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          * Create a log context to pass to wfLogDBError or other logging functions.
 803          *
 804          * @param array $extras Additional data to add to context
 805          * @return array
 806          */
 807         protected function getLogContext( array $extras = array() ) {
 808                 return array_merge(
 809                         array(
 810                                 'db_server' => $this->mServer,
 811                                 'db_name' => $this->mDBname,
 812                                 'db_user' => $this->mUser,
 813                         ),
 814                         $extras
 815                 );
 816         }
 817
 818         /**
 819          * Closes a database connection.
 820          * if it is open : commits any open transactions
 821          *
 822          * @throws MWException
 823          * @return bool Operation success. true if already closed.
 824          */
 825         public function close() {
 826                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 827                         throw new MWException( "Transaction idle callbacks still pending." );
 828                 }
 829                 if ( $this->mConn ) {
 830                         if ( $this->trxLevel() ) {
 831                                 if ( !$this->mTrxAutomatic ) {
 832                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 833                                                 " performing implicit commit before closing connection!" );
 834                                 }
 835
 836                                 $this->commit( __METHOD__, 'flush' );
 837                         }
 838
 839                         $closed = $this->closeConnection();
 840                         $this->mConn = false;
 841                 } else {
 842                         $closed = true;
 843                 }
 844                 $this->mOpened = false;
 845
 846                 return $closed;
 847         }
 848
 849         /**
 850          * Closes underlying database connection
 851          * @since 1.20
 852          * @return bool Whether connection was closed successfully
 853          */
 854         abstract protected function closeConnection();
 855
 856         /**
 857          * @param string $error Fallback error message, used if none is given by DB
 858          * @throws DBConnectionError
 859          */
 860         function reportConnectionError( $error = 'Unknown error' ) {
 861                 $myError = $this->lastError();
 862                 if ( $myError ) {
 863                         $error = $myError;
 864                 }
 865
 866                 # New method
 867                 throw new DBConnectionError( $this, $error );
 868         }
 869
 870         /**
 871          * The DBMS-dependent part of query()
 872          *
 873          * @param string $sql SQL query.
 874          * @return ResultWrapper|bool Result object to feed to fetchObject,
 875          *   fetchRow, ...; or false on failure
 876          */
 877         abstract protected function doQuery( $sql );
 878
 879         /**
 880          * Determine whether a query writes to the DB.
 881          * Should return true if unsure.
 882          *
 883          * @param string $sql
 884          * @return bool
 885          */
 886         public function isWriteQuery( $sql ) {
 887                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 888         }
 889
 890         /**
 891          * Run an SQL query and return the result. Normally throws a DBQueryError
 892          * on failure. If errors are ignored, returns false instead.
 893          *
 894          * In new code, the query wrappers select(), insert(), update(), delete(),
 895          * etc. should be used where possible, since they give much better DBMS
 896          * independence and automatically quote or validate user input in a variety
 897          * of contexts. This function is generally only useful for queries which are
 898          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 899          * as CREATE TABLE.
 900          *
 901          * However, the query wrappers themselves should call this function.
 902          *
 903          * @param string $sql SQL query
 904          * @param string $fname Name of the calling function, for profiling/SHOW PROCESSLIST
 905          *     comment (you can use __METHOD__ or add some extra info)
 906          * @param bool $tempIgnore Whether to avoid throwing an exception on errors...
 907          *     maybe best to catch the exception instead?
 908          * @throws MWException
 909          * @return bool|ResultWrapper True for a successful write query, ResultWrapper object
 910          *     for a successful read query, or false on failure if $tempIgnore set
 911          */
 912         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 913                 global $wgUser, $wgDebugDBTransactions, $wgDebugDumpSqlLength;
 914
 915                 $this->mLastQuery = $sql;
 916                 if ( $this->isWriteQuery( $sql ) ) {
 917                         # Set a flag indicating that writes have been done
 918                         wfDebug( __METHOD__ . ': Writes done: ' . DatabaseBase::generalizeSQL( $sql ) . "\n" );
 919                         $this->mDoneWrites = microtime( true );
 920                 }
 921
 922                 # Add a comment for easy SHOW PROCESSLIST interpretation
 923                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 924                         $userName = $wgUser->getName();
 925                         if ( mb_strlen( $userName ) > 15 ) {
 926                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 927                         }
 928                         $userName = str_replace( '/', '', $userName );
 929                 } else {
 930                         $userName = '';
 931                 }
 932
 933                 // Add trace comment to the begin of the sql string, right after the operator.
 934                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 935                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 936
 937                 # If DBO_TRX is set, start a transaction
 938                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 939                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK'
 940                 ) {
 941                         # Avoid establishing transactions for SHOW and SET statements too -
 942                         # that would delay transaction initializations to once connection
 943                         # is really used by application
 944                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 945                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 946                                 if ( $wgDebugDBTransactions ) {
 947                                         wfDebug( "Implicit transaction start.\n" );
 948                                 }
 949                                 $this->begin( __METHOD__ . " ($fname)" );
 950                                 $this->mTrxAutomatic = true;
 951                         }
 952                 }
 953
 954                 # Keep track of whether the transaction has write queries pending
 955                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
 956                         $this->mTrxDoneWrites = true;
 957                         Profiler::instance()->getTransactionProfiler()->transactionWritingIn(
 958                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
 959                 }
 960
 961                 $queryProf = '';
 962                 $totalProf = '';
 963                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 964
 965                 if ( !Profiler::instance()->isStub() ) {
 966                         # generalizeSQL will probably cut down the query to reasonable
 967                         # logging size most of the time. The substr is really just a sanity check.
 968                         if ( $isMaster ) {
 969                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 970                                 $totalProf = 'DatabaseBase::query-master';
 971                         } else {
 972                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 973                                 $totalProf = 'DatabaseBase::query';
 974                         }
 975                         # Include query transaction state
 976                         $queryProf .= $this->mTrxShortId ? " [TRX#{$this->mTrxShortId}]" : "";
 977
 978                         $trx = $this->mTrxLevel ? 'TRX=yes' : 'TRX=no';
 979                         wfProfileIn( $totalProf );
 980                         wfProfileIn( $queryProf );
 981                 }
 982
 983                 if ( $this->debug() ) {
 984                         static $cnt = 0;
 985
 986                         $cnt++;
 987                         $sqlx = $wgDebugDumpSqlLength ? substr( $commentedSql, 0, $wgDebugDumpSqlLength )
 988                                 : $commentedSql;
 989                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 990
 991                         $master = $isMaster ? 'master' : 'slave';
 992                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 993                 }
 994
 995                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 996
 997                 # Avoid fatals if close() was called
 998                 if ( !$this->isOpen() ) {
 999                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
1000                 }
1001
1002                 # Log the query time and feed it into the DB trx profiler
1003                 $queryStartTime = microtime( true );
1004                 $queryProfile = new ScopedCallback( function() use ( $queryStartTime, $queryProf ) {
1005                         $elapsed = microtime( true ) - $queryStartTime;
1006                         $trxProfiler = Profiler::instance()->getTransactionProfiler();
1007                         $trxProfiler->recordFunctionCompletion( $queryProf, $elapsed );
1008                 } );
1009
1010                 # Do the query and handle errors
1011                 $ret = $this->doQuery( $commentedSql );
1012
1013                 MWDebug::queryTime( $queryId );
1014
1015                 # Try reconnecting if the connection was lost
1016                 if ( false === $ret && $this->wasErrorReissuable() ) {
1017                         # Transaction is gone, like it or not
1018                         $hadTrx = $this->mTrxLevel; // possible lost transaction
1019                         $this->mTrxLevel = 0;
1020                         $this->mTrxIdleCallbacks = array(); // bug 65263
1021                         $this->mTrxPreCommitCallbacks = array(); // bug 65263
1022                         wfDebug( "Connection lost, reconnecting...\n" );
1023                         # Stash the last error values since ping() might clear them
1024                         $lastError = $this->lastError();
1025                         $lastErrno = $this->lastErrno();
1026                         if ( $this->ping() ) {
1027                                 global $wgRequestTime;
1028                                 wfDebug( "Reconnected\n" );
1029                                 $sqlx = $wgDebugDumpSqlLength ? substr( $commentedSql, 0, $wgDebugDumpSqlLength )
1030                                         : $commentedSql;
1031                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
1032                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
1033                                 if ( $elapsed < 300 ) {
1034                                         # Not a database error to lose a transaction after a minute or two
1035                                         wfLogDBError(
1036                                                 "Connection lost and reconnected after {$elapsed}s, query: $sqlx",
1037                                                 $this->getLogContext( array(
1038                                                         'method' => __METHOD__,
1039                                                         'query' => $sqlx,
1040                                                 ) )
1041                                         );
1042                                 }
1043                                 if ( $hadTrx ) {
1044                                         # Leave $ret as false and let an error be reported.
1045                                         # Callers may catch the exception and continue to use the DB.
1046                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname, $tempIgnore );
1047                                 } else {
1048                                         # Should be safe to silently retry (no trx and thus no callbacks)
1049                                         $ret = $this->doQuery( $commentedSql );
1050                                 }
1051                         } else {
1052                                 wfDebug( "Failed\n" );
1053                         }
1054                 }
1055
1056                 if ( false === $ret ) {
1057                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1058                 }
1059
1060                 if ( !Profiler::instance()->isStub() ) {
1061                         wfProfileOut( $queryProf );
1062                         wfProfileOut( $totalProf );
1063                 }
1064
1065                 return $this->resultObject( $ret );
1066         }
1067
1068         /**
1069          * Report a query error. Log the error, and if neither the object ignore
1070          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1071          *
1072          * @param string $error
1073          * @param int $errno
1074          * @param string $sql
1075          * @param string $fname
1076          * @param bool $tempIgnore
1077          * @throws DBQueryError
1078          */
1079         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1080                 # Ignore errors during error handling to avoid infinite recursion
1081                 $ignore = $this->ignoreErrors( true );
1082                 ++$this->mErrorCount;
1083
1084                 if ( $ignore || $tempIgnore ) {
1085                         wfDebug( "SQL ERROR (ignored): $error\n" );
1086                         $this->ignoreErrors( $ignore );
1087                 } else {
1088                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1089                         wfLogDBError(
1090                                 "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1091                                 $this->getLogContext( array(
1092                                         'method' => __METHOD__,
1093                                         'errno' => $errno,
1094                                         'error' => $error,
1095                                         'sql1line' => $sql1line,
1096                                         'fname' => $fname,
1097                                 ) )
1098                         );
1099                         wfDebug( "SQL ERROR: " . $error . "\n" );
1100                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1101                 }
1102         }
1103
1104         /**
1105          * Intended to be compatible with the PEAR::DB wrapper functions.
1106          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1107          *
1108          * ? = scalar value, quoted as necessary
1109          * ! = raw SQL bit (a function for instance)
1110          * & = filename; reads the file and inserts as a blob
1111          *     (we don't use this though...)
1112          *
1113          * @param string $sql
1114          * @param string $func
1115          *
1116          * @return array
1117          */
1118         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1119                 /* MySQL doesn't support prepared statements (yet), so just
1120                  * pack up the query for reference. We'll manually replace
1121                  * the bits later.
1122                  */
1123                 return array( 'query' => $sql, 'func' => $func );
1124         }
1125
1126         /**
1127          * Free a prepared query, generated by prepare().
1128          * @param string $prepared
1129          */
1130         protected function freePrepared( $prepared ) {
1131                 /* No-op by default */
1132         }
1133
1134         /**
1135          * Execute a prepared query with the various arguments
1136          * @param string $prepared The prepared sql
1137          * @param mixed $args Either an array here, or put scalars as varargs
1138          *
1139          * @return ResultWrapper
1140          */
1141         public function execute( $prepared, $args = null ) {
1142                 if ( !is_array( $args ) ) {
1143                         # Pull the var args
1144                         $args = func_get_args();
1145                         array_shift( $args );
1146                 }
1147
1148                 $sql = $this->fillPrepared( $prepared['query'], $args );
1149
1150                 return $this->query( $sql, $prepared['func'] );
1151         }
1152
1153         /**
1154          * For faking prepared SQL statements on DBs that don't support it directly.
1155          *
1156          * @param string $preparedQuery A 'preparable' SQL statement
1157          * @param array $args Array of Arguments to fill it with
1158          * @return string Executable SQL
1159          */
1160         public function fillPrepared( $preparedQuery, $args ) {
1161                 reset( $args );
1162                 $this->preparedArgs =& $args;
1163
1164                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1165                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1166         }
1167
1168         /**
1169          * preg_callback func for fillPrepared()
1170          * The arguments should be in $this->preparedArgs and must not be touched
1171          * while we're doing this.
1172          *
1173          * @param array $matches
1174          * @throws DBUnexpectedError
1175          * @return string
1176          */
1177         protected function fillPreparedArg( $matches ) {
1178                 switch ( $matches[1] ) {
1179                         case '\\?':
1180                                 return '?';
1181                         case '\\!':
1182                                 return '!';
1183                         case '\\&':
1184                                 return '&';
1185                 }
1186
1187                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1188
1189                 switch ( $matches[1] ) {
1190                         case '?':
1191                                 return $this->addQuotes( $arg );
1192                         case '!':
1193                                 return $arg;
1194                         case '&':
1195                                 # return $this->addQuotes( file_get_contents( $arg ) );
1196                                 throw new DBUnexpectedError(
1197                                         $this,
1198                                         '& mode is not implemented. If it\'s really needed, uncomment the line above.'
1199                                 );
1200                         default:
1201                                 throw new DBUnexpectedError(
1202                                         $this,
1203                                         'Received invalid match. This should never happen!'
1204                                 );
1205                 }
1206         }
1207
1208         /**
1209          * Free a result object returned by query() or select(). It's usually not
1210          * necessary to call this, just use unset() or let the variable holding
1211          * the result object go out of scope.
1212          *
1213          * @param mixed $res A SQL result
1214          */
1215         public function freeResult( $res ) {
1216         }
1217
1218         /**
1219          * A SELECT wrapper which returns a single field from a single result row.
1220          *
1221          * Usually throws a DBQueryError on failure. If errors are explicitly
1222          * ignored, returns false on failure.
1223          *
1224          * If no result rows are returned from the query, false is returned.
1225          *
1226          * @param string|array $table Table name. See DatabaseBase::select() for details.
1227          * @param string $var The field name to select. This must be a valid SQL
1228          *   fragment: do not use unvalidated user input.
1229          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1230          * @param string $fname The function name of the caller.
1231          * @param string|array $options The query options. See DatabaseBase::select() for details.
1232          *
1233          * @return bool|mixed The value from the field, or false on failure.
1234          */
1235         public function selectField( $table, $var, $cond = '', $fname = __METHOD__,
1236                 $options = array()
1237         ) {
1238                 if ( !is_array( $options ) ) {
1239                         $options = array( $options );
1240                 }
1241
1242                 $options['LIMIT'] = 1;
1243
1244                 $res = $this->select( $table, $var, $cond, $fname, $options );
1245
1246                 if ( $res === false || !$this->numRows( $res ) ) {
1247                         return false;
1248                 }
1249
1250                 $row = $this->fetchRow( $res );
1251
1252                 if ( $row !== false ) {
1253                         return reset( $row );
1254                 } else {
1255                         return false;
1256                 }
1257         }
1258
1259         /**
1260          * Returns an optional USE INDEX clause to go after the table, and a
1261          * string to go at the end of the query.
1262          *
1263          * @param array $options Associative array of options to be turned into
1264          *   an SQL query, valid keys are listed in the function.
1265          * @return array
1266          * @see DatabaseBase::select()
1267          */
1268         public function makeSelectOptions( $options ) {
1269                 $preLimitTail = $postLimitTail = '';
1270                 $startOpts = '';
1271
1272                 $noKeyOptions = array();
1273
1274                 foreach ( $options as $key => $option ) {
1275                         if ( is_numeric( $key ) ) {
1276                                 $noKeyOptions[$option] = true;
1277                         }
1278                 }
1279
1280                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1281
1282                 $preLimitTail .= $this->makeOrderBy( $options );
1283
1284                 // if (isset($options['LIMIT'])) {
1285                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1286                 //              isset($options['OFFSET']) ? $options['OFFSET']
1287                 //              : false);
1288                 // }
1289
1290                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1291                         $postLimitTail .= ' FOR UPDATE';
1292                 }
1293
1294                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1295                         $postLimitTail .= ' LOCK IN SHARE MODE';
1296                 }
1297
1298                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1299                         $startOpts .= 'DISTINCT';
1300                 }
1301
1302                 # Various MySQL extensions
1303                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1304                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1305                 }
1306
1307                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1308                         $startOpts .= ' HIGH_PRIORITY';
1309                 }
1310
1311                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1312                         $startOpts .= ' SQL_BIG_RESULT';
1313                 }
1314
1315                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1316                         $startOpts .= ' SQL_BUFFER_RESULT';
1317                 }
1318
1319                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1320                         $startOpts .= ' SQL_SMALL_RESULT';
1321                 }
1322
1323                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1324                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1325                 }
1326
1327                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1328                         $startOpts .= ' SQL_CACHE';
1329                 }
1330
1331                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1332                         $startOpts .= ' SQL_NO_CACHE';
1333                 }
1334
1335                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1336                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1337                 } else {
1338                         $useIndex = '';
1339                 }
1340
1341                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1342         }
1343
1344         /**
1345          * Returns an optional GROUP BY with an optional HAVING
1346          *
1347          * @param array $options Associative array of options
1348          * @return string
1349          * @see DatabaseBase::select()
1350          * @since 1.21
1351          */
1352         public function makeGroupByWithHaving( $options ) {
1353                 $sql = '';
1354                 if ( isset( $options['GROUP BY'] ) ) {
1355                         $gb = is_array( $options['GROUP BY'] )
1356                                 ? implode( ',', $options['GROUP BY'] )
1357                                 : $options['GROUP BY'];
1358                         $sql .= ' GROUP BY ' . $gb;
1359                 }
1360                 if ( isset( $options['HAVING'] ) ) {
1361                         $having = is_array( $options['HAVING'] )
1362                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1363                                 : $options['HAVING'];
1364                         $sql .= ' HAVING ' . $having;
1365                 }
1366
1367                 return $sql;
1368         }
1369
1370         /**
1371          * Returns an optional ORDER BY
1372          *
1373          * @param array $options Associative array of options
1374          * @return string
1375          * @see DatabaseBase::select()
1376          * @since 1.21
1377          */
1378         public function makeOrderBy( $options ) {
1379                 if ( isset( $options['ORDER BY'] ) ) {
1380                         $ob = is_array( $options['ORDER BY'] )
1381                                 ? implode( ',', $options['ORDER BY'] )
1382                                 : $options['ORDER BY'];
1383
1384                         return ' ORDER BY ' . $ob;
1385                 }
1386
1387                 return '';
1388         }
1389
1390         /**
1391          * Execute a SELECT query constructed using the various parameters provided.
1392          * See below for full details of the parameters.
1393          *
1394          * @param string|array $table Table name
1395          * @param string|array $vars Field names
1396          * @param string|array $conds Conditions
1397          * @param string $fname Caller function name
1398          * @param array $options Query options
1399          * @param array $join_conds Join conditions
1400          *
1401          *
1402          * @param string|array $table
1403          *
1404          * May be either an array of table names, or a single string holding a table
1405          * name. If an array is given, table aliases can be specified, for example:
1406          *
1407          *    array( 'a' => 'user' )
1408          *
1409          * This includes the user table in the query, with the alias "a" available
1410          * for use in field names (e.g. a.user_name).
1411          *
1412          * All of the table names given here are automatically run through
1413          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1414          * added, and various other table name mappings to be performed.
1415          *
1416          *
1417          * @param string|array $vars
1418          *
1419          * May be either a field name or an array of field names. The field names
1420          * can be complete fragments of SQL, for direct inclusion into the SELECT
1421          * query. If an array is given, field aliases can be specified, for example:
1422          *
1423          *   array( 'maxrev' => 'MAX(rev_id)' )
1424          *
1425          * This includes an expression with the alias "maxrev" in the query.
1426          *
1427          * If an expression is given, care must be taken to ensure that it is
1428          * DBMS-independent.
1429          *
1430          *
1431          * @param string|array $conds
1432          *
1433          * May be either a string containing a single condition, or an array of
1434          * conditions. If an array is given, the conditions constructed from each
1435          * element are combined with AND.
1436          *
1437          * Array elements may take one of two forms:
1438          *
1439          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1440          *   - Elements with a string key are interpreted as equality conditions,
1441          *     where the key is the field name.
1442          *     - If the value of such an array element is a scalar (such as a
1443          *       string), it will be treated as data and thus quoted appropriately.
1444          *       If it is null, an IS NULL clause will be added.
1445          *     - If the value is an array, an IN(...) clause will be constructed,
1446          *       such that the field name may match any of the elements in the
1447          *       array. The elements of the array will be quoted.
1448          *
1449          * Note that expressions are often DBMS-dependent in their syntax.
1450          * DBMS-independent wrappers are provided for constructing several types of
1451          * expression commonly used in condition queries. See:
1452          *    - DatabaseBase::buildLike()
1453          *    - DatabaseBase::conditional()
1454          *
1455          *
1456          * @param string|array $options
1457          *
1458          * Optional: Array of query options. Boolean options are specified by
1459          * including them in the array as a string value with a numeric key, for
1460          * example:
1461          *
1462          *    array( 'FOR UPDATE' )
1463          *
1464          * The supported options are:
1465          *
1466          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1467          *     with LIMIT can theoretically be used for paging through a result set,
1468          *     but this is discouraged in MediaWiki for performance reasons.
1469          *
1470          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1471          *     and then the first rows are taken until the limit is reached. LIMIT
1472          *     is applied to a result set after OFFSET.
1473          *
1474          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1475          *     changed until the next COMMIT.
1476          *
1477          *   - DISTINCT: Boolean: return only unique result rows.
1478          *
1479          *   - GROUP BY: May be either an SQL fragment string naming a field or
1480          *     expression to group by, or an array of such SQL fragments.
1481          *
1482          *   - HAVING: May be either an string containing a HAVING clause or an array of
1483          *     conditions building the HAVING clause. If an array is given, the conditions
1484          *     constructed from each element are combined with AND.
1485          *
1486          *   - ORDER BY: May be either an SQL fragment giving a field name or
1487          *     expression to order by, or an array of such SQL fragments.
1488          *
1489          *   - USE INDEX: This may be either a string giving the index name to use
1490          *     for the query, or an array. If it is an associative array, each key
1491          *     gives the table name (or alias), each value gives the index name to
1492          *     use for that table. All strings are SQL fragments and so should be
1493          *     validated by the caller.
1494          *
1495          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1496          *     instead of SELECT.
1497          *
1498          * And also the following boolean MySQL extensions, see the MySQL manual
1499          * for documentation:
1500          *
1501          *    - LOCK IN SHARE MODE
1502          *    - STRAIGHT_JOIN
1503          *    - HIGH_PRIORITY
1504          *    - SQL_BIG_RESULT
1505          *    - SQL_BUFFER_RESULT
1506          *    - SQL_SMALL_RESULT
1507          *    - SQL_CALC_FOUND_ROWS
1508          *    - SQL_CACHE
1509          *    - SQL_NO_CACHE
1510          *
1511          *
1512          * @param string|array $join_conds
1513          *
1514          * Optional associative array of table-specific join conditions. In the
1515          * most common case, this is unnecessary, since the join condition can be
1516          * in $conds. However, it is useful for doing a LEFT JOIN.
1517          *
1518          * The key of the array contains the table name or alias. The value is an
1519          * array with two elements, numbered 0 and 1. The first gives the type of
1520          * join, the second is an SQL fragment giving the join condition for that
1521          * table. For example:
1522          *
1523          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1524          *
1525          * @return ResultWrapper|bool If the query returned no rows, a ResultWrapper
1526          *   with no rows in it will be returned. If there was a query error, a
1527          *   DBQueryError exception will be thrown, except if the "ignore errors"
1528          *   option was set, in which case false will be returned.
1529          */
1530         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1531                 $options = array(), $join_conds = array() ) {
1532                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1533
1534                 return $this->query( $sql, $fname );
1535         }
1536
1537         /**
1538          * The equivalent of DatabaseBase::select() except that the constructed SQL
1539          * is returned, instead of being immediately executed. This can be useful for
1540          * doing UNION queries, where the SQL text of each query is needed. In general,
1541          * however, callers outside of Database classes should just use select().
1542          *
1543          * @param string|array $table Table name
1544          * @param string|array $vars Field names
1545          * @param string|array $conds Conditions
1546          * @param string $fname Caller function name
1547          * @param string|array $options Query options
1548          * @param string|array $join_conds Join conditions
1549          *
1550          * @return string SQL query string.
1551          * @see DatabaseBase::select()
1552          */
1553         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1554                 $options = array(), $join_conds = array()
1555         ) {
1556                 if ( is_array( $vars ) ) {
1557                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1558                 }
1559
1560                 $options = (array)$options;
1561                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1562                         ? $options['USE INDEX']
1563                         : array();
1564
1565                 if ( is_array( $table ) ) {
1566                         $from = ' FROM ' .
1567                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1568                 } elseif ( $table != '' ) {
1569                         if ( $table[0] == ' ' ) {
1570                                 $from = ' FROM ' . $table;
1571                         } else {
1572                                 $from = ' FROM ' .
1573                                         $this->tableNamesWithUseIndexOrJOIN( array( $table ), $useIndexes, array() );
1574                         }
1575                 } else {
1576                         $from = '';
1577                 }
1578
1579                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1580                         $this->makeSelectOptions( $options );
1581
1582                 if ( !empty( $conds ) ) {
1583                         if ( is_array( $conds ) ) {
1584                                 $conds = $this->makeList( $conds, LIST_AND );
1585                         }
1586                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1587                 } else {
1588                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1589                 }
1590
1591                 if ( isset( $options['LIMIT'] ) ) {
1592                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1593                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1594                 }
1595                 $sql = "$sql $postLimitTail";
1596
1597                 if ( isset( $options['EXPLAIN'] ) ) {
1598                         $sql = 'EXPLAIN ' . $sql;
1599                 }
1600
1601                 return $sql;
1602         }
1603
1604         /**
1605          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1606          * that a single row object is returned. If the query returns no rows,
1607          * false is returned.
1608          *
1609          * @param string|array $table Table name
1610          * @param string|array $vars Field names
1611          * @param array $conds Conditions
1612          * @param string $fname Caller function name
1613          * @param string|array $options Query options
1614          * @param array|string $join_conds Join conditions
1615          *
1616          * @return stdClass|bool
1617          */
1618         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1619                 $options = array(), $join_conds = array()
1620         ) {
1621                 $options = (array)$options;
1622                 $options['LIMIT'] = 1;
1623                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1624
1625                 if ( $res === false ) {
1626                         return false;
1627                 }
1628
1629                 if ( !$this->numRows( $res ) ) {
1630                         return false;
1631                 }
1632
1633                 $obj = $this->fetchObject( $res );
1634
1635                 return $obj;
1636         }
1637
1638         /**
1639          * Estimate the number of rows in dataset
1640          *
1641          * MySQL allows you to estimate the number of rows that would be returned
1642          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1643          * index cardinality statistics, and is notoriously inaccurate, especially
1644          * when large numbers of rows have recently been added or deleted.
1645          *
1646          * For DBMSs that don't support fast result size estimation, this function
1647          * will actually perform the SELECT COUNT(*).
1648          *
1649          * Takes the same arguments as DatabaseBase::select().
1650          *
1651          * @param string $table Table name
1652          * @param string $vars Unused
1653          * @param array|string $conds Filters on the table
1654          * @param string $fname Function name for profiling
1655          * @param array $options Options for select
1656          * @return int Row count
1657          */
1658         public function estimateRowCount(
1659                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = array()
1660         ) {
1661                 $rows = 0;
1662                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1663
1664                 if ( $res ) {
1665                         $row = $this->fetchRow( $res );
1666                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1667                 }
1668
1669                 return $rows;
1670         }
1671
1672         /**
1673          * Get the number of rows in dataset
1674          *
1675          * This is useful when trying to do COUNT(*) but with a LIMIT for performance.
1676          *
1677          * Takes the same arguments as DatabaseBase::select().
1678          *
1679          * @param string $table Table name
1680          * @param string $vars Unused
1681          * @param array|string $conds Filters on the table
1682          * @param string $fname Function name for profiling
1683          * @param array $options Options for select
1684          * @return int Row count
1685          * @since 1.24
1686          */
1687         public function selectRowCount(
1688                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = array()
1689         ) {
1690                 $rows = 0;
1691                 $sql = $this->selectSQLText( $table, '1', $conds, $fname, $options );
1692                 $res = $this->query( "SELECT COUNT(*) AS rowcount FROM ($sql) tmp_count" );
1693
1694                 if ( $res ) {
1695                         $row = $this->fetchRow( $res );
1696                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1697                 }
1698
1699                 return $rows;
1700         }
1701
1702         /**
1703          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1704          * It's only slightly flawed. Don't use for anything important.
1705          *
1706          * @param string $sql A SQL Query
1707          *
1708          * @return string
1709          */
1710         static function generalizeSQL( $sql ) {
1711                 # This does the same as the regexp below would do, but in such a way
1712                 # as to avoid crashing php on some large strings.
1713                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1714
1715                 $sql = str_replace( "\\\\", '', $sql );
1716                 $sql = str_replace( "\\'", '', $sql );
1717                 $sql = str_replace( "\\\"", '', $sql );
1718                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1719                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1720
1721                 # All newlines, tabs, etc replaced by single space
1722                 $sql = preg_replace( '/\s+/', ' ', $sql );
1723
1724                 # All numbers => N,
1725                 # except the ones surrounded by characters, e.g. l10n
1726                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1727                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1728
1729                 return $sql;
1730         }
1731
1732         /**
1733          * Determines whether a field exists in a table
1734          *
1735          * @param string $table Table name
1736          * @param string $field Filed to check on that table
1737          * @param string $fname Calling function name (optional)
1738          * @return bool Whether $table has filed $field
1739          */
1740         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1741                 $info = $this->fieldInfo( $table, $field );
1742
1743                 return (bool)$info;
1744         }
1745
1746         /**
1747          * Determines whether an index exists
1748          * Usually throws a DBQueryError on failure
1749          * If errors are explicitly ignored, returns NULL on failure
1750          *
1751          * @param string $table
1752          * @param string $index
1753          * @param string $fname
1754          * @return bool|null
1755          */
1756         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1757                 if ( !$this->tableExists( $table ) ) {
1758                         return null;
1759                 }
1760
1761                 $info = $this->indexInfo( $table, $index, $fname );
1762                 if ( is_null( $info ) ) {
1763                         return null;
1764                 } else {
1765                         return $info !== false;
1766                 }
1767         }
1768
1769         /**
1770          * Query whether a given table exists
1771          *
1772          * @param string $table
1773          * @param string $fname
1774          * @return bool
1775          */
1776         public function tableExists( $table, $fname = __METHOD__ ) {
1777                 $table = $this->tableName( $table );
1778                 $old = $this->ignoreErrors( true );
1779                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1780                 $this->ignoreErrors( $old );
1781
1782                 return (bool)$res;
1783         }
1784
1785         /**
1786          * Determines if a given index is unique
1787          *
1788          * @param string $table
1789          * @param string $index
1790          *
1791          * @return bool
1792          */
1793         public function indexUnique( $table, $index ) {
1794                 $indexInfo = $this->indexInfo( $table, $index );
1795
1796                 if ( !$indexInfo ) {
1797                         return null;
1798                 }
1799
1800                 return !$indexInfo[0]->Non_unique;
1801         }
1802
1803         /**
1804          * Helper for DatabaseBase::insert().
1805          *
1806          * @param array $options
1807          * @return string
1808          */
1809         protected function makeInsertOptions( $options ) {
1810                 return implode( ' ', $options );
1811         }
1812
1813         /**
1814          * INSERT wrapper, inserts an array into a table.
1815          *
1816          * $a may be either:
1817          *
1818          *   - A single associative array. The array keys are the field names, and
1819          *     the values are the values to insert. The values are treated as data
1820          *     and will be quoted appropriately. If NULL is inserted, this will be
1821          *     converted to a database NULL.
1822          *   - An array with numeric keys, holding a list of associative arrays.
1823          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1824          *     each subarray must be identical to each other, and in the same order.
1825          *
1826          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1827          * returns success.
1828          *
1829          * $options is an array of options, with boolean options encoded as values
1830          * with numeric keys, in the same style as $options in
1831          * DatabaseBase::select(). Supported options are:
1832          *
1833          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1834          *     any rows which cause duplicate key errors are not inserted. It's
1835          *     possible to determine how many rows were successfully inserted using
1836          *     DatabaseBase::affectedRows().
1837          *
1838          * @param string $table Table name. This will be passed through
1839          *   DatabaseBase::tableName().
1840          * @param array $a Array of rows to insert
1841          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1842          * @param array $options Array of options
1843          *
1844          * @return bool
1845          */
1846         public function insert( $table, $a, $fname = __METHOD__, $options = array() ) {
1847                 # No rows to insert, easy just return now
1848                 if ( !count( $a ) ) {
1849                         return true;
1850                 }
1851
1852                 $table = $this->tableName( $table );
1853
1854                 if ( !is_array( $options ) ) {
1855                         $options = array( $options );
1856                 }
1857
1858                 $fh = null;
1859                 if ( isset( $options['fileHandle'] ) ) {
1860                         $fh = $options['fileHandle'];
1861                 }
1862                 $options = $this->makeInsertOptions( $options );
1863
1864                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1865                         $multi = true;
1866                         $keys = array_keys( $a[0] );
1867                 } else {
1868                         $multi = false;
1869                         $keys = array_keys( $a );
1870                 }
1871
1872                 $sql = 'INSERT ' . $options .
1873                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1874
1875                 if ( $multi ) {
1876                         $first = true;
1877                         foreach ( $a as $row ) {
1878                                 if ( $first ) {
1879                                         $first = false;
1880                                 } else {
1881                                         $sql .= ',';
1882                                 }
1883                                 $sql .= '(' . $this->makeList( $row ) . ')';
1884                         }
1885                 } else {
1886                         $sql .= '(' . $this->makeList( $a ) . ')';
1887                 }
1888
1889                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1890                         return false;
1891                 } elseif ( $fh !== null ) {
1892                         return true;
1893                 }
1894
1895                 return (bool)$this->query( $sql, $fname );
1896         }
1897
1898         /**
1899          * Make UPDATE options array for DatabaseBase::makeUpdateOptions
1900          *
1901          * @param array $options
1902          * @return array
1903          */
1904         protected function makeUpdateOptionsArray( $options ) {
1905                 if ( !is_array( $options ) ) {
1906                         $options = array( $options );
1907                 }
1908
1909                 $opts = array();
1910
1911                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1912                         $opts[] = $this->lowPriorityOption();
1913                 }
1914
1915                 if ( in_array( 'IGNORE', $options ) ) {
1916                         $opts[] = 'IGNORE';
1917                 }
1918
1919                 return $opts;
1920         }
1921
1922         /**
1923          * Make UPDATE options for the DatabaseBase::update function
1924          *
1925          * @param array $options The options passed to DatabaseBase::update
1926          * @return string
1927          */
1928         protected function makeUpdateOptions( $options ) {
1929                 $opts = $this->makeUpdateOptionsArray( $options );
1930
1931                 return implode( ' ', $opts );
1932         }
1933
1934         /**
1935          * UPDATE wrapper. Takes a condition array and a SET array.
1936          *
1937          * @param string $table Name of the table to UPDATE. This will be passed through
1938          *   DatabaseBase::tableName().
1939          * @param array $values An array of values to SET. For each array element,
1940          *   the key gives the field name, and the value gives the data to set
1941          *   that field to. The data will be quoted by DatabaseBase::addQuotes().
1942          * @param array $conds An array of conditions (WHERE). See
1943          *   DatabaseBase::select() for the details of the format of condition
1944          *   arrays. Use '*' to update all rows.
1945          * @param string $fname The function name of the caller (from __METHOD__),
1946          *   for logging and profiling.
1947          * @param array $options An array of UPDATE options, can be:
1948          *   - IGNORE: Ignore unique key conflicts
1949          *   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1950          * @return bool
1951          */
1952         function update( $table, $values, $conds, $fname = __METHOD__, $options = array() ) {
1953                 $table = $this->tableName( $table );
1954                 $opts = $this->makeUpdateOptions( $options );
1955                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1956
1957                 if ( $conds !== array() && $conds !== '*' ) {
1958                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1959                 }
1960
1961                 return $this->query( $sql, $fname );
1962         }
1963
1964         /**
1965          * Makes an encoded list of strings from an array
1966          *
1967          * @param array $a Containing the data
1968          * @param int $mode Constant
1969          *    - LIST_COMMA: Comma separated, no field names
1970          *    - LIST_AND:   ANDed WHERE clause (without the WHERE). See the
1971          *      documentation for $conds in DatabaseBase::select().
1972          *    - LIST_OR:    ORed WHERE clause (without the WHERE)
1973          *    - LIST_SET:   Comma separated with field names, like a SET clause
1974          *    - LIST_NAMES: Comma separated field names
1975          * @throws MWException|DBUnexpectedError
1976          * @return string
1977          */
1978         public function makeList( $a, $mode = LIST_COMMA ) {
1979                 if ( !is_array( $a ) ) {
1980                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1981                 }
1982
1983                 $first = true;
1984                 $list = '';
1985
1986                 foreach ( $a as $field => $value ) {
1987                         if ( !$first ) {
1988                                 if ( $mode == LIST_AND ) {
1989                                         $list .= ' AND ';
1990                                 } elseif ( $mode == LIST_OR ) {
1991                                         $list .= ' OR ';
1992                                 } else {
1993                                         $list .= ',';
1994                                 }
1995                         } else {
1996                                 $first = false;
1997                         }
1998
1999                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
2000                                 $list .= "($value)";
2001                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
2002                                 $list .= "$value";
2003                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
2004                                 if ( count( $value ) == 0 ) {
2005                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
2006                                 } elseif ( count( $value ) == 1 ) {
2007                                         // Special-case single values, as IN isn't terribly efficient
2008                                         // Don't necessarily assume the single key is 0; we don't
2009                                         // enforce linear numeric ordering on other arrays here.
2010                                         $value = array_values( $value );
2011                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
2012                                 } else {
2013                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
2014                                 }
2015                         } elseif ( $value === null ) {
2016                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
2017                                         $list .= "$field IS ";
2018                                 } elseif ( $mode == LIST_SET ) {
2019                                         $list .= "$field = ";
2020                                 }
2021                                 $list .= 'NULL';
2022                         } else {
2023                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
2024                                         $list .= "$field = ";
2025                                 }
2026                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
2027                         }
2028                 }
2029
2030                 return $list;
2031         }
2032
2033         /**
2034          * Build a partial where clause from a 2-d array such as used for LinkBatch.
2035          * The keys on each level may be either integers or strings.
2036          *
2037          * @param array $data Organized as 2-d
2038          *    array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
2039          * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
2040          * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
2041          * @return string|bool SQL fragment, or false if no items in array
2042          */
2043         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2044                 $conds = array();
2045
2046                 foreach ( $data as $base => $sub ) {
2047                         if ( count( $sub ) ) {
2048                                 $conds[] = $this->makeList(
2049                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
2050                                         LIST_AND );
2051                         }
2052                 }
2053
2054                 if ( $conds ) {
2055                         return $this->makeList( $conds, LIST_OR );
2056                 } else {
2057                         // Nothing to search for...
2058                         return false;
2059                 }
2060         }
2061
2062         /**
2063          * Return aggregated value alias
2064          *
2065          * @param array $valuedata
2066          * @param string $valuename
2067          *
2068          * @return string
2069          */
2070         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2071                 return $valuename;
2072         }
2073
2074         /**
2075          * @param string $field
2076          * @return string
2077          */
2078         public function bitNot( $field ) {
2079                 return "(~$field)";
2080         }
2081
2082         /**
2083          * @param string $fieldLeft
2084          * @param string $fieldRight
2085          * @return string
2086          */
2087         public function bitAnd( $fieldLeft, $fieldRight ) {
2088                 return "($fieldLeft & $fieldRight)";
2089         }
2090
2091         /**
2092          * @param string $fieldLeft
2093          * @param string $fieldRight
2094          * @return string
2095          */
2096         public function bitOr( $fieldLeft, $fieldRight ) {
2097                 return "($fieldLeft | $fieldRight)";
2098         }
2099
2100         /**
2101          * Build a concatenation list to feed into a SQL query
2102          * @param array $stringList List of raw SQL expressions; caller is
2103          *   responsible for any quoting
2104          * @return string
2105          */
2106         public function buildConcat( $stringList ) {
2107                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2108         }
2109
2110         /**
2111          * Build a GROUP_CONCAT or equivalent statement for a query.
2112          *
2113          * This is useful for combining a field for several rows into a single string.
2114          * NULL values will not appear in the output, duplicated values will appear,
2115          * and the resulting delimiter-separated values have no defined sort order.
2116          * Code using the results may need to use the PHP unique() or sort() methods.
2117          *
2118          * @param string $delim Glue to bind the results together
2119          * @param string|array $table Table name
2120          * @param string $field Field name
2121          * @param string|array $conds Conditions
2122          * @param string|array $join_conds Join conditions
2123          * @return string SQL text
2124          * @since 1.23
2125          */
2126         public function buildGroupConcatField(
2127                 $delim, $table, $field, $conds = '', $join_conds = array()
2128         ) {
2129                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
2130
2131                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, array(), $join_conds ) . ')';
2132         }
2133
2134         /**
2135          * Change the current database
2136          *
2137          * @todo Explain what exactly will fail if this is not overridden.
2138          *
2139          * @param string $db
2140          *
2141          * @return bool Success or failure
2142          */
2143         public function selectDB( $db ) {
2144                 # Stub. Shouldn't cause serious problems if it's not overridden, but
2145                 # if your database engine supports a concept similar to MySQL's
2146                 # databases you may as well.
2147                 $this->mDBname = $db;
2148
2149                 return true;
2150         }
2151
2152         /**
2153          * Get the current DB name
2154          * @return string
2155          */
2156         public function getDBname() {
2157                 return $this->mDBname;
2158         }
2159
2160         /**
2161          * Get the server hostname or IP address
2162          * @return string
2163          */
2164         public function getServer() {
2165                 return $this->mServer;
2166         }
2167
2168         /**
2169          * Format a table name ready for use in constructing an SQL query
2170          *
2171          * This does two important things: it quotes the table names to clean them up,
2172          * and it adds a table prefix if only given a table name with no quotes.
2173          *
2174          * All functions of this object which require a table name call this function
2175          * themselves. Pass the canonical name to such functions. This is only needed
2176          * when calling query() directly.
2177          *
2178          * @param string $name Database table name
2179          * @param string $format One of:
2180          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2181          *            so that it can be used in a query.
2182          *   raw - Do not add identifier quotes to the table name
2183          * @return string Full database name
2184          */
2185         public function tableName( $name, $format = 'quoted' ) {
2186                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables, $wgSharedSchema;
2187                 # Skip the entire process when we have a string quoted on both ends.
2188                 # Note that we check the end so that we will still quote any use of
2189                 # use of `database`.table. But won't break things if someone wants
2190                 # to query a database table with a dot in the name.
2191                 if ( $this->isQuotedIdentifier( $name ) ) {
2192                         return $name;
2193                 }
2194
2195                 # Lets test for any bits of text that should never show up in a table
2196                 # name. Basically anything like JOIN or ON which are actually part of
2197                 # SQL queries, but may end up inside of the table value to combine
2198                 # sql. Such as how the API is doing.
2199                 # Note that we use a whitespace test rather than a \b test to avoid
2200                 # any remote case where a word like on may be inside of a table name
2201                 # surrounded by symbols which may be considered word breaks.
2202                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2203                         return $name;
2204                 }
2205
2206                 # Split database and table into proper variables.
2207                 # We reverse the explode so that database.table and table both output
2208                 # the correct table.
2209                 $dbDetails = explode( '.', $name, 3 );
2210                 if ( count( $dbDetails ) == 3 ) {
2211                         list( $database, $schema, $table ) = $dbDetails;
2212                         # We don't want any prefix added in this case
2213                         $prefix = '';
2214                 } elseif ( count( $dbDetails ) == 2 ) {
2215                         list( $database, $table ) = $dbDetails;
2216                         # We don't want any prefix added in this case
2217                         # In dbs that support it, $database may actually be the schema
2218                         # but that doesn't affect any of the functionality here
2219                         $prefix = '';
2220                         $schema = null;
2221                 } else {
2222                         list( $table ) = $dbDetails;
2223                         if ( $wgSharedDB !== null # We have a shared database
2224                                 && $this->mForeign == false # We're not working on a foreign database
2225                                 && !$this->isQuotedIdentifier( $table ) # Prevent shared tables listing '`table`'
2226                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2227                         ) {
2228                                 $database = $wgSharedDB;
2229                                 $schema = $wgSharedSchema === null ? $this->mSchema : $wgSharedSchema;
2230                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2231                         } else {
2232                                 $database = null;
2233                                 $schema = $this->mSchema; # Default schema
2234                                 $prefix = $this->mTablePrefix; # Default prefix
2235                         }
2236                 }
2237
2238                 # Quote $table and apply the prefix if not quoted.
2239                 # $tableName might be empty if this is called from Database::replaceVars()
2240                 $tableName = "{$prefix}{$table}";
2241                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) && $tableName !== '' ) {
2242                         $tableName = $this->addIdentifierQuotes( $tableName );
2243                 }
2244
2245                 # Quote $schema and merge it with the table name if needed
2246                 if ( $schema !== null ) {
2247                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $schema ) ) {
2248                                 $schema = $this->addIdentifierQuotes( $schema );
2249                         }
2250                         $tableName = $schema . '.' . $tableName;
2251                 }
2252
2253                 # Quote $database and merge it with the table name if needed
2254                 if ( $database !== null ) {
2255                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2256                                 $database = $this->addIdentifierQuotes( $database );
2257                         }
2258                         $tableName = $database . '.' . $tableName;
2259                 }
2260
2261                 return $tableName;
2262         }
2263
2264         /**
2265          * Fetch a number of table names into an array
2266          * This is handy when you need to construct SQL for joins
2267          *
2268          * Example:
2269          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2270          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2271          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2272          *
2273          * @return array
2274          */
2275         public function tableNames() {
2276                 $inArray = func_get_args();
2277                 $retVal = array();
2278
2279                 foreach ( $inArray as $name ) {
2280                         $retVal[$name] = $this->tableName( $name );
2281                 }
2282
2283                 return $retVal;
2284         }
2285
2286         /**
2287          * Fetch a number of table names into an zero-indexed numerical array
2288          * This is handy when you need to construct SQL for joins
2289          *
2290          * Example:
2291          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2292          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2293          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2294          *
2295          * @return array
2296          */
2297         public function tableNamesN() {
2298                 $inArray = func_get_args();
2299                 $retVal = array();
2300
2301                 foreach ( $inArray as $name ) {
2302                         $retVal[] = $this->tableName( $name );
2303                 }
2304
2305                 return $retVal;
2306         }
2307
2308         /**
2309          * Get an aliased table name
2310          * e.g. tableName AS newTableName
2311          *
2312          * @param string $name Table name, see tableName()
2313          * @param string|bool $alias Alias (optional)
2314          * @return string SQL name for aliased table. Will not alias a table to its own name
2315          */
2316         public function tableNameWithAlias( $name, $alias = false ) {
2317                 if ( !$alias || $alias == $name ) {
2318                         return $this->tableName( $name );
2319                 } else {
2320                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2321                 }
2322         }
2323
2324         /**
2325          * Gets an array of aliased table names
2326          *
2327          * @param array $tables Array( [alias] => table )
2328          * @return string[] See tableNameWithAlias()
2329          */
2330         public function tableNamesWithAlias( $tables ) {
2331                 $retval = array();
2332                 foreach ( $tables as $alias => $table ) {
2333                         if ( is_numeric( $alias ) ) {
2334                                 $alias = $table;
2335                         }
2336                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2337                 }
2338
2339                 return $retval;
2340         }
2341
2342         /**
2343          * Get an aliased field name
2344          * e.g. fieldName AS newFieldName
2345          *
2346          * @param string $name Field name
2347          * @param string|bool $alias Alias (optional)
2348          * @return string SQL name for aliased field. Will not alias a field to its own name
2349          */
2350         public function fieldNameWithAlias( $name, $alias = false ) {
2351                 if ( !$alias || (string)$alias === (string)$name ) {
2352                         return $name;
2353                 } else {
2354                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2355                 }
2356         }
2357
2358         /**
2359          * Gets an array of aliased field names
2360          *
2361          * @param array $fields Array( [alias] => field )
2362          * @return string[] See fieldNameWithAlias()
2363          */
2364         public function fieldNamesWithAlias( $fields ) {
2365                 $retval = array();
2366                 foreach ( $fields as $alias => $field ) {
2367                         if ( is_numeric( $alias ) ) {
2368                                 $alias = $field;
2369                         }
2370                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2371                 }
2372
2373                 return $retval;
2374         }
2375
2376         /**
2377          * Get the aliased table name clause for a FROM clause
2378          * which might have a JOIN and/or USE INDEX clause
2379          *
2380          * @param array $tables ( [alias] => table )
2381          * @param array $use_index Same as for select()
2382          * @param array $join_conds Same as for select()
2383          * @return string
2384          */
2385         protected function tableNamesWithUseIndexOrJOIN(
2386                 $tables, $use_index = array(), $join_conds = array()
2387         ) {
2388                 $ret = array();
2389                 $retJOIN = array();
2390                 $use_index = (array)$use_index;
2391                 $join_conds = (array)$join_conds;
2392
2393                 foreach ( $tables as $alias => $table ) {
2394                         if ( !is_string( $alias ) ) {
2395                                 // No alias? Set it equal to the table name
2396                                 $alias = $table;
2397                         }
2398                         // Is there a JOIN clause for this table?
2399                         if ( isset( $join_conds[$alias] ) ) {
2400                                 list( $joinType, $conds ) = $join_conds[$alias];
2401                                 $tableClause = $joinType;
2402                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2403                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2404                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2405                                         if ( $use != '' ) {
2406                                                 $tableClause .= ' ' . $use;
2407                                         }
2408                                 }
2409                                 $on = $this->makeList( (array)$conds, LIST_AND );
2410                                 if ( $on != '' ) {
2411                                         $tableClause .= ' ON (' . $on . ')';
2412                                 }
2413
2414                                 $retJOIN[] = $tableClause;
2415                         } elseif ( isset( $use_index[$alias] ) ) {
2416                                 // Is there an INDEX clause for this table?
2417                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2418                                 $tableClause .= ' ' . $this->useIndexClause(
2419                                         implode( ',', (array)$use_index[$alias] )
2420                                 );
2421
2422                                 $ret[] = $tableClause;
2423                         } else {
2424                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2425
2426                                 $ret[] = $tableClause;
2427                         }
2428                 }
2429
2430                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2431                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2432                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2433
2434                 // Compile our final table clause
2435                 return implode( ' ', array( $implicitJoins, $explicitJoins ) );
2436         }
2437
2438         /**
2439          * Get the name of an index in a given table
2440          *
2441          * @param string $index
2442          * @return string
2443          */
2444         protected function indexName( $index ) {
2445                 // Backwards-compatibility hack
2446                 $renamed = array(
2447                         'ar_usertext_timestamp' => 'usertext_timestamp',
2448                         'un_user_id' => 'user_id',
2449                         'un_user_ip' => 'user_ip',
2450                 );
2451
2452                 if ( isset( $renamed[$index] ) ) {
2453                         return $renamed[$index];
2454                 } else {
2455                         return $index;
2456                 }
2457         }
2458
2459         /**
2460          * Adds quotes and backslashes.
2461          *
2462          * @param string $s
2463          * @return string
2464          */
2465         public function addQuotes( $s ) {
2466                 if ( $s === null ) {
2467                         return 'NULL';
2468                 } else {
2469                         # This will also quote numeric values. This should be harmless,
2470                         # and protects against weird problems that occur when they really
2471                         # _are_ strings such as article titles and string->number->string
2472                         # conversion is not 1:1.
2473                         return "'" . $this->strencode( $s ) . "'";
2474                 }
2475         }
2476
2477         /**
2478          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2479          * MySQL uses `backticks` while basically everything else uses double quotes.
2480          * Since MySQL is the odd one out here the double quotes are our generic
2481          * and we implement backticks in DatabaseMysql.
2482          *
2483          * @param string $s
2484          * @return string
2485          */
2486         public function addIdentifierQuotes( $s ) {
2487                 return '"' . str_replace( '"', '""', $s ) . '"';
2488         }
2489
2490         /**
2491          * Returns if the given identifier looks quoted or not according to
2492          * the database convention for quoting identifiers .
2493          *
2494          * @param string $name
2495          * @return bool
2496          */
2497         public function isQuotedIdentifier( $name ) {
2498                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2499         }
2500
2501         /**
2502          * @param string $s
2503          * @return string
2504          */
2505         protected function escapeLikeInternal( $s ) {
2506                 return addcslashes( $s, '\%_' );
2507         }
2508
2509         /**
2510          * LIKE statement wrapper, receives a variable-length argument list with
2511          * parts of pattern to match containing either string literals that will be
2512          * escaped or tokens returned by anyChar() or anyString(). Alternatively,
2513          * the function could be provided with an array of aforementioned
2514          * parameters.
2515          *
2516          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
2517          * a LIKE clause that searches for subpages of 'My page title'.
2518          * Alternatively:
2519          *   $pattern = array( 'My_page_title/', $dbr->anyString() );
2520          *   $query .= $dbr->buildLike( $pattern );
2521          *
2522          * @since 1.16
2523          * @return string Fully built LIKE statement
2524          */
2525         public function buildLike() {
2526                 $params = func_get_args();
2527
2528                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2529                         $params = $params[0];
2530                 }
2531
2532                 $s = '';
2533
2534                 foreach ( $params as $value ) {
2535                         if ( $value instanceof LikeMatch ) {
2536                                 $s .= $value->toString();
2537                         } else {
2538                                 $s .= $this->escapeLikeInternal( $value );
2539                         }
2540                 }
2541
2542                 return " LIKE {$this->addQuotes( $s )} ";
2543         }
2544
2545         /**
2546          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2547          *
2548          * @return LikeMatch
2549          */
2550         public function anyChar() {
2551                 return new LikeMatch( '_' );
2552         }
2553
2554         /**
2555          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2556          *
2557          * @return LikeMatch
2558          */
2559         public function anyString() {
2560                 return new LikeMatch( '%' );
2561         }
2562
2563         /**
2564          * Returns an appropriately quoted sequence value for inserting a new row.
2565          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2566          * subclass will return an integer, and save the value for insertId()
2567          *
2568          * Any implementation of this function should *not* involve reusing
2569          * sequence numbers created for rolled-back transactions.
2570          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2571          * @param string $seqName
2572          * @return null|int
2573          */
2574         public function nextSequenceValue( $seqName ) {
2575                 return null;
2576         }
2577
2578         /**
2579          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2580          * is only needed because a) MySQL must be as efficient as possible due to
2581          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2582          * which index to pick. Anyway, other databases might have different
2583          * indexes on a given table. So don't bother overriding this unless you're
2584          * MySQL.
2585          * @param string $index
2586          * @return string
2587          */
2588         public function useIndexClause( $index ) {
2589                 return '';
2590         }
2591
2592         /**
2593          * REPLACE query wrapper.
2594          *
2595          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2596          * except that when there is a duplicate key error, the old row is deleted
2597          * and the new row is inserted in its place.
2598          *
2599          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2600          * perform the delete, we need to know what the unique indexes are so that
2601          * we know how to find the conflicting rows.
2602          *
2603          * It may be more efficient to leave off unique indexes which are unlikely
2604          * to collide. However if you do this, you run the risk of encountering
2605          * errors which wouldn't have occurred in MySQL.
2606          *
2607          * @param string $table The table to replace the row(s) in.
2608          * @param array $uniqueIndexes Is an array of indexes. Each element may be either
2609          *    a field name or an array of field names
2610          * @param array $rows Can be either a single row to insert, or multiple rows,
2611          *    in the same format as for DatabaseBase::insert()
2612          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2613          */
2614         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2615                 $quotedTable = $this->tableName( $table );
2616
2617                 if ( count( $rows ) == 0 ) {
2618                         return;
2619                 }
2620
2621                 # Single row case
2622                 if ( !is_array( reset( $rows ) ) ) {
2623                         $rows = array( $rows );
2624                 }
2625
2626                 foreach ( $rows as $row ) {
2627                         # Delete rows which collide
2628                         if ( $uniqueIndexes ) {
2629                                 $sql = "DELETE FROM $quotedTable WHERE ";
2630                                 $first = true;
2631                                 foreach ( $uniqueIndexes as $index ) {
2632                                         if ( $first ) {
2633                                                 $first = false;
2634                                                 $sql .= '( ';
2635                                         } else {
2636                                                 $sql .= ' ) OR ( ';
2637                                         }
2638                                         if ( is_array( $index ) ) {
2639                                                 $first2 = true;
2640                                                 foreach ( $index as $col ) {
2641                                                         if ( $first2 ) {
2642                                                                 $first2 = false;
2643                                                         } else {
2644                                                                 $sql .= ' AND ';
2645                                                         }
2646                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2647                                                 }
2648                                         } else {
2649                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2650                                         }
2651                                 }
2652                                 $sql .= ' )';
2653                                 $this->query( $sql, $fname );
2654                         }
2655
2656                         # Now insert the row
2657                         $this->insert( $table, $row, $fname );
2658                 }
2659         }
2660
2661         /**
2662          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2663          * statement.
2664          *
2665          * @param string $table Table name
2666          * @param array|string $rows Row(s) to insert
2667          * @param string $fname Caller function name
2668          *
2669          * @return ResultWrapper
2670          */
2671         protected function nativeReplace( $table, $rows, $fname ) {
2672                 $table = $this->tableName( $table );
2673
2674                 # Single row case
2675                 if ( !is_array( reset( $rows ) ) ) {
2676                         $rows = array( $rows );
2677                 }
2678
2679                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2680                 $first = true;
2681
2682                 foreach ( $rows as $row ) {
2683                         if ( $first ) {
2684                                 $first = false;
2685                         } else {
2686                                 $sql .= ',';
2687                         }
2688
2689                         $sql .= '(' . $this->makeList( $row ) . ')';
2690                 }
2691
2692                 return $this->query( $sql, $fname );
2693         }
2694
2695         /**
2696          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
2697          *
2698          * This updates any conflicting rows (according to the unique indexes) using
2699          * the provided SET clause and inserts any remaining (non-conflicted) rows.
2700          *
2701          * $rows may be either:
2702          *   - A single associative array. The array keys are the field names, and
2703          *     the values are the values to insert. The values are treated as data
2704          *     and will be quoted appropriately. If NULL is inserted, this will be
2705          *     converted to a database NULL.
2706          *   - An array with numeric keys, holding a list of associative arrays.
2707          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
2708          *     each subarray must be identical to each other, and in the same order.
2709          *
2710          * It may be more efficient to leave off unique indexes which are unlikely
2711          * to collide. However if you do this, you run the risk of encountering
2712          * errors which wouldn't have occurred in MySQL.
2713          *
2714          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
2715          * returns success.
2716          *
2717          * @since 1.22
2718          *
2719          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
2720          * @param array $rows A single row or list of rows to insert
2721          * @param array $uniqueIndexes List of single field names or field name tuples
2722          * @param array $set An array of values to SET. For each array element, the
2723          *   key gives the field name, and the value gives the data to set that
2724          *   field to. The data will be quoted by DatabaseBase::addQuotes().
2725          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2726          * @throws Exception
2727          * @return bool
2728          */
2729         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2730                 $fname = __METHOD__
2731         ) {
2732                 if ( !count( $rows ) ) {
2733                         return true; // nothing to do
2734                 }
2735
2736                 if ( !is_array( reset( $rows ) ) ) {
2737                         $rows = array( $rows );
2738                 }
2739
2740                 if ( count( $uniqueIndexes ) ) {
2741                         $clauses = array(); // list WHERE clauses that each identify a single row
2742                         foreach ( $rows as $row ) {
2743                                 foreach ( $uniqueIndexes as $index ) {
2744                                         $index = is_array( $index ) ? $index : array( $index ); // columns
2745                                         $rowKey = array(); // unique key to this row
2746                                         foreach ( $index as $column ) {
2747                                                 $rowKey[$column] = $row[$column];
2748                                         }
2749                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2750                                 }
2751                         }
2752                         $where = array( $this->makeList( $clauses, LIST_OR ) );
2753                 } else {
2754                         $where = false;
2755                 }
2756
2757                 $useTrx = !$this->mTrxLevel;
2758                 if ( $useTrx ) {
2759                         $this->begin( $fname );
2760                 }
2761                 try {
2762                         # Update any existing conflicting row(s)
2763                         if ( $where !== false ) {
2764                                 $ok = $this->update( $table, $set, $where, $fname );
2765                         } else {
2766                                 $ok = true;
2767                         }
2768                         # Now insert any non-conflicting row(s)
2769                         $ok = $this->insert( $table, $rows, $fname, array( 'IGNORE' ) ) && $ok;
2770                 } catch ( Exception $e ) {
2771                         if ( $useTrx ) {
2772                                 $this->rollback( $fname );
2773                         }
2774                         throw $e;
2775                 }
2776                 if ( $useTrx ) {
2777                         $this->commit( $fname );
2778                 }
2779
2780                 return $ok;
2781         }
2782
2783         /**
2784          * DELETE where the condition is a join.
2785          *
2786          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2787          * we use sub-selects
2788          *
2789          * For safety, an empty $conds will not delete everything. If you want to
2790          * delete all rows where the join condition matches, set $conds='*'.
2791          *
2792          * DO NOT put the join condition in $conds.
2793          *
2794          * @param string $delTable The table to delete from.
2795          * @param string $joinTable The other table.
2796          * @param string $delVar The variable to join on, in the first table.
2797          * @param string $joinVar The variable to join on, in the second table.
2798          * @param array $conds Condition array of field names mapped to variables,
2799          *   ANDed together in the WHERE clause
2800          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2801          * @throws DBUnexpectedError
2802          */
2803         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2804                 $fname = __METHOD__
2805         ) {
2806                 if ( !$conds ) {
2807                         throw new DBUnexpectedError( $this,
2808                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2809                 }
2810
2811                 $delTable = $this->tableName( $delTable );
2812                 $joinTable = $this->tableName( $joinTable );
2813                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2814                 if ( $conds != '*' ) {
2815                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2816                 }
2817                 $sql .= ')';
2818
2819                 $this->query( $sql, $fname );
2820         }
2821
2822         /**
2823          * Returns the size of a text field, or -1 for "unlimited"
2824          *
2825          * @param string $table
2826          * @param string $field
2827          * @return int
2828          */
2829         public function textFieldSize( $table, $field ) {
2830                 $table = $this->tableName( $table );
2831                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2832                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2833                 $row = $this->fetchObject( $res );
2834
2835                 $m = array();
2836
2837                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2838                         $size = $m[1];
2839                 } else {
2840                         $size = -1;
2841                 }
2842
2843                 return $size;
2844         }
2845
2846         /**
2847          * A string to insert into queries to show that they're low-priority, like
2848          * MySQL's LOW_PRIORITY. If no such feature exists, return an empty
2849          * string and nothing bad should happen.
2850          *
2851          * @return string Returns the text of the low priority option if it is
2852          *   supported, or a blank string otherwise
2853          */
2854         public function lowPriorityOption() {
2855                 return '';
2856         }
2857
2858         /**
2859          * DELETE query wrapper.
2860          *
2861          * @param array $table Table name
2862          * @param string|array $conds Array of conditions. See $conds in DatabaseBase::select()
2863          *   for the format. Use $conds == "*" to delete all rows
2864          * @param string $fname Name of the calling function
2865          * @throws DBUnexpectedError
2866          * @return bool|ResultWrapper
2867          */
2868         public function delete( $table, $conds, $fname = __METHOD__ ) {
2869                 if ( !$conds ) {
2870                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2871                 }
2872
2873                 $table = $this->tableName( $table );
2874                 $sql = "DELETE FROM $table";
2875
2876                 if ( $conds != '*' ) {
2877                         if ( is_array( $conds ) ) {
2878                                 $conds = $this->makeList( $conds, LIST_AND );
2879                         }
2880                         $sql .= ' WHERE ' . $conds;
2881                 }
2882
2883                 return $this->query( $sql, $fname );
2884         }
2885
2886         /**
2887          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2888          * into another table.
2889          *
2890          * @param string $destTable The table name to insert into
2891          * @param string|array $srcTable May be either a table name, or an array of table names
2892          *    to include in a join.
2893          *
2894          * @param array $varMap Must be an associative array of the form
2895          *    array( 'dest1' => 'source1', ...). Source items may be literals
2896          *    rather than field names, but strings should be quoted with
2897          *    DatabaseBase::addQuotes()
2898          *
2899          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2900          *    the details of the format of condition arrays. May be "*" to copy the
2901          *    whole table.
2902          *
2903          * @param string $fname The function name of the caller, from __METHOD__
2904          *
2905          * @param array $insertOptions Options for the INSERT part of the query, see
2906          *    DatabaseBase::insert() for details.
2907          * @param array $selectOptions Options for the SELECT part of the query, see
2908          *    DatabaseBase::select() for details.
2909          *
2910          * @return ResultWrapper
2911          */
2912         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2913                 $fname = __METHOD__,
2914                 $insertOptions = array(), $selectOptions = array()
2915         ) {
2916                 $destTable = $this->tableName( $destTable );
2917
2918                 if ( !is_array( $insertOptions ) ) {
2919                         $insertOptions = array( $insertOptions );
2920                 }
2921
2922                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2923
2924                 if ( !is_array( $selectOptions ) ) {
2925                         $selectOptions = array( $selectOptions );
2926                 }
2927
2928                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2929
2930                 if ( is_array( $srcTable ) ) {
2931                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2932                 } else {
2933                         $srcTable = $this->tableName( $srcTable );
2934                 }
2935
2936                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2937                         " SELECT $startOpts " . implode( ',', $varMap ) .
2938                         " FROM $srcTable $useIndex ";
2939
2940                 if ( $conds != '*' ) {
2941                         if ( is_array( $conds ) ) {
2942                                 $conds = $this->makeList( $conds, LIST_AND );
2943                         }
2944                         $sql .= " WHERE $conds";
2945                 }
2946
2947                 $sql .= " $tailOpts";
2948
2949                 return $this->query( $sql, $fname );
2950         }
2951
2952         /**
2953          * Construct a LIMIT query with optional offset. This is used for query
2954          * pages. The SQL should be adjusted so that only the first $limit rows
2955          * are returned. If $offset is provided as well, then the first $offset
2956          * rows should be discarded, and the next $limit rows should be returned.
2957          * If the result of the query is not ordered, then the rows to be returned
2958          * are theoretically arbitrary.
2959          *
2960          * $sql is expected to be a SELECT, if that makes a difference.
2961          *
2962          * The version provided by default works in MySQL and SQLite. It will very
2963          * likely need to be overridden for most other DBMSes.
2964          *
2965          * @param string $sql SQL query we will append the limit too
2966          * @param int $limit The SQL limit
2967          * @param int|bool $offset The SQL offset (default false)
2968          * @throws DBUnexpectedError
2969          * @return string
2970          */
2971         public function limitResult( $sql, $limit, $offset = false ) {
2972                 if ( !is_numeric( $limit ) ) {
2973                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2974                 }
2975
2976                 return "$sql LIMIT "
2977                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2978                         . "{$limit} ";
2979         }
2980
2981         /**
2982          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2983          * within the UNION construct.
2984          * @return bool
2985          */
2986         public function unionSupportsOrderAndLimit() {
2987                 return true; // True for almost every DB supported
2988         }
2989
2990         /**
2991          * Construct a UNION query
2992          * This is used for providing overload point for other DB abstractions
2993          * not compatible with the MySQL syntax.
2994          * @param array $sqls SQL statements to combine
2995          * @param bool $all Use UNION ALL
2996          * @return string SQL fragment
2997          */
2998         public function unionQueries( $sqls, $all ) {
2999                 $glue = $all ? ') UNION ALL (' : ') UNION (';
3000
3001                 return '(' . implode( $glue, $sqls ) . ')';
3002         }
3003
3004         /**
3005          * Returns an SQL expression for a simple conditional. This doesn't need
3006          * to be overridden unless CASE isn't supported in your DBMS.
3007          *
3008          * @param string|array $cond SQL expression which will result in a boolean value
3009          * @param string $trueVal SQL expression to return if true
3010          * @param string $falseVal SQL expression to return if false
3011          * @return string SQL fragment
3012          */
3013         public function conditional( $cond, $trueVal, $falseVal ) {
3014                 if ( is_array( $cond ) ) {
3015                         $cond = $this->makeList( $cond, LIST_AND );
3016                 }
3017
3018                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
3019         }
3020
3021         /**
3022          * Returns a comand for str_replace function in SQL query.
3023          * Uses REPLACE() in MySQL
3024          *
3025          * @param string $orig Column to modify
3026          * @param string $old Column to seek
3027          * @param string $new Column to replace with
3028          *
3029          * @return string
3030          */
3031         public function strreplace( $orig, $old, $new ) {
3032                 return "REPLACE({$orig}, {$old}, {$new})";
3033         }
3034
3035         /**
3036          * Determines how long the server has been up
3037          * STUB
3038          *
3039          * @return int
3040          */
3041         public function getServerUptime() {
3042                 return 0;
3043         }
3044
3045         /**
3046          * Determines if the last failure was due to a deadlock
3047          * STUB
3048          *
3049          * @return bool
3050          */
3051         public function wasDeadlock() {
3052                 return false;
3053         }
3054
3055         /**
3056          * Determines if the last failure was due to a lock timeout
3057          * STUB
3058          *
3059          * @return bool
3060          */
3061         public function wasLockTimeout() {
3062                 return false;
3063         }
3064
3065         /**
3066          * Determines if the last query error was something that should be dealt
3067          * with by pinging the connection and reissuing the query.
3068          * STUB
3069          *
3070          * @return bool
3071          */
3072         public function wasErrorReissuable() {
3073                 return false;
3074         }
3075
3076         /**
3077          * Determines if the last failure was due to the database being read-only.
3078          * STUB
3079          *
3080          * @return bool
3081          */
3082         public function wasReadOnlyError() {
3083                 return false;
3084         }
3085
3086         /**
3087          * Perform a deadlock-prone transaction.
3088          *
3089          * This function invokes a callback function to perform a set of write
3090          * queries. If a deadlock occurs during the processing, the transaction
3091          * will be rolled back and the callback function will be called again.
3092          *
3093          * Usage:
3094          *   $dbw->deadlockLoop( callback, ... );
3095          *
3096          * Extra arguments are passed through to the specified callback function.
3097          *
3098          * Returns whatever the callback function returned on its successful,
3099          * iteration, or false on error, for example if the retry limit was
3100          * reached.
3101          *
3102          * @return bool
3103          */
3104         public function deadlockLoop() {
3105                 $this->begin( __METHOD__ );
3106                 $args = func_get_args();
3107                 $function = array_shift( $args );
3108                 $oldIgnore = $this->ignoreErrors( true );
3109                 $tries = self::DEADLOCK_TRIES;
3110
3111                 if ( is_array( $function ) ) {
3112                         $fname = $function[0];
3113                 } else {
3114                         $fname = $function;
3115                 }
3116
3117                 do {
3118                         $retVal = call_user_func_array( $function, $args );
3119                         $error = $this->lastError();
3120                         $errno = $this->lastErrno();
3121                         $sql = $this->lastQuery();
3122
3123                         if ( $errno ) {
3124                                 if ( $this->wasDeadlock() ) {
3125                                         # Retry
3126                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3127                                 } else {
3128                                         $this->reportQueryError( $error, $errno, $sql, $fname );
3129                                 }
3130                         }
3131                 } while ( $this->wasDeadlock() && --$tries > 0 );
3132
3133                 $this->ignoreErrors( $oldIgnore );
3134
3135                 if ( $tries <= 0 ) {
3136                         $this->rollback( __METHOD__ );
3137                         $this->reportQueryError( $error, $errno, $sql, $fname );
3138
3139                         return false;
3140                 } else {
3141                         $this->commit( __METHOD__ );
3142
3143                         return $retVal;
3144                 }
3145         }
3146
3147         /**
3148          * Wait for the slave to catch up to a given master position.
3149          *
3150          * @param DBMasterPos $pos
3151          * @param int $timeout The maximum number of seconds to wait for
3152          *   synchronisation
3153          * @return int Zero if the slave was past that position already,
3154          *   greater than zero if we waited for some period of time, less than
3155          *   zero if we timed out.
3156          */
3157         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3158                 # Real waits are implemented in the subclass.
3159                 return 0;
3160         }
3161
3162         /**
3163          * Get the replication position of this slave
3164          *
3165          * @return DBMasterPos|bool False if this is not a slave.
3166          */
3167         public function getSlavePos() {
3168                 # Stub
3169                 return false;
3170         }
3171
3172         /**
3173          * Get the position of this master
3174          *
3175          * @return DBMasterPos|bool False if this is not a master
3176          */
3177         public function getMasterPos() {
3178                 # Stub
3179                 return false;
3180         }
3181
3182         /**
3183          * Run an anonymous function as soon as there is no transaction pending.
3184          * If there is a transaction and it is rolled back, then the callback is cancelled.
3185          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
3186          * Callbacks must commit any transactions that they begin.
3187          *
3188          * This is useful for updates to different systems or when separate transactions are needed.
3189          * For example, one might want to enqueue jobs into a system outside the database, but only
3190          * after the database is updated so that the jobs will see the data when they actually run.
3191          * It can also be used for updates that easily cause deadlocks if locks are held too long.
3192          *
3193          * @param callable $callback
3194          * @since 1.20
3195          */
3196         final public function onTransactionIdle( $callback ) {
3197                 $this->mTrxIdleCallbacks[] = array( $callback, wfGetCaller() );
3198                 if ( !$this->mTrxLevel ) {
3199                         $this->runOnTransactionIdleCallbacks();
3200                 }
3201         }
3202
3203         /**
3204          * Run an anonymous function before the current transaction commits or now if there is none.
3205          * If there is a transaction and it is rolled back, then the callback is cancelled.
3206          * Callbacks must not start nor commit any transactions.
3207          *
3208          * This is useful for updates that easily cause deadlocks if locks are held too long
3209          * but where atomicity is strongly desired for these updates and some related updates.
3210          *
3211          * @param callable $callback
3212          * @since 1.22
3213          */
3214         final public function onTransactionPreCommitOrIdle( $callback ) {
3215                 if ( $this->mTrxLevel ) {
3216                         $this->mTrxPreCommitCallbacks[] = array( $callback, wfGetCaller() );
3217                 } else {
3218                         $this->onTransactionIdle( $callback ); // this will trigger immediately
3219                 }
3220         }
3221
3222         /**
3223          * Actually any "on transaction idle" callbacks.
3224          *
3225          * @since 1.20
3226          */
3227         protected function runOnTransactionIdleCallbacks() {
3228                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
3229
3230                 $e = $ePrior = null; // last exception
3231                 do { // callbacks may add callbacks :)
3232                         $callbacks = $this->mTrxIdleCallbacks;
3233                         $this->mTrxIdleCallbacks = array(); // recursion guard
3234                         foreach ( $callbacks as $callback ) {
3235                                 try {
3236                                         list( $phpCallback ) = $callback;
3237                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
3238                                         call_user_func( $phpCallback );
3239                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3240                                 } catch ( Exception $e ) {
3241                                         if ( $ePrior ) {
3242                                                 MWExceptionHandler::logException( $ePrior );
3243                                         }
3244                                         $ePrior = $e;
3245                                 }
3246                         }
3247                 } while ( count( $this->mTrxIdleCallbacks ) );
3248
3249                 if ( $e instanceof Exception ) {
3250                         throw $e; // re-throw any last exception
3251                 }
3252         }
3253
3254         /**
3255          * Actually any "on transaction pre-commit" callbacks.
3256          *
3257          * @since 1.22
3258          */
3259         protected function runOnTransactionPreCommitCallbacks() {
3260                 $e = $ePrior = null; // last exception
3261                 do { // callbacks may add callbacks :)
3262                         $callbacks = $this->mTrxPreCommitCallbacks;
3263                         $this->mTrxPreCommitCallbacks = array(); // recursion guard
3264                         foreach ( $callbacks as $callback ) {
3265                                 try {
3266                                         list( $phpCallback ) = $callback;
3267                                         call_user_func( $phpCallback );
3268                                 } catch ( Exception $e ) {
3269                                         if ( $ePrior ) {
3270                                                 MWExceptionHandler::logException( $ePrior );
3271                                         }
3272                                         $ePrior = $e;
3273                                 }
3274                         }
3275                 } while ( count( $this->mTrxPreCommitCallbacks ) );
3276
3277                 if ( $e instanceof Exception ) {
3278                         throw $e; // re-throw any last exception
3279                 }
3280         }
3281
3282         /**
3283          * Begin an atomic section of statements
3284          *
3285          * If a transaction has been started already, just keep track of the given
3286          * section name to make sure the transaction is not committed pre-maturely.
3287          * This function can be used in layers (with sub-sections), so use a stack
3288          * to keep track of the different atomic sections. If there is no transaction,
3289          * start one implicitly.
3290          *
3291          * The goal of this function is to create an atomic section of SQL queries
3292          * without having to start a new transaction if it already exists.
3293          *
3294          * Atomic sections are more strict than transactions. With transactions,
3295          * attempting to begin a new transaction when one is already running results
3296          * in MediaWiki issuing a brief warning and doing an implicit commit. All
3297          * atomic levels *must* be explicitly closed using DatabaseBase::endAtomic(),
3298          * and any database transactions cannot be began or committed until all atomic
3299          * levels are closed. There is no such thing as implicitly opening or closing
3300          * an atomic section.
3301          *
3302          * @since 1.23
3303          * @param string $fname
3304          * @throws DBError
3305          */
3306         final public function startAtomic( $fname = __METHOD__ ) {
3307                 if ( !$this->mTrxLevel ) {
3308                         $this->begin( $fname );
3309                         $this->mTrxAutomatic = true;
3310                         $this->mTrxAutomaticAtomic = true;
3311                 }
3312
3313                 $this->mTrxAtomicLevels->push( $fname );
3314         }
3315
3316         /**
3317          * Ends an atomic section of SQL statements
3318          *
3319          * Ends the next section of atomic SQL statements and commits the transaction
3320          * if necessary.
3321          *
3322          * @since 1.23
3323          * @see DatabaseBase::startAtomic
3324          * @param string $fname
3325          * @throws DBError
3326          */
3327         final public function endAtomic( $fname = __METHOD__ ) {
3328                 if ( !$this->mTrxLevel ) {
3329                         throw new DBUnexpectedError( $this, 'No atomic transaction is open.' );
3330                 }
3331                 if ( $this->mTrxAtomicLevels->isEmpty() ||
3332                         $this->mTrxAtomicLevels->pop() !== $fname
3333                 ) {
3334                         throw new DBUnexpectedError( $this, 'Invalid atomic section ended.' );
3335                 }
3336
3337                 if ( $this->mTrxAtomicLevels->isEmpty() && $this->mTrxAutomaticAtomic ) {
3338                         $this->commit( $fname, 'flush' );
3339                 }
3340         }
3341
3342         /**
3343          * Begin a transaction. If a transaction is already in progress,
3344          * that transaction will be committed before the new transaction is started.
3345          *
3346          * Note that when the DBO_TRX flag is set (which is usually the case for web
3347          * requests, but not for maintenance scripts), any previous database query
3348          * will have started a transaction automatically.
3349          *
3350          * Nesting of transactions is not supported. Attempts to nest transactions
3351          * will cause a warning, unless the current transaction was started
3352          * automatically because of the DBO_TRX flag.
3353          *
3354          * @param string $fname
3355          * @throws DBError
3356          */
3357         final public function begin( $fname = __METHOD__ ) {
3358                 global $wgDebugDBTransactions;
3359
3360                 if ( $this->mTrxLevel ) { // implicit commit
3361                         if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3362                                 // If the current transaction was an automatic atomic one, then we definitely have
3363                                 // a problem. Same if there is any unclosed atomic level.
3364                                 throw new DBUnexpectedError( $this,
3365                                         "Attempted to start explicit transaction when atomic levels are still open."
3366                                 );
3367                         } elseif ( !$this->mTrxAutomatic ) {
3368                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3369                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3370                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3371                                         " performing implicit commit!";
3372                                 wfWarn( $msg );
3373                                 wfLogDBError( $msg,
3374                                         $this->getLogContext( array(
3375                                                 'method' => __METHOD__,
3376                                                 'fname' => $fname,
3377                                         ) )
3378                                 );
3379                         } else {
3380                                 // if the transaction was automatic and has done write operations,
3381                                 // log it if $wgDebugDBTransactions is enabled.
3382                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3383                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3384                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3385                                         );
3386                                 }
3387                         }
3388
3389                         $this->runOnTransactionPreCommitCallbacks();
3390                         $this->doCommit( $fname );
3391                         if ( $this->mTrxDoneWrites ) {
3392                                 Profiler::instance()->getTransactionProfiler()->transactionWritingOut(
3393                                         $this->mServer, $this->mDBname, $this->mTrxShortId );
3394                         }
3395                         $this->runOnTransactionIdleCallbacks();
3396                 }
3397
3398                 # Avoid fatals if close() was called
3399                 if ( !$this->isOpen() ) {
3400                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3401                 }
3402
3403                 $this->doBegin( $fname );
3404                 $this->mTrxTimestamp = microtime( true );
3405                 $this->mTrxFname = $fname;
3406                 $this->mTrxDoneWrites = false;
3407                 $this->mTrxAutomatic = false;
3408                 $this->mTrxAutomaticAtomic = false;
3409                 $this->mTrxAtomicLevels = new SplStack;
3410                 $this->mTrxIdleCallbacks = array();
3411                 $this->mTrxPreCommitCallbacks = array();
3412                 $this->mTrxShortId = wfRandomString( 12 );
3413         }
3414
3415         /**
3416          * Issues the BEGIN command to the database server.
3417          *
3418          * @see DatabaseBase::begin()
3419          * @param string $fname
3420          */
3421         protected function doBegin( $fname ) {
3422                 $this->query( 'BEGIN', $fname );
3423                 $this->mTrxLevel = 1;
3424         }
3425
3426         /**
3427          * Commits a transaction previously started using begin().
3428          * If no transaction is in progress, a warning is issued.
3429          *
3430          * Nesting of transactions is not supported.
3431          *
3432          * @param string $fname
3433          * @param string $flush Flush flag, set to 'flush' to disable warnings about
3434          *   explicitly committing implicit transactions, or calling commit when no
3435          *   transaction is in progress. This will silently break any ongoing
3436          *   explicit transaction. Only set the flush flag if you are sure that it
3437          *   is safe to ignore these warnings in your context.
3438          * @throws DBUnexpectedError
3439          */
3440         final public function commit( $fname = __METHOD__, $flush = '' ) {
3441                 if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3442                         // There are still atomic sections open. This cannot be ignored
3443                         throw new DBUnexpectedError(
3444                                 $this,
3445                                 "Attempted to commit transaction while atomic sections are still open"
3446                         );
3447                 }
3448
3449                 if ( $flush === 'flush' ) {
3450                         if ( !$this->mTrxLevel ) {
3451                                 return; // nothing to do
3452                         } elseif ( !$this->mTrxAutomatic ) {
3453                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3454                         }
3455                 } else {
3456                         if ( !$this->mTrxLevel ) {
3457                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3458                                 return; // nothing to do
3459                         } elseif ( $this->mTrxAutomatic ) {
3460                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3461                         }
3462                 }
3463
3464                 # Avoid fatals if close() was called
3465                 if ( !$this->isOpen() ) {
3466                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3467                 }
3468
3469                 $this->runOnTransactionPreCommitCallbacks();
3470                 $this->doCommit( $fname );
3471                 if ( $this->mTrxDoneWrites ) {
3472                         Profiler::instance()->getTransactionProfiler()->transactionWritingOut(
3473                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
3474                 }
3475                 $this->runOnTransactionIdleCallbacks();
3476         }
3477
3478         /**
3479          * Issues the COMMIT command to the database server.
3480          *
3481          * @see DatabaseBase::commit()
3482          * @param string $fname
3483          */
3484         protected function doCommit( $fname ) {
3485                 if ( $this->mTrxLevel ) {
3486                         $this->query( 'COMMIT', $fname );
3487                         $this->mTrxLevel = 0;
3488                 }
3489         }
3490
3491         /**
3492          * Rollback a transaction previously started using begin().
3493          * If no transaction is in progress, a warning is issued.
3494          *
3495          * No-op on non-transactional databases.
3496          *
3497          * @param string $fname
3498          * @param string $flush Flush flag, set to 'flush' to disable warnings about
3499          *   calling rollback when no transaction is in progress. This will silently
3500          *   break any ongoing explicit transaction. Only set the flush flag if you
3501          *   are sure that it is safe to ignore these warnings in your context.
3502          * @since 1.23 Added $flush parameter
3503          */
3504         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3505                 if ( $flush !== 'flush' ) {
3506                         if ( !$this->mTrxLevel ) {
3507                                 wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3508                                 return; // nothing to do
3509                         } elseif ( $this->mTrxAutomatic ) {
3510                                 wfWarn( "$fname: Explicit rollback of implicit transaction. Something may be out of sync!" );
3511                         }
3512                 } else {
3513                         if ( !$this->mTrxLevel ) {
3514                                 return; // nothing to do
3515                         } elseif ( !$this->mTrxAutomatic ) {
3516                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3517                         }
3518                 }
3519
3520                 # Avoid fatals if close() was called
3521                 if ( !$this->isOpen() ) {
3522                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3523                 }
3524
3525                 $this->doRollback( $fname );
3526                 $this->mTrxIdleCallbacks = array(); // cancel
3527                 $this->mTrxPreCommitCallbacks = array(); // cancel
3528                 $this->mTrxAtomicLevels = new SplStack;
3529                 if ( $this->mTrxDoneWrites ) {
3530                         Profiler::instance()->getTransactionProfiler()->transactionWritingOut(
3531                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
3532                 }
3533         }
3534
3535         /**
3536          * Issues the ROLLBACK command to the database server.
3537          *
3538          * @see DatabaseBase::rollback()
3539          * @param string $fname
3540          */
3541         protected function doRollback( $fname ) {
3542                 if ( $this->mTrxLevel ) {
3543                         $this->query( 'ROLLBACK', $fname, true );
3544                         $this->mTrxLevel = 0;
3545                 }
3546         }
3547
3548         /**
3549          * Creates a new table with structure copied from existing table
3550          * Note that unlike most database abstraction functions, this function does not
3551          * automatically append database prefix, because it works at a lower
3552          * abstraction level.
3553          * The table names passed to this function shall not be quoted (this
3554          * function calls addIdentifierQuotes when needed).
3555          *
3556          * @param string $oldName Name of table whose structure should be copied
3557          * @param string $newName Name of table to be created
3558          * @param bool $temporary Whether the new table should be temporary
3559          * @param string $fname Calling function name
3560          * @throws MWException
3561          * @return bool True if operation was successful
3562          */
3563         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3564                 $fname = __METHOD__
3565         ) {
3566                 throw new MWException(
3567                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3568         }
3569
3570         /**
3571          * List all tables on the database
3572          *
3573          * @param string $prefix Only show tables with this prefix, e.g. mw_
3574          * @param string $fname Calling function name
3575          * @throws MWException
3576          */
3577         function listTables( $prefix = null, $fname = __METHOD__ ) {
3578                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3579         }
3580
3581         /**
3582          * Reset the views process cache set by listViews()
3583          * @since 1.22
3584          */
3585         final public function clearViewsCache() {
3586                 $this->allViews = null;
3587         }
3588
3589         /**
3590          * Lists all the VIEWs in the database
3591          *
3592          * For caching purposes the list of all views should be stored in
3593          * $this->allViews. The process cache can be cleared with clearViewsCache()
3594          *
3595          * @param string $prefix Only show VIEWs with this prefix, eg. unit_test_
3596          * @param string $fname Name of calling function
3597          * @throws MWException
3598          * @since 1.22
3599          */
3600         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3601                 throw new MWException( 'DatabaseBase::listViews is not implemented in descendant class' );
3602         }
3603
3604         /**
3605          * Differentiates between a TABLE and a VIEW
3606          *
3607          * @param string $name Name of the database-structure to test.
3608          * @throws MWException
3609          * @since 1.22
3610          */
3611         public function isView( $name ) {
3612                 throw new MWException( 'DatabaseBase::isView is not implemented in descendant class' );
3613         }
3614
3615         /**
3616          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3617          * to the format used for inserting into timestamp fields in this DBMS.
3618          *
3619          * The result is unquoted, and needs to be passed through addQuotes()
3620          * before it can be included in raw SQL.
3621          *
3622          * @param string|int $ts
3623          *
3624          * @return string
3625          */
3626         public function timestamp( $ts = 0 ) {
3627                 return wfTimestamp( TS_MW, $ts );
3628         }
3629
3630         /**
3631          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3632          * to the format used for inserting into timestamp fields in this DBMS. If
3633          * NULL is input, it is passed through, allowing NULL values to be inserted
3634          * into timestamp fields.
3635          *
3636          * The result is unquoted, and needs to be passed through addQuotes()
3637          * before it can be included in raw SQL.
3638          *
3639          * @param string|int $ts
3640          *
3641          * @return string
3642          */
3643         public function timestampOrNull( $ts = null ) {
3644                 if ( is_null( $ts ) ) {
3645                         return null;
3646                 } else {
3647                         return $this->timestamp( $ts );
3648                 }
3649         }
3650
3651         /**
3652          * Take the result from a query, and wrap it in a ResultWrapper if
3653          * necessary. Boolean values are passed through as is, to indicate success
3654          * of write queries or failure.
3655          *
3656          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3657          * resource, and it was necessary to call this function to convert it to
3658          * a wrapper. Nowadays, raw database objects are never exposed to external
3659          * callers, so this is unnecessary in external code. For compatibility with
3660          * old code, ResultWrapper objects are passed through unaltered.
3661          *
3662          * @param bool|ResultWrapper|resource $result
3663          * @return bool|ResultWrapper
3664          */
3665         public function resultObject( $result ) {
3666                 if ( empty( $result ) ) {
3667                         return false;
3668                 } elseif ( $result instanceof ResultWrapper ) {
3669                         return $result;
3670                 } elseif ( $result === true ) {
3671                         // Successful write query
3672                         return $result;
3673                 } else {
3674                         return new ResultWrapper( $this, $result );
3675                 }
3676         }
3677
3678         /**
3679          * Ping the server and try to reconnect if it there is no connection
3680          *
3681          * @return bool Success or failure
3682          */
3683         public function ping() {
3684                 # Stub. Not essential to override.
3685                 return true;
3686         }
3687
3688         /**
3689          * Get slave lag. Currently supported only by MySQL.
3690          *
3691          * Note that this function will generate a fatal error on many
3692          * installations. Most callers should use LoadBalancer::safeGetLag()
3693          * instead.
3694          *
3695          * @return int Database replication lag in seconds
3696          */
3697         public function getLag() {
3698                 return 0;
3699         }
3700
3701         /**
3702          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3703          *
3704          * @return int
3705          */
3706         function maxListLen() {
3707                 return 0;
3708         }
3709
3710         /**
3711          * Some DBMSs have a special format for inserting into blob fields, they
3712          * don't allow simple quoted strings to be inserted. To insert into such
3713          * a field, pass the data through this function before passing it to
3714          * DatabaseBase::insert().
3715          *
3716          * @param string $b
3717          * @return string
3718          */
3719         public function encodeBlob( $b ) {
3720                 return $b;
3721         }
3722
3723         /**
3724          * Some DBMSs return a special placeholder object representing blob fields
3725          * in result objects. Pass the object through this function to return the
3726          * original string.
3727          *
3728          * @param string $b
3729          * @return string
3730          */
3731         public function decodeBlob( $b ) {
3732                 return $b;
3733         }
3734
3735         /**
3736          * Override database's default behavior. $options include:
3737          *     'connTimeout' : Set the connection timeout value in seconds.
3738          *                     May be useful for very long batch queries such as
3739          *                     full-wiki dumps, where a single query reads out over
3740          *                     hours or days.
3741          *
3742          * @param array $options
3743          * @return void
3744          */
3745         public function setSessionOptions( array $options ) {
3746         }
3747
3748         /**
3749          * Read and execute SQL commands from a file.
3750          *
3751          * Returns true on success, error string or exception on failure (depending
3752          * on object's error ignore settings).
3753          *
3754          * @param string $filename File name to open
3755          * @param bool|callable $lineCallback Optional function called before reading each line
3756          * @param bool|callable $resultCallback Optional function called for each MySQL result
3757          * @param bool|string $fname Calling function name or false if name should be
3758          *   generated dynamically using $filename
3759          * @param bool|callable $inputCallback Optional function called for each
3760          *   complete line sent
3761          * @throws Exception|MWException
3762          * @return bool|string
3763          */
3764         public function sourceFile(
3765                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3766         ) {
3767                 wfSuppressWarnings();
3768                 $fp = fopen( $filename, 'r' );
3769                 wfRestoreWarnings();
3770
3771                 if ( false === $fp ) {
3772                         throw new MWException( "Could not open \"{$filename}\".\n" );
3773                 }
3774
3775                 if ( !$fname ) {
3776                         $fname = __METHOD__ . "( $filename )";
3777                 }
3778
3779                 try {
3780                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3781                 } catch ( MWException $e ) {
3782                         fclose( $fp );
3783                         throw $e;
3784                 }
3785
3786                 fclose( $fp );
3787
3788                 return $error;
3789         }
3790
3791         /**
3792          * Get the full path of a patch file. Originally based on archive()
3793          * from updaters.inc. Keep in mind this always returns a patch, as
3794          * it fails back to MySQL if no DB-specific patch can be found
3795          *
3796          * @param string $patch The name of the patch, like patch-something.sql
3797          * @return string Full path to patch file
3798          */
3799         public function patchPath( $patch ) {
3800                 global $IP;
3801
3802                 $dbType = $this->getType();
3803                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3804                         return "$IP/maintenance/$dbType/archives/$patch";
3805                 } else {
3806                         return "$IP/maintenance/archives/$patch";
3807                 }
3808         }
3809
3810         /**
3811          * Set variables to be used in sourceFile/sourceStream, in preference to the
3812          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3813          * all. If it's set to false, $GLOBALS will be used.
3814          *
3815          * @param bool|array $vars Mapping variable name to value.
3816          */
3817         public function setSchemaVars( $vars ) {
3818                 $this->mSchemaVars = $vars;
3819         }
3820
3821         /**
3822          * Read and execute commands from an open file handle.
3823          *
3824          * Returns true on success, error string or exception on failure (depending
3825          * on object's error ignore settings).
3826          *
3827          * @param resource $fp File handle
3828          * @param bool|callable $lineCallback Optional function called before reading each query
3829          * @param bool|callable $resultCallback Optional function called for each MySQL result
3830          * @param string $fname Calling function name
3831          * @param bool|callable $inputCallback Optional function called for each complete query sent
3832          * @return bool|string
3833          */
3834         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3835                 $fname = __METHOD__, $inputCallback = false
3836         ) {
3837                 $cmd = '';
3838
3839                 while ( !feof( $fp ) ) {
3840                         if ( $lineCallback ) {
3841                                 call_user_func( $lineCallback );
3842                         }
3843
3844                         $line = trim( fgets( $fp ) );
3845
3846                         if ( $line == '' ) {
3847                                 continue;
3848                         }
3849
3850                         if ( '-' == $line[0] && '-' == $line[1] ) {
3851                                 continue;
3852                         }
3853
3854                         if ( $cmd != '' ) {
3855                                 $cmd .= ' ';
3856                         }
3857
3858                         $done = $this->streamStatementEnd( $cmd, $line );
3859
3860                         $cmd .= "$line\n";
3861
3862                         if ( $done || feof( $fp ) ) {
3863                                 $cmd = $this->replaceVars( $cmd );
3864
3865                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3866                                         $res = $this->query( $cmd, $fname );
3867
3868                                         if ( $resultCallback ) {
3869                                                 call_user_func( $resultCallback, $res, $this );
3870                                         }
3871
3872                                         if ( false === $res ) {
3873                                                 $err = $this->lastError();
3874
3875                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3876                                         }
3877                                 }
3878                                 $cmd = '';
3879                         }
3880                 }
3881
3882                 return true;
3883         }
3884
3885         /**
3886          * Called by sourceStream() to check if we've reached a statement end
3887          *
3888          * @param string $sql SQL assembled so far
3889          * @param string $newLine New line about to be added to $sql
3890          * @return bool Whether $newLine contains end of the statement
3891          */
3892         public function streamStatementEnd( &$sql, &$newLine ) {
3893                 if ( $this->delimiter ) {
3894                         $prev = $newLine;
3895                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3896                         if ( $newLine != $prev ) {
3897                                 return true;
3898                         }
3899                 }
3900
3901                 return false;
3902         }
3903
3904         /**
3905          * Database independent variable replacement. Replaces a set of variables
3906          * in an SQL statement with their contents as given by $this->getSchemaVars().
3907          *
3908          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3909          *
3910          * - '{$var}' should be used for text and is passed through the database's
3911          *   addQuotes method.
3912          * - `{$var}` should be used for identifiers (eg: table and database names),
3913          *   it is passed through the database's addIdentifierQuotes method which
3914          *   can be overridden if the database uses something other than backticks.
3915          * - / *$var* / is just encoded, besides traditional table prefix and
3916          *   table options its use should be avoided.
3917          *
3918          * @param string $ins SQL statement to replace variables in
3919          * @return string The new SQL statement with variables replaced
3920          */
3921         protected function replaceSchemaVars( $ins ) {
3922                 $vars = $this->getSchemaVars();
3923                 foreach ( $vars as $var => $value ) {
3924                         // replace '{$var}'
3925                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3926                         // replace `{$var}`
3927                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3928                         // replace /*$var*/
3929                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3930                 }
3931
3932                 return $ins;
3933         }
3934
3935         /**
3936          * Replace variables in sourced SQL
3937          *
3938          * @param string $ins
3939          * @return string
3940          */
3941         protected function replaceVars( $ins ) {
3942                 $ins = $this->replaceSchemaVars( $ins );
3943
3944                 // Table prefixes
3945                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3946                         array( $this, 'tableNameCallback' ), $ins );
3947
3948                 // Index names
3949                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3950                         array( $this, 'indexNameCallback' ), $ins );
3951
3952                 return $ins;
3953         }
3954
3955         /**
3956          * Get schema variables. If none have been set via setSchemaVars(), then
3957          * use some defaults from the current object.
3958          *
3959          * @return array
3960          */
3961         protected function getSchemaVars() {
3962                 if ( $this->mSchemaVars ) {
3963                         return $this->mSchemaVars;
3964                 } else {
3965                         return $this->getDefaultSchemaVars();
3966                 }
3967         }
3968
3969         /**
3970          * Get schema variables to use if none have been set via setSchemaVars().
3971          *
3972          * Override this in derived classes to provide variables for tables.sql
3973          * and SQL patch files.
3974          *
3975          * @return array
3976          */
3977         protected function getDefaultSchemaVars() {
3978                 return array();
3979         }
3980
3981         /**
3982          * Table name callback
3983          *
3984          * @param array $matches
3985          * @return string
3986          */
3987         protected function tableNameCallback( $matches ) {
3988                 return $this->tableName( $matches[1] );
3989         }
3990
3991         /**
3992          * Index name callback
3993          *
3994          * @param array $matches
3995          * @return string
3996          */
3997         protected function indexNameCallback( $matches ) {
3998                 return $this->indexName( $matches[1] );
3999         }
4000
4001         /**
4002          * Check to see if a named lock is available. This is non-blocking.
4003          *
4004          * @param string $lockName Name of lock to poll
4005          * @param string $method Name of method calling us
4006          * @return bool
4007          * @since 1.20
4008          */
4009         public function lockIsFree( $lockName, $method ) {
4010                 return true;
4011         }
4012
4013         /**
4014          * Acquire a named lock
4015          *
4016          * Abstracted from Filestore::lock() so child classes can implement for
4017          * their own needs.
4018          *
4019          * @param string $lockName Name of lock to aquire
4020          * @param string $method Name of method calling us
4021          * @param int $timeout
4022          * @return bool
4023          */
4024         public function lock( $lockName, $method, $timeout = 5 ) {
4025                 return true;
4026         }
4027
4028         /**
4029          * Release a lock.
4030          *
4031          * @param string $lockName Name of lock to release
4032          * @param string $method Name of method calling us
4033          *
4034          * @return int Returns 1 if the lock was released, 0 if the lock was not established
4035          * by this thread (in which case the lock is not released), and NULL if the named
4036          * lock did not exist
4037          */
4038         public function unlock( $lockName, $method ) {
4039                 return true;
4040         }
4041
4042         /**
4043          * Lock specific tables
4044          *
4045          * @param array $read Array of tables to lock for read access
4046          * @param array $write Array of tables to lock for write access
4047          * @param string $method Name of caller
4048          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
4049          * @return bool
4050          */
4051         public function lockTables( $read, $write, $method, $lowPriority = true ) {
4052                 return true;
4053         }
4054
4055         /**
4056          * Unlock specific tables
4057          *
4058          * @param string $method The caller
4059          * @return bool
4060          */
4061         public function unlockTables( $method ) {
4062                 return true;
4063         }
4064
4065         /**
4066          * Delete a table
4067          * @param string $tableName
4068          * @param string $fName
4069          * @return bool|ResultWrapper
4070          * @since 1.18
4071          */
4072         public function dropTable( $tableName, $fName = __METHOD__ ) {
4073                 if ( !$this->tableExists( $tableName, $fName ) ) {
4074                         return false;
4075                 }
4076                 $sql = "DROP TABLE " . $this->tableName( $tableName );
4077                 if ( $this->cascadingDeletes() ) {
4078                         $sql .= " CASCADE";
4079                 }
4080
4081                 return $this->query( $sql, $fName );
4082         }
4083
4084         /**
4085          * Get search engine class. All subclasses of this need to implement this
4086          * if they wish to use searching.
4087          *
4088          * @return string
4089          */
4090         public function getSearchEngine() {
4091                 return 'SearchEngineDummy';
4092         }
4093
4094         /**
4095          * Find out when 'infinity' is. Most DBMSes support this. This is a special
4096          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
4097          * because "i" sorts after all numbers.
4098          *
4099          * @return string
4100          */
4101         public function getInfinity() {
4102                 return 'infinity';
4103         }
4104
4105         /**
4106          * Encode an expiry time into the DBMS dependent format
4107          *
4108          * @param string $expiry Timestamp for expiry, or the 'infinity' string
4109          * @return string
4110          */
4111         public function encodeExpiry( $expiry ) {
4112                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4113                         ? $this->getInfinity()
4114                         : $this->timestamp( $expiry );
4115         }
4116
4117         /**
4118          * Decode an expiry time into a DBMS independent format
4119          *
4120          * @param string $expiry DB timestamp field value for expiry
4121          * @param int $format TS_* constant, defaults to TS_MW
4122          * @return string
4123          */
4124         public function decodeExpiry( $expiry, $format = TS_MW ) {
4125                 return ( $expiry == '' || $expiry == $this->getInfinity() )
4126                         ? 'infinity'
4127                         : wfTimestamp( $format, $expiry );
4128         }
4129
4130         /**
4131          * Allow or deny "big selects" for this session only. This is done by setting
4132          * the sql_big_selects session variable.
4133          *
4134          * This is a MySQL-specific feature.
4135          *
4136          * @param bool|string $value True for allow, false for deny, or "default" to
4137          *   restore the initial value
4138          */
4139         public function setBigSelects( $value = true ) {
4140                 // no-op
4141         }
4142
4143         /**
4144          * @since 1.19
4145          * @return string
4146          */
4147         public function __toString() {
4148                 return (string)$this->mConn;
4149         }
4150
4151         /**
4152          * Run a few simple sanity checks
4153          */
4154         public function __destruct() {
4155                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
4156                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
4157                 }
4158                 if ( count( $this->mTrxIdleCallbacks ) || count( $this->mTrxPreCommitCallbacks ) ) {
4159                         $callers = array();
4160                         foreach ( $this->mTrxIdleCallbacks as $callbackInfo ) {
4161                                 $callers[] = $callbackInfo[1];
4162                         }
4163                         $callers = implode( ', ', $callers );
4164                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
4165                 }
4166         }
4167 }