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