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