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 Wikimedia\ScopedCallback;
  31 use Wikimedia\Timestamp\ConvertibleTimestamp;
  32 use MediaWiki;
  33 use BagOStuff;
  34 use HashBagOStuff;
  35 use InvalidArgumentException;
  36 use Exception;
  37 use RuntimeException;
  38
  39 /**
  40  * Relational database abstraction object
  41  *
  42  * @ingroup Database
  43  * @since 1.28
  44  */
  45 abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAwareInterface {
  46         /** Number of times to re-try an operation in case of deadlock */
  47         const DEADLOCK_TRIES = 4;
  48         /** Minimum time to wait before retry, in microseconds */
  49         const DEADLOCK_DELAY_MIN = 500000;
  50         /** Maximum time to wait before retry */
  51         const DEADLOCK_DELAY_MAX = 1500000;
  52
  53         /** How long before it is worth doing a dummy query to test the connection */
  54         const PING_TTL = 1.0;
  55         const PING_QUERY = 'SELECT 1 AS ping';
  56
  57         const TINY_WRITE_SEC = 0.010;
  58         const SLOW_WRITE_SEC = 0.500;
  59         const SMALL_WRITE_ROWS = 100;
  60
  61         /** @var string SQL query */
  62         protected $mLastQuery = '';
  63         /** @var float|bool UNIX timestamp of last write query */
  64         protected $mLastWriteTime = false;
  65         /** @var string|bool */
  66         protected $mPHPError = false;
  67         /** @var string */
  68         protected $mServer;
  69         /** @var string */
  70         protected $mUser;
  71         /** @var string */
  72         protected $mPassword;
  73         /** @var string */
  74         protected $mDBname;
  75         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  76         protected $tableAliases = [];
  77         /** @var bool Whether this PHP instance is for a CLI script */
  78         protected $cliMode;
  79         /** @var string Agent name for query profiling */
  80         protected $agent;
  81
  82         /** @var BagOStuff APC cache */
  83         protected $srvCache;
  84         /** @var LoggerInterface */
  85         protected $connLogger;
  86         /** @var LoggerInterface */
  87         protected $queryLogger;
  88         /** @var callback Error logging callback */
  89         protected $errorLogger;
  90
  91         /** @var resource|null Database connection */
  92         protected $mConn = null;
  93         /** @var bool */
  94         protected $mOpened = false;
  95
  96         /** @var array[] List of (callable, method name) */
  97         protected $mTrxIdleCallbacks = [];
  98         /** @var array[] List of (callable, method name) */
  99         protected $mTrxPreCommitCallbacks = [];
 100         /** @var array[] List of (callable, method name) */
 101         protected $mTrxEndCallbacks = [];
 102         /** @var callable[] Map of (name => callable) */
 103         protected $mTrxRecurringCallbacks = [];
 104         /** @var bool Whether to suppress triggering of transaction end callbacks */
 105         protected $mTrxEndCallbacksSuppressed = false;
 106
 107         /** @var string */
 108         protected $mTablePrefix = '';
 109         /** @var string */
 110         protected $mSchema = '';
 111         /** @var int */
 112         protected $mFlags;
 113         /** @var array */
 114         protected $mLBInfo = [];
 115         /** @var bool|null */
 116         protected $mDefaultBigSelects = null;
 117         /** @var array|bool */
 118         protected $mSchemaVars = false;
 119         /** @var array */
 120         protected $mSessionVars = [];
 121         /** @var array|null */
 122         protected $preparedArgs;
 123         /** @var string|bool|null Stashed value of html_errors INI setting */
 124         protected $htmlErrors;
 125         /** @var string */
 126         protected $delimiter = ';';
 127         /** @var DatabaseDomain */
 128         protected $currentDomain;
 129
 130         /**
 131          * Either 1 if a transaction is active or 0 otherwise.
 132          * The other Trx fields may not be meaningfull if this is 0.
 133          *
 134          * @var int
 135          */
 136         protected $mTrxLevel = 0;
 137         /**
 138          * Either a short hexidecimal string if a transaction is active or ""
 139          *
 140          * @var string
 141          * @see Database::mTrxLevel
 142          */
 143         protected $mTrxShortId = '';
 144         /**
 145          * The UNIX time that the transaction started. Callers can assume that if
 146          * snapshot isolation is used, then the data is *at least* up to date to that
 147          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 148          *
 149          * @var float|null
 150          * @see Database::mTrxLevel
 151          */
 152         private $mTrxTimestamp = null;
 153         /** @var float Lag estimate at the time of BEGIN */
 154         private $mTrxReplicaLag = null;
 155         /**
 156          * Remembers the function name given for starting the most recent transaction via begin().
 157          * Used to provide additional context for error reporting.
 158          *
 159          * @var string
 160          * @see Database::mTrxLevel
 161          */
 162         private $mTrxFname = null;
 163         /**
 164          * Record if possible write queries were done in the last transaction started
 165          *
 166          * @var bool
 167          * @see Database::mTrxLevel
 168          */
 169         private $mTrxDoneWrites = false;
 170         /**
 171          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 172          *
 173          * @var bool
 174          * @see Database::mTrxLevel
 175          */
 176         private $mTrxAutomatic = false;
 177         /**
 178          * Array of levels of atomicity within transactions
 179          *
 180          * @var array
 181          */
 182         private $mTrxAtomicLevels = [];
 183         /**
 184          * Record if the current transaction was started implicitly by Database::startAtomic
 185          *
 186          * @var bool
 187          */
 188         private $mTrxAutomaticAtomic = false;
 189         /**
 190          * Track the write query callers of the current transaction
 191          *
 192          * @var string[]
 193          */
 194         private $mTrxWriteCallers = [];
 195         /**
 196          * @var float Seconds spent in write queries for the current transaction
 197          */
 198         private $mTrxWriteDuration = 0.0;
 199         /**
 200          * @var int Number of write queries for the current transaction
 201          */
 202         private $mTrxWriteQueryCount = 0;
 203         /**
 204          * @var int Number of rows affected by write queries for the current transaction
 205          */
 206         private $mTrxWriteAffectedRows = 0;
 207         /**
 208          * @var float Like mTrxWriteQueryCount but excludes lock-bound, easy to replicate, queries
 209          */
 210         private $mTrxWriteAdjDuration = 0.0;
 211         /**
 212          * @var int Number of write queries counted in mTrxWriteAdjDuration
 213          */
 214         private $mTrxWriteAdjQueryCount = 0;
 215         /**
 216          * @var float RTT time estimate
 217          */
 218         private $mRTTEstimate = 0.0;
 219
 220         /** @var array Map of (name => 1) for locks obtained via lock() */
 221         private $mNamedLocksHeld = [];
 222         /** @var array Map of (table name => 1) for TEMPORARY tables */
 223         protected $mSessionTempTables = [];
 224
 225         /** @var IDatabase|null Lazy handle to the master DB this server replicates from */
 226         private $lazyMasterHandle;
 227
 228         /** @var float UNIX timestamp */
 229         protected $lastPing = 0.0;
 230
 231         /** @var int[] Prior mFlags values */
 232         private $priorFlags = [];
 233
 234         /** @var object|string Class name or object With profileIn/profileOut methods */
 235         protected $profiler;
 236         /** @var TransactionProfiler */
 237         protected $trxProfiler;
 238
 239         /**
 240          * @var bool Whether writing is allowed on this connection.
 241          *      Should be false for connections to replicas.
 242          */
 243         protected $allowWrite = true;
 244
 245         /**
 246          * Constructor and database handle and attempt to connect to the DB server
 247          *
 248          * IDatabase classes should not be constructed directly in external
 249          * code. Database::factory() should be used instead.
 250          *
 251          * @param array $params Parameters passed from Database::factory()
 252          */
 253         function __construct( array $params ) {
 254                 $server = $params['host'];
 255                 $user = $params['user'];
 256                 $password = $params['password'];
 257                 $dbName = $params['dbname'];
 258
 259                 $this->mSchema = $params['schema'];
 260                 $this->mTablePrefix = $params['tablePrefix'];
 261
 262                 $this->cliMode = $params['cliMode'];
 263                 // Agent name is added to SQL queries in a comment, so make sure it can't break out
 264                 $this->agent = str_replace( '/', '-', $params['agent'] );
 265
 266                 $this->mFlags = $params['flags'];
 267                 if ( $this->mFlags & self::DBO_DEFAULT ) {
 268                         if ( $this->cliMode ) {
 269                                 $this->mFlags &= ~self::DBO_TRX;
 270                         } else {
 271                                 $this->mFlags |= self::DBO_TRX;
 272                         }
 273                 }
 274
 275                 $this->mSessionVars = $params['variables'];
 276
 277                 $this->srvCache = isset( $params['srvCache'] )
 278                         ? $params['srvCache']
 279                         : new HashBagOStuff();
 280
 281                 $this->profiler = $params['profiler'];
 282                 $this->trxProfiler = $params['trxProfiler'];
 283                 $this->connLogger = $params['connLogger'];
 284                 $this->queryLogger = $params['queryLogger'];
 285                 $this->errorLogger = $params['errorLogger'];
 286                 $this->allowWrite = empty( $params['noWrite'] );
 287
 288                 // Set initial dummy domain until open() sets the final DB/prefix
 289                 $this->currentDomain = DatabaseDomain::newUnspecified();
 290
 291                 if ( $user ) {
 292                         $this->open( $server, $user, $password, $dbName );
 293                 } elseif ( $this->requiresDatabaseUser() ) {
 294                         throw new InvalidArgumentException( "No database user provided." );
 295                 }
 296
 297                 // Set the domain object after open() sets the relevant fields
 298                 if ( $this->mDBname != '' ) {
 299                         // Domains with server scope but a table prefix are not used by IDatabase classes
 300                         $this->currentDomain = new DatabaseDomain( $this->mDBname, null, $this->mTablePrefix );
 301                 }
 302         }
 303
 304         /**
 305          * Construct a Database subclass instance given a database type and parameters
 306          *
 307          * This also connects to the database immediately upon object construction
 308          *
 309          * @param string $dbType A possible DB type (sqlite, mysql, postgres)
 310          * @param array $p Parameter map with keys:
 311          *   - host : The hostname of the DB server
 312          *   - user : The name of the database user the client operates under
 313          *   - password : The password for the database user
 314          *   - dbname : The name of the database to use where queries do not specify one.
 315          *      The database must exist or an error might be thrown. Setting this to the empty string
 316          *      will avoid any such errors and make the handle have no implicit database scope. This is
 317          *      useful for queries like SHOW STATUS, CREATE DATABASE, or DROP DATABASE. Note that a
 318          *      "database" in Postgres is rougly equivalent to an entire MySQL server. This the domain
 319          *      in which user names and such are defined, e.g. users are database-specific in Postgres.
 320          *   - schema : The database schema to use (if supported). A "schema" in Postgres is roughly
 321          *      equivalent to a "database" in MySQL. Note that MySQL and SQLite do not use schemas.
 322          *   - tablePrefix : Optional table prefix that is implicitly added on to all table names
 323          *      recognized in queries. This can be used in place of schemas for handle site farms.
 324          *   - flags : Optional bitfield of DBO_* constants that define connection, protocol,
 325          *      buffering, and transaction behavior. It is STRONGLY adviced to leave the DBO_DEFAULT
 326          *      flag in place UNLESS this this database simply acts as a key/value store.
 327          *   - driver: Optional name of a specific DB client driver. For MySQL, there is the old
 328          *      'mysql' driver and the newer 'mysqli' driver.
 329          *   - variables: Optional map of session variables to set after connecting. This can be
 330          *      used to adjust lock timeouts or encoding modes and the like.
 331          *   - connLogger: Optional PSR-3 logger interface instance.
 332          *   - queryLogger: Optional PSR-3 logger interface instance.
 333          *   - profiler: Optional class name or object with profileIn()/profileOut() methods.
 334          *      These will be called in query(), using a simplified version of the SQL that also
 335          *      includes the agent as a SQL comment.
 336          *   - trxProfiler: Optional TransactionProfiler instance.
 337          *   - errorLogger: Optional callback that takes an Exception and logs it.
 338          *   - cliMode: Whether to consider the execution context that of a CLI script.
 339          *   - agent: Optional name used to identify the end-user in query profiling/logging.
 340          *   - srvCache: Optional BagOStuff instance to an APC-style cache.
 341          * @return Database|null If the database driver or extension cannot be found
 342          * @throws InvalidArgumentException If the database driver or extension cannot be found
 343          * @since 1.18
 344          */
 345         final public static function factory( $dbType, $p = [] ) {
 346                 static $canonicalDBTypes = [
 347                         'mysql' => [ 'mysqli', 'mysql' ],
 348                         'postgres' => [],
 349                         'sqlite' => [],
 350                         'oracle' => [],
 351                         'mssql' => [],
 352                 ];
 353                 static $classAliases = [
 354                         'DatabaseMssql' => DatabaseMssql::class,
 355                         'DatabaseMysql' => DatabaseMysql::class,
 356                         'DatabaseMysqli' => DatabaseMysqli::class,
 357                         'DatabaseSqlite' => DatabaseSqlite::class,
 358                         'DatabasePostgres' => DatabasePostgres::class
 359                 ];
 360
 361                 $driver = false;
 362                 $dbType = strtolower( $dbType );
 363                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 364                         $possibleDrivers = $canonicalDBTypes[$dbType];
 365                         if ( !empty( $p['driver'] ) ) {
 366                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 367                                         $driver = $p['driver'];
 368                                 } else {
 369                                         throw new InvalidArgumentException( __METHOD__ .
 370                                                 " type '$dbType' does not support driver '{$p['driver']}'" );
 371                                 }
 372                         } else {
 373                                 foreach ( $possibleDrivers as $posDriver ) {
 374                                         if ( extension_loaded( $posDriver ) ) {
 375                                                 $driver = $posDriver;
 376                                                 break;
 377                                         }
 378                                 }
 379                         }
 380                 } else {
 381                         $driver = $dbType;
 382                 }
 383
 384                 if ( $driver === false || $driver === '' ) {
 385                         throw new InvalidArgumentException( __METHOD__ .
 386                                 " no viable database extension found for type '$dbType'" );
 387                 }
 388
 389                 $class = 'Database' . ucfirst( $driver );
 390                 if ( isset( $classAliases[$class] ) ) {
 391                         $class = $classAliases[$class];
 392                 }
 393
 394                 if ( class_exists( $class ) && is_subclass_of( $class, IDatabase::class ) ) {
 395                         // Resolve some defaults for b/c
 396                         $p['host'] = isset( $p['host'] ) ? $p['host'] : false;
 397                         $p['user'] = isset( $p['user'] ) ? $p['user'] : false;
 398                         $p['password'] = isset( $p['password'] ) ? $p['password'] : false;
 399                         $p['dbname'] = isset( $p['dbname'] ) ? $p['dbname'] : false;
 400                         $p['flags'] = isset( $p['flags'] ) ? $p['flags'] : 0;
 401                         $p['variables'] = isset( $p['variables'] ) ? $p['variables'] : [];
 402                         $p['tablePrefix'] = isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : '';
 403                         $p['schema'] = isset( $p['schema'] ) ? $p['schema'] : '';
 404                         $p['cliMode'] = isset( $p['cliMode'] ) ? $p['cliMode'] : ( PHP_SAPI === 'cli' );
 405                         $p['agent'] = isset( $p['agent'] ) ? $p['agent'] : '';
 406                         if ( !isset( $p['connLogger'] ) ) {
 407                                 $p['connLogger'] = new \Psr\Log\NullLogger();
 408                         }
 409                         if ( !isset( $p['queryLogger'] ) ) {
 410                                 $p['queryLogger'] = new \Psr\Log\NullLogger();
 411                         }
 412                         $p['profiler'] = isset( $p['profiler'] ) ? $p['profiler'] : null;
 413                         if ( !isset( $p['trxProfiler'] ) ) {
 414                                 $p['trxProfiler'] = new TransactionProfiler();
 415                         }
 416                         if ( !isset( $p['errorLogger'] ) ) {
 417                                 $p['errorLogger'] = function ( Exception $e ) {
 418                                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 419                                 };
 420                         }
 421
 422                         $conn = new $class( $p );
 423                 } else {
 424                         $conn = null;
 425                 }
 426
 427                 return $conn;
 428         }
 429
 430         /**
 431          * Set the PSR-3 logger interface to use for query logging. (The logger
 432          * interfaces for connection logging and error logging can be set with the
 433          * constructor.)
 434          *
 435          * @param LoggerInterface $logger
 436          */
 437         public function setLogger( LoggerInterface $logger ) {
 438                 $this->queryLogger = $logger;
 439         }
 440
 441         public function getServerInfo() {
 442                 return $this->getServerVersion();
 443         }
 444
 445         public function bufferResults( $buffer = null ) {
 446                 $res = !$this->getFlag( self::DBO_NOBUFFER );
 447                 if ( $buffer !== null ) {
 448                         $buffer
 449                                 ? $this->clearFlag( self::DBO_NOBUFFER )
 450                                 : $this->setFlag( self::DBO_NOBUFFER );
 451                 }
 452
 453                 return $res;
 454         }
 455
 456         /**
 457          * Turns on (false) or off (true) the automatic generation and sending
 458          * of a "we're sorry, but there has been a database error" page on
 459          * database errors. Default is on (false). When turned off, the
 460          * code should use lastErrno() and lastError() to handle the
 461          * situation as appropriate.
 462          *
 463          * Do not use this function outside of the Database classes.
 464          *
 465          * @param null|bool $ignoreErrors
 466          * @return bool The previous value of the flag.
 467          */
 468         protected function ignoreErrors( $ignoreErrors = null ) {
 469                 $res = $this->getFlag( self::DBO_IGNORE );
 470                 if ( $ignoreErrors !== null ) {
 471                         // setFlag()/clearFlag() do not allow DBO_IGNORE changes for sanity
 472                         if ( $ignoreErrors ) {
 473                                 $this->mFlags |= self::DBO_IGNORE;
 474                         } else {
 475                                 $this->mFlags &= ~self::DBO_IGNORE;
 476                         }
 477                 }
 478
 479                 return $res;
 480         }
 481
 482         public function trxLevel() {
 483                 return $this->mTrxLevel;
 484         }
 485
 486         public function trxTimestamp() {
 487                 return $this->mTrxLevel ? $this->mTrxTimestamp : null;
 488         }
 489
 490         public function tablePrefix( $prefix = null ) {
 491                 $old = $this->mTablePrefix;
 492                 if ( $prefix !== null ) {
 493                         $this->mTablePrefix = $prefix;
 494                         $this->currentDomain = ( $this->mDBname != '' )
 495                                 ? new DatabaseDomain( $this->mDBname, null, $this->mTablePrefix )
 496                                 : DatabaseDomain::newUnspecified();
 497                 }
 498
 499                 return $old;
 500         }
 501
 502         public function dbSchema( $schema = null ) {
 503                 $old = $this->mSchema;
 504                 if ( $schema !== null ) {
 505                         $this->mSchema = $schema;
 506                 }
 507
 508                 return $old;
 509         }
 510
 511         public function getLBInfo( $name = null ) {
 512                 if ( is_null( $name ) ) {
 513                         return $this->mLBInfo;
 514                 } else {
 515                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 516                                 return $this->mLBInfo[$name];
 517                         } else {
 518                                 return null;
 519                         }
 520                 }
 521         }
 522
 523         public function setLBInfo( $name, $value = null ) {
 524                 if ( is_null( $value ) ) {
 525                         $this->mLBInfo = $name;
 526                 } else {
 527                         $this->mLBInfo[$name] = $value;
 528                 }
 529         }
 530
 531         public function setLazyMasterHandle( IDatabase $conn ) {
 532                 $this->lazyMasterHandle = $conn;
 533         }
 534
 535         /**
 536          * @return IDatabase|null
 537          * @see setLazyMasterHandle()
 538          * @since 1.27
 539          */
 540         protected function getLazyMasterHandle() {
 541                 return $this->lazyMasterHandle;
 542         }
 543
 544         public function implicitGroupby() {
 545                 return true;
 546         }
 547
 548         public function implicitOrderby() {
 549                 return true;
 550         }
 551
 552         public function lastQuery() {
 553                 return $this->mLastQuery;
 554         }
 555
 556         public function doneWrites() {
 557                 return (bool)$this->mLastWriteTime;
 558         }
 559
 560         public function lastDoneWrites() {
 561                 return $this->mLastWriteTime ?: false;
 562         }
 563
 564         public function writesPending() {
 565                 return $this->mTrxLevel && $this->mTrxDoneWrites;
 566         }
 567
 568         public function writesOrCallbacksPending() {
 569                 return $this->mTrxLevel && (
 570                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 571                 );
 572         }
 573
 574         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 575                 if ( !$this->mTrxLevel ) {
 576                         return false;
 577                 } elseif ( !$this->mTrxDoneWrites ) {
 578                         return 0.0;
 579                 }
 580
 581                 switch ( $type ) {
 582                         case self::ESTIMATE_DB_APPLY:
 583                                 $this->ping( $rtt );
 584                                 $rttAdjTotal = $this->mTrxWriteAdjQueryCount * $rtt;
 585                                 $applyTime = max( $this->mTrxWriteAdjDuration - $rttAdjTotal, 0 );
 586                                 // For omitted queries, make them count as something at least
 587                                 $omitted = $this->mTrxWriteQueryCount - $this->mTrxWriteAdjQueryCount;
 588                                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 589
 590                                 return $applyTime;
 591                         default: // everything
 592                                 return $this->mTrxWriteDuration;
 593                 }
 594         }
 595
 596         public function pendingWriteCallers() {
 597                 return $this->mTrxLevel ? $this->mTrxWriteCallers : [];
 598         }
 599
 600         public function pendingWriteRowsAffected() {
 601                 return $this->mTrxWriteAffectedRows;
 602         }
 603
 604         /**
 605          * Get the list of method names that have pending write queries or callbacks
 606          * for this transaction
 607          *
 608          * @return array
 609          */
 610         protected function pendingWriteAndCallbackCallers() {
 611                 if ( !$this->mTrxLevel ) {
 612                         return [];
 613                 }
 614
 615                 $fnames = $this->mTrxWriteCallers;
 616                 foreach ( [
 617                         $this->mTrxIdleCallbacks,
 618                         $this->mTrxPreCommitCallbacks,
 619                         $this->mTrxEndCallbacks
 620                 ] as $callbacks ) {
 621                         foreach ( $callbacks as $callback ) {
 622                                 $fnames[] = $callback[1];
 623                         }
 624                 }
 625
 626                 return $fnames;
 627         }
 628
 629         public function isOpen() {
 630                 return $this->mOpened;
 631         }
 632
 633         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 634                 if ( ( $flag & self::DBO_IGNORE ) ) {
 635                         throw new \UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 636                 }
 637
 638                 if ( $remember === self::REMEMBER_PRIOR ) {
 639                         array_push( $this->priorFlags, $this->mFlags );
 640                 }
 641                 $this->mFlags |= $flag;
 642         }
 643
 644         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 645                 if ( ( $flag & self::DBO_IGNORE ) ) {
 646                         throw new \UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 647                 }
 648
 649                 if ( $remember === self::REMEMBER_PRIOR ) {
 650                         array_push( $this->priorFlags, $this->mFlags );
 651                 }
 652                 $this->mFlags &= ~$flag;
 653         }
 654
 655         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 656                 if ( !$this->priorFlags ) {
 657                         return;
 658                 }
 659
 660                 if ( $state === self::RESTORE_INITIAL ) {
 661                         $this->mFlags = reset( $this->priorFlags );
 662                         $this->priorFlags = [];
 663                 } else {
 664                         $this->mFlags = array_pop( $this->priorFlags );
 665                 }
 666         }
 667
 668         public function getFlag( $flag ) {
 669                 return !!( $this->mFlags & $flag );
 670         }
 671
 672         /**
 673          * @param string $name Class field name
 674          * @return mixed
 675          * @deprecated Since 1.28
 676          */
 677         public function getProperty( $name ) {
 678                 return $this->$name;
 679         }
 680
 681         public function getDomainID() {
 682                 return $this->currentDomain->getId();
 683         }
 684
 685         final public function getWikiID() {
 686                 return $this->getDomainID();
 687         }
 688
 689         /**
 690          * Get information about an index into an object
 691          * @param string $table Table name
 692          * @param string $index Index name
 693          * @param string $fname Calling function name
 694          * @return mixed Database-specific index description class or false if the index does not exist
 695          */
 696         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 697
 698         /**
 699          * Wrapper for addslashes()
 700          *
 701          * @param string $s String to be slashed.
 702          * @return string Slashed string.
 703          */
 704         abstract function strencode( $s );
 705
 706         /**
 707          * Set a custom error handler for logging errors during database connection
 708          */
 709         protected function installErrorHandler() {
 710                 $this->mPHPError = false;
 711                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 712                 set_error_handler( [ $this, 'connectionErrorLogger' ] );
 713         }
 714
 715         /**
 716          * Restore the previous error handler and return the last PHP error for this DB
 717          *
 718          * @return bool|string
 719          */
 720         protected function restoreErrorHandler() {
 721                 restore_error_handler();
 722                 if ( $this->htmlErrors !== false ) {
 723                         ini_set( 'html_errors', $this->htmlErrors );
 724                 }
 725
 726                 return $this->getLastPHPError();
 727         }
 728
 729         /**
 730          * @return string|bool Last PHP error for this DB (typically connection errors)
 731          */
 732         protected function getLastPHPError() {
 733                 if ( $this->mPHPError ) {
 734                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 735                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 736
 737                         return $error;
 738                 }
 739
 740                 return false;
 741         }
 742
 743         /**
 744          * Error handler for logging errors during database connection
 745          * This method should not be used outside of Database classes
 746          *
 747          * @param int $errno
 748          * @param string $errstr
 749          */
 750         public function connectionErrorLogger( $errno, $errstr ) {
 751                 $this->mPHPError = $errstr;
 752         }
 753
 754         /**
 755          * Create a log context to pass to PSR-3 logger functions.
 756          *
 757          * @param array $extras Additional data to add to context
 758          * @return array
 759          */
 760         protected function getLogContext( array $extras = [] ) {
 761                 return array_merge(
 762                         [
 763                                 'db_server' => $this->mServer,
 764                                 'db_name' => $this->mDBname,
 765                                 'db_user' => $this->mUser,
 766                         ],
 767                         $extras
 768                 );
 769         }
 770
 771         public function close() {
 772                 if ( $this->mConn ) {
 773                         if ( $this->trxLevel() ) {
 774                                 $this->commit( __METHOD__, self::FLUSHING_INTERNAL );
 775                         }
 776
 777                         $closed = $this->closeConnection();
 778                         $this->mConn = false;
 779                 } elseif (
 780                         $this->mTrxIdleCallbacks ||
 781                         $this->mTrxPreCommitCallbacks ||
 782                         $this->mTrxEndCallbacks
 783                 ) { // sanity
 784                         throw new RuntimeException( "Transaction callbacks still pending." );
 785                 } else {
 786                         $closed = true;
 787                 }
 788                 $this->mOpened = false;
 789
 790                 return $closed;
 791         }
 792
 793         /**
 794          * Make sure isOpen() returns true as a sanity check
 795          *
 796          * @throws DBUnexpectedError
 797          */
 798         protected function assertOpen() {
 799                 if ( !$this->isOpen() ) {
 800                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
 801                 }
 802         }
 803
 804         /**
 805          * Closes underlying database connection
 806          * @since 1.20
 807          * @return bool Whether connection was closed successfully
 808          */
 809         abstract protected function closeConnection();
 810
 811         public function reportConnectionError( $error = 'Unknown error' ) {
 812                 $myError = $this->lastError();
 813                 if ( $myError ) {
 814                         $error = $myError;
 815                 }
 816
 817                 # New method
 818                 throw new DBConnectionError( $this, $error );
 819         }
 820
 821         /**
 822          * The DBMS-dependent part of query()
 823          *
 824          * @param string $sql SQL query.
 825          * @return ResultWrapper|bool Result object to feed to fetchObject,
 826          *   fetchRow, ...; or false on failure
 827          */
 828         abstract protected function doQuery( $sql );
 829
 830         /**
 831          * Determine whether a query writes to the DB.
 832          * Should return true if unsure.
 833          *
 834          * @param string $sql
 835          * @return bool
 836          */
 837         protected function isWriteQuery( $sql ) {
 838                 return !preg_match(
 839                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 840         }
 841
 842         /**
 843          * @param string $sql
 844          * @return string|null
 845          */
 846         protected function getQueryVerb( $sql ) {
 847                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
 848         }
 849
 850         /**
 851          * Determine whether a SQL statement is sensitive to isolation level.
 852          * A SQL statement is considered transactable if its result could vary
 853          * depending on the transaction isolation level. Operational commands
 854          * such as 'SET' and 'SHOW' are not considered to be transactable.
 855          *
 856          * @param string $sql
 857          * @return bool
 858          */
 859         protected function isTransactableQuery( $sql ) {
 860                 return !in_array(
 861                         $this->getQueryVerb( $sql ),
 862                         [ 'BEGIN', 'COMMIT', 'ROLLBACK', 'SHOW', 'SET', 'CREATE', 'ALTER' ],
 863                         true
 864                 );
 865         }
 866
 867         /**
 868          * @param string $sql A SQL query
 869          * @return bool Whether $sql is SQL for TEMPORARY table operation
 870          */
 871         protected function registerTempTableOperation( $sql ) {
 872                 if ( preg_match(
 873                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 874                         $sql,
 875                         $matches
 876                 ) ) {
 877                         $this->mSessionTempTables[$matches[1]] = 1;
 878
 879                         return true;
 880                 } elseif ( preg_match(
 881                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 882                         $sql,
 883                         $matches
 884                 ) ) {
 885                         $isTemp = isset( $this->mSessionTempTables[$matches[1]] );
 886                         unset( $this->mSessionTempTables[$matches[1]] );
 887
 888                         return $isTemp;
 889                 } elseif ( preg_match(
 890                         '/^TRUNCATE\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 891                         $sql,
 892                         $matches
 893                 ) ) {
 894                         return isset( $this->mSessionTempTables[$matches[1]] );
 895                 } elseif ( preg_match(
 896                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
 897                         $sql,
 898                         $matches
 899                 ) ) {
 900                         return isset( $this->mSessionTempTables[$matches[1]] );
 901                 }
 902
 903                 return false;
 904         }
 905
 906         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 907                 $priorWritesPending = $this->writesOrCallbacksPending();
 908                 $this->mLastQuery = $sql;
 909
 910                 $isWrite = $this->isWriteQuery( $sql );
 911                 if ( $isWrite ) {
 912                         $isNonTempWrite = !$this->registerTempTableOperation( $sql );
 913                 } else {
 914                         $isNonTempWrite = false;
 915                 }
 916
 917                 if ( $isWrite ) {
 918                         if ( !$this->allowWrite ) {
 919                                 throw new DBError(
 920                                         $this,
 921                                         'Write operations are not allowed on this database connection!'
 922                                 );
 923                         }
 924
 925                         # In theory, non-persistent writes are allowed in read-only mode, but due to things
 926                         # like https://bugs.mysql.com/bug.php?id=33669 that might not work anyway...
 927                         $reason = $this->getReadOnlyReason();
 928                         if ( $reason !== false ) {
 929                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
 930                         }
 931                         # Set a flag indicating that writes have been done
 932                         $this->mLastWriteTime = microtime( true );
 933                 }
 934
 935                 # Add trace comment to the begin of the sql string, right after the operator.
 936                 # Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598)
 937                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
 938
 939                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
 940                 if ( !$this->mTrxLevel && $this->getFlag( self::DBO_TRX )
 941                         && $this->isTransactableQuery( $sql )
 942                 ) {
 943                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
 944                         $this->mTrxAutomatic = true;
 945                 }
 946
 947                 # Keep track of whether the transaction has write queries pending
 948                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $isWrite ) {
 949                         $this->mTrxDoneWrites = true;
 950                         $this->trxProfiler->transactionWritingIn(
 951                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
 952                 }
 953
 954                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
 955                         $this->queryLogger->debug( "{$this->mDBname} {$commentedSql}" );
 956                 }
 957
 958                 # Avoid fatals if close() was called
 959                 $this->assertOpen();
 960
 961                 # Send the query to the server
 962                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
 963
 964                 # Try reconnecting if the connection was lost
 965                 if ( false === $ret && $this->wasErrorReissuable() ) {
 966                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
 967                         # Stash the last error values before anything might clear them
 968                         $lastError = $this->lastError();
 969                         $lastErrno = $this->lastErrno();
 970                         # Update state tracking to reflect transaction loss due to disconnection
 971                         $this->handleSessionLoss();
 972                         if ( $this->reconnect() ) {
 973                                 $msg = __METHOD__ . ': lost connection to {dbserver}; reconnected';
 974                                 $params = [ 'dbserver' => $this->getServer() ];
 975                                 $this->connLogger->warning( $msg, $params );
 976                                 $this->queryLogger->warning( $msg, $params +
 977                                         [ 'trace' => ( new RuntimeException() )->getTraceAsString() ] );
 978
 979                                 if ( !$recoverable ) {
 980                                         # Callers may catch the exception and continue to use the DB
 981                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname );
 982                                 } else {
 983                                         # Should be safe to silently retry the query
 984                                         $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
 985                                 }
 986                         } else {
 987                                 $msg = __METHOD__ . ': lost connection to {dbserver} permanently';
 988                                 $this->connLogger->error( $msg, [ 'dbserver' => $this->getServer() ] );
 989                         }
 990                 }
 991
 992                 if ( false === $ret ) {
 993                         # Deadlocks cause the entire transaction to abort, not just the statement.
 994                         # https://dev.mysql.com/doc/refman/5.7/en/innodb-error-handling.html
 995                         # https://www.postgresql.org/docs/9.1/static/explicit-locking.html
 996                         if ( $this->wasDeadlock() ) {
 997                                 if ( $this->explicitTrxActive() || $priorWritesPending ) {
 998                                         $tempIgnore = false; // not recoverable
 999                                 }
1000                                 # Update state tracking to reflect transaction loss
1001                                 $this->handleSessionLoss();
1002                         }
1003
1004                         $this->reportQueryError(
1005                                 $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1006                 }
1007
1008                 $res = $this->resultObject( $ret );
1009
1010                 return $res;
1011         }
1012
1013         /**
1014          * Helper method for query() that handles profiling and logging and sends
1015          * the query to doQuery()
1016          *
1017          * @param string $sql Original SQL query
1018          * @param string $commentedSql SQL query with debugging/trace comment
1019          * @param bool $isWrite Whether the query is a (non-temporary) write operation
1020          * @param string $fname Name of the calling function
1021          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
1022          *     object for a successful read query, or false on failure
1023          */
1024         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
1025                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1026                 # generalizeSQL() will probably cut down the query to reasonable
1027                 # logging size most of the time. The substr is really just a sanity check.
1028                 if ( $isMaster ) {
1029                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1030                 } else {
1031                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1032                 }
1033
1034                 # Include query transaction state
1035                 $queryProf .= $this->mTrxShortId ? " [TRX#{$this->mTrxShortId}]" : "";
1036
1037                 $startTime = microtime( true );
1038                 if ( $this->profiler ) {
1039                         call_user_func( [ $this->profiler, 'profileIn' ], $queryProf );
1040                 }
1041                 $ret = $this->doQuery( $commentedSql );
1042                 if ( $this->profiler ) {
1043                         call_user_func( [ $this->profiler, 'profileOut' ], $queryProf );
1044                 }
1045                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1046
1047                 unset( $queryProfSection ); // profile out (if set)
1048
1049                 if ( $ret !== false ) {
1050                         $this->lastPing = $startTime;
1051                         if ( $isWrite && $this->mTrxLevel ) {
1052                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1053                                 $this->mTrxWriteCallers[] = $fname;
1054                         }
1055                 }
1056
1057                 if ( $sql === self::PING_QUERY ) {
1058                         $this->mRTTEstimate = $queryRuntime;
1059                 }
1060
1061                 $this->trxProfiler->recordQueryCompletion(
1062                         $queryProf, $startTime, $isWrite, $this->affectedRows()
1063                 );
1064                 $this->queryLogger->debug( $sql, [
1065                         'method' => $fname,
1066                         'master' => $isMaster,
1067                         'runtime' => $queryRuntime,
1068                 ] );
1069
1070                 return $ret;
1071         }
1072
1073         /**
1074          * Update the estimated run-time of a query, not counting large row lock times
1075          *
1076          * LoadBalancer can be set to rollback transactions that will create huge replication
1077          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1078          * queries, like inserting a row can take a long time due to row locking. This method
1079          * uses some simple heuristics to discount those cases.
1080          *
1081          * @param string $sql A SQL write query
1082          * @param float $runtime Total runtime, including RTT
1083          * @param int $affected Affected row count
1084          */
1085         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1086                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1087                 $indicativeOfReplicaRuntime = true;
1088                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1089                         $verb = $this->getQueryVerb( $sql );
1090                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1091                         if ( $verb === 'INSERT' ) {
1092                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1093                         } elseif ( $verb === 'REPLACE' ) {
1094                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1095                         }
1096                 }
1097
1098                 $this->mTrxWriteDuration += $runtime;
1099                 $this->mTrxWriteQueryCount += 1;
1100                 $this->mTrxWriteAffectedRows += $affected;
1101                 if ( $indicativeOfReplicaRuntime ) {
1102                         $this->mTrxWriteAdjDuration += $runtime;
1103                         $this->mTrxWriteAdjQueryCount += 1;
1104                 }
1105         }
1106
1107         /**
1108          * Determine whether or not it is safe to retry queries after a database
1109          * connection is lost
1110          *
1111          * @param string $sql SQL query
1112          * @param bool $priorWritesPending Whether there is a transaction open with
1113          *     possible write queries or transaction pre-commit/idle callbacks
1114          *     waiting on it to finish.
1115          * @return bool True if it is safe to retry the query, false otherwise
1116          */
1117         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1118                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1119                 # Dropped connections also mean that named locks are automatically released.
1120                 # Only allow error suppression in autocommit mode or when the lost transaction
1121                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1122                 if ( $this->mNamedLocksHeld ) {
1123                         return false; // possible critical section violation
1124                 } elseif ( $sql === 'COMMIT' ) {
1125                         return !$priorWritesPending; // nothing written anyway? (T127428)
1126                 } elseif ( $sql === 'ROLLBACK' ) {
1127                         return true; // transaction lost...which is also what was requested :)
1128                 } elseif ( $this->explicitTrxActive() ) {
1129                         return false; // don't drop atomocity
1130                 } elseif ( $priorWritesPending ) {
1131                         return false; // prior writes lost from implicit transaction
1132                 }
1133
1134                 return true;
1135         }
1136
1137         /**
1138          * Clean things up after transaction loss due to disconnection
1139          *
1140          * @return null|Exception
1141          */
1142         private function handleSessionLoss() {
1143                 $this->mTrxLevel = 0;
1144                 $this->mTrxIdleCallbacks = []; // T67263
1145                 $this->mTrxPreCommitCallbacks = []; // T67263
1146                 $this->mSessionTempTables = [];
1147                 $this->mNamedLocksHeld = [];
1148                 try {
1149                         // Handle callbacks in mTrxEndCallbacks
1150                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1151                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1152                         return null;
1153                 } catch ( Exception $e ) {
1154                         // Already logged; move on...
1155                         return $e;
1156                 }
1157         }
1158
1159         /**
1160          * Checks whether the cause of the error is detected to be a timeout.
1161          *
1162          * It returns false by default, and not all engines support detecting this yet.
1163          * If this returns false, it will be treated as a generic query error.
1164          *
1165          * @param string $error Error text
1166          * @param int $errno Error number
1167          * @return bool
1168          */
1169         protected function wasQueryTimeout( $error, $errno ) {
1170                 return false;
1171         }
1172
1173         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1174                 if ( $this->ignoreErrors() || $tempIgnore ) {
1175                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1176                 } else {
1177                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1178                         $this->queryLogger->error(
1179                                 "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1180                                 $this->getLogContext( [
1181                                         'method' => __METHOD__,
1182                                         'errno' => $errno,
1183                                         'error' => $error,
1184                                         'sql1line' => $sql1line,
1185                                         'fname' => $fname,
1186                                 ] )
1187                         );
1188                         $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1189                         $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1190                         if ( $wasQueryTimeout ) {
1191                                 throw new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1192                         } else {
1193                                 throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1194                         }
1195                 }
1196         }
1197
1198         public function freeResult( $res ) {
1199         }
1200
1201         public function selectField(
1202                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1203         ) {
1204                 if ( $var === '*' ) { // sanity
1205                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1206                 }
1207
1208                 if ( !is_array( $options ) ) {
1209                         $options = [ $options ];
1210                 }
1211
1212                 $options['LIMIT'] = 1;
1213
1214                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1215                 if ( $res === false || !$this->numRows( $res ) ) {
1216                         return false;
1217                 }
1218
1219                 $row = $this->fetchRow( $res );
1220
1221                 if ( $row !== false ) {
1222                         return reset( $row );
1223                 } else {
1224                         return false;
1225                 }
1226         }
1227
1228         public function selectFieldValues(
1229                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1230         ) {
1231                 if ( $var === '*' ) { // sanity
1232                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1233                 } elseif ( !is_string( $var ) ) { // sanity
1234                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1235                 }
1236
1237                 if ( !is_array( $options ) ) {
1238                         $options = [ $options ];
1239                 }
1240
1241                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1242                 if ( $res === false ) {
1243                         return false;
1244                 }
1245
1246                 $values = [];
1247                 foreach ( $res as $row ) {
1248                         $values[] = $row->$var;
1249                 }
1250
1251                 return $values;
1252         }
1253
1254         /**
1255          * Returns an optional USE INDEX clause to go after the table, and a
1256          * string to go at the end of the query.
1257          *
1258          * @param array $options Associative array of options to be turned into
1259          *   an SQL query, valid keys are listed in the function.
1260          * @return array
1261          * @see Database::select()
1262          */
1263         protected function makeSelectOptions( $options ) {
1264                 $preLimitTail = $postLimitTail = '';
1265                 $startOpts = '';
1266
1267                 $noKeyOptions = [];
1268
1269                 foreach ( $options as $key => $option ) {
1270                         if ( is_numeric( $key ) ) {
1271                                 $noKeyOptions[$option] = true;
1272                         }
1273                 }
1274
1275                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1276
1277                 $preLimitTail .= $this->makeOrderBy( $options );
1278
1279                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1280                         $postLimitTail .= ' FOR UPDATE';
1281                 }
1282
1283                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1284                         $postLimitTail .= ' LOCK IN SHARE MODE';
1285                 }
1286
1287                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1288                         $startOpts .= 'DISTINCT';
1289                 }
1290
1291                 # Various MySQL extensions
1292                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1293                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1294                 }
1295
1296                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1297                         $startOpts .= ' HIGH_PRIORITY';
1298                 }
1299
1300                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1301                         $startOpts .= ' SQL_BIG_RESULT';
1302                 }
1303
1304                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1305                         $startOpts .= ' SQL_BUFFER_RESULT';
1306                 }
1307
1308                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1309                         $startOpts .= ' SQL_SMALL_RESULT';
1310                 }
1311
1312                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1313                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1314                 }
1315
1316                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1317                         $startOpts .= ' SQL_CACHE';
1318                 }
1319
1320                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1321                         $startOpts .= ' SQL_NO_CACHE';
1322                 }
1323
1324                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1325                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1326                 } else {
1327                         $useIndex = '';
1328                 }
1329                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1330                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1331                 } else {
1332                         $ignoreIndex = '';
1333                 }
1334
1335                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1336         }
1337
1338         /**
1339          * Returns an optional GROUP BY with an optional HAVING
1340          *
1341          * @param array $options Associative array of options
1342          * @return string
1343          * @see Database::select()
1344          * @since 1.21
1345          */
1346         protected function makeGroupByWithHaving( $options ) {
1347                 $sql = '';
1348                 if ( isset( $options['GROUP BY'] ) ) {
1349                         $gb = is_array( $options['GROUP BY'] )
1350                                 ? implode( ',', $options['GROUP BY'] )
1351                                 : $options['GROUP BY'];
1352                         $sql .= ' GROUP BY ' . $gb;
1353                 }
1354                 if ( isset( $options['HAVING'] ) ) {
1355                         $having = is_array( $options['HAVING'] )
1356                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1357                                 : $options['HAVING'];
1358                         $sql .= ' HAVING ' . $having;
1359                 }
1360
1361                 return $sql;
1362         }
1363
1364         /**
1365          * Returns an optional ORDER BY
1366          *
1367          * @param array $options Associative array of options
1368          * @return string
1369          * @see Database::select()
1370          * @since 1.21
1371          */
1372         protected function makeOrderBy( $options ) {
1373                 if ( isset( $options['ORDER BY'] ) ) {
1374                         $ob = is_array( $options['ORDER BY'] )
1375                                 ? implode( ',', $options['ORDER BY'] )
1376                                 : $options['ORDER BY'];
1377
1378                         return ' ORDER BY ' . $ob;
1379                 }
1380
1381                 return '';
1382         }
1383
1384         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1385                 $options = [], $join_conds = [] ) {
1386                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1387
1388                 return $this->query( $sql, $fname );
1389         }
1390
1391         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1392                 $options = [], $join_conds = []
1393         ) {
1394                 if ( is_array( $vars ) ) {
1395                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1396                 }
1397
1398                 $options = (array)$options;
1399                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1400                         ? $options['USE INDEX']
1401                         : [];
1402                 $ignoreIndexes = (
1403                         isset( $options['IGNORE INDEX'] ) &&
1404                         is_array( $options['IGNORE INDEX'] )
1405                 )
1406                         ? $options['IGNORE INDEX']
1407                         : [];
1408
1409                 if ( is_array( $table ) ) {
1410                         $from = ' FROM ' .
1411                                 $this->tableNamesWithIndexClauseOrJOIN(
1412                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1413                 } elseif ( $table != '' ) {
1414                         if ( $table[0] == ' ' ) {
1415                                 $from = ' FROM ' . $table;
1416                         } else {
1417                                 $from = ' FROM ' .
1418                                         $this->tableNamesWithIndexClauseOrJOIN(
1419                                                 [ $table ], $useIndexes, $ignoreIndexes, [] );
1420                         }
1421                 } else {
1422                         $from = '';
1423                 }
1424
1425                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1426                         $this->makeSelectOptions( $options );
1427
1428                 if ( !empty( $conds ) ) {
1429                         if ( is_array( $conds ) ) {
1430                                 $conds = $this->makeList( $conds, self::LIST_AND );
1431                         }
1432                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex " .
1433                                 "WHERE $conds $preLimitTail";
1434                 } else {
1435                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex $preLimitTail";
1436                 }
1437
1438                 if ( isset( $options['LIMIT'] ) ) {
1439                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1440                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1441                 }
1442                 $sql = "$sql $postLimitTail";
1443
1444                 if ( isset( $options['EXPLAIN'] ) ) {
1445                         $sql = 'EXPLAIN ' . $sql;
1446                 }
1447
1448                 return $sql;
1449         }
1450
1451         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1452                 $options = [], $join_conds = []
1453         ) {
1454                 $options = (array)$options;
1455                 $options['LIMIT'] = 1;
1456                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1457
1458                 if ( $res === false ) {
1459                         return false;
1460                 }
1461
1462                 if ( !$this->numRows( $res ) ) {
1463                         return false;
1464                 }
1465
1466                 $obj = $this->fetchObject( $res );
1467
1468                 return $obj;
1469         }
1470
1471         public function estimateRowCount(
1472                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
1473         ) {
1474                 $rows = 0;
1475                 $res = $this->select( $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options );
1476
1477                 if ( $res ) {
1478                         $row = $this->fetchRow( $res );
1479                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1480                 }
1481
1482                 return $rows;
1483         }
1484
1485         public function selectRowCount(
1486                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1487         ) {
1488                 $rows = 0;
1489                 $sql = $this->selectSQLText( $tables, '1', $conds, $fname, $options, $join_conds );
1490                 // The identifier quotes is primarily for MSSQL.
1491                 $rowCountCol = $this->addIdentifierQuotes( "rowcount" );
1492                 $tableName = $this->addIdentifierQuotes( "tmp_count" );
1493                 $res = $this->query( "SELECT COUNT(*) AS $rowCountCol FROM ($sql) $tableName", $fname );
1494
1495                 if ( $res ) {
1496                         $row = $this->fetchRow( $res );
1497                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1498                 }
1499
1500                 return $rows;
1501         }
1502
1503         /**
1504          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1505          * It's only slightly flawed. Don't use for anything important.
1506          *
1507          * @param string $sql A SQL Query
1508          *
1509          * @return string
1510          */
1511         protected static function generalizeSQL( $sql ) {
1512                 # This does the same as the regexp below would do, but in such a way
1513                 # as to avoid crashing php on some large strings.
1514                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1515
1516                 $sql = str_replace( "\\\\", '', $sql );
1517                 $sql = str_replace( "\\'", '', $sql );
1518                 $sql = str_replace( "\\\"", '', $sql );
1519                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1520                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1521
1522                 # All newlines, tabs, etc replaced by single space
1523                 $sql = preg_replace( '/\s+/', ' ', $sql );
1524
1525                 # All numbers => N,
1526                 # except the ones surrounded by characters, e.g. l10n
1527                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1528                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1529
1530                 return $sql;
1531         }
1532
1533         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1534                 $info = $this->fieldInfo( $table, $field );
1535
1536                 return (bool)$info;
1537         }
1538
1539         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1540                 if ( !$this->tableExists( $table ) ) {
1541                         return null;
1542                 }
1543
1544                 $info = $this->indexInfo( $table, $index, $fname );
1545                 if ( is_null( $info ) ) {
1546                         return null;
1547                 } else {
1548                         return $info !== false;
1549                 }
1550         }
1551
1552         public function tableExists( $table, $fname = __METHOD__ ) {
1553                 $tableRaw = $this->tableName( $table, 'raw' );
1554                 if ( isset( $this->mSessionTempTables[$tableRaw] ) ) {
1555                         return true; // already known to exist
1556                 }
1557
1558                 $table = $this->tableName( $table );
1559                 $ignoreErrors = true;
1560                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname, $ignoreErrors );
1561
1562                 return (bool)$res;
1563         }
1564
1565         public function indexUnique( $table, $index ) {
1566                 $indexInfo = $this->indexInfo( $table, $index );
1567
1568                 if ( !$indexInfo ) {
1569                         return null;
1570                 }
1571
1572                 return !$indexInfo[0]->Non_unique;
1573         }
1574
1575         /**
1576          * Helper for Database::insert().
1577          *
1578          * @param array $options
1579          * @return string
1580          */
1581         protected function makeInsertOptions( $options ) {
1582                 return implode( ' ', $options );
1583         }
1584
1585         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1586                 # No rows to insert, easy just return now
1587                 if ( !count( $a ) ) {
1588                         return true;
1589                 }
1590
1591                 $table = $this->tableName( $table );
1592
1593                 if ( !is_array( $options ) ) {
1594                         $options = [ $options ];
1595                 }
1596
1597                 $fh = null;
1598                 if ( isset( $options['fileHandle'] ) ) {
1599                         $fh = $options['fileHandle'];
1600                 }
1601                 $options = $this->makeInsertOptions( $options );
1602
1603                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1604                         $multi = true;
1605                         $keys = array_keys( $a[0] );
1606                 } else {
1607                         $multi = false;
1608                         $keys = array_keys( $a );
1609                 }
1610
1611                 $sql = 'INSERT ' . $options .
1612                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1613
1614                 if ( $multi ) {
1615                         $first = true;
1616                         foreach ( $a as $row ) {
1617                                 if ( $first ) {
1618                                         $first = false;
1619                                 } else {
1620                                         $sql .= ',';
1621                                 }
1622                                 $sql .= '(' . $this->makeList( $row ) . ')';
1623                         }
1624                 } else {
1625                         $sql .= '(' . $this->makeList( $a ) . ')';
1626                 }
1627
1628                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1629                         return false;
1630                 } elseif ( $fh !== null ) {
1631                         return true;
1632                 }
1633
1634                 return (bool)$this->query( $sql, $fname );
1635         }
1636
1637         /**
1638          * Make UPDATE options array for Database::makeUpdateOptions
1639          *
1640          * @param array $options
1641          * @return array
1642          */
1643         protected function makeUpdateOptionsArray( $options ) {
1644                 if ( !is_array( $options ) ) {
1645                         $options = [ $options ];
1646                 }
1647
1648                 $opts = [];
1649
1650                 if ( in_array( 'IGNORE', $options ) ) {
1651                         $opts[] = 'IGNORE';
1652                 }
1653
1654                 return $opts;
1655         }
1656
1657         /**
1658          * Make UPDATE options for the Database::update function
1659          *
1660          * @param array $options The options passed to Database::update
1661          * @return string
1662          */
1663         protected function makeUpdateOptions( $options ) {
1664                 $opts = $this->makeUpdateOptionsArray( $options );
1665
1666                 return implode( ' ', $opts );
1667         }
1668
1669         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1670                 $table = $this->tableName( $table );
1671                 $opts = $this->makeUpdateOptions( $options );
1672                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
1673
1674                 if ( $conds !== [] && $conds !== '*' ) {
1675                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
1676                 }
1677
1678                 return (bool)$this->query( $sql, $fname );
1679         }
1680
1681         public function makeList( $a, $mode = self::LIST_COMMA ) {
1682                 if ( !is_array( $a ) ) {
1683                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1684                 }
1685
1686                 $first = true;
1687                 $list = '';
1688
1689                 foreach ( $a as $field => $value ) {
1690                         if ( !$first ) {
1691                                 if ( $mode == self::LIST_AND ) {
1692                                         $list .= ' AND ';
1693                                 } elseif ( $mode == self::LIST_OR ) {
1694                                         $list .= ' OR ';
1695                                 } else {
1696                                         $list .= ',';
1697                                 }
1698                         } else {
1699                                 $first = false;
1700                         }
1701
1702                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
1703                                 $list .= "($value)";
1704                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
1705                                 $list .= "$value";
1706                         } elseif (
1707                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
1708                         ) {
1709                                 // Remove null from array to be handled separately if found
1710                                 $includeNull = false;
1711                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
1712                                         $includeNull = true;
1713                                         unset( $value[$nullKey] );
1714                                 }
1715                                 if ( count( $value ) == 0 && !$includeNull ) {
1716                                         throw new InvalidArgumentException(
1717                                                 __METHOD__ . ": empty input for field $field" );
1718                                 } elseif ( count( $value ) == 0 ) {
1719                                         // only check if $field is null
1720                                         $list .= "$field IS NULL";
1721                                 } else {
1722                                         // IN clause contains at least one valid element
1723                                         if ( $includeNull ) {
1724                                                 // Group subconditions to ensure correct precedence
1725                                                 $list .= '(';
1726                                         }
1727                                         if ( count( $value ) == 1 ) {
1728                                                 // Special-case single values, as IN isn't terribly efficient
1729                                                 // Don't necessarily assume the single key is 0; we don't
1730                                                 // enforce linear numeric ordering on other arrays here.
1731                                                 $value = array_values( $value )[0];
1732                                                 $list .= $field . " = " . $this->addQuotes( $value );
1733                                         } else {
1734                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1735                                         }
1736                                         // if null present in array, append IS NULL
1737                                         if ( $includeNull ) {
1738                                                 $list .= " OR $field IS NULL)";
1739                                         }
1740                                 }
1741                         } elseif ( $value === null ) {
1742                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
1743                                         $list .= "$field IS ";
1744                                 } elseif ( $mode == self::LIST_SET ) {
1745                                         $list .= "$field = ";
1746                                 }
1747                                 $list .= 'NULL';
1748                         } else {
1749                                 if (
1750                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
1751                                 ) {
1752                                         $list .= "$field = ";
1753                                 }
1754                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
1755                         }
1756                 }
1757
1758                 return $list;
1759         }
1760
1761         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1762                 $conds = [];
1763
1764                 foreach ( $data as $base => $sub ) {
1765                         if ( count( $sub ) ) {
1766                                 $conds[] = $this->makeList(
1767                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
1768                                         self::LIST_AND );
1769                         }
1770                 }
1771
1772                 if ( $conds ) {
1773                         return $this->makeList( $conds, self::LIST_OR );
1774                 } else {
1775                         // Nothing to search for...
1776                         return false;
1777                 }
1778         }
1779
1780         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1781                 return $valuename;
1782         }
1783
1784         public function bitNot( $field ) {
1785                 return "(~$field)";
1786         }
1787
1788         public function bitAnd( $fieldLeft, $fieldRight ) {
1789                 return "($fieldLeft & $fieldRight)";
1790         }
1791
1792         public function bitOr( $fieldLeft, $fieldRight ) {
1793                 return "($fieldLeft | $fieldRight)";
1794         }
1795
1796         public function buildConcat( $stringList ) {
1797                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1798         }
1799
1800         public function buildGroupConcatField(
1801                 $delim, $table, $field, $conds = '', $join_conds = []
1802         ) {
1803                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
1804
1805                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
1806         }
1807
1808         public function buildStringCast( $field ) {
1809                 return $field;
1810         }
1811
1812         public function databasesAreIndependent() {
1813                 return false;
1814         }
1815
1816         public function selectDB( $db ) {
1817                 # Stub. Shouldn't cause serious problems if it's not overridden, but
1818                 # if your database engine supports a concept similar to MySQL's
1819                 # databases you may as well.
1820                 $this->mDBname = $db;
1821
1822                 return true;
1823         }
1824
1825         public function getDBname() {
1826                 return $this->mDBname;
1827         }
1828
1829         public function getServer() {
1830                 return $this->mServer;
1831         }
1832
1833         public function tableName( $name, $format = 'quoted' ) {
1834                 # Skip the entire process when we have a string quoted on both ends.
1835                 # Note that we check the end so that we will still quote any use of
1836                 # use of `database`.table. But won't break things if someone wants
1837                 # to query a database table with a dot in the name.
1838                 if ( $this->isQuotedIdentifier( $name ) ) {
1839                         return $name;
1840                 }
1841
1842                 # Lets test for any bits of text that should never show up in a table
1843                 # name. Basically anything like JOIN or ON which are actually part of
1844                 # SQL queries, but may end up inside of the table value to combine
1845                 # sql. Such as how the API is doing.
1846                 # Note that we use a whitespace test rather than a \b test to avoid
1847                 # any remote case where a word like on may be inside of a table name
1848                 # surrounded by symbols which may be considered word breaks.
1849                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1850                         return $name;
1851                 }
1852
1853                 # Split database and table into proper variables.
1854                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
1855
1856                 # Quote $table and apply the prefix if not quoted.
1857                 # $tableName might be empty if this is called from Database::replaceVars()
1858                 $tableName = "{$prefix}{$table}";
1859                 if ( $format === 'quoted'
1860                         && !$this->isQuotedIdentifier( $tableName )
1861                         && $tableName !== ''
1862                 ) {
1863                         $tableName = $this->addIdentifierQuotes( $tableName );
1864                 }
1865
1866                 # Quote $schema and $database and merge them with the table name if needed
1867                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
1868                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
1869
1870                 return $tableName;
1871         }
1872
1873         /**
1874          * Get the table components needed for a query given the currently selected database
1875          *
1876          * @param string $name Table name in the form of db.schema.table, db.table, or table
1877          * @return array (DB name or "" for default, schema name, table prefix, table name)
1878          */
1879         protected function qualifiedTableComponents( $name ) {
1880                 # We reverse the explode so that database.table and table both output the correct table.
1881                 $dbDetails = explode( '.', $name, 3 );
1882                 if ( count( $dbDetails ) == 3 ) {
1883                         list( $database, $schema, $table ) = $dbDetails;
1884                         # We don't want any prefix added in this case
1885                         $prefix = '';
1886                 } elseif ( count( $dbDetails ) == 2 ) {
1887                         list( $database, $table ) = $dbDetails;
1888                         # We don't want any prefix added in this case
1889                         $prefix = '';
1890                         # In dbs that support it, $database may actually be the schema
1891                         # but that doesn't affect any of the functionality here
1892                         $schema = '';
1893                 } else {
1894                         list( $table ) = $dbDetails;
1895                         if ( isset( $this->tableAliases[$table] ) ) {
1896                                 $database = $this->tableAliases[$table]['dbname'];
1897                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
1898                                         ? $this->tableAliases[$table]['schema']
1899                                         : $this->mSchema;
1900                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
1901                                         ? $this->tableAliases[$table]['prefix']
1902                                         : $this->mTablePrefix;
1903                         } else {
1904                                 $database = '';
1905                                 $schema = $this->mSchema; # Default schema
1906                                 $prefix = $this->mTablePrefix; # Default prefix
1907                         }
1908                 }
1909
1910                 return [ $database, $schema, $prefix, $table ];
1911         }
1912
1913         /**
1914          * @param string|null $namespace Database or schema
1915          * @param string $relation Name of table, view, sequence, etc...
1916          * @param string $format One of (raw, quoted)
1917          * @return string Relation name with quoted and merged $namespace as needed
1918          */
1919         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
1920                 if ( strlen( $namespace ) ) {
1921                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
1922                                 $namespace = $this->addIdentifierQuotes( $namespace );
1923                         }
1924                         $relation = $namespace . '.' . $relation;
1925                 }
1926
1927                 return $relation;
1928         }
1929
1930         public function tableNames() {
1931                 $inArray = func_get_args();
1932                 $retVal = [];
1933
1934                 foreach ( $inArray as $name ) {
1935                         $retVal[$name] = $this->tableName( $name );
1936                 }
1937
1938                 return $retVal;
1939         }
1940
1941         public function tableNamesN() {
1942                 $inArray = func_get_args();
1943                 $retVal = [];
1944
1945                 foreach ( $inArray as $name ) {
1946                         $retVal[] = $this->tableName( $name );
1947                 }
1948
1949                 return $retVal;
1950         }
1951
1952         /**
1953          * Get an aliased table name
1954          * e.g. tableName AS newTableName
1955          *
1956          * @param string $name Table name, see tableName()
1957          * @param string|bool $alias Alias (optional)
1958          * @return string SQL name for aliased table. Will not alias a table to its own name
1959          */
1960         protected function tableNameWithAlias( $name, $alias = false ) {
1961                 if ( !$alias || $alias == $name ) {
1962                         return $this->tableName( $name );
1963                 } else {
1964                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
1965                 }
1966         }
1967
1968         /**
1969          * Gets an array of aliased table names
1970          *
1971          * @param array $tables [ [alias] => table ]
1972          * @return string[] See tableNameWithAlias()
1973          */
1974         protected function tableNamesWithAlias( $tables ) {
1975                 $retval = [];
1976                 foreach ( $tables as $alias => $table ) {
1977                         if ( is_numeric( $alias ) ) {
1978                                 $alias = $table;
1979                         }
1980                         $retval[] = $this->tableNameWithAlias( $table, $alias );
1981                 }
1982
1983                 return $retval;
1984         }
1985
1986         /**
1987          * Get an aliased field name
1988          * e.g. fieldName AS newFieldName
1989          *
1990          * @param string $name Field name
1991          * @param string|bool $alias Alias (optional)
1992          * @return string SQL name for aliased field. Will not alias a field to its own name
1993          */
1994         protected function fieldNameWithAlias( $name, $alias = false ) {
1995                 if ( !$alias || (string)$alias === (string)$name ) {
1996                         return $name;
1997                 } else {
1998                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
1999                 }
2000         }
2001
2002         /**
2003          * Gets an array of aliased field names
2004          *
2005          * @param array $fields [ [alias] => field ]
2006          * @return string[] See fieldNameWithAlias()
2007          */
2008         protected function fieldNamesWithAlias( $fields ) {
2009                 $retval = [];
2010                 foreach ( $fields as $alias => $field ) {
2011                         if ( is_numeric( $alias ) ) {
2012                                 $alias = $field;
2013                         }
2014                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2015                 }
2016
2017                 return $retval;
2018         }
2019
2020         /**
2021          * Get the aliased table name clause for a FROM clause
2022          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2023          *
2024          * @param array $tables ( [alias] => table )
2025          * @param array $use_index Same as for select()
2026          * @param array $ignore_index Same as for select()
2027          * @param array $join_conds Same as for select()
2028          * @return string
2029          */
2030         protected function tableNamesWithIndexClauseOrJOIN(
2031                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2032         ) {
2033                 $ret = [];
2034                 $retJOIN = [];
2035                 $use_index = (array)$use_index;
2036                 $ignore_index = (array)$ignore_index;
2037                 $join_conds = (array)$join_conds;
2038
2039                 foreach ( $tables as $alias => $table ) {
2040                         if ( !is_string( $alias ) ) {
2041                                 // No alias? Set it equal to the table name
2042                                 $alias = $table;
2043                         }
2044
2045                         if ( is_array( $table ) ) {
2046                                 // A parenthesized group
2047                                 if ( count( $table ) > 1 ) {
2048                                         $joinedTable = '('
2049                                                 . $this->tableNamesWithIndexClauseOrJOIN( $table, $use_index, $ignore_index, $join_conds )
2050                                                 . ')';
2051                                 } else {
2052                                         // Degenerate case
2053                                         $innerTable = reset( $table );
2054                                         $innerAlias = key( $table );
2055                                         $joinedTable = $this->tableNameWithAlias(
2056                                                 $innerTable,
2057                                                 is_string( $innerAlias ) ? $innerAlias : $innerTable
2058                                         );
2059                                 }
2060                         } else {
2061                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2062                         }
2063
2064                         // Is there a JOIN clause for this table?
2065                         if ( isset( $join_conds[$alias] ) ) {
2066                                 list( $joinType, $conds ) = $join_conds[$alias];
2067                                 $tableClause = $joinType;
2068                                 $tableClause .= ' ' . $joinedTable;
2069                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2070                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2071                                         if ( $use != '' ) {
2072                                                 $tableClause .= ' ' . $use;
2073                                         }
2074                                 }
2075                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2076                                         $ignore = $this->ignoreIndexClause(
2077                                                 implode( ',', (array)$ignore_index[$alias] ) );
2078                                         if ( $ignore != '' ) {
2079                                                 $tableClause .= ' ' . $ignore;
2080                                         }
2081                                 }
2082                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2083                                 if ( $on != '' ) {
2084                                         $tableClause .= ' ON (' . $on . ')';
2085                                 }
2086
2087                                 $retJOIN[] = $tableClause;
2088                         } elseif ( isset( $use_index[$alias] ) ) {
2089                                 // Is there an INDEX clause for this table?
2090                                 $tableClause = $joinedTable;
2091                                 $tableClause .= ' ' . $this->useIndexClause(
2092                                                 implode( ',', (array)$use_index[$alias] )
2093                                         );
2094
2095                                 $ret[] = $tableClause;
2096                         } elseif ( isset( $ignore_index[$alias] ) ) {
2097                                 // Is there an INDEX clause for this table?
2098                                 $tableClause = $joinedTable;
2099                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2100                                                 implode( ',', (array)$ignore_index[$alias] )
2101                                         );
2102
2103                                 $ret[] = $tableClause;
2104                         } else {
2105                                 $tableClause = $joinedTable;
2106
2107                                 $ret[] = $tableClause;
2108                         }
2109                 }
2110
2111                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2112                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2113                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2114
2115                 // Compile our final table clause
2116                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2117         }
2118
2119         /**
2120          * Allows for index remapping in queries where this is not consistent across DBMS
2121          *
2122          * @param string $index
2123          * @return string
2124          */
2125         protected function indexName( $index ) {
2126                 return $index;
2127         }
2128
2129         public function addQuotes( $s ) {
2130                 if ( $s instanceof Blob ) {
2131                         $s = $s->fetch();
2132                 }
2133                 if ( $s === null ) {
2134                         return 'NULL';
2135                 } elseif ( is_bool( $s ) ) {
2136                         return (int)$s;
2137                 } else {
2138                         # This will also quote numeric values. This should be harmless,
2139                         # and protects against weird problems that occur when they really
2140                         # _are_ strings such as article titles and string->number->string
2141                         # conversion is not 1:1.
2142                         return "'" . $this->strencode( $s ) . "'";
2143                 }
2144         }
2145
2146         /**
2147          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2148          * MySQL uses `backticks` while basically everything else uses double quotes.
2149          * Since MySQL is the odd one out here the double quotes are our generic
2150          * and we implement backticks in DatabaseMysqlBase.
2151          *
2152          * @param string $s
2153          * @return string
2154          */
2155         public function addIdentifierQuotes( $s ) {
2156                 return '"' . str_replace( '"', '""', $s ) . '"';
2157         }
2158
2159         /**
2160          * Returns if the given identifier looks quoted or not according to
2161          * the database convention for quoting identifiers .
2162          *
2163          * @note Do not use this to determine if untrusted input is safe.
2164          *   A malicious user can trick this function.
2165          * @param string $name
2166          * @return bool
2167          */
2168         public function isQuotedIdentifier( $name ) {
2169                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2170         }
2171
2172         /**
2173          * @param string $s
2174          * @param string $escapeChar
2175          * @return string
2176          */
2177         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2178                 return str_replace( [ $escapeChar, '%', '_' ],
2179                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2180                         $s );
2181         }
2182
2183         public function buildLike() {
2184                 $params = func_get_args();
2185
2186                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2187                         $params = $params[0];
2188                 }
2189
2190                 $s = '';
2191
2192                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2193                 // may escape backslashes, creating problems of double escaping. The `
2194                 // character has good cross-DBMS compatibility, avoiding special operators
2195                 // in MS SQL like ^ and %
2196                 $escapeChar = '`';
2197
2198                 foreach ( $params as $value ) {
2199                         if ( $value instanceof LikeMatch ) {
2200                                 $s .= $value->toString();
2201                         } else {
2202                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2203                         }
2204                 }
2205
2206                 return ' LIKE ' . $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2207         }
2208
2209         public function anyChar() {
2210                 return new LikeMatch( '_' );
2211         }
2212
2213         public function anyString() {
2214                 return new LikeMatch( '%' );
2215         }
2216
2217         public function nextSequenceValue( $seqName ) {
2218                 return null;
2219         }
2220
2221         /**
2222          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2223          * is only needed because a) MySQL must be as efficient as possible due to
2224          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2225          * which index to pick. Anyway, other databases might have different
2226          * indexes on a given table. So don't bother overriding this unless you're
2227          * MySQL.
2228          * @param string $index
2229          * @return string
2230          */
2231         public function useIndexClause( $index ) {
2232                 return '';
2233         }
2234
2235         /**
2236          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2237          * is only needed because a) MySQL must be as efficient as possible due to
2238          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2239          * which index to pick. Anyway, other databases might have different
2240          * indexes on a given table. So don't bother overriding this unless you're
2241          * MySQL.
2242          * @param string $index
2243          * @return string
2244          */
2245         public function ignoreIndexClause( $index ) {
2246                 return '';
2247         }
2248
2249         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2250                 $quotedTable = $this->tableName( $table );
2251
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                 // @FXIME: this is not atomic, but a trx would break affectedRows()
2262                 foreach ( $rows as $row ) {
2263                         # Delete rows which collide
2264                         if ( $uniqueIndexes ) {
2265                                 $sql = "DELETE FROM $quotedTable WHERE ";
2266                                 $first = true;
2267                                 foreach ( $uniqueIndexes as $index ) {
2268                                         if ( $first ) {
2269                                                 $first = false;
2270                                                 $sql .= '( ';
2271                                         } else {
2272                                                 $sql .= ' ) OR ( ';
2273                                         }
2274                                         if ( is_array( $index ) ) {
2275                                                 $first2 = true;
2276                                                 foreach ( $index as $col ) {
2277                                                         if ( $first2 ) {
2278                                                                 $first2 = false;
2279                                                         } else {
2280                                                                 $sql .= ' AND ';
2281                                                         }
2282                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2283                                                 }
2284                                         } else {
2285                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2286                                         }
2287                                 }
2288                                 $sql .= ' )';
2289                                 $this->query( $sql, $fname );
2290                         }
2291
2292                         # Now insert the row
2293                         $this->insert( $table, $row, $fname );
2294                 }
2295         }
2296
2297         /**
2298          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2299          * statement.
2300          *
2301          * @param string $table Table name
2302          * @param array|string $rows Row(s) to insert
2303          * @param string $fname Caller function name
2304          *
2305          * @return ResultWrapper
2306          */
2307         protected function nativeReplace( $table, $rows, $fname ) {
2308                 $table = $this->tableName( $table );
2309
2310                 # Single row case
2311                 if ( !is_array( reset( $rows ) ) ) {
2312                         $rows = [ $rows ];
2313                 }
2314
2315                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2316                 $first = true;
2317
2318                 foreach ( $rows as $row ) {
2319                         if ( $first ) {
2320                                 $first = false;
2321                         } else {
2322                                 $sql .= ',';
2323                         }
2324
2325                         $sql .= '(' . $this->makeList( $row ) . ')';
2326                 }
2327
2328                 return $this->query( $sql, $fname );
2329         }
2330
2331         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2332                 $fname = __METHOD__
2333         ) {
2334                 if ( !count( $rows ) ) {
2335                         return true; // nothing to do
2336                 }
2337
2338                 if ( !is_array( reset( $rows ) ) ) {
2339                         $rows = [ $rows ];
2340                 }
2341
2342                 if ( count( $uniqueIndexes ) ) {
2343                         $clauses = []; // list WHERE clauses that each identify a single row
2344                         foreach ( $rows as $row ) {
2345                                 foreach ( $uniqueIndexes as $index ) {
2346                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2347                                         $rowKey = []; // unique key to this row
2348                                         foreach ( $index as $column ) {
2349                                                 $rowKey[$column] = $row[$column];
2350                                         }
2351                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2352                                 }
2353                         }
2354                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2355                 } else {
2356                         $where = false;
2357                 }
2358
2359                 $useTrx = !$this->mTrxLevel;
2360                 if ( $useTrx ) {
2361                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2362                 }
2363                 try {
2364                         # Update any existing conflicting row(s)
2365                         if ( $where !== false ) {
2366                                 $ok = $this->update( $table, $set, $where, $fname );
2367                         } else {
2368                                 $ok = true;
2369                         }
2370                         # Now insert any non-conflicting row(s)
2371                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2372                 } catch ( Exception $e ) {
2373                         if ( $useTrx ) {
2374                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
2375                         }
2376                         throw $e;
2377                 }
2378                 if ( $useTrx ) {
2379                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2380                 }
2381
2382                 return $ok;
2383         }
2384
2385         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2386                 $fname = __METHOD__
2387         ) {
2388                 if ( !$conds ) {
2389                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2390                 }
2391
2392                 $delTable = $this->tableName( $delTable );
2393                 $joinTable = $this->tableName( $joinTable );
2394                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2395                 if ( $conds != '*' ) {
2396                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2397                 }
2398                 $sql .= ')';
2399
2400                 $this->query( $sql, $fname );
2401         }
2402
2403         public function textFieldSize( $table, $field ) {
2404                 $table = $this->tableName( $table );
2405                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2406                 $res = $this->query( $sql, __METHOD__ );
2407                 $row = $this->fetchObject( $res );
2408
2409                 $m = [];
2410
2411                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2412                         $size = $m[1];
2413                 } else {
2414                         $size = -1;
2415                 }
2416
2417                 return $size;
2418         }
2419
2420         public function delete( $table, $conds, $fname = __METHOD__ ) {
2421                 if ( !$conds ) {
2422                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2423                 }
2424
2425                 $table = $this->tableName( $table );
2426                 $sql = "DELETE FROM $table";
2427
2428                 if ( $conds != '*' ) {
2429                         if ( is_array( $conds ) ) {
2430                                 $conds = $this->makeList( $conds, self::LIST_AND );
2431                         }
2432                         $sql .= ' WHERE ' . $conds;
2433                 }
2434
2435                 return $this->query( $sql, $fname );
2436         }
2437
2438         public function insertSelect(
2439                 $destTable, $srcTable, $varMap, $conds,
2440                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2441         ) {
2442                 if ( $this->cliMode ) {
2443                         // For massive migrations with downtime, we don't want to select everything
2444                         // into memory and OOM, so do all this native on the server side if possible.
2445                         return $this->nativeInsertSelect(
2446                                 $destTable,
2447                                 $srcTable,
2448                                 $varMap,
2449                                 $conds,
2450                                 $fname,
2451                                 $insertOptions,
2452                                 $selectOptions,
2453                                 $selectJoinConds
2454                         );
2455                 }
2456
2457                 return $this->nonNativeInsertSelect(
2458                         $destTable,
2459                         $srcTable,
2460                         $varMap,
2461                         $conds,
2462                         $fname,
2463                         $insertOptions,
2464                         $selectOptions,
2465                         $selectJoinConds
2466                 );
2467         }
2468
2469         /**
2470          * Implementation of insertSelect() based on select() and insert()
2471          *
2472          * @see IDatabase::insertSelect()
2473          * @since 1.30
2474          * @param string $destTable
2475          * @param string|array $srcTable
2476          * @param array $varMap
2477          * @param array $conds
2478          * @param string $fname
2479          * @param array $insertOptions
2480          * @param array $selectOptions
2481          * @param array $selectJoinConds
2482          * @return bool
2483          */
2484         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2485                 $fname = __METHOD__,
2486                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2487         ) {
2488                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
2489                 // on only the master (without needing row-based-replication). It also makes it easy to
2490                 // know how big the INSERT is going to be.
2491                 $fields = [];
2492                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
2493                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
2494                 }
2495                 $selectOptions[] = 'FOR UPDATE';
2496                 $res = $this->select(
2497                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
2498                 );
2499                 if ( !$res ) {
2500                         return false;
2501                 }
2502
2503                 $rows = [];
2504                 foreach ( $res as $row ) {
2505                         $rows[] = (array)$row;
2506                 }
2507
2508                 return $this->insert( $destTable, $rows, $fname, $insertOptions );
2509         }
2510
2511         /**
2512          * Native server-side implementation of insertSelect() for situations where
2513          * we don't want to select everything into memory
2514          *
2515          * @see IDatabase::insertSelect()
2516          * @param string $destTable
2517          * @param string|array $srcTable
2518          * @param array $varMap
2519          * @param array $conds
2520          * @param string $fname
2521          * @param array $insertOptions
2522          * @param array $selectOptions
2523          * @param array $selectJoinConds
2524          * @return bool
2525          */
2526         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2527                 $fname = __METHOD__,
2528                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2529         ) {
2530                 $destTable = $this->tableName( $destTable );
2531
2532                 if ( !is_array( $insertOptions ) ) {
2533                         $insertOptions = [ $insertOptions ];
2534                 }
2535
2536                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2537
2538                 $selectSql = $this->selectSQLText(
2539                         $srcTable,
2540                         array_values( $varMap ),
2541                         $conds,
2542                         $fname,
2543                         $selectOptions,
2544                         $selectJoinConds
2545                 );
2546
2547                 $sql = "INSERT $insertOptions" .
2548                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
2549                         $selectSql;
2550
2551                 return $this->query( $sql, $fname );
2552         }
2553
2554         /**
2555          * Construct a LIMIT query with optional offset. This is used for query
2556          * pages. The SQL should be adjusted so that only the first $limit rows
2557          * are returned. If $offset is provided as well, then the first $offset
2558          * rows should be discarded, and the next $limit rows should be returned.
2559          * If the result of the query is not ordered, then the rows to be returned
2560          * are theoretically arbitrary.
2561          *
2562          * $sql is expected to be a SELECT, if that makes a difference.
2563          *
2564          * The version provided by default works in MySQL and SQLite. It will very
2565          * likely need to be overridden for most other DBMSes.
2566          *
2567          * @param string $sql SQL query we will append the limit too
2568          * @param int $limit The SQL limit
2569          * @param int|bool $offset The SQL offset (default false)
2570          * @throws DBUnexpectedError
2571          * @return string
2572          */
2573         public function limitResult( $sql, $limit, $offset = false ) {
2574                 if ( !is_numeric( $limit ) ) {
2575                         throw new DBUnexpectedError( $this,
2576                                 "Invalid non-numeric limit passed to limitResult()\n" );
2577                 }
2578
2579                 return "$sql LIMIT "
2580                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2581                 . "{$limit} ";
2582         }
2583
2584         public function unionSupportsOrderAndLimit() {
2585                 return true; // True for almost every DB supported
2586         }
2587
2588         public function unionQueries( $sqls, $all ) {
2589                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2590
2591                 return '(' . implode( $glue, $sqls ) . ')';
2592         }
2593
2594         public function unionConditionPermutations(
2595                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
2596                 $options = [], $join_conds = []
2597         ) {
2598                 // First, build the Cartesian product of $permute_conds
2599                 $conds = [ [] ];
2600                 foreach ( $permute_conds as $field => $values ) {
2601                         if ( !$values ) {
2602                                 // Skip empty $values
2603                                 continue;
2604                         }
2605                         $values = array_unique( $values ); // For sanity
2606                         $newConds = [];
2607                         foreach ( $conds as $cond ) {
2608                                 foreach ( $values as $value ) {
2609                                         $cond[$field] = $value;
2610                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
2611                                 }
2612                         }
2613                         $conds = $newConds;
2614                 }
2615
2616                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
2617
2618                 // If there's just one condition and no subordering, hand off to
2619                 // selectSQLText directly.
2620                 if ( count( $conds ) === 1 &&
2621                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
2622                 ) {
2623                         return $this->selectSQLText(
2624                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
2625                         );
2626                 }
2627
2628                 // Otherwise, we need to pull out the order and limit to apply after
2629                 // the union. Then build the SQL queries for each set of conditions in
2630                 // $conds. Then union them together (using UNION ALL, because the
2631                 // product *should* already be distinct).
2632                 $orderBy = $this->makeOrderBy( $options );
2633                 $limit = isset( $options['LIMIT'] ) ? $options['LIMIT'] : null;
2634                 $offset = isset( $options['OFFSET'] ) ? $options['OFFSET'] : false;
2635                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
2636                 if ( !$this->unionSupportsOrderAndLimit() ) {
2637                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
2638                 } else {
2639                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
2640                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
2641                         }
2642                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
2643                                 // We need to increase the limit by the offset rather than
2644                                 // using the offset directly, otherwise it'll skip incorrectly
2645                                 // in the subqueries.
2646                                 $options['LIMIT'] = $limit + $offset;
2647                                 unset( $options['OFFSET'] );
2648                         }
2649                 }
2650
2651                 $sqls = [];
2652                 foreach ( $conds as $cond ) {
2653                         $sqls[] = $this->selectSQLText(
2654                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
2655                         );
2656                 }
2657                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
2658                 if ( $limit !== null ) {
2659                         $sql = $this->limitResult( $sql, $limit, $offset );
2660                 }
2661
2662                 return $sql;
2663         }
2664
2665         public function conditional( $cond, $trueVal, $falseVal ) {
2666                 if ( is_array( $cond ) ) {
2667                         $cond = $this->makeList( $cond, self::LIST_AND );
2668                 }
2669
2670                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2671         }
2672
2673         public function strreplace( $orig, $old, $new ) {
2674                 return "REPLACE({$orig}, {$old}, {$new})";
2675         }
2676
2677         public function getServerUptime() {
2678                 return 0;
2679         }
2680
2681         public function wasDeadlock() {
2682                 return false;
2683         }
2684
2685         public function wasLockTimeout() {
2686                 return false;
2687         }
2688
2689         public function wasErrorReissuable() {
2690                 return false;
2691         }
2692
2693         public function wasReadOnlyError() {
2694                 return false;
2695         }
2696
2697         /**
2698          * Do not use this method outside of Database/DBError classes
2699          *
2700          * @param int|string $errno
2701          * @return bool Whether the given query error was a connection drop
2702          */
2703         public function wasConnectionError( $errno ) {
2704                 return false;
2705         }
2706
2707         public function deadlockLoop() {
2708                 $args = func_get_args();
2709                 $function = array_shift( $args );
2710                 $tries = self::DEADLOCK_TRIES;
2711
2712                 $this->begin( __METHOD__ );
2713
2714                 $retVal = null;
2715                 /** @var Exception $e */
2716                 $e = null;
2717                 do {
2718                         try {
2719                                 $retVal = call_user_func_array( $function, $args );
2720                                 break;
2721                         } catch ( DBQueryError $e ) {
2722                                 if ( $this->wasDeadlock() ) {
2723                                         // Retry after a randomized delay
2724                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
2725                                 } else {
2726                                         // Throw the error back up
2727                                         throw $e;
2728                                 }
2729                         }
2730                 } while ( --$tries > 0 );
2731
2732                 if ( $tries <= 0 ) {
2733                         // Too many deadlocks; give up
2734                         $this->rollback( __METHOD__ );
2735                         throw $e;
2736                 } else {
2737                         $this->commit( __METHOD__ );
2738
2739                         return $retVal;
2740                 }
2741         }
2742
2743         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2744                 # Real waits are implemented in the subclass.
2745                 return 0;
2746         }
2747
2748         public function getReplicaPos() {
2749                 # Stub
2750                 return false;
2751         }
2752
2753         public function getMasterPos() {
2754                 # Stub
2755                 return false;
2756         }
2757
2758         public function serverIsReadOnly() {
2759                 return false;
2760         }
2761
2762         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
2763                 if ( !$this->mTrxLevel ) {
2764                         throw new DBUnexpectedError( $this, "No transaction is active." );
2765                 }
2766                 $this->mTrxEndCallbacks[] = [ $callback, $fname ];
2767         }
2768
2769         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
2770                 $this->mTrxIdleCallbacks[] = [ $callback, $fname ];
2771                 if ( !$this->mTrxLevel ) {
2772                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
2773                 }
2774         }
2775
2776         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
2777                 if ( $this->mTrxLevel || $this->getFlag( self::DBO_TRX ) ) {
2778                         // As long as DBO_TRX is set, writes will accumulate until the load balancer issues
2779                         // an implicit commit of all peer databases. This is true even if a transaction has
2780                         // not yet been triggered by writes; make sure $callback runs *after* any such writes.
2781                         $this->mTrxPreCommitCallbacks[] = [ $callback, $fname ];
2782                 } else {
2783                         // No transaction is active nor will start implicitly, so make one for this callback
2784                         $this->startAtomic( __METHOD__ );
2785                         try {
2786                                 call_user_func( $callback );
2787                                 $this->endAtomic( __METHOD__ );
2788                         } catch ( Exception $e ) {
2789                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2790                                 throw $e;
2791                         }
2792                 }
2793         }
2794
2795         final public function setTransactionListener( $name, callable $callback = null ) {
2796                 if ( $callback ) {
2797                         $this->mTrxRecurringCallbacks[$name] = $callback;
2798                 } else {
2799                         unset( $this->mTrxRecurringCallbacks[$name] );
2800                 }
2801         }
2802
2803         /**
2804          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
2805          *
2806          * This method should not be used outside of Database/LoadBalancer
2807          *
2808          * @param bool $suppress
2809          * @since 1.28
2810          */
2811         final public function setTrxEndCallbackSuppression( $suppress ) {
2812                 $this->mTrxEndCallbacksSuppressed = $suppress;
2813         }
2814
2815         /**
2816          * Actually run and consume any "on transaction idle/resolution" callbacks.
2817          *
2818          * This method should not be used outside of Database/LoadBalancer
2819          *
2820          * @param int $trigger IDatabase::TRIGGER_* constant
2821          * @since 1.20
2822          * @throws Exception
2823          */
2824         public function runOnTransactionIdleCallbacks( $trigger ) {
2825                 if ( $this->mTrxEndCallbacksSuppressed ) {
2826                         return;
2827                 }
2828
2829                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
2830                 /** @var Exception $e */
2831                 $e = null; // first exception
2832                 do { // callbacks may add callbacks :)
2833                         $callbacks = array_merge(
2834                                 $this->mTrxIdleCallbacks,
2835                                 $this->mTrxEndCallbacks // include "transaction resolution" callbacks
2836                         );
2837                         $this->mTrxIdleCallbacks = []; // consumed (and recursion guard)
2838                         $this->mTrxEndCallbacks = []; // consumed (recursion guard)
2839                         foreach ( $callbacks as $callback ) {
2840                                 try {
2841                                         list( $phpCallback ) = $callback;
2842                                         $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
2843                                         call_user_func_array( $phpCallback, [ $trigger ] );
2844                                         if ( $autoTrx ) {
2845                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
2846                                         } else {
2847                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
2848                                         }
2849                                 } catch ( Exception $ex ) {
2850                                         call_user_func( $this->errorLogger, $ex );
2851                                         $e = $e ?: $ex;
2852                                         // Some callbacks may use startAtomic/endAtomic, so make sure
2853                                         // their transactions are ended so other callbacks don't fail
2854                                         if ( $this->trxLevel() ) {
2855                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2856                                         }
2857                                 }
2858                         }
2859                 } while ( count( $this->mTrxIdleCallbacks ) );
2860
2861                 if ( $e instanceof Exception ) {
2862                         throw $e; // re-throw any first exception
2863                 }
2864         }
2865
2866         /**
2867          * Actually run and consume any "on transaction pre-commit" callbacks.
2868          *
2869          * This method should not be used outside of Database/LoadBalancer
2870          *
2871          * @since 1.22
2872          * @throws Exception
2873          */
2874         public function runOnTransactionPreCommitCallbacks() {
2875                 $e = null; // first exception
2876                 do { // callbacks may add callbacks :)
2877                         $callbacks = $this->mTrxPreCommitCallbacks;
2878                         $this->mTrxPreCommitCallbacks = []; // consumed (and recursion guard)
2879                         foreach ( $callbacks as $callback ) {
2880                                 try {
2881                                         list( $phpCallback ) = $callback;
2882                                         call_user_func( $phpCallback );
2883                                 } catch ( Exception $ex ) {
2884                                         call_user_func( $this->errorLogger, $ex );
2885                                         $e = $e ?: $ex;
2886                                 }
2887                         }
2888                 } while ( count( $this->mTrxPreCommitCallbacks ) );
2889
2890                 if ( $e instanceof Exception ) {
2891                         throw $e; // re-throw any first exception
2892                 }
2893         }
2894
2895         /**
2896          * Actually run any "transaction listener" callbacks.
2897          *
2898          * This method should not be used outside of Database/LoadBalancer
2899          *
2900          * @param int $trigger IDatabase::TRIGGER_* constant
2901          * @throws Exception
2902          * @since 1.20
2903          */
2904         public function runTransactionListenerCallbacks( $trigger ) {
2905                 if ( $this->mTrxEndCallbacksSuppressed ) {
2906                         return;
2907                 }
2908
2909                 /** @var Exception $e */
2910                 $e = null; // first exception
2911
2912                 foreach ( $this->mTrxRecurringCallbacks as $phpCallback ) {
2913                         try {
2914                                 $phpCallback( $trigger, $this );
2915                         } catch ( Exception $ex ) {
2916                                 call_user_func( $this->errorLogger, $ex );
2917                                 $e = $e ?: $ex;
2918                         }
2919                 }
2920
2921                 if ( $e instanceof Exception ) {
2922                         throw $e; // re-throw any first exception
2923                 }
2924         }
2925
2926         final public function startAtomic( $fname = __METHOD__ ) {
2927                 if ( !$this->mTrxLevel ) {
2928                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2929                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
2930                         // in all changes being in one transaction to keep requests transactional.
2931                         if ( !$this->getFlag( self::DBO_TRX ) ) {
2932                                 $this->mTrxAutomaticAtomic = true;
2933                         }
2934                 }
2935
2936                 $this->mTrxAtomicLevels[] = $fname;
2937         }
2938
2939         final public function endAtomic( $fname = __METHOD__ ) {
2940                 if ( !$this->mTrxLevel ) {
2941                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
2942                 }
2943                 if ( !$this->mTrxAtomicLevels ||
2944                         array_pop( $this->mTrxAtomicLevels ) !== $fname
2945                 ) {
2946                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
2947                 }
2948
2949                 if ( !$this->mTrxAtomicLevels && $this->mTrxAutomaticAtomic ) {
2950                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2951                 }
2952         }
2953
2954         final public function doAtomicSection( $fname, callable $callback ) {
2955                 $this->startAtomic( $fname );
2956                 try {
2957                         $res = call_user_func_array( $callback, [ $this, $fname ] );
2958                 } catch ( Exception $e ) {
2959                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2960                         throw $e;
2961                 }
2962                 $this->endAtomic( $fname );
2963
2964                 return $res;
2965         }
2966
2967         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
2968                 if ( !$this->allowWrite ) {
2969                         throw new DBError(
2970                                 $this,
2971                                 'Write operations are not allowed on this database connection!'
2972                         );
2973                 }
2974
2975                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
2976                 if ( $this->mTrxLevel ) {
2977                         if ( $this->mTrxAtomicLevels ) {
2978                                 $levels = implode( ', ', $this->mTrxAtomicLevels );
2979                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
2980                                 throw new DBUnexpectedError( $this, $msg );
2981                         } elseif ( !$this->mTrxAutomatic ) {
2982                                 $msg = "$fname: Explicit transaction already active (from {$this->mTrxFname}).";
2983                                 throw new DBUnexpectedError( $this, $msg );
2984                         } else {
2985                                 // @TODO: make this an exception at some point
2986                                 $msg = "$fname: Implicit transaction already active (from {$this->mTrxFname}).";
2987                                 $this->queryLogger->error( $msg );
2988                                 return; // join the main transaction set
2989                         }
2990                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
2991                         // @TODO: make this an exception at some point
2992                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
2993                         $this->queryLogger->error( $msg );
2994                         return; // let any writes be in the main transaction
2995                 }
2996
2997                 // Avoid fatals if close() was called
2998                 $this->assertOpen();
2999
3000                 $this->doBegin( $fname );
3001                 $this->mTrxTimestamp = microtime( true );
3002                 $this->mTrxFname = $fname;
3003                 $this->mTrxDoneWrites = false;
3004                 $this->mTrxAutomaticAtomic = false;
3005                 $this->mTrxAtomicLevels = [];
3006                 $this->mTrxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
3007                 $this->mTrxWriteDuration = 0.0;
3008                 $this->mTrxWriteQueryCount = 0;
3009                 $this->mTrxWriteAffectedRows = 0;
3010                 $this->mTrxWriteAdjDuration = 0.0;
3011                 $this->mTrxWriteAdjQueryCount = 0;
3012                 $this->mTrxWriteCallers = [];
3013                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
3014                 // Get an estimate of the replica DB lag before then, treating estimate staleness
3015                 // as lag itself just to be safe
3016                 $status = $this->getApproximateLagStatus();
3017                 $this->mTrxReplicaLag = $status['lag'] + ( microtime( true ) - $status['since'] );
3018                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
3019                 // caller will think its OK to muck around with the transaction just because startAtomic()
3020                 // has not yet completed (e.g. setting mTrxAtomicLevels).
3021                 $this->mTrxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
3022         }
3023
3024         /**
3025          * Issues the BEGIN command to the database server.
3026          *
3027          * @see Database::begin()
3028          * @param string $fname
3029          */
3030         protected function doBegin( $fname ) {
3031                 $this->query( 'BEGIN', $fname );
3032                 $this->mTrxLevel = 1;
3033         }
3034
3035         final public function commit( $fname = __METHOD__, $flush = '' ) {
3036                 if ( !$this->allowWrite ) {
3037                         // we should never get here, since begin() would already throw
3038                         throw new DBError(
3039                                 $this,
3040                                 'Write operations are not allowed on this database connection!'
3041                         );
3042                 }
3043
3044                 if ( $this->mTrxLevel && $this->mTrxAtomicLevels ) {
3045                         // There are still atomic sections open. This cannot be ignored
3046                         $levels = implode( ', ', $this->mTrxAtomicLevels );
3047                         throw new DBUnexpectedError(
3048                                 $this,
3049                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3050                         );
3051                 }
3052
3053                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3054                         if ( !$this->mTrxLevel ) {
3055                                 return; // nothing to do
3056                         } elseif ( !$this->mTrxAutomatic ) {
3057                                 throw new DBUnexpectedError(
3058                                         $this,
3059                                         "$fname: Flushing an explicit transaction, getting out of sync."
3060                                 );
3061                         }
3062                 } else {
3063                         if ( !$this->mTrxLevel ) {
3064                                 $this->queryLogger->error(
3065                                         "$fname: No transaction to commit, something got out of sync." );
3066                                 return; // nothing to do
3067                         } elseif ( $this->mTrxAutomatic ) {
3068                                 // @TODO: make this an exception at some point
3069                                 $msg = "$fname: Explicit commit of implicit transaction.";
3070                                 $this->queryLogger->error( $msg );
3071                                 return; // wait for the main transaction set commit round
3072                         }
3073                 }
3074
3075                 // Avoid fatals if close() was called
3076                 $this->assertOpen();
3077
3078                 $this->runOnTransactionPreCommitCallbacks();
3079                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3080                 $this->doCommit( $fname );
3081                 if ( $this->mTrxDoneWrites ) {
3082                         $this->mLastWriteTime = microtime( true );
3083                         $this->trxProfiler->transactionWritingOut(
3084                                 $this->mServer,
3085                                 $this->mDBname,
3086                                 $this->mTrxShortId,
3087                                 $writeTime,
3088                                 $this->mTrxWriteAffectedRows
3089                         );
3090                 }
3091
3092                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3093                 $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3094         }
3095
3096         /**
3097          * Issues the COMMIT command to the database server.
3098          *
3099          * @see Database::commit()
3100          * @param string $fname
3101          */
3102         protected function doCommit( $fname ) {
3103                 if ( $this->mTrxLevel ) {
3104                         $this->query( 'COMMIT', $fname );
3105                         $this->mTrxLevel = 0;
3106                 }
3107         }
3108
3109         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3110                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3111                         if ( !$this->mTrxLevel ) {
3112                                 return; // nothing to do
3113                         }
3114                 } else {
3115                         if ( !$this->mTrxLevel ) {
3116                                 $this->queryLogger->error(
3117                                         "$fname: No transaction to rollback, something got out of sync." );
3118                                 return; // nothing to do
3119                         } elseif ( $this->getFlag( self::DBO_TRX ) ) {
3120                                 throw new DBUnexpectedError(
3121                                         $this,
3122                                         "$fname: Expected mass rollback of all peer databases (DBO_TRX set)."
3123                                 );
3124                         }
3125                 }
3126
3127                 // Avoid fatals if close() was called
3128                 $this->assertOpen();
3129
3130                 $this->doRollback( $fname );
3131                 $this->mTrxAtomicLevels = [];
3132                 if ( $this->mTrxDoneWrites ) {
3133                         $this->trxProfiler->transactionWritingOut(
3134                                 $this->mServer,
3135                                 $this->mDBname,
3136                                 $this->mTrxShortId
3137                         );
3138                 }
3139
3140                 $this->mTrxIdleCallbacks = []; // clear
3141                 $this->mTrxPreCommitCallbacks = []; // clear
3142                 try {
3143                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
3144                 } catch ( Exception $e ) {
3145                         // already logged; finish and let LoadBalancer move on during mass-rollback
3146                 }
3147                 try {
3148                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
3149                 } catch ( Exception $e ) {
3150                         // already logged; let LoadBalancer move on during mass-rollback
3151                 }
3152         }
3153
3154         /**
3155          * Issues the ROLLBACK command to the database server.
3156          *
3157          * @see Database::rollback()
3158          * @param string $fname
3159          */
3160         protected function doRollback( $fname ) {
3161                 if ( $this->mTrxLevel ) {
3162                         # Disconnects cause rollback anyway, so ignore those errors
3163                         $ignoreErrors = true;
3164                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
3165                         $this->mTrxLevel = 0;
3166                 }
3167         }
3168
3169         public function flushSnapshot( $fname = __METHOD__ ) {
3170                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
3171                         // This only flushes transactions to clear snapshots, not to write data
3172                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3173                         throw new DBUnexpectedError(
3174                                 $this,
3175                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
3176                         );
3177                 }
3178
3179                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3180         }
3181
3182         public function explicitTrxActive() {
3183                 return $this->mTrxLevel && ( $this->mTrxAtomicLevels || !$this->mTrxAutomatic );
3184         }
3185
3186         public function duplicateTableStructure(
3187                 $oldName, $newName, $temporary = false, $fname = __METHOD__
3188         ) {
3189                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3190         }
3191
3192         public function listTables( $prefix = null, $fname = __METHOD__ ) {
3193                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3194         }
3195
3196         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3197                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3198         }
3199
3200         public function timestamp( $ts = 0 ) {
3201                 $t = new ConvertibleTimestamp( $ts );
3202                 // Let errors bubble up to avoid putting garbage in the DB
3203                 return $t->getTimestamp( TS_MW );
3204         }
3205
3206         public function timestampOrNull( $ts = null ) {
3207                 if ( is_null( $ts ) ) {
3208                         return null;
3209                 } else {
3210                         return $this->timestamp( $ts );
3211                 }
3212         }
3213
3214         /**
3215          * Take the result from a query, and wrap it in a ResultWrapper if
3216          * necessary. Boolean values are passed through as is, to indicate success
3217          * of write queries or failure.
3218          *
3219          * Once upon a time, Database::query() returned a bare MySQL result
3220          * resource, and it was necessary to call this function to convert it to
3221          * a wrapper. Nowadays, raw database objects are never exposed to external
3222          * callers, so this is unnecessary in external code.
3223          *
3224          * @param bool|ResultWrapper|resource|object $result
3225          * @return bool|ResultWrapper
3226          */
3227         protected function resultObject( $result ) {
3228                 if ( !$result ) {
3229                         return false;
3230                 } elseif ( $result instanceof ResultWrapper ) {
3231                         return $result;
3232                 } elseif ( $result === true ) {
3233                         // Successful write query
3234                         return $result;
3235                 } else {
3236                         return new ResultWrapper( $this, $result );
3237                 }
3238         }
3239
3240         public function ping( &$rtt = null ) {
3241                 // Avoid hitting the server if it was hit recently
3242                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
3243                         if ( !func_num_args() || $this->mRTTEstimate > 0 ) {
3244                                 $rtt = $this->mRTTEstimate;
3245                                 return true; // don't care about $rtt
3246                         }
3247                 }
3248
3249                 // This will reconnect if possible or return false if not
3250                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
3251                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
3252                 $this->restoreFlags( self::RESTORE_PRIOR );
3253
3254                 if ( $ok ) {
3255                         $rtt = $this->mRTTEstimate;
3256                 }
3257
3258                 return $ok;
3259         }
3260
3261         /**
3262          * Close existing database connection and open a new connection
3263          *
3264          * @return bool True if new connection is opened successfully, false if error
3265          */
3266         protected function reconnect() {
3267                 $this->closeConnection();
3268                 $this->mOpened = false;
3269                 $this->mConn = false;
3270                 try {
3271                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3272                         $this->lastPing = microtime( true );
3273                         $ok = true;
3274                 } catch ( DBConnectionError $e ) {
3275                         $ok = false;
3276                 }
3277
3278                 return $ok;
3279         }
3280
3281         public function getSessionLagStatus() {
3282                 return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
3283         }
3284
3285         /**
3286          * Get the replica DB lag when the current transaction started
3287          *
3288          * This is useful when transactions might use snapshot isolation
3289          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
3290          * is this lag plus transaction duration. If they don't, it is still
3291          * safe to be pessimistic. This returns null if there is no transaction.
3292          *
3293          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
3294          * @since 1.27
3295          */
3296         protected function getTransactionLagStatus() {
3297                 return $this->mTrxLevel
3298                         ? [ 'lag' => $this->mTrxReplicaLag, 'since' => $this->trxTimestamp() ]
3299                         : null;
3300         }
3301
3302         /**
3303          * Get a replica DB lag estimate for this server
3304          *
3305          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
3306          * @since 1.27
3307          */
3308         protected function getApproximateLagStatus() {
3309                 return [
3310                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
3311                         'since' => microtime( true )
3312                 ];
3313         }
3314
3315         /**
3316          * Merge the result of getSessionLagStatus() for several DBs
3317          * using the most pessimistic values to estimate the lag of
3318          * any data derived from them in combination
3319          *
3320          * This is information is useful for caching modules
3321          *
3322          * @see WANObjectCache::set()
3323          * @see WANObjectCache::getWithSetCallback()
3324          *
3325          * @param IDatabase $db1
3326          * @param IDatabase $db2 [optional]
3327          * @return array Map of values:
3328          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3329          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3330          *   - pending: whether any of the DBs have uncommitted changes
3331          * @throws DBError
3332          * @since 1.27
3333          */
3334         public static function getCacheSetOptions( IDatabase $db1, IDatabase $db2 = null ) {
3335                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3336                 foreach ( func_get_args() as $db ) {
3337                         /** @var IDatabase $db */
3338                         $status = $db->getSessionLagStatus();
3339                         if ( $status['lag'] === false ) {
3340                                 $res['lag'] = false;
3341                         } elseif ( $res['lag'] !== false ) {
3342                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3343                         }
3344                         $res['since'] = min( $res['since'], $status['since'] );
3345                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3346                 }
3347
3348                 return $res;
3349         }
3350
3351         public function getLag() {
3352                 return 0;
3353         }
3354
3355         public function maxListLen() {
3356                 return 0;
3357         }
3358
3359         public function encodeBlob( $b ) {
3360                 return $b;
3361         }
3362
3363         public function decodeBlob( $b ) {
3364                 if ( $b instanceof Blob ) {
3365                         $b = $b->fetch();
3366                 }
3367                 return $b;
3368         }
3369
3370         public function setSessionOptions( array $options ) {
3371         }
3372
3373         public function sourceFile(
3374                 $filename,
3375                 callable $lineCallback = null,
3376                 callable $resultCallback = null,
3377                 $fname = false,
3378                 callable $inputCallback = null
3379         ) {
3380                 MediaWiki\suppressWarnings();
3381                 $fp = fopen( $filename, 'r' );
3382                 MediaWiki\restoreWarnings();
3383
3384                 if ( false === $fp ) {
3385                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
3386                 }
3387
3388                 if ( !$fname ) {
3389                         $fname = __METHOD__ . "( $filename )";
3390                 }
3391
3392                 try {
3393                         $error = $this->sourceStream(
3394                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3395                 } catch ( Exception $e ) {
3396                         fclose( $fp );
3397                         throw $e;
3398                 }
3399
3400                 fclose( $fp );
3401
3402                 return $error;
3403         }
3404
3405         public function setSchemaVars( $vars ) {
3406                 $this->mSchemaVars = $vars;
3407         }
3408
3409         public function sourceStream(
3410                 $fp,
3411                 callable $lineCallback = null,
3412                 callable $resultCallback = null,
3413                 $fname = __METHOD__,
3414                 callable $inputCallback = null
3415         ) {
3416                 $cmd = '';
3417
3418                 while ( !feof( $fp ) ) {
3419                         if ( $lineCallback ) {
3420                                 call_user_func( $lineCallback );
3421                         }
3422
3423                         $line = trim( fgets( $fp ) );
3424
3425                         if ( $line == '' ) {
3426                                 continue;
3427                         }
3428
3429                         if ( '-' == $line[0] && '-' == $line[1] ) {
3430                                 continue;
3431                         }
3432
3433                         if ( $cmd != '' ) {
3434                                 $cmd .= ' ';
3435                         }
3436
3437                         $done = $this->streamStatementEnd( $cmd, $line );
3438
3439                         $cmd .= "$line\n";
3440
3441                         if ( $done || feof( $fp ) ) {
3442                                 $cmd = $this->replaceVars( $cmd );
3443
3444                                 if ( !$inputCallback || call_user_func( $inputCallback, $cmd ) ) {
3445                                         $res = $this->query( $cmd, $fname );
3446
3447                                         if ( $resultCallback ) {
3448                                                 call_user_func( $resultCallback, $res, $this );
3449                                         }
3450
3451                                         if ( false === $res ) {
3452                                                 $err = $this->lastError();
3453
3454                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3455                                         }
3456                                 }
3457                                 $cmd = '';
3458                         }
3459                 }
3460
3461                 return true;
3462         }
3463
3464         /**
3465          * Called by sourceStream() to check if we've reached a statement end
3466          *
3467          * @param string &$sql SQL assembled so far
3468          * @param string &$newLine New line about to be added to $sql
3469          * @return bool Whether $newLine contains end of the statement
3470          */
3471         public function streamStatementEnd( &$sql, &$newLine ) {
3472                 if ( $this->delimiter ) {
3473                         $prev = $newLine;
3474                         $newLine = preg_replace(
3475                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3476                         if ( $newLine != $prev ) {
3477                                 return true;
3478                         }
3479                 }
3480
3481                 return false;
3482         }
3483
3484         /**
3485          * Database independent variable replacement. Replaces a set of variables
3486          * in an SQL statement with their contents as given by $this->getSchemaVars().
3487          *
3488          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3489          *
3490          * - '{$var}' should be used for text and is passed through the database's
3491          *   addQuotes method.
3492          * - `{$var}` should be used for identifiers (e.g. table and database names).
3493          *   It is passed through the database's addIdentifierQuotes method which
3494          *   can be overridden if the database uses something other than backticks.
3495          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
3496          *   database's tableName method.
3497          * - / *i* / passes the name that follows through the database's indexName method.
3498          * - In all other cases, / *$var* / is left unencoded. Except for table options,
3499          *   its use should be avoided. In 1.24 and older, string encoding was applied.
3500          *
3501          * @param string $ins SQL statement to replace variables in
3502          * @return string The new SQL statement with variables replaced
3503          */
3504         protected function replaceVars( $ins ) {
3505                 $vars = $this->getSchemaVars();
3506                 return preg_replace_callback(
3507                         '!
3508                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
3509                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
3510                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
3511                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
3512                         !x',
3513                         function ( $m ) use ( $vars ) {
3514                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
3515                                 // check for both nonexistent keys *and* the empty string.
3516                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
3517                                         if ( $m[1] === 'i' ) {
3518                                                 return $this->indexName( $m[2] );
3519                                         } else {
3520                                                 return $this->tableName( $m[2] );
3521                                         }
3522                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
3523                                         return $this->addQuotes( $vars[$m[3]] );
3524                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
3525                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
3526                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
3527                                         return $vars[$m[5]];
3528                                 } else {
3529                                         return $m[0];
3530                                 }
3531                         },
3532                         $ins
3533                 );
3534         }
3535
3536         /**
3537          * Get schema variables. If none have been set via setSchemaVars(), then
3538          * use some defaults from the current object.
3539          *
3540          * @return array
3541          */
3542         protected function getSchemaVars() {
3543                 if ( $this->mSchemaVars ) {
3544                         return $this->mSchemaVars;
3545                 } else {
3546                         return $this->getDefaultSchemaVars();
3547                 }
3548         }
3549
3550         /**
3551          * Get schema variables to use if none have been set via setSchemaVars().
3552          *
3553          * Override this in derived classes to provide variables for tables.sql
3554          * and SQL patch files.
3555          *
3556          * @return array
3557          */
3558         protected function getDefaultSchemaVars() {
3559                 return [];
3560         }
3561
3562         public function lockIsFree( $lockName, $method ) {
3563                 return true;
3564         }
3565
3566         public function lock( $lockName, $method, $timeout = 5 ) {
3567                 $this->mNamedLocksHeld[$lockName] = 1;
3568
3569                 return true;
3570         }
3571
3572         public function unlock( $lockName, $method ) {
3573                 unset( $this->mNamedLocksHeld[$lockName] );
3574
3575                 return true;
3576         }
3577
3578         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
3579                 if ( $this->writesOrCallbacksPending() ) {
3580                         // This only flushes transactions to clear snapshots, not to write data
3581                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3582                         throw new DBUnexpectedError(
3583                                 $this,
3584                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
3585                         );
3586                 }
3587
3588                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
3589                         return null;
3590                 }
3591
3592                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
3593                         if ( $this->trxLevel() ) {
3594                                 // There is a good chance an exception was thrown, causing any early return
3595                                 // from the caller. Let any error handler get a chance to issue rollback().
3596                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
3597                                 $this->onTransactionResolution(
3598                                         function () use ( $lockKey, $fname ) {
3599                                                 $this->unlock( $lockKey, $fname );
3600                                         },
3601                                         $fname
3602                                 );
3603                         } else {
3604                                 $this->unlock( $lockKey, $fname );
3605                         }
3606                 } );
3607
3608                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3609
3610                 return $unlocker;
3611         }
3612
3613         public function namedLocksEnqueue() {
3614                 return false;
3615         }
3616
3617         public function tableLocksHaveTransactionScope() {
3618                 return true;
3619         }
3620
3621         final public function lockTables( array $read, array $write, $method ) {
3622                 if ( $this->writesOrCallbacksPending() ) {
3623                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
3624                 }
3625
3626                 if ( $this->tableLocksHaveTransactionScope() ) {
3627                         $this->startAtomic( $method );
3628                 }
3629
3630                 return $this->doLockTables( $read, $write, $method );
3631         }
3632
3633         /**
3634          * Helper function for lockTables() that handles the actual table locking
3635          *
3636          * @param array $read Array of tables to lock for read access
3637          * @param array $write Array of tables to lock for write access
3638          * @param string $method Name of caller
3639          * @return true
3640          */
3641         protected function doLockTables( array $read, array $write, $method ) {
3642                 return true;
3643         }
3644
3645         final public function unlockTables( $method ) {
3646                 if ( $this->tableLocksHaveTransactionScope() ) {
3647                         $this->endAtomic( $method );
3648
3649                         return true; // locks released on COMMIT/ROLLBACK
3650                 }
3651
3652                 return $this->doUnlockTables( $method );
3653         }
3654
3655         /**
3656          * Helper function for unlockTables() that handles the actual table unlocking
3657          *
3658          * @param string $method Name of caller
3659          * @return true
3660          */
3661         protected function doUnlockTables( $method ) {
3662                 return true;
3663         }
3664
3665         /**
3666          * Delete a table
3667          * @param string $tableName
3668          * @param string $fName
3669          * @return bool|ResultWrapper
3670          * @since 1.18
3671          */
3672         public function dropTable( $tableName, $fName = __METHOD__ ) {
3673                 if ( !$this->tableExists( $tableName, $fName ) ) {
3674                         return false;
3675                 }
3676                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
3677
3678                 return $this->query( $sql, $fName );
3679         }
3680
3681         public function getInfinity() {
3682                 return 'infinity';
3683         }
3684
3685         public function encodeExpiry( $expiry ) {
3686                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3687                         ? $this->getInfinity()
3688                         : $this->timestamp( $expiry );
3689         }
3690
3691         public function decodeExpiry( $expiry, $format = TS_MW ) {
3692                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
3693                         return 'infinity';
3694                 }
3695
3696                 return ConvertibleTimestamp::convert( $format, $expiry );
3697         }
3698
3699         public function setBigSelects( $value = true ) {
3700                 // no-op
3701         }
3702
3703         public function isReadOnly() {
3704                 return ( $this->getReadOnlyReason() !== false );
3705         }
3706
3707         /**
3708          * @return string|bool Reason this DB is read-only or false if it is not
3709          */
3710         protected function getReadOnlyReason() {
3711                 $reason = $this->getLBInfo( 'readOnlyReason' );
3712
3713                 return is_string( $reason ) ? $reason : false;
3714         }
3715
3716         public function setTableAliases( array $aliases ) {
3717                 $this->tableAliases = $aliases;
3718         }
3719
3720         /**
3721          * @return bool Whether a DB user is required to access the DB
3722          * @since 1.28
3723          */
3724         protected function requiresDatabaseUser() {
3725                 return true;
3726         }
3727
3728         /**
3729          * Get the underlying binding handle, mConn
3730          *
3731          * Makes sure that mConn is set (disconnects and ping() failure can unset it).
3732          * This catches broken callers than catch and ignore disconnection exceptions.
3733          * Unlike checking isOpen(), this is safe to call inside of open().
3734          *
3735          * @return resource|object
3736          * @throws DBUnexpectedError
3737          * @since 1.26
3738          */
3739         protected function getBindingHandle() {
3740                 if ( !$this->mConn ) {
3741                         throw new DBUnexpectedError(
3742                                 $this,
3743                                 'DB connection was already closed or the connection dropped.'
3744                         );
3745                 }
3746
3747                 return $this->mConn;
3748         }
3749
3750         /**
3751          * @since 1.19
3752          * @return string
3753          */
3754         public function __toString() {
3755                 return (string)$this->mConn;
3756         }
3757
3758         /**
3759          * Make sure that copies do not share the same client binding handle
3760          * @throws DBConnectionError
3761          */
3762         public function __clone() {
3763                 $this->connLogger->warning(
3764                         "Cloning " . static::class . " is not recomended; forking connection:\n" .
3765                         ( new RuntimeException() )->getTraceAsString()
3766                 );
3767
3768                 if ( $this->isOpen() ) {
3769                         // Open a new connection resource without messing with the old one
3770                         $this->mOpened = false;
3771                         $this->mConn = false;
3772                         $this->mTrxEndCallbacks = []; // don't copy
3773                         $this->handleSessionLoss(); // no trx or locks anymore
3774                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3775                         $this->lastPing = microtime( true );
3776                 }
3777         }
3778
3779         /**
3780          * Called by serialize. Throw an exception when DB connection is serialized.
3781          * This causes problems on some database engines because the connection is
3782          * not restored on unserialize.
3783          */
3784         public function __sleep() {
3785                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
3786                         'the connection is not restored on wakeup.' );
3787         }
3788
3789         /**
3790          * Run a few simple sanity checks and close dangling connections
3791          */
3792         public function __destruct() {
3793                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
3794                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
3795                 }
3796
3797                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
3798                 if ( $danglingWriters ) {
3799                         $fnames = implode( ', ', $danglingWriters );
3800                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
3801                 }
3802
3803                 if ( $this->mConn ) {
3804                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
3805                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
3806                         \MediaWiki\suppressWarnings();
3807                         $this->closeConnection();
3808                         \MediaWiki\restoreWarnings();
3809                         $this->mConn = false;
3810                         $this->mOpened = false;
3811                 }
3812         }
3813 }
3814
3815 class_alias( Database::class, 'DatabaseBase' ); // b/c for old name
3816 class_alias( Database::class, 'Database' ); // b/c global alias