "" for default, schema name, table prefix, table name)
1961          */
1962         protected function qualifiedTableComponents( $name ) {
1963                 # We reverse the explode so that database.table and table both output the correct table.
1964                 $dbDetails = explode( '.', $name, 3 );
1965                 if ( count( $dbDetails ) == 3 ) {
1966                         list( $database, $schema, $table ) = $dbDetails;
1967                         # We don't want any prefix added in this case
1968                         $prefix = '';
1969                 } elseif ( count( $dbDetails ) == 2 ) {
1970                         list( $database, $table ) = $dbDetails;
1971                         # We don't want any prefix added in this case
1972                         $prefix = '';
1973                         # In dbs that support it, $database may actually be the schema
1974                         # but that doesn't affect any of the functionality here
1975                         $schema = '';
1976                 } else {
1977                         list( $table ) = $dbDetails;
1978                         if ( isset( $this->tableAliases[$table] ) ) {
1979                                 $database = $this->tableAliases[$table]['dbname'];
1980                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
1981                                         ? $this->tableAliases[$table]['schema']
1982                                         : $this->schema;
1983                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
1984                                         ? $this->tableAliases[$table]['prefix']
1985                                         : $this->tablePrefix;
1986                         } else {
1987                                 $database = '';
1988                                 $schema = $this->schema; # Default schema
1989                                 $prefix = $this->tablePrefix; # Default prefix
1990                         }
1991                 }
1992
1993                 return [ $database, $schema, $prefix, $table ];
1994         }
1995
1996         /**
1997          * @param string|null $namespace Database or schema
1998          * @param string $relation Name of table, view, sequence, etc...
1999          * @param string $format One of (raw, quoted)
2000          * @return string Relation name with quoted and merged $namespace as needed
2001          */
2002         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
2003                 if ( strlen( $namespace ) ) {
2004                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
2005                                 $namespace = $this->addIdentifierQuotes( $namespace );
2006                         }
2007                         $relation = $namespace . '.' . $relation;
2008                 }
2009
2010                 return $relation;
2011         }
2012
2013         public function tableNames() {
2014                 $inArray = func_get_args();
2015                 $retVal = [];
2016
2017                 foreach ( $inArray as $name ) {
2018                         $retVal[$name] = $this->tableName( $name );
2019                 }
2020
2021                 return $retVal;
2022         }
2023
2024         public function tableNamesN() {
2025                 $inArray = func_get_args();
2026                 $retVal = [];
2027
2028                 foreach ( $inArray as $name ) {
2029                         $retVal[] = $this->tableName( $name );
2030                 }
2031
2032                 return $retVal;
2033         }
2034
2035         /**
2036          * Get an aliased table name
2037          * e.g. tableName AS newTableName
2038          *
2039          * @param string $name Table name, see tableName()
2040          * @param string|bool $alias Alias (optional)
2041          * @return string SQL name for aliased table. Will not alias a table to its own name
2042          */
2043         protected function tableNameWithAlias( $name, $alias = false ) {
2044                 if ( !$alias || $alias == $name ) {
2045                         return $this->tableName( $name );
2046                 } else {
2047                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2048                 }
2049         }
2050
2051         /**
2052          * Gets an array of aliased table names
2053          *
2054          * @param array $tables [ [alias] => table ]
2055          * @return string[] See tableNameWithAlias()
2056          */
2057         protected function tableNamesWithAlias( $tables ) {
2058                 $retval = [];
2059                 foreach ( $tables as $alias => $table ) {
2060                         if ( is_numeric( $alias ) ) {
2061                                 $alias = $table;
2062                         }
2063                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2064                 }
2065
2066                 return $retval;
2067         }
2068
2069         /**
2070          * Get an aliased field name
2071          * e.g. fieldName AS newFieldName
2072          *
2073          * @param string $name Field name
2074          * @param string|bool $alias Alias (optional)
2075          * @return string SQL name for aliased field. Will not alias a field to its own name
2076          */
2077         protected function fieldNameWithAlias( $name, $alias = false ) {
2078                 if ( !$alias || (string)$alias === (string)$name ) {
2079                         return $name;
2080                 } else {
2081                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
2082                 }
2083         }
2084
2085         /**
2086          * Gets an array of aliased field names
2087          *
2088          * @param array $fields [ [alias] => field ]
2089          * @return string[] See fieldNameWithAlias()
2090          */
2091         protected function fieldNamesWithAlias( $fields ) {
2092                 $retval = [];
2093                 foreach ( $fields as $alias => $field ) {
2094                         if ( is_numeric( $alias ) ) {
2095                                 $alias = $field;
2096                         }
2097                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2098                 }
2099
2100                 return $retval;
2101         }
2102
2103         /**
2104          * Get the aliased table name clause for a FROM clause
2105          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2106          *
2107          * @param array $tables ( [alias] => table )
2108          * @param array $use_index Same as for select()
2109          * @param array $ignore_index Same as for select()
2110          * @param array $join_conds Same as for select()
2111          * @return string
2112          */
2113         protected function tableNamesWithIndexClauseOrJOIN(
2114                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2115         ) {
2116                 $ret = [];
2117                 $retJOIN = [];
2118                 $use_index = (array)$use_index;
2119                 $ignore_index = (array)$ignore_index;
2120                 $join_conds = (array)$join_conds;
2121
2122                 foreach ( $tables as $alias => $table ) {
2123                         if ( !is_string( $alias ) ) {
2124                                 // No alias? Set it equal to the table name
2125                                 $alias = $table;
2126                         }
2127
2128                         if ( is_array( $table ) ) {
2129                                 // A parenthesized group
2130                                 if ( count( $table ) > 1 ) {
2131                                         $joinedTable = '('
2132                                                 . $this->tableNamesWithIndexClauseOrJOIN( $table, $use_index, $ignore_index, $join_conds )
2133                                                 . ')';
2134                                 } else {
2135                                         // Degenerate case
2136                                         $innerTable = reset( $table );
2137                                         $innerAlias = key( $table );
2138                                         $joinedTable = $this->tableNameWithAlias(
2139                                                 $innerTable,
2140                                                 is_string( $innerAlias ) ? $innerAlias : $innerTable
2141                                         );
2142                                 }
2143                         } else {
2144                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2145                         }
2146
2147                         // Is there a JOIN clause for this table?
2148                         if ( isset( $join_conds[$alias] ) ) {
2149                                 list( $joinType, $conds ) = $join_conds[$alias];
2150                                 $tableClause = $joinType;
2151                                 $tableClause .= ' ' . $joinedTable;
2152                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2153                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2154                                         if ( $use != '' ) {
2155                                                 $tableClause .= ' ' . $use;
2156                                         }
2157                                 }
2158                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2159                                         $ignore = $this->ignoreIndexClause(
2160                                                 implode( ',', (array)$ignore_index[$alias] ) );
2161                                         if ( $ignore != '' ) {
2162                                                 $tableClause .= ' ' . $ignore;
2163                                         }
2164                                 }
2165                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2166                                 if ( $on != '' ) {
2167                                         $tableClause .= ' ON (' . $on . ')';
2168                                 }
2169
2170                                 $retJOIN[] = $tableClause;
2171                         } elseif ( isset( $use_index[$alias] ) ) {
2172                                 // Is there an INDEX clause for this table?
2173                                 $tableClause = $joinedTable;
2174                                 $tableClause .= ' ' . $this->useIndexClause(
2175                                                 implode( ',', (array)$use_index[$alias] )
2176                                         );
2177
2178                                 $ret[] = $tableClause;
2179                         } elseif ( isset( $ignore_index[$alias] ) ) {
2180                                 // Is there an INDEX clause for this table?
2181                                 $tableClause = $joinedTable;
2182                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2183                                                 implode( ',', (array)$ignore_index[$alias] )
2184                                         );
2185
2186                                 $ret[] = $tableClause;
2187                         } else {
2188                                 $tableClause = $joinedTable;
2189
2190                                 $ret[] = $tableClause;
2191                         }
2192                 }
2193
2194                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2195                 $implicitJoins = $ret ? implode( ',', $ret ) : "";
2196                 $explicitJoins = $retJOIN ? implode( ' ', $retJOIN ) : "";
2197
2198                 // Compile our final table clause
2199                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2200         }
2201
2202         /**
2203          * Allows for index remapping in queries where this is not consistent across DBMS
2204          *
2205          * @param string $index
2206          * @return string
2207          */
2208         protected function indexName( $index ) {
2209                 return $index;
2210         }
2211
2212         public function addQuotes( $s ) {
2213                 if ( $s instanceof Blob ) {
2214                         $s = $s->fetch();
2215                 }
2216                 if ( $s === null ) {
2217                         return 'NULL';
2218                 } elseif ( is_bool( $s ) ) {
2219                         return (int)$s;
2220                 } else {
2221                         # This will also quote numeric values. This should be harmless,
2222                         # and protects against weird problems that occur when they really
2223                         # _are_ strings such as article titles and string->number->string
2224                         # conversion is not 1:1.
2225                         return "'" . $this->strencode( $s ) . "'";
2226                 }
2227         }
2228
2229         /**
2230          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2231          * MySQL uses `backticks` while basically everything else uses double quotes.
2232          * Since MySQL is the odd one out here the double quotes are our generic
2233          * and we implement backticks in DatabaseMysqlBase.
2234          *
2235          * @param string $s
2236          * @return string
2237          */
2238         public function addIdentifierQuotes( $s ) {
2239                 return '"' . str_replace( '"', '""', $s ) . '"';
2240         }
2241
2242         /**
2243          * Returns if the given identifier looks quoted or not according to
2244          * the database convention for quoting identifiers .
2245          *
2246          * @note Do not use this to determine if untrusted input is safe.
2247          *   A malicious user can trick this function.
2248          * @param string $name
2249          * @return bool
2250          */
2251         public function isQuotedIdentifier( $name ) {
2252                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2253         }
2254
2255         /**
2256          * @param string $s
2257          * @param string $escapeChar
2258          * @return string
2259          */
2260         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2261                 return str_replace( [ $escapeChar, '%', '_' ],
2262                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2263                         $s );
2264         }
2265
2266         public function buildLike() {
2267                 $params = func_get_args();
2268
2269                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2270                         $params = $params[0];
2271                 }
2272
2273                 $s = '';
2274
2275                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2276                 // may escape backslashes, creating problems of double escaping. The `
2277                 // character has good cross-DBMS compatibility, avoiding special operators
2278                 // in MS SQL like ^ and %
2279                 $escapeChar = '`';
2280
2281                 foreach ( $params as $value ) {
2282                         if ( $value instanceof LikeMatch ) {
2283                                 $s .= $value->toString();
2284                         } else {
2285                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2286                         }
2287                 }
2288
2289                 return ' LIKE ' . $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2290         }
2291
2292         public function anyChar() {
2293                 return new LikeMatch( '_' );
2294         }
2295
2296         public function anyString() {
2297                 return new LikeMatch( '%' );
2298         }
2299
2300         public function nextSequenceValue( $seqName ) {
2301                 return null;
2302         }
2303
2304         /**
2305          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2306          * is only needed because a) MySQL must be as efficient as possible due to
2307          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2308          * which index to pick. Anyway, other databases might have different
2309          * indexes on a given table. So don't bother overriding this unless you're
2310          * MySQL.
2311          * @param string $index
2312          * @return string
2313          */
2314         public function useIndexClause( $index ) {
2315                 return '';
2316         }
2317
2318         /**
2319          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2320          * is only needed because a) MySQL must be as efficient as possible due to
2321          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2322          * which index to pick. Anyway, other databases might have different
2323          * indexes on a given table. So don't bother overriding this unless you're
2324          * MySQL.
2325          * @param string $index
2326          * @return string
2327          */
2328         public function ignoreIndexClause( $index ) {
2329                 return '';
2330         }
2331
2332         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2333                 if ( count( $rows ) == 0 ) {
2334                         return;
2335                 }
2336
2337                 // Single row case
2338                 if ( !is_array( reset( $rows ) ) ) {
2339                         $rows = [ $rows ];
2340                 }
2341
2342                 try {
2343                         $this->startAtomic( $fname );
2344                         $affectedRowCount = 0;
2345                         foreach ( $rows as $row ) {
2346                                 // Delete rows which collide with this one
2347                                 $indexWhereClauses = [];
2348                                 foreach ( $uniqueIndexes as $index ) {
2349                                         $indexColumns = (array)$index;
2350                                         $indexRowValues = array_intersect_key( $row, array_flip( $indexColumns ) );
2351                                         if ( count( $indexRowValues ) != count( $indexColumns ) ) {
2352                                                 throw new DBUnexpectedError(
2353                                                         $this,
2354                                                         'New record does not provide all values for unique key (' .
2355                                                         implode( ', ', $indexColumns ) . ')'
2356                                                 );
2357                                         } elseif ( in_array( null, $indexRowValues, true ) ) {
2358                                                 throw new DBUnexpectedError(
2359                                                         $this,
2360                                                         'New record has a null value for unique key (' .
2361                                                         implode( ', ', $indexColumns ) . ')'
2362                                                 );
2363                                         }
2364                                         $indexWhereClauses[] = $this->makeList( $indexRowValues, LIST_AND );
2365                                 }
2366
2367                                 if ( $indexWhereClauses ) {
2368                                         $this->delete( $table, $this->makeList( $indexWhereClauses, LIST_OR ), $fname );
2369                                         $affectedRowCount += $this->affectedRows();
2370                                 }
2371
2372                                 // Now insert the row
2373                                 $this->insert( $table, $row, $fname );
2374                                 $affectedRowCount += $this->affectedRows();
2375                         }
2376                         $this->endAtomic( $fname );
2377                         $this->affectedRowCount = $affectedRowCount;
2378                 } catch ( Exception $e ) {
2379                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2380                         throw $e;
2381                 }
2382         }
2383
2384         /**
2385          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2386          * statement.
2387          *
2388          * @param string $table Table name
2389          * @param array|string $rows Row(s) to insert
2390          * @param string $fname Caller function name
2391          *
2392          * @return ResultWrapper
2393          */
2394         protected function nativeReplace( $table, $rows, $fname ) {
2395                 $table = $this->tableName( $table );
2396
2397                 # Single row case
2398                 if ( !is_array( reset( $rows ) ) ) {
2399                         $rows = [ $rows ];
2400                 }
2401
2402                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2403                 $first = true;
2404
2405                 foreach ( $rows as $row ) {
2406                         if ( $first ) {
2407                                 $first = false;
2408                         } else {
2409                                 $sql .= ',';
2410                         }
2411
2412                         $sql .= '(' . $this->makeList( $row ) . ')';
2413                 }
2414
2415                 return $this->query( $sql, $fname );
2416         }
2417
2418         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2419                 $fname = __METHOD__
2420         ) {
2421                 if ( !count( $rows ) ) {
2422                         return true; // nothing to do
2423                 }
2424
2425                 if ( !is_array( reset( $rows ) ) ) {
2426                         $rows = [ $rows ];
2427                 }
2428
2429                 if ( count( $uniqueIndexes ) ) {
2430                         $clauses = []; // list WHERE clauses that each identify a single row
2431                         foreach ( $rows as $row ) {
2432                                 foreach ( $uniqueIndexes as $index ) {
2433                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2434                                         $rowKey = []; // unique key to this row
2435                                         foreach ( $index as $column ) {
2436                                                 $rowKey[$column] = $row[$column];
2437                                         }
2438                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2439                                 }
2440                         }
2441                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2442                 } else {
2443                         $where = false;
2444                 }
2445
2446                 $affectedRowCount = 0;
2447                 try {
2448                         $this->startAtomic( $fname );
2449                         # Update any existing conflicting row(s)
2450                         if ( $where !== false ) {
2451                                 $ok = $this->update( $table, $set, $where, $fname );
2452                                 $affectedRowCount += $this->affectedRows();
2453                         } else {
2454                                 $ok = true;
2455                         }
2456                         # Now insert any non-conflicting row(s)
2457                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2458                         $affectedRowCount += $this->affectedRows();
2459                         $this->endAtomic( $fname );
2460                         $this->affectedRowCount = $affectedRowCount;
2461                 } catch ( Exception $e ) {
2462                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2463                         throw $e;
2464                 }
2465
2466                 return $ok;
2467         }
2468
2469         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2470                 $fname = __METHOD__
2471         ) {
2472                 if ( !$conds ) {
2473                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2474                 }
2475
2476                 $delTable = $this->tableName( $delTable );
2477                 $joinTable = $this->tableName( $joinTable );
2478                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2479                 if ( $conds != '*' ) {
2480                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2481                 }
2482                 $sql .= ')';
2483
2484                 $this->query( $sql, $fname );
2485         }
2486
2487         public function textFieldSize( $table, $field ) {
2488                 $table = $this->tableName( $table );
2489                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2490                 $res = $this->query( $sql, __METHOD__ );
2491                 $row = $this->fetchObject( $res );
2492
2493                 $m = [];
2494
2495                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2496                         $size = $m[1];
2497                 } else {
2498                         $size = -1;
2499                 }
2500
2501                 return $size;
2502         }
2503
2504         public function delete( $table, $conds, $fname = __METHOD__ ) {
2505                 if ( !$conds ) {
2506                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2507                 }
2508
2509                 $table = $this->tableName( $table );
2510                 $sql = "DELETE FROM $table";
2511
2512                 if ( $conds != '*' ) {
2513                         if ( is_array( $conds ) ) {
2514                                 $conds = $this->makeList( $conds, self::LIST_AND );
2515                         }
2516                         $sql .= ' WHERE ' . $conds;
2517                 }
2518
2519                 return $this->query( $sql, $fname );
2520         }
2521
2522         final public function insertSelect(
2523                 $destTable, $srcTable, $varMap, $conds,
2524                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2525         ) {
2526                 static $hints = [ 'NO_AUTO_COLUMNS' ];
2527
2528                 $insertOptions = (array)$insertOptions;
2529                 $selectOptions = (array)$selectOptions;
2530
2531                 if ( $this->cliMode && $this->isInsertSelectSafe( $insertOptions, $selectOptions ) ) {
2532                         // For massive migrations with downtime, we don't want to select everything
2533                         // into memory and OOM, so do all this native on the server side if possible.
2534                         return $this->nativeInsertSelect(
2535                                 $destTable,
2536                                 $srcTable,
2537                                 $varMap,
2538                                 $conds,
2539                                 $fname,
2540                                 array_diff( $insertOptions, $hints ),
2541                                 $selectOptions,
2542                                 $selectJoinConds
2543                         );
2544                 }
2545
2546                 return $this->nonNativeInsertSelect(
2547                         $destTable,
2548                         $srcTable,
2549                         $varMap,
2550                         $conds,
2551                         $fname,
2552                         array_diff( $insertOptions, $hints ),
2553                         $selectOptions,
2554                         $selectJoinConds
2555                 );
2556         }
2557
2558         /**
2559          * @param array $insertOptions INSERT options
2560          * @param array $selectOptions SELECT options
2561          * @return bool Whether an INSERT SELECT with these options will be replication safe
2562          * @since 1.31
2563          */
2564         protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
2565                 return true;
2566         }
2567
2568         /**
2569          * Implementation of insertSelect() based on select() and insert()
2570          *
2571          * @see IDatabase::insertSelect()
2572          * @since 1.30
2573          * @param string $destTable
2574          * @param string|array $srcTable
2575          * @param array $varMap
2576          * @param array $conds
2577          * @param string $fname
2578          * @param array $insertOptions
2579          * @param array $selectOptions
2580          * @param array $selectJoinConds
2581          * @return bool
2582          */
2583         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2584                 $fname = __METHOD__,
2585                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2586         ) {
2587                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
2588                 // on only the master (without needing row-based-replication). It also makes it easy to
2589                 // know how big the INSERT is going to be.
2590                 $fields = [];
2591                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
2592                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
2593                 }
2594                 $selectOptions[] = 'FOR UPDATE';
2595                 $res = $this->select(
2596                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
2597                 );
2598                 if ( !$res ) {
2599                         return false;
2600                 }
2601
2602                 try {
2603                         $affectedRowCount = 0;
2604                         $this->startAtomic( $fname );
2605                         $rows = [];
2606                         $ok = true;
2607                         foreach ( $res as $row ) {
2608                                 $rows[] = (array)$row;
2609
2610                                 // Avoid inserts that are too huge
2611                                 if ( count( $rows ) >= $this->nonNativeInsertSelectBatchSize ) {
2612                                         $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
2613                                         if ( !$ok ) {
2614                                                 break;
2615                                         }
2616                                         $affectedRowCount += $this->affectedRows();
2617                                         $rows = [];
2618                                 }
2619                         }
2620                         if ( $rows && $ok ) {
2621                                 $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
2622                                 if ( $ok ) {
2623                                         $affectedRowCount += $this->affectedRows();
2624                                 }
2625                         }
2626                         if ( $ok ) {
2627                                 $this->endAtomic( $fname );
2628                                 $this->affectedRowCount = $affectedRowCount;
2629                         } else {
2630                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
2631                         }
2632                         return $ok;
2633                 } catch ( Exception $e ) {
2634                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2635                         throw $e;
2636                 }
2637         }
2638
2639         /**
2640          * Native server-side implementation of insertSelect() for situations where
2641          * we don't want to select everything into memory
2642          *
2643          * @see IDatabase::insertSelect()
2644          * @param string $destTable
2645          * @param string|array $srcTable
2646          * @param array $varMap
2647          * @param array $conds
2648          * @param string $fname
2649          * @param array $insertOptions
2650          * @param array $selectOptions
2651          * @param array $selectJoinConds
2652          * @return bool
2653          */
2654         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2655                 $fname = __METHOD__,
2656                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2657         ) {
2658                 $destTable = $this->tableName( $destTable );
2659
2660                 if ( !is_array( $insertOptions ) ) {
2661                         $insertOptions = [ $insertOptions ];
2662                 }
2663
2664                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2665
2666                 $selectSql = $this->selectSQLText(
2667                         $srcTable,
2668                         array_values( $varMap ),
2669                         $conds,
2670                         $fname,
2671                         $selectOptions,
2672                         $selectJoinConds
2673                 );
2674
2675                 $sql = "INSERT $insertOptions" .
2676                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
2677                         $selectSql;
2678
2679                 return $this->query( $sql, $fname );
2680         }
2681
2682         /**
2683          * Construct a LIMIT query with optional offset. This is used for query
2684          * pages. The SQL should be adjusted so that only the first $limit rows
2685          * are returned. If $offset is provided as well, then the first $offset
2686          * rows should be discarded, and the next $limit rows should be returned.
2687          * If the result of the query is not ordered, then the rows to be returned
2688          * are theoretically arbitrary.
2689          *
2690          * $sql is expected to be a SELECT, if that makes a difference.
2691          *
2692          * The version provided by default works in MySQL and SQLite. It will very
2693          * likely need to be overridden for most other DBMSes.
2694          *
2695          * @param string $sql SQL query we will append the limit too
2696          * @param int $limit The SQL limit
2697          * @param int|bool $offset The SQL offset (default false)
2698          * @throws DBUnexpectedError
2699          * @return string
2700          */
2701         public function limitResult( $sql, $limit, $offset = false ) {
2702                 if ( !is_numeric( $limit ) ) {
2703                         throw new DBUnexpectedError( $this,
2704                                 "Invalid non-numeric limit passed to limitResult()\n" );
2705                 }
2706
2707                 return "$sql LIMIT "
2708                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2709                 . "{$limit} ";
2710         }
2711
2712         public function unionSupportsOrderAndLimit() {
2713                 return true; // True for almost every DB supported
2714         }
2715
2716         public function unionQueries( $sqls, $all ) {
2717                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2718
2719                 return '(' . implode( $glue, $sqls ) . ')';
2720         }
2721
2722         public function unionConditionPermutations(
2723                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
2724                 $options = [], $join_conds = []
2725         ) {
2726                 // First, build the Cartesian product of $permute_conds
2727                 $conds = [ [] ];
2728                 foreach ( $permute_conds as $field => $values ) {
2729                         if ( !$values ) {
2730                                 // Skip empty $values
2731                                 continue;
2732                         }
2733                         $values = array_unique( $values ); // For sanity
2734                         $newConds = [];
2735                         foreach ( $conds as $cond ) {
2736                                 foreach ( $values as $value ) {
2737                                         $cond[$field] = $value;
2738                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
2739                                 }
2740                         }
2741                         $conds = $newConds;
2742                 }
2743
2744                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
2745
2746                 // If there's just one condition and no subordering, hand off to
2747                 // selectSQLText directly.
2748                 if ( count( $conds ) === 1 &&
2749                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
2750                 ) {
2751                         return $this->selectSQLText(
2752                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
2753                         );
2754                 }
2755
2756                 // Otherwise, we need to pull out the order and limit to apply after
2757                 // the union. Then build the SQL queries for each set of conditions in
2758                 // $conds. Then union them together (using UNION ALL, because the
2759                 // product *should* already be distinct).
2760                 $orderBy = $this->makeOrderBy( $options );
2761                 $limit = isset( $options['LIMIT'] ) ? $options['LIMIT'] : null;
2762                 $offset = isset( $options['OFFSET'] ) ? $options['OFFSET'] : false;
2763                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
2764                 if ( !$this->unionSupportsOrderAndLimit() ) {
2765                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
2766                 } else {
2767                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
2768                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
2769                         }
2770                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
2771                                 // We need to increase the limit by the offset rather than
2772                                 // using the offset directly, otherwise it'll skip incorrectly
2773                                 // in the subqueries.
2774                                 $options['LIMIT'] = $limit + $offset;
2775                                 unset( $options['OFFSET'] );
2776                         }
2777                 }
2778
2779                 $sqls = [];
2780                 foreach ( $conds as $cond ) {
2781                         $sqls[] = $this->selectSQLText(
2782                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
2783                         );
2784                 }
2785                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
2786                 if ( $limit !== null ) {
2787                         $sql = $this->limitResult( $sql, $limit, $offset );
2788                 }
2789
2790                 return $sql;
2791         }
2792
2793         public function conditional( $cond, $trueVal, $falseVal ) {
2794                 if ( is_array( $cond ) ) {
2795                         $cond = $this->makeList( $cond, self::LIST_AND );
2796                 }
2797
2798                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2799         }
2800
2801         public function strreplace( $orig, $old, $new ) {
2802                 return "REPLACE({$orig}, {$old}, {$new})";
2803         }
2804
2805         public function getServerUptime() {
2806                 return 0;
2807         }
2808
2809         public function wasDeadlock() {
2810                 return false;
2811         }
2812
2813         public function wasLockTimeout() {
2814                 return false;
2815         }
2816
2817         public function wasErrorReissuable() {
2818                 return false;
2819         }
2820
2821         public function wasReadOnlyError() {
2822                 return false;
2823         }
2824
2825         /**
2826          * Do not use this method outside of Database/DBError classes
2827          *
2828          * @param int|string $errno
2829          * @return bool Whether the given query error was a connection drop
2830          */
2831         public function wasConnectionError( $errno ) {
2832                 return false;
2833         }
2834
2835         public function deadlockLoop() {
2836                 $args = func_get_args();
2837                 $function = array_shift( $args );
2838                 $tries = self::DEADLOCK_TRIES;
2839
2840                 $this->begin( __METHOD__ );
2841
2842                 $retVal = null;
2843                 /** @var Exception $e */
2844                 $e = null;
2845                 do {
2846                         try {
2847                                 $retVal = call_user_func_array( $function, $args );
2848                                 break;
2849                         } catch ( DBQueryError $e ) {
2850                                 if ( $this->wasDeadlock() ) {
2851                                         // Retry after a randomized delay
2852                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
2853                                 } else {
2854                                         // Throw the error back up
2855                                         throw $e;
2856                                 }
2857                         }
2858                 } while ( --$tries > 0 );
2859
2860                 if ( $tries <= 0 ) {
2861                         // Too many deadlocks; give up
2862                         $this->rollback( __METHOD__ );
2863                         throw $e;
2864                 } else {
2865                         $this->commit( __METHOD__ );
2866
2867                         return $retVal;
2868                 }
2869         }
2870
2871         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2872                 # Real waits are implemented in the subclass.
2873                 return 0;
2874         }
2875
2876         public function getReplicaPos() {
2877                 # Stub
2878                 return false;
2879         }
2880
2881         public function getMasterPos() {
2882                 # Stub
2883                 return false;
2884         }
2885
2886         public function serverIsReadOnly() {
2887                 return false;
2888         }
2889
2890         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
2891                 if ( !$this->trxLevel ) {
2892                         throw new DBUnexpectedError( $this, "No transaction is active." );
2893                 }
2894                 $this->trxEndCallbacks[] = [ $callback, $fname ];
2895         }
2896
2897         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
2898                 $this->trxIdleCallbacks[] = [ $callback, $fname ];
2899                 if ( !$this->trxLevel ) {
2900                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
2901                 }
2902         }
2903
2904         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
2905                 if ( $this->trxLevel || $this->getFlag( self::DBO_TRX ) ) {
2906                         // As long as DBO_TRX is set, writes will accumulate until the load balancer issues
2907                         // an implicit commit of all peer databases. This is true even if a transaction has
2908                         // not yet been triggered by writes; make sure $callback runs *after* any such writes.
2909                         $this->trxPreCommitCallbacks[] = [ $callback, $fname ];
2910                 } else {
2911                         // No transaction is active nor will start implicitly, so make one for this callback
2912                         $this->startAtomic( __METHOD__ );
2913                         try {
2914                                 call_user_func( $callback );
2915                                 $this->endAtomic( __METHOD__ );
2916                         } catch ( Exception $e ) {
2917                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2918                                 throw $e;
2919                         }
2920                 }
2921         }
2922
2923         final public function setTransactionListener( $name, callable $callback = null ) {
2924                 if ( $callback ) {
2925                         $this->trxRecurringCallbacks[$name] = $callback;
2926                 } else {
2927                         unset( $this->trxRecurringCallbacks[$name] );
2928                 }
2929         }
2930
2931         /**
2932          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
2933          *
2934          * This method should not be used outside of Database/LoadBalancer
2935          *
2936          * @param bool $suppress
2937          * @since 1.28
2938          */
2939         final public function setTrxEndCallbackSuppression( $suppress ) {
2940                 $this->trxEndCallbacksSuppressed = $suppress;
2941         }
2942
2943         /**
2944          * Actually run and consume any "on transaction idle/resolution" callbacks.
2945          *
2946          * This method should not be used outside of Database/LoadBalancer
2947          *
2948          * @param int $trigger IDatabase::TRIGGER_* constant
2949          * @since 1.20
2950          * @throws Exception
2951          */
2952         public function runOnTransactionIdleCallbacks( $trigger ) {
2953                 if ( $this->trxEndCallbacksSuppressed ) {
2954                         return;
2955                 }
2956
2957                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
2958                 /** @var Exception $e */
2959                 $e = null; // first exception
2960                 do { // callbacks may add callbacks :)
2961                         $callbacks = array_merge(
2962                                 $this->trxIdleCallbacks,
2963                                 $this->trxEndCallbacks // include "transaction resolution" callbacks
2964                         );
2965                         $this->trxIdleCallbacks = []; // consumed (and recursion guard)
2966                         $this->trxEndCallbacks = []; // consumed (recursion guard)
2967                         foreach ( $callbacks as $callback ) {
2968                                 try {
2969                                         list( $phpCallback ) = $callback;
2970                                         $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
2971                                         call_user_func_array( $phpCallback, [ $trigger ] );
2972                                         if ( $autoTrx ) {
2973                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
2974                                         } else {
2975                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
2976                                         }
2977                                 } catch ( Exception $ex ) {
2978                                         call_user_func( $this->errorLogger, $ex );
2979                                         $e = $e ?: $ex;
2980                                         // Some callbacks may use startAtomic/endAtomic, so make sure
2981                                         // their transactions are ended so other callbacks don't fail
2982                                         if ( $this->trxLevel() ) {
2983                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2984                                         }
2985                                 }
2986                         }
2987                 } while ( count( $this->trxIdleCallbacks ) );
2988
2989                 if ( $e instanceof Exception ) {
2990                         throw $e; // re-throw any first exception
2991                 }
2992         }
2993
2994         /**
2995          * Actually run and consume any "on transaction pre-commit" callbacks.
2996          *
2997          * This method should not be used outside of Database/LoadBalancer
2998          *
2999          * @since 1.22
3000          * @throws Exception
3001          */
3002         public function runOnTransactionPreCommitCallbacks() {
3003                 $e = null; // first exception
3004                 do { // callbacks may add callbacks :)
3005                         $callbacks = $this->trxPreCommitCallbacks;
3006                         $this->trxPreCommitCallbacks = []; // consumed (and recursion guard)
3007                         foreach ( $callbacks as $callback ) {
3008                                 try {
3009                                         list( $phpCallback ) = $callback;
3010                                         call_user_func( $phpCallback );
3011                                 } catch ( Exception $ex ) {
3012                                         call_user_func( $this->errorLogger, $ex );
3013                                         $e = $e ?: $ex;
3014                                 }
3015                         }
3016                 } while ( count( $this->trxPreCommitCallbacks ) );
3017
3018                 if ( $e instanceof Exception ) {
3019                         throw $e; // re-throw any first exception
3020                 }
3021         }
3022
3023         /**
3024          * Actually run any "transaction listener" callbacks.
3025          *
3026          * This method should not be used outside of Database/LoadBalancer
3027          *
3028          * @param int $trigger IDatabase::TRIGGER_* constant
3029          * @throws Exception
3030          * @since 1.20
3031          */
3032         public function runTransactionListenerCallbacks( $trigger ) {
3033                 if ( $this->trxEndCallbacksSuppressed ) {
3034                         return;
3035                 }
3036
3037                 /** @var Exception $e */
3038                 $e = null; // first exception
3039
3040                 foreach ( $this->trxRecurringCallbacks as $phpCallback ) {
3041                         try {
3042                                 $phpCallback( $trigger, $this );
3043                         } catch ( Exception $ex ) {
3044                                 call_user_func( $this->errorLogger, $ex );
3045                                 $e = $e ?: $ex;
3046                         }
3047                 }
3048
3049                 if ( $e instanceof Exception ) {
3050                         throw $e; // re-throw any first exception
3051                 }
3052         }
3053
3054         final public function startAtomic( $fname = __METHOD__ ) {
3055                 if ( !$this->trxLevel ) {
3056                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
3057                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
3058                         // in all changes being in one transaction to keep requests transactional.
3059                         if ( !$this->getFlag( self::DBO_TRX ) ) {
3060                                 $this->trxAutomaticAtomic = true;
3061                         }
3062                 }
3063
3064                 $this->trxAtomicLevels[] = $fname;
3065         }
3066
3067         final public function endAtomic( $fname = __METHOD__ ) {
3068                 if ( !$this->trxLevel ) {
3069                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
3070                 }
3071                 if ( !$this->trxAtomicLevels ||
3072                         array_pop( $this->trxAtomicLevels ) !== $fname
3073                 ) {
3074                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
3075                 }
3076
3077                 if ( !$this->trxAtomicLevels && $this->trxAutomaticAtomic ) {
3078                         $this->commit( $fname, self::FLUSHING_INTERNAL );
3079                 }
3080         }
3081
3082         final public function doAtomicSection( $fname, callable $callback ) {
3083                 $this->startAtomic( $fname );
3084                 try {
3085                         $res = call_user_func_array( $callback, [ $this, $fname ] );
3086                 } catch ( Exception $e ) {
3087                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
3088                         throw $e;
3089                 }
3090                 $this->endAtomic( $fname );
3091
3092                 return $res;
3093         }
3094
3095         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
3096                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
3097                 if ( $this->trxLevel ) {
3098                         if ( $this->trxAtomicLevels ) {
3099                                 $levels = implode( ', ', $this->trxAtomicLevels );
3100                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
3101                                 throw new DBUnexpectedError( $this, $msg );
3102                         } elseif ( !$this->trxAutomatic ) {
3103                                 $msg = "$fname: Explicit transaction already active (from {$this->trxFname}).";
3104                                 throw new DBUnexpectedError( $this, $msg );
3105                         } else {
3106                                 // @TODO: make this an exception at some point
3107                                 $msg = "$fname: Implicit transaction already active (from {$this->trxFname}).";
3108                                 $this->queryLogger->error( $msg );
3109                                 return; // join the main transaction set
3110                         }
3111                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
3112                         // @TODO: make this an exception at some point
3113                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
3114                         $this->queryLogger->error( $msg );
3115                         return; // let any writes be in the main transaction
3116                 }
3117
3118                 // Avoid fatals if close() was called
3119                 $this->assertOpen();
3120
3121                 $this->doBegin( $fname );
3122                 $this->trxTimestamp = microtime( true );
3123                 $this->trxFname = $fname;
3124                 $this->trxDoneWrites = false;
3125                 $this->trxAutomaticAtomic = false;
3126                 $this->trxAtomicLevels = [];
3127                 $this->trxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
3128                 $this->trxWriteDuration = 0.0;
3129                 $this->trxWriteQueryCount = 0;
3130                 $this->trxWriteAffectedRows = 0;
3131                 $this->trxWriteAdjDuration = 0.0;
3132                 $this->trxWriteAdjQueryCount = 0;
3133                 $this->trxWriteCallers = [];
3134                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
3135                 // Get an estimate of the replica DB lag before then, treating estimate staleness
3136                 // as lag itself just to be safe
3137                 $status = $this->getApproximateLagStatus();
3138                 $this->trxReplicaLag = $status['lag'] + ( microtime( true ) - $status['since'] );
3139                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
3140                 // caller will think its OK to muck around with the transaction just because startAtomic()
3141                 // has not yet completed (e.g. setting trxAtomicLevels).
3142                 $this->trxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
3143         }
3144
3145         /**
3146          * Issues the BEGIN command to the database server.
3147          *
3148          * @see Database::begin()
3149          * @param string $fname
3150          */
3151         protected function doBegin( $fname ) {
3152                 $this->query( 'BEGIN', $fname );
3153                 $this->trxLevel = 1;
3154         }
3155
3156         final public function commit( $fname = __METHOD__, $flush = '' ) {
3157                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3158                         // There are still atomic sections open. This cannot be ignored
3159                         $levels = implode( ', ', $this->trxAtomicLevels );
3160                         throw new DBUnexpectedError(
3161                                 $this,
3162                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3163                         );
3164                 }
3165
3166                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3167                         if ( !$this->trxLevel ) {
3168                                 return; // nothing to do
3169                         } elseif ( !$this->trxAutomatic ) {
3170                                 throw new DBUnexpectedError(
3171                                         $this,
3172                                         "$fname: Flushing an explicit transaction, getting out of sync."
3173                                 );
3174                         }
3175                 } else {
3176                         if ( !$this->trxLevel ) {
3177                                 $this->queryLogger->error(
3178                                         "$fname: No transaction to commit, something got out of sync." );
3179                                 return; // nothing to do
3180                         } elseif ( $this->trxAutomatic ) {
3181                                 // @TODO: make this an exception at some point
3182                                 $msg = "$fname: Explicit commit of implicit transaction.";
3183                                 $this->queryLogger->error( $msg );
3184                                 return; // wait for the main transaction set commit round
3185                         }
3186                 }
3187
3188                 // Avoid fatals if close() was called
3189                 $this->assertOpen();
3190
3191                 $this->runOnTransactionPreCommitCallbacks();
3192                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3193                 $this->doCommit( $fname );
3194                 if ( $this->trxDoneWrites ) {
3195                         $this->lastWriteTime = microtime( true );
3196                         $this->trxProfiler->transactionWritingOut(
3197                                 $this->server,
3198                                 $this->dbName,
3199                                 $this->trxShortId,
3200                                 $writeTime,
3201                                 $this->trxWriteAffectedRows
3202                         );
3203                 }
3204
3205                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3206                 $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3207         }
3208
3209         /**
3210          * Issues the COMMIT command to the database server.
3211          *
3212          * @see Database::commit()
3213          * @param string $fname
3214          */
3215         protected function doCommit( $fname ) {
3216                 if ( $this->trxLevel ) {
3217                         $this->query( 'COMMIT', $fname );
3218                         $this->trxLevel = 0;
3219                 }
3220         }
3221
3222         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3223                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3224                         if ( !$this->trxLevel ) {
3225                                 return; // nothing to do
3226                         }
3227                 } else {
3228                         if ( !$this->trxLevel ) {
3229                                 $this->queryLogger->error(
3230                                         "$fname: No transaction to rollback, something got out of sync." );
3231                                 return; // nothing to do
3232                         } elseif ( $this->getFlag( self::DBO_TRX ) ) {
3233                                 throw new DBUnexpectedError(
3234                                         $this,
3235                                         "$fname: Expected mass rollback of all peer databases (DBO_TRX set)."
3236                                 );
3237                         }
3238                 }
3239
3240                 // Avoid fatals if close() was called
3241                 $this->assertOpen();
3242
3243                 $this->doRollback( $fname );
3244                 $this->trxAtomicLevels = [];
3245                 if ( $this->trxDoneWrites ) {
3246                         $this->trxProfiler->transactionWritingOut(
3247                                 $this->server,
3248                                 $this->dbName,
3249                                 $this->trxShortId
3250                         );
3251                 }
3252
3253                 $this->trxIdleCallbacks = []; // clear
3254                 $this->trxPreCommitCallbacks = []; // clear
3255                 try {
3256                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
3257                 } catch ( Exception $e ) {
3258                         // already logged; finish and let LoadBalancer move on during mass-rollback
3259                 }
3260                 try {
3261                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
3262                 } catch ( Exception $e ) {
3263                         // already logged; let LoadBalancer move on during mass-rollback
3264                 }
3265
3266                 $this->affectedRowCount = 0; // for the sake of consistency
3267         }
3268
3269         /**
3270          * Issues the ROLLBACK command to the database server.
3271          *
3272          * @see Database::rollback()
3273          * @param string $fname
3274          */
3275         protected function doRollback( $fname ) {
3276                 if ( $this->trxLevel ) {
3277                         # Disconnects cause rollback anyway, so ignore those errors
3278                         $ignoreErrors = true;
3279                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
3280                         $this->trxLevel = 0;
3281                 }
3282         }
3283
3284         public function flushSnapshot( $fname = __METHOD__ ) {
3285                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
3286                         // This only flushes transactions to clear snapshots, not to write data
3287                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3288                         throw new DBUnexpectedError(
3289                                 $this,
3290                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
3291                         );
3292                 }
3293
3294                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3295         }
3296
3297         public function explicitTrxActive() {
3298                 return $this->trxLevel && ( $this->trxAtomicLevels || !$this->trxAutomatic );
3299         }
3300
3301         public function duplicateTableStructure(
3302                 $oldName, $newName, $temporary = false, $fname = __METHOD__
3303         ) {
3304                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3305         }
3306
3307         public function listTables( $prefix = null, $fname = __METHOD__ ) {
3308                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3309         }
3310
3311         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3312                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3313         }
3314
3315         public function timestamp( $ts = 0 ) {
3316                 $t = new ConvertibleTimestamp( $ts );
3317                 // Let errors bubble up to avoid putting garbage in the DB
3318                 return $t->getTimestamp( TS_MW );
3319         }
3320
3321         public function timestampOrNull( $ts = null ) {
3322                 if ( is_null( $ts ) ) {
3323                         return null;
3324                 } else {
3325                         return $this->timestamp( $ts );
3326                 }
3327         }
3328
3329         public function affectedRows() {
3330                 return ( $this->affectedRowCount === null )
3331                         ? $this->fetchAffectedRowCount() // default to driver value
3332                         : $this->affectedRowCount;
3333         }
3334
3335         /**
3336          * @return int Number of retrieved rows according to the driver
3337          */
3338         abstract protected function fetchAffectedRowCount();
3339
3340         /**
3341          * Take the result from a query, and wrap it in a ResultWrapper if
3342          * necessary. Boolean values are passed through as is, to indicate success
3343          * of write queries or failure.
3344          *
3345          * Once upon a time, Database::query() returned a bare MySQL result
3346          * resource, and it was necessary to call this function to convert it to
3347          * a wrapper. Nowadays, raw database objects are never exposed to external
3348          * callers, so this is unnecessary in external code.
3349          *
3350          * @param bool|ResultWrapper|resource|object $result
3351          * @return bool|ResultWrapper
3352          */
3353         protected function resultObject( $result ) {
3354                 if ( !$result ) {
3355                         return false;
3356                 } elseif ( $result instanceof ResultWrapper ) {
3357                         return $result;
3358                 } elseif ( $result === true ) {
3359                         // Successful write query
3360                         return $result;
3361                 } else {
3362                         return new ResultWrapper( $this, $result );
3363                 }
3364         }
3365
3366         public function ping( &$rtt = null ) {
3367                 // Avoid hitting the server if it was hit recently
3368                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
3369                         if ( !func_num_args() || $this->rttEstimate > 0 ) {
3370                                 $rtt = $this->rttEstimate;
3371                                 return true; // don't care about $rtt
3372                         }
3373                 }
3374
3375                 // This will reconnect if possible or return false if not
3376                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
3377                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
3378                 $this->restoreFlags( self::RESTORE_PRIOR );
3379
3380                 if ( $ok ) {
3381                         $rtt = $this->rttEstimate;
3382                 }
3383
3384                 return $ok;
3385         }
3386
3387         /**
3388          * Close existing database connection and open a new connection
3389          *
3390          * @return bool True if new connection is opened successfully, false if error
3391          */
3392         protected function reconnect() {
3393                 $this->closeConnection();
3394                 $this->opened = false;
3395                 $this->conn = false;
3396                 try {
3397                         $this->open( $this->server, $this->user, $this->password, $this->dbName );
3398                         $this->lastPing = microtime( true );
3399                         $ok = true;
3400                 } catch ( DBConnectionError $e ) {
3401                         $ok = false;
3402                 }
3403
3404                 return $ok;
3405         }
3406
3407         public function getSessionLagStatus() {
3408                 return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
3409         }
3410
3411         /**
3412          * Get the replica DB lag when the current transaction started
3413          *
3414          * This is useful when transactions might use snapshot isolation
3415          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
3416          * is this lag plus transaction duration. If they don't, it is still
3417          * safe to be pessimistic. This returns null if there is no transaction.
3418          *
3419          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
3420          * @since 1.27
3421          */
3422         protected function getTransactionLagStatus() {
3423                 return $this->trxLevel
3424                         ? [ 'lag' => $this->trxReplicaLag, 'since' => $this->trxTimestamp() ]
3425                         : null;
3426         }
3427
3428         /**
3429          * Get a replica DB lag estimate for this server
3430          *
3431          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
3432          * @since 1.27
3433          */
3434         protected function getApproximateLagStatus() {
3435                 return [
3436                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
3437                         'since' => microtime( true )
3438                 ];
3439         }
3440
3441         /**
3442          * Merge the result of getSessionLagStatus() for several DBs
3443          * using the most pessimistic values to estimate the lag of
3444          * any data derived from them in combination
3445          *
3446          * This is information is useful for caching modules
3447          *
3448          * @see WANObjectCache::set()
3449          * @see WANObjectCache::getWithSetCallback()
3450          *
3451          * @param IDatabase $db1
3452          * @param IDatabase $db2 [optional]
3453          * @return array Map of values:
3454          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3455          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3456          *   - pending: whether any of the DBs have uncommitted changes
3457          * @throws DBError
3458          * @since 1.27
3459          */
3460         public static function getCacheSetOptions( IDatabase $db1, IDatabase $db2 = null ) {
3461                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3462                 foreach ( func_get_args() as $db ) {
3463                         /** @var IDatabase $db */
3464                         $status = $db->getSessionLagStatus();
3465                         if ( $status['lag'] === false ) {
3466                                 $res['lag'] = false;
3467                         } elseif ( $res['lag'] !== false ) {
3468                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3469                         }
3470                         $res['since'] = min( $res['since'], $status['since'] );
3471                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3472                 }
3473
3474                 return $res;
3475         }
3476
3477         public function getLag() {
3478                 return 0;
3479         }
3480
3481         public function maxListLen() {
3482                 return 0;
3483         }
3484
3485         public function encodeBlob( $b ) {
3486                 return $b;
3487         }
3488
3489         public function decodeBlob( $b ) {
3490                 if ( $b instanceof Blob ) {
3491                         $b = $b->fetch();
3492                 }
3493                 return $b;
3494         }
3495
3496         public function setSessionOptions( array $options ) {
3497         }
3498
3499         public function sourceFile(
3500                 $filename,
3501                 callable $lineCallback = null,
3502                 callable $resultCallback = null,
3503                 $fname = false,
3504                 callable $inputCallback = null
3505         ) {
3506                 Wikimedia\suppressWarnings();
3507                 $fp = fopen( $filename, 'r' );
3508                 Wikimedia\restoreWarnings();
3509
3510                 if ( false === $fp ) {
3511                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
3512                 }
3513
3514                 if ( !$fname ) {
3515                         $fname = __METHOD__ . "( $filename )";
3516                 }
3517
3518                 try {
3519                         $error = $this->sourceStream(
3520                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3521                 } catch ( Exception $e ) {
3522                         fclose( $fp );
3523                         throw $e;
3524                 }
3525
3526                 fclose( $fp );
3527
3528                 return $error;
3529         }
3530
3531         public function setSchemaVars( $vars ) {
3532                 $this->schemaVars = $vars;
3533         }
3534
3535         public function sourceStream(
3536                 $fp,
3537                 callable $lineCallback = null,
3538                 callable $resultCallback = null,
3539                 $fname = __METHOD__,
3540                 callable $inputCallback = null
3541         ) {
3542                 $delimiterReset = new ScopedCallback(
3543                         function ( $delimiter ) {
3544                                 $this->delimiter = $delimiter;
3545                         },
3546                         [ $this->delimiter ]
3547                 );
3548                 $cmd = '';
3549
3550                 while ( !feof( $fp ) ) {
3551                         if ( $lineCallback ) {
3552                                 call_user_func( $lineCallback );
3553                         }
3554
3555                         $line = trim( fgets( $fp ) );
3556
3557                         if ( $line == '' ) {
3558                                 continue;
3559                         }
3560
3561                         if ( '-' == $line[0] && '-' == $line[1] ) {
3562                                 continue;
3563                         }
3564
3565                         if ( $cmd != '' ) {
3566                                 $cmd .= ' ';
3567                         }
3568
3569                         $done = $this->streamStatementEnd( $cmd, $line );
3570
3571                         $cmd .= "$line\n";
3572
3573                         if ( $done || feof( $fp ) ) {
3574                                 $cmd = $this->replaceVars( $cmd );
3575
3576                                 if ( $inputCallback ) {
3577                                         $callbackResult = call_user_func( $inputCallback, $cmd );
3578
3579                                         if ( is_string( $callbackResult ) || !$callbackResult ) {
3580                                                 $cmd = $callbackResult;
3581                                         }
3582                                 }
3583
3584                                 if ( $cmd ) {
3585                                         $res = $this->query( $cmd, $fname );
3586
3587                                         if ( $resultCallback ) {
3588                                                 call_user_func( $resultCallback, $res, $this );
3589                                         }
3590
3591                                         if ( false === $res ) {
3592                                                 $err = $this->lastError();
3593
3594                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3595                                         }
3596                                 }
3597                                 $cmd = '';
3598                         }
3599                 }
3600
3601                 ScopedCallback::consume( $delimiterReset );
3602                 return true;
3603         }
3604
3605         /**
3606          * Called by sourceStream() to check if we've reached a statement end
3607          *
3608          * @param string &$sql SQL assembled so far
3609          * @param string &$newLine New line about to be added to $sql
3610          * @return bool Whether $newLine contains end of the statement
3611          */
3612         public function streamStatementEnd( &$sql, &$newLine ) {
3613                 if ( $this->delimiter ) {
3614                         $prev = $newLine;
3615                         $newLine = preg_replace(
3616                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3617                         if ( $newLine != $prev ) {
3618                                 return true;
3619                         }
3620                 }
3621
3622                 return false;
3623         }
3624
3625         /**
3626          * Database independent variable replacement. Replaces a set of variables
3627          * in an SQL statement with their contents as given by $this->getSchemaVars().
3628          *
3629          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3630          *
3631          * - '{$var}' should be used for text and is passed through the database's
3632          *   addQuotes method.
3633          * - `{$var}` should be used for identifiers (e.g. table and database names).
3634          *   It is passed through the database's addIdentifierQuotes method which
3635          *   can be overridden if the database uses something other than backticks.
3636          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
3637          *   database's tableName method.
3638          * - / *i* / passes the name that follows through the database's indexName method.
3639          * - In all other cases, / *$var* / is left unencoded. Except for table options,
3640          *   its use should be avoided. In 1.24 and older, string encoding was applied.
3641          *
3642          * @param string $ins SQL statement to replace variables in
3643          * @return string The new SQL statement with variables replaced
3644          */
3645         protected function replaceVars( $ins ) {
3646                 $vars = $this->getSchemaVars();
3647                 return preg_replace_callback(
3648                         '!
3649                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
3650                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
3651                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
3652                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
3653                         !x',
3654                         function ( $m ) use ( $vars ) {
3655                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
3656                                 // check for both nonexistent keys *and* the empty string.
3657                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
3658                                         if ( $m[1] === 'i' ) {
3659                                                 return $this->indexName( $m[2] );
3660                                         } else {
3661                                                 return $this->tableName( $m[2] );
3662                                         }
3663                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
3664                                         return $this->addQuotes( $vars[$m[3]] );
3665                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
3666                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
3667                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
3668                                         return $vars[$m[5]];
3669                                 } else {
3670                                         return $m[0];
3671                                 }
3672                         },
3673                         $ins
3674                 );
3675         }
3676
3677         /**
3678          * Get schema variables. If none have been set via setSchemaVars(), then
3679          * use some defaults from the current object.
3680          *
3681          * @return array
3682          */
3683         protected function getSchemaVars() {
3684                 if ( $this->schemaVars ) {
3685                         return $this->schemaVars;
3686                 } else {
3687                         return $this->getDefaultSchemaVars();
3688                 }
3689         }
3690
3691         /**
3692          * Get schema variables to use if none have been set via setSchemaVars().
3693          *
3694          * Override this in derived classes to provide variables for tables.sql
3695          * and SQL patch files.
3696          *
3697          * @return array
3698          */
3699         protected function getDefaultSchemaVars() {
3700                 return [];
3701         }
3702
3703         public function lockIsFree( $lockName, $method ) {
3704                 // RDBMs methods for checking named locks may or may not count this thread itself.
3705                 // In MySQL, IS_FREE_LOCK() returns 0 if the thread already has the lock. This is
3706                 // the behavior choosen by the interface for this method.
3707                 return !isset( $this->namedLocksHeld[$lockName] );
3708         }
3709
3710         public function lock( $lockName, $method, $timeout = 5 ) {
3711                 $this->namedLocksHeld[$lockName] = 1;
3712
3713                 return true;
3714         }
3715
3716         public function unlock( $lockName, $method ) {
3717                 unset( $this->namedLocksHeld[$lockName] );
3718
3719                 return true;
3720         }
3721
3722         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
3723                 if ( $this->writesOrCallbacksPending() ) {
3724                         // This only flushes transactions to clear snapshots, not to write data
3725                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3726                         throw new DBUnexpectedError(
3727                                 $this,
3728                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
3729                         );
3730                 }
3731
3732                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
3733                         return null;
3734                 }
3735
3736                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
3737                         if ( $this->trxLevel() ) {
3738                                 // There is a good chance an exception was thrown, causing any early return
3739                                 // from the caller. Let any error handler get a chance to issue rollback().
3740                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
3741                                 $this->onTransactionResolution(
3742                                         function () use ( $lockKey, $fname ) {
3743                                                 $this->unlock( $lockKey, $fname );
3744                                         },
3745                                         $fname
3746                                 );
3747                         } else {
3748                                 $this->unlock( $lockKey, $fname );
3749                         }
3750                 } );
3751
3752                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3753
3754                 return $unlocker;
3755         }
3756
3757         public function namedLocksEnqueue() {
3758                 return false;
3759         }
3760
3761         public function tableLocksHaveTransactionScope() {
3762                 return true;
3763         }
3764
3765         final public function lockTables( array $read, array $write, $method ) {
3766                 if ( $this->writesOrCallbacksPending() ) {
3767                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
3768                 }
3769
3770                 if ( $this->tableLocksHaveTransactionScope() ) {
3771                         $this->startAtomic( $method );
3772                 }
3773
3774                 return $this->doLockTables( $read, $write, $method );
3775         }
3776
3777         /**
3778          * Helper function for lockTables() that handles the actual table locking
3779          *
3780          * @param array $read Array of tables to lock for read access
3781          * @param array $write Array of tables to lock for write access
3782          * @param string $method Name of caller
3783          * @return true
3784          */
3785         protected function doLockTables( array $read, array $write, $method ) {
3786                 return true;
3787         }
3788
3789         final public function unlockTables( $method ) {
3790                 if ( $this->tableLocksHaveTransactionScope() ) {
3791                         $this->endAtomic( $method );
3792
3793                         return true; // locks released on COMMIT/ROLLBACK
3794                 }
3795
3796                 return $this->doUnlockTables( $method );
3797         }
3798
3799         /**
3800          * Helper function for unlockTables() that handles the actual table unlocking
3801          *
3802          * @param string $method Name of caller
3803          * @return true
3804          */
3805         protected function doUnlockTables( $method ) {
3806                 return true;
3807         }
3808
3809         /**
3810          * Delete a table
3811          * @param string $tableName
3812          * @param string $fName
3813          * @return bool|ResultWrapper
3814          * @since 1.18
3815          */
3816         public function dropTable( $tableName, $fName = __METHOD__ ) {
3817                 if ( !$this->tableExists( $tableName, $fName ) ) {
3818                         return false;
3819                 }
3820                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
3821
3822                 return $this->query( $sql, $fName );
3823         }
3824
3825         public function getInfinity() {
3826                 return 'infinity';
3827         }
3828
3829         public function encodeExpiry( $expiry ) {
3830                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3831                         ? $this->getInfinity()
3832                         : $this->timestamp( $expiry );
3833         }
3834
3835         public function decodeExpiry( $expiry, $format = TS_MW ) {
3836                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
3837                         return 'infinity';
3838                 }
3839
3840                 return ConvertibleTimestamp::convert( $format, $expiry );
3841         }
3842
3843         public function setBigSelects( $value = true ) {
3844                 // no-op
3845         }
3846
3847         public function isReadOnly() {
3848                 return ( $this->getReadOnlyReason() !== false );
3849         }
3850
3851         /**
3852          * @return string|bool Reason this DB is read-only or false if it is not
3853          */
3854         protected function getReadOnlyReason() {
3855                 $reason = $this->getLBInfo( 'readOnlyReason' );
3856
3857                 return is_string( $reason ) ? $reason : false;
3858         }
3859
3860         public function setTableAliases( array $aliases ) {
3861                 $this->tableAliases = $aliases;
3862         }
3863
3864         /**
3865          * @return bool Whether a DB user is required to access the DB
3866          * @since 1.28
3867          */
3868         protected function requiresDatabaseUser() {
3869                 return true;
3870         }
3871
3872         /**
3873          * Get the underlying binding connection handle
3874          *
3875          * Makes sure the connection resource is set (disconnects and ping() failure can unset it).
3876          * This catches broken callers than catch and ignore disconnection exceptions.
3877          * Unlike checking isOpen(), this is safe to call inside of open().
3878          *
3879          * @return resource|object
3880          * @throws DBUnexpectedError
3881          * @since 1.26
3882          */
3883         protected function getBindingHandle() {
3884                 if ( !$this->conn ) {
3885                         throw new DBUnexpectedError(
3886                                 $this,
3887                                 'DB connection was already closed or the connection dropped.'
3888                         );
3889                 }
3890
3891                 return $this->conn;
3892         }
3893
3894         /**
3895          * @since 1.19
3896          * @return string
3897          */
3898         public function __toString() {
3899                 return (string)$this->conn;
3900         }
3901
3902         /**
3903          * Make sure that copies do not share the same client binding handle
3904          * @throws DBConnectionError
3905          */
3906         public function __clone() {
3907                 $this->connLogger->warning(
3908                         "Cloning " . static::class . " is not recomended; forking connection:\n" .
3909                         ( new RuntimeException() )->getTraceAsString()
3910                 );
3911
3912                 if ( $this->isOpen() ) {
3913                         // Open a new connection resource without messing with the old one
3914                         $this->opened = false;
3915                         $this->conn = false;
3916                         $this->trxEndCallbacks = []; // don't copy
3917                         $this->handleSessionLoss(); // no trx or locks anymore
3918                         $this->open( $this->server, $this->user, $this->password, $this->dbName );
3919                         $this->lastPing = microtime( true );
3920                 }
3921         }
3922
3923         /**
3924          * Called by serialize. Throw an exception when DB connection is serialized.
3925          * This causes problems on some database engines because the connection is
3926          * not restored on unserialize.
3927          */
3928         public function __sleep() {
3929                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
3930                         'the connection is not restored on wakeup.' );
3931         }
3932
3933         /**
3934          * Run a few simple sanity checks and close dangling connections
3935          */
3936         public function __destruct() {
3937                 if ( $this->trxLevel && $this->trxDoneWrites ) {
3938                         trigger_error( "Uncommitted DB writes (transaction from {$this->trxFname})." );
3939                 }
3940
3941                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
3942                 if ( $danglingWriters ) {
3943                         $fnames = implode( ', ', $danglingWriters );
3944                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
3945                 }
3946
3947                 if ( $this->conn ) {
3948                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
3949                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
3950                         Wikimedia\suppressWarnings();
3951                         $this->closeConnection();
3952                         Wikimedia\restoreWarnings();
3953                         $this->conn = false;
3954                         $this->opened = false;
3955                 }
3956         }
3957 }
3958
3959 class_alias( Database::class, 'DatabaseBase' ); // b/c for old name
3960 class_alias( Database::class, 'Database' ); // b/c global alias