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 use Psr\Log\LoggerAwareInterface;
  27 use Psr\Log\LoggerInterface;
  28 use Wikimedia\ScopedCallback;
  29 use Wikimedia\Rdbms\TransactionProfiler;
  30 use Wikimedia\Rdbms\LikeMatch;
  31 use Wikimedia\Rdbms\DatabaseDomain;
  32 use Wikimedia\Rdbms\DBMasterPos;
  33
  34 /**
  35  * Relational database abstraction object
  36  *
  37  * @ingroup Database
  38  * @since 1.28
  39  */
  40 abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAwareInterface {
  41         /** Number of times to re-try an operation in case of deadlock */
  42         const DEADLOCK_TRIES = 4;
  43         /** Minimum time to wait before retry, in microseconds */
  44         const DEADLOCK_DELAY_MIN = 500000;
  45         /** Maximum time to wait before retry */
  46         const DEADLOCK_DELAY_MAX = 1500000;
  47
  48         /** How long before it is worth doing a dummy query to test the connection */
  49         const PING_TTL = 1.0;
  50         const PING_QUERY = 'SELECT 1 AS ping';
  51
  52         const TINY_WRITE_SEC = .010;
  53         const SLOW_WRITE_SEC = .500;
  54         const SMALL_WRITE_ROWS = 100;
  55
  56         /** @var string SQL query */
  57         protected $mLastQuery = '';
  58         /** @var float|bool UNIX timestamp of last write query */
  59         protected $mLastWriteTime = false;
  60         /** @var string|bool */
  61         protected $mPHPError = false;
  62         /** @var string */
  63         protected $mServer;
  64         /** @var string */
  65         protected $mUser;
  66         /** @var string */
  67         protected $mPassword;
  68         /** @var string */
  69         protected $mDBname;
  70         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  71         protected $tableAliases = [];
  72         /** @var bool Whether this PHP instance is for a CLI script */
  73         protected $cliMode;
  74         /** @var string Agent name for query profiling */
  75         protected $agent;
  76
  77         /** @var BagOStuff APC cache */
  78         protected $srvCache;
  79         /** @var LoggerInterface */
  80         protected $connLogger;
  81         /** @var LoggerInterface */
  82         protected $queryLogger;
  83         /** @var callback Error logging callback */
  84         protected $errorLogger;
  85
  86         /** @var resource|null Database connection */
  87         protected $mConn = null;
  88         /** @var bool */
  89         protected $mOpened = false;
  90
  91         /** @var array[] List of (callable, method name) */
  92         protected $mTrxIdleCallbacks = [];
  93         /** @var array[] List of (callable, method name) */
  94         protected $mTrxPreCommitCallbacks = [];
  95         /** @var array[] List of (callable, method name) */
  96         protected $mTrxEndCallbacks = [];
  97         /** @var callable[] Map of (name => callable) */
  98         protected $mTrxRecurringCallbacks = [];
  99         /** @var bool Whether to suppress triggering of transaction end callbacks */
 100         protected $mTrxEndCallbacksSuppressed = false;
 101
 102         /** @var string */
 103         protected $mTablePrefix = '';
 104         /** @var string */
 105         protected $mSchema = '';
 106         /** @var integer */
 107         protected $mFlags;
 108         /** @var array */
 109         protected $mLBInfo = [];
 110         /** @var bool|null */
 111         protected $mDefaultBigSelects = null;
 112         /** @var array|bool */
 113         protected $mSchemaVars = false;
 114         /** @var array */
 115         protected $mSessionVars = [];
 116         /** @var array|null */
 117         protected $preparedArgs;
 118         /** @var string|bool|null Stashed value of html_errors INI setting */
 119         protected $htmlErrors;
 120         /** @var string */
 121         protected $delimiter = ';';
 122         /** @var DatabaseDomain */
 123         protected $currentDomain;
 124
 125         /**
 126          * Either 1 if a transaction is active or 0 otherwise.
 127          * The other Trx fields may not be meaningfull if this is 0.
 128          *
 129          * @var int
 130          */
 131         protected $mTrxLevel = 0;
 132         /**
 133          * Either a short hexidecimal string if a transaction is active or ""
 134          *
 135          * @var string
 136          * @see Database::mTrxLevel
 137          */
 138         protected $mTrxShortId = '';
 139         /**
 140          * The UNIX time that the transaction started. Callers can assume that if
 141          * snapshot isolation is used, then the data is *at least* up to date to that
 142          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 143          *
 144          * @var float|null
 145          * @see Database::mTrxLevel
 146          */
 147         private $mTrxTimestamp = null;
 148         /** @var float Lag estimate at the time of BEGIN */
 149         private $mTrxReplicaLag = null;
 150         /**
 151          * Remembers the function name given for starting the most recent transaction via begin().
 152          * Used to provide additional context for error reporting.
 153          *
 154          * @var string
 155          * @see Database::mTrxLevel
 156          */
 157         private $mTrxFname = null;
 158         /**
 159          * Record if possible write queries were done in the last transaction started
 160          *
 161          * @var bool
 162          * @see Database::mTrxLevel
 163          */
 164         private $mTrxDoneWrites = false;
 165         /**
 166          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 167          *
 168          * @var bool
 169          * @see Database::mTrxLevel
 170          */
 171         private $mTrxAutomatic = false;
 172         /**
 173          * Array of levels of atomicity within transactions
 174          *
 175          * @var array
 176          */
 177         private $mTrxAtomicLevels = [];
 178         /**
 179          * Record if the current transaction was started implicitly by Database::startAtomic
 180          *
 181          * @var bool
 182          */
 183         private $mTrxAutomaticAtomic = false;
 184         /**
 185          * Track the write query callers of the current transaction
 186          *
 187          * @var string[]
 188          */
 189         private $mTrxWriteCallers = [];
 190         /**
 191          * @var float Seconds spent in write queries for the current transaction
 192          */
 193         private $mTrxWriteDuration = 0.0;
 194         /**
 195          * @var integer Number of write queries for the current transaction
 196          */
 197         private $mTrxWriteQueryCount = 0;
 198         /**
 199          * @var float Like mTrxWriteQueryCount but excludes lock-bound, easy to replicate, queries
 200          */
 201         private $mTrxWriteAdjDuration = 0.0;
 202         /**
 203          * @var integer Number of write queries counted in mTrxWriteAdjDuration
 204          */
 205         private $mTrxWriteAdjQueryCount = 0;
 206         /**
 207          * @var float RTT time estimate
 208          */
 209         private $mRTTEstimate = 0.0;
 210
 211         /** @var array Map of (name => 1) for locks obtained via lock() */
 212         private $mNamedLocksHeld = [];
 213         /** @var array Map of (table name => 1) for TEMPORARY tables */
 214         protected $mSessionTempTables = [];
 215
 216         /** @var IDatabase|null Lazy handle to the master DB this server replicates from */
 217         private $lazyMasterHandle;
 218
 219         /** @var float UNIX timestamp */
 220         protected $lastPing = 0.0;
 221
 222         /** @var int[] Prior mFlags values */
 223         private $priorFlags = [];
 224
 225         /** @var object|string Class name or object With profileIn/profileOut methods */
 226         protected $profiler;
 227         /** @var TransactionProfiler */
 228         protected $trxProfiler;
 229
 230         /**
 231          * Constructor and database handle and attempt to connect to the DB server
 232          *
 233          * IDatabase classes should not be constructed directly in external
 234          * code. Database::factory() should be used instead.
 235          *
 236          * @param array $params Parameters passed from Database::factory()
 237          */
 238         function __construct( array $params ) {
 239                 $server = $params['host'];
 240                 $user = $params['user'];
 241                 $password = $params['password'];
 242                 $dbName = $params['dbname'];
 243
 244                 $this->mSchema = $params['schema'];
 245                 $this->mTablePrefix = $params['tablePrefix'];
 246
 247                 $this->cliMode = $params['cliMode'];
 248                 // Agent name is added to SQL queries in a comment, so make sure it can't break out
 249                 $this->agent = str_replace( '/', '-', $params['agent'] );
 250
 251                 $this->mFlags = $params['flags'];
 252                 if ( $this->mFlags & self::DBO_DEFAULT ) {
 253                         if ( $this->cliMode ) {
 254                                 $this->mFlags &= ~self::DBO_TRX;
 255                         } else {
 256                                 $this->mFlags |= self::DBO_TRX;
 257                         }
 258                 }
 259
 260                 $this->mSessionVars = $params['variables'];
 261
 262                 $this->srvCache = isset( $params['srvCache'] )
 263                         ? $params['srvCache']
 264                         : new HashBagOStuff();
 265
 266                 $this->profiler = $params['profiler'];
 267                 $this->trxProfiler = $params['trxProfiler'];
 268                 $this->connLogger = $params['connLogger'];
 269                 $this->queryLogger = $params['queryLogger'];
 270                 $this->errorLogger = $params['errorLogger'];
 271
 272                 // Set initial dummy domain until open() sets the final DB/prefix
 273                 $this->currentDomain = DatabaseDomain::newUnspecified();
 274
 275                 if ( $user ) {
 276                         $this->open( $server, $user, $password, $dbName );
 277                 } elseif ( $this->requiresDatabaseUser() ) {
 278                         throw new InvalidArgumentException( "No database user provided." );
 279                 }
 280
 281                 // Set the domain object after open() sets the relevant fields
 282                 if ( $this->mDBname != '' ) {
 283                         // Domains with server scope but a table prefix are not used by IDatabase classes
 284                         $this->currentDomain = new DatabaseDomain( $this->mDBname, null, $this->mTablePrefix );
 285                 }
 286         }
 287
 288         /**
 289          * Construct a Database subclass instance given a database type and parameters
 290          *
 291          * This also connects to the database immediately upon object construction
 292          *
 293          * @param string $dbType A possible DB type (sqlite, mysql, postgres)
 294          * @param array $p Parameter map with keys:
 295          *   - host : The hostname of the DB server
 296          *   - user : The name of the database user the client operates under
 297          *   - password : The password for the database user
 298          *   - dbname : The name of the database to use where queries do not specify one.
 299          *      The database must exist or an error might be thrown. Setting this to the empty string
 300          *      will avoid any such errors and make the handle have no implicit database scope. This is
 301          *      useful for queries like SHOW STATUS, CREATE DATABASE, or DROP DATABASE. Note that a
 302          *      "database" in Postgres is rougly equivalent to an entire MySQL server. This the domain
 303          *      in which user names and such are defined, e.g. users are database-specific in Postgres.
 304          *   - schema : The database schema to use (if supported). A "schema" in Postgres is roughly
 305          *      equivalent to a "database" in MySQL. Note that MySQL and SQLite do not use schemas.
 306          *   - tablePrefix : Optional table prefix that is implicitly added on to all table names
 307          *      recognized in queries. This can be used in place of schemas for handle site farms.
 308          *   - flags : Optional bitfield of DBO_* constants that define connection, protocol,
 309          *      buffering, and transaction behavior. It is STRONGLY adviced to leave the DBO_DEFAULT
 310          *      flag in place UNLESS this this database simply acts as a key/value store.
 311          *   - driver: Optional name of a specific DB client driver. For MySQL, there is the old
 312          *      'mysql' driver and the newer 'mysqli' driver.
 313          *   - variables: Optional map of session variables to set after connecting. This can be
 314          *      used to adjust lock timeouts or encoding modes and the like.
 315          *   - connLogger: Optional PSR-3 logger interface instance.
 316          *   - queryLogger: Optional PSR-3 logger interface instance.
 317          *   - profiler: Optional class name or object with profileIn()/profileOut() methods.
 318          *      These will be called in query(), using a simplified version of the SQL that also
 319          *      includes the agent as a SQL comment.
 320          *   - trxProfiler: Optional TransactionProfiler instance.
 321          *   - errorLogger: Optional callback that takes an Exception and logs it.
 322          *   - cliMode: Whether to consider the execution context that of a CLI script.
 323          *   - agent: Optional name used to identify the end-user in query profiling/logging.
 324          *   - srvCache: Optional BagOStuff instance to an APC-style cache.
 325          * @return Database|null If the database driver or extension cannot be found
 326          * @throws InvalidArgumentException If the database driver or extension cannot be found
 327          * @since 1.18
 328          */
 329         final public static function factory( $dbType, $p = [] ) {
 330                 static $canonicalDBTypes = [
 331                         'mysql' => [ 'mysqli', 'mysql' ],
 332                         'postgres' => [],
 333                         'sqlite' => [],
 334                         'oracle' => [],
 335                         'mssql' => [],
 336                 ];
 337
 338                 $driver = false;
 339                 $dbType = strtolower( $dbType );
 340                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 341                         $possibleDrivers = $canonicalDBTypes[$dbType];
 342                         if ( !empty( $p['driver'] ) ) {
 343                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 344                                         $driver = $p['driver'];
 345                                 } else {
 346                                         throw new InvalidArgumentException( __METHOD__ .
 347                                                 " type '$dbType' does not support driver '{$p['driver']}'" );
 348                                 }
 349                         } else {
 350                                 foreach ( $possibleDrivers as $posDriver ) {
 351                                         if ( extension_loaded( $posDriver ) ) {
 352                                                 $driver = $posDriver;
 353                                                 break;
 354                                         }
 355                                 }
 356                         }
 357                 } else {
 358                         $driver = $dbType;
 359                 }
 360                 if ( $driver === false || $driver === '' ) {
 361                         throw new InvalidArgumentException( __METHOD__ .
 362                                 " no viable database extension found for type '$dbType'" );
 363                 }
 364
 365                 $class = 'Database' . ucfirst( $driver );
 366                 if ( class_exists( $class ) && is_subclass_of( $class, 'IDatabase' ) ) {
 367                         // Resolve some defaults for b/c
 368                         $p['host'] = isset( $p['host'] ) ? $p['host'] : false;
 369                         $p['user'] = isset( $p['user'] ) ? $p['user'] : false;
 370                         $p['password'] = isset( $p['password'] ) ? $p['password'] : false;
 371                         $p['dbname'] = isset( $p['dbname'] ) ? $p['dbname'] : false;
 372                         $p['flags'] = isset( $p['flags'] ) ? $p['flags'] : 0;
 373                         $p['variables'] = isset( $p['variables'] ) ? $p['variables'] : [];
 374                         $p['tablePrefix'] = isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : '';
 375                         $p['schema'] = isset( $p['schema'] ) ? $p['schema'] : '';
 376                         $p['cliMode'] = isset( $p['cliMode'] ) ? $p['cliMode'] : ( PHP_SAPI === 'cli' );
 377                         $p['agent'] = isset( $p['agent'] ) ? $p['agent'] : '';
 378                         if ( !isset( $p['connLogger'] ) ) {
 379                                 $p['connLogger'] = new \Psr\Log\NullLogger();
 380                         }
 381                         if ( !isset( $p['queryLogger'] ) ) {
 382                                 $p['queryLogger'] = new \Psr\Log\NullLogger();
 383                         }
 384                         $p['profiler'] = isset( $p['profiler'] ) ? $p['profiler'] : null;
 385                         if ( !isset( $p['trxProfiler'] ) ) {
 386                                 $p['trxProfiler'] = new TransactionProfiler();
 387                         }
 388                         if ( !isset( $p['errorLogger'] ) ) {
 389                                 $p['errorLogger'] = function ( Exception $e ) {
 390                                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 391                                 };
 392                         }
 393
 394                         $conn = new $class( $p );
 395                 } else {
 396                         $conn = null;
 397                 }
 398
 399                 return $conn;
 400         }
 401
 402         public function setLogger( LoggerInterface $logger ) {
 403                 $this->queryLogger = $logger;
 404         }
 405
 406         public function getServerInfo() {
 407                 return $this->getServerVersion();
 408         }
 409
 410         public function bufferResults( $buffer = null ) {
 411                 $res = !$this->getFlag( self::DBO_NOBUFFER );
 412                 if ( $buffer !== null ) {
 413                         $buffer
 414                                 ? $this->clearFlag( self::DBO_NOBUFFER )
 415                                 : $this->setFlag( self::DBO_NOBUFFER );
 416                 }
 417
 418                 return $res;
 419         }
 420
 421         /**
 422          * Turns on (false) or off (true) the automatic generation and sending
 423          * of a "we're sorry, but there has been a database error" page on
 424          * database errors. Default is on (false). When turned off, the
 425          * code should use lastErrno() and lastError() to handle the
 426          * situation as appropriate.
 427          *
 428          * Do not use this function outside of the Database classes.
 429          *
 430          * @param null|bool $ignoreErrors
 431          * @return bool The previous value of the flag.
 432          */
 433         protected function ignoreErrors( $ignoreErrors = null ) {
 434                 $res = $this->getFlag( self::DBO_IGNORE );
 435                 if ( $ignoreErrors !== null ) {
 436                         $ignoreErrors
 437                                 ? $this->setFlag( self::DBO_IGNORE )
 438                                 : $this->clearFlag( self::DBO_IGNORE );
 439                 }
 440
 441                 return $res;
 442         }
 443
 444         public function trxLevel() {
 445                 return $this->mTrxLevel;
 446         }
 447
 448         public function trxTimestamp() {
 449                 return $this->mTrxLevel ? $this->mTrxTimestamp : null;
 450         }
 451
 452         public function tablePrefix( $prefix = null ) {
 453                 $old = $this->mTablePrefix;
 454                 if ( $prefix !== null ) {
 455                         $this->mTablePrefix = $prefix;
 456                         $this->currentDomain = ( $this->mDBname != '' )
 457                                 ? new DatabaseDomain( $this->mDBname, null, $this->mTablePrefix )
 458                                 : DatabaseDomain::newUnspecified();
 459                 }
 460
 461                 return $old;
 462         }
 463
 464         public function dbSchema( $schema = null ) {
 465                 $old = $this->mSchema;
 466                 if ( $schema !== null ) {
 467                         $this->mSchema = $schema;
 468                 }
 469
 470                 return $old;
 471         }
 472
 473         public function getLBInfo( $name = null ) {
 474                 if ( is_null( $name ) ) {
 475                         return $this->mLBInfo;
 476                 } else {
 477                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 478                                 return $this->mLBInfo[$name];
 479                         } else {
 480                                 return null;
 481                         }
 482                 }
 483         }
 484
 485         public function setLBInfo( $name, $value = null ) {
 486                 if ( is_null( $value ) ) {
 487                         $this->mLBInfo = $name;
 488                 } else {
 489                         $this->mLBInfo[$name] = $value;
 490                 }
 491         }
 492
 493         public function setLazyMasterHandle( IDatabase $conn ) {
 494                 $this->lazyMasterHandle = $conn;
 495         }
 496
 497         /**
 498          * @return IDatabase|null
 499          * @see setLazyMasterHandle()
 500          * @since 1.27
 501          */
 502         protected function getLazyMasterHandle() {
 503                 return $this->lazyMasterHandle;
 504         }
 505
 506         public function implicitGroupby() {
 507                 return true;
 508         }
 509
 510         public function implicitOrderby() {
 511                 return true;
 512         }
 513
 514         public function lastQuery() {
 515                 return $this->mLastQuery;
 516         }
 517
 518         public function doneWrites() {
 519                 return (bool)$this->mLastWriteTime;
 520         }
 521
 522         public function lastDoneWrites() {
 523                 return $this->mLastWriteTime ?: false;
 524         }
 525
 526         public function writesPending() {
 527                 return $this->mTrxLevel && $this->mTrxDoneWrites;
 528         }
 529
 530         public function writesOrCallbacksPending() {
 531                 return $this->mTrxLevel && (
 532                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 533                 );
 534         }
 535
 536         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 537                 if ( !$this->mTrxLevel ) {
 538                         return false;
 539                 } elseif ( !$this->mTrxDoneWrites ) {
 540                         return 0.0;
 541                 }
 542
 543                 switch ( $type ) {
 544                         case self::ESTIMATE_DB_APPLY:
 545                                 $this->ping( $rtt );
 546                                 $rttAdjTotal = $this->mTrxWriteAdjQueryCount * $rtt;
 547                                 $applyTime = max( $this->mTrxWriteAdjDuration - $rttAdjTotal, 0 );
 548                                 // For omitted queries, make them count as something at least
 549                                 $omitted = $this->mTrxWriteQueryCount - $this->mTrxWriteAdjQueryCount;
 550                                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 551
 552                                 return $applyTime;
 553                         default: // everything
 554                                 return $this->mTrxWriteDuration;
 555                 }
 556         }
 557
 558         public function pendingWriteCallers() {
 559                 return $this->mTrxLevel ? $this->mTrxWriteCallers : [];
 560         }
 561
 562         protected function pendingWriteAndCallbackCallers() {
 563                 if ( !$this->mTrxLevel ) {
 564                         return [];
 565                 }
 566
 567                 $fnames = $this->mTrxWriteCallers;
 568                 foreach ( [
 569                         $this->mTrxIdleCallbacks,
 570                         $this->mTrxPreCommitCallbacks,
 571                         $this->mTrxEndCallbacks
 572                 ] as $callbacks ) {
 573                         foreach ( $callbacks as $callback ) {
 574                                 $fnames[] = $callback[1];
 575                         }
 576                 }
 577
 578                 return $fnames;
 579         }
 580
 581         public function isOpen() {
 582                 return $this->mOpened;
 583         }
 584
 585         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 586                 if ( $remember === self::REMEMBER_PRIOR ) {
 587                         array_push( $this->priorFlags, $this->mFlags );
 588                 }
 589                 $this->mFlags |= $flag;
 590         }
 591
 592         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 593                 if ( $remember === self::REMEMBER_PRIOR ) {
 594                         array_push( $this->priorFlags, $this->mFlags );
 595                 }
 596                 $this->mFlags &= ~$flag;
 597         }
 598
 599         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 600                 if ( !$this->priorFlags ) {
 601                         return;
 602                 }
 603
 604                 if ( $state === self::RESTORE_INITIAL ) {
 605                         $this->mFlags = reset( $this->priorFlags );
 606                         $this->priorFlags = [];
 607                 } else {
 608                         $this->mFlags = array_pop( $this->priorFlags );
 609                 }
 610         }
 611
 612         public function getFlag( $flag ) {
 613                 return !!( $this->mFlags & $flag );
 614         }
 615
 616         /**
 617          * @param string $name Class field name
 618          * @return mixed
 619          * @deprecated Since 1.28
 620          */
 621         public function getProperty( $name ) {
 622                 return $this->$name;
 623         }
 624
 625         public function getDomainID() {
 626                 return $this->currentDomain->getId();
 627         }
 628
 629         final public function getWikiID() {
 630                 return $this->getDomainID();
 631         }
 632
 633         /**
 634          * Get information about an index into an object
 635          * @param string $table Table name
 636          * @param string $index Index name
 637          * @param string $fname Calling function name
 638          * @return mixed Database-specific index description class or false if the index does not exist
 639          */
 640         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 641
 642         /**
 643          * Wrapper for addslashes()
 644          *
 645          * @param string $s String to be slashed.
 646          * @return string Slashed string.
 647          */
 648         abstract function strencode( $s );
 649
 650         protected function installErrorHandler() {
 651                 $this->mPHPError = false;
 652                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 653                 set_error_handler( [ $this, 'connectionErrorLogger' ] );
 654         }
 655
 656         /**
 657          * @return bool|string
 658          */
 659         protected function restoreErrorHandler() {
 660                 restore_error_handler();
 661                 if ( $this->htmlErrors !== false ) {
 662                         ini_set( 'html_errors', $this->htmlErrors );
 663                 }
 664
 665                 return $this->getLastPHPError();
 666         }
 667
 668         /**
 669          * @return string|bool Last PHP error for this DB (typically connection errors)
 670          */
 671         protected function getLastPHPError() {
 672                 if ( $this->mPHPError ) {
 673                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 674                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 675
 676                         return $error;
 677                 }
 678
 679                 return false;
 680         }
 681
 682         /**
 683          * This method should not be used outside of Database classes
 684          *
 685          * @param int $errno
 686          * @param string $errstr
 687          */
 688         public function connectionErrorLogger( $errno, $errstr ) {
 689                 $this->mPHPError = $errstr;
 690         }
 691
 692         /**
 693          * Create a log context to pass to PSR-3 logger functions.
 694          *
 695          * @param array $extras Additional data to add to context
 696          * @return array
 697          */
 698         protected function getLogContext( array $extras = [] ) {
 699                 return array_merge(
 700                         [
 701                                 'db_server' => $this->mServer,
 702                                 'db_name' => $this->mDBname,
 703                                 'db_user' => $this->mUser,
 704                         ],
 705                         $extras
 706                 );
 707         }
 708
 709         public function close() {
 710                 if ( $this->mConn ) {
 711                         if ( $this->trxLevel() ) {
 712                                 $this->commit( __METHOD__, self::FLUSHING_INTERNAL );
 713                         }
 714
 715                         $closed = $this->closeConnection();
 716                         $this->mConn = false;
 717                 } elseif ( $this->mTrxIdleCallbacks || $this->mTrxEndCallbacks ) { // sanity
 718                         throw new RuntimeException( "Transaction callbacks still pending." );
 719                 } else {
 720                         $closed = true;
 721                 }
 722                 $this->mOpened = false;
 723
 724                 return $closed;
 725         }
 726
 727         /**
 728          * Make sure isOpen() returns true as a sanity check
 729          *
 730          * @throws DBUnexpectedError
 731          */
 732         protected function assertOpen() {
 733                 if ( !$this->isOpen() ) {
 734                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
 735                 }
 736         }
 737
 738         /**
 739          * Closes underlying database connection
 740          * @since 1.20
 741          * @return bool Whether connection was closed successfully
 742          */
 743         abstract protected function closeConnection();
 744
 745         public function reportConnectionError( $error = 'Unknown error' ) {
 746                 $myError = $this->lastError();
 747                 if ( $myError ) {
 748                         $error = $myError;
 749                 }
 750
 751                 # New method
 752                 throw new DBConnectionError( $this, $error );
 753         }
 754
 755         /**
 756          * The DBMS-dependent part of query()
 757          *
 758          * @param string $sql SQL query.
 759          * @return ResultWrapper|bool Result object to feed to fetchObject,
 760          *   fetchRow, ...; or false on failure
 761          */
 762         abstract protected function doQuery( $sql );
 763
 764         /**
 765          * Determine whether a query writes to the DB.
 766          * Should return true if unsure.
 767          *
 768          * @param string $sql
 769          * @return bool
 770          */
 771         protected function isWriteQuery( $sql ) {
 772                 return !preg_match(
 773                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 774         }
 775
 776         /**
 777          * @param $sql
 778          * @return string|null
 779          */
 780         protected function getQueryVerb( $sql ) {
 781                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
 782         }
 783
 784         /**
 785          * Determine whether a SQL statement is sensitive to isolation level.
 786          * A SQL statement is considered transactable if its result could vary
 787          * depending on the transaction isolation level. Operational commands
 788          * such as 'SET' and 'SHOW' are not considered to be transactable.
 789          *
 790          * @param string $sql
 791          * @return bool
 792          */
 793         protected function isTransactableQuery( $sql ) {
 794                 return !in_array(
 795                         $this->getQueryVerb( $sql ),
 796                         [ 'BEGIN', 'COMMIT', 'ROLLBACK', 'SHOW', 'SET', 'CREATE', 'ALTER' ],
 797                         true
 798                 );
 799         }
 800
 801         /**
 802          * @param string $sql A SQL query
 803          * @return bool Whether $sql is SQL for creating/dropping a new TEMPORARY table
 804          */
 805         protected function registerTempTableOperation( $sql ) {
 806                 if ( preg_match(
 807                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 808                         $sql,
 809                         $matches
 810                 ) ) {
 811                         $this->mSessionTempTables[$matches[1]] = 1;
 812
 813                         return true;
 814                 } elseif ( preg_match(
 815                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
 816                         $sql,
 817                         $matches
 818                 ) ) {
 819                         unset( $this->mSessionTempTables[$matches[1]] );
 820
 821                         return true;
 822                 } elseif ( preg_match(
 823                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
 824                         $sql,
 825                         $matches
 826                 ) ) {
 827                         return isset( $this->mSessionTempTables[$matches[1]] );
 828                 }
 829
 830                 return false;
 831         }
 832
 833         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 834                 $priorWritesPending = $this->writesOrCallbacksPending();
 835                 $this->mLastQuery = $sql;
 836
 837                 $isWrite = $this->isWriteQuery( $sql ) && !$this->registerTempTableOperation( $sql );
 838                 if ( $isWrite ) {
 839                         $reason = $this->getReadOnlyReason();
 840                         if ( $reason !== false ) {
 841                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
 842                         }
 843                         # Set a flag indicating that writes have been done
 844                         $this->mLastWriteTime = microtime( true );
 845                 }
 846
 847                 // Add trace comment to the begin of the sql string, right after the operator.
 848                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 849                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
 850
 851                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
 852                 if ( !$this->mTrxLevel && $this->getFlag( self::DBO_TRX )
 853                         && $this->isTransactableQuery( $sql )
 854                 ) {
 855                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
 856                         $this->mTrxAutomatic = true;
 857                 }
 858
 859                 # Keep track of whether the transaction has write queries pending
 860                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $isWrite ) {
 861                         $this->mTrxDoneWrites = true;
 862                         $this->trxProfiler->transactionWritingIn(
 863                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
 864                 }
 865
 866                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
 867                         $this->queryLogger->debug( "{$this->mDBname} {$commentedSql}" );
 868                 }
 869
 870                 # Avoid fatals if close() was called
 871                 $this->assertOpen();
 872
 873                 # Send the query to the server
 874                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isWrite, $fname );
 875
 876                 # Try reconnecting if the connection was lost
 877                 if ( false === $ret && $this->wasErrorReissuable() ) {
 878                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
 879                         # Stash the last error values before anything might clear them
 880                         $lastError = $this->lastError();
 881                         $lastErrno = $this->lastErrno();
 882                         # Update state tracking to reflect transaction loss due to disconnection
 883                         $this->handleSessionLoss();
 884                         if ( $this->reconnect() ) {
 885                                 $msg = __METHOD__ . ": lost connection to {$this->getServer()}; reconnected";
 886                                 $this->connLogger->warning( $msg );
 887                                 $this->queryLogger->warning(
 888                                         "$msg:\n" . ( new RuntimeException() )->getTraceAsString() );
 889
 890                                 if ( !$recoverable ) {
 891                                         # Callers may catch the exception and continue to use the DB
 892                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname );
 893                                 } else {
 894                                         # Should be safe to silently retry the query
 895                                         $ret = $this->doProfiledQuery( $sql, $commentedSql, $isWrite, $fname );
 896                                 }
 897                         } else {
 898                                 $msg = __METHOD__ . ": lost connection to {$this->getServer()} permanently";
 899                                 $this->connLogger->error( $msg );
 900                         }
 901                 }
 902
 903                 if ( false === $ret ) {
 904                         # Deadlocks cause the entire transaction to abort, not just the statement.
 905                         # https://dev.mysql.com/doc/refman/5.7/en/innodb-error-handling.html
 906                         # https://www.postgresql.org/docs/9.1/static/explicit-locking.html
 907                         if ( $this->wasDeadlock() ) {
 908                                 if ( $this->explicitTrxActive() || $priorWritesPending ) {
 909                                         $tempIgnore = false; // not recoverable
 910                                 }
 911                                 # Update state tracking to reflect transaction loss
 912                                 $this->handleSessionLoss();
 913                         }
 914
 915                         $this->reportQueryError(
 916                                 $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 917                 }
 918
 919                 $res = $this->resultObject( $ret );
 920
 921                 return $res;
 922         }
 923
 924         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
 925                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 926                 # generalizeSQL() will probably cut down the query to reasonable
 927                 # logging size most of the time. The substr is really just a sanity check.
 928                 if ( $isMaster ) {
 929                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
 930                 } else {
 931                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
 932                 }
 933
 934                 # Include query transaction state
 935                 $queryProf .= $this->mTrxShortId ? " [TRX#{$this->mTrxShortId}]" : "";
 936
 937                 $startTime = microtime( true );
 938                 if ( $this->profiler ) {
 939                         call_user_func( [ $this->profiler, 'profileIn' ], $queryProf );
 940                 }
 941                 $ret = $this->doQuery( $commentedSql );
 942                 if ( $this->profiler ) {
 943                         call_user_func( [ $this->profiler, 'profileOut' ], $queryProf );
 944                 }
 945                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
 946
 947                 unset( $queryProfSection ); // profile out (if set)
 948
 949                 if ( $ret !== false ) {
 950                         $this->lastPing = $startTime;
 951                         if ( $isWrite && $this->mTrxLevel ) {
 952                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime );
 953                                 $this->mTrxWriteCallers[] = $fname;
 954                         }
 955                 }
 956
 957                 if ( $sql === self::PING_QUERY ) {
 958                         $this->mRTTEstimate = $queryRuntime;
 959                 }
 960
 961                 $this->trxProfiler->recordQueryCompletion(
 962                         $queryProf, $startTime, $isWrite, $this->affectedRows()
 963                 );
 964                 $this->queryLogger->debug( $sql, [
 965                         'method' => $fname,
 966                         'master' => $isMaster,
 967                         'runtime' => $queryRuntime,
 968                 ] );
 969
 970                 return $ret;
 971         }
 972
 973         /**
 974          * Update the estimated run-time of a query, not counting large row lock times
 975          *
 976          * LoadBalancer can be set to rollback transactions that will create huge replication
 977          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
 978          * queries, like inserting a row can take a long time due to row locking. This method
 979          * uses some simple heuristics to discount those cases.
 980          *
 981          * @param string $sql A SQL write query
 982          * @param float $runtime Total runtime, including RTT
 983          */
 984         private function updateTrxWriteQueryTime( $sql, $runtime ) {
 985                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
 986                 $indicativeOfReplicaRuntime = true;
 987                 if ( $runtime > self::SLOW_WRITE_SEC ) {
 988                         $verb = $this->getQueryVerb( $sql );
 989                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
 990                         if ( $verb === 'INSERT' ) {
 991                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
 992                         } elseif ( $verb === 'REPLACE' ) {
 993                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
 994                         }
 995                 }
 996
 997                 $this->mTrxWriteDuration += $runtime;
 998                 $this->mTrxWriteQueryCount += 1;
 999                 if ( $indicativeOfReplicaRuntime ) {
1000                         $this->mTrxWriteAdjDuration += $runtime;
1001                         $this->mTrxWriteAdjQueryCount += 1;
1002                 }
1003         }
1004
1005         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1006                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1007                 # Dropped connections also mean that named locks are automatically released.
1008                 # Only allow error suppression in autocommit mode or when the lost transaction
1009                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1010                 if ( $this->mNamedLocksHeld ) {
1011                         return false; // possible critical section violation
1012                 } elseif ( $sql === 'COMMIT' ) {
1013                         return !$priorWritesPending; // nothing written anyway? (T127428)
1014                 } elseif ( $sql === 'ROLLBACK' ) {
1015                         return true; // transaction lost...which is also what was requested :)
1016                 } elseif ( $this->explicitTrxActive() ) {
1017                         return false; // don't drop atomocity
1018                 } elseif ( $priorWritesPending ) {
1019                         return false; // prior writes lost from implicit transaction
1020                 }
1021
1022                 return true;
1023         }
1024
1025         private function handleSessionLoss() {
1026                 $this->mTrxLevel = 0;
1027                 $this->mTrxIdleCallbacks = []; // bug 65263
1028                 $this->mTrxPreCommitCallbacks = []; // bug 65263
1029                 $this->mSessionTempTables = [];
1030                 $this->mNamedLocksHeld = [];
1031                 try {
1032                         // Handle callbacks in mTrxEndCallbacks
1033                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1034                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1035                         return null;
1036                 } catch ( Exception $e ) {
1037                         // Already logged; move on...
1038                         return $e;
1039                 }
1040         }
1041
1042         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1043                 if ( $this->ignoreErrors() || $tempIgnore ) {
1044                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1045                 } else {
1046                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1047                         $this->queryLogger->error(
1048                                 "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1049                                 $this->getLogContext( [
1050                                         'method' => __METHOD__,
1051                                         'errno' => $errno,
1052                                         'error' => $error,
1053                                         'sql1line' => $sql1line,
1054                                         'fname' => $fname,
1055                                 ] )
1056                         );
1057                         $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1058                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1059                 }
1060         }
1061
1062         public function freeResult( $res ) {
1063         }
1064
1065         public function selectField(
1066                 $table, $var, $cond = '', $fname = __METHOD__, $options = []
1067         ) {
1068                 if ( $var === '*' ) { // sanity
1069                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1070                 }
1071
1072                 if ( !is_array( $options ) ) {
1073                         $options = [ $options ];
1074                 }
1075
1076                 $options['LIMIT'] = 1;
1077
1078                 $res = $this->select( $table, $var, $cond, $fname, $options );
1079                 if ( $res === false || !$this->numRows( $res ) ) {
1080                         return false;
1081                 }
1082
1083                 $row = $this->fetchRow( $res );
1084
1085                 if ( $row !== false ) {
1086                         return reset( $row );
1087                 } else {
1088                         return false;
1089                 }
1090         }
1091
1092         public function selectFieldValues(
1093                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1094         ) {
1095                 if ( $var === '*' ) { // sanity
1096                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1097                 } elseif ( !is_string( $var ) ) { // sanity
1098                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1099                 }
1100
1101                 if ( !is_array( $options ) ) {
1102                         $options = [ $options ];
1103                 }
1104
1105                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1106                 if ( $res === false ) {
1107                         return false;
1108                 }
1109
1110                 $values = [];
1111                 foreach ( $res as $row ) {
1112                         $values[] = $row->$var;
1113                 }
1114
1115                 return $values;
1116         }
1117
1118         /**
1119          * Returns an optional USE INDEX clause to go after the table, and a
1120          * string to go at the end of the query.
1121          *
1122          * @param array $options Associative array of options to be turned into
1123          *   an SQL query, valid keys are listed in the function.
1124          * @return array
1125          * @see Database::select()
1126          */
1127         protected function makeSelectOptions( $options ) {
1128                 $preLimitTail = $postLimitTail = '';
1129                 $startOpts = '';
1130
1131                 $noKeyOptions = [];
1132
1133                 foreach ( $options as $key => $option ) {
1134                         if ( is_numeric( $key ) ) {
1135                                 $noKeyOptions[$option] = true;
1136                         }
1137                 }
1138
1139                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1140
1141                 $preLimitTail .= $this->makeOrderBy( $options );
1142
1143                 // if (isset($options['LIMIT'])) {
1144                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1145                 //              isset($options['OFFSET']) ? $options['OFFSET']
1146                 //              : false);
1147                 // }
1148
1149                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1150                         $postLimitTail .= ' FOR UPDATE';
1151                 }
1152
1153                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1154                         $postLimitTail .= ' LOCK IN SHARE MODE';
1155                 }
1156
1157                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1158                         $startOpts .= 'DISTINCT';
1159                 }
1160
1161                 # Various MySQL extensions
1162                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1163                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1164                 }
1165
1166                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1167                         $startOpts .= ' HIGH_PRIORITY';
1168                 }
1169
1170                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1171                         $startOpts .= ' SQL_BIG_RESULT';
1172                 }
1173
1174                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1175                         $startOpts .= ' SQL_BUFFER_RESULT';
1176                 }
1177
1178                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1179                         $startOpts .= ' SQL_SMALL_RESULT';
1180                 }
1181
1182                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1183                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1184                 }
1185
1186                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1187                         $startOpts .= ' SQL_CACHE';
1188                 }
1189
1190                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1191                         $startOpts .= ' SQL_NO_CACHE';
1192                 }
1193
1194                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1195                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1196                 } else {
1197                         $useIndex = '';
1198                 }
1199                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1200                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1201                 } else {
1202                         $ignoreIndex = '';
1203                 }
1204
1205                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1206         }
1207
1208         /**
1209          * Returns an optional GROUP BY with an optional HAVING
1210          *
1211          * @param array $options Associative array of options
1212          * @return string
1213          * @see Database::select()
1214          * @since 1.21
1215          */
1216         protected function makeGroupByWithHaving( $options ) {
1217                 $sql = '';
1218                 if ( isset( $options['GROUP BY'] ) ) {
1219                         $gb = is_array( $options['GROUP BY'] )
1220                                 ? implode( ',', $options['GROUP BY'] )
1221                                 : $options['GROUP BY'];
1222                         $sql .= ' GROUP BY ' . $gb;
1223                 }
1224                 if ( isset( $options['HAVING'] ) ) {
1225                         $having = is_array( $options['HAVING'] )
1226                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1227                                 : $options['HAVING'];
1228                         $sql .= ' HAVING ' . $having;
1229                 }
1230
1231                 return $sql;
1232         }
1233
1234         /**
1235          * Returns an optional ORDER BY
1236          *
1237          * @param array $options Associative array of options
1238          * @return string
1239          * @see Database::select()
1240          * @since 1.21
1241          */
1242         protected function makeOrderBy( $options ) {
1243                 if ( isset( $options['ORDER BY'] ) ) {
1244                         $ob = is_array( $options['ORDER BY'] )
1245                                 ? implode( ',', $options['ORDER BY'] )
1246                                 : $options['ORDER BY'];
1247
1248                         return ' ORDER BY ' . $ob;
1249                 }
1250
1251                 return '';
1252         }
1253
1254         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1255                 $options = [], $join_conds = [] ) {
1256                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1257
1258                 return $this->query( $sql, $fname );
1259         }
1260
1261         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1262                 $options = [], $join_conds = []
1263         ) {
1264                 if ( is_array( $vars ) ) {
1265                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1266                 }
1267
1268                 $options = (array)$options;
1269                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1270                         ? $options['USE INDEX']
1271                         : [];
1272                 $ignoreIndexes = (
1273                         isset( $options['IGNORE INDEX'] ) &&
1274                         is_array( $options['IGNORE INDEX'] )
1275                 )
1276                         ? $options['IGNORE INDEX']
1277                         : [];
1278
1279                 if ( is_array( $table ) ) {
1280                         $from = ' FROM ' .
1281                                 $this->tableNamesWithIndexClauseOrJOIN(
1282                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1283                 } elseif ( $table != '' ) {
1284                         if ( $table[0] == ' ' ) {
1285                                 $from = ' FROM ' . $table;
1286                         } else {
1287                                 $from = ' FROM ' .
1288                                         $this->tableNamesWithIndexClauseOrJOIN(
1289                                                 [ $table ], $useIndexes, $ignoreIndexes, [] );
1290                         }
1291                 } else {
1292                         $from = '';
1293                 }
1294
1295                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1296                         $this->makeSelectOptions( $options );
1297
1298                 if ( !empty( $conds ) ) {
1299                         if ( is_array( $conds ) ) {
1300                                 $conds = $this->makeList( $conds, self::LIST_AND );
1301                         }
1302                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex " .
1303                                 "WHERE $conds $preLimitTail";
1304                 } else {
1305                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex $preLimitTail";
1306                 }
1307
1308                 if ( isset( $options['LIMIT'] ) ) {
1309                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1310                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1311                 }
1312                 $sql = "$sql $postLimitTail";
1313
1314                 if ( isset( $options['EXPLAIN'] ) ) {
1315                         $sql = 'EXPLAIN ' . $sql;
1316                 }
1317
1318                 return $sql;
1319         }
1320
1321         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1322                 $options = [], $join_conds = []
1323         ) {
1324                 $options = (array)$options;
1325                 $options['LIMIT'] = 1;
1326                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1327
1328                 if ( $res === false ) {
1329                         return false;
1330                 }
1331
1332                 if ( !$this->numRows( $res ) ) {
1333                         return false;
1334                 }
1335
1336                 $obj = $this->fetchObject( $res );
1337
1338                 return $obj;
1339         }
1340
1341         public function estimateRowCount(
1342                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
1343         ) {
1344                 $rows = 0;
1345                 $res = $this->select( $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options );
1346
1347                 if ( $res ) {
1348                         $row = $this->fetchRow( $res );
1349                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1350                 }
1351
1352                 return $rows;
1353         }
1354
1355         public function selectRowCount(
1356                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1357         ) {
1358                 $rows = 0;
1359                 $sql = $this->selectSQLText( $tables, '1', $conds, $fname, $options, $join_conds );
1360                 $res = $this->query( "SELECT COUNT(*) AS rowcount FROM ($sql) tmp_count", $fname );
1361
1362                 if ( $res ) {
1363                         $row = $this->fetchRow( $res );
1364                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1365                 }
1366
1367                 return $rows;
1368         }
1369
1370         /**
1371          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1372          * It's only slightly flawed. Don't use for anything important.
1373          *
1374          * @param string $sql A SQL Query
1375          *
1376          * @return string
1377          */
1378         protected static function generalizeSQL( $sql ) {
1379                 # This does the same as the regexp below would do, but in such a way
1380                 # as to avoid crashing php on some large strings.
1381                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1382
1383                 $sql = str_replace( "\\\\", '', $sql );
1384                 $sql = str_replace( "\\'", '', $sql );
1385                 $sql = str_replace( "\\\"", '', $sql );
1386                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1387                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1388
1389                 # All newlines, tabs, etc replaced by single space
1390                 $sql = preg_replace( '/\s+/', ' ', $sql );
1391
1392                 # All numbers => N,
1393                 # except the ones surrounded by characters, e.g. l10n
1394                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1395                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1396
1397                 return $sql;
1398         }
1399
1400         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1401                 $info = $this->fieldInfo( $table, $field );
1402
1403                 return (bool)$info;
1404         }
1405
1406         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1407                 if ( !$this->tableExists( $table ) ) {
1408                         return null;
1409                 }
1410
1411                 $info = $this->indexInfo( $table, $index, $fname );
1412                 if ( is_null( $info ) ) {
1413                         return null;
1414                 } else {
1415                         return $info !== false;
1416                 }
1417         }
1418
1419         public function tableExists( $table, $fname = __METHOD__ ) {
1420                 $tableRaw = $this->tableName( $table, 'raw' );
1421                 if ( isset( $this->mSessionTempTables[$tableRaw] ) ) {
1422                         return true; // already known to exist
1423                 }
1424
1425                 $table = $this->tableName( $table );
1426                 $ignoreErrors = true;
1427                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname, $ignoreErrors );
1428
1429                 return (bool)$res;
1430         }
1431
1432         public function indexUnique( $table, $index ) {
1433                 $indexInfo = $this->indexInfo( $table, $index );
1434
1435                 if ( !$indexInfo ) {
1436                         return null;
1437                 }
1438
1439                 return !$indexInfo[0]->Non_unique;
1440         }
1441
1442         /**
1443          * Helper for Database::insert().
1444          *
1445          * @param array $options
1446          * @return string
1447          */
1448         protected function makeInsertOptions( $options ) {
1449                 return implode( ' ', $options );
1450         }
1451
1452         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1453                 # No rows to insert, easy just return now
1454                 if ( !count( $a ) ) {
1455                         return true;
1456                 }
1457
1458                 $table = $this->tableName( $table );
1459
1460                 if ( !is_array( $options ) ) {
1461                         $options = [ $options ];
1462                 }
1463
1464                 $fh = null;
1465                 if ( isset( $options['fileHandle'] ) ) {
1466                         $fh = $options['fileHandle'];
1467                 }
1468                 $options = $this->makeInsertOptions( $options );
1469
1470                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1471                         $multi = true;
1472                         $keys = array_keys( $a[0] );
1473                 } else {
1474                         $multi = false;
1475                         $keys = array_keys( $a );
1476                 }
1477
1478                 $sql = 'INSERT ' . $options .
1479                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1480
1481                 if ( $multi ) {
1482                         $first = true;
1483                         foreach ( $a as $row ) {
1484                                 if ( $first ) {
1485                                         $first = false;
1486                                 } else {
1487                                         $sql .= ',';
1488                                 }
1489                                 $sql .= '(' . $this->makeList( $row ) . ')';
1490                         }
1491                 } else {
1492                         $sql .= '(' . $this->makeList( $a ) . ')';
1493                 }
1494
1495                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1496                         return false;
1497                 } elseif ( $fh !== null ) {
1498                         return true;
1499                 }
1500
1501                 return (bool)$this->query( $sql, $fname );
1502         }
1503
1504         /**
1505          * Make UPDATE options array for Database::makeUpdateOptions
1506          *
1507          * @param array $options
1508          * @return array
1509          */
1510         protected function makeUpdateOptionsArray( $options ) {
1511                 if ( !is_array( $options ) ) {
1512                         $options = [ $options ];
1513                 }
1514
1515                 $opts = [];
1516
1517                 if ( in_array( 'IGNORE', $options ) ) {
1518                         $opts[] = 'IGNORE';
1519                 }
1520
1521                 return $opts;
1522         }
1523
1524         /**
1525          * Make UPDATE options for the Database::update function
1526          *
1527          * @param array $options The options passed to Database::update
1528          * @return string
1529          */
1530         protected function makeUpdateOptions( $options ) {
1531                 $opts = $this->makeUpdateOptionsArray( $options );
1532
1533                 return implode( ' ', $opts );
1534         }
1535
1536         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1537                 $table = $this->tableName( $table );
1538                 $opts = $this->makeUpdateOptions( $options );
1539                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
1540
1541                 if ( $conds !== [] && $conds !== '*' ) {
1542                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
1543                 }
1544
1545                 return $this->query( $sql, $fname );
1546         }
1547
1548         public function makeList( $a, $mode = self::LIST_COMMA ) {
1549                 if ( !is_array( $a ) ) {
1550                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1551                 }
1552
1553                 $first = true;
1554                 $list = '';
1555
1556                 foreach ( $a as $field => $value ) {
1557                         if ( !$first ) {
1558                                 if ( $mode == self::LIST_AND ) {
1559                                         $list .= ' AND ';
1560                                 } elseif ( $mode == self::LIST_OR ) {
1561                                         $list .= ' OR ';
1562                                 } else {
1563                                         $list .= ',';
1564                                 }
1565                         } else {
1566                                 $first = false;
1567                         }
1568
1569                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
1570                                 $list .= "($value)";
1571                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
1572                                 $list .= "$value";
1573                         } elseif (
1574                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
1575                         ) {
1576                                 // Remove null from array to be handled separately if found
1577                                 $includeNull = false;
1578                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
1579                                         $includeNull = true;
1580                                         unset( $value[$nullKey] );
1581                                 }
1582                                 if ( count( $value ) == 0 && !$includeNull ) {
1583                                         throw new InvalidArgumentException(
1584                                                 __METHOD__ . ": empty input for field $field" );
1585                                 } elseif ( count( $value ) == 0 ) {
1586                                         // only check if $field is null
1587                                         $list .= "$field IS NULL";
1588                                 } else {
1589                                         // IN clause contains at least one valid element
1590                                         if ( $includeNull ) {
1591                                                 // Group subconditions to ensure correct precedence
1592                                                 $list .= '(';
1593                                         }
1594                                         if ( count( $value ) == 1 ) {
1595                                                 // Special-case single values, as IN isn't terribly efficient
1596                                                 // Don't necessarily assume the single key is 0; we don't
1597                                                 // enforce linear numeric ordering on other arrays here.
1598                                                 $value = array_values( $value )[0];
1599                                                 $list .= $field . " = " . $this->addQuotes( $value );
1600                                         } else {
1601                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1602                                         }
1603                                         // if null present in array, append IS NULL
1604                                         if ( $includeNull ) {
1605                                                 $list .= " OR $field IS NULL)";
1606                                         }
1607                                 }
1608                         } elseif ( $value === null ) {
1609                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
1610                                         $list .= "$field IS ";
1611                                 } elseif ( $mode == self::LIST_SET ) {
1612                                         $list .= "$field = ";
1613                                 }
1614                                 $list .= 'NULL';
1615                         } else {
1616                                 if (
1617                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
1618                                 ) {
1619                                         $list .= "$field = ";
1620                                 }
1621                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
1622                         }
1623                 }
1624
1625                 return $list;
1626         }
1627
1628         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1629                 $conds = [];
1630
1631                 foreach ( $data as $base => $sub ) {
1632                         if ( count( $sub ) ) {
1633                                 $conds[] = $this->makeList(
1634                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
1635                                         self::LIST_AND );
1636                         }
1637                 }
1638
1639                 if ( $conds ) {
1640                         return $this->makeList( $conds, self::LIST_OR );
1641                 } else {
1642                         // Nothing to search for...
1643                         return false;
1644                 }
1645         }
1646
1647         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1648                 return $valuename;
1649         }
1650
1651         public function bitNot( $field ) {
1652                 return "(~$field)";
1653         }
1654
1655         public function bitAnd( $fieldLeft, $fieldRight ) {
1656                 return "($fieldLeft & $fieldRight)";
1657         }
1658
1659         public function bitOr( $fieldLeft, $fieldRight ) {
1660                 return "($fieldLeft | $fieldRight)";
1661         }
1662
1663         public function buildConcat( $stringList ) {
1664                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1665         }
1666
1667         public function buildGroupConcatField(
1668                 $delim, $table, $field, $conds = '', $join_conds = []
1669         ) {
1670                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
1671
1672                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
1673         }
1674
1675         public function buildStringCast( $field ) {
1676                 return $field;
1677         }
1678
1679         public function selectDB( $db ) {
1680                 # Stub. Shouldn't cause serious problems if it's not overridden, but
1681                 # if your database engine supports a concept similar to MySQL's
1682                 # databases you may as well.
1683                 $this->mDBname = $db;
1684
1685                 return true;
1686         }
1687
1688         public function getDBname() {
1689                 return $this->mDBname;
1690         }
1691
1692         public function getServer() {
1693                 return $this->mServer;
1694         }
1695
1696         public function tableName( $name, $format = 'quoted' ) {
1697                 # Skip the entire process when we have a string quoted on both ends.
1698                 # Note that we check the end so that we will still quote any use of
1699                 # use of `database`.table. But won't break things if someone wants
1700                 # to query a database table with a dot in the name.
1701                 if ( $this->isQuotedIdentifier( $name ) ) {
1702                         return $name;
1703                 }
1704
1705                 # Lets test for any bits of text that should never show up in a table
1706                 # name. Basically anything like JOIN or ON which are actually part of
1707                 # SQL queries, but may end up inside of the table value to combine
1708                 # sql. Such as how the API is doing.
1709                 # Note that we use a whitespace test rather than a \b test to avoid
1710                 # any remote case where a word like on may be inside of a table name
1711                 # surrounded by symbols which may be considered word breaks.
1712                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1713                         return $name;
1714                 }
1715
1716                 # Split database and table into proper variables.
1717                 # We reverse the explode so that database.table and table both output
1718                 # the correct table.
1719                 $dbDetails = explode( '.', $name, 3 );
1720                 if ( count( $dbDetails ) == 3 ) {
1721                         list( $database, $schema, $table ) = $dbDetails;
1722                         # We don't want any prefix added in this case
1723                         $prefix = '';
1724                 } elseif ( count( $dbDetails ) == 2 ) {
1725                         list( $database, $table ) = $dbDetails;
1726                         # We don't want any prefix added in this case
1727                         $prefix = '';
1728                         # In dbs that support it, $database may actually be the schema
1729                         # but that doesn't affect any of the functionality here
1730                         $schema = '';
1731                 } else {
1732                         list( $table ) = $dbDetails;
1733                         if ( isset( $this->tableAliases[$table] ) ) {
1734                                 $database = $this->tableAliases[$table]['dbname'];
1735                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
1736                                         ? $this->tableAliases[$table]['schema']
1737                                         : $this->mSchema;
1738                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
1739                                         ? $this->tableAliases[$table]['prefix']
1740                                         : $this->mTablePrefix;
1741                         } else {
1742                                 $database = '';
1743                                 $schema = $this->mSchema; # Default schema
1744                                 $prefix = $this->mTablePrefix; # Default prefix
1745                         }
1746                 }
1747
1748                 # Quote $table and apply the prefix if not quoted.
1749                 # $tableName might be empty if this is called from Database::replaceVars()
1750                 $tableName = "{$prefix}{$table}";
1751                 if ( $format === 'quoted'
1752                         && !$this->isQuotedIdentifier( $tableName )
1753                         && $tableName !== ''
1754                 ) {
1755                         $tableName = $this->addIdentifierQuotes( $tableName );
1756                 }
1757
1758                 # Quote $schema and $database and merge them with the table name if needed
1759                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
1760                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
1761
1762                 return $tableName;
1763         }
1764
1765         /**
1766          * @param string|null $namespace Database or schema
1767          * @param string $relation Name of table, view, sequence, etc...
1768          * @param string $format One of (raw, quoted)
1769          * @return string Relation name with quoted and merged $namespace as needed
1770          */
1771         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
1772                 if ( strlen( $namespace ) ) {
1773                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
1774                                 $namespace = $this->addIdentifierQuotes( $namespace );
1775                         }
1776                         $relation = $namespace . '.' . $relation;
1777                 }
1778
1779                 return $relation;
1780         }
1781
1782         public function tableNames() {
1783                 $inArray = func_get_args();
1784                 $retVal = [];
1785
1786                 foreach ( $inArray as $name ) {
1787                         $retVal[$name] = $this->tableName( $name );
1788                 }
1789
1790                 return $retVal;
1791         }
1792
1793         public function tableNamesN() {
1794                 $inArray = func_get_args();
1795                 $retVal = [];
1796
1797                 foreach ( $inArray as $name ) {
1798                         $retVal[] = $this->tableName( $name );
1799                 }
1800
1801                 return $retVal;
1802         }
1803
1804         /**
1805          * Get an aliased table name
1806          * e.g. tableName AS newTableName
1807          *
1808          * @param string $name Table name, see tableName()
1809          * @param string|bool $alias Alias (optional)
1810          * @return string SQL name for aliased table. Will not alias a table to its own name
1811          */
1812         protected function tableNameWithAlias( $name, $alias = false ) {
1813                 if ( !$alias || $alias == $name ) {
1814                         return $this->tableName( $name );
1815                 } else {
1816                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
1817                 }
1818         }
1819
1820         /**
1821          * Gets an array of aliased table names
1822          *
1823          * @param array $tables [ [alias] => table ]
1824          * @return string[] See tableNameWithAlias()
1825          */
1826         protected function tableNamesWithAlias( $tables ) {
1827                 $retval = [];
1828                 foreach ( $tables as $alias => $table ) {
1829                         if ( is_numeric( $alias ) ) {
1830                                 $alias = $table;
1831                         }
1832                         $retval[] = $this->tableNameWithAlias( $table, $alias );
1833                 }
1834
1835                 return $retval;
1836         }
1837
1838         /**
1839          * Get an aliased field name
1840          * e.g. fieldName AS newFieldName
1841          *
1842          * @param string $name Field name
1843          * @param string|bool $alias Alias (optional)
1844          * @return string SQL name for aliased field. Will not alias a field to its own name
1845          */
1846         protected function fieldNameWithAlias( $name, $alias = false ) {
1847                 if ( !$alias || (string)$alias === (string)$name ) {
1848                         return $name;
1849                 } else {
1850                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
1851                 }
1852         }
1853
1854         /**
1855          * Gets an array of aliased field names
1856          *
1857          * @param array $fields [ [alias] => field ]
1858          * @return string[] See fieldNameWithAlias()
1859          */
1860         protected function fieldNamesWithAlias( $fields ) {
1861                 $retval = [];
1862                 foreach ( $fields as $alias => $field ) {
1863                         if ( is_numeric( $alias ) ) {
1864                                 $alias = $field;
1865                         }
1866                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
1867                 }
1868
1869                 return $retval;
1870         }
1871
1872         /**
1873          * Get the aliased table name clause for a FROM clause
1874          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
1875          *
1876          * @param array $tables ( [alias] => table )
1877          * @param array $use_index Same as for select()
1878          * @param array $ignore_index Same as for select()
1879          * @param array $join_conds Same as for select()
1880          * @return string
1881          */
1882         protected function tableNamesWithIndexClauseOrJOIN(
1883                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
1884         ) {
1885                 $ret = [];
1886                 $retJOIN = [];
1887                 $use_index = (array)$use_index;
1888                 $ignore_index = (array)$ignore_index;
1889                 $join_conds = (array)$join_conds;
1890
1891                 foreach ( $tables as $alias => $table ) {
1892                         if ( !is_string( $alias ) ) {
1893                                 // No alias? Set it equal to the table name
1894                                 $alias = $table;
1895                         }
1896                         // Is there a JOIN clause for this table?
1897                         if ( isset( $join_conds[$alias] ) ) {
1898                                 list( $joinType, $conds ) = $join_conds[$alias];
1899                                 $tableClause = $joinType;
1900                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
1901                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
1902                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
1903                                         if ( $use != '' ) {
1904                                                 $tableClause .= ' ' . $use;
1905                                         }
1906                                 }
1907                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
1908                                         $ignore = $this->ignoreIndexClause(
1909                                                 implode( ',', (array)$ignore_index[$alias] ) );
1910                                         if ( $ignore != '' ) {
1911                                                 $tableClause .= ' ' . $ignore;
1912                                         }
1913                                 }
1914                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
1915                                 if ( $on != '' ) {
1916                                         $tableClause .= ' ON (' . $on . ')';
1917                                 }
1918
1919                                 $retJOIN[] = $tableClause;
1920                         } elseif ( isset( $use_index[$alias] ) ) {
1921                                 // Is there an INDEX clause for this table?
1922                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
1923                                 $tableClause .= ' ' . $this->useIndexClause(
1924                                                 implode( ',', (array)$use_index[$alias] )
1925                                         );
1926
1927                                 $ret[] = $tableClause;
1928                         } elseif ( isset( $ignore_index[$alias] ) ) {
1929                                 // Is there an INDEX clause for this table?
1930                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
1931                                 $tableClause .= ' ' . $this->ignoreIndexClause(
1932                                                 implode( ',', (array)$ignore_index[$alias] )
1933                                         );
1934
1935                                 $ret[] = $tableClause;
1936                         } else {
1937                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
1938
1939                                 $ret[] = $tableClause;
1940                         }
1941                 }
1942
1943                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
1944                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
1945                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
1946
1947                 // Compile our final table clause
1948                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
1949         }
1950
1951         /**
1952          * Get the name of an index in a given table.
1953          *
1954          * @param string $index
1955          * @return string
1956          */
1957         protected function indexName( $index ) {
1958                 return $index;
1959         }
1960
1961         public function addQuotes( $s ) {
1962                 if ( $s instanceof Blob ) {
1963                         $s = $s->fetch();
1964                 }
1965                 if ( $s === null ) {
1966                         return 'NULL';
1967                 } elseif ( is_bool( $s ) ) {
1968                         return (int)$s;
1969                 } else {
1970                         # This will also quote numeric values. This should be harmless,
1971                         # and protects against weird problems that occur when they really
1972                         # _are_ strings such as article titles and string->number->string
1973                         # conversion is not 1:1.
1974                         return "'" . $this->strencode( $s ) . "'";
1975                 }
1976         }
1977
1978         /**
1979          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
1980          * MySQL uses `backticks` while basically everything else uses double quotes.
1981          * Since MySQL is the odd one out here the double quotes are our generic
1982          * and we implement backticks in DatabaseMysql.
1983          *
1984          * @param string $s
1985          * @return string
1986          */
1987         public function addIdentifierQuotes( $s ) {
1988                 return '"' . str_replace( '"', '""', $s ) . '"';
1989         }
1990
1991         /**
1992          * Returns if the given identifier looks quoted or not according to
1993          * the database convention for quoting identifiers .
1994          *
1995          * @note Do not use this to determine if untrusted input is safe.
1996          *   A malicious user can trick this function.
1997          * @param string $name
1998          * @return bool
1999          */
2000         public function isQuotedIdentifier( $name ) {
2001                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2002         }
2003
2004         /**
2005          * @param string $s
2006          * @return string
2007          */
2008         protected function escapeLikeInternal( $s ) {
2009                 return addcslashes( $s, '\%_' );
2010         }
2011
2012         public function buildLike() {
2013                 $params = func_get_args();
2014
2015                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2016                         $params = $params[0];
2017                 }
2018
2019                 $s = '';
2020
2021                 foreach ( $params as $value ) {
2022                         if ( $value instanceof LikeMatch ) {
2023                                 $s .= $value->toString();
2024                         } else {
2025                                 $s .= $this->escapeLikeInternal( $value );
2026                         }
2027                 }
2028
2029                 return " LIKE {$this->addQuotes( $s )} ";
2030         }
2031
2032         public function anyChar() {
2033                 return new LikeMatch( '_' );
2034         }
2035
2036         public function anyString() {
2037                 return new LikeMatch( '%' );
2038         }
2039
2040         public function nextSequenceValue( $seqName ) {
2041                 return null;
2042         }
2043
2044         /**
2045          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2046          * is only needed because a) MySQL must be as efficient as possible due to
2047          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2048          * which index to pick. Anyway, other databases might have different
2049          * indexes on a given table. So don't bother overriding this unless you're
2050          * MySQL.
2051          * @param string $index
2052          * @return string
2053          */
2054         public function useIndexClause( $index ) {
2055                 return '';
2056         }
2057
2058         /**
2059          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2060          * is only needed because a) MySQL must be as efficient as possible due to
2061          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2062          * which index to pick. Anyway, other databases might have different
2063          * indexes on a given table. So don't bother overriding this unless you're
2064          * MySQL.
2065          * @param string $index
2066          * @return string
2067          */
2068         public function ignoreIndexClause( $index ) {
2069                 return '';
2070         }
2071
2072         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2073                 $quotedTable = $this->tableName( $table );
2074
2075                 if ( count( $rows ) == 0 ) {
2076                         return;
2077                 }
2078
2079                 # Single row case
2080                 if ( !is_array( reset( $rows ) ) ) {
2081                         $rows = [ $rows ];
2082                 }
2083
2084                 // @FXIME: this is not atomic, but a trx would break affectedRows()
2085                 foreach ( $rows as $row ) {
2086                         # Delete rows which collide
2087                         if ( $uniqueIndexes ) {
2088                                 $sql = "DELETE FROM $quotedTable WHERE ";
2089                                 $first = true;
2090                                 foreach ( $uniqueIndexes as $index ) {
2091                                         if ( $first ) {
2092                                                 $first = false;
2093                                                 $sql .= '( ';
2094                                         } else {
2095                                                 $sql .= ' ) OR ( ';
2096                                         }
2097                                         if ( is_array( $index ) ) {
2098                                                 $first2 = true;
2099                                                 foreach ( $index as $col ) {
2100                                                         if ( $first2 ) {
2101                                                                 $first2 = false;
2102                                                         } else {
2103                                                                 $sql .= ' AND ';
2104                                                         }
2105                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2106                                                 }
2107                                         } else {
2108                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2109                                         }
2110                                 }
2111                                 $sql .= ' )';
2112                                 $this->query( $sql, $fname );
2113                         }
2114
2115                         # Now insert the row
2116                         $this->insert( $table, $row, $fname );
2117                 }
2118         }
2119
2120         /**
2121          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2122          * statement.
2123          *
2124          * @param string $table Table name
2125          * @param array|string $rows Row(s) to insert
2126          * @param string $fname Caller function name
2127          *
2128          * @return ResultWrapper
2129          */
2130         protected function nativeReplace( $table, $rows, $fname ) {
2131                 $table = $this->tableName( $table );
2132
2133                 # Single row case
2134                 if ( !is_array( reset( $rows ) ) ) {
2135                         $rows = [ $rows ];
2136                 }
2137
2138                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2139                 $first = true;
2140
2141                 foreach ( $rows as $row ) {
2142                         if ( $first ) {
2143                                 $first = false;
2144                         } else {
2145                                 $sql .= ',';
2146                         }
2147
2148                         $sql .= '(' . $this->makeList( $row ) . ')';
2149                 }
2150
2151                 return $this->query( $sql, $fname );
2152         }
2153
2154         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2155                 $fname = __METHOD__
2156         ) {
2157                 if ( !count( $rows ) ) {
2158                         return true; // nothing to do
2159                 }
2160
2161                 if ( !is_array( reset( $rows ) ) ) {
2162                         $rows = [ $rows ];
2163                 }
2164
2165                 if ( count( $uniqueIndexes ) ) {
2166                         $clauses = []; // list WHERE clauses that each identify a single row
2167                         foreach ( $rows as $row ) {
2168                                 foreach ( $uniqueIndexes as $index ) {
2169                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2170                                         $rowKey = []; // unique key to this row
2171                                         foreach ( $index as $column ) {
2172                                                 $rowKey[$column] = $row[$column];
2173                                         }
2174                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2175                                 }
2176                         }
2177                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2178                 } else {
2179                         $where = false;
2180                 }
2181
2182                 $useTrx = !$this->mTrxLevel;
2183                 if ( $useTrx ) {
2184                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2185                 }
2186                 try {
2187                         # Update any existing conflicting row(s)
2188                         if ( $where !== false ) {
2189                                 $ok = $this->update( $table, $set, $where, $fname );
2190                         } else {
2191                                 $ok = true;
2192                         }
2193                         # Now insert any non-conflicting row(s)
2194                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2195                 } catch ( Exception $e ) {
2196                         if ( $useTrx ) {
2197                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
2198                         }
2199                         throw $e;
2200                 }
2201                 if ( $useTrx ) {
2202                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2203                 }
2204
2205                 return $ok;
2206         }
2207
2208         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2209                 $fname = __METHOD__
2210         ) {
2211                 if ( !$conds ) {
2212                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2213                 }
2214
2215                 $delTable = $this->tableName( $delTable );
2216                 $joinTable = $this->tableName( $joinTable );
2217                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2218                 if ( $conds != '*' ) {
2219                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2220                 }
2221                 $sql .= ')';
2222
2223                 $this->query( $sql, $fname );
2224         }
2225
2226         public function textFieldSize( $table, $field ) {
2227                 $table = $this->tableName( $table );
2228                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2229                 $res = $this->query( $sql, __METHOD__ );
2230                 $row = $this->fetchObject( $res );
2231
2232                 $m = [];
2233
2234                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2235                         $size = $m[1];
2236                 } else {
2237                         $size = -1;
2238                 }
2239
2240                 return $size;
2241         }
2242
2243         public function delete( $table, $conds, $fname = __METHOD__ ) {
2244                 if ( !$conds ) {
2245                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2246                 }
2247
2248                 $table = $this->tableName( $table );
2249                 $sql = "DELETE FROM $table";
2250
2251                 if ( $conds != '*' ) {
2252                         if ( is_array( $conds ) ) {
2253                                 $conds = $this->makeList( $conds, self::LIST_AND );
2254                         }
2255                         $sql .= ' WHERE ' . $conds;
2256                 }
2257
2258                 return $this->query( $sql, $fname );
2259         }
2260
2261         public function insertSelect(
2262                 $destTable, $srcTable, $varMap, $conds,
2263                 $fname = __METHOD__, $insertOptions = [], $selectOptions = []
2264         ) {
2265                 if ( $this->cliMode ) {
2266                         // For massive migrations with downtime, we don't want to select everything
2267                         // into memory and OOM, so do all this native on the server side if possible.
2268                         return $this->nativeInsertSelect(
2269                                 $destTable,
2270                                 $srcTable,
2271                                 $varMap,
2272                                 $conds,
2273                                 $fname,
2274                                 $insertOptions,
2275                                 $selectOptions
2276                         );
2277                 }
2278
2279                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
2280                 // on only the master (without needing row-based-replication). It also makes it easy to
2281                 // know how big the INSERT is going to be.
2282                 $fields = [];
2283                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
2284                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
2285                 }
2286                 $selectOptions[] = 'FOR UPDATE';
2287                 $res = $this->select( $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions );
2288                 if ( !$res ) {
2289                         return false;
2290                 }
2291
2292                 $rows = [];
2293                 foreach ( $res as $row ) {
2294                         $rows[] = (array)$row;
2295                 }
2296
2297                 return $this->insert( $destTable, $rows, $fname, $insertOptions );
2298         }
2299
2300         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2301                 $fname = __METHOD__,
2302                 $insertOptions = [], $selectOptions = []
2303         ) {
2304                 $destTable = $this->tableName( $destTable );
2305
2306                 if ( !is_array( $insertOptions ) ) {
2307                         $insertOptions = [ $insertOptions ];
2308                 }
2309
2310                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2311
2312                 if ( !is_array( $selectOptions ) ) {
2313                         $selectOptions = [ $selectOptions ];
2314                 }
2315
2316                 list( $startOpts, $useIndex, $tailOpts, $ignoreIndex ) = $this->makeSelectOptions(
2317                         $selectOptions );
2318
2319                 if ( is_array( $srcTable ) ) {
2320                         $srcTable = implode( ',', array_map( [ $this, 'tableName' ], $srcTable ) );
2321                 } else {
2322                         $srcTable = $this->tableName( $srcTable );
2323                 }
2324
2325                 $sql = "INSERT $insertOptions" .
2326                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2327                         " SELECT $startOpts " . implode( ',', $varMap ) .
2328                         " FROM $srcTable $useIndex $ignoreIndex ";
2329
2330                 if ( $conds != '*' ) {
2331                         if ( is_array( $conds ) ) {
2332                                 $conds = $this->makeList( $conds, self::LIST_AND );
2333                         }
2334                         $sql .= " WHERE $conds";
2335                 }
2336
2337                 $sql .= " $tailOpts";
2338
2339                 return $this->query( $sql, $fname );
2340         }
2341
2342         /**
2343          * Construct a LIMIT query with optional offset. This is used for query
2344          * pages. The SQL should be adjusted so that only the first $limit rows
2345          * are returned. If $offset is provided as well, then the first $offset
2346          * rows should be discarded, and the next $limit rows should be returned.
2347          * If the result of the query is not ordered, then the rows to be returned
2348          * are theoretically arbitrary.
2349          *
2350          * $sql is expected to be a SELECT, if that makes a difference.
2351          *
2352          * The version provided by default works in MySQL and SQLite. It will very
2353          * likely need to be overridden for most other DBMSes.
2354          *
2355          * @param string $sql SQL query we will append the limit too
2356          * @param int $limit The SQL limit
2357          * @param int|bool $offset The SQL offset (default false)
2358          * @throws DBUnexpectedError
2359          * @return string
2360          */
2361         public function limitResult( $sql, $limit, $offset = false ) {
2362                 if ( !is_numeric( $limit ) ) {
2363                         throw new DBUnexpectedError( $this,
2364                                 "Invalid non-numeric limit passed to limitResult()\n" );
2365                 }
2366
2367                 return "$sql LIMIT "
2368                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2369                 . "{$limit} ";
2370         }
2371
2372         public function unionSupportsOrderAndLimit() {
2373                 return true; // True for almost every DB supported
2374         }
2375
2376         public function unionQueries( $sqls, $all ) {
2377                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2378
2379                 return '(' . implode( $glue, $sqls ) . ')';
2380         }
2381
2382         public function conditional( $cond, $trueVal, $falseVal ) {
2383                 if ( is_array( $cond ) ) {
2384                         $cond = $this->makeList( $cond, self::LIST_AND );
2385                 }
2386
2387                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2388         }
2389
2390         public function strreplace( $orig, $old, $new ) {
2391                 return "REPLACE({$orig}, {$old}, {$new})";
2392         }
2393
2394         public function getServerUptime() {
2395                 return 0;
2396         }
2397
2398         public function wasDeadlock() {
2399                 return false;
2400         }
2401
2402         public function wasLockTimeout() {
2403                 return false;
2404         }
2405
2406         public function wasErrorReissuable() {
2407                 return false;
2408         }
2409
2410         public function wasReadOnlyError() {
2411                 return false;
2412         }
2413
2414         /**
2415          * Do not use this method outside of Database/DBError classes
2416          *
2417          * @param integer|string $errno
2418          * @return bool Whether the given query error was a connection drop
2419          */
2420         public function wasConnectionError( $errno ) {
2421                 return false;
2422         }
2423
2424         public function deadlockLoop() {
2425                 $args = func_get_args();
2426                 $function = array_shift( $args );
2427                 $tries = self::DEADLOCK_TRIES;
2428
2429                 $this->begin( __METHOD__ );
2430
2431                 $retVal = null;
2432                 /** @var Exception $e */
2433                 $e = null;
2434                 do {
2435                         try {
2436                                 $retVal = call_user_func_array( $function, $args );
2437                                 break;
2438                         } catch ( DBQueryError $e ) {
2439                                 if ( $this->wasDeadlock() ) {
2440                                         // Retry after a randomized delay
2441                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
2442                                 } else {
2443                                         // Throw the error back up
2444                                         throw $e;
2445                                 }
2446                         }
2447                 } while ( --$tries > 0 );
2448
2449                 if ( $tries <= 0 ) {
2450                         // Too many deadlocks; give up
2451                         $this->rollback( __METHOD__ );
2452                         throw $e;
2453                 } else {
2454                         $this->commit( __METHOD__ );
2455
2456                         return $retVal;
2457                 }
2458         }
2459
2460         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2461                 # Real waits are implemented in the subclass.
2462                 return 0;
2463         }
2464
2465         public function getReplicaPos() {
2466                 # Stub
2467                 return false;
2468         }
2469
2470         public function getMasterPos() {
2471                 # Stub
2472                 return false;
2473         }
2474
2475         public function serverIsReadOnly() {
2476                 return false;
2477         }
2478
2479         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
2480                 if ( !$this->mTrxLevel ) {
2481                         throw new DBUnexpectedError( $this, "No transaction is active." );
2482                 }
2483                 $this->mTrxEndCallbacks[] = [ $callback, $fname ];
2484         }
2485
2486         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
2487                 $this->mTrxIdleCallbacks[] = [ $callback, $fname ];
2488                 if ( !$this->mTrxLevel ) {
2489                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
2490                 }
2491         }
2492
2493         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
2494                 if ( $this->mTrxLevel ) {
2495                         $this->mTrxPreCommitCallbacks[] = [ $callback, $fname ];
2496                 } else {
2497                         // If no transaction is active, then make one for this callback
2498                         $this->startAtomic( __METHOD__ );
2499                         try {
2500                                 call_user_func( $callback );
2501                                 $this->endAtomic( __METHOD__ );
2502                         } catch ( Exception $e ) {
2503                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2504                                 throw $e;
2505                         }
2506                 }
2507         }
2508
2509         final public function setTransactionListener( $name, callable $callback = null ) {
2510                 if ( $callback ) {
2511                         $this->mTrxRecurringCallbacks[$name] = $callback;
2512                 } else {
2513                         unset( $this->mTrxRecurringCallbacks[$name] );
2514                 }
2515         }
2516
2517         /**
2518          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
2519          *
2520          * This method should not be used outside of Database/LoadBalancer
2521          *
2522          * @param bool $suppress
2523          * @since 1.28
2524          */
2525         final public function setTrxEndCallbackSuppression( $suppress ) {
2526                 $this->mTrxEndCallbacksSuppressed = $suppress;
2527         }
2528
2529         /**
2530          * Actually run and consume any "on transaction idle/resolution" callbacks.
2531          *
2532          * This method should not be used outside of Database/LoadBalancer
2533          *
2534          * @param integer $trigger IDatabase::TRIGGER_* constant
2535          * @since 1.20
2536          * @throws Exception
2537          */
2538         public function runOnTransactionIdleCallbacks( $trigger ) {
2539                 if ( $this->mTrxEndCallbacksSuppressed ) {
2540                         return;
2541                 }
2542
2543                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
2544                 /** @var Exception $e */
2545                 $e = null; // first exception
2546                 do { // callbacks may add callbacks :)
2547                         $callbacks = array_merge(
2548                                 $this->mTrxIdleCallbacks,
2549                                 $this->mTrxEndCallbacks // include "transaction resolution" callbacks
2550                         );
2551                         $this->mTrxIdleCallbacks = []; // consumed (and recursion guard)
2552                         $this->mTrxEndCallbacks = []; // consumed (recursion guard)
2553                         foreach ( $callbacks as $callback ) {
2554                                 try {
2555                                         list( $phpCallback ) = $callback;
2556                                         $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
2557                                         call_user_func_array( $phpCallback, [ $trigger ] );
2558                                         if ( $autoTrx ) {
2559                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
2560                                         } else {
2561                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
2562                                         }
2563                                 } catch ( Exception $ex ) {
2564                                         call_user_func( $this->errorLogger, $ex );
2565                                         $e = $e ?: $ex;
2566                                         // Some callbacks may use startAtomic/endAtomic, so make sure
2567                                         // their transactions are ended so other callbacks don't fail
2568                                         if ( $this->trxLevel() ) {
2569                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2570                                         }
2571                                 }
2572                         }
2573                 } while ( count( $this->mTrxIdleCallbacks ) );
2574
2575                 if ( $e instanceof Exception ) {
2576                         throw $e; // re-throw any first exception
2577                 }
2578         }
2579
2580         /**
2581          * Actually run and consume any "on transaction pre-commit" callbacks.
2582          *
2583          * This method should not be used outside of Database/LoadBalancer
2584          *
2585          * @since 1.22
2586          * @throws Exception
2587          */
2588         public function runOnTransactionPreCommitCallbacks() {
2589                 $e = null; // first exception
2590                 do { // callbacks may add callbacks :)
2591                         $callbacks = $this->mTrxPreCommitCallbacks;
2592                         $this->mTrxPreCommitCallbacks = []; // consumed (and recursion guard)
2593                         foreach ( $callbacks as $callback ) {
2594                                 try {
2595                                         list( $phpCallback ) = $callback;
2596                                         call_user_func( $phpCallback );
2597                                 } catch ( Exception $ex ) {
2598                                         call_user_func( $this->errorLogger, $ex );
2599                                         $e = $e ?: $ex;
2600                                 }
2601                         }
2602                 } while ( count( $this->mTrxPreCommitCallbacks ) );
2603
2604                 if ( $e instanceof Exception ) {
2605                         throw $e; // re-throw any first exception
2606                 }
2607         }
2608
2609         /**
2610          * Actually run any "transaction listener" callbacks.
2611          *
2612          * This method should not be used outside of Database/LoadBalancer
2613          *
2614          * @param integer $trigger IDatabase::TRIGGER_* constant
2615          * @throws Exception
2616          * @since 1.20
2617          */
2618         public function runTransactionListenerCallbacks( $trigger ) {
2619                 if ( $this->mTrxEndCallbacksSuppressed ) {
2620                         return;
2621                 }
2622
2623                 /** @var Exception $e */
2624                 $e = null; // first exception
2625
2626                 foreach ( $this->mTrxRecurringCallbacks as $phpCallback ) {
2627                         try {
2628                                 $phpCallback( $trigger, $this );
2629                         } catch ( Exception $ex ) {
2630                                 call_user_func( $this->errorLogger, $ex );
2631                                 $e = $e ?: $ex;
2632                         }
2633                 }
2634
2635                 if ( $e instanceof Exception ) {
2636                         throw $e; // re-throw any first exception
2637                 }
2638         }
2639
2640         final public function startAtomic( $fname = __METHOD__ ) {
2641                 if ( !$this->mTrxLevel ) {
2642                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2643                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
2644                         // in all changes being in one transaction to keep requests transactional.
2645                         if ( !$this->getFlag( self::DBO_TRX ) ) {
2646                                 $this->mTrxAutomaticAtomic = true;
2647                         }
2648                 }
2649
2650                 $this->mTrxAtomicLevels[] = $fname;
2651         }
2652
2653         final public function endAtomic( $fname = __METHOD__ ) {
2654                 if ( !$this->mTrxLevel ) {
2655                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
2656                 }
2657                 if ( !$this->mTrxAtomicLevels ||
2658                         array_pop( $this->mTrxAtomicLevels ) !== $fname
2659                 ) {
2660                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
2661                 }
2662
2663                 if ( !$this->mTrxAtomicLevels && $this->mTrxAutomaticAtomic ) {
2664                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2665                 }
2666         }
2667
2668         final public function doAtomicSection( $fname, callable $callback ) {
2669                 $this->startAtomic( $fname );
2670                 try {
2671                         $res = call_user_func_array( $callback, [ $this, $fname ] );
2672                 } catch ( Exception $e ) {
2673                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2674                         throw $e;
2675                 }
2676                 $this->endAtomic( $fname );
2677
2678                 return $res;
2679         }
2680
2681         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
2682                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
2683                 if ( $this->mTrxLevel ) {
2684                         if ( $this->mTrxAtomicLevels ) {
2685                                 $levels = implode( ', ', $this->mTrxAtomicLevels );
2686                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
2687                                 throw new DBUnexpectedError( $this, $msg );
2688                         } elseif ( !$this->mTrxAutomatic ) {
2689                                 $msg = "$fname: Explicit transaction already active (from {$this->mTrxFname}).";
2690                                 throw new DBUnexpectedError( $this, $msg );
2691                         } else {
2692                                 // @TODO: make this an exception at some point
2693                                 $msg = "$fname: Implicit transaction already active (from {$this->mTrxFname}).";
2694                                 $this->queryLogger->error( $msg );
2695                                 return; // join the main transaction set
2696                         }
2697                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
2698                         // @TODO: make this an exception at some point
2699                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
2700                         $this->queryLogger->error( $msg );
2701                         return; // let any writes be in the main transaction
2702                 }
2703
2704                 // Avoid fatals if close() was called
2705                 $this->assertOpen();
2706
2707                 $this->doBegin( $fname );
2708                 $this->mTrxTimestamp = microtime( true );
2709                 $this->mTrxFname = $fname;
2710                 $this->mTrxDoneWrites = false;
2711                 $this->mTrxAutomaticAtomic = false;
2712                 $this->mTrxAtomicLevels = [];
2713                 $this->mTrxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
2714                 $this->mTrxWriteDuration = 0.0;
2715                 $this->mTrxWriteQueryCount = 0;
2716                 $this->mTrxWriteAdjDuration = 0.0;
2717                 $this->mTrxWriteAdjQueryCount = 0;
2718                 $this->mTrxWriteCallers = [];
2719                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
2720                 // Get an estimate of the replica DB lag before then, treating estimate staleness
2721                 // as lag itself just to be safe
2722                 $status = $this->getApproximateLagStatus();
2723                 $this->mTrxReplicaLag = $status['lag'] + ( microtime( true ) - $status['since'] );
2724                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
2725                 // caller will think its OK to muck around with the transaction just because startAtomic()
2726                 // has not yet completed (e.g. setting mTrxAtomicLevels).
2727                 $this->mTrxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
2728         }
2729
2730         /**
2731          * Issues the BEGIN command to the database server.
2732          *
2733          * @see Database::begin()
2734          * @param string $fname
2735          */
2736         protected function doBegin( $fname ) {
2737                 $this->query( 'BEGIN', $fname );
2738                 $this->mTrxLevel = 1;
2739         }
2740
2741         final public function commit( $fname = __METHOD__, $flush = '' ) {
2742                 if ( $this->mTrxLevel && $this->mTrxAtomicLevels ) {
2743                         // There are still atomic sections open. This cannot be ignored
2744                         $levels = implode( ', ', $this->mTrxAtomicLevels );
2745                         throw new DBUnexpectedError(
2746                                 $this,
2747                                 "$fname: Got COMMIT while atomic sections $levels are still open."
2748                         );
2749                 }
2750
2751                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
2752                         if ( !$this->mTrxLevel ) {
2753                                 return; // nothing to do
2754                         } elseif ( !$this->mTrxAutomatic ) {
2755                                 throw new DBUnexpectedError(
2756                                         $this,
2757                                         "$fname: Flushing an explicit transaction, getting out of sync."
2758                                 );
2759                         }
2760                 } else {
2761                         if ( !$this->mTrxLevel ) {
2762                                 $this->queryLogger->error(
2763                                         "$fname: No transaction to commit, something got out of sync." );
2764                                 return; // nothing to do
2765                         } elseif ( $this->mTrxAutomatic ) {
2766                                 // @TODO: make this an exception at some point
2767                                 $msg = "$fname: Explicit commit of implicit transaction.";
2768                                 $this->queryLogger->error( $msg );
2769                                 return; // wait for the main transaction set commit round
2770                         }
2771                 }
2772
2773                 // Avoid fatals if close() was called
2774                 $this->assertOpen();
2775
2776                 $this->runOnTransactionPreCommitCallbacks();
2777                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
2778                 $this->doCommit( $fname );
2779                 if ( $this->mTrxDoneWrites ) {
2780                         $this->mLastWriteTime = microtime( true );
2781                         $this->trxProfiler->transactionWritingOut(
2782                                 $this->mServer, $this->mDBname, $this->mTrxShortId, $writeTime );
2783                 }
2784
2785                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
2786                 $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
2787         }
2788
2789         /**
2790          * Issues the COMMIT command to the database server.
2791          *
2792          * @see Database::commit()
2793          * @param string $fname
2794          */
2795         protected function doCommit( $fname ) {
2796                 if ( $this->mTrxLevel ) {
2797                         $this->query( 'COMMIT', $fname );
2798                         $this->mTrxLevel = 0;
2799                 }
2800         }
2801
2802         final public function rollback( $fname = __METHOD__, $flush = '' ) {
2803                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
2804                         if ( !$this->mTrxLevel ) {
2805                                 return; // nothing to do
2806                         }
2807                 } else {
2808                         if ( !$this->mTrxLevel ) {
2809                                 $this->queryLogger->error(
2810                                         "$fname: No transaction to rollback, something got out of sync." );
2811                                 return; // nothing to do
2812                         } elseif ( $this->getFlag( self::DBO_TRX ) ) {
2813                                 throw new DBUnexpectedError(
2814                                         $this,
2815                                         "$fname: Expected mass rollback of all peer databases (DBO_TRX set)."
2816                                 );
2817                         }
2818                 }
2819
2820                 // Avoid fatals if close() was called
2821                 $this->assertOpen();
2822
2823                 $this->doRollback( $fname );
2824                 $this->mTrxAtomicLevels = [];
2825                 if ( $this->mTrxDoneWrites ) {
2826                         $this->trxProfiler->transactionWritingOut(
2827                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
2828                 }
2829
2830                 $this->mTrxIdleCallbacks = []; // clear
2831                 $this->mTrxPreCommitCallbacks = []; // clear
2832                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
2833                 $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
2834         }
2835
2836         /**
2837          * Issues the ROLLBACK command to the database server.
2838          *
2839          * @see Database::rollback()
2840          * @param string $fname
2841          */
2842         protected function doRollback( $fname ) {
2843                 if ( $this->mTrxLevel ) {
2844                         # Disconnects cause rollback anyway, so ignore those errors
2845                         $ignoreErrors = true;
2846                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
2847                         $this->mTrxLevel = 0;
2848                 }
2849         }
2850
2851         public function flushSnapshot( $fname = __METHOD__ ) {
2852                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
2853                         // This only flushes transactions to clear snapshots, not to write data
2854                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
2855                         throw new DBUnexpectedError(
2856                                 $this,
2857                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
2858                         );
2859                 }
2860
2861                 $this->commit( $fname, self::FLUSHING_INTERNAL );
2862         }
2863
2864         public function explicitTrxActive() {
2865                 return $this->mTrxLevel && ( $this->mTrxAtomicLevels || !$this->mTrxAutomatic );
2866         }
2867
2868         public function duplicateTableStructure(
2869                 $oldName, $newName, $temporary = false, $fname = __METHOD__
2870         ) {
2871                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
2872         }
2873
2874         public function listTables( $prefix = null, $fname = __METHOD__ ) {
2875                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
2876         }
2877
2878         public function listViews( $prefix = null, $fname = __METHOD__ ) {
2879                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
2880         }
2881
2882         public function timestamp( $ts = 0 ) {
2883                 $t = new ConvertibleTimestamp( $ts );
2884                 // Let errors bubble up to avoid putting garbage in the DB
2885                 return $t->getTimestamp( TS_MW );
2886         }
2887
2888         public function timestampOrNull( $ts = null ) {
2889                 if ( is_null( $ts ) ) {
2890                         return null;
2891                 } else {
2892                         return $this->timestamp( $ts );
2893                 }
2894         }
2895
2896         /**
2897          * Take the result from a query, and wrap it in a ResultWrapper if
2898          * necessary. Boolean values are passed through as is, to indicate success
2899          * of write queries or failure.
2900          *
2901          * Once upon a time, Database::query() returned a bare MySQL result
2902          * resource, and it was necessary to call this function to convert it to
2903          * a wrapper. Nowadays, raw database objects are never exposed to external
2904          * callers, so this is unnecessary in external code.
2905          *
2906          * @param bool|ResultWrapper|resource|object $result
2907          * @return bool|ResultWrapper
2908          */
2909         protected function resultObject( $result ) {
2910                 if ( !$result ) {
2911                         return false;
2912                 } elseif ( $result instanceof ResultWrapper ) {
2913                         return $result;
2914                 } elseif ( $result === true ) {
2915                         // Successful write query
2916                         return $result;
2917                 } else {
2918                         return new ResultWrapper( $this, $result );
2919                 }
2920         }
2921
2922         public function ping( &$rtt = null ) {
2923                 // Avoid hitting the server if it was hit recently
2924                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
2925                         if ( !func_num_args() || $this->mRTTEstimate > 0 ) {
2926                                 $rtt = $this->mRTTEstimate;
2927                                 return true; // don't care about $rtt
2928                         }
2929                 }
2930
2931                 // This will reconnect if possible or return false if not
2932                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
2933                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
2934                 $this->restoreFlags( self::RESTORE_PRIOR );
2935
2936                 if ( $ok ) {
2937                         $rtt = $this->mRTTEstimate;
2938                 }
2939
2940                 return $ok;
2941         }
2942
2943         /**
2944          * @return bool
2945          */
2946         protected function reconnect() {
2947                 $this->closeConnection();
2948                 $this->mOpened = false;
2949                 $this->mConn = false;
2950                 try {
2951                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
2952                         $this->lastPing = microtime( true );
2953                         $ok = true;
2954                 } catch ( DBConnectionError $e ) {
2955                         $ok = false;
2956                 }
2957
2958                 return $ok;
2959         }
2960
2961         public function getSessionLagStatus() {
2962                 return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
2963         }
2964
2965         /**
2966          * Get the replica DB lag when the current transaction started
2967          *
2968          * This is useful when transactions might use snapshot isolation
2969          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
2970          * is this lag plus transaction duration. If they don't, it is still
2971          * safe to be pessimistic. This returns null if there is no transaction.
2972          *
2973          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
2974          * @since 1.27
2975          */
2976         protected function getTransactionLagStatus() {
2977                 return $this->mTrxLevel
2978                         ? [ 'lag' => $this->mTrxReplicaLag, 'since' => $this->trxTimestamp() ]
2979                         : null;
2980         }
2981
2982         /**
2983          * Get a replica DB lag estimate for this server
2984          *
2985          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
2986          * @since 1.27
2987          */
2988         protected function getApproximateLagStatus() {
2989                 return [
2990                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
2991                         'since' => microtime( true )
2992                 ];
2993         }
2994
2995         /**
2996          * Merge the result of getSessionLagStatus() for several DBs
2997          * using the most pessimistic values to estimate the lag of
2998          * any data derived from them in combination
2999          *
3000          * This is information is useful for caching modules
3001          *
3002          * @see WANObjectCache::set()
3003          * @see WANObjectCache::getWithSetCallback()
3004          *
3005          * @param IDatabase $db1
3006          * @param IDatabase ...
3007          * @return array Map of values:
3008          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3009          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3010          *   - pending: whether any of the DBs have uncommitted changes
3011          * @since 1.27
3012          */
3013         public static function getCacheSetOptions( IDatabase $db1 ) {
3014                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3015                 foreach ( func_get_args() as $db ) {
3016                         /** @var IDatabase $db */
3017                         $status = $db->getSessionLagStatus();
3018                         if ( $status['lag'] === false ) {
3019                                 $res['lag'] = false;
3020                         } elseif ( $res['lag'] !== false ) {
3021                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3022                         }
3023                         $res['since'] = min( $res['since'], $status['since'] );
3024                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3025                 }
3026
3027                 return $res;
3028         }
3029
3030         public function getLag() {
3031                 return 0;
3032         }
3033
3034         public function maxListLen() {
3035                 return 0;
3036         }
3037
3038         public function encodeBlob( $b ) {
3039                 return $b;
3040         }
3041
3042         public function decodeBlob( $b ) {
3043                 if ( $b instanceof Blob ) {
3044                         $b = $b->fetch();
3045                 }
3046                 return $b;
3047         }
3048
3049         public function setSessionOptions( array $options ) {
3050         }
3051
3052         public function sourceFile(
3053                 $filename,
3054                 callable $lineCallback = null,
3055                 callable $resultCallback = null,
3056                 $fname = false,
3057                 callable $inputCallback = null
3058         ) {
3059                 MediaWiki\suppressWarnings();
3060                 $fp = fopen( $filename, 'r' );
3061                 MediaWiki\restoreWarnings();
3062
3063                 if ( false === $fp ) {
3064                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
3065                 }
3066
3067                 if ( !$fname ) {
3068                         $fname = __METHOD__ . "( $filename )";
3069                 }
3070
3071                 try {
3072                         $error = $this->sourceStream(
3073                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3074                 } catch ( Exception $e ) {
3075                         fclose( $fp );
3076                         throw $e;
3077                 }
3078
3079                 fclose( $fp );
3080
3081                 return $error;
3082         }
3083
3084         public function setSchemaVars( $vars ) {
3085                 $this->mSchemaVars = $vars;
3086         }
3087
3088         public function sourceStream(
3089                 $fp,
3090                 callable $lineCallback = null,
3091                 callable $resultCallback = null,
3092                 $fname = __METHOD__,
3093                 callable $inputCallback = null
3094         ) {
3095                 $cmd = '';
3096
3097                 while ( !feof( $fp ) ) {
3098                         if ( $lineCallback ) {
3099                                 call_user_func( $lineCallback );
3100                         }
3101
3102                         $line = trim( fgets( $fp ) );
3103
3104                         if ( $line == '' ) {
3105                                 continue;
3106                         }
3107
3108                         if ( '-' == $line[0] && '-' == $line[1] ) {
3109                                 continue;
3110                         }
3111
3112                         if ( $cmd != '' ) {
3113                                 $cmd .= ' ';
3114                         }
3115
3116                         $done = $this->streamStatementEnd( $cmd, $line );
3117
3118                         $cmd .= "$line\n";
3119
3120                         if ( $done || feof( $fp ) ) {
3121                                 $cmd = $this->replaceVars( $cmd );
3122
3123                                 if ( !$inputCallback || call_user_func( $inputCallback, $cmd ) ) {
3124                                         $res = $this->query( $cmd, $fname );
3125
3126                                         if ( $resultCallback ) {
3127                                                 call_user_func( $resultCallback, $res, $this );
3128                                         }
3129
3130                                         if ( false === $res ) {
3131                                                 $err = $this->lastError();
3132
3133                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3134                                         }
3135                                 }
3136                                 $cmd = '';
3137                         }
3138                 }
3139
3140                 return true;
3141         }
3142
3143         /**
3144          * Called by sourceStream() to check if we've reached a statement end
3145          *
3146          * @param string &$sql SQL assembled so far
3147          * @param string &$newLine New line about to be added to $sql
3148          * @return bool Whether $newLine contains end of the statement
3149          */
3150         public function streamStatementEnd( &$sql, &$newLine ) {
3151                 if ( $this->delimiter ) {
3152                         $prev = $newLine;
3153                         $newLine = preg_replace(
3154                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3155                         if ( $newLine != $prev ) {
3156                                 return true;
3157                         }
3158                 }
3159
3160                 return false;
3161         }
3162
3163         /**
3164          * Database independent variable replacement. Replaces a set of variables
3165          * in an SQL statement with their contents as given by $this->getSchemaVars().
3166          *
3167          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3168          *
3169          * - '{$var}' should be used for text and is passed through the database's
3170          *   addQuotes method.
3171          * - `{$var}` should be used for identifiers (e.g. table and database names).
3172          *   It is passed through the database's addIdentifierQuotes method which
3173          *   can be overridden if the database uses something other than backticks.
3174          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
3175          *   database's tableName method.
3176          * - / *i* / passes the name that follows through the database's indexName method.
3177          * - In all other cases, / *$var* / is left unencoded. Except for table options,
3178          *   its use should be avoided. In 1.24 and older, string encoding was applied.
3179          *
3180          * @param string $ins SQL statement to replace variables in
3181          * @return string The new SQL statement with variables replaced
3182          */
3183         protected function replaceVars( $ins ) {
3184                 $vars = $this->getSchemaVars();
3185                 return preg_replace_callback(
3186                         '!
3187                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
3188                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
3189                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
3190                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
3191                         !x',
3192                         function ( $m ) use ( $vars ) {
3193                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
3194                                 // check for both nonexistent keys *and* the empty string.
3195                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
3196                                         if ( $m[1] === 'i' ) {
3197                                                 return $this->indexName( $m[2] );
3198                                         } else {
3199                                                 return $this->tableName( $m[2] );
3200                                         }
3201                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
3202                                         return $this->addQuotes( $vars[$m[3]] );
3203                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
3204                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
3205                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
3206                                         return $vars[$m[5]];
3207                                 } else {
3208                                         return $m[0];
3209                                 }
3210                         },
3211                         $ins
3212                 );
3213         }
3214
3215         /**
3216          * Get schema variables. If none have been set via setSchemaVars(), then
3217          * use some defaults from the current object.
3218          *
3219          * @return array
3220          */
3221         protected function getSchemaVars() {
3222                 if ( $this->mSchemaVars ) {
3223                         return $this->mSchemaVars;
3224                 } else {
3225                         return $this->getDefaultSchemaVars();
3226                 }
3227         }
3228
3229         /**
3230          * Get schema variables to use if none have been set via setSchemaVars().
3231          *
3232          * Override this in derived classes to provide variables for tables.sql
3233          * and SQL patch files.
3234          *
3235          * @return array
3236          */
3237         protected function getDefaultSchemaVars() {
3238                 return [];
3239         }
3240
3241         public function lockIsFree( $lockName, $method ) {
3242                 return true;
3243         }
3244
3245         public function lock( $lockName, $method, $timeout = 5 ) {
3246                 $this->mNamedLocksHeld[$lockName] = 1;
3247
3248                 return true;
3249         }
3250
3251         public function unlock( $lockName, $method ) {
3252                 unset( $this->mNamedLocksHeld[$lockName] );
3253
3254                 return true;
3255         }
3256
3257         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
3258                 if ( $this->writesOrCallbacksPending() ) {
3259                         // This only flushes transactions to clear snapshots, not to write data
3260                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3261                         throw new DBUnexpectedError(
3262                                 $this,
3263                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
3264                         );
3265                 }
3266
3267                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
3268                         return null;
3269                 }
3270
3271                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
3272                         if ( $this->trxLevel() ) {
3273                                 // There is a good chance an exception was thrown, causing any early return
3274                                 // from the caller. Let any error handler get a chance to issue rollback().
3275                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
3276                                 $this->onTransactionResolution(
3277                                         function () use ( $lockKey, $fname ) {
3278                                                 $this->unlock( $lockKey, $fname );
3279                                         },
3280                                         $fname
3281                                 );
3282                         } else {
3283                                 $this->unlock( $lockKey, $fname );
3284                         }
3285                 } );
3286
3287                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3288
3289                 return $unlocker;
3290         }
3291
3292         public function namedLocksEnqueue() {
3293                 return false;
3294         }
3295
3296         /**
3297          * Lock specific tables
3298          *
3299          * @param array $read Array of tables to lock for read access
3300          * @param array $write Array of tables to lock for write access
3301          * @param string $method Name of caller
3302          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
3303          * @return bool
3304          */
3305         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3306                 return true;
3307         }
3308
3309         /**
3310          * Unlock specific tables
3311          *
3312          * @param string $method The caller
3313          * @return bool
3314          */
3315         public function unlockTables( $method ) {
3316                 return true;
3317         }
3318
3319         /**
3320          * Delete a table
3321          * @param string $tableName
3322          * @param string $fName
3323          * @return bool|ResultWrapper
3324          * @since 1.18
3325          */
3326         public function dropTable( $tableName, $fName = __METHOD__ ) {
3327                 if ( !$this->tableExists( $tableName, $fName ) ) {
3328                         return false;
3329                 }
3330                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
3331
3332                 return $this->query( $sql, $fName );
3333         }
3334
3335         public function getInfinity() {
3336                 return 'infinity';
3337         }
3338
3339         public function encodeExpiry( $expiry ) {
3340                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3341                         ? $this->getInfinity()
3342                         : $this->timestamp( $expiry );
3343         }
3344
3345         public function decodeExpiry( $expiry, $format = TS_MW ) {
3346                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
3347                         return 'infinity';
3348                 }
3349
3350                 return ConvertibleTimestamp::convert( $format, $expiry );
3351         }
3352
3353         public function setBigSelects( $value = true ) {
3354                 // no-op
3355         }
3356
3357         public function isReadOnly() {
3358                 return ( $this->getReadOnlyReason() !== false );
3359         }
3360
3361         /**
3362          * @return string|bool Reason this DB is read-only or false if it is not
3363          */
3364         protected function getReadOnlyReason() {
3365                 $reason = $this->getLBInfo( 'readOnlyReason' );
3366
3367                 return is_string( $reason ) ? $reason : false;
3368         }
3369
3370         public function setTableAliases( array $aliases ) {
3371                 $this->tableAliases = $aliases;
3372         }
3373
3374         /**
3375          * @return bool Whether a DB user is required to access the DB
3376          * @since 1.28
3377          */
3378         protected function requiresDatabaseUser() {
3379                 return true;
3380         }
3381
3382         /**
3383          * Get the underlying binding handle, mConn
3384          *
3385          * Makes sure that mConn is set (disconnects and ping() failure can unset it).
3386          * This catches broken callers than catch and ignore disconnection exceptions.
3387          * Unlike checking isOpen(), this is safe to call inside of open().
3388          *
3389          * @return resource|object
3390          * @throws DBUnexpectedError
3391          * @since 1.26
3392          */
3393         protected function getBindingHandle() {
3394                 if ( !$this->mConn ) {
3395                         throw new DBUnexpectedError(
3396                                 $this,
3397                                 'DB connection was already closed or the connection dropped.'
3398                         );
3399                 }
3400
3401                 return $this->mConn;
3402         }
3403
3404         /**
3405          * @since 1.19
3406          * @return string
3407          */
3408         public function __toString() {
3409                 return (string)$this->mConn;
3410         }
3411
3412         /**
3413          * Make sure that copies do not share the same client binding handle
3414          * @throws DBConnectionError
3415          */
3416         public function __clone() {
3417                 $this->connLogger->warning(
3418                         "Cloning " . get_class( $this ) . " is not recomended; forking connection:\n" .
3419                         ( new RuntimeException() )->getTraceAsString()
3420                 );
3421
3422                 if ( $this->isOpen() ) {
3423                         // Open a new connection resource without messing with the old one
3424                         $this->mOpened = false;
3425                         $this->mConn = false;
3426                         $this->mTrxEndCallbacks = []; // don't copy
3427                         $this->handleSessionLoss(); // no trx or locks anymore
3428                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3429                         $this->lastPing = microtime( true );
3430                 }
3431         }
3432
3433         /**
3434          * Called by serialize. Throw an exception when DB connection is serialized.
3435          * This causes problems on some database engines because the connection is
3436          * not restored on unserialize.
3437          */
3438         public function __sleep() {
3439                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
3440                         'the connection is not restored on wakeup.' );
3441         }
3442
3443         /**
3444          * Run a few simple sanity checks and close dangling connections
3445          */
3446         public function __destruct() {
3447                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
3448                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
3449                 }
3450
3451                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
3452                 if ( $danglingWriters ) {
3453                         $fnames = implode( ', ', $danglingWriters );
3454                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
3455                 }
3456
3457                 if ( $this->mConn ) {
3458                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
3459                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
3460                         \MediaWiki\suppressWarnings();
3461                         $this->closeConnection();
3462                         \MediaWiki\restoreWarnings();
3463                         $this->mConn = false;
3464                         $this->mOpened = false;
3465                 }
3466         }
3467 }
3468
3469 class_alias( 'Database', 'DatabaseBase' );