includes/db/Database.php

   1 <?php
   2
   3 /**
   4  * @defgroup Database Database
   5  *
   6  * This file deals with database interface functions
   7  * and query specifics/optimisations.
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write to the Free Software Foundation, Inc.,
  21  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  22  * http://www.gnu.org/copyleft/gpl.html
  23  *
  24  * @file
  25  * @ingroup Database
  26  */
  27
  28 /**
  29  * Interface for classes that implement or wrap DatabaseBase
  30  * @ingroup Database
  31  */
  32 interface IDatabase {
  33 }
  34
  35 /**
  36  * Database abstraction object
  37  * @ingroup Database
  38  */
  39 abstract class DatabaseBase implements IDatabase {
  40         /** Number of times to re-try an operation in case of deadlock */
  41         const DEADLOCK_TRIES = 4;
  42
  43         /** Minimum time to wait before retry, in microseconds */
  44         const DEADLOCK_DELAY_MIN = 500000;
  45
  46         /** Maximum time to wait before retry */
  47         const DEADLOCK_DELAY_MAX = 1500000;
  48
  49 # ------------------------------------------------------------------------------
  50 # Variables
  51 # ------------------------------------------------------------------------------
  52
  53         protected $mLastQuery = '';
  54         protected $mDoneWrites = false;
  55         protected $mPHPError = false;
  56
  57         protected $mServer, $mUser, $mPassword, $mDBname;
  58
  59         /** @var resource Database connection */
  60         protected $mConn = null;
  61         protected $mOpened = false;
  62
  63         /** @var callable[] */
  64         protected $mTrxIdleCallbacks = array();
  65         /** @var callable[] */
  66         protected $mTrxPreCommitCallbacks = array();
  67
  68         protected $mTablePrefix;
  69         protected $mSchema;
  70         protected $mFlags;
  71         protected $mForeign;
  72         protected $mErrorCount = 0;
  73         protected $mLBInfo = array();
  74         protected $mDefaultBigSelects = null;
  75         protected $mSchemaVars = false;
  76
  77         protected $preparedArgs;
  78
  79         protected $htmlErrors;
  80
  81         protected $delimiter = ';';
  82
  83         /**
  84          * Either 1 if a transaction is active or 0 otherwise.
  85          * The other Trx fields may not be meaningfull if this is 0.
  86          *
  87          * @var int
  88          */
  89         protected $mTrxLevel = 0;
  90
  91         /**
  92          * Either a short hexidecimal string if a transaction is active or ""
  93          *
  94          * @var string
  95          * @see DatabaseBase::mTrxLevel
  96          */
  97         protected $mTrxShortId = '';
  98
  99         /**
 100          * The UNIX time that the transaction started. Callers can assume that if
 101          * snapshot isolation is used, then the data is *at least* up to date to that
 102          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 103          *
 104          * @var float|null
 105          * @see DatabaseBase::mTrxLevel
 106          */
 107         private $mTrxTimestamp = null;
 108
 109         /**
 110          * Remembers the function name given for starting the most recent transaction via begin().
 111          * Used to provide additional context for error reporting.
 112          *
 113          * @var string
 114          * @see DatabaseBase::mTrxLevel
 115          */
 116         private $mTrxFname = null;
 117
 118         /**
 119          * Record if possible write queries were done in the last transaction started
 120          *
 121          * @var bool
 122          * @see DatabaseBase::mTrxLevel
 123          */
 124         private $mTrxDoneWrites = false;
 125
 126         /**
 127          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 128          *
 129          * @var bool
 130          * @see DatabaseBase::mTrxLevel
 131          */
 132         private $mTrxAutomatic = false;
 133
 134         /**
 135          * Array of levels of atomicity within transactions
 136          *
 137          * @var SplStack
 138          */
 139         private $mTrxAtomicLevels;
 140
 141         /**
 142          * Record if the current transaction was started implicitly by DatabaseBase::startAtomic
 143          *
 144          * @var bool
 145          */
 146         private $mTrxAutomaticAtomic = false;
 147
 148         /**
 149          * @since 1.21
 150          * @var resource File handle for upgrade
 151          */
 152         protected $fileHandle = null;
 153
 154         /**
 155          * @since 1.22
 156          * @var string[] Process cache of VIEWs names in the database
 157          */
 158         protected $allViews = null;
 159
 160 # ------------------------------------------------------------------------------
 161 # Accessors
 162 # ------------------------------------------------------------------------------
 163         # These optionally set a variable and return the previous state
 164
 165         /**
 166          * A string describing the current software version, and possibly
 167          * other details in a user-friendly way. Will be listed on Special:Version, etc.
 168          * Use getServerVersion() to get machine-friendly information.
 169          *
 170          * @return string Version information from the database server
 171          */
 172         public function getServerInfo() {
 173                 return $this->getServerVersion();
 174         }
 175
 176         /**
 177          * @return string Command delimiter used by this database engine
 178          */
 179         public function getDelimiter() {
 180                 return $this->delimiter;
 181         }
 182
 183         /**
 184          * Boolean, controls output of large amounts of debug information.
 185          * @param bool|null $debug
 186          *   - true to enable debugging
 187          *   - false to disable debugging
 188          *   - omitted or null to do nothing
 189          *
 190          * @return bool|null Previous value of the flag
 191          */
 192         public function debug( $debug = null ) {
 193                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 194         }
 195
 196         /**
 197          * Turns buffering of SQL result sets on (true) or off (false). Default is
 198          * "on".
 199          *
 200          * Unbuffered queries are very troublesome in MySQL:
 201          *
 202          *   - If another query is executed while the first query is being read
 203          *     out, the first query is killed. This means you can't call normal
 204          *     MediaWiki functions while you are reading an unbuffered query result
 205          *     from a normal wfGetDB() connection.
 206          *
 207          *   - Unbuffered queries cause the MySQL server to use large amounts of
 208          *     memory and to hold broad locks which block other queries.
 209          *
 210          * If you want to limit client-side memory, it's almost always better to
 211          * split up queries into batches using a LIMIT clause than to switch off
 212          * buffering.
 213          *
 214          * @param null|bool $buffer
 215          * @return null|bool The previous value of the flag
 216          */
 217         public function bufferResults( $buffer = null ) {
 218                 if ( is_null( $buffer ) ) {
 219                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 220                 } else {
 221                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 222                 }
 223         }
 224
 225         /**
 226          * Turns on (false) or off (true) the automatic generation and sending
 227          * of a "we're sorry, but there has been a database error" page on
 228          * database errors. Default is on (false). When turned off, the
 229          * code should use lastErrno() and lastError() to handle the
 230          * situation as appropriate.
 231          *
 232          * Do not use this function outside of the Database classes.
 233          *
 234          * @param null|bool $ignoreErrors
 235          * @return bool The previous value of the flag.
 236          */
 237         public function ignoreErrors( $ignoreErrors = null ) {
 238                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 239         }
 240
 241         /**
 242          * Gets the current transaction level.
 243          *
 244          * Historically, transactions were allowed to be "nested". This is no
 245          * longer supported, so this function really only returns a boolean.
 246          *
 247          * @return int The previous value
 248          */
 249         public function trxLevel() {
 250                 return $this->mTrxLevel;
 251         }
 252
 253         /**
 254          * Get the UNIX timestamp of the time that the transaction was established
 255          *
 256          * This can be used to reason about the staleness of SELECT data
 257          * in REPEATABLE-READ transaction isolation level.
 258          *
 259          * @return float|null Returns null if there is not active transaction
 260          * @since 1.25
 261          */
 262         public function trxTimestamp() {
 263                 return $this->mTrxLevel ? $this->mTrxTimestamp : null;
 264         }
 265
 266         /**
 267          * Get/set the number of errors logged. Only useful when errors are ignored
 268          * @param int $count The count to set, or omitted to leave it unchanged.
 269          * @return int The error count
 270          */
 271         public function errorCount( $count = null ) {
 272                 return wfSetVar( $this->mErrorCount, $count );
 273         }
 274
 275         /**
 276          * Get/set the table prefix.
 277          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 278          * @return string The previous table prefix.
 279          */
 280         public function tablePrefix( $prefix = null ) {
 281                 return wfSetVar( $this->mTablePrefix, $prefix );
 282         }
 283
 284         /**
 285          * Get/set the db schema.
 286          * @param string $schema The database schema to set, or omitted to leave it unchanged.
 287          * @return string The previous db schema.
 288          */
 289         public function dbSchema( $schema = null ) {
 290                 return wfSetVar( $this->mSchema, $schema );
 291         }
 292
 293         /**
 294          * Set the filehandle to copy write statements to.
 295          *
 296          * @param resource $fh File handle
 297          */
 298         public function setFileHandle( $fh ) {
 299                 $this->fileHandle = $fh;
 300         }
 301
 302         /**
 303          * Get properties passed down from the server info array of the load
 304          * balancer.
 305          *
 306          * @param string $name The entry of the info array to get, or null to get the
 307          *   whole array
 308          *
 309          * @return array|mixed|null
 310          */
 311         public function getLBInfo( $name = null ) {
 312                 if ( is_null( $name ) ) {
 313                         return $this->mLBInfo;
 314                 } else {
 315                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 316                                 return $this->mLBInfo[$name];
 317                         } else {
 318                                 return null;
 319                         }
 320                 }
 321         }
 322
 323         /**
 324          * Set the LB info array, or a member of it. If called with one parameter,
 325          * the LB info array is set to that parameter. If it is called with two
 326          * parameters, the member with the given name is set to the given value.
 327          *
 328          * @param string $name
 329          * @param array $value
 330          */
 331         public function setLBInfo( $name, $value = null ) {
 332                 if ( is_null( $value ) ) {
 333                         $this->mLBInfo = $name;
 334                 } else {
 335                         $this->mLBInfo[$name] = $value;
 336                 }
 337         }
 338
 339         /**
 340          * Set lag time in seconds for a fake slave
 341          *
 342          * @param mixed $lag Valid values for this parameter are determined by the
 343          *   subclass, but should be a PHP scalar or array that would be sensible
 344          *   as part of $wgLBFactoryConf.
 345          */
 346         public function setFakeSlaveLag( $lag ) {
 347         }
 348
 349         /**
 350          * Make this connection a fake master
 351          *
 352          * @param bool $enabled
 353          */
 354         public function setFakeMaster( $enabled = true ) {
 355         }
 356
 357         /**
 358          * Returns true if this database supports (and uses) cascading deletes
 359          *
 360          * @return bool
 361          */
 362         public function cascadingDeletes() {
 363                 return false;
 364         }
 365
 366         /**
 367          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 368          *
 369          * @return bool
 370          */
 371         public function cleanupTriggers() {
 372                 return false;
 373         }
 374
 375         /**
 376          * Returns true if this database is strict about what can be put into an IP field.
 377          * Specifically, it uses a NULL value instead of an empty string.
 378          *
 379          * @return bool
 380          */
 381         public function strictIPs() {
 382                 return false;
 383         }
 384
 385         /**
 386          * Returns true if this database uses timestamps rather than integers
 387          *
 388          * @return bool
 389          */
 390         public function realTimestamps() {
 391                 return false;
 392         }
 393
 394         /**
 395          * Returns true if this database does an implicit sort when doing GROUP BY
 396          *
 397          * @return bool
 398          */
 399         public function implicitGroupby() {
 400                 return true;
 401         }
 402
 403         /**
 404          * Returns true if this database does an implicit order by when the column has an index
 405          * For example: SELECT page_title FROM page LIMIT 1
 406          *
 407          * @return bool
 408          */
 409         public function implicitOrderby() {
 410                 return true;
 411         }
 412
 413         /**
 414          * Returns true if this database can do a native search on IP columns
 415          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 416          *
 417          * @return bool
 418          */
 419         public function searchableIPs() {
 420                 return false;
 421         }
 422
 423         /**
 424          * Returns true if this database can use functional indexes
 425          *
 426          * @return bool
 427          */
 428         public function functionalIndexes() {
 429                 return false;
 430         }
 431
 432         /**
 433          * Return the last query that went through DatabaseBase::query()
 434          * @return string
 435          */
 436         public function lastQuery() {
 437                 return $this->mLastQuery;
 438         }
 439
 440         /**
 441          * Returns true if the connection may have been used for write queries.
 442          * Should return true if unsure.
 443          *
 444          * @return bool
 445          */
 446         public function doneWrites() {
 447                 return (bool)$this->mDoneWrites;
 448         }
 449
 450         /**
 451          * Returns the last time the connection may have been used for write queries.
 452          * Should return a timestamp if unsure.
 453          *
 454          * @return int|float UNIX timestamp or false
 455          * @since 1.24
 456          */
 457         public function lastDoneWrites() {
 458                 return $this->mDoneWrites ?: false;
 459         }
 460
 461         /**
 462          * Returns true if there is a transaction open with possible write
 463          * queries or transaction pre-commit/idle callbacks waiting on it to finish.
 464          *
 465          * @return bool
 466          */
 467         public function writesOrCallbacksPending() {
 468                 return $this->mTrxLevel && (
 469                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 470                 );
 471         }
 472
 473         /**
 474          * Is a connection to the database open?
 475          * @return bool
 476          */
 477         public function isOpen() {
 478                 return $this->mOpened;
 479         }
 480
 481         /**
 482          * Set a flag for this connection
 483          *
 484          * @param int $flag DBO_* constants from Defines.php:
 485          *   - DBO_DEBUG: output some debug info (same as debug())
 486          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 487          *   - DBO_TRX: automatically start transactions
 488          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 489          *       and removes it in command line mode
 490          *   - DBO_PERSISTENT: use persistant database connection
 491          */
 492         public function setFlag( $flag ) {
 493                 global $wgDebugDBTransactions;
 494                 $this->mFlags |= $flag;
 495                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 496                         wfDebug( "Implicit transactions are now enabled.\n" );
 497                 }
 498         }
 499
 500         /**
 501          * Clear a flag for this connection
 502          *
 503          * @param int $flag DBO_* constants from Defines.php:
 504          *   - DBO_DEBUG: output some debug info (same as debug())
 505          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 506          *   - DBO_TRX: automatically start transactions
 507          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 508          *       and removes it in command line mode
 509          *   - DBO_PERSISTENT: use persistant database connection
 510          */
 511         public function clearFlag( $flag ) {
 512                 global $wgDebugDBTransactions;
 513                 $this->mFlags &= ~$flag;
 514                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 515                         wfDebug( "Implicit transactions are now disabled.\n" );
 516                 }
 517         }
 518
 519         /**
 520          * Returns a boolean whether the flag $flag is set for this connection
 521          *
 522          * @param int $flag DBO_* constants from Defines.php:
 523          *   - DBO_DEBUG: output some debug info (same as debug())
 524          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 525          *   - DBO_TRX: automatically start transactions
 526          *   - DBO_PERSISTENT: use persistant database connection
 527          * @return bool
 528          */
 529         public function getFlag( $flag ) {
 530                 return !!( $this->mFlags & $flag );
 531         }
 532
 533         /**
 534          * General read-only accessor
 535          *
 536          * @param string $name
 537          * @return string
 538          */
 539         public function getProperty( $name ) {
 540                 return $this->$name;
 541         }
 542
 543         /**
 544          * @return string
 545          */
 546         public function getWikiID() {
 547                 if ( $this->mTablePrefix ) {
 548                         return "{$this->mDBname}-{$this->mTablePrefix}";
 549                 } else {
 550                         return $this->mDBname;
 551                 }
 552         }
 553
 554         /**
 555          * Return a path to the DBMS-specific SQL file if it exists,
 556          * otherwise default SQL file
 557          *
 558          * @param string $filename
 559          * @return string
 560          */
 561         private function getSqlFilePath( $filename ) {
 562                 global $IP;
 563                 $dbmsSpecificFilePath = "$IP/maintenance/" . $this->getType() . "/$filename";
 564                 if ( file_exists( $dbmsSpecificFilePath ) ) {
 565                         return $dbmsSpecificFilePath;
 566                 } else {
 567                         return "$IP/maintenance/$filename";
 568                 }
 569         }
 570
 571         /**
 572          * Return a path to the DBMS-specific schema file,
 573          * otherwise default to tables.sql
 574          *
 575          * @return string
 576          */
 577         public function getSchemaPath() {
 578                 return $this->getSqlFilePath( 'tables.sql' );
 579         }
 580
 581         /**
 582          * Return a path to the DBMS-specific update key file,
 583          * otherwise default to update-keys.sql
 584          *
 585          * @return string
 586          */
 587         public function getUpdateKeysPath() {
 588                 return $this->getSqlFilePath( 'update-keys.sql' );
 589         }
 590
 591 # ------------------------------------------------------------------------------
 592 # Other functions
 593 # ------------------------------------------------------------------------------
 594
 595         /**
 596          * Constructor.
 597          *
 598          * FIXME: It is possible to construct a Database object with no associated
 599          * connection object, by specifying no parameters to __construct(). This
 600          * feature is deprecated and should be removed.
 601          *
 602          * DatabaseBase subclasses should not be constructed directly in external
 603          * code. DatabaseBase::factory() should be used instead.
 604          *
 605          * @param array $params Parameters passed from DatabaseBase::factory()
 606          */
 607         function __construct( $params = null ) {
 608                 global $wgDBprefix, $wgDBmwschema, $wgCommandLineMode, $wgDebugDBTransactions;
 609
 610                 $this->mTrxAtomicLevels = new SplStack;
 611
 612                 if ( is_array( $params ) ) { // MW 1.22
 613                         $server = $params['host'];
 614                         $user = $params['user'];
 615                         $password = $params['password'];
 616                         $dbName = $params['dbname'];
 617                         $flags = $params['flags'];
 618                         $tablePrefix = $params['tablePrefix'];
 619                         $schema = $params['schema'];
 620                         $foreign = $params['foreign'];
 621                 } else { // legacy calling pattern
 622                         wfDeprecated( __METHOD__ . " method called without parameter array.", "1.23" );
 623                         $args = func_get_args();
 624                         $server = isset( $args[0] ) ? $args[0] : false;
 625                         $user = isset( $args[1] ) ? $args[1] : false;
 626                         $password = isset( $args[2] ) ? $args[2] : false;
 627                         $dbName = isset( $args[3] ) ? $args[3] : false;
 628                         $flags = isset( $args[4] ) ? $args[4] : 0;
 629                         $tablePrefix = isset( $args[5] ) ? $args[5] : 'get from global';
 630                         $schema = 'get from global';
 631                         $foreign = isset( $args[6] ) ? $args[6] : false;
 632                 }
 633
 634                 $this->mFlags = $flags;
 635                 if ( $this->mFlags & DBO_DEFAULT ) {
 636                         if ( $wgCommandLineMode ) {
 637                                 $this->mFlags &= ~DBO_TRX;
 638                                 if ( $wgDebugDBTransactions ) {
 639                                         wfDebug( "Implicit transaction open disabled.\n" );
 640                                 }
 641                         } else {
 642                                 $this->mFlags |= DBO_TRX;
 643                                 if ( $wgDebugDBTransactions ) {
 644                                         wfDebug( "Implicit transaction open enabled.\n" );
 645                                 }
 646                         }
 647                 }
 648
 649                 /** Get the default table prefix*/
 650                 if ( $tablePrefix == 'get from global' ) {
 651                         $this->mTablePrefix = $wgDBprefix;
 652                 } else {
 653                         $this->mTablePrefix = $tablePrefix;
 654                 }
 655
 656                 /** Get the database schema*/
 657                 if ( $schema == 'get from global' ) {
 658                         $this->mSchema = $wgDBmwschema;
 659                 } else {
 660                         $this->mSchema = $schema;
 661                 }
 662
 663                 $this->mForeign = $foreign;
 664
 665                 if ( $user ) {
 666                         $this->open( $server, $user, $password, $dbName );
 667                 }
 668         }
 669
 670         /**
 671          * Called by serialize. Throw an exception when DB connection is serialized.
 672          * This causes problems on some database engines because the connection is
 673          * not restored on unserialize.
 674          */
 675         public function __sleep() {
 676                 throw new MWException( 'Database serialization may cause problems, since ' .
 677                         'the connection is not restored on wakeup.' );
 678         }
 679
 680         /**
 681          * Given a DB type, construct the name of the appropriate child class of
 682          * DatabaseBase. This is designed to replace all of the manual stuff like:
 683          *    $class = 'Database' . ucfirst( strtolower( $dbType ) );
 684          * as well as validate against the canonical list of DB types we have
 685          *
 686          * This factory function is mostly useful for when you need to connect to a
 687          * database other than the MediaWiki default (such as for external auth,
 688          * an extension, et cetera). Do not use this to connect to the MediaWiki
 689          * database. Example uses in core:
 690          * @see LoadBalancer::reallyOpenConnection()
 691          * @see ForeignDBRepo::getMasterDB()
 692          * @see WebInstallerDBConnect::execute()
 693          *
 694          * @since 1.18
 695          *
 696          * @param string $dbType A possible DB type
 697          * @param array $p An array of options to pass to the constructor.
 698          *    Valid options are: host, user, password, dbname, flags, tablePrefix, schema, driver
 699          * @throws MWException If the database driver or extension cannot be found
 700          * @return DatabaseBase|null DatabaseBase subclass or null
 701          */
 702         final public static function factory( $dbType, $p = array() ) {
 703                 $canonicalDBTypes = array(
 704                         'mysql' => array( 'mysqli', 'mysql' ),
 705                         'postgres' => array(),
 706                         'sqlite' => array(),
 707                         'oracle' => array(),
 708                         'mssql' => array(),
 709                 );
 710
 711                 $driver = false;
 712                 $dbType = strtolower( $dbType );
 713                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 714                         $possibleDrivers = $canonicalDBTypes[$dbType];
 715                         if ( !empty( $p['driver'] ) ) {
 716                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 717                                         $driver = $p['driver'];
 718                                 } else {
 719                                         throw new MWException( __METHOD__ .
 720                                                 " cannot construct Database with type '$dbType' and driver '{$p['driver']}'" );
 721                                 }
 722                         } else {
 723                                 foreach ( $possibleDrivers as $posDriver ) {
 724                                         if ( extension_loaded( $posDriver ) ) {
 725                                                 $driver = $posDriver;
 726                                                 break;
 727                                         }
 728                                 }
 729                         }
 730                 } else {
 731                         $driver = $dbType;
 732                 }
 733                 if ( $driver === false ) {
 734                         throw new MWException( __METHOD__ .
 735                                 " no viable database extension found for type '$dbType'" );
 736                 }
 737
 738                 // Determine schema defaults. Currently Microsoft SQL Server uses $wgDBmwschema,
 739                 // and everything else doesn't use a schema (e.g. null)
 740                 // Although postgres and oracle support schemas, we don't use them (yet)
 741                 // to maintain backwards compatibility
 742                 $defaultSchemas = array(
 743                         'mysql' => null,
 744                         'postgres' => null,
 745                         'sqlite' => null,
 746                         'oracle' => null,
 747                         'mssql' => 'get from global',
 748                 );
 749
 750                 $class = 'Database' . ucfirst( $driver );
 751                 if ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 752                         $params = array(
 753                                 'host' => isset( $p['host'] ) ? $p['host'] : false,
 754                                 'user' => isset( $p['user'] ) ? $p['user'] : false,
 755                                 'password' => isset( $p['password'] ) ? $p['password'] : false,
 756                                 'dbname' => isset( $p['dbname'] ) ? $p['dbname'] : false,
 757                                 'flags' => isset( $p['flags'] ) ? $p['flags'] : 0,
 758                                 'tablePrefix' => isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global',
 759                                 'schema' => isset( $p['schema'] ) ? $p['schema'] : $defaultSchemas[$dbType],
 760                                 'foreign' => isset( $p['foreign'] ) ? $p['foreign'] : false
 761                         );
 762
 763                         return new $class( $params );
 764                 } else {
 765                         return null;
 766                 }
 767         }
 768
 769         protected function installErrorHandler() {
 770                 $this->mPHPError = false;
 771                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 772                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 773         }
 774
 775         /**
 776          * @return bool|string
 777          */
 778         protected function restoreErrorHandler() {
 779                 restore_error_handler();
 780                 if ( $this->htmlErrors !== false ) {
 781                         ini_set( 'html_errors', $this->htmlErrors );
 782                 }
 783                 if ( $this->mPHPError ) {
 784                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 785                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 786
 787                         return $error;
 788                 } else {
 789                         return false;
 790                 }
 791         }
 792
 793         /**
 794          * @param int $errno
 795          * @param string $errstr
 796          */
 797         public function connectionErrorHandler( $errno, $errstr ) {
 798                 $this->mPHPError = $errstr;
 799         }
 800
 801         /**
 802          * Closes a database connection.
 803          * if it is open : commits any open transactions
 804          *
 805          * @throws MWException
 806          * @return bool Operation success. true if already closed.
 807          */
 808         public function close() {
 809                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 810                         throw new MWException( "Transaction idle callbacks still pending." );
 811                 }
 812                 if ( $this->mConn ) {
 813                         if ( $this->trxLevel() ) {
 814                                 if ( !$this->mTrxAutomatic ) {
 815                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 816                                                 " performing implicit commit before closing connection!" );
 817                                 }
 818
 819                                 $this->commit( __METHOD__, 'flush' );
 820                         }
 821
 822                         $closed = $this->closeConnection();
 823                         $this->mConn = false;
 824                 } else {
 825                         $closed = true;
 826                 }
 827                 $this->mOpened = false;
 828
 829                 return $closed;
 830         }
 831
 832         /**
 833          * Closes underlying database connection
 834          * @since 1.20
 835          * @return bool Whether connection was closed successfully
 836          */
 837         abstract protected function closeConnection();
 838
 839         /**
 840          * @param string $error Fallback error message, used if none is given by DB
 841          * @throws DBConnectionError
 842          */
 843         function reportConnectionError( $error = 'Unknown error' ) {
 844                 $myError = $this->lastError();
 845                 if ( $myError ) {
 846                         $error = $myError;
 847                 }
 848
 849                 # New method
 850                 throw new DBConnectionError( $this, $error );
 851         }
 852
 853         /**
 854          * The DBMS-dependent part of query()
 855          *
 856          * @param string $sql SQL query.
 857          * @return ResultWrapper|bool Result object to feed to fetchObject,
 858          *   fetchRow, ...; or false on failure
 859          */
 860         abstract protected function doQuery( $sql );
 861
 862         /**
 863          * Determine whether a query writes to the DB.
 864          * Should return true if unsure.
 865          *
 866          * @param string $sql
 867          * @return bool
 868          */
 869         public function isWriteQuery( $sql ) {
 870                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 871         }
 872
 873         /**
 874          * Run an SQL query and return the result. Normally throws a DBQueryError
 875          * on failure. If errors are ignored, returns false instead.
 876          *
 877          * In new code, the query wrappers select(), insert(), update(), delete(),
 878          * etc. should be used where possible, since they give much better DBMS
 879          * independence and automatically quote or validate user input in a variety
 880          * of contexts. This function is generally only useful for queries which are
 881          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 882          * as CREATE TABLE.
 883          *
 884          * However, the query wrappers themselves should call this function.
 885          *
 886          * @param string $sql SQL query
 887          * @param string $fname Name of the calling function, for profiling/SHOW PROCESSLIST
 888          *     comment (you can use __METHOD__ or add some extra info)
 889          * @param bool $tempIgnore Whether to avoid throwing an exception on errors...
 890          *     maybe best to catch the exception instead?
 891          * @throws MWException
 892          * @return bool|ResultWrapper True for a successful write query, ResultWrapper object
 893          *     for a successful read query, or false on failure if $tempIgnore set
 894          */
 895         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 896                 global $wgUser, $wgDebugDBTransactions, $wgDebugDumpSqlLength;
 897
 898                 $this->mLastQuery = $sql;
 899                 if ( $this->isWriteQuery( $sql ) ) {
 900                         # Set a flag indicating that writes have been done
 901                         wfDebug( __METHOD__ . ': Writes done: ' . DatabaseBase::generalizeSQL( $sql ) . "\n" );
 902                         $this->mDoneWrites = microtime( true );
 903                 }
 904
 905                 # Add a comment for easy SHOW PROCESSLIST interpretation
 906                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 907                         $userName = $wgUser->getName();
 908                         if ( mb_strlen( $userName ) > 15 ) {
 909                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 910                         }
 911                         $userName = str_replace( '/', '', $userName );
 912                 } else {
 913                         $userName = '';
 914                 }
 915
 916                 // Add trace comment to the begin of the sql string, right after the operator.
 917                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 918                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 919
 920                 # If DBO_TRX is set, start a transaction
 921                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 922                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK'
 923                 ) {
 924                         # Avoid establishing transactions for SHOW and SET statements too -
 925                         # that would delay transaction initializations to once connection
 926                         # is really used by application
 927                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 928                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 929                                 if ( $wgDebugDBTransactions ) {
 930                                         wfDebug( "Implicit transaction start.\n" );
 931                                 }
 932                                 $this->begin( __METHOD__ . " ($fname)" );
 933                                 $this->mTrxAutomatic = true;
 934                         }
 935                 }
 936
 937                 # Keep track of whether the transaction has write queries pending
 938                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
 939                         $this->mTrxDoneWrites = true;
 940                         Profiler::instance()->getTransactionProfiler()->transactionWritingIn(
 941                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
 942                 }
 943
 944                 $queryProf = '';
 945                 $totalProf = '';
 946                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 947
 948                 if ( !Profiler::instance()->isStub() ) {
 949                         # generalizeSQL will probably cut down the query to reasonable
 950                         # logging size most of the time. The substr is really just a sanity check.
 951                         if ( $isMaster ) {
 952                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 953                                 $totalProf = 'DatabaseBase::query-master';
 954                         } else {
 955                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 956                                 $totalProf = 'DatabaseBase::query';
 957                         }
 958                         # Include query transaction state
 959                         $queryProf .= $this->mTrxShortId ? " [TRX#{$this->mTrxShortId}]" : "";
 960
 961                         $trx = $this->mTrxLevel ? 'TRX=yes' : 'TRX=no';
 962                         wfProfileIn( $totalProf );
 963                         wfProfileIn( $queryProf );
 964                 }
 965
 966                 if ( $this->debug() ) {
 967                         static $cnt = 0;
 968
 969                         $cnt++;
 970                         $sqlx = $wgDebugDumpSqlLength ? substr( $commentedSql, 0, $wgDebugDumpSqlLength )
 971                                 : $commentedSql;
 972                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 973
 974                         $master = $isMaster ? 'master' : 'slave';
 975                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 976                 }
 977
 978                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 979
 980                 # Avoid fatals if close() was called
 981                 if ( !$this->isOpen() ) {
 982                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
 983                 }
 984
 985                 # Log the query time and feed it into the DB trx profiler
 986                 $queryStartTime = microtime( true );
 987                 $queryProfile = new ScopedCallback( function() use ( $queryStartTime, $queryProf ) {
 988                         $elapsed = microtime( true ) - $queryStartTime;
 989                         $trxProfiler = Profiler::instance()->getTransactionProfiler();
 990                         $trxProfiler->recordFunctionCompletion( $queryProf, $elapsed );
 991                 } );
 992
 993                 # Do the query and handle errors
 994                 $ret = $this->doQuery( $commentedSql );
 995
 996                 MWDebug::queryTime( $queryId );
 997
 998                 # Try reconnecting if the connection was lost
 999                 if ( false === $ret && $this->wasErrorReissuable() ) {
1000                         # Transaction is gone, like it or not
1001                         $hadTrx = $this->mTrxLevel; // possible lost transaction
1002                         $this->mTrxLevel = 0;
1003                         $this->mTrxIdleCallbacks = array(); // bug 65263
1004                         $this->mTrxPreCommitCallbacks = array(); // bug 65263
1005                         wfDebug( "Connection lost, reconnecting...\n" );
1006                         # Stash the last error values since ping() might clear them
1007                         $lastError = $this->lastError();
1008                         $lastErrno = $this->lastErrno();
1009                         if ( $this->ping() ) {
1010                                 global $wgRequestTime;
1011                                 wfDebug( "Reconnected\n" );
1012                                 $sqlx = $wgDebugDumpSqlLength ? substr( $commentedSql, 0, $wgDebugDumpSqlLength )
1013                                         : $commentedSql;
1014                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
1015                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
1016                                 if ( $elapsed < 300 ) {
1017                                         # Not a database error to lose a transaction after a minute or two
1018                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx" );
1019                                 }
1020                                 if ( $hadTrx ) {
1021                                         # Leave $ret as false and let an error be reported.
1022                                         # Callers may catch the exception and continue to use the DB.
1023                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname, $tempIgnore );
1024                                 } else {
1025                                         # Should be safe to silently retry (no trx and thus no callbacks)
1026                                         $ret = $this->doQuery( $commentedSql );
1027                                 }
1028                         } else {
1029                                 wfDebug( "Failed\n" );
1030                         }
1031                 }
1032
1033                 if ( false === $ret ) {
1034                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1035                 }
1036
1037                 if ( !Profiler::instance()->isStub() ) {
1038                         wfProfileOut( $queryProf );
1039                         wfProfileOut( $totalProf );
1040                 }
1041
1042                 return $this->resultObject( $ret );
1043         }
1044
1045         /**
1046          * Report a query error. Log the error, and if neither the object ignore
1047          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1048          *
1049          * @param string $error
1050          * @param int $errno
1051          * @param string $sql
1052          * @param string $fname
1053          * @param bool $tempIgnore
1054          * @throws DBQueryError
1055          */
1056         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1057                 # Ignore errors during error handling to avoid infinite recursion
1058                 $ignore = $this->ignoreErrors( true );
1059                 ++$this->mErrorCount;
1060
1061                 if ( $ignore || $tempIgnore ) {
1062                         wfDebug( "SQL ERROR (ignored): $error\n" );
1063                         $this->ignoreErrors( $ignore );
1064                 } else {
1065                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1066                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line" );
1067                         wfDebug( "SQL ERROR: " . $error . "\n" );
1068                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1069                 }
1070         }
1071
1072         /**
1073          * Intended to be compatible with the PEAR::DB wrapper functions.
1074          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1075          *
1076          * ? = scalar value, quoted as necessary
1077          * ! = raw SQL bit (a function for instance)
1078          * & = filename; reads the file and inserts as a blob
1079          *     (we don't use this though...)
1080          *
1081          * @param string $sql
1082          * @param string $func
1083          *
1084          * @return array
1085          */
1086         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1087                 /* MySQL doesn't support prepared statements (yet), so just
1088                  * pack up the query for reference. We'll manually replace
1089                  * the bits later.
1090                  */
1091                 return array( 'query' => $sql, 'func' => $func );
1092         }
1093
1094         /**
1095          * Free a prepared query, generated by prepare().
1096          * @param string $prepared
1097          */
1098         protected function freePrepared( $prepared ) {
1099                 /* No-op by default */
1100         }
1101
1102         /**
1103          * Execute a prepared query with the various arguments
1104          * @param string $prepared The prepared sql
1105          * @param mixed $args Either an array here, or put scalars as varargs
1106          *
1107          * @return ResultWrapper
1108          */
1109         public function execute( $prepared, $args = null ) {
1110                 if ( !is_array( $args ) ) {
1111                         # Pull the var args
1112                         $args = func_get_args();
1113                         array_shift( $args );
1114                 }
1115
1116                 $sql = $this->fillPrepared( $prepared['query'], $args );
1117
1118                 return $this->query( $sql, $prepared['func'] );
1119         }
1120
1121         /**
1122          * For faking prepared SQL statements on DBs that don't support it directly.
1123          *
1124          * @param string $preparedQuery A 'preparable' SQL statement
1125          * @param array $args Array of Arguments to fill it with
1126          * @return string Executable SQL
1127          */
1128         public function fillPrepared( $preparedQuery, $args ) {
1129                 reset( $args );
1130                 $this->preparedArgs =& $args;
1131
1132                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1133                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1134         }
1135
1136         /**
1137          * preg_callback func for fillPrepared()
1138          * The arguments should be in $this->preparedArgs and must not be touched
1139          * while we're doing this.
1140          *
1141          * @param array $matches
1142          * @throws DBUnexpectedError
1143          * @return string
1144          */
1145         protected function fillPreparedArg( $matches ) {
1146                 switch ( $matches[1] ) {
1147                         case '\\?':
1148                                 return '?';
1149                         case '\\!':
1150                                 return '!';
1151                         case '\\&':
1152                                 return '&';
1153                 }
1154
1155                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1156
1157                 switch ( $matches[1] ) {
1158                         case '?':
1159                                 return $this->addQuotes( $arg );
1160                         case '!':
1161                                 return $arg;
1162                         case '&':
1163                                 # return $this->addQuotes( file_get_contents( $arg ) );
1164                                 throw new DBUnexpectedError(
1165                                         $this,
1166                                         '& mode is not implemented. If it\'s really needed, uncomment the line above.'
1167                                 );
1168                         default:
1169                                 throw new DBUnexpectedError(
1170                                         $this,
1171                                         'Received invalid match. This should never happen!'
1172                                 );
1173                 }
1174         }
1175
1176         /**
1177          * Free a result object returned by query() or select(). It's usually not
1178          * necessary to call this, just use unset() or let the variable holding
1179          * the result object go out of scope.
1180          *
1181          * @param mixed $res A SQL result
1182          */
1183         public function freeResult( $res ) {
1184         }
1185
1186         /**
1187          * A SELECT wrapper which returns a single field from a single result row.
1188          *
1189          * Usually throws a DBQueryError on failure. If errors are explicitly
1190          * ignored, returns false on failure.
1191          *
1192          * If no result rows are returned from the query, false is returned.
1193          *
1194          * @param string|array $table Table name. See DatabaseBase::select() for details.
1195          * @param string $var The field name to select. This must be a valid SQL
1196          *   fragment: do not use unvalidated user input.
1197          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1198          * @param string $fname The function name of the caller.
1199          * @param string|array $options The query options. See DatabaseBase::select() for details.
1200          *
1201          * @return bool|mixed The value from the field, or false on failure.
1202          */
1203         public function selectField( $table, $var, $cond = '', $fname = __METHOD__,
1204                 $options = array()
1205         ) {
1206                 if ( !is_array( $options ) ) {
1207                         $options = array( $options );
1208                 }
1209
1210                 $options['LIMIT'] = 1;
1211
1212                 $res = $this->select( $table, $var, $cond, $fname, $options );
1213
1214                 if ( $res === false || !$this->numRows( $res ) ) {
1215                         return false;
1216                 }
1217
1218                 $row = $this->fetchRow( $res );
1219
1220                 if ( $row !== false ) {
1221                         return reset( $row );
1222                 } else {
1223                         return false;
1224                 }
1225         }
1226
1227         /**
1228          * Returns an optional USE INDEX clause to go after the table, and a
1229          * string to go at the end of the query.
1230          *
1231          * @param array $options Associative array of options to be turned into
1232          *   an SQL query, valid keys are listed in the function.
1233          * @return array
1234          * @see DatabaseBase::select()
1235          */
1236         public function makeSelectOptions( $options ) {
1237                 $preLimitTail = $postLimitTail = '';
1238                 $startOpts = '';
1239
1240                 $noKeyOptions = array();
1241
1242                 foreach ( $options as $key => $option ) {
1243                         if ( is_numeric( $key ) ) {
1244                                 $noKeyOptions[$option] = true;
1245                         }
1246                 }
1247
1248                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1249
1250                 $preLimitTail .= $this->makeOrderBy( $options );
1251
1252                 // if (isset($options['LIMIT'])) {
1253                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1254                 //              isset($options['OFFSET']) ? $options['OFFSET']
1255                 //              : false);
1256                 // }
1257
1258                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1259                         $postLimitTail .= ' FOR UPDATE';
1260                 }
1261
1262                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1263                         $postLimitTail .= ' LOCK IN SHARE MODE';
1264                 }
1265
1266                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1267                         $startOpts .= 'DISTINCT';
1268                 }
1269
1270                 # Various MySQL extensions
1271                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1272                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1273                 }
1274
1275                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1276                         $startOpts .= ' HIGH_PRIORITY';
1277                 }
1278
1279                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1280                         $startOpts .= ' SQL_BIG_RESULT';
1281                 }
1282
1283                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1284                         $startOpts .= ' SQL_BUFFER_RESULT';
1285                 }
1286
1287                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1288                         $startOpts .= ' SQL_SMALL_RESULT';
1289                 }
1290
1291                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1292                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1293                 }
1294
1295                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1296                         $startOpts .= ' SQL_CACHE';
1297                 }
1298
1299                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1300                         $startOpts .= ' SQL_NO_CACHE';
1301                 }
1302
1303                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1304                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1305                 } else {
1306                         $useIndex = '';
1307                 }
1308
1309                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1310         }
1311
1312         /**
1313          * Returns an optional GROUP BY with an optional HAVING
1314          *
1315          * @param array $options Associative array of options
1316          * @return string
1317          * @see DatabaseBase::select()
1318          * @since 1.21
1319          */
1320         public function makeGroupByWithHaving( $options ) {
1321                 $sql = '';
1322                 if ( isset( $options['GROUP BY'] ) ) {
1323                         $gb = is_array( $options['GROUP BY'] )
1324                                 ? implode( ',', $options['GROUP BY'] )
1325                                 : $options['GROUP BY'];
1326                         $sql .= ' GROUP BY ' . $gb;
1327                 }
1328                 if ( isset( $options['HAVING'] ) ) {
1329                         $having = is_array( $options['HAVING'] )
1330                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1331                                 : $options['HAVING'];
1332                         $sql .= ' HAVING ' . $having;
1333                 }
1334
1335                 return $sql;
1336         }
1337
1338         /**
1339          * Returns an optional ORDER BY
1340          *
1341          * @param array $options Associative array of options
1342          * @return string
1343          * @see DatabaseBase::select()
1344          * @since 1.21
1345          */
1346         public function makeOrderBy( $options ) {
1347                 if ( isset( $options['ORDER BY'] ) ) {
1348                         $ob = is_array( $options['ORDER BY'] )
1349                                 ? implode( ',', $options['ORDER BY'] )
1350                                 : $options['ORDER BY'];
1351
1352                         return ' ORDER BY ' . $ob;
1353                 }
1354
1355                 return '';
1356         }
1357
1358         /**
1359          * Execute a SELECT query constructed using the various parameters provided.
1360          * See below for full details of the parameters.
1361          *
1362          * @param string|array $table Table name
1363          * @param string|array $vars Field names
1364          * @param string|array $conds Conditions
1365          * @param string $fname Caller function name
1366          * @param array $options Query options
1367          * @param array $join_conds Join conditions
1368          *
1369          *
1370          * @param string|array $table
1371          *
1372          * May be either an array of table names, or a single string holding a table
1373          * name. If an array is given, table aliases can be specified, for example:
1374          *
1375          *    array( 'a' => 'user' )
1376          *
1377          * This includes the user table in the query, with the alias "a" available
1378          * for use in field names (e.g. a.user_name).
1379          *
1380          * All of the table names given here are automatically run through
1381          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1382          * added, and various other table name mappings to be performed.
1383          *
1384          *
1385          * @param string|array $vars
1386          *
1387          * May be either a field name or an array of field names. The field names
1388          * can be complete fragments of SQL, for direct inclusion into the SELECT
1389          * query. If an array is given, field aliases can be specified, for example:
1390          *
1391          *   array( 'maxrev' => 'MAX(rev_id)' )
1392          *
1393          * This includes an expression with the alias "maxrev" in the query.
1394          *
1395          * If an expression is given, care must be taken to ensure that it is
1396          * DBMS-independent.
1397          *
1398          *
1399          * @param string|array $conds
1400          *
1401          * May be either a string containing a single condition, or an array of
1402          * conditions. If an array is given, the conditions constructed from each
1403          * element are combined with AND.
1404          *
1405          * Array elements may take one of two forms:
1406          *
1407          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1408          *   - Elements with a string key are interpreted as equality conditions,
1409          *     where the key is the field name.
1410          *     - If the value of such an array element is a scalar (such as a
1411          *       string), it will be treated as data and thus quoted appropriately.
1412          *       If it is null, an IS NULL clause will be added.
1413          *     - If the value is an array, an IN(...) clause will be constructed,
1414          *       such that the field name may match any of the elements in the
1415          *       array. The elements of the array will be quoted.
1416          *
1417          * Note that expressions are often DBMS-dependent in their syntax.
1418          * DBMS-independent wrappers are provided for constructing several types of
1419          * expression commonly used in condition queries. See:
1420          *    - DatabaseBase::buildLike()
1421          *    - DatabaseBase::conditional()
1422          *
1423          *
1424          * @param string|array $options
1425          *
1426          * Optional: Array of query options. Boolean options are specified by
1427          * including them in the array as a string value with a numeric key, for
1428          * example:
1429          *
1430          *    array( 'FOR UPDATE' )
1431          *
1432          * The supported options are:
1433          *
1434          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1435          *     with LIMIT can theoretically be used for paging through a result set,
1436          *     but this is discouraged in MediaWiki for performance reasons.
1437          *
1438          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1439          *     and then the first rows are taken until the limit is reached. LIMIT
1440          *     is applied to a result set after OFFSET.
1441          *
1442          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1443          *     changed until the next COMMIT.
1444          *
1445          *   - DISTINCT: Boolean: return only unique result rows.
1446          *
1447          *   - GROUP BY: May be either an SQL fragment string naming a field or
1448          *     expression to group by, or an array of such SQL fragments.
1449          *
1450          *   - HAVING: May be either an string containing a HAVING clause or an array of
1451          *     conditions building the HAVING clause. If an array is given, the conditions
1452          *     constructed from each element are combined with AND.
1453          *
1454          *   - ORDER BY: May be either an SQL fragment giving a field name or
1455          *     expression to order by, or an array of such SQL fragments.
1456          *
1457          *   - USE INDEX: This may be either a string giving the index name to use
1458          *     for the query, or an array. If it is an associative array, each key
1459          *     gives the table name (or alias), each value gives the index name to
1460          *     use for that table. All strings are SQL fragments and so should be
1461          *     validated by the caller.
1462          *
1463          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1464          *     instead of SELECT.
1465          *
1466          * And also the following boolean MySQL extensions, see the MySQL manual
1467          * for documentation:
1468          *
1469          *    - LOCK IN SHARE MODE
1470          *    - STRAIGHT_JOIN
1471          *    - HIGH_PRIORITY
1472          *    - SQL_BIG_RESULT
1473          *    - SQL_BUFFER_RESULT
1474          *    - SQL_SMALL_RESULT
1475          *    - SQL_CALC_FOUND_ROWS
1476          *    - SQL_CACHE
1477          *    - SQL_NO_CACHE
1478          *
1479          *
1480          * @param string|array $join_conds
1481          *
1482          * Optional associative array of table-specific join conditions. In the
1483          * most common case, this is unnecessary, since the join condition can be
1484          * in $conds. However, it is useful for doing a LEFT JOIN.
1485          *
1486          * The key of the array contains the table name or alias. The value is an
1487          * array with two elements, numbered 0 and 1. The first gives the type of
1488          * join, the second is an SQL fragment giving the join condition for that
1489          * table. For example:
1490          *
1491          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1492          *
1493          * @return ResultWrapper|bool If the query returned no rows, a ResultWrapper
1494          *   with no rows in it will be returned. If there was a query error, a
1495          *   DBQueryError exception will be thrown, except if the "ignore errors"
1496          *   option was set, in which case false will be returned.
1497          */
1498         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1499                 $options = array(), $join_conds = array() ) {
1500                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1501
1502                 return $this->query( $sql, $fname );
1503         }
1504
1505         /**
1506          * The equivalent of DatabaseBase::select() except that the constructed SQL
1507          * is returned, instead of being immediately executed. This can be useful for
1508          * doing UNION queries, where the SQL text of each query is needed. In general,
1509          * however, callers outside of Database classes should just use select().
1510          *
1511          * @param string|array $table Table name
1512          * @param string|array $vars Field names
1513          * @param string|array $conds Conditions
1514          * @param string $fname Caller function name
1515          * @param string|array $options Query options
1516          * @param string|array $join_conds Join conditions
1517          *
1518          * @return string SQL query string.
1519          * @see DatabaseBase::select()
1520          */
1521         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1522                 $options = array(), $join_conds = array()
1523         ) {
1524                 if ( is_array( $vars ) ) {
1525                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1526                 }
1527
1528                 $options = (array)$options;
1529                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1530                         ? $options['USE INDEX']
1531                         : array();
1532
1533                 if ( is_array( $table ) ) {
1534                         $from = ' FROM ' .
1535                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1536                 } elseif ( $table != '' ) {
1537                         if ( $table[0] == ' ' ) {
1538                                 $from = ' FROM ' . $table;
1539                         } else {
1540                                 $from = ' FROM ' .
1541                                         $this->tableNamesWithUseIndexOrJOIN( array( $table ), $useIndexes, array() );
1542                         }
1543                 } else {
1544                         $from = '';
1545                 }
1546
1547                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1548                         $this->makeSelectOptions( $options );
1549
1550                 if ( !empty( $conds ) ) {
1551                         if ( is_array( $conds ) ) {
1552                                 $conds = $this->makeList( $conds, LIST_AND );
1553                         }
1554                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1555                 } else {
1556                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1557                 }
1558
1559                 if ( isset( $options['LIMIT'] ) ) {
1560                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1561                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1562                 }
1563                 $sql = "$sql $postLimitTail";
1564
1565                 if ( isset( $options['EXPLAIN'] ) ) {
1566                         $sql = 'EXPLAIN ' . $sql;
1567                 }
1568
1569                 return $sql;
1570         }
1571
1572         /**
1573          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1574          * that a single row object is returned. If the query returns no rows,
1575          * false is returned.
1576          *
1577          * @param string|array $table Table name
1578          * @param string|array $vars Field names
1579          * @param array $conds Conditions
1580          * @param string $fname Caller function name
1581          * @param string|array $options Query options
1582          * @param array|string $join_conds Join conditions
1583          *
1584          * @return stdClass|bool
1585          */
1586         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1587                 $options = array(), $join_conds = array()
1588         ) {
1589                 $options = (array)$options;
1590                 $options['LIMIT'] = 1;
1591                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1592
1593                 if ( $res === false ) {
1594                         return false;
1595                 }
1596
1597                 if ( !$this->numRows( $res ) ) {
1598                         return false;
1599                 }
1600
1601                 $obj = $this->fetchObject( $res );
1602
1603                 return $obj;
1604         }
1605
1606         /**
1607          * Estimate the number of rows in dataset
1608          *
1609          * MySQL allows you to estimate the number of rows that would be returned
1610          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1611          * index cardinality statistics, and is notoriously inaccurate, especially
1612          * when large numbers of rows have recently been added or deleted.
1613          *
1614          * For DBMSs that don't support fast result size estimation, this function
1615          * will actually perform the SELECT COUNT(*).
1616          *
1617          * Takes the same arguments as DatabaseBase::select().
1618          *
1619          * @param string $table Table name
1620          * @param string $vars Unused
1621          * @param array|string $conds Filters on the table
1622          * @param string $fname Function name for profiling
1623          * @param array $options Options for select
1624          * @return int Row count
1625          */
1626         public function estimateRowCount(
1627                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = array()
1628         ) {
1629                 $rows = 0;
1630                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1631
1632                 if ( $res ) {
1633                         $row = $this->fetchRow( $res );
1634                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1635                 }
1636
1637                 return $rows;
1638         }
1639
1640         /**
1641          * Get the number of rows in dataset
1642          *
1643          * This is useful when trying to do COUNT(*) but with a LIMIT for performance.
1644          *
1645          * Takes the same arguments as DatabaseBase::select().
1646          *
1647          * @param string $table Table name
1648          * @param string $vars Unused
1649          * @param array|string $conds Filters on the table
1650          * @param string $fname Function name for profiling
1651          * @param array $options Options for select
1652          * @return int Row count
1653          * @since 1.24
1654          */
1655         public function selectRowCount(
1656                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = array()
1657         ) {
1658                 $rows = 0;
1659                 $sql = $this->selectSQLText( $table, '1', $conds, $fname, $options );
1660                 $res = $this->query( "SELECT COUNT(*) AS rowcount FROM ($sql) tmp_count" );
1661
1662                 if ( $res ) {
1663                         $row = $this->fetchRow( $res );
1664                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1665                 }
1666
1667                 return $rows;
1668         }
1669
1670         /**
1671          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1672          * It's only slightly flawed. Don't use for anything important.
1673          *
1674          * @param string $sql A SQL Query
1675          *
1676          * @return string
1677          */
1678         static function generalizeSQL( $sql ) {
1679                 # This does the same as the regexp below would do, but in such a way
1680                 # as to avoid crashing php on some large strings.
1681                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1682
1683                 $sql = str_replace( "\\\\", '', $sql );
1684                 $sql = str_replace( "\\'", '', $sql );
1685                 $sql = str_replace( "\\\"", '', $sql );
1686                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1687                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1688
1689                 # All newlines, tabs, etc replaced by single space
1690                 $sql = preg_replace( '/\s+/', ' ', $sql );
1691
1692                 # All numbers => N,
1693                 # except the ones surrounded by characters, e.g. l10n
1694                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1695                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1696
1697                 return $sql;
1698         }
1699
1700         /**
1701          * Determines whether a field exists in a table
1702          *
1703          * @param string $table Table name
1704          * @param string $field Filed to check on that table
1705          * @param string $fname Calling function name (optional)
1706          * @return bool Whether $table has filed $field
1707          */
1708         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1709                 $info = $this->fieldInfo( $table, $field );
1710
1711                 return (bool)$info;
1712         }
1713
1714         /**
1715          * Determines whether an index exists
1716          * Usually throws a DBQueryError on failure
1717          * If errors are explicitly ignored, returns NULL on failure
1718          *
1719          * @param string $table
1720          * @param string $index
1721          * @param string $fname
1722          * @return bool|null
1723          */
1724         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1725                 if ( !$this->tableExists( $table ) ) {
1726                         return null;
1727                 }
1728
1729                 $info = $this->indexInfo( $table, $index, $fname );
1730                 if ( is_null( $info ) ) {
1731                         return null;
1732                 } else {
1733                         return $info !== false;
1734                 }
1735         }
1736
1737         /**
1738          * Query whether a given table exists
1739          *
1740          * @param string $table
1741          * @param string $fname
1742          * @return bool
1743          */
1744         public function tableExists( $table, $fname = __METHOD__ ) {
1745                 $table = $this->tableName( $table );
1746                 $old = $this->ignoreErrors( true );
1747                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1748                 $this->ignoreErrors( $old );
1749
1750                 return (bool)$res;
1751         }
1752
1753         /**
1754          * Determines if a given index is unique
1755          *
1756          * @param string $table
1757          * @param string $index
1758          *
1759          * @return bool
1760          */
1761         public function indexUnique( $table, $index ) {
1762                 $indexInfo = $this->indexInfo( $table, $index );
1763
1764                 if ( !$indexInfo ) {
1765                         return null;
1766                 }
1767
1768                 return !$indexInfo[0]->Non_unique;
1769         }
1770
1771         /**
1772          * Helper for DatabaseBase::insert().
1773          *
1774          * @param array $options
1775          * @return string
1776          */
1777         protected function makeInsertOptions( $options ) {
1778                 return implode( ' ', $options );
1779         }
1780
1781         /**
1782          * INSERT wrapper, inserts an array into a table.
1783          *
1784          * $a may be either:
1785          *
1786          *   - A single associative array. The array keys are the field names, and
1787          *     the values are the values to insert. The values are treated as data
1788          *     and will be quoted appropriately. If NULL is inserted, this will be
1789          *     converted to a database NULL.
1790          *   - An array with numeric keys, holding a list of associative arrays.
1791          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1792          *     each subarray must be identical to each other, and in the same order.
1793          *
1794          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1795          * returns success.
1796          *
1797          * $options is an array of options, with boolean options encoded as values
1798          * with numeric keys, in the same style as $options in
1799          * DatabaseBase::select(). Supported options are:
1800          *
1801          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1802          *     any rows which cause duplicate key errors are not inserted. It's
1803          *     possible to determine how many rows were successfully inserted using
1804          *     DatabaseBase::affectedRows().
1805          *
1806          * @param string $table Table name. This will be passed through
1807          *   DatabaseBase::tableName().
1808          * @param array $a Array of rows to insert
1809          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1810          * @param array $options Array of options
1811          *
1812          * @return bool
1813          */
1814         public function insert( $table, $a, $fname = __METHOD__, $options = array() ) {
1815                 # No rows to insert, easy just return now
1816                 if ( !count( $a ) ) {
1817                         return true;
1818                 }
1819
1820                 $table = $this->tableName( $table );
1821
1822                 if ( !is_array( $options ) ) {
1823                         $options = array( $options );
1824                 }
1825
1826                 $fh = null;
1827                 if ( isset( $options['fileHandle'] ) ) {
1828                         $fh = $options['fileHandle'];
1829                 }
1830                 $options = $this->makeInsertOptions( $options );
1831
1832                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1833                         $multi = true;
1834                         $keys = array_keys( $a[0] );
1835                 } else {
1836                         $multi = false;
1837                         $keys = array_keys( $a );
1838                 }
1839
1840                 $sql = 'INSERT ' . $options .
1841                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1842
1843                 if ( $multi ) {
1844                         $first = true;
1845                         foreach ( $a as $row ) {
1846                                 if ( $first ) {
1847                                         $first = false;
1848                                 } else {
1849                                         $sql .= ',';
1850                                 }
1851                                 $sql .= '(' . $this->makeList( $row ) . ')';
1852                         }
1853                 } else {
1854                         $sql .= '(' . $this->makeList( $a ) . ')';
1855                 }
1856
1857                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1858                         return false;
1859                 } elseif ( $fh !== null ) {
1860                         return true;
1861                 }
1862
1863                 return (bool)$this->query( $sql, $fname );
1864         }
1865
1866         /**
1867          * Make UPDATE options array for DatabaseBase::makeUpdateOptions
1868          *
1869          * @param array $options
1870          * @return array
1871          */
1872         protected function makeUpdateOptionsArray( $options ) {
1873                 if ( !is_array( $options ) ) {
1874                         $options = array( $options );
1875                 }
1876
1877                 $opts = array();
1878
1879                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1880                         $opts[] = $this->lowPriorityOption();
1881                 }
1882
1883                 if ( in_array( 'IGNORE', $options ) ) {
1884                         $opts[] = 'IGNORE';
1885                 }
1886
1887                 return $opts;
1888         }
1889
1890         /**
1891          * Make UPDATE options for the DatabaseBase::update function
1892          *
1893          * @param array $options The options passed to DatabaseBase::update
1894          * @return string
1895          */
1896         protected function makeUpdateOptions( $options ) {
1897                 $opts = $this->makeUpdateOptionsArray( $options );
1898
1899                 return implode( ' ', $opts );
1900         }
1901
1902         /**
1903          * UPDATE wrapper. Takes a condition array and a SET array.
1904          *
1905          * @param string $table Name of the table to UPDATE. This will be passed through
1906          *   DatabaseBase::tableName().
1907          * @param array $values An array of values to SET. For each array element,
1908          *   the key gives the field name, and the value gives the data to set
1909          *   that field to. The data will be quoted by DatabaseBase::addQuotes().
1910          * @param array $conds An array of conditions (WHERE). See
1911          *   DatabaseBase::select() for the details of the format of condition
1912          *   arrays. Use '*' to update all rows.
1913          * @param string $fname The function name of the caller (from __METHOD__),
1914          *   for logging and profiling.
1915          * @param array $options An array of UPDATE options, can be:
1916          *   - IGNORE: Ignore unique key conflicts
1917          *   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1918          * @return bool
1919          */
1920         function update( $table, $values, $conds, $fname = __METHOD__, $options = array() ) {
1921                 $table = $this->tableName( $table );
1922                 $opts = $this->makeUpdateOptions( $options );
1923                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1924
1925                 if ( $conds !== array() && $conds !== '*' ) {
1926                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1927                 }
1928
1929                 return $this->query( $sql, $fname );
1930         }
1931
1932         /**
1933          * Makes an encoded list of strings from an array
1934          *
1935          * @param array $a Containing the data
1936          * @param int $mode Constant
1937          *    - LIST_COMMA: Comma separated, no field names
1938          *    - LIST_AND:   ANDed WHERE clause (without the WHERE). See the
1939          *      documentation for $conds in DatabaseBase::select().
1940          *    - LIST_OR:    ORed WHERE clause (without the WHERE)
1941          *    - LIST_SET:   Comma separated with field names, like a SET clause
1942          *    - LIST_NAMES: Comma separated field names
1943          * @throws MWException|DBUnexpectedError
1944          * @return string
1945          */
1946         public function makeList( $a, $mode = LIST_COMMA ) {
1947                 if ( !is_array( $a ) ) {
1948                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1949                 }
1950
1951                 $first = true;
1952                 $list = '';
1953
1954                 foreach ( $a as $field => $value ) {
1955                         if ( !$first ) {
1956                                 if ( $mode == LIST_AND ) {
1957                                         $list .= ' AND ';
1958                                 } elseif ( $mode == LIST_OR ) {
1959                                         $list .= ' OR ';
1960                                 } else {
1961                                         $list .= ',';
1962                                 }
1963                         } else {
1964                                 $first = false;
1965                         }
1966
1967                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1968                                 $list .= "($value)";
1969                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1970                                 $list .= "$value";
1971                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1972                                 if ( count( $value ) == 0 ) {
1973                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1974                                 } elseif ( count( $value ) == 1 ) {
1975                                         // Special-case single values, as IN isn't terribly efficient
1976                                         // Don't necessarily assume the single key is 0; we don't
1977                                         // enforce linear numeric ordering on other arrays here.
1978                                         $value = array_values( $value );
1979                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1980                                 } else {
1981                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1982                                 }
1983                         } elseif ( $value === null ) {
1984                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1985                                         $list .= "$field IS ";
1986                                 } elseif ( $mode == LIST_SET ) {
1987                                         $list .= "$field = ";
1988                                 }
1989                                 $list .= 'NULL';
1990                         } else {
1991                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1992                                         $list .= "$field = ";
1993                                 }
1994                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1995                         }
1996                 }
1997
1998                 return $list;
1999         }
2000
2001         /**
2002          * Build a partial where clause from a 2-d array such as used for LinkBatch.
2003          * The keys on each level may be either integers or strings.
2004          *
2005          * @param array $data Organized as 2-d
2006          *    array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
2007          * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
2008          * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
2009          * @return string|bool SQL fragment, or false if no items in array
2010          */
2011         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2012                 $conds = array();
2013
2014                 foreach ( $data as $base => $sub ) {
2015                         if ( count( $sub ) ) {
2016                                 $conds[] = $this->makeList(
2017                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
2018                                         LIST_AND );
2019                         }
2020                 }
2021
2022                 if ( $conds ) {
2023                         return $this->makeList( $conds, LIST_OR );
2024                 } else {
2025                         // Nothing to search for...
2026                         return false;
2027                 }
2028         }
2029
2030         /**
2031          * Return aggregated value alias
2032          *
2033          * @param array $valuedata
2034          * @param string $valuename
2035          *
2036          * @return string
2037          */
2038         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2039                 return $valuename;
2040         }
2041
2042         /**
2043          * @param string $field
2044          * @return string
2045          */
2046         public function bitNot( $field ) {
2047                 return "(~$field)";
2048         }
2049
2050         /**
2051          * @param string $fieldLeft
2052          * @param string $fieldRight
2053          * @return string
2054          */
2055         public function bitAnd( $fieldLeft, $fieldRight ) {
2056                 return "($fieldLeft & $fieldRight)";
2057         }
2058
2059         /**
2060          * @param string $fieldLeft
2061          * @param string $fieldRight
2062          * @return string
2063          */
2064         public function bitOr( $fieldLeft, $fieldRight ) {
2065                 return "($fieldLeft | $fieldRight)";
2066         }
2067
2068         /**
2069          * Build a concatenation list to feed into a SQL query
2070          * @param array $stringList List of raw SQL expressions; caller is
2071          *   responsible for any quoting
2072          * @return string
2073          */
2074         public function buildConcat( $stringList ) {
2075                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2076         }
2077
2078         /**
2079          * Build a GROUP_CONCAT or equivalent statement for a query.
2080          *
2081          * This is useful for combining a field for several rows into a single string.
2082          * NULL values will not appear in the output, duplicated values will appear,
2083          * and the resulting delimiter-separated values have no defined sort order.
2084          * Code using the results may need to use the PHP unique() or sort() methods.
2085          *
2086          * @param string $delim Glue to bind the results together
2087          * @param string|array $table Table name
2088          * @param string $field Field name
2089          * @param string|array $conds Conditions
2090          * @param string|array $join_conds Join conditions
2091          * @return string SQL text
2092          * @since 1.23
2093          */
2094         public function buildGroupConcatField(
2095                 $delim, $table, $field, $conds = '', $join_conds = array()
2096         ) {
2097                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
2098
2099                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, array(), $join_conds ) . ')';
2100         }
2101
2102         /**
2103          * Change the current database
2104          *
2105          * @todo Explain what exactly will fail if this is not overridden.
2106          *
2107          * @param string $db
2108          *
2109          * @return bool Success or failure
2110          */
2111         public function selectDB( $db ) {
2112                 # Stub. Shouldn't cause serious problems if it's not overridden, but
2113                 # if your database engine supports a concept similar to MySQL's
2114                 # databases you may as well.
2115                 $this->mDBname = $db;
2116
2117                 return true;
2118         }
2119
2120         /**
2121          * Get the current DB name
2122          * @return string
2123          */
2124         public function getDBname() {
2125                 return $this->mDBname;
2126         }
2127
2128         /**
2129          * Get the server hostname or IP address
2130          * @return string
2131          */
2132         public function getServer() {
2133                 return $this->mServer;
2134         }
2135
2136         /**
2137          * Format a table name ready for use in constructing an SQL query
2138          *
2139          * This does two important things: it quotes the table names to clean them up,
2140          * and it adds a table prefix if only given a table name with no quotes.
2141          *
2142          * All functions of this object which require a table name call this function
2143          * themselves. Pass the canonical name to such functions. This is only needed
2144          * when calling query() directly.
2145          *
2146          * @param string $name Database table name
2147          * @param string $format One of:
2148          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2149          *            so that it can be used in a query.
2150          *   raw - Do not add identifier quotes to the table name
2151          * @return string Full database name
2152          */
2153         public function tableName( $name, $format = 'quoted' ) {
2154                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables, $wgSharedSchema;
2155                 # Skip the entire process when we have a string quoted on both ends.
2156                 # Note that we check the end so that we will still quote any use of
2157                 # use of `database`.table. But won't break things if someone wants
2158                 # to query a database table with a dot in the name.
2159                 if ( $this->isQuotedIdentifier( $name ) ) {
2160                         return $name;
2161                 }
2162
2163                 # Lets test for any bits of text that should never show up in a table
2164                 # name. Basically anything like JOIN or ON which are actually part of
2165                 # SQL queries, but may end up inside of the table value to combine
2166                 # sql. Such as how the API is doing.
2167                 # Note that we use a whitespace test rather than a \b test to avoid
2168                 # any remote case where a word like on may be inside of a table name
2169                 # surrounded by symbols which may be considered word breaks.
2170                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2171                         return $name;
2172                 }
2173
2174                 # Split database and table into proper variables.
2175                 # We reverse the explode so that database.table and table both output
2176                 # the correct table.
2177                 $dbDetails = explode( '.', $name, 3 );
2178                 if ( count( $dbDetails ) == 3 ) {
2179                         list( $database, $schema, $table ) = $dbDetails;
2180                         # We don't want any prefix added in this case
2181                         $prefix = '';
2182                 } elseif ( count( $dbDetails ) == 2 ) {
2183                         list( $database, $table ) = $dbDetails;
2184                         # We don't want any prefix added in this case
2185                         # In dbs that support it, $database may actually be the schema
2186                         # but that doesn't affect any of the functionality here
2187                         $prefix = '';
2188                         $schema = null;
2189                 } else {
2190                         list( $table ) = $dbDetails;
2191                         if ( $wgSharedDB !== null # We have a shared database
2192                                 && $this->mForeign == false # We're not working on a foreign database
2193                                 && !$this->isQuotedIdentifier( $table ) # Prevent shared tables listing '`table`'
2194                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2195                         ) {
2196                                 $database = $wgSharedDB;
2197                                 $schema = $wgSharedSchema === null ? $this->mSchema : $wgSharedSchema;
2198                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2199                         } else {
2200                                 $database = null;
2201                                 $schema = $this->mSchema; # Default schema
2202                                 $prefix = $this->mTablePrefix; # Default prefix
2203                         }
2204                 }
2205
2206                 # Quote $table and apply the prefix if not quoted.
2207                 # $tableName might be empty if this is called from Database::replaceVars()
2208                 $tableName = "{$prefix}{$table}";
2209                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) && $tableName !== '' ) {
2210                         $tableName = $this->addIdentifierQuotes( $tableName );
2211                 }
2212
2213                 # Quote $schema and merge it with the table name if needed
2214                 if ( $schema !== null ) {
2215                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $schema ) ) {
2216                                 $schema = $this->addIdentifierQuotes( $schema );
2217                         }
2218                         $tableName = $schema . '.' . $tableName;
2219                 }
2220
2221                 # Quote $database and merge it with the table name if needed
2222                 if ( $database !== null ) {
2223                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2224                                 $database = $this->addIdentifierQuotes( $database );
2225                         }
2226                         $tableName = $database . '.' . $tableName;
2227                 }
2228
2229                 return $tableName;
2230         }
2231
2232         /**
2233          * Fetch a number of table names into an array
2234          * This is handy when you need to construct SQL for joins
2235          *
2236          * Example:
2237          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2238          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2239          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2240          *
2241          * @return array
2242          */
2243         public function tableNames() {
2244                 $inArray = func_get_args();
2245                 $retVal = array();
2246
2247                 foreach ( $inArray as $name ) {
2248                         $retVal[$name] = $this->tableName( $name );
2249                 }
2250
2251                 return $retVal;
2252         }
2253
2254         /**
2255          * Fetch a number of table names into an zero-indexed numerical array
2256          * This is handy when you need to construct SQL for joins
2257          *
2258          * Example:
2259          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2260          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2261          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2262          *
2263          * @return array
2264          */
2265         public function tableNamesN() {
2266                 $inArray = func_get_args();
2267                 $retVal = array();
2268
2269                 foreach ( $inArray as $name ) {
2270                         $retVal[] = $this->tableName( $name );
2271                 }
2272
2273                 return $retVal;
2274         }
2275
2276         /**
2277          * Get an aliased table name
2278          * e.g. tableName AS newTableName
2279          *
2280          * @param string $name Table name, see tableName()
2281          * @param string|bool $alias Alias (optional)
2282          * @return string SQL name for aliased table. Will not alias a table to its own name
2283          */
2284         public function tableNameWithAlias( $name, $alias = false ) {
2285                 if ( !$alias || $alias == $name ) {
2286                         return $this->tableName( $name );
2287                 } else {
2288                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2289                 }
2290         }
2291
2292         /**
2293          * Gets an array of aliased table names
2294          *
2295          * @param array $tables Array( [alias] => table )
2296          * @return string[] See tableNameWithAlias()
2297          */
2298         public function tableNamesWithAlias( $tables ) {
2299                 $retval = array();
2300                 foreach ( $tables as $alias => $table ) {
2301                         if ( is_numeric( $alias ) ) {
2302                                 $alias = $table;
2303                         }
2304                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2305                 }
2306
2307                 return $retval;
2308         }
2309
2310         /**
2311          * Get an aliased field name
2312          * e.g. fieldName AS newFieldName
2313          *
2314          * @param string $name Field name
2315          * @param string|bool $alias Alias (optional)
2316          * @return string SQL name for aliased field. Will not alias a field to its own name
2317          */
2318         public function fieldNameWithAlias( $name, $alias = false ) {
2319                 if ( !$alias || (string)$alias === (string)$name ) {
2320                         return $name;
2321                 } else {
2322                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2323                 }
2324         }
2325
2326         /**
2327          * Gets an array of aliased field names
2328          *
2329          * @param array $fields Array( [alias] => field )
2330          * @return string[] See fieldNameWithAlias()
2331          */
2332         public function fieldNamesWithAlias( $fields ) {
2333                 $retval = array();
2334                 foreach ( $fields as $alias => $field ) {
2335                         if ( is_numeric( $alias ) ) {
2336                                 $alias = $field;
2337                         }
2338                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2339                 }
2340
2341                 return $retval;
2342         }
2343
2344         /**
2345          * Get the aliased table name clause for a FROM clause
2346          * which might have a JOIN and/or USE INDEX clause
2347          *
2348          * @param array $tables ( [alias] => table )
2349          * @param array $use_index Same as for select()
2350          * @param array $join_conds Same as for select()
2351          * @return string
2352          */
2353         protected function tableNamesWithUseIndexOrJOIN(
2354                 $tables, $use_index = array(), $join_conds = array()
2355         ) {
2356                 $ret = array();
2357                 $retJOIN = array();
2358                 $use_index = (array)$use_index;
2359                 $join_conds = (array)$join_conds;
2360
2361                 foreach ( $tables as $alias => $table ) {
2362                         if ( !is_string( $alias ) ) {
2363                                 // No alias? Set it equal to the table name
2364                                 $alias = $table;
2365                         }
2366                         // Is there a JOIN clause for this table?
2367                         if ( isset( $join_conds[$alias] ) ) {
2368                                 list( $joinType, $conds ) = $join_conds[$alias];
2369                                 $tableClause = $joinType;
2370                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2371                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2372                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2373                                         if ( $use != '' ) {
2374                                                 $tableClause .= ' ' . $use;
2375                                         }
2376                                 }
2377                                 $on = $this->makeList( (array)$conds, LIST_AND );
2378                                 if ( $on != '' ) {
2379                                         $tableClause .= ' ON (' . $on . ')';
2380                                 }
2381
2382                                 $retJOIN[] = $tableClause;
2383                         } elseif ( isset( $use_index[$alias] ) ) {
2384                                 // Is there an INDEX clause for this table?
2385                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2386                                 $tableClause .= ' ' . $this->useIndexClause(
2387                                         implode( ',', (array)$use_index[$alias] )
2388                                 );
2389
2390                                 $ret[] = $tableClause;
2391                         } else {
2392                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2393
2394                                 $ret[] = $tableClause;
2395                         }
2396                 }
2397
2398                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2399                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2400                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2401
2402                 // Compile our final table clause
2403                 return implode( ' ', array( $implicitJoins, $explicitJoins ) );
2404         }
2405
2406         /**
2407          * Get the name of an index in a given table
2408          *
2409          * @param string $index
2410          * @return string
2411          */
2412         protected function indexName( $index ) {
2413                 // Backwards-compatibility hack
2414                 $renamed = array(
2415                         'ar_usertext_timestamp' => 'usertext_timestamp',
2416                         'un_user_id' => 'user_id',
2417                         'un_user_ip' => 'user_ip',
2418                 );
2419
2420                 if ( isset( $renamed[$index] ) ) {
2421                         return $renamed[$index];
2422                 } else {
2423                         return $index;
2424                 }
2425         }
2426
2427         /**
2428          * Adds quotes and backslashes.
2429          *
2430          * @param string $s
2431          * @return string
2432          */
2433         public function addQuotes( $s ) {
2434                 if ( $s === null ) {
2435                         return 'NULL';
2436                 } else {
2437                         # This will also quote numeric values. This should be harmless,
2438                         # and protects against weird problems that occur when they really
2439                         # _are_ strings such as article titles and string->number->string
2440                         # conversion is not 1:1.
2441                         return "'" . $this->strencode( $s ) . "'";
2442                 }
2443         }
2444
2445         /**
2446          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2447          * MySQL uses `backticks` while basically everything else uses double quotes.
2448          * Since MySQL is the odd one out here the double quotes are our generic
2449          * and we implement backticks in DatabaseMysql.
2450          *
2451          * @param string $s
2452          * @return string
2453          */
2454         public function addIdentifierQuotes( $s ) {
2455                 return '"' . str_replace( '"', '""', $s ) . '"';
2456         }
2457
2458         /**
2459          * Returns if the given identifier looks quoted or not according to
2460          * the database convention for quoting identifiers .
2461          *
2462          * @param string $name
2463          * @return bool
2464          */
2465         public function isQuotedIdentifier( $name ) {
2466                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2467         }
2468
2469         /**
2470          * @param string $s
2471          * @return string
2472          */
2473         protected function escapeLikeInternal( $s ) {
2474                 return addcslashes( $s, '\%_' );
2475         }
2476
2477         /**
2478          * LIKE statement wrapper, receives a variable-length argument list with
2479          * parts of pattern to match containing either string literals that will be
2480          * escaped or tokens returned by anyChar() or anyString(). Alternatively,
2481          * the function could be provided with an array of aforementioned
2482          * parameters.
2483          *
2484          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
2485          * a LIKE clause that searches for subpages of 'My page title'.
2486          * Alternatively:
2487          *   $pattern = array( 'My_page_title/', $dbr->anyString() );
2488          *   $query .= $dbr->buildLike( $pattern );
2489          *
2490          * @since 1.16
2491          * @return string Fully built LIKE statement
2492          */
2493         public function buildLike() {
2494                 $params = func_get_args();
2495
2496                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2497                         $params = $params[0];
2498                 }
2499
2500                 $s = '';
2501
2502                 foreach ( $params as $value ) {
2503                         if ( $value instanceof LikeMatch ) {
2504                                 $s .= $value->toString();
2505                         } else {
2506                                 $s .= $this->escapeLikeInternal( $value );
2507                         }
2508                 }
2509
2510                 return " LIKE {$this->addQuotes( $s )} ";
2511         }
2512
2513         /**
2514          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2515          *
2516          * @return LikeMatch
2517          */
2518         public function anyChar() {
2519                 return new LikeMatch( '_' );
2520         }
2521
2522         /**
2523          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2524          *
2525          * @return LikeMatch
2526          */
2527         public function anyString() {
2528                 return new LikeMatch( '%' );
2529         }
2530
2531         /**
2532          * Returns an appropriately quoted sequence value for inserting a new row.
2533          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2534          * subclass will return an integer, and save the value for insertId()
2535          *
2536          * Any implementation of this function should *not* involve reusing
2537          * sequence numbers created for rolled-back transactions.
2538          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2539          * @param string $seqName
2540          * @return null|int
2541          */
2542         public function nextSequenceValue( $seqName ) {
2543                 return null;
2544         }
2545
2546         /**
2547          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2548          * is only needed because a) MySQL must be as efficient as possible due to
2549          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2550          * which index to pick. Anyway, other databases might have different
2551          * indexes on a given table. So don't bother overriding this unless you're
2552          * MySQL.
2553          * @param string $index
2554          * @return string
2555          */
2556         public function useIndexClause( $index ) {
2557                 return '';
2558         }
2559
2560         /**
2561          * REPLACE query wrapper.
2562          *
2563          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2564          * except that when there is a duplicate key error, the old row is deleted
2565          * and the new row is inserted in its place.
2566          *
2567          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2568          * perform the delete, we need to know what the unique indexes are so that
2569          * we know how to find the conflicting rows.
2570          *
2571          * It may be more efficient to leave off unique indexes which are unlikely
2572          * to collide. However if you do this, you run the risk of encountering
2573          * errors which wouldn't have occurred in MySQL.
2574          *
2575          * @param string $table The table to replace the row(s) in.
2576          * @param array $uniqueIndexes Is an array of indexes. Each element may be either
2577          *    a field name or an array of field names
2578          * @param array $rows Can be either a single row to insert, or multiple rows,
2579          *    in the same format as for DatabaseBase::insert()
2580          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2581          */
2582         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2583                 $quotedTable = $this->tableName( $table );
2584
2585                 if ( count( $rows ) == 0 ) {
2586                         return;
2587                 }
2588
2589                 # Single row case
2590                 if ( !is_array( reset( $rows ) ) ) {
2591                         $rows = array( $rows );
2592                 }
2593
2594                 foreach ( $rows as $row ) {
2595                         # Delete rows which collide
2596                         if ( $uniqueIndexes ) {
2597                                 $sql = "DELETE FROM $quotedTable WHERE ";
2598                                 $first = true;
2599                                 foreach ( $uniqueIndexes as $index ) {
2600                                         if ( $first ) {
2601                                                 $first = false;
2602                                                 $sql .= '( ';
2603                                         } else {
2604                                                 $sql .= ' ) OR ( ';
2605                                         }
2606                                         if ( is_array( $index ) ) {
2607                                                 $first2 = true;
2608                                                 foreach ( $index as $col ) {
2609                                                         if ( $first2 ) {
2610                                                                 $first2 = false;
2611                                                         } else {
2612                                                                 $sql .= ' AND ';
2613                                                         }
2614                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2615                                                 }
2616                                         } else {
2617                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2618                                         }
2619                                 }
2620                                 $sql .= ' )';
2621                                 $this->query( $sql, $fname );
2622                         }
2623
2624                         # Now insert the row
2625                         $this->insert( $table, $row, $fname );
2626                 }
2627         }
2628
2629         /**
2630          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2631          * statement.
2632          *
2633          * @param string $table Table name
2634          * @param array|string $rows Row(s) to insert
2635          * @param string $fname Caller function name
2636          *
2637          * @return ResultWrapper
2638          */
2639         protected function nativeReplace( $table, $rows, $fname ) {
2640                 $table = $this->tableName( $table );
2641
2642                 # Single row case
2643                 if ( !is_array( reset( $rows ) ) ) {
2644                         $rows = array( $rows );
2645                 }
2646
2647                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2648                 $first = true;
2649
2650                 foreach ( $rows as $row ) {
2651                         if ( $first ) {
2652                                 $first = false;
2653                         } else {
2654                                 $sql .= ',';
2655                         }
2656
2657                         $sql .= '(' . $this->makeList( $row ) . ')';
2658                 }
2659
2660                 return $this->query( $sql, $fname );
2661         }
2662
2663         /**
2664          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
2665          *
2666          * This updates any conflicting rows (according to the unique indexes) using
2667          * the provided SET clause and inserts any remaining (non-conflicted) rows.
2668          *
2669          * $rows may be either:
2670          *   - A single associative array. The array keys are the field names, and
2671          *     the values are the values to insert. The values are treated as data
2672          *     and will be quoted appropriately. If NULL is inserted, this will be
2673          *     converted to a database NULL.
2674          *   - An array with numeric keys, holding a list of associative arrays.
2675          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
2676          *     each subarray must be identical to each other, and in the same order.
2677          *
2678          * It may be more efficient to leave off unique indexes which are unlikely
2679          * to collide. However if you do this, you run the risk of encountering
2680          * errors which wouldn't have occurred in MySQL.
2681          *
2682          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
2683          * returns success.
2684          *
2685          * @since 1.22
2686          *
2687          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
2688          * @param array $rows A single row or list of rows to insert
2689          * @param array $uniqueIndexes List of single field names or field name tuples
2690          * @param array $set An array of values to SET. For each array element, the
2691          *   key gives the field name, and the value gives the data to set that
2692          *   field to. The data will be quoted by DatabaseBase::addQuotes().
2693          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2694          * @throws Exception
2695          * @return bool
2696          */
2697         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2698                 $fname = __METHOD__
2699         ) {
2700                 if ( !count( $rows ) ) {
2701                         return true; // nothing to do
2702                 }
2703
2704                 if ( !is_array( reset( $rows ) ) ) {
2705                         $rows = array( $rows );
2706                 }
2707
2708                 if ( count( $uniqueIndexes ) ) {
2709                         $clauses = array(); // list WHERE clauses that each identify a single row
2710                         foreach ( $rows as $row ) {
2711                                 foreach ( $uniqueIndexes as $index ) {
2712                                         $index = is_array( $index ) ? $index : array( $index ); // columns
2713                                         $rowKey = array(); // unique key to this row
2714                                         foreach ( $index as $column ) {
2715                                                 $rowKey[$column] = $row[$column];
2716                                         }
2717                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2718                                 }
2719                         }
2720                         $where = array( $this->makeList( $clauses, LIST_OR ) );
2721                 } else {
2722                         $where = false;
2723                 }
2724
2725                 $useTrx = !$this->mTrxLevel;
2726                 if ( $useTrx ) {
2727                         $this->begin( $fname );
2728                 }
2729                 try {
2730                         # Update any existing conflicting row(s)
2731                         if ( $where !== false ) {
2732                                 $ok = $this->update( $table, $set, $where, $fname );
2733                         } else {
2734                                 $ok = true;
2735                         }
2736                         # Now insert any non-conflicting row(s)
2737                         $ok = $this->insert( $table, $rows, $fname, array( 'IGNORE' ) ) && $ok;
2738                 } catch ( Exception $e ) {
2739                         if ( $useTrx ) {
2740                                 $this->rollback( $fname );
2741                         }
2742                         throw $e;
2743                 }
2744                 if ( $useTrx ) {
2745                         $this->commit( $fname );
2746                 }
2747
2748                 return $ok;
2749         }
2750
2751         /**
2752          * DELETE where the condition is a join.
2753          *
2754          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2755          * we use sub-selects
2756          *
2757          * For safety, an empty $conds will not delete everything. If you want to
2758          * delete all rows where the join condition matches, set $conds='*'.
2759          *
2760          * DO NOT put the join condition in $conds.
2761          *
2762          * @param string $delTable The table to delete from.
2763          * @param string $joinTable The other table.
2764          * @param string $delVar The variable to join on, in the first table.
2765          * @param string $joinVar The variable to join on, in the second table.
2766          * @param array $conds Condition array of field names mapped to variables,
2767          *   ANDed together in the WHERE clause
2768          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2769          * @throws DBUnexpectedError
2770          */
2771         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2772                 $fname = __METHOD__
2773         ) {
2774                 if ( !$conds ) {
2775                         throw new DBUnexpectedError( $this,
2776                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2777                 }
2778
2779                 $delTable = $this->tableName( $delTable );
2780                 $joinTable = $this->tableName( $joinTable );
2781                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2782                 if ( $conds != '*' ) {
2783                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2784                 }
2785                 $sql .= ')';
2786
2787                 $this->query( $sql, $fname );
2788         }
2789
2790         /**
2791          * Returns the size of a text field, or -1 for "unlimited"
2792          *
2793          * @param string $table
2794          * @param string $field
2795          * @return int
2796          */
2797         public function textFieldSize( $table, $field ) {
2798                 $table = $this->tableName( $table );
2799                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2800                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2801                 $row = $this->fetchObject( $res );
2802
2803                 $m = array();
2804
2805                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2806                         $size = $m[1];
2807                 } else {
2808                         $size = -1;
2809                 }
2810
2811                 return $size;
2812         }
2813
2814         /**
2815          * A string to insert into queries to show that they're low-priority, like
2816          * MySQL's LOW_PRIORITY. If no such feature exists, return an empty
2817          * string and nothing bad should happen.
2818          *
2819          * @return string Returns the text of the low priority option if it is
2820          *   supported, or a blank string otherwise
2821          */
2822         public function lowPriorityOption() {
2823                 return '';
2824         }
2825
2826         /**
2827          * DELETE query wrapper.
2828          *
2829          * @param array $table Table name
2830          * @param string|array $conds Array of conditions. See $conds in DatabaseBase::select()
2831          *   for the format. Use $conds == "*" to delete all rows
2832          * @param string $fname Name of the calling function
2833          * @throws DBUnexpectedError
2834          * @return bool|ResultWrapper
2835          */
2836         public function delete( $table, $conds, $fname = __METHOD__ ) {
2837                 if ( !$conds ) {
2838                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2839                 }
2840
2841                 $table = $this->tableName( $table );
2842                 $sql = "DELETE FROM $table";
2843
2844                 if ( $conds != '*' ) {
2845                         if ( is_array( $conds ) ) {
2846                                 $conds = $this->makeList( $conds, LIST_AND );
2847                         }
2848                         $sql .= ' WHERE ' . $conds;
2849                 }
2850
2851                 return $this->query( $sql, $fname );
2852         }
2853
2854         /**
2855          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2856          * into another table.
2857          *
2858          * @param string $destTable The table name to insert into
2859          * @param string|array $srcTable May be either a table name, or an array of table names
2860          *    to include in a join.
2861          *
2862          * @param array $varMap Must be an associative array of the form
2863          *    array( 'dest1' => 'source1', ...). Source items may be literals
2864          *    rather than field names, but strings should be quoted with
2865          *    DatabaseBase::addQuotes()
2866          *
2867          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2868          *    the details of the format of condition arrays. May be "*" to copy the
2869          *    whole table.
2870          *
2871          * @param string $fname The function name of the caller, from __METHOD__
2872          *
2873          * @param array $insertOptions Options for the INSERT part of the query, see
2874          *    DatabaseBase::insert() for details.
2875          * @param array $selectOptions Options for the SELECT part of the query, see
2876          *    DatabaseBase::select() for details.
2877          *
2878          * @return ResultWrapper
2879          */
2880         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2881                 $fname = __METHOD__,
2882                 $insertOptions = array(), $selectOptions = array()
2883         ) {
2884                 $destTable = $this->tableName( $destTable );
2885
2886                 if ( !is_array( $insertOptions ) ) {
2887                         $insertOptions = array( $insertOptions );
2888                 }
2889
2890                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2891
2892                 if ( !is_array( $selectOptions ) ) {
2893                         $selectOptions = array( $selectOptions );
2894                 }
2895
2896                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2897
2898                 if ( is_array( $srcTable ) ) {
2899                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2900                 } else {
2901                         $srcTable = $this->tableName( $srcTable );
2902                 }
2903
2904                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2905                         " SELECT $startOpts " . implode( ',', $varMap ) .
2906                         " FROM $srcTable $useIndex ";
2907
2908                 if ( $conds != '*' ) {
2909                         if ( is_array( $conds ) ) {
2910                                 $conds = $this->makeList( $conds, LIST_AND );
2911                         }
2912                         $sql .= " WHERE $conds";
2913                 }
2914
2915                 $sql .= " $tailOpts";
2916
2917                 return $this->query( $sql, $fname );
2918         }
2919
2920         /**
2921          * Construct a LIMIT query with optional offset. This is used for query
2922          * pages. The SQL should be adjusted so that only the first $limit rows
2923          * are returned. If $offset is provided as well, then the first $offset
2924          * rows should be discarded, and the next $limit rows should be returned.
2925          * If the result of the query is not ordered, then the rows to be returned
2926          * are theoretically arbitrary.
2927          *
2928          * $sql is expected to be a SELECT, if that makes a difference.
2929          *
2930          * The version provided by default works in MySQL and SQLite. It will very
2931          * likely need to be overridden for most other DBMSes.
2932          *
2933          * @param string $sql SQL query we will append the limit too
2934          * @param int $limit The SQL limit
2935          * @param int|bool $offset The SQL offset (default false)
2936          * @throws DBUnexpectedError
2937          * @return string
2938          */
2939         public function limitResult( $sql, $limit, $offset = false ) {
2940                 if ( !is_numeric( $limit ) ) {
2941                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2942                 }
2943
2944                 return "$sql LIMIT "
2945                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2946                         . "{$limit} ";
2947         }
2948
2949         /**
2950          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2951          * within the UNION construct.
2952          * @return bool
2953          */
2954         public function unionSupportsOrderAndLimit() {
2955                 return true; // True for almost every DB supported
2956         }
2957
2958         /**
2959          * Construct a UNION query
2960          * This is used for providing overload point for other DB abstractions
2961          * not compatible with the MySQL syntax.
2962          * @param array $sqls SQL statements to combine
2963          * @param bool $all Use UNION ALL
2964          * @return string SQL fragment
2965          */
2966         public function unionQueries( $sqls, $all ) {
2967                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2968
2969                 return '(' . implode( $glue, $sqls ) . ')';
2970         }
2971
2972         /**
2973          * Returns an SQL expression for a simple conditional. This doesn't need
2974          * to be overridden unless CASE isn't supported in your DBMS.
2975          *
2976          * @param string|array $cond SQL expression which will result in a boolean value
2977          * @param string $trueVal SQL expression to return if true
2978          * @param string $falseVal SQL expression to return if false
2979          * @return string SQL fragment
2980          */
2981         public function conditional( $cond, $trueVal, $falseVal ) {
2982                 if ( is_array( $cond ) ) {
2983                         $cond = $this->makeList( $cond, LIST_AND );
2984                 }
2985
2986                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2987         }
2988
2989         /**
2990          * Returns a comand for str_replace function in SQL query.
2991          * Uses REPLACE() in MySQL
2992          *
2993          * @param string $orig Column to modify
2994          * @param string $old Column to seek
2995          * @param string $new Column to replace with
2996          *
2997          * @return string
2998          */
2999         public function strreplace( $orig, $old, $new ) {
3000                 return "REPLACE({$orig}, {$old}, {$new})";
3001         }
3002
3003         /**
3004          * Determines how long the server has been up
3005          * STUB
3006          *
3007          * @return int
3008          */
3009         public function getServerUptime() {
3010                 return 0;
3011         }
3012
3013         /**
3014          * Determines if the last failure was due to a deadlock
3015          * STUB
3016          *
3017          * @return bool
3018          */
3019         public function wasDeadlock() {
3020                 return false;
3021         }
3022
3023         /**
3024          * Determines if the last failure was due to a lock timeout
3025          * STUB
3026          *
3027          * @return bool
3028          */
3029         public function wasLockTimeout() {
3030                 return false;
3031         }
3032
3033         /**
3034          * Determines if the last query error was something that should be dealt
3035          * with by pinging the connection and reissuing the query.
3036          * STUB
3037          *
3038          * @return bool
3039          */
3040         public function wasErrorReissuable() {
3041                 return false;
3042         }
3043
3044         /**
3045          * Determines if the last failure was due to the database being read-only.
3046          * STUB
3047          *
3048          * @return bool
3049          */
3050         public function wasReadOnlyError() {
3051                 return false;
3052         }
3053
3054         /**
3055          * Perform a deadlock-prone transaction.
3056          *
3057          * This function invokes a callback function to perform a set of write
3058          * queries. If a deadlock occurs during the processing, the transaction
3059          * will be rolled back and the callback function will be called again.
3060          *
3061          * Usage:
3062          *   $dbw->deadlockLoop( callback, ... );
3063          *
3064          * Extra arguments are passed through to the specified callback function.
3065          *
3066          * Returns whatever the callback function returned on its successful,
3067          * iteration, or false on error, for example if the retry limit was
3068          * reached.
3069          *
3070          * @return bool
3071          */
3072         public function deadlockLoop() {
3073                 $this->begin( __METHOD__ );
3074                 $args = func_get_args();
3075                 $function = array_shift( $args );
3076                 $oldIgnore = $this->ignoreErrors( true );
3077                 $tries = self::DEADLOCK_TRIES;
3078
3079                 if ( is_array( $function ) ) {
3080                         $fname = $function[0];
3081                 } else {
3082                         $fname = $function;
3083                 }
3084
3085                 do {
3086                         $retVal = call_user_func_array( $function, $args );
3087                         $error = $this->lastError();
3088                         $errno = $this->lastErrno();
3089                         $sql = $this->lastQuery();
3090
3091                         if ( $errno ) {
3092                                 if ( $this->wasDeadlock() ) {
3093                                         # Retry
3094                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3095                                 } else {
3096                                         $this->reportQueryError( $error, $errno, $sql, $fname );
3097                                 }
3098                         }
3099                 } while ( $this->wasDeadlock() && --$tries > 0 );
3100
3101                 $this->ignoreErrors( $oldIgnore );
3102
3103                 if ( $tries <= 0 ) {
3104                         $this->rollback( __METHOD__ );
3105                         $this->reportQueryError( $error, $errno, $sql, $fname );
3106
3107                         return false;
3108                 } else {
3109                         $this->commit( __METHOD__ );
3110
3111                         return $retVal;
3112                 }
3113         }
3114
3115         /**
3116          * Wait for the slave to catch up to a given master position.
3117          *
3118          * @param DBMasterPos $pos
3119          * @param int $timeout The maximum number of seconds to wait for
3120          *   synchronisation
3121          * @return int Zero if the slave was past that position already,
3122          *   greater than zero if we waited for some period of time, less than
3123          *   zero if we timed out.
3124          */
3125         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3126                 # Real waits are implemented in the subclass.
3127                 return 0;
3128         }
3129
3130         /**
3131          * Get the replication position of this slave
3132          *
3133          * @return DBMasterPos|bool False if this is not a slave.
3134          */
3135         public function getSlavePos() {
3136                 # Stub
3137                 return false;
3138         }
3139
3140         /**
3141          * Get the position of this master
3142          *
3143          * @return DBMasterPos|bool False if this is not a master
3144          */
3145         public function getMasterPos() {
3146                 # Stub
3147                 return false;
3148         }
3149
3150         /**
3151          * Run an anonymous function as soon as there is no transaction pending.
3152          * If there is a transaction and it is rolled back, then the callback is cancelled.
3153          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
3154          * Callbacks must commit any transactions that they begin.
3155          *
3156          * This is useful for updates to different systems or when separate transactions are needed.
3157          * For example, one might want to enqueue jobs into a system outside the database, but only
3158          * after the database is updated so that the jobs will see the data when they actually run.
3159          * It can also be used for updates that easily cause deadlocks if locks are held too long.
3160          *
3161          * @param callable $callback
3162          * @since 1.20
3163          */
3164         final public function onTransactionIdle( $callback ) {
3165                 $this->mTrxIdleCallbacks[] = array( $callback, wfGetCaller() );
3166                 if ( !$this->mTrxLevel ) {
3167                         $this->runOnTransactionIdleCallbacks();
3168                 }
3169         }
3170
3171         /**
3172          * Run an anonymous function before the current transaction commits or now if there is none.
3173          * If there is a transaction and it is rolled back, then the callback is cancelled.
3174          * Callbacks must not start nor commit any transactions.
3175          *
3176          * This is useful for updates that easily cause deadlocks if locks are held too long
3177          * but where atomicity is strongly desired for these updates and some related updates.
3178          *
3179          * @param callable $callback
3180          * @since 1.22
3181          */
3182         final public function onTransactionPreCommitOrIdle( $callback ) {
3183                 if ( $this->mTrxLevel ) {
3184                         $this->mTrxPreCommitCallbacks[] = array( $callback, wfGetCaller() );
3185                 } else {
3186                         $this->onTransactionIdle( $callback ); // this will trigger immediately
3187                 }
3188         }
3189
3190         /**
3191          * Actually any "on transaction idle" callbacks.
3192          *
3193          * @since 1.20
3194          */
3195         protected function runOnTransactionIdleCallbacks() {
3196                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
3197
3198                 $e = $ePrior = null; // last exception
3199                 do { // callbacks may add callbacks :)
3200                         $callbacks = $this->mTrxIdleCallbacks;
3201                         $this->mTrxIdleCallbacks = array(); // recursion guard
3202                         foreach ( $callbacks as $callback ) {
3203                                 try {
3204                                         list( $phpCallback ) = $callback;
3205                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
3206                                         call_user_func( $phpCallback );
3207                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3208                                 } catch ( Exception $e ) {
3209                                         if ( $ePrior ) {
3210                                                 MWExceptionHandler::logException( $ePrior );
3211                                         }
3212                                         $ePrior = $e;
3213                                 }
3214                         }
3215                 } while ( count( $this->mTrxIdleCallbacks ) );
3216
3217                 if ( $e instanceof Exception ) {
3218                         throw $e; // re-throw any last exception
3219                 }
3220         }
3221
3222         /**
3223          * Actually any "on transaction pre-commit" callbacks.
3224          *
3225          * @since 1.22
3226          */
3227         protected function runOnTransactionPreCommitCallbacks() {
3228                 $e = $ePrior = null; // last exception
3229                 do { // callbacks may add callbacks :)
3230                         $callbacks = $this->mTrxPreCommitCallbacks;
3231                         $this->mTrxPreCommitCallbacks = array(); // recursion guard
3232                         foreach ( $callbacks as $callback ) {
3233                                 try {
3234                                         list( $phpCallback ) = $callback;
3235                                         call_user_func( $phpCallback );
3236                                 } catch ( Exception $e ) {
3237                                         if ( $ePrior ) {
3238                                                 MWExceptionHandler::logException( $ePrior );
3239                                         }
3240                                         $ePrior = $e;
3241                                 }
3242                         }
3243                 } while ( count( $this->mTrxPreCommitCallbacks ) );
3244
3245                 if ( $e instanceof Exception ) {
3246                         throw $e; // re-throw any last exception
3247                 }
3248         }
3249
3250         /**
3251          * Begin an atomic section of statements
3252          *
3253          * If a transaction has been started already, just keep track of the given
3254          * section name to make sure the transaction is not committed pre-maturely.
3255          * This function can be used in layers (with sub-sections), so use a stack
3256          * to keep track of the different atomic sections. If there is no transaction,
3257          * start one implicitly.
3258          *
3259          * The goal of this function is to create an atomic section of SQL queries
3260          * without having to start a new transaction if it already exists.
3261          *
3262          * Atomic sections are more strict than transactions. With transactions,
3263          * attempting to begin a new transaction when one is already running results
3264          * in MediaWiki issuing a brief warning and doing an implicit commit. All
3265          * atomic levels *must* be explicitly closed using DatabaseBase::endAtomic(),
3266          * and any database transactions cannot be began or committed until all atomic
3267          * levels are closed. There is no such thing as implicitly opening or closing
3268          * an atomic section.
3269          *
3270          * @since 1.23
3271          * @param string $fname
3272          * @throws DBError
3273          */
3274         final public function startAtomic( $fname = __METHOD__ ) {
3275                 if ( !$this->mTrxLevel ) {
3276                         $this->begin( $fname );
3277                         $this->mTrxAutomatic = true;
3278                         $this->mTrxAutomaticAtomic = true;
3279                 }
3280
3281                 $this->mTrxAtomicLevels->push( $fname );
3282         }
3283
3284         /**
3285          * Ends an atomic section of SQL statements
3286          *
3287          * Ends the next section of atomic SQL statements and commits the transaction
3288          * if necessary.
3289          *
3290          * @since 1.23
3291          * @see DatabaseBase::startAtomic
3292          * @param string $fname
3293          * @throws DBError
3294          */
3295         final public function endAtomic( $fname = __METHOD__ ) {
3296                 if ( !$this->mTrxLevel ) {
3297                         throw new DBUnexpectedError( $this, 'No atomic transaction is open.' );
3298                 }
3299                 if ( $this->mTrxAtomicLevels->isEmpty() ||
3300                         $this->mTrxAtomicLevels->pop() !== $fname
3301                 ) {
3302                         throw new DBUnexpectedError( $this, 'Invalid atomic section ended.' );
3303                 }
3304
3305                 if ( $this->mTrxAtomicLevels->isEmpty() && $this->mTrxAutomaticAtomic ) {
3306                         $this->commit( $fname, 'flush' );
3307                 }
3308         }
3309
3310         /**
3311          * Begin a transaction. If a transaction is already in progress,
3312          * that transaction will be committed before the new transaction is started.
3313          *
3314          * Note that when the DBO_TRX flag is set (which is usually the case for web
3315          * requests, but not for maintenance scripts), any previous database query
3316          * will have started a transaction automatically.
3317          *
3318          * Nesting of transactions is not supported. Attempts to nest transactions
3319          * will cause a warning, unless the current transaction was started
3320          * automatically because of the DBO_TRX flag.
3321          *
3322          * @param string $fname
3323          * @throws DBError
3324          */
3325         final public function begin( $fname = __METHOD__ ) {
3326                 global $wgDebugDBTransactions;
3327
3328                 if ( $this->mTrxLevel ) { // implicit commit
3329                         if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3330                                 // If the current transaction was an automatic atomic one, then we definitely have
3331                                 // a problem. Same if there is any unclosed atomic level.
3332                                 throw new DBUnexpectedError( $this,
3333                                         "Attempted to start explicit transaction when atomic levels are still open."
3334                                 );
3335                         } elseif ( !$this->mTrxAutomatic ) {
3336                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3337                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3338                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3339                                         " performing implicit commit!";
3340                                 wfWarn( $msg );
3341                                 wfLogDBError( $msg );
3342                         } else {
3343                                 // if the transaction was automatic and has done write operations,
3344                                 // log it if $wgDebugDBTransactions is enabled.
3345                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3346                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3347                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3348                                         );
3349                                 }
3350                         }
3351
3352                         $this->runOnTransactionPreCommitCallbacks();
3353                         $this->doCommit( $fname );
3354                         if ( $this->mTrxDoneWrites ) {
3355                                 Profiler::instance()->getTransactionProfiler()->transactionWritingOut(
3356                                         $this->mServer, $this->mDBname, $this->mTrxShortId );
3357                         }
3358                         $this->runOnTransactionIdleCallbacks();
3359                 }
3360
3361                 # Avoid fatals if close() was called
3362                 if ( !$this->isOpen() ) {
3363                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3364                 }
3365
3366                 $this->doBegin( $fname );
3367                 $this->mTrxTimestamp = microtime( true );
3368                 $this->mTrxFname = $fname;
3369                 $this->mTrxDoneWrites = false;
3370                 $this->mTrxAutomatic = false;
3371                 $this->mTrxAutomaticAtomic = false;
3372                 $this->mTrxAtomicLevels = new SplStack;
3373                 $this->mTrxIdleCallbacks = array();
3374                 $this->mTrxPreCommitCallbacks = array();
3375                 $this->mTrxShortId = wfRandomString( 12 );
3376         }
3377
3378         /**
3379          * Issues the BEGIN command to the database server.
3380          *
3381          * @see DatabaseBase::begin()
3382          * @param string $fname
3383          */
3384         protected function doBegin( $fname ) {
3385                 $this->query( 'BEGIN', $fname );
3386                 $this->mTrxLevel = 1;
3387         }
3388
3389         /**
3390          * Commits a transaction previously started using begin().
3391          * If no transaction is in progress, a warning is issued.
3392          *
3393          * Nesting of transactions is not supported.
3394          *
3395          * @param string $fname
3396          * @param string $flush Flush flag, set to 'flush' to disable warnings about
3397          *   explicitly committing implicit transactions, or calling commit when no
3398          *   transaction is in progress. This will silently break any ongoing
3399          *   explicit transaction. Only set the flush flag if you are sure that it
3400          *   is safe to ignore these warnings in your context.
3401          * @throws DBUnexpectedError
3402          */
3403         final public function commit( $fname = __METHOD__, $flush = '' ) {
3404                 if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3405                         // There are still atomic sections open. This cannot be ignored
3406                         throw new DBUnexpectedError(
3407                                 $this,
3408                                 "Attempted to commit transaction while atomic sections are still open"
3409                         );
3410                 }
3411
3412                 if ( $flush === 'flush' ) {
3413                         if ( !$this->mTrxLevel ) {
3414                                 return; // nothing to do
3415                         } elseif ( !$this->mTrxAutomatic ) {
3416                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3417                         }
3418                 } else {
3419                         if ( !$this->mTrxLevel ) {
3420                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3421                                 return; // nothing to do
3422                         } elseif ( $this->mTrxAutomatic ) {
3423                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3424                         }
3425                 }
3426
3427                 # Avoid fatals if close() was called
3428                 if ( !$this->isOpen() ) {
3429                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3430                 }
3431
3432                 $this->runOnTransactionPreCommitCallbacks();
3433                 $this->doCommit( $fname );
3434                 if ( $this->mTrxDoneWrites ) {
3435                         Profiler::instance()->getTransactionProfiler()->transactionWritingOut(
3436                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
3437                 }
3438                 $this->runOnTransactionIdleCallbacks();
3439         }
3440
3441         /**
3442          * Issues the COMMIT command to the database server.
3443          *
3444          * @see DatabaseBase::commit()
3445          * @param string $fname
3446          */
3447         protected function doCommit( $fname ) {
3448                 if ( $this->mTrxLevel ) {
3449                         $this->query( 'COMMIT', $fname );
3450                         $this->mTrxLevel = 0;
3451                 }
3452         }
3453
3454         /**
3455          * Rollback a transaction previously started using begin().
3456          * If no transaction is in progress, a warning is issued.
3457          *
3458          * No-op on non-transactional databases.
3459          *
3460          * @param string $fname
3461          * @param string $flush Flush flag, set to 'flush' to disable warnings about
3462          *   calling rollback when no transaction is in progress. This will silently
3463          *   break any ongoing explicit transaction. Only set the flush flag if you
3464          *   are sure that it is safe to ignore these warnings in your context.
3465          * @since 1.23 Added $flush parameter
3466          */
3467         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3468                 if ( $flush !== 'flush' ) {
3469                         if ( !$this->mTrxLevel ) {
3470                                 wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3471                                 return; // nothing to do
3472                         } elseif ( $this->mTrxAutomatic ) {
3473                                 wfWarn( "$fname: Explicit rollback of implicit transaction. Something may be out of sync!" );
3474                         }
3475                 } else {
3476                         if ( !$this->mTrxLevel ) {
3477                                 return; // nothing to do
3478                         } elseif ( !$this->mTrxAutomatic ) {
3479                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3480                         }
3481                 }
3482
3483                 # Avoid fatals if close() was called
3484                 if ( !$this->isOpen() ) {
3485                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3486                 }
3487
3488                 $this->doRollback( $fname );
3489                 $this->mTrxIdleCallbacks = array(); // cancel
3490                 $this->mTrxPreCommitCallbacks = array(); // cancel
3491                 $this->mTrxAtomicLevels = new SplStack;
3492                 if ( $this->mTrxDoneWrites ) {
3493                         Profiler::instance()->getTransactionProfiler()->transactionWritingOut(
3494                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
3495                 }
3496         }
3497
3498         /**
3499          * Issues the ROLLBACK command to the database server.
3500          *
3501          * @see DatabaseBase::rollback()
3502          * @param string $fname
3503          */
3504         protected function doRollback( $fname ) {
3505                 if ( $this->mTrxLevel ) {
3506                         $this->query( 'ROLLBACK', $fname, true );
3507                         $this->mTrxLevel = 0;
3508                 }
3509         }
3510
3511         /**
3512          * Creates a new table with structure copied from existing table
3513          * Note that unlike most database abstraction functions, this function does not
3514          * automatically append database prefix, because it works at a lower
3515          * abstraction level.
3516          * The table names passed to this function shall not be quoted (this
3517          * function calls addIdentifierQuotes when needed).
3518          *
3519          * @param string $oldName Name of table whose structure should be copied
3520          * @param string $newName Name of table to be created
3521          * @param bool $temporary Whether the new table should be temporary
3522          * @param string $fname Calling function name
3523          * @throws MWException
3524          * @return bool True if operation was successful
3525          */
3526         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3527                 $fname = __METHOD__
3528         ) {
3529                 throw new MWException(
3530                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3531         }
3532
3533         /**
3534          * List all tables on the database
3535          *
3536          * @param string $prefix Only show tables with this prefix, e.g. mw_
3537          * @param string $fname Calling function name
3538          * @throws MWException
3539          */
3540         function listTables( $prefix = null, $fname = __METHOD__ ) {
3541                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3542         }
3543
3544         /**
3545          * Reset the views process cache set by listViews()
3546          * @since 1.22
3547          */
3548         final public function clearViewsCache() {
3549                 $this->allViews = null;
3550         }
3551
3552         /**
3553          * Lists all the VIEWs in the database
3554          *
3555          * For caching purposes the list of all views should be stored in
3556          * $this->allViews. The process cache can be cleared with clearViewsCache()
3557          *
3558          * @param string $prefix Only show VIEWs with this prefix, eg. unit_test_
3559          * @param string $fname Name of calling function
3560          * @throws MWException
3561          * @since 1.22
3562          */
3563         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3564                 throw new MWException( 'DatabaseBase::listViews is not implemented in descendant class' );
3565         }
3566
3567         /**
3568          * Differentiates between a TABLE and a VIEW
3569          *
3570          * @param string $name Name of the database-structure to test.
3571          * @throws MWException
3572          * @since 1.22
3573          */
3574         public function isView( $name ) {
3575                 throw new MWException( 'DatabaseBase::isView is not implemented in descendant class' );
3576         }
3577
3578         /**
3579          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3580          * to the format used for inserting into timestamp fields in this DBMS.
3581          *
3582          * The result is unquoted, and needs to be passed through addQuotes()
3583          * before it can be included in raw SQL.
3584          *
3585          * @param string|int $ts
3586          *
3587          * @return string
3588          */
3589         public function timestamp( $ts = 0 ) {
3590                 return wfTimestamp( TS_MW, $ts );
3591         }
3592
3593         /**
3594          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3595          * to the format used for inserting into timestamp fields in this DBMS. If
3596          * NULL is input, it is passed through, allowing NULL values to be inserted
3597          * into timestamp fields.
3598          *
3599          * The result is unquoted, and needs to be passed through addQuotes()
3600          * before it can be included in raw SQL.
3601          *
3602          * @param string|int $ts
3603          *
3604          * @return string
3605          */
3606         public function timestampOrNull( $ts = null ) {
3607                 if ( is_null( $ts ) ) {
3608                         return null;
3609                 } else {
3610                         return $this->timestamp( $ts );
3611                 }
3612         }
3613
3614         /**
3615          * Take the result from a query, and wrap it in a ResultWrapper if
3616          * necessary. Boolean values are passed through as is, to indicate success
3617          * of write queries or failure.
3618          *
3619          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3620          * resource, and it was necessary to call this function to convert it to
3621          * a wrapper. Nowadays, raw database objects are never exposed to external
3622          * callers, so this is unnecessary in external code. For compatibility with
3623          * old code, ResultWrapper objects are passed through unaltered.
3624          *
3625          * @param bool|ResultWrapper|resource $result
3626          * @return bool|ResultWrapper
3627          */
3628         public function resultObject( $result ) {
3629                 if ( empty( $result ) ) {
3630                         return false;
3631                 } elseif ( $result instanceof ResultWrapper ) {
3632                         return $result;
3633                 } elseif ( $result === true ) {
3634                         // Successful write query
3635                         return $result;
3636                 } else {
3637                         return new ResultWrapper( $this, $result );
3638                 }
3639         }
3640
3641         /**
3642          * Ping the server and try to reconnect if it there is no connection
3643          *
3644          * @return bool Success or failure
3645          */
3646         public function ping() {
3647                 # Stub. Not essential to override.
3648                 return true;
3649         }
3650
3651         /**
3652          * Get slave lag. Currently supported only by MySQL.
3653          *
3654          * Note that this function will generate a fatal error on many
3655          * installations. Most callers should use LoadBalancer::safeGetLag()
3656          * instead.
3657          *
3658          * @return int Database replication lag in seconds
3659          */
3660         public function getLag() {
3661                 return 0;
3662         }
3663
3664         /**
3665          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3666          *
3667          * @return int
3668          */
3669         function maxListLen() {
3670                 return 0;
3671         }
3672
3673         /**
3674          * Some DBMSs have a special format for inserting into blob fields, they
3675          * don't allow simple quoted strings to be inserted. To insert into such
3676          * a field, pass the data through this function before passing it to
3677          * DatabaseBase::insert().
3678          *
3679          * @param string $b
3680          * @return string
3681          */
3682         public function encodeBlob( $b ) {
3683                 return $b;
3684         }
3685
3686         /**
3687          * Some DBMSs return a special placeholder object representing blob fields
3688          * in result objects. Pass the object through this function to return the
3689          * original string.
3690          *
3691          * @param string $b
3692          * @return string
3693          */
3694         public function decodeBlob( $b ) {
3695                 return $b;
3696         }
3697
3698         /**
3699          * Override database's default behavior. $options include:
3700          *     'connTimeout' : Set the connection timeout value in seconds.
3701          *                     May be useful for very long batch queries such as
3702          *                     full-wiki dumps, where a single query reads out over
3703          *                     hours or days.
3704          *
3705          * @param array $options
3706          * @return void
3707          */
3708         public function setSessionOptions( array $options ) {
3709         }
3710
3711         /**
3712          * Read and execute SQL commands from a file.
3713          *
3714          * Returns true on success, error string or exception on failure (depending
3715          * on object's error ignore settings).
3716          *
3717          * @param string $filename File name to open
3718          * @param bool|callable $lineCallback Optional function called before reading each line
3719          * @param bool|callable $resultCallback Optional function called for each MySQL result
3720          * @param bool|string $fname Calling function name or false if name should be
3721          *   generated dynamically using $filename
3722          * @param bool|callable $inputCallback Optional function called for each
3723          *   complete line sent
3724          * @throws Exception|MWException
3725          * @return bool|string
3726          */
3727         public function sourceFile(
3728                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3729         ) {
3730                 wfSuppressWarnings();
3731                 $fp = fopen( $filename, 'r' );
3732                 wfRestoreWarnings();
3733
3734                 if ( false === $fp ) {
3735                         throw new MWException( "Could not open \"{$filename}\".\n" );
3736                 }
3737
3738                 if ( !$fname ) {
3739                         $fname = __METHOD__ . "( $filename )";
3740                 }
3741
3742                 try {
3743                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3744                 } catch ( MWException $e ) {
3745                         fclose( $fp );
3746                         throw $e;
3747                 }
3748
3749                 fclose( $fp );
3750
3751                 return $error;
3752         }
3753
3754         /**
3755          * Get the full path of a patch file. Originally based on archive()
3756          * from updaters.inc. Keep in mind this always returns a patch, as
3757          * it fails back to MySQL if no DB-specific patch can be found
3758          *
3759          * @param string $patch The name of the patch, like patch-something.sql
3760          * @return string Full path to patch file
3761          */
3762         public function patchPath( $patch ) {
3763                 global $IP;
3764
3765                 $dbType = $this->getType();
3766                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3767                         return "$IP/maintenance/$dbType/archives/$patch";
3768                 } else {
3769                         return "$IP/maintenance/archives/$patch";
3770                 }
3771         }
3772
3773         /**
3774          * Set variables to be used in sourceFile/sourceStream, in preference to the
3775          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3776          * all. If it's set to false, $GLOBALS will be used.
3777          *
3778          * @param bool|array $vars Mapping variable name to value.
3779          */
3780         public function setSchemaVars( $vars ) {
3781                 $this->mSchemaVars = $vars;
3782         }
3783
3784         /**
3785          * Read and execute commands from an open file handle.
3786          *
3787          * Returns true on success, error string or exception on failure (depending
3788          * on object's error ignore settings).
3789          *
3790          * @param resource $fp File handle
3791          * @param bool|callable $lineCallback Optional function called before reading each query
3792          * @param bool|callable $resultCallback Optional function called for each MySQL result
3793          * @param string $fname Calling function name
3794          * @param bool|callable $inputCallback Optional function called for each complete query sent
3795          * @return bool|string
3796          */
3797         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3798                 $fname = __METHOD__, $inputCallback = false
3799         ) {
3800                 $cmd = '';
3801
3802                 while ( !feof( $fp ) ) {
3803                         if ( $lineCallback ) {
3804                                 call_user_func( $lineCallback );
3805                         }
3806
3807                         $line = trim( fgets( $fp ) );
3808
3809                         if ( $line == '' ) {
3810                                 continue;
3811                         }
3812
3813                         if ( '-' == $line[0] && '-' == $line[1] ) {
3814                                 continue;
3815                         }
3816
3817                         if ( $cmd != '' ) {
3818                                 $cmd .= ' ';
3819                         }
3820
3821                         $done = $this->streamStatementEnd( $cmd, $line );
3822
3823                         $cmd .= "$line\n";
3824
3825                         if ( $done || feof( $fp ) ) {
3826                                 $cmd = $this->replaceVars( $cmd );
3827
3828                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3829                                         $res = $this->query( $cmd, $fname );
3830
3831                                         if ( $resultCallback ) {
3832                                                 call_user_func( $resultCallback, $res, $this );
3833                                         }
3834
3835                                         if ( false === $res ) {
3836                                                 $err = $this->lastError();
3837
3838                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3839                                         }
3840                                 }
3841                                 $cmd = '';
3842                         }
3843                 }
3844
3845                 return true;
3846         }
3847
3848         /**
3849          * Called by sourceStream() to check if we've reached a statement end
3850          *
3851          * @param string $sql SQL assembled so far
3852          * @param string $newLine New line about to be added to $sql
3853          * @return bool Whether $newLine contains end of the statement
3854          */
3855         public function streamStatementEnd( &$sql, &$newLine ) {
3856                 if ( $this->delimiter ) {
3857                         $prev = $newLine;
3858                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3859                         if ( $newLine != $prev ) {
3860                                 return true;
3861                         }
3862                 }
3863
3864                 return false;
3865         }
3866
3867         /**
3868          * Database independent variable replacement. Replaces a set of variables
3869          * in an SQL statement with their contents as given by $this->getSchemaVars().
3870          *
3871          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3872          *
3873          * - '{$var}' should be used for text and is passed through the database's
3874          *   addQuotes method.
3875          * - `{$var}` should be used for identifiers (eg: table and database names),
3876          *   it is passed through the database's addIdentifierQuotes method which
3877          *   can be overridden if the database uses something other than backticks.
3878          * - / *$var* / is just encoded, besides traditional table prefix and
3879          *   table options its use should be avoided.
3880          *
3881          * @param string $ins SQL statement to replace variables in
3882          * @return string The new SQL statement with variables replaced
3883          */
3884         protected function replaceSchemaVars( $ins ) {
3885                 $vars = $this->getSchemaVars();
3886                 foreach ( $vars as $var => $value ) {
3887                         // replace '{$var}'
3888                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3889                         // replace `{$var}`
3890                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3891                         // replace /*$var*/
3892                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3893                 }
3894
3895                 return $ins;
3896         }
3897
3898         /**
3899          * Replace variables in sourced SQL
3900          *
3901          * @param string $ins
3902          * @return string
3903          */
3904         protected function replaceVars( $ins ) {
3905                 $ins = $this->replaceSchemaVars( $ins );
3906
3907                 // Table prefixes
3908                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3909                         array( $this, 'tableNameCallback' ), $ins );
3910
3911                 // Index names
3912                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3913                         array( $this, 'indexNameCallback' ), $ins );
3914
3915                 return $ins;
3916         }
3917
3918         /**
3919          * Get schema variables. If none have been set via setSchemaVars(), then
3920          * use some defaults from the current object.
3921          *
3922          * @return array
3923          */
3924         protected function getSchemaVars() {
3925                 if ( $this->mSchemaVars ) {
3926                         return $this->mSchemaVars;
3927                 } else {
3928                         return $this->getDefaultSchemaVars();
3929                 }
3930         }
3931
3932         /**
3933          * Get schema variables to use if none have been set via setSchemaVars().
3934          *
3935          * Override this in derived classes to provide variables for tables.sql
3936          * and SQL patch files.
3937          *
3938          * @return array
3939          */
3940         protected function getDefaultSchemaVars() {
3941                 return array();
3942         }
3943
3944         /**
3945          * Table name callback
3946          *
3947          * @param array $matches
3948          * @return string
3949          */
3950         protected function tableNameCallback( $matches ) {
3951                 return $this->tableName( $matches[1] );
3952         }
3953
3954         /**
3955          * Index name callback
3956          *
3957          * @param array $matches
3958          * @return string
3959          */
3960         protected function indexNameCallback( $matches ) {
3961                 return $this->indexName( $matches[1] );
3962         }
3963
3964         /**
3965          * Check to see if a named lock is available. This is non-blocking.
3966          *
3967          * @param string $lockName Name of lock to poll
3968          * @param string $method Name of method calling us
3969          * @return bool
3970          * @since 1.20
3971          */
3972         public function lockIsFree( $lockName, $method ) {
3973                 return true;
3974         }
3975
3976         /**
3977          * Acquire a named lock
3978          *
3979          * Abstracted from Filestore::lock() so child classes can implement for
3980          * their own needs.
3981          *
3982          * @param string $lockName Name of lock to aquire
3983          * @param string $method Name of method calling us
3984          * @param int $timeout
3985          * @return bool
3986          */
3987         public function lock( $lockName, $method, $timeout = 5 ) {
3988                 return true;
3989         }
3990
3991         /**
3992          * Release a lock.
3993          *
3994          * @param string $lockName Name of lock to release
3995          * @param string $method Name of method calling us
3996          *
3997          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3998          * by this thread (in which case the lock is not released), and NULL if the named
3999          * lock did not exist
4000          */
4001         public function unlock( $lockName, $method ) {
4002                 return true;
4003         }
4004
4005         /**
4006          * Lock specific tables
4007          *
4008          * @param array $read Array of tables to lock for read access
4009          * @param array $write Array of tables to lock for write access
4010          * @param string $method Name of caller
4011          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
4012          * @return bool
4013          */
4014         public function lockTables( $read, $write, $method, $lowPriority = true ) {
4015                 return true;
4016         }
4017
4018         /**
4019          * Unlock specific tables
4020          *
4021          * @param string $method The caller
4022          * @return bool
4023          */
4024         public function unlockTables( $method ) {
4025                 return true;
4026         }
4027
4028         /**
4029          * Delete a table
4030          * @param string $tableName
4031          * @param string $fName
4032          * @return bool|ResultWrapper
4033          * @since 1.18
4034          */
4035         public function dropTable( $tableName, $fName = __METHOD__ ) {
4036                 if ( !$this->tableExists( $tableName, $fName ) ) {
4037                         return false;
4038                 }
4039                 $sql = "DROP TABLE " . $this->tableName( $tableName );
4040                 if ( $this->cascadingDeletes() ) {
4041                         $sql .= " CASCADE";
4042                 }
4043
4044                 return $this->query( $sql, $fName );
4045         }
4046
4047         /**
4048          * Get search engine class. All subclasses of this need to implement this
4049          * if they wish to use searching.
4050          *
4051          * @return string
4052          */
4053         public function getSearchEngine() {
4054                 return 'SearchEngineDummy';
4055         }
4056
4057         /**
4058          * Find out when 'infinity' is. Most DBMSes support this. This is a special
4059          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
4060          * because "i" sorts after all numbers.
4061          *
4062          * @return string
4063          */
4064         public function getInfinity() {
4065                 return 'infinity';
4066         }
4067
4068         /**
4069          * Encode an expiry time into the DBMS dependent format
4070          *
4071          * @param string $expiry Timestamp for expiry, or the 'infinity' string
4072          * @return string
4073          */
4074         public function encodeExpiry( $expiry ) {
4075                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4076                         ? $this->getInfinity()
4077                         : $this->timestamp( $expiry );
4078         }
4079
4080         /**
4081          * Decode an expiry time into a DBMS independent format
4082          *
4083          * @param string $expiry DB timestamp field value for expiry
4084          * @param int $format TS_* constant, defaults to TS_MW
4085          * @return string
4086          */
4087         public function decodeExpiry( $expiry, $format = TS_MW ) {
4088                 return ( $expiry == '' || $expiry == $this->getInfinity() )
4089                         ? 'infinity'
4090                         : wfTimestamp( $format, $expiry );
4091         }
4092
4093         /**
4094          * Allow or deny "big selects" for this session only. This is done by setting
4095          * the sql_big_selects session variable.
4096          *
4097          * This is a MySQL-specific feature.
4098          *
4099          * @param bool|string $value True for allow, false for deny, or "default" to
4100          *   restore the initial value
4101          */
4102         public function setBigSelects( $value = true ) {
4103                 // no-op
4104         }
4105
4106         /**
4107          * @since 1.19
4108          * @return string
4109          */
4110         public function __toString() {
4111                 return (string)$this->mConn;
4112         }
4113
4114         /**
4115          * Run a few simple sanity checks
4116          */
4117         public function __destruct() {
4118                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
4119                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
4120                 }
4121                 if ( count( $this->mTrxIdleCallbacks ) || count( $this->mTrxPreCommitCallbacks ) ) {
4122                         $callers = array();
4123                         foreach ( $this->mTrxIdleCallbacks as $callbackInfo ) {
4124                                 $callers[] = $callbackInfo[1];
4125                         }
4126                         $callers = implode( ', ', $callers );
4127                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
4128                 }
4129         }
4130 }