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                         if ( $table[0] == ' ' ) {
1409                                 $from = ' FROM ' . $table;
1410                         } else {
1411                                 $from = ' FROM ' .
1412                                         $this->tableNamesWithIndexClauseOrJOIN(
1413                                                 [ $table ], $useIndexes, $ignoreIndexes, [] );
1414                         }
1415                 } else {
1416                         $from = '';
1417                 }
1418
1419                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1420                         $this->makeSelectOptions( $options );
1421
1422                 if ( !empty( $conds ) ) {
1423                         if ( is_array( $conds ) ) {
1424                                 $conds = $this->makeList( $conds, self::LIST_AND );
1425                         }
1426                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex " .
1427                                 "WHERE $conds $preLimitTail";
1428                 } else {
1429                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex $preLimitTail";
1430                 }
1431
1432                 if ( isset( $options['LIMIT'] ) ) {
1433                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1434                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1435                 }
1436                 $sql = "$sql $postLimitTail";
1437
1438                 if ( isset( $options['EXPLAIN'] ) ) {
1439                         $sql = 'EXPLAIN ' . $sql;
1440                 }
1441
1442                 return $sql;
1443         }
1444
1445         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1446                 $options = [], $join_conds = []
1447         ) {
1448                 $options = (array)$options;
1449                 $options['LIMIT'] = 1;
1450                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1451
1452                 if ( $res === false ) {
1453                         return false;
1454                 }
1455
1456                 if ( !$this->numRows( $res ) ) {
1457                         return false;
1458                 }
1459
1460                 $obj = $this->fetchObject( $res );
1461
1462                 return $obj;
1463         }
1464
1465         public function estimateRowCount(
1466                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
1467         ) {
1468                 $rows = 0;
1469                 $res = $this->select( $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options );
1470
1471                 if ( $res ) {
1472                         $row = $this->fetchRow( $res );
1473                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1474                 }
1475
1476                 return $rows;
1477         }
1478
1479         public function selectRowCount(
1480                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1481         ) {
1482                 $rows = 0;
1483                 $sql = $this->selectSQLText( $tables, '1', $conds, $fname, $options, $join_conds );
1484                 // The identifier quotes is primarily for MSSQL.
1485                 $rowCountCol = $this->addIdentifierQuotes( "rowcount" );
1486                 $tableName = $this->addIdentifierQuotes( "tmp_count" );
1487                 $res = $this->query( "SELECT COUNT(*) AS $rowCountCol FROM ($sql) $tableName", $fname );
1488
1489                 if ( $res ) {
1490                         $row = $this->fetchRow( $res );
1491                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1492                 }
1493
1494                 return $rows;
1495         }
1496
1497         /**
1498          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1499          * It's only slightly flawed. Don't use for anything important.
1500          *
1501          * @param string $sql A SQL Query
1502          *
1503          * @return string
1504          */
1505         protected static function generalizeSQL( $sql ) {
1506                 # This does the same as the regexp below would do, but in such a way
1507                 # as to avoid crashing php on some large strings.
1508                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1509
1510                 $sql = str_replace( "\\\\", '', $sql );
1511                 $sql = str_replace( "\\'", '', $sql );
1512                 $sql = str_replace( "\\\"", '', $sql );
1513                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1514                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1515
1516                 # All newlines, tabs, etc replaced by single space
1517                 $sql = preg_replace( '/\s+/', ' ', $sql );
1518
1519                 # All numbers => N,
1520                 # except the ones surrounded by characters, e.g. l10n
1521                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1522                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1523
1524                 return $sql;
1525         }
1526
1527         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1528                 $info = $this->fieldInfo( $table, $field );
1529
1530                 return (bool)$info;
1531         }
1532
1533         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1534                 if ( !$this->tableExists( $table ) ) {
1535                         return null;
1536                 }
1537
1538                 $info = $this->indexInfo( $table, $index, $fname );
1539                 if ( is_null( $info ) ) {
1540                         return null;
1541                 } else {
1542                         return $info !== false;
1543                 }
1544         }
1545
1546         public function tableExists( $table, $fname = __METHOD__ ) {
1547                 $tableRaw = $this->tableName( $table, 'raw' );
1548                 if ( isset( $this->mSessionTempTables[$tableRaw] ) ) {
1549                         return true; // already known to exist
1550                 }
1551
1552                 $table = $this->tableName( $table );
1553                 $ignoreErrors = true;
1554                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname, $ignoreErrors );
1555
1556                 return (bool)$res;
1557         }
1558
1559         public function indexUnique( $table, $index ) {
1560                 $indexInfo = $this->indexInfo( $table, $index );
1561
1562                 if ( !$indexInfo ) {
1563                         return null;
1564                 }
1565
1566                 return !$indexInfo[0]->Non_unique;
1567         }
1568
1569         /**
1570          * Helper for Database::insert().
1571          *
1572          * @param array $options
1573          * @return string
1574          */
1575         protected function makeInsertOptions( $options ) {
1576                 return implode( ' ', $options );
1577         }
1578
1579         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1580                 # No rows to insert, easy just return now
1581                 if ( !count( $a ) ) {
1582                         return true;
1583                 }
1584
1585                 $table = $this->tableName( $table );
1586
1587                 if ( !is_array( $options ) ) {
1588                         $options = [ $options ];
1589                 }
1590
1591                 $fh = null;
1592                 if ( isset( $options['fileHandle'] ) ) {
1593                         $fh = $options['fileHandle'];
1594                 }
1595                 $options = $this->makeInsertOptions( $options );
1596
1597                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1598                         $multi = true;
1599                         $keys = array_keys( $a[0] );
1600                 } else {
1601                         $multi = false;
1602                         $keys = array_keys( $a );
1603                 }
1604
1605                 $sql = 'INSERT ' . $options .
1606                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1607
1608                 if ( $multi ) {
1609                         $first = true;
1610                         foreach ( $a as $row ) {
1611                                 if ( $first ) {
1612                                         $first = false;
1613                                 } else {
1614                                         $sql .= ',';
1615                                 }
1616                                 $sql .= '(' . $this->makeList( $row ) . ')';
1617                         }
1618                 } else {
1619                         $sql .= '(' . $this->makeList( $a ) . ')';
1620                 }
1621
1622                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1623                         return false;
1624                 } elseif ( $fh !== null ) {
1625                         return true;
1626                 }
1627
1628                 return (bool)$this->query( $sql, $fname );
1629         }
1630
1631         /**
1632          * Make UPDATE options array for Database::makeUpdateOptions
1633          *
1634          * @param array $options
1635          * @return array
1636          */
1637         protected function makeUpdateOptionsArray( $options ) {
1638                 if ( !is_array( $options ) ) {
1639                         $options = [ $options ];
1640                 }
1641
1642                 $opts = [];
1643
1644                 if ( in_array( 'IGNORE', $options ) ) {
1645                         $opts[] = 'IGNORE';
1646                 }
1647
1648                 return $opts;
1649         }
1650
1651         /**
1652          * Make UPDATE options for the Database::update function
1653          *
1654          * @param array $options The options passed to Database::update
1655          * @return string
1656          */
1657         protected function makeUpdateOptions( $options ) {
1658                 $opts = $this->makeUpdateOptionsArray( $options );
1659
1660                 return implode( ' ', $opts );
1661         }
1662
1663         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1664                 $table = $this->tableName( $table );
1665                 $opts = $this->makeUpdateOptions( $options );
1666                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
1667
1668                 if ( $conds !== [] && $conds !== '*' ) {
1669                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
1670                 }
1671
1672                 return (bool)$this->query( $sql, $fname );
1673         }
1674
1675         public function makeList( $a, $mode = self::LIST_COMMA ) {
1676                 if ( !is_array( $a ) ) {
1677                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1678                 }
1679
1680                 $first = true;
1681                 $list = '';
1682
1683                 foreach ( $a as $field => $value ) {
1684                         if ( !$first ) {
1685                                 if ( $mode == self::LIST_AND ) {
1686                                         $list .= ' AND ';
1687                                 } elseif ( $mode == self::LIST_OR ) {
1688                                         $list .= ' OR ';
1689                                 } else {
1690                                         $list .= ',';
1691                                 }
1692                         } else {
1693                                 $first = false;
1694                         }
1695
1696                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
1697                                 $list .= "($value)";
1698                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
1699                                 $list .= "$value";
1700                         } elseif (
1701                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
1702                         ) {
1703                                 // Remove null from array to be handled separately if found
1704                                 $includeNull = false;
1705                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
1706                                         $includeNull = true;
1707                                         unset( $value[$nullKey] );
1708                                 }
1709                                 if ( count( $value ) == 0 && !$includeNull ) {
1710                                         throw new InvalidArgumentException(
1711                                                 __METHOD__ . ": empty input for field $field" );
1712                                 } elseif ( count( $value ) == 0 ) {
1713                                         // only check if $field is null
1714                                         $list .= "$field IS NULL";
1715                                 } else {
1716                                         // IN clause contains at least one valid element
1717                                         if ( $includeNull ) {
1718                                                 // Group subconditions to ensure correct precedence
1719                                                 $list .= '(';
1720                                         }
1721                                         if ( count( $value ) == 1 ) {
1722                                                 // Special-case single values, as IN isn't terribly efficient
1723                                                 // Don't necessarily assume the single key is 0; we don't
1724                                                 // enforce linear numeric ordering on other arrays here.
1725                                                 $value = array_values( $value )[0];
1726                                                 $list .= $field . " = " . $this->addQuotes( $value );
1727                                         } else {
1728                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1729                                         }
1730                                         // if null present in array, append IS NULL
1731                                         if ( $includeNull ) {
1732                                                 $list .= " OR $field IS NULL)";
1733                                         }
1734                                 }
1735                         } elseif ( $value === null ) {
1736                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
1737                                         $list .= "$field IS ";
1738                                 } elseif ( $mode == self::LIST_SET ) {
1739                                         $list .= "$field = ";
1740                                 }
1741                                 $list .= 'NULL';
1742                         } else {
1743                                 if (
1744                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
1745                                 ) {
1746                                         $list .= "$field = ";
1747                                 }
1748                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
1749                         }
1750                 }
1751
1752                 return $list;
1753         }
1754
1755         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1756                 $conds = [];
1757
1758                 foreach ( $data as $base => $sub ) {
1759                         if ( count( $sub ) ) {
1760                                 $conds[] = $this->makeList(
1761                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
1762                                         self::LIST_AND );
1763                         }
1764                 }
1765
1766                 if ( $conds ) {
1767                         return $this->makeList( $conds, self::LIST_OR );
1768                 } else {
1769                         // Nothing to search for...
1770                         return false;
1771                 }
1772         }
1773
1774         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1775                 return $valuename;
1776         }
1777
1778         public function bitNot( $field ) {
1779                 return "(~$field)";
1780         }
1781
1782         public function bitAnd( $fieldLeft, $fieldRight ) {
1783                 return "($fieldLeft & $fieldRight)";
1784         }
1785
1786         public function bitOr( $fieldLeft, $fieldRight ) {
1787                 return "($fieldLeft | $fieldRight)";
1788         }
1789
1790         public function buildConcat( $stringList ) {
1791                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1792         }
1793
1794         public function buildGroupConcatField(
1795                 $delim, $table, $field, $conds = '', $join_conds = []
1796         ) {
1797                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
1798
1799                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
1800         }
1801
1802         public function buildStringCast( $field ) {
1803                 return $field;
1804         }
1805
1806         public function databasesAreIndependent() {
1807                 return false;
1808         }
1809
1810         public function selectDB( $db ) {
1811                 # Stub. Shouldn't cause serious problems if it's not overridden, but
1812                 # if your database engine supports a concept similar to MySQL's
1813                 # databases you may as well.
1814                 $this->mDBname = $db;
1815
1816                 return true;
1817         }
1818
1819         public function getDBname() {
1820                 return $this->mDBname;
1821         }
1822
1823         public function getServer() {
1824                 return $this->mServer;
1825         }
1826
1827         public function tableName( $name, $format = 'quoted' ) {
1828                 # Skip the entire process when we have a string quoted on both ends.
1829                 # Note that we check the end so that we will still quote any use of
1830                 # use of `database`.table. But won't break things if someone wants
1831                 # to query a database table with a dot in the name.
1832                 if ( $this->isQuotedIdentifier( $name ) ) {
1833                         return $name;
1834                 }
1835
1836                 # Lets test for any bits of text that should never show up in a table
1837                 # name. Basically anything like JOIN or ON which are actually part of
1838                 # SQL queries, but may end up inside of the table value to combine
1839                 # sql. Such as how the API is doing.
1840                 # Note that we use a whitespace test rather than a \b test to avoid
1841                 # any remote case where a word like on may be inside of a table name
1842                 # surrounded by symbols which may be considered word breaks.
1843                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1844                         return $name;
1845                 }
1846
1847                 # Split database and table into proper variables.
1848                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
1849
1850                 # Quote $table and apply the prefix if not quoted.
1851                 # $tableName might be empty if this is called from Database::replaceVars()
1852                 $tableName = "{$prefix}{$table}";
1853                 if ( $format === 'quoted'
1854                         && !$this->isQuotedIdentifier( $tableName )
1855                         && $tableName !== ''
1856                 ) {
1857                         $tableName = $this->addIdentifierQuotes( $tableName );
1858                 }
1859
1860                 # Quote $schema and $database and merge them with the table name if needed
1861                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
1862                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
1863
1864                 return $tableName;
1865         }
1866
1867         /**
1868          * Get the table components needed for a query given the currently selected database
1869          *
1870          * @param string $name Table name in the form of db.schema.table, db.table, or table
1871          * @return array (DB name or "" for default, schema name, table prefix, table name)
1872          */
1873         protected function qualifiedTableComponents( $name ) {
1874                 # We reverse the explode so that database.table and table both output the correct table.
1875                 $dbDetails = explode( '.', $name, 3 );
1876                 if ( count( $dbDetails ) == 3 ) {
1877                         list( $database, $schema, $table ) = $dbDetails;
1878                         # We don't want any prefix added in this case
1879                         $prefix = '';
1880                 } elseif ( count( $dbDetails ) == 2 ) {
1881                         list( $database, $table ) = $dbDetails;
1882                         # We don't want any prefix added in this case
1883                         $prefix = '';
1884                         # In dbs that support it, $database may actually be the schema
1885                         # but that doesn't affect any of the functionality here
1886                         $schema = '';
1887                 } else {
1888                         list( $table ) = $dbDetails;
1889                         if ( isset( $this->tableAliases[$table] ) ) {
1890                                 $database = $this->tableAliases[$table]['dbname'];
1891                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
1892                                         ? $this->tableAliases[$table]['schema']
1893                                         : $this->mSchema;
1894                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
1895                                         ? $this->tableAliases[$table]['prefix']
1896                                         : $this->mTablePrefix;
1897                         } else {
1898                                 $database = '';
1899                                 $schema = $this->mSchema; # Default schema
1900                                 $prefix = $this->mTablePrefix; # Default prefix
1901                         }
1902                 }
1903
1904                 return [ $database, $schema, $prefix, $table ];
1905         }
1906
1907         /**
1908          * @param string|null $namespace Database or schema
1909          * @param string $relation Name of table, view, sequence, etc...
1910          * @param string $format One of (raw, quoted)
1911          * @return string Relation name with quoted and merged $namespace as needed
1912          */
1913         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
1914                 if ( strlen( $namespace ) ) {
1915                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
1916                                 $namespace = $this->addIdentifierQuotes( $namespace );
1917                         }
1918                         $relation = $namespace . '.' . $relation;
1919                 }
1920
1921                 return $relation;
1922         }
1923
1924         public function tableNames() {
1925                 $inArray = func_get_args();
1926                 $retVal = [];
1927
1928                 foreach ( $inArray as $name ) {
1929                         $retVal[$name] = $this->tableName( $name );
1930                 }
1931
1932                 return $retVal;
1933         }
1934
1935         public function tableNamesN() {
1936                 $inArray = func_get_args();
1937                 $retVal = [];
1938
1939                 foreach ( $inArray as $name ) {
1940                         $retVal[] = $this->tableName( $name );
1941                 }
1942
1943                 return $retVal;
1944         }
1945
1946         /**
1947          * Get an aliased table name
1948          * e.g. tableName AS newTableName
1949          *
1950          * @param string $name Table name, see tableName()
1951          * @param string|bool $alias Alias (optional)
1952          * @return string SQL name for aliased table. Will not alias a table to its own name
1953          */
1954         protected function tableNameWithAlias( $name, $alias = false ) {
1955                 if ( !$alias || $alias == $name ) {
1956                         return $this->tableName( $name );
1957                 } else {
1958                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
1959                 }
1960         }
1961
1962         /**
1963          * Gets an array of aliased table names
1964          *
1965          * @param array $tables [ [alias] => table ]
1966          * @return string[] See tableNameWithAlias()
1967          */
1968         protected function tableNamesWithAlias( $tables ) {
1969                 $retval = [];
1970                 foreach ( $tables as $alias => $table ) {
1971                         if ( is_numeric( $alias ) ) {
1972                                 $alias = $table;
1973                         }
1974                         $retval[] = $this->tableNameWithAlias( $table, $alias );
1975                 }
1976
1977                 return $retval;
1978         }
1979
1980         /**
1981          * Get an aliased field name
1982          * e.g. fieldName AS newFieldName
1983          *
1984          * @param string $name Field name
1985          * @param string|bool $alias Alias (optional)
1986          * @return string SQL name for aliased field. Will not alias a field to its own name
1987          */
1988         protected function fieldNameWithAlias( $name, $alias = false ) {
1989                 if ( !$alias || (string)$alias === (string)$name ) {
1990                         return $name;
1991                 } else {
1992                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
1993                 }
1994         }
1995
1996         /**
1997          * Gets an array of aliased field names
1998          *
1999          * @param array $fields [ [alias] => field ]
2000          * @return string[] See fieldNameWithAlias()
2001          */
2002         protected function fieldNamesWithAlias( $fields ) {
2003                 $retval = [];
2004                 foreach ( $fields as $alias => $field ) {
2005                         if ( is_numeric( $alias ) ) {
2006                                 $alias = $field;
2007                         }
2008                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2009                 }
2010
2011                 return $retval;
2012         }
2013
2014         /**
2015          * Get the aliased table name clause for a FROM clause
2016          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2017          *
2018          * @param array $tables ( [alias] => table )
2019          * @param array $use_index Same as for select()
2020          * @param array $ignore_index Same as for select()
2021          * @param array $join_conds Same as for select()
2022          * @return string
2023          */
2024         protected function tableNamesWithIndexClauseOrJOIN(
2025                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2026         ) {
2027                 $ret = [];
2028                 $retJOIN = [];
2029                 $use_index = (array)$use_index;
2030                 $ignore_index = (array)$ignore_index;
2031                 $join_conds = (array)$join_conds;
2032
2033                 foreach ( $tables as $alias => $table ) {
2034                         if ( !is_string( $alias ) ) {
2035                                 // No alias? Set it equal to the table name
2036                                 $alias = $table;
2037                         }
2038
2039                         if ( is_array( $table ) ) {
2040                                 // A parenthesized group
2041                                 if ( count( $table ) > 1 ) {
2042                                         $joinedTable = '('
2043                                                 . $this->tableNamesWithIndexClauseOrJOIN( $table, $use_index, $ignore_index, $join_conds )
2044                                                 . ')';
2045                                 } else {
2046                                         // Degenerate case
2047                                         $innerTable = reset( $table );
2048                                         $innerAlias = key( $table );
2049                                         $joinedTable = $this->tableNameWithAlias(
2050                                                 $innerTable,
2051                                                 is_string( $innerAlias ) ? $innerAlias : $innerTable
2052                                         );
2053                                 }
2054                         } else {
2055                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2056                         }
2057
2058                         // Is there a JOIN clause for this table?
2059                         if ( isset( $join_conds[$alias] ) ) {
2060                                 list( $joinType, $conds ) = $join_conds[$alias];
2061                                 $tableClause = $joinType;
2062                                 $tableClause .= ' ' . $joinedTable;
2063                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2064                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2065                                         if ( $use != '' ) {
2066                                                 $tableClause .= ' ' . $use;
2067                                         }
2068                                 }
2069                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2070                                         $ignore = $this->ignoreIndexClause(
2071                                                 implode( ',', (array)$ignore_index[$alias] ) );
2072                                         if ( $ignore != '' ) {
2073                                                 $tableClause .= ' ' . $ignore;
2074                                         }
2075                                 }
2076                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2077                                 if ( $on != '' ) {
2078                                         $tableClause .= ' ON (' . $on . ')';
2079                                 }
2080
2081                                 $retJOIN[] = $tableClause;
2082                         } elseif ( isset( $use_index[$alias] ) ) {
2083                                 // Is there an INDEX clause for this table?
2084                                 $tableClause = $joinedTable;
2085                                 $tableClause .= ' ' . $this->useIndexClause(
2086                                                 implode( ',', (array)$use_index[$alias] )
2087                                         );
2088
2089                                 $ret[] = $tableClause;
2090                         } elseif ( isset( $ignore_index[$alias] ) ) {
2091                                 // Is there an INDEX clause for this table?
2092                                 $tableClause = $joinedTable;
2093                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2094                                                 implode( ',', (array)$ignore_index[$alias] )
2095                                         );
2096
2097                                 $ret[] = $tableClause;
2098                         } else {
2099                                 $tableClause = $joinedTable;
2100
2101                                 $ret[] = $tableClause;
2102                         }
2103                 }
2104
2105                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2106                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2107                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2108
2109                 // Compile our final table clause
2110                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2111         }
2112
2113         /**
2114          * Allows for index remapping in queries where this is not consistent across DBMS
2115          *
2116          * @param string $index
2117          * @return string
2118          */
2119         protected function indexName( $index ) {
2120                 return $index;
2121         }
2122
2123         public function addQuotes( $s ) {
2124                 if ( $s instanceof Blob ) {
2125                         $s = $s->fetch();
2126                 }
2127                 if ( $s === null ) {
2128                         return 'NULL';
2129                 } elseif ( is_bool( $s ) ) {
2130                         return (int)$s;
2131                 } else {
2132                         # This will also quote numeric values. This should be harmless,
2133                         # and protects against weird problems that occur when they really
2134                         # _are_ strings such as article titles and string->number->string
2135                         # conversion is not 1:1.
2136                         return "'" . $this->strencode( $s ) . "'";
2137                 }
2138         }
2139
2140         /**
2141          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2142          * MySQL uses `backticks` while basically everything else uses double quotes.
2143          * Since MySQL is the odd one out here the double quotes are our generic
2144          * and we implement backticks in DatabaseMysqlBase.
2145          *
2146          * @param string $s
2147          * @return string
2148          */
2149         public function addIdentifierQuotes( $s ) {
2150                 return '"' . str_replace( '"', '""', $s ) . '"';
2151         }
2152
2153         /**
2154          * Returns if the given identifier looks quoted or not according to
2155          * the database convention for quoting identifiers .
2156          *
2157          * @note Do not use this to determine if untrusted input is safe.
2158          *   A malicious user can trick this function.
2159          * @param string $name
2160          * @return bool
2161          */
2162         public function isQuotedIdentifier( $name ) {
2163                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2164         }
2165
2166         /**
2167          * @param string $s
2168          * @param string $escapeChar
2169          * @return string
2170          */
2171         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2172                 return str_replace( [ $escapeChar, '%', '_' ],
2173                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2174                         $s );
2175         }
2176
2177         public function buildLike() {
2178                 $params = func_get_args();
2179
2180                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2181                         $params = $params[0];
2182                 }
2183
2184                 $s = '';
2185
2186                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2187                 // may escape backslashes, creating problems of double escaping. The `
2188                 // character has good cross-DBMS compatibility, avoiding special operators
2189                 // in MS SQL like ^ and %
2190                 $escapeChar = '`';
2191
2192                 foreach ( $params as $value ) {
2193                         if ( $value instanceof LikeMatch ) {
2194                                 $s .= $value->toString();
2195                         } else {
2196                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2197                         }
2198                 }
2199
2200                 return ' LIKE ' . $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2201         }
2202
2203         public function anyChar() {
2204                 return new LikeMatch( '_' );
2205         }
2206
2207         public function anyString() {
2208                 return new LikeMatch( '%' );
2209         }
2210
2211         public function nextSequenceValue( $seqName ) {
2212                 return null;
2213         }
2214
2215         /**
2216          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2217          * is only needed because a) MySQL must be as efficient as possible due to
2218          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2219          * which index to pick. Anyway, other databases might have different
2220          * indexes on a given table. So don't bother overriding this unless you're
2221          * MySQL.
2222          * @param string $index
2223          * @return string
2224          */
2225         public function useIndexClause( $index ) {
2226                 return '';
2227         }
2228
2229         /**
2230          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2231          * is only needed because a) MySQL must be as efficient as possible due to
2232          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2233          * which index to pick. Anyway, other databases might have different
2234          * indexes on a given table. So don't bother overriding this unless you're
2235          * MySQL.
2236          * @param string $index
2237          * @return string
2238          */
2239         public function ignoreIndexClause( $index ) {
2240                 return '';
2241         }
2242
2243         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2244                 if ( count( $rows ) == 0 ) {
2245                         return;
2246                 }
2247
2248                 // Single row case
2249                 if ( !is_array( reset( $rows ) ) ) {
2250                         $rows = [ $rows ];
2251                 }
2252
2253                 $affectedRowCount = 0;
2254                 foreach ( $rows as $row ) {
2255                         // Delete rows which collide with this one
2256                         $indexWhereClauses = [];
2257                         foreach ( $uniqueIndexes as $index ) {
2258                                 $indexColumns = (array)$index;
2259                                 $indexRowValues = array_intersect_key( $row, array_flip( $indexColumns ) );
2260                                 if ( count( $indexRowValues ) != count( $indexColumns ) ) {
2261                                         throw new DBUnexpectedError(
2262                                                 $this,
2263                                                 'New record does not provide all values for unique key (' .
2264                                                         implode( ', ', $indexColumns ) . ')'
2265                                         );
2266                                 } elseif ( in_array( null, $indexRowValues, true ) ) {
2267                                         throw new DBUnexpectedError(
2268                                                 $this,
2269                                                 'New record has a null value for unique key (' .
2270                                                         implode( ', ', $indexColumns ) . ')'
2271                                         );
2272                                 }
2273                                 $indexWhereClauses[] = $this->makeList( $indexRowValues, LIST_AND );
2274                         }
2275
2276                         if ( $indexWhereClauses ) {
2277                                 $this->delete( $table, $this->makeList( $indexWhereClauses, LIST_OR ), $fname );
2278                                 $affectedRowCount += $this->affectedRows();
2279                         }
2280
2281                         // Now insert the row
2282                         $this->insert( $table, $row, $fname );
2283                         $affectedRowCount += $this->affectedRows();
2284                 }
2285
2286                 $this->affectedRowCount = $affectedRowCount;
2287         }
2288
2289         /**
2290          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2291          * statement.
2292          *
2293          * @param string $table Table name
2294          * @param array|string $rows Row(s) to insert
2295          * @param string $fname Caller function name
2296          *
2297          * @return ResultWrapper
2298          */
2299         protected function nativeReplace( $table, $rows, $fname ) {
2300                 $table = $this->tableName( $table );
2301
2302                 # Single row case
2303                 if ( !is_array( reset( $rows ) ) ) {
2304                         $rows = [ $rows ];
2305                 }
2306
2307                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2308                 $first = true;
2309
2310                 foreach ( $rows as $row ) {
2311                         if ( $first ) {
2312                                 $first = false;
2313                         } else {
2314                                 $sql .= ',';
2315                         }
2316
2317                         $sql .= '(' . $this->makeList( $row ) . ')';
2318                 }
2319
2320                 return $this->query( $sql, $fname );
2321         }
2322
2323         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2324                 $fname = __METHOD__
2325         ) {
2326                 if ( !count( $rows ) ) {
2327                         return true; // nothing to do
2328                 }
2329
2330                 if ( !is_array( reset( $rows ) ) ) {
2331                         $rows = [ $rows ];
2332                 }
2333
2334                 if ( count( $uniqueIndexes ) ) {
2335                         $clauses = []; // list WHERE clauses that each identify a single row
2336                         foreach ( $rows as $row ) {
2337                                 foreach ( $uniqueIndexes as $index ) {
2338                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2339                                         $rowKey = []; // unique key to this row
2340                                         foreach ( $index as $column ) {
2341                                                 $rowKey[$column] = $row[$column];
2342                                         }
2343                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2344                                 }
2345                         }
2346                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2347                 } else {
2348                         $where = false;
2349                 }
2350
2351                 $affectedRowCount = 0;
2352                 $useTrx = !$this->mTrxLevel;
2353                 if ( $useTrx ) {
2354                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2355                 }
2356                 try {
2357                         # Update any existing conflicting row(s)
2358                         if ( $where !== false ) {
2359                                 $ok = $this->update( $table, $set, $where, $fname );
2360                                 $affectedRowCount += $this->affectedRows();
2361                         } else {
2362                                 $ok = true;
2363                         }
2364                         # Now insert any non-conflicting row(s)
2365                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2366                         $affectedRowCount += $this->affectedRows();
2367                 } catch ( Exception $e ) {
2368                         if ( $useTrx ) {
2369                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
2370                         }
2371                         throw $e;
2372                 }
2373                 if ( $useTrx ) {
2374                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2375                 }
2376                 $this->affectedRowCount = $affectedRowCount;
2377
2378                 return $ok;
2379         }
2380
2381         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2382                 $fname = __METHOD__
2383         ) {
2384                 if ( !$conds ) {
2385                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2386                 }
2387
2388                 $delTable = $this->tableName( $delTable );
2389                 $joinTable = $this->tableName( $joinTable );
2390                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2391                 if ( $conds != '*' ) {
2392                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2393                 }
2394                 $sql .= ')';
2395
2396                 $this->query( $sql, $fname );
2397         }
2398
2399         public function textFieldSize( $table, $field ) {
2400                 $table = $this->tableName( $table );
2401                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2402                 $res = $this->query( $sql, __METHOD__ );
2403                 $row = $this->fetchObject( $res );
2404
2405                 $m = [];
2406
2407                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2408                         $size = $m[1];
2409                 } else {
2410                         $size = -1;
2411                 }
2412
2413                 return $size;
2414         }
2415
2416         public function delete( $table, $conds, $fname = __METHOD__ ) {
2417                 if ( !$conds ) {
2418                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2419                 }
2420
2421                 $table = $this->tableName( $table );
2422                 $sql = "DELETE FROM $table";
2423
2424                 if ( $conds != '*' ) {
2425                         if ( is_array( $conds ) ) {
2426                                 $conds = $this->makeList( $conds, self::LIST_AND );
2427                         }
2428                         $sql .= ' WHERE ' . $conds;
2429                 }
2430
2431                 return $this->query( $sql, $fname );
2432         }
2433
2434         public function insertSelect(
2435                 $destTable, $srcTable, $varMap, $conds,
2436                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2437         ) {
2438                 if ( $this->cliMode ) {
2439                         // For massive migrations with downtime, we don't want to select everything
2440                         // into memory and OOM, so do all this native on the server side if possible.
2441                         return $this->nativeInsertSelect(
2442                                 $destTable,
2443                                 $srcTable,
2444                                 $varMap,
2445                                 $conds,
2446                                 $fname,
2447                                 $insertOptions,
2448                                 $selectOptions,
2449                                 $selectJoinConds
2450                         );
2451                 }
2452
2453                 return $this->nonNativeInsertSelect(
2454                         $destTable,
2455                         $srcTable,
2456                         $varMap,
2457                         $conds,
2458                         $fname,
2459                         $insertOptions,
2460                         $selectOptions,
2461                         $selectJoinConds
2462                 );
2463         }
2464
2465         /**
2466          * Implementation of insertSelect() based on select() and insert()
2467          *
2468          * @see IDatabase::insertSelect()
2469          * @since 1.30
2470          * @param string $destTable
2471          * @param string|array $srcTable
2472          * @param array $varMap
2473          * @param array $conds
2474          * @param string $fname
2475          * @param array $insertOptions
2476          * @param array $selectOptions
2477          * @param array $selectJoinConds
2478          * @return bool
2479          */
2480         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2481                 $fname = __METHOD__,
2482                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2483         ) {
2484                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
2485                 // on only the master (without needing row-based-replication). It also makes it easy to
2486                 // know how big the INSERT is going to be.
2487                 $fields = [];
2488                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
2489                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
2490                 }
2491                 $selectOptions[] = 'FOR UPDATE';
2492                 $res = $this->select(
2493                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
2494                 );
2495                 if ( !$res ) {
2496                         return false;
2497                 }
2498
2499                 $rows = [];
2500                 foreach ( $res as $row ) {
2501                         $rows[] = (array)$row;
2502                 }
2503
2504                 return $this->insert( $destTable, $rows, $fname, $insertOptions );
2505         }
2506
2507         /**
2508          * Native server-side implementation of insertSelect() for situations where
2509          * we don't want to select everything into memory
2510          *
2511          * @see IDatabase::insertSelect()
2512          * @param string $destTable
2513          * @param string|array $srcTable
2514          * @param array $varMap
2515          * @param array $conds
2516          * @param string $fname
2517          * @param array $insertOptions
2518          * @param array $selectOptions
2519          * @param array $selectJoinConds
2520          * @return bool
2521          */
2522         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2523                 $fname = __METHOD__,
2524                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2525         ) {
2526                 $destTable = $this->tableName( $destTable );
2527
2528                 if ( !is_array( $insertOptions ) ) {
2529                         $insertOptions = [ $insertOptions ];
2530                 }
2531
2532                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2533
2534                 $selectSql = $this->selectSQLText(
2535                         $srcTable,
2536                         array_values( $varMap ),
2537                         $conds,
2538                         $fname,
2539                         $selectOptions,
2540                         $selectJoinConds
2541                 );
2542
2543                 $sql = "INSERT $insertOptions" .
2544                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
2545                         $selectSql;
2546
2547                 return $this->query( $sql, $fname );
2548         }
2549
2550         /**
2551          * Construct a LIMIT query with optional offset. This is used for query
2552          * pages. The SQL should be adjusted so that only the first $limit rows
2553          * are returned. If $offset is provided as well, then the first $offset
2554          * rows should be discarded, and the next $limit rows should be returned.
2555          * If the result of the query is not ordered, then the rows to be returned
2556          * are theoretically arbitrary.
2557          *
2558          * $sql is expected to be a SELECT, if that makes a difference.
2559          *
2560          * The version provided by default works in MySQL and SQLite. It will very
2561          * likely need to be overridden for most other DBMSes.
2562          *
2563          * @param string $sql SQL query we will append the limit too
2564          * @param int $limit The SQL limit
2565          * @param int|bool $offset The SQL offset (default false)
2566          * @throws DBUnexpectedError
2567          * @return string
2568          */
2569         public function limitResult( $sql, $limit, $offset = false ) {
2570                 if ( !is_numeric( $limit ) ) {
2571                         throw new DBUnexpectedError( $this,
2572                                 "Invalid non-numeric limit passed to limitResult()\n" );
2573                 }
2574
2575                 return "$sql LIMIT "
2576                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2577                 . "{$limit} ";
2578         }
2579
2580         public function unionSupportsOrderAndLimit() {
2581                 return true; // True for almost every DB supported
2582         }
2583
2584         public function unionQueries( $sqls, $all ) {
2585                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2586
2587                 return '(' . implode( $glue, $sqls ) . ')';
2588         }
2589
2590         public function unionConditionPermutations(
2591                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
2592                 $options = [], $join_conds = []
2593         ) {
2594                 // First, build the Cartesian product of $permute_conds
2595                 $conds = [ [] ];
2596                 foreach ( $permute_conds as $field => $values ) {
2597                         if ( !$values ) {
2598                                 // Skip empty $values
2599                                 continue;
2600                         }
2601                         $values = array_unique( $values ); // For sanity
2602                         $newConds = [];
2603                         foreach ( $conds as $cond ) {
2604                                 foreach ( $values as $value ) {
2605                                         $cond[$field] = $value;
2606                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
2607                                 }
2608                         }
2609                         $conds = $newConds;
2610                 }
2611
2612                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
2613
2614                 // If there's just one condition and no subordering, hand off to
2615                 // selectSQLText directly.
2616                 if ( count( $conds ) === 1 &&
2617                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
2618                 ) {
2619                         return $this->selectSQLText(
2620                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
2621                         );
2622                 }
2623
2624                 // Otherwise, we need to pull out the order and limit to apply after
2625                 // the union. Then build the SQL queries for each set of conditions in
2626                 // $conds. Then union them together (using UNION ALL, because the
2627                 // product *should* already be distinct).
2628                 $orderBy = $this->makeOrderBy( $options );
2629                 $limit = isset( $options['LIMIT'] ) ? $options['LIMIT'] : null;
2630                 $offset = isset( $options['OFFSET'] ) ? $options['OFFSET'] : false;
2631                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
2632                 if ( !$this->unionSupportsOrderAndLimit() ) {
2633                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
2634                 } else {
2635                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
2636                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
2637                         }
2638                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
2639                                 // We need to increase the limit by the offset rather than
2640                                 // using the offset directly, otherwise it'll skip incorrectly
2641                                 // in the subqueries.
2642                                 $options['LIMIT'] = $limit + $offset;
2643                                 unset( $options['OFFSET'] );
2644                         }
2645                 }
2646
2647                 $sqls = [];
2648                 foreach ( $conds as $cond ) {
2649                         $sqls[] = $this->selectSQLText(
2650                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
2651                         );
2652                 }
2653                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
2654                 if ( $limit !== null ) {
2655                         $sql = $this->limitResult( $sql, $limit, $offset );
2656                 }
2657
2658                 return $sql;
2659         }
2660
2661         public function conditional( $cond, $trueVal, $falseVal ) {
2662                 if ( is_array( $cond ) ) {
2663                         $cond = $this->makeList( $cond, self::LIST_AND );
2664                 }
2665
2666                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2667         }
2668
2669         public function strreplace( $orig, $old, $new ) {
2670                 return "REPLACE({$orig}, {$old}, {$new})";
2671         }
2672
2673         public function getServerUptime() {
2674                 return 0;
2675         }
2676
2677         public function wasDeadlock() {
2678                 return false;
2679         }
2680
2681         public function wasLockTimeout() {
2682                 return false;
2683         }
2684
2685         public function wasErrorReissuable() {
2686                 return false;
2687         }
2688
2689         public function wasReadOnlyError() {
2690                 return false;
2691         }
2692
2693         /**
2694          * Do not use this method outside of Database/DBError classes
2695          *
2696          * @param int|string $errno
2697          * @return bool Whether the given query error was a connection drop
2698          */
2699         public function wasConnectionError( $errno ) {
2700                 return false;
2701         }
2702
2703         public function deadlockLoop() {
2704                 $args = func_get_args();
2705                 $function = array_shift( $args );
2706                 $tries = self::DEADLOCK_TRIES;
2707
2708                 $this->begin( __METHOD__ );
2709
2710                 $retVal = null;
2711                 /** @var Exception $e */
2712                 $e = null;
2713                 do {
2714                         try {
2715                                 $retVal = call_user_func_array( $function, $args );
2716                                 break;
2717                         } catch ( DBQueryError $e ) {
2718                                 if ( $this->wasDeadlock() ) {
2719                                         // Retry after a randomized delay
2720                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
2721                                 } else {
2722                                         // Throw the error back up
2723                                         throw $e;
2724                                 }
2725                         }
2726                 } while ( --$tries > 0 );
2727
2728                 if ( $tries <= 0 ) {
2729                         // Too many deadlocks; give up
2730                         $this->rollback( __METHOD__ );
2731                         throw $e;
2732                 } else {
2733                         $this->commit( __METHOD__ );
2734
2735                         return $retVal;
2736                 }
2737         }
2738
2739         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2740                 # Real waits are implemented in the subclass.
2741                 return 0;
2742         }
2743
2744         public function getReplicaPos() {
2745                 # Stub
2746                 return false;
2747         }
2748
2749         public function getMasterPos() {
2750                 # Stub
2751                 return false;
2752         }
2753
2754         public function serverIsReadOnly() {
2755                 return false;
2756         }
2757
2758         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
2759                 if ( !$this->mTrxLevel ) {
2760                         throw new DBUnexpectedError( $this, "No transaction is active." );
2761                 }
2762                 $this->mTrxEndCallbacks[] = [ $callback, $fname ];
2763         }
2764
2765         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
2766                 $this->mTrxIdleCallbacks[] = [ $callback, $fname ];
2767                 if ( !$this->mTrxLevel ) {
2768                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
2769                 }
2770         }
2771
2772         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
2773                 if ( $this->mTrxLevel || $this->getFlag( self::DBO_TRX ) ) {
2774                         // As long as DBO_TRX is set, writes will accumulate until the load balancer issues
2775                         // an implicit commit of all peer databases. This is true even if a transaction has
2776                         // not yet been triggered by writes; make sure $callback runs *after* any such writes.
2777                         $this->mTrxPreCommitCallbacks[] = [ $callback, $fname ];
2778                 } else {
2779                         // No transaction is active nor will start implicitly, so make one for this callback
2780                         $this->startAtomic( __METHOD__ );
2781                         try {
2782                                 call_user_func( $callback );
2783                                 $this->endAtomic( __METHOD__ );
2784                         } catch ( Exception $e ) {
2785                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2786                                 throw $e;
2787                         }
2788                 }
2789         }
2790
2791         final public function setTransactionListener( $name, callable $callback = null ) {
2792                 if ( $callback ) {
2793                         $this->mTrxRecurringCallbacks[$name] = $callback;
2794                 } else {
2795                         unset( $this->mTrxRecurringCallbacks[$name] );
2796                 }
2797         }
2798
2799         /**
2800          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
2801          *
2802          * This method should not be used outside of Database/LoadBalancer
2803          *
2804          * @param bool $suppress
2805          * @since 1.28
2806          */
2807         final public function setTrxEndCallbackSuppression( $suppress ) {
2808                 $this->mTrxEndCallbacksSuppressed = $suppress;
2809         }
2810
2811         /**
2812          * Actually run and consume any "on transaction idle/resolution" callbacks.
2813          *
2814          * This method should not be used outside of Database/LoadBalancer
2815          *
2816          * @param int $trigger IDatabase::TRIGGER_* constant
2817          * @since 1.20
2818          * @throws Exception
2819          */
2820         public function runOnTransactionIdleCallbacks( $trigger ) {
2821                 if ( $this->mTrxEndCallbacksSuppressed ) {
2822                         return;
2823                 }
2824
2825                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
2826                 /** @var Exception $e */
2827                 $e = null; // first exception
2828                 do { // callbacks may add callbacks :)
2829                         $callbacks = array_merge(
2830                                 $this->mTrxIdleCallbacks,
2831                                 $this->mTrxEndCallbacks // include "transaction resolution" callbacks
2832                         );
2833                         $this->mTrxIdleCallbacks = []; // consumed (and recursion guard)
2834                         $this->mTrxEndCallbacks = []; // consumed (recursion guard)
2835                         foreach ( $callbacks as $callback ) {
2836                                 try {
2837                                         list( $phpCallback ) = $callback;
2838                                         $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
2839                                         call_user_func_array( $phpCallback, [ $trigger ] );
2840                                         if ( $autoTrx ) {
2841                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
2842                                         } else {
2843                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
2844                                         }
2845                                 } catch ( Exception $ex ) {
2846                                         call_user_func( $this->errorLogger, $ex );
2847                                         $e = $e ?: $ex;
2848                                         // Some callbacks may use startAtomic/endAtomic, so make sure
2849                                         // their transactions are ended so other callbacks don't fail
2850                                         if ( $this->trxLevel() ) {
2851                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2852                                         }
2853                                 }
2854                         }
2855                 } while ( count( $this->mTrxIdleCallbacks ) );
2856
2857                 if ( $e instanceof Exception ) {
2858                         throw $e; // re-throw any first exception
2859                 }
2860         }
2861
2862         /**
2863          * Actually run and consume any "on transaction pre-commit" callbacks.
2864          *
2865          * This method should not be used outside of Database/LoadBalancer
2866          *
2867          * @since 1.22
2868          * @throws Exception
2869          */
2870         public function runOnTransactionPreCommitCallbacks() {
2871                 $e = null; // first exception
2872                 do { // callbacks may add callbacks :)
2873                         $callbacks = $this->mTrxPreCommitCallbacks;
2874                         $this->mTrxPreCommitCallbacks = []; // consumed (and recursion guard)
2875                         foreach ( $callbacks as $callback ) {
2876                                 try {
2877                                         list( $phpCallback ) = $callback;
2878                                         call_user_func( $phpCallback );
2879                                 } catch ( Exception $ex ) {
2880                                         call_user_func( $this->errorLogger, $ex );
2881                                         $e = $e ?: $ex;
2882                                 }
2883                         }
2884                 } while ( count( $this->mTrxPreCommitCallbacks ) );
2885
2886                 if ( $e instanceof Exception ) {
2887                         throw $e; // re-throw any first exception
2888                 }
2889         }
2890
2891         /**
2892          * Actually run any "transaction listener" callbacks.
2893          *
2894          * This method should not be used outside of Database/LoadBalancer
2895          *
2896          * @param int $trigger IDatabase::TRIGGER_* constant
2897          * @throws Exception
2898          * @since 1.20
2899          */
2900         public function runTransactionListenerCallbacks( $trigger ) {
2901                 if ( $this->mTrxEndCallbacksSuppressed ) {
2902                         return;
2903                 }
2904
2905                 /** @var Exception $e */
2906                 $e = null; // first exception
2907
2908                 foreach ( $this->mTrxRecurringCallbacks as $phpCallback ) {
2909                         try {
2910                                 $phpCallback( $trigger, $this );
2911                         } catch ( Exception $ex ) {
2912                                 call_user_func( $this->errorLogger, $ex );
2913                                 $e = $e ?: $ex;
2914                         }
2915                 }
2916
2917                 if ( $e instanceof Exception ) {
2918                         throw $e; // re-throw any first exception
2919                 }
2920         }
2921
2922         final public function startAtomic( $fname = __METHOD__ ) {
2923                 if ( !$this->mTrxLevel ) {
2924                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2925                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
2926                         // in all changes being in one transaction to keep requests transactional.
2927                         if ( !$this->getFlag( self::DBO_TRX ) ) {
2928                                 $this->mTrxAutomaticAtomic = true;
2929                         }
2930                 }
2931
2932                 $this->mTrxAtomicLevels[] = $fname;
2933         }
2934
2935         final public function endAtomic( $fname = __METHOD__ ) {
2936                 if ( !$this->mTrxLevel ) {
2937                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
2938                 }
2939                 if ( !$this->mTrxAtomicLevels ||
2940                         array_pop( $this->mTrxAtomicLevels ) !== $fname
2941                 ) {
2942                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
2943                 }
2944
2945                 if ( !$this->mTrxAtomicLevels && $this->mTrxAutomaticAtomic ) {
2946                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2947                 }
2948         }
2949
2950         final public function doAtomicSection( $fname, callable $callback ) {
2951                 $this->startAtomic( $fname );
2952                 try {
2953                         $res = call_user_func_array( $callback, [ $this, $fname ] );
2954                 } catch ( Exception $e ) {
2955                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2956                         throw $e;
2957                 }
2958                 $this->endAtomic( $fname );
2959
2960                 return $res;
2961         }
2962
2963         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
2964                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
2965                 if ( $this->mTrxLevel ) {
2966                         if ( $this->mTrxAtomicLevels ) {
2967                                 $levels = implode( ', ', $this->mTrxAtomicLevels );
2968                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
2969                                 throw new DBUnexpectedError( $this, $msg );
2970                         } elseif ( !$this->mTrxAutomatic ) {
2971                                 $msg = "$fname: Explicit transaction already active (from {$this->mTrxFname}).";
2972                                 throw new DBUnexpectedError( $this, $msg );
2973                         } else {
2974                                 // @TODO: make this an exception at some point
2975                                 $msg = "$fname: Implicit transaction already active (from {$this->mTrxFname}).";
2976                                 $this->queryLogger->error( $msg );
2977                                 return; // join the main transaction set
2978                         }
2979                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
2980                         // @TODO: make this an exception at some point
2981                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
2982                         $this->queryLogger->error( $msg );
2983                         return; // let any writes be in the main transaction
2984                 }
2985
2986                 // Avoid fatals if close() was called
2987                 $this->assertOpen();
2988
2989                 $this->doBegin( $fname );
2990                 $this->mTrxTimestamp = microtime( true );
2991                 $this->mTrxFname = $fname;
2992                 $this->mTrxDoneWrites = false;
2993                 $this->mTrxAutomaticAtomic = false;
2994                 $this->mTrxAtomicLevels = [];
2995                 $this->mTrxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
2996                 $this->mTrxWriteDuration = 0.0;
2997                 $this->mTrxWriteQueryCount = 0;
2998                 $this->mTrxWriteAffectedRows = 0;
2999                 $this->mTrxWriteAdjDuration = 0.0;
3000                 $this->mTrxWriteAdjQueryCount = 0;
3001                 $this->mTrxWriteCallers = [];
3002                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
3003                 // Get an estimate of the replica DB lag before then, treating estimate staleness
3004                 // as lag itself just to be safe
3005                 $status = $this->getApproximateLagStatus();
3006                 $this->mTrxReplicaLag = $status['lag'] + ( microtime( true ) - $status['since'] );
3007                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
3008                 // caller will think its OK to muck around with the transaction just because startAtomic()
3009                 // has not yet completed (e.g. setting mTrxAtomicLevels).
3010                 $this->mTrxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
3011         }
3012
3013         /**
3014          * Issues the BEGIN command to the database server.
3015          *
3016          * @see Database::begin()
3017          * @param string $fname
3018          */
3019         protected function doBegin( $fname ) {
3020                 $this->query( 'BEGIN', $fname );
3021                 $this->mTrxLevel = 1;
3022         }
3023
3024         final public function commit( $fname = __METHOD__, $flush = '' ) {
3025                 if ( $this->mTrxLevel && $this->mTrxAtomicLevels ) {
3026                         // There are still atomic sections open. This cannot be ignored
3027                         $levels = implode( ', ', $this->mTrxAtomicLevels );
3028                         throw new DBUnexpectedError(
3029                                 $this,
3030                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3031                         );
3032                 }
3033
3034                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3035                         if ( !$this->mTrxLevel ) {
3036                                 return; // nothing to do
3037                         } elseif ( !$this->mTrxAutomatic ) {
3038                                 throw new DBUnexpectedError(
3039                                         $this,
3040                                         "$fname: Flushing an explicit transaction, getting out of sync."
3041                                 );
3042                         }
3043                 } else {
3044                         if ( !$this->mTrxLevel ) {
3045                                 $this->queryLogger->error(
3046                                         "$fname: No transaction to commit, something got out of sync." );
3047                                 return; // nothing to do
3048                         } elseif ( $this->mTrxAutomatic ) {
3049                                 // @TODO: make this an exception at some point
3050                                 $msg = "$fname: Explicit commit of implicit transaction.";
3051                                 $this->queryLogger->error( $msg );
3052                                 return; // wait for the main transaction set commit round
3053                         }
3054                 }
3055
3056                 // Avoid fatals if close() was called
3057                 $this->assertOpen();
3058
3059                 $this->runOnTransactionPreCommitCallbacks();
3060                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3061                 $this->doCommit( $fname );
3062                 if ( $this->mTrxDoneWrites ) {
3063                         $this->mLastWriteTime = microtime( true );
3064                         $this->trxProfiler->transactionWritingOut(
3065                                 $this->mServer,
3066                                 $this->mDBname,
3067                                 $this->mTrxShortId,
3068                                 $writeTime,
3069                                 $this->mTrxWriteAffectedRows
3070                         );
3071                 }
3072
3073                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3074                 $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3075         }
3076
3077         /**
3078          * Issues the COMMIT command to the database server.
3079          *
3080          * @see Database::commit()
3081          * @param string $fname
3082          */
3083         protected function doCommit( $fname ) {
3084                 if ( $this->mTrxLevel ) {
3085                         $this->query( 'COMMIT', $fname );
3086                         $this->mTrxLevel = 0;
3087                 }
3088         }
3089
3090         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3091                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3092                         if ( !$this->mTrxLevel ) {
3093                                 return; // nothing to do
3094                         }
3095                 } else {
3096                         if ( !$this->mTrxLevel ) {
3097                                 $this->queryLogger->error(
3098                                         "$fname: No transaction to rollback, something got out of sync." );
3099                                 return; // nothing to do
3100                         } elseif ( $this->getFlag( self::DBO_TRX ) ) {
3101                                 throw new DBUnexpectedError(
3102                                         $this,
3103                                         "$fname: Expected mass rollback of all peer databases (DBO_TRX set)."
3104                                 );
3105                         }
3106                 }
3107
3108                 // Avoid fatals if close() was called
3109                 $this->assertOpen();
3110
3111                 $this->doRollback( $fname );
3112                 $this->mTrxAtomicLevels = [];
3113                 if ( $this->mTrxDoneWrites ) {
3114                         $this->trxProfiler->transactionWritingOut(
3115                                 $this->mServer,
3116                                 $this->mDBname,
3117                                 $this->mTrxShortId
3118                         );
3119                 }
3120
3121                 $this->mTrxIdleCallbacks = []; // clear
3122                 $this->mTrxPreCommitCallbacks = []; // clear
3123                 try {
3124                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
3125                 } catch ( Exception $e ) {
3126                         // already logged; finish and let LoadBalancer move on during mass-rollback
3127                 }
3128                 try {
3129                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
3130                 } catch ( Exception $e ) {
3131                         // already logged; let LoadBalancer move on during mass-rollback
3132                 }
3133         }
3134
3135         /**
3136          * Issues the ROLLBACK command to the database server.
3137          *
3138          * @see Database::rollback()
3139          * @param string $fname
3140          */
3141         protected function doRollback( $fname ) {
3142                 if ( $this->mTrxLevel ) {
3143                         # Disconnects cause rollback anyway, so ignore those errors
3144                         $ignoreErrors = true;
3145                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
3146                         $this->mTrxLevel = 0;
3147                 }
3148         }
3149
3150         public function flushSnapshot( $fname = __METHOD__ ) {
3151                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
3152                         // This only flushes transactions to clear snapshots, not to write data
3153                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3154                         throw new DBUnexpectedError(
3155                                 $this,
3156                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
3157                         );
3158                 }
3159
3160                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3161         }
3162
3163         public function explicitTrxActive() {
3164                 return $this->mTrxLevel && ( $this->mTrxAtomicLevels || !$this->mTrxAutomatic );
3165         }
3166
3167         public function duplicateTableStructure(
3168                 $oldName, $newName, $temporary = false, $fname = __METHOD__
3169         ) {
3170                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3171         }
3172
3173         public function listTables( $prefix = null, $fname = __METHOD__ ) {
3174                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3175         }
3176
3177         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3178                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3179         }
3180
3181         public function timestamp( $ts = 0 ) {
3182                 $t = new ConvertibleTimestamp( $ts );
3183                 // Let errors bubble up to avoid putting garbage in the DB
3184                 return $t->getTimestamp( TS_MW );
3185         }
3186
3187         public function timestampOrNull( $ts = null ) {
3188                 if ( is_null( $ts ) ) {
3189                         return null;
3190                 } else {
3191                         return $this->timestamp( $ts );
3192                 }
3193         }
3194
3195         public function affectedRows() {
3196                 return ( $this->affectedRowCount === null )
3197                         ? $this->fetchAffectedRowCount() // default to driver value
3198                         : $this->affectedRowCount;
3199         }
3200
3201         /**
3202          * @return int Number of retrieved rows according to the driver
3203          */
3204         abstract protected function fetchAffectedRowCount();
3205
3206         /**
3207          * Take the result from a query, and wrap it in a ResultWrapper if
3208          * necessary. Boolean values are passed through as is, to indicate success
3209          * of write queries or failure.
3210          *
3211          * Once upon a time, Database::query() returned a bare MySQL result
3212          * resource, and it was necessary to call this function to convert it to
3213          * a wrapper. Nowadays, raw database objects are never exposed to external
3214          * callers, so this is unnecessary in external code.
3215          *
3216          * @param bool|ResultWrapper|resource|object $result
3217          * @return bool|ResultWrapper
3218          */
3219         protected function resultObject( $result ) {
3220                 if ( !$result ) {
3221                         return false;
3222                 } elseif ( $result instanceof ResultWrapper ) {
3223                         return $result;
3224                 } elseif ( $result === true ) {
3225                         // Successful write query
3226                         return $result;
3227                 } else {
3228                         return new ResultWrapper( $this, $result );
3229                 }
3230         }
3231
3232         public function ping( &$rtt = null ) {
3233                 // Avoid hitting the server if it was hit recently
3234                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
3235                         if ( !func_num_args() || $this->mRTTEstimate > 0 ) {
3236                                 $rtt = $this->mRTTEstimate;
3237                                 return true; // don't care about $rtt
3238                         }
3239                 }
3240
3241                 // This will reconnect if possible or return false if not
3242                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
3243                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
3244                 $this->restoreFlags( self::RESTORE_PRIOR );
3245
3246                 if ( $ok ) {
3247                         $rtt = $this->mRTTEstimate;
3248                 }
3249
3250                 return $ok;
3251         }
3252
3253         /**
3254          * Close existing database connection and open a new connection
3255          *
3256          * @return bool True if new connection is opened successfully, false if error
3257          */
3258         protected function reconnect() {
3259                 $this->closeConnection();
3260                 $this->mOpened = false;
3261                 $this->mConn = false;
3262                 try {
3263                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3264                         $this->lastPing = microtime( true );
3265                         $ok = true;
3266                 } catch ( DBConnectionError $e ) {
3267                         $ok = false;
3268                 }
3269
3270                 return $ok;
3271         }
3272
3273         public function getSessionLagStatus() {
3274                 return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
3275         }
3276
3277         /**
3278          * Get the replica DB lag when the current transaction started
3279          *
3280          * This is useful when transactions might use snapshot isolation
3281          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
3282          * is this lag plus transaction duration. If they don't, it is still
3283          * safe to be pessimistic. This returns null if there is no transaction.
3284          *
3285          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
3286          * @since 1.27
3287          */
3288         protected function getTransactionLagStatus() {
3289                 return $this->mTrxLevel
3290                         ? [ 'lag' => $this->mTrxReplicaLag, 'since' => $this->trxTimestamp() ]
3291                         : null;
3292         }
3293
3294         /**
3295          * Get a replica DB lag estimate for this server
3296          *
3297          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
3298          * @since 1.27
3299          */
3300         protected function getApproximateLagStatus() {
3301                 return [
3302                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
3303                         'since' => microtime( true )
3304                 ];
3305         }
3306
3307         /**
3308          * Merge the result of getSessionLagStatus() for several DBs
3309          * using the most pessimistic values to estimate the lag of
3310          * any data derived from them in combination
3311          *
3312          * This is information is useful for caching modules
3313          *
3314          * @see WANObjectCache::set()
3315          * @see WANObjectCache::getWithSetCallback()
3316          *
3317          * @param IDatabase $db1
3318          * @param IDatabase $db2 [optional]
3319          * @return array Map of values:
3320          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3321          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3322          *   - pending: whether any of the DBs have uncommitted changes
3323          * @throws DBError
3324          * @since 1.27
3325          */
3326         public static function getCacheSetOptions( IDatabase $db1, IDatabase $db2 = null ) {
3327                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3328                 foreach ( func_get_args() as $db ) {
3329                         /** @var IDatabase $db */
3330                         $status = $db->getSessionLagStatus();
3331                         if ( $status['lag'] === false ) {
3332                                 $res['lag'] = false;
3333                         } elseif ( $res['lag'] !== false ) {
3334                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3335                         }
3336                         $res['since'] = min( $res['since'], $status['since'] );
3337                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3338                 }
3339
3340                 return $res;
3341         }
3342
3343         public function getLag() {
3344                 return 0;
3345         }
3346
3347         public function maxListLen() {
3348                 return 0;
3349         }
3350
3351         public function encodeBlob( $b ) {
3352                 return $b;
3353         }
3354
3355         public function decodeBlob( $b ) {
3356                 if ( $b instanceof Blob ) {
3357                         $b = $b->fetch();
3358                 }
3359                 return $b;
3360         }
3361
3362         public function setSessionOptions( array $options ) {
3363         }
3364
3365         public function sourceFile(
3366                 $filename,
3367                 callable $lineCallback = null,
3368                 callable $resultCallback = null,
3369                 $fname = false,
3370                 callable $inputCallback = null
3371         ) {
3372                 Wikimedia\suppressWarnings();
3373                 $fp = fopen( $filename, 'r' );
3374                 Wikimedia\restoreWarnings();
3375
3376                 if ( false === $fp ) {
3377                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
3378                 }
3379
3380                 if ( !$fname ) {
3381                         $fname = __METHOD__ . "( $filename )";
3382                 }
3383
3384                 try {
3385                         $error = $this->sourceStream(
3386                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3387                 } catch ( Exception $e ) {
3388                         fclose( $fp );
3389                         throw $e;
3390                 }
3391
3392                 fclose( $fp );
3393
3394                 return $error;
3395         }
3396
3397         public function setSchemaVars( $vars ) {
3398                 $this->mSchemaVars = $vars;
3399         }
3400
3401         public function sourceStream(
3402                 $fp,
3403                 callable $lineCallback = null,
3404                 callable $resultCallback = null,
3405                 $fname = __METHOD__,
3406                 callable $inputCallback = null
3407         ) {
3408                 $delimiterReset = new ScopedCallback(
3409                         function ( $delimiter ) {
3410                                 $this->delimiter = $delimiter;
3411                         },
3412                         [ $this->delimiter ]
3413                 );
3414                 $cmd = '';
3415
3416                 while ( !feof( $fp ) ) {
3417                         if ( $lineCallback ) {
3418                                 call_user_func( $lineCallback );
3419                         }
3420
3421                         $line = trim( fgets( $fp ) );
3422
3423                         if ( $line == '' ) {
3424                                 continue;
3425                         }
3426
3427                         if ( '-' == $line[0] && '-' == $line[1] ) {
3428                                 continue;
3429                         }
3430
3431                         if ( $cmd != '' ) {
3432                                 $cmd .= ' ';
3433                         }
3434
3435                         $done = $this->streamStatementEnd( $cmd, $line );
3436
3437                         $cmd .= "$line\n";
3438
3439                         if ( $done || feof( $fp ) ) {
3440                                 $cmd = $this->replaceVars( $cmd );
3441
3442                                 if ( $inputCallback ) {
3443                                         $callbackResult = call_user_func( $inputCallback, $cmd );
3444
3445                                         if ( is_string( $callbackResult ) || !$callbackResult ) {
3446                                                 $cmd = $callbackResult;
3447                                         }
3448                                 }
3449
3450                                 if ( $cmd ) {
3451                                         $res = $this->query( $cmd, $fname );
3452
3453                                         if ( $resultCallback ) {
3454                                                 call_user_func( $resultCallback, $res, $this );
3455                                         }
3456
3457                                         if ( false === $res ) {
3458                                                 $err = $this->lastError();
3459
3460                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3461                                         }
3462                                 }
3463                                 $cmd = '';
3464                         }
3465                 }
3466
3467                 ScopedCallback::consume( $delimiterReset );
3468                 return true;
3469         }
3470
3471         /**
3472          * Called by sourceStream() to check if we've reached a statement end
3473          *
3474          * @param string &$sql SQL assembled so far
3475          * @param string &$newLine New line about to be added to $sql
3476          * @return bool Whether $newLine contains end of the statement
3477          */
3478         public function streamStatementEnd( &$sql, &$newLine ) {
3479                 if ( $this->delimiter ) {
3480                         $prev = $newLine;
3481                         $newLine = preg_replace(
3482                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3483                         if ( $newLine != $prev ) {
3484                                 return true;
3485                         }
3486                 }
3487
3488                 return false;
3489         }
3490
3491         /**
3492          * Database independent variable replacement. Replaces a set of variables
3493          * in an SQL statement with their contents as given by $this->getSchemaVars().
3494          *
3495          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3496          *
3497          * - '{$var}' should be used for text and is passed through the database's
3498          *   addQuotes method.
3499          * - `{$var}` should be used for identifiers (e.g. table and database names).
3500          *   It is passed through the database's addIdentifierQuotes method which
3501          *   can be overridden if the database uses something other than backticks.
3502          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
3503          *   database's tableName method.
3504          * - / *i* / passes the name that follows through the database's indexName method.
3505          * - In all other cases, / *$var* / is left unencoded. Except for table options,
3506          *   its use should be avoided. In 1.24 and older, string encoding was applied.
3507          *
3508          * @param string $ins SQL statement to replace variables in
3509          * @return string The new SQL statement with variables replaced
3510          */
3511         protected function replaceVars( $ins ) {
3512                 $vars = $this->getSchemaVars();
3513                 return preg_replace_callback(
3514                         '!
3515                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
3516                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
3517                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
3518                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
3519                         !x',
3520                         function ( $m ) use ( $vars ) {
3521                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
3522                                 // check for both nonexistent keys *and* the empty string.
3523                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
3524                                         if ( $m[1] === 'i' ) {
3525                                                 return $this->indexName( $m[2] );
3526                                         } else {
3527                                                 return $this->tableName( $m[2] );
3528                                         }
3529                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
3530                                         return $this->addQuotes( $vars[$m[3]] );
3531                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
3532                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
3533                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
3534                                         return $vars[$m[5]];
3535                                 } else {
3536                                         return $m[0];
3537                                 }
3538                         },
3539                         $ins
3540                 );
3541         }
3542
3543         /**
3544          * Get schema variables. If none have been set via setSchemaVars(), then
3545          * use some defaults from the current object.
3546          *
3547          * @return array
3548          */
3549         protected function getSchemaVars() {
3550                 if ( $this->mSchemaVars ) {
3551                         return $this->mSchemaVars;
3552                 } else {
3553                         return $this->getDefaultSchemaVars();
3554                 }
3555         }
3556
3557         /**
3558          * Get schema variables to use if none have been set via setSchemaVars().
3559          *
3560          * Override this in derived classes to provide variables for tables.sql
3561          * and SQL patch files.
3562          *
3563          * @return array
3564          */
3565         protected function getDefaultSchemaVars() {
3566                 return [];
3567         }
3568
3569         public function lockIsFree( $lockName, $method ) {
3570                 return true;
3571         }
3572
3573         public function lock( $lockName, $method, $timeout = 5 ) {
3574                 $this->mNamedLocksHeld[$lockName] = 1;
3575
3576                 return true;
3577         }
3578
3579         public function unlock( $lockName, $method ) {
3580                 unset( $this->mNamedLocksHeld[$lockName] );
3581
3582                 return true;
3583         }
3584
3585         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
3586                 if ( $this->writesOrCallbacksPending() ) {
3587                         // This only flushes transactions to clear snapshots, not to write data
3588                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3589                         throw new DBUnexpectedError(
3590                                 $this,
3591                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
3592                         );
3593                 }
3594
3595                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
3596                         return null;
3597                 }
3598
3599                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
3600                         if ( $this->trxLevel() ) {
3601                                 // There is a good chance an exception was thrown, causing any early return
3602                                 // from the caller. Let any error handler get a chance to issue rollback().
3603                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
3604                                 $this->onTransactionResolution(
3605                                         function () use ( $lockKey, $fname ) {
3606                                                 $this->unlock( $lockKey, $fname );
3607                                         },
3608                                         $fname
3609                                 );
3610                         } else {
3611                                 $this->unlock( $lockKey, $fname );
3612                         }
3613                 } );
3614
3615                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3616
3617                 return $unlocker;
3618         }
3619
3620         public function namedLocksEnqueue() {
3621                 return false;
3622         }
3623
3624         public function tableLocksHaveTransactionScope() {
3625                 return true;
3626         }
3627
3628         final public function lockTables( array $read, array $write, $method ) {
3629                 if ( $this->writesOrCallbacksPending() ) {
3630                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
3631                 }
3632
3633                 if ( $this->tableLocksHaveTransactionScope() ) {
3634                         $this->startAtomic( $method );
3635                 }
3636
3637                 return $this->doLockTables( $read, $write, $method );
3638         }
3639
3640         /**
3641          * Helper function for lockTables() that handles the actual table locking
3642          *
3643          * @param array $read Array of tables to lock for read access
3644          * @param array $write Array of tables to lock for write access
3645          * @param string $method Name of caller
3646          * @return true
3647          */
3648         protected function doLockTables( array $read, array $write, $method ) {
3649                 return true;
3650         }
3651
3652         final public function unlockTables( $method ) {
3653                 if ( $this->tableLocksHaveTransactionScope() ) {
3654                         $this->endAtomic( $method );
3655
3656                         return true; // locks released on COMMIT/ROLLBACK
3657                 }
3658
3659                 return $this->doUnlockTables( $method );
3660         }
3661
3662         /**
3663          * Helper function for unlockTables() that handles the actual table unlocking
3664          *
3665          * @param string $method Name of caller
3666          * @return true
3667          */
3668         protected function doUnlockTables( $method ) {
3669                 return true;
3670         }
3671
3672         /**
3673          * Delete a table
3674          * @param string $tableName
3675          * @param string $fName
3676          * @return bool|ResultWrapper
3677          * @since 1.18
3678          */
3679         public function dropTable( $tableName, $fName = __METHOD__ ) {
3680                 if ( !$this->tableExists( $tableName, $fName ) ) {
3681                         return false;
3682                 }
3683                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
3684
3685                 return $this->query( $sql, $fName );
3686         }
3687
3688         public function getInfinity() {
3689                 return 'infinity';
3690         }
3691
3692         public function encodeExpiry( $expiry ) {
3693                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3694                         ? $this->getInfinity()
3695                         : $this->timestamp( $expiry );
3696         }
3697
3698         public function decodeExpiry( $expiry, $format = TS_MW ) {
3699                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
3700                         return 'infinity';
3701                 }
3702
3703                 return ConvertibleTimestamp::convert( $format, $expiry );
3704         }
3705
3706         public function setBigSelects( $value = true ) {
3707                 // no-op
3708         }
3709
3710         public function isReadOnly() {
3711                 return ( $this->getReadOnlyReason() !== false );
3712         }
3713
3714         /**
3715          * @return string|bool Reason this DB is read-only or false if it is not
3716          */
3717         protected function getReadOnlyReason() {
3718                 $reason = $this->getLBInfo( 'readOnlyReason' );
3719
3720                 return is_string( $reason ) ? $reason : false;
3721         }
3722
3723         public function setTableAliases( array $aliases ) {
3724                 $this->tableAliases = $aliases;
3725         }
3726
3727         /**
3728          * @return bool Whether a DB user is required to access the DB
3729          * @since 1.28
3730          */
3731         protected function requiresDatabaseUser() {
3732                 return true;
3733         }
3734
3735         /**
3736          * Get the underlying binding handle, mConn
3737          *
3738          * Makes sure that mConn is set (disconnects and ping() failure can unset it).
3739          * This catches broken callers than catch and ignore disconnection exceptions.
3740          * Unlike checking isOpen(), this is safe to call inside of open().
3741          *
3742          * @return resource|object
3743          * @throws DBUnexpectedError
3744          * @since 1.26
3745          */
3746         protected function getBindingHandle() {
3747                 if ( !$this->mConn ) {
3748                         throw new DBUnexpectedError(
3749                                 $this,
3750                                 'DB connection was already closed or the connection dropped.'
3751                         );
3752                 }
3753
3754                 return $this->mConn;
3755         }
3756
3757         /**
3758          * @since 1.19
3759          * @return string
3760          */
3761         public function __toString() {
3762                 return (string)$this->mConn;
3763         }
3764
3765         /**
3766          * Make sure that copies do not share the same client binding handle
3767          * @throws DBConnectionError
3768          */
3769         public function __clone() {
3770                 $this->connLogger->warning(
3771                         "Cloning " . static::class . " is not recomended; forking connection:\n" .
3772                         ( new RuntimeException() )->getTraceAsString()
3773                 );
3774
3775                 if ( $this->isOpen() ) {
3776                         // Open a new connection resource without messing with the old one
3777                         $this->mOpened = false;
3778                         $this->mConn = false;
3779                         $this->mTrxEndCallbacks = []; // don't copy
3780                         $this->handleSessionLoss(); // no trx or locks anymore
3781                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3782                         $this->lastPing = microtime( true );
3783                 }
3784         }
3785
3786         /**
3787          * Called by serialize. Throw an exception when DB connection is serialized.
3788          * This causes problems on some database engines because the connection is
3789          * not restored on unserialize.
3790          */
3791         public function __sleep() {
3792                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
3793                         'the connection is not restored on wakeup.' );
3794         }
3795
3796         /**
3797          * Run a few simple sanity checks and close dangling connections
3798          */
3799         public function __destruct() {
3800                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
3801                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
3802                 }
3803
3804                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
3805                 if ( $danglingWriters ) {
3806                         $fnames = implode( ', ', $danglingWriters );
3807                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
3808                 }
3809
3810                 if ( $this->mConn ) {
3811                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
3812                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
3813                         Wikimedia\suppressWarnings();
3814                         $this->closeConnection();
3815                         Wikimedia\restoreWarnings();
3816                         $this->mConn = false;
3817                         $this->mOpened = false;
3818                 }
3819         }
3820 }
3821
3822 class_alias( Database::class, 'DatabaseBase' ); // b/c for old name
3823 class_alias( Database::class, 'Database' ); // b/c global alias