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                 if ( $queryProf != '' ) {
1004                         $queryStartTime = microtime( true );
1005                         $queryProfile = new ScopedCallback( function() use ( $queryStartTime, $queryProf ) {
1006                                 $elapsed = microtime( true ) - $queryStartTime;
1007                                 $trxProfiler = Profiler::instance()->getTransactionProfiler();
1008                                 $trxProfiler->recordFunctionCompletion( $queryProf, $elapsed );
1009                         } );
1010                 }
1011
1012                 # Do the query and handle errors
1013                 $ret = $this->doQuery( $commentedSql );
1014
1015                 MWDebug::queryTime( $queryId );
1016
1017                 # Try reconnecting if the connection was lost
1018                 if ( false === $ret && $this->wasErrorReissuable() ) {
1019                         # Transaction is gone, like it or not
1020                         $hadTrx = $this->mTrxLevel; // possible lost transaction
1021                         $this->mTrxLevel = 0;
1022                         $this->mTrxIdleCallbacks = array(); // bug 65263
1023                         $this->mTrxPreCommitCallbacks = array(); // bug 65263
1024                         wfDebug( "Connection lost, reconnecting...\n" );
1025                         # Stash the last error values since ping() might clear them
1026                         $lastError = $this->lastError();
1027                         $lastErrno = $this->lastErrno();
1028                         if ( $this->ping() ) {
1029                                 global $wgRequestTime;
1030                                 wfDebug( "Reconnected\n" );
1031                                 $sqlx = $wgDebugDumpSqlLength ? substr( $commentedSql, 0, $wgDebugDumpSqlLength )
1032                                         : $commentedSql;
1033                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
1034                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
1035                                 if ( $elapsed < 300 ) {
1036                                         # Not a database error to lose a transaction after a minute or two
1037                                         wfLogDBError(
1038                                                 "Connection lost and reconnected after {$elapsed}s, query: $sqlx",
1039                                                 $this->getLogContext( array(
1040                                                         'method' => __METHOD__,
1041                                                         'query' => $sqlx,
1042                                                 ) )
1043                                         );
1044                                 }
1045                                 if ( $hadTrx ) {
1046                                         # Leave $ret as false and let an error be reported.
1047                                         # Callers may catch the exception and continue to use the DB.
1048                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname, $tempIgnore );
1049                                 } else {
1050                                         # Should be safe to silently retry (no trx and thus no callbacks)
1051                                         $ret = $this->doQuery( $commentedSql );
1052                                 }
1053                         } else {
1054                                 wfDebug( "Failed\n" );
1055                         }
1056                 }
1057
1058                 if ( false === $ret ) {
1059                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1060                 }
1061
1062                 if ( !Profiler::instance()->isStub() ) {
1063                         wfProfileOut( $queryProf );
1064                         wfProfileOut( $totalProf );
1065                 }
1066
1067                 return $this->resultObject( $ret );
1068         }
1069
1070         /**
1071          * Report a query error. Log the error, and if neither the object ignore
1072          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1073          *
1074          * @param string $error
1075          * @param int $errno
1076          * @param string $sql
1077          * @param string $fname
1078          * @param bool $tempIgnore
1079          * @throws DBQueryError
1080          */
1081         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1082                 # Ignore errors during error handling to avoid infinite recursion
1083                 $ignore = $this->ignoreErrors( true );
1084                 ++$this->mErrorCount;
1085
1086                 if ( $ignore || $tempIgnore ) {
1087                         wfDebug( "SQL ERROR (ignored): $error\n" );
1088                         $this->ignoreErrors( $ignore );
1089                 } else {
1090                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1091                         wfLogDBError(
1092                                 "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1093                                 $this->getLogContext( array(
1094                                         'method' => __METHOD__,
1095                                         'errno' => $errno,
1096                                         'error' => $error,
1097                                         'sql1line' => $sql1line,
1098                                         'fname' => $fname,
1099                                 ) )
1100                         );
1101                         wfDebug( "SQL ERROR: " . $error . "\n" );
1102                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1103                 }
1104         }
1105
1106         /**
1107          * Intended to be compatible with the PEAR::DB wrapper functions.
1108          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1109          *
1110          * ? = scalar value, quoted as necessary
1111          * ! = raw SQL bit (a function for instance)
1112          * & = filename; reads the file and inserts as a blob
1113          *     (we don't use this though...)
1114          *
1115          * @param string $sql
1116          * @param string $func
1117          *
1118          * @return array
1119          */
1120         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1121                 /* MySQL doesn't support prepared statements (yet), so just
1122                  * pack up the query for reference. We'll manually replace
1123                  * the bits later.
1124                  */
1125                 return array( 'query' => $sql, 'func' => $func );
1126         }
1127
1128         /**
1129          * Free a prepared query, generated by prepare().
1130          * @param string $prepared
1131          */
1132         protected function freePrepared( $prepared ) {
1133                 /* No-op by default */
1134         }
1135
1136         /**
1137          * Execute a prepared query with the various arguments
1138          * @param string $prepared The prepared sql
1139          * @param mixed $args Either an array here, or put scalars as varargs
1140          *
1141          * @return ResultWrapper
1142          */
1143         public function execute( $prepared, $args = null ) {
1144                 if ( !is_array( $args ) ) {
1145                         # Pull the var args
1146                         $args = func_get_args();
1147                         array_shift( $args );
1148                 }
1149
1150                 $sql = $this->fillPrepared( $prepared['query'], $args );
1151
1152                 return $this->query( $sql, $prepared['func'] );
1153         }
1154
1155         /**
1156          * For faking prepared SQL statements on DBs that don't support it directly.
1157          *
1158          * @param string $preparedQuery A 'preparable' SQL statement
1159          * @param array $args Array of Arguments to fill it with
1160          * @return string Executable SQL
1161          */
1162         public function fillPrepared( $preparedQuery, $args ) {
1163                 reset( $args );
1164                 $this->preparedArgs =& $args;
1165
1166                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1167                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1168         }
1169
1170         /**
1171          * preg_callback func for fillPrepared()
1172          * The arguments should be in $this->preparedArgs and must not be touched
1173          * while we're doing this.
1174          *
1175          * @param array $matches
1176          * @throws DBUnexpectedError
1177          * @return string
1178          */
1179         protected function fillPreparedArg( $matches ) {
1180                 switch ( $matches[1] ) {
1181                         case '\\?':
1182                                 return '?';
1183                         case '\\!':
1184                                 return '!';
1185                         case '\\&':
1186                                 return '&';
1187                 }
1188
1189                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1190
1191                 switch ( $matches[1] ) {
1192                         case '?':
1193                                 return $this->addQuotes( $arg );
1194                         case '!':
1195                                 return $arg;
1196                         case '&':
1197                                 # return $this->addQuotes( file_get_contents( $arg ) );
1198                                 throw new DBUnexpectedError(
1199                                         $this,
1200                                         '& mode is not implemented. If it\'s really needed, uncomment the line above.'
1201                                 );
1202                         default:
1203                                 throw new DBUnexpectedError(
1204                                         $this,
1205                                         'Received invalid match. This should never happen!'
1206                                 );
1207                 }
1208         }
1209
1210         /**
1211          * Free a result object returned by query() or select(). It's usually not
1212          * necessary to call this, just use unset() or let the variable holding
1213          * the result object go out of scope.
1214          *
1215          * @param mixed $res A SQL result
1216          */
1217         public function freeResult( $res ) {
1218         }
1219
1220         /**
1221          * A SELECT wrapper which returns a single field from a single result row.
1222          *
1223          * Usually throws a DBQueryError on failure. If errors are explicitly
1224          * ignored, returns false on failure.
1225          *
1226          * If no result rows are returned from the query, false is returned.
1227          *
1228          * @param string|array $table Table name. See DatabaseBase::select() for details.
1229          * @param string $var The field name to select. This must be a valid SQL
1230          *   fragment: do not use unvalidated user input.
1231          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1232          * @param string $fname The function name of the caller.
1233          * @param string|array $options The query options. See DatabaseBase::select() for details.
1234          *
1235          * @return bool|mixed The value from the field, or false on failure.
1236          */
1237         public function selectField( $table, $var, $cond = '', $fname = __METHOD__,
1238                 $options = array()
1239         ) {
1240                 if ( !is_array( $options ) ) {
1241                         $options = array( $options );
1242                 }
1243
1244                 $options['LIMIT'] = 1;
1245
1246                 $res = $this->select( $table, $var, $cond, $fname, $options );
1247
1248                 if ( $res === false || !$this->numRows( $res ) ) {
1249                         return false;
1250                 }
1251
1252                 $row = $this->fetchRow( $res );
1253
1254                 if ( $row !== false ) {
1255                         return reset( $row );
1256                 } else {
1257                         return false;
1258                 }
1259         }
1260
1261         /**
1262          * Returns an optional USE INDEX clause to go after the table, and a
1263          * string to go at the end of the query.
1264          *
1265          * @param array $options Associative array of options to be turned into
1266          *   an SQL query, valid keys are listed in the function.
1267          * @return array
1268          * @see DatabaseBase::select()
1269          */
1270         public function makeSelectOptions( $options ) {
1271                 $preLimitTail = $postLimitTail = '';
1272                 $startOpts = '';
1273
1274                 $noKeyOptions = array();
1275
1276                 foreach ( $options as $key => $option ) {
1277                         if ( is_numeric( $key ) ) {
1278                                 $noKeyOptions[$option] = true;
1279                         }
1280                 }
1281
1282                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1283
1284                 $preLimitTail .= $this->makeOrderBy( $options );
1285
1286                 // if (isset($options['LIMIT'])) {
1287                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1288                 //              isset($options['OFFSET']) ? $options['OFFSET']
1289                 //              : false);
1290                 // }
1291
1292                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1293                         $postLimitTail .= ' FOR UPDATE';
1294                 }
1295
1296                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1297                         $postLimitTail .= ' LOCK IN SHARE MODE';
1298                 }
1299
1300                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1301                         $startOpts .= 'DISTINCT';
1302                 }
1303
1304                 # Various MySQL extensions
1305                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1306                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1307                 }
1308
1309                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1310                         $startOpts .= ' HIGH_PRIORITY';
1311                 }
1312
1313                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1314                         $startOpts .= ' SQL_BIG_RESULT';
1315                 }
1316
1317                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1318                         $startOpts .= ' SQL_BUFFER_RESULT';
1319                 }
1320
1321                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1322                         $startOpts .= ' SQL_SMALL_RESULT';
1323                 }
1324
1325                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1326                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1327                 }
1328
1329                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1330                         $startOpts .= ' SQL_CACHE';
1331                 }
1332
1333                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1334                         $startOpts .= ' SQL_NO_CACHE';
1335                 }
1336
1337                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1338                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1339                 } else {
1340                         $useIndex = '';
1341                 }
1342
1343                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1344         }
1345
1346         /**
1347          * Returns an optional GROUP BY with an optional HAVING
1348          *
1349          * @param array $options Associative array of options
1350          * @return string
1351          * @see DatabaseBase::select()
1352          * @since 1.21
1353          */
1354         public function makeGroupByWithHaving( $options ) {
1355                 $sql = '';
1356                 if ( isset( $options['GROUP BY'] ) ) {
1357                         $gb = is_array( $options['GROUP BY'] )
1358                                 ? implode( ',', $options['GROUP BY'] )
1359                                 : $options['GROUP BY'];
1360                         $sql .= ' GROUP BY ' . $gb;
1361                 }
1362                 if ( isset( $options['HAVING'] ) ) {
1363                         $having = is_array( $options['HAVING'] )
1364                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1365                                 : $options['HAVING'];
1366                         $sql .= ' HAVING ' . $having;
1367                 }
1368
1369                 return $sql;
1370         }
1371
1372         /**
1373          * Returns an optional ORDER BY
1374          *
1375          * @param array $options Associative array of options
1376          * @return string
1377          * @see DatabaseBase::select()
1378          * @since 1.21
1379          */
1380         public function makeOrderBy( $options ) {
1381                 if ( isset( $options['ORDER BY'] ) ) {
1382                         $ob = is_array( $options['ORDER BY'] )
1383                                 ? implode( ',', $options['ORDER BY'] )
1384                                 : $options['ORDER BY'];
1385
1386                         return ' ORDER BY ' . $ob;
1387                 }
1388
1389                 return '';
1390         }
1391
1392         /**
1393          * Execute a SELECT query constructed using the various parameters provided.
1394          * See below for full details of the parameters.
1395          *
1396          * @param string|array $table Table name
1397          * @param string|array $vars Field names
1398          * @param string|array $conds Conditions
1399          * @param string $fname Caller function name
1400          * @param array $options Query options
1401          * @param array $join_conds Join conditions
1402          *
1403          *
1404          * @param string|array $table
1405          *
1406          * May be either an array of table names, or a single string holding a table
1407          * name. If an array is given, table aliases can be specified, for example:
1408          *
1409          *    array( 'a' => 'user' )
1410          *
1411          * This includes the user table in the query, with the alias "a" available
1412          * for use in field names (e.g. a.user_name).
1413          *
1414          * All of the table names given here are automatically run through
1415          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1416          * added, and various other table name mappings to be performed.
1417          *
1418          *
1419          * @param string|array $vars
1420          *
1421          * May be either a field name or an array of field names. The field names
1422          * can be complete fragments of SQL, for direct inclusion into the SELECT
1423          * query. If an array is given, field aliases can be specified, for example:
1424          *
1425          *   array( 'maxrev' => 'MAX(rev_id)' )
1426          *
1427          * This includes an expression with the alias "maxrev" in the query.
1428          *
1429          * If an expression is given, care must be taken to ensure that it is
1430          * DBMS-independent.
1431          *
1432          *
1433          * @param string|array $conds
1434          *
1435          * May be either a string containing a single condition, or an array of
1436          * conditions. If an array is given, the conditions constructed from each
1437          * element are combined with AND.
1438          *
1439          * Array elements may take one of two forms:
1440          *
1441          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1442          *   - Elements with a string key are interpreted as equality conditions,
1443          *     where the key is the field name.
1444          *     - If the value of such an array element is a scalar (such as a
1445          *       string), it will be treated as data and thus quoted appropriately.
1446          *       If it is null, an IS NULL clause will be added.
1447          *     - If the value is an array, an IN(...) clause will be constructed,
1448          *       such that the field name may match any of the elements in the
1449          *       array. The elements of the array will be quoted.
1450          *
1451          * Note that expressions are often DBMS-dependent in their syntax.
1452          * DBMS-independent wrappers are provided for constructing several types of
1453          * expression commonly used in condition queries. See:
1454          *    - DatabaseBase::buildLike()
1455          *    - DatabaseBase::conditional()
1456          *
1457          *
1458          * @param string|array $options
1459          *
1460          * Optional: Array of query options. Boolean options are specified by
1461          * including them in the array as a string value with a numeric key, for
1462          * example:
1463          *
1464          *    array( 'FOR UPDATE' )
1465          *
1466          * The supported options are:
1467          *
1468          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1469          *     with LIMIT can theoretically be used for paging through a result set,
1470          *     but this is discouraged in MediaWiki for performance reasons.
1471          *
1472          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1473          *     and then the first rows are taken until the limit is reached. LIMIT
1474          *     is applied to a result set after OFFSET.
1475          *
1476          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1477          *     changed until the next COMMIT.
1478          *
1479          *   - DISTINCT: Boolean: return only unique result rows.
1480          *
1481          *   - GROUP BY: May be either an SQL fragment string naming a field or
1482          *     expression to group by, or an array of such SQL fragments.
1483          *
1484          *   - HAVING: May be either an string containing a HAVING clause or an array of
1485          *     conditions building the HAVING clause. If an array is given, the conditions
1486          *     constructed from each element are combined with AND.
1487          *
1488          *   - ORDER BY: May be either an SQL fragment giving a field name or
1489          *     expression to order by, or an array of such SQL fragments.
1490          *
1491          *   - USE INDEX: This may be either a string giving the index name to use
1492          *     for the query, or an array. If it is an associative array, each key
1493          *     gives the table name (or alias), each value gives the index name to
1494          *     use for that table. All strings are SQL fragments and so should be
1495          *     validated by the caller.
1496          *
1497          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1498          *     instead of SELECT.
1499          *
1500          * And also the following boolean MySQL extensions, see the MySQL manual
1501          * for documentation:
1502          *
1503          *    - LOCK IN SHARE MODE
1504          *    - STRAIGHT_JOIN
1505          *    - HIGH_PRIORITY
1506          *    - SQL_BIG_RESULT
1507          *    - SQL_BUFFER_RESULT
1508          *    - SQL_SMALL_RESULT
1509          *    - SQL_CALC_FOUND_ROWS
1510          *    - SQL_CACHE
1511          *    - SQL_NO_CACHE
1512          *
1513          *
1514          * @param string|array $join_conds
1515          *
1516          * Optional associative array of table-specific join conditions. In the
1517          * most common case, this is unnecessary, since the join condition can be
1518          * in $conds. However, it is useful for doing a LEFT JOIN.
1519          *
1520          * The key of the array contains the table name or alias. The value is an
1521          * array with two elements, numbered 0 and 1. The first gives the type of
1522          * join, the second is an SQL fragment giving the join condition for that
1523          * table. For example:
1524          *
1525          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1526          *
1527          * @return ResultWrapper|bool If the query returned no rows, a ResultWrapper
1528          *   with no rows in it will be returned. If there was a query error, a
1529          *   DBQueryError exception will be thrown, except if the "ignore errors"
1530          *   option was set, in which case false will be returned.
1531          */
1532         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1533                 $options = array(), $join_conds = array() ) {
1534                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1535
1536                 return $this->query( $sql, $fname );
1537         }
1538
1539         /**
1540          * The equivalent of DatabaseBase::select() except that the constructed SQL
1541          * is returned, instead of being immediately executed. This can be useful for
1542          * doing UNION queries, where the SQL text of each query is needed. In general,
1543          * however, callers outside of Database classes should just use select().
1544          *
1545          * @param string|array $table Table name
1546          * @param string|array $vars Field names
1547          * @param string|array $conds Conditions
1548          * @param string $fname Caller function name
1549          * @param string|array $options Query options
1550          * @param string|array $join_conds Join conditions
1551          *
1552          * @return string SQL query string.
1553          * @see DatabaseBase::select()
1554          */
1555         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1556                 $options = array(), $join_conds = array()
1557         ) {
1558                 if ( is_array( $vars ) ) {
1559                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1560                 }
1561
1562                 $options = (array)$options;
1563                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1564                         ? $options['USE INDEX']
1565                         : array();
1566
1567                 if ( is_array( $table ) ) {
1568                         $from = ' FROM ' .
1569                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1570                 } elseif ( $table != '' ) {
1571                         if ( $table[0] == ' ' ) {
1572                                 $from = ' FROM ' . $table;
1573                         } else {
1574                                 $from = ' FROM ' .
1575                                         $this->tableNamesWithUseIndexOrJOIN( array( $table ), $useIndexes, array() );
1576                         }
1577                 } else {
1578                         $from = '';
1579                 }
1580
1581                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1582                         $this->makeSelectOptions( $options );
1583
1584                 if ( !empty( $conds ) ) {
1585                         if ( is_array( $conds ) ) {
1586                                 $conds = $this->makeList( $conds, LIST_AND );
1587                         }
1588                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1589                 } else {
1590                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1591                 }
1592
1593                 if ( isset( $options['LIMIT'] ) ) {
1594                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1595                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1596                 }
1597                 $sql = "$sql $postLimitTail";
1598
1599                 if ( isset( $options['EXPLAIN'] ) ) {
1600                         $sql = 'EXPLAIN ' . $sql;
1601                 }
1602
1603                 return $sql;
1604         }
1605
1606         /**
1607          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1608          * that a single row object is returned. If the query returns no rows,
1609          * false is returned.
1610          *
1611          * @param string|array $table Table name
1612          * @param string|array $vars Field names
1613          * @param array $conds Conditions
1614          * @param string $fname Caller function name
1615          * @param string|array $options Query options
1616          * @param array|string $join_conds Join conditions
1617          *
1618          * @return stdClass|bool
1619          */
1620         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1621                 $options = array(), $join_conds = array()
1622         ) {
1623                 $options = (array)$options;
1624                 $options['LIMIT'] = 1;
1625                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1626
1627                 if ( $res === false ) {
1628                         return false;
1629                 }
1630
1631                 if ( !$this->numRows( $res ) ) {
1632                         return false;
1633                 }
1634
1635                 $obj = $this->fetchObject( $res );
1636
1637                 return $obj;
1638         }
1639
1640         /**
1641          * Estimate the number of rows in dataset
1642          *
1643          * MySQL allows you to estimate the number of rows that would be returned
1644          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1645          * index cardinality statistics, and is notoriously inaccurate, especially
1646          * when large numbers of rows have recently been added or deleted.
1647          *
1648          * For DBMSs that don't support fast result size estimation, this function
1649          * will actually perform the SELECT COUNT(*).
1650          *
1651          * Takes the same arguments as DatabaseBase::select().
1652          *
1653          * @param string $table Table name
1654          * @param string $vars Unused
1655          * @param array|string $conds Filters on the table
1656          * @param string $fname Function name for profiling
1657          * @param array $options Options for select
1658          * @return int Row count
1659          */
1660         public function estimateRowCount(
1661                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = array()
1662         ) {
1663                 $rows = 0;
1664                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1665
1666                 if ( $res ) {
1667                         $row = $this->fetchRow( $res );
1668                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1669                 }
1670
1671                 return $rows;
1672         }
1673
1674         /**
1675          * Get the number of rows in dataset
1676          *
1677          * This is useful when trying to do COUNT(*) but with a LIMIT for performance.
1678          *
1679          * Takes the same arguments as DatabaseBase::select().
1680          *
1681          * @param string $table Table name
1682          * @param string $vars Unused
1683          * @param array|string $conds Filters on the table
1684          * @param string $fname Function name for profiling
1685          * @param array $options Options for select
1686          * @return int Row count
1687          * @since 1.24
1688          */
1689         public function selectRowCount(
1690                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = array()
1691         ) {
1692                 $rows = 0;
1693                 $sql = $this->selectSQLText( $table, '1', $conds, $fname, $options );
1694                 $res = $this->query( "SELECT COUNT(*) AS rowcount FROM ($sql) tmp_count" );
1695
1696                 if ( $res ) {
1697                         $row = $this->fetchRow( $res );
1698                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1699                 }
1700
1701                 return $rows;
1702         }
1703
1704         /**
1705          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1706          * It's only slightly flawed. Don't use for anything important.
1707          *
1708          * @param string $sql A SQL Query
1709          *
1710          * @return string
1711          */
1712         static function generalizeSQL( $sql ) {
1713                 # This does the same as the regexp below would do, but in such a way
1714                 # as to avoid crashing php on some large strings.
1715                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1716
1717                 $sql = str_replace( "\\\\", '', $sql );
1718                 $sql = str_replace( "\\'", '', $sql );
1719                 $sql = str_replace( "\\\"", '', $sql );
1720                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1721                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1722
1723                 # All newlines, tabs, etc replaced by single space
1724                 $sql = preg_replace( '/\s+/', ' ', $sql );
1725
1726                 # All numbers => N,
1727                 # except the ones surrounded by characters, e.g. l10n
1728                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1729                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1730
1731                 return $sql;
1732         }
1733
1734         /**
1735          * Determines whether a field exists in a table
1736          *
1737          * @param string $table Table name
1738          * @param string $field Filed to check on that table
1739          * @param string $fname Calling function name (optional)
1740          * @return bool Whether $table has filed $field
1741          */
1742         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1743                 $info = $this->fieldInfo( $table, $field );
1744
1745                 return (bool)$info;
1746         }
1747
1748         /**
1749          * Determines whether an index exists
1750          * Usually throws a DBQueryError on failure
1751          * If errors are explicitly ignored, returns NULL on failure
1752          *
1753          * @param string $table
1754          * @param string $index
1755          * @param string $fname
1756          * @return bool|null
1757          */
1758         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1759                 if ( !$this->tableExists( $table ) ) {
1760                         return null;
1761                 }
1762
1763                 $info = $this->indexInfo( $table, $index, $fname );
1764                 if ( is_null( $info ) ) {
1765                         return null;
1766                 } else {
1767                         return $info !== false;
1768                 }
1769         }
1770
1771         /**
1772          * Query whether a given table exists
1773          *
1774          * @param string $table
1775          * @param string $fname
1776          * @return bool
1777          */
1778         public function tableExists( $table, $fname = __METHOD__ ) {
1779                 $table = $this->tableName( $table );
1780                 $old = $this->ignoreErrors( true );
1781                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1782                 $this->ignoreErrors( $old );
1783
1784                 return (bool)$res;
1785         }
1786
1787         /**
1788          * Determines if a given index is unique
1789          *
1790          * @param string $table
1791          * @param string $index
1792          *
1793          * @return bool
1794          */
1795         public function indexUnique( $table, $index ) {
1796                 $indexInfo = $this->indexInfo( $table, $index );
1797
1798                 if ( !$indexInfo ) {
1799                         return null;
1800                 }
1801
1802                 return !$indexInfo[0]->Non_unique;
1803         }
1804
1805         /**
1806          * Helper for DatabaseBase::insert().
1807          *
1808          * @param array $options
1809          * @return string
1810          */
1811         protected function makeInsertOptions( $options ) {
1812                 return implode( ' ', $options );
1813         }
1814
1815         /**
1816          * INSERT wrapper, inserts an array into a table.
1817          *
1818          * $a may be either:
1819          *
1820          *   - A single associative array. The array keys are the field names, and
1821          *     the values are the values to insert. The values are treated as data
1822          *     and will be quoted appropriately. If NULL is inserted, this will be
1823          *     converted to a database NULL.
1824          *   - An array with numeric keys, holding a list of associative arrays.
1825          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1826          *     each subarray must be identical to each other, and in the same order.
1827          *
1828          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1829          * returns success.
1830          *
1831          * $options is an array of options, with boolean options encoded as values
1832          * with numeric keys, in the same style as $options in
1833          * DatabaseBase::select(). Supported options are:
1834          *
1835          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1836          *     any rows which cause duplicate key errors are not inserted. It's
1837          *     possible to determine how many rows were successfully inserted using
1838          *     DatabaseBase::affectedRows().
1839          *
1840          * @param string $table Table name. This will be passed through
1841          *   DatabaseBase::tableName().
1842          * @param array $a Array of rows to insert
1843          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1844          * @param array $options Array of options
1845          *
1846          * @return bool
1847          */
1848         public function insert( $table, $a, $fname = __METHOD__, $options = array() ) {
1849                 # No rows to insert, easy just return now
1850                 if ( !count( $a ) ) {
1851                         return true;
1852                 }
1853
1854                 $table = $this->tableName( $table );
1855
1856                 if ( !is_array( $options ) ) {
1857                         $options = array( $options );
1858                 }
1859
1860                 $fh = null;
1861                 if ( isset( $options['fileHandle'] ) ) {
1862                         $fh = $options['fileHandle'];
1863                 }
1864                 $options = $this->makeInsertOptions( $options );
1865
1866                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1867                         $multi = true;
1868                         $keys = array_keys( $a[0] );
1869                 } else {
1870                         $multi = false;
1871                         $keys = array_keys( $a );
1872                 }
1873
1874                 $sql = 'INSERT ' . $options .
1875                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1876
1877                 if ( $multi ) {
1878                         $first = true;
1879                         foreach ( $a as $row ) {
1880                                 if ( $first ) {
1881                                         $first = false;
1882                                 } else {
1883                                         $sql .= ',';
1884                                 }
1885                                 $sql .= '(' . $this->makeList( $row ) . ')';
1886                         }
1887                 } else {
1888                         $sql .= '(' . $this->makeList( $a ) . ')';
1889                 }
1890
1891                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1892                         return false;
1893                 } elseif ( $fh !== null ) {
1894                         return true;
1895                 }
1896
1897                 return (bool)$this->query( $sql, $fname );
1898         }
1899
1900         /**
1901          * Make UPDATE options array for DatabaseBase::makeUpdateOptions
1902          *
1903          * @param array $options
1904          * @return array
1905          */
1906         protected function makeUpdateOptionsArray( $options ) {
1907                 if ( !is_array( $options ) ) {
1908                         $options = array( $options );
1909                 }
1910
1911                 $opts = array();
1912
1913                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1914                         $opts[] = $this->lowPriorityOption();
1915                 }
1916
1917                 if ( in_array( 'IGNORE', $options ) ) {
1918                         $opts[] = 'IGNORE';
1919                 }
1920
1921                 return $opts;
1922         }
1923
1924         /**
1925          * Make UPDATE options for the DatabaseBase::update function
1926          *
1927          * @param array $options The options passed to DatabaseBase::update
1928          * @return string
1929          */
1930         protected function makeUpdateOptions( $options ) {
1931                 $opts = $this->makeUpdateOptionsArray( $options );
1932
1933                 return implode( ' ', $opts );
1934         }
1935
1936         /**
1937          * UPDATE wrapper. Takes a condition array and a SET array.
1938          *
1939          * @param string $table Name of the table to UPDATE. This will be passed through
1940          *   DatabaseBase::tableName().
1941          * @param array $values An array of values to SET. For each array element,
1942          *   the key gives the field name, and the value gives the data to set
1943          *   that field to. The data will be quoted by DatabaseBase::addQuotes().
1944          * @param array $conds An array of conditions (WHERE). See
1945          *   DatabaseBase::select() for the details of the format of condition
1946          *   arrays. Use '*' to update all rows.
1947          * @param string $fname The function name of the caller (from __METHOD__),
1948          *   for logging and profiling.
1949          * @param array $options An array of UPDATE options, can be:
1950          *   - IGNORE: Ignore unique key conflicts
1951          *   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1952          * @return bool
1953          */
1954         function update( $table, $values, $conds, $fname = __METHOD__, $options = array() ) {
1955                 $table = $this->tableName( $table );
1956                 $opts = $this->makeUpdateOptions( $options );
1957                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1958
1959                 if ( $conds !== array() && $conds !== '*' ) {
1960                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1961                 }
1962
1963                 return $this->query( $sql, $fname );
1964         }
1965
1966         /**
1967          * Makes an encoded list of strings from an array
1968          *
1969          * @param array $a Containing the data
1970          * @param int $mode Constant
1971          *    - LIST_COMMA: Comma separated, no field names
1972          *    - LIST_AND:   ANDed WHERE clause (without the WHERE). See the
1973          *      documentation for $conds in DatabaseBase::select().
1974          *    - LIST_OR:    ORed WHERE clause (without the WHERE)
1975          *    - LIST_SET:   Comma separated with field names, like a SET clause
1976          *    - LIST_NAMES: Comma separated field names
1977          * @throws MWException|DBUnexpectedError
1978          * @return string
1979          */
1980         public function makeList( $a, $mode = LIST_COMMA ) {
1981                 if ( !is_array( $a ) ) {
1982                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1983                 }
1984
1985                 $first = true;
1986                 $list = '';
1987
1988                 foreach ( $a as $field => $value ) {
1989                         if ( !$first ) {
1990                                 if ( $mode == LIST_AND ) {
1991                                         $list .= ' AND ';
1992                                 } elseif ( $mode == LIST_OR ) {
1993                                         $list .= ' OR ';
1994                                 } else {
1995                                         $list .= ',';
1996                                 }
1997                         } else {
1998                                 $first = false;
1999                         }
2000
2001                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
2002                                 $list .= "($value)";
2003                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
2004                                 $list .= "$value";
2005                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
2006                                 if ( count( $value ) == 0 ) {
2007                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
2008                                 } elseif ( count( $value ) == 1 ) {
2009                                         // Special-case single values, as IN isn't terribly efficient
2010                                         // Don't necessarily assume the single key is 0; we don't
2011                                         // enforce linear numeric ordering on other arrays here.
2012                                         $value = array_values( $value );
2013                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
2014                                 } else {
2015                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
2016                                 }
2017                         } elseif ( $value === null ) {
2018                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
2019                                         $list .= "$field IS ";
2020                                 } elseif ( $mode == LIST_SET ) {
2021                                         $list .= "$field = ";
2022                                 }
2023                                 $list .= 'NULL';
2024                         } else {
2025                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
2026                                         $list .= "$field = ";
2027                                 }
2028                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
2029                         }
2030                 }
2031
2032                 return $list;
2033         }
2034
2035         /**
2036          * Build a partial where clause from a 2-d array such as used for LinkBatch.
2037          * The keys on each level may be either integers or strings.
2038          *
2039          * @param array $data Organized as 2-d
2040          *    array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
2041          * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
2042          * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
2043          * @return string|bool SQL fragment, or false if no items in array
2044          */
2045         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2046                 $conds = array();
2047
2048                 foreach ( $data as $base => $sub ) {
2049                         if ( count( $sub ) ) {
2050                                 $conds[] = $this->makeList(
2051                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
2052                                         LIST_AND );
2053                         }
2054                 }
2055
2056                 if ( $conds ) {
2057                         return $this->makeList( $conds, LIST_OR );
2058                 } else {
2059                         // Nothing to search for...
2060                         return false;
2061                 }
2062         }
2063
2064         /**
2065          * Return aggregated value alias
2066          *
2067          * @param array $valuedata
2068          * @param string $valuename
2069          *
2070          * @return string
2071          */
2072         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2073                 return $valuename;
2074         }
2075
2076         /**
2077          * @param string $field
2078          * @return string
2079          */
2080         public function bitNot( $field ) {
2081                 return "(~$field)";
2082         }
2083
2084         /**
2085          * @param string $fieldLeft
2086          * @param string $fieldRight
2087          * @return string
2088          */
2089         public function bitAnd( $fieldLeft, $fieldRight ) {
2090                 return "($fieldLeft & $fieldRight)";
2091         }
2092
2093         /**
2094          * @param string $fieldLeft
2095          * @param string $fieldRight
2096          * @return string
2097          */
2098         public function bitOr( $fieldLeft, $fieldRight ) {
2099                 return "($fieldLeft | $fieldRight)";
2100         }
2101
2102         /**
2103          * Build a concatenation list to feed into a SQL query
2104          * @param array $stringList List of raw SQL expressions; caller is
2105          *   responsible for any quoting
2106          * @return string
2107          */
2108         public function buildConcat( $stringList ) {
2109                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2110         }
2111
2112         /**
2113          * Build a GROUP_CONCAT or equivalent statement for a query.
2114          *
2115          * This is useful for combining a field for several rows into a single string.
2116          * NULL values will not appear in the output, duplicated values will appear,
2117          * and the resulting delimiter-separated values have no defined sort order.
2118          * Code using the results may need to use the PHP unique() or sort() methods.
2119          *
2120          * @param string $delim Glue to bind the results together
2121          * @param string|array $table Table name
2122          * @param string $field Field name
2123          * @param string|array $conds Conditions
2124          * @param string|array $join_conds Join conditions
2125          * @return string SQL text
2126          * @since 1.23
2127          */
2128         public function buildGroupConcatField(
2129                 $delim, $table, $field, $conds = '', $join_conds = array()
2130         ) {
2131                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
2132
2133                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, array(), $join_conds ) . ')';
2134         }
2135
2136         /**
2137          * Change the current database
2138          *
2139          * @todo Explain what exactly will fail if this is not overridden.
2140          *
2141          * @param string $db
2142          *
2143          * @return bool Success or failure
2144          */
2145         public function selectDB( $db ) {
2146                 # Stub. Shouldn't cause serious problems if it's not overridden, but
2147                 # if your database engine supports a concept similar to MySQL's
2148                 # databases you may as well.
2149                 $this->mDBname = $db;
2150
2151                 return true;
2152         }
2153
2154         /**
2155          * Get the current DB name
2156          * @return string
2157          */
2158         public function getDBname() {
2159                 return $this->mDBname;
2160         }
2161
2162         /**
2163          * Get the server hostname or IP address
2164          * @return string
2165          */
2166         public function getServer() {
2167                 return $this->mServer;
2168         }
2169
2170         /**
2171          * Format a table name ready for use in constructing an SQL query
2172          *
2173          * This does two important things: it quotes the table names to clean them up,
2174          * and it adds a table prefix if only given a table name with no quotes.
2175          *
2176          * All functions of this object which require a table name call this function
2177          * themselves. Pass the canonical name to such functions. This is only needed
2178          * when calling query() directly.
2179          *
2180          * @param string $name Database table name
2181          * @param string $format One of:
2182          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2183          *            so that it can be used in a query.
2184          *   raw - Do not add identifier quotes to the table name
2185          * @return string Full database name
2186          */
2187         public function tableName( $name, $format = 'quoted' ) {
2188                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables, $wgSharedSchema;
2189                 # Skip the entire process when we have a string quoted on both ends.
2190                 # Note that we check the end so that we will still quote any use of
2191                 # use of `database`.table. But won't break things if someone wants
2192                 # to query a database table with a dot in the name.
2193                 if ( $this->isQuotedIdentifier( $name ) ) {
2194                         return $name;
2195                 }
2196
2197                 # Lets test for any bits of text that should never show up in a table
2198                 # name. Basically anything like JOIN or ON which are actually part of
2199                 # SQL queries, but may end up inside of the table value to combine
2200                 # sql. Such as how the API is doing.
2201                 # Note that we use a whitespace test rather than a \b test to avoid
2202                 # any remote case where a word like on may be inside of a table name
2203                 # surrounded by symbols which may be considered word breaks.
2204                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2205                         return $name;
2206                 }
2207
2208                 # Split database and table into proper variables.
2209                 # We reverse the explode so that database.table and table both output
2210                 # the correct table.
2211                 $dbDetails = explode( '.', $name, 3 );
2212                 if ( count( $dbDetails ) == 3 ) {
2213                         list( $database, $schema, $table ) = $dbDetails;
2214                         # We don't want any prefix added in this case
2215                         $prefix = '';
2216                 } elseif ( count( $dbDetails ) == 2 ) {
2217                         list( $database, $table ) = $dbDetails;
2218                         # We don't want any prefix added in this case
2219                         # In dbs that support it, $database may actually be the schema
2220                         # but that doesn't affect any of the functionality here
2221                         $prefix = '';
2222                         $schema = null;
2223                 } else {
2224                         list( $table ) = $dbDetails;
2225                         if ( $wgSharedDB !== null # We have a shared database
2226                                 && $this->mForeign == false # We're not working on a foreign database
2227                                 && !$this->isQuotedIdentifier( $table ) # Prevent shared tables listing '`table`'
2228                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2229                         ) {
2230                                 $database = $wgSharedDB;
2231                                 $schema = $wgSharedSchema === null ? $this->mSchema : $wgSharedSchema;
2232                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2233                         } else {
2234                                 $database = null;
2235                                 $schema = $this->mSchema; # Default schema
2236                                 $prefix = $this->mTablePrefix; # Default prefix
2237                         }
2238                 }
2239
2240                 # Quote $table and apply the prefix if not quoted.
2241                 # $tableName might be empty if this is called from Database::replaceVars()
2242                 $tableName = "{$prefix}{$table}";
2243                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) && $tableName !== '' ) {
2244                         $tableName = $this->addIdentifierQuotes( $tableName );
2245                 }
2246
2247                 # Quote $schema and merge it with the table name if needed
2248                 if ( $schema !== null ) {
2249                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $schema ) ) {
2250                                 $schema = $this->addIdentifierQuotes( $schema );
2251                         }
2252                         $tableName = $schema . '.' . $tableName;
2253                 }
2254
2255                 # Quote $database and merge it with the table name if needed
2256                 if ( $database !== null ) {
2257                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2258                                 $database = $this->addIdentifierQuotes( $database );
2259                         }
2260                         $tableName = $database . '.' . $tableName;
2261                 }
2262
2263                 return $tableName;
2264         }
2265
2266         /**
2267          * Fetch a number of table names into an array
2268          * This is handy when you need to construct SQL for joins
2269          *
2270          * Example:
2271          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2272          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2273          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2274          *
2275          * @return array
2276          */
2277         public function tableNames() {
2278                 $inArray = func_get_args();
2279                 $retVal = array();
2280
2281                 foreach ( $inArray as $name ) {
2282                         $retVal[$name] = $this->tableName( $name );
2283                 }
2284
2285                 return $retVal;
2286         }
2287
2288         /**
2289          * Fetch a number of table names into an zero-indexed numerical array
2290          * This is handy when you need to construct SQL for joins
2291          *
2292          * Example:
2293          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2294          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2295          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2296          *
2297          * @return array
2298          */
2299         public function tableNamesN() {
2300                 $inArray = func_get_args();
2301                 $retVal = array();
2302
2303                 foreach ( $inArray as $name ) {
2304                         $retVal[] = $this->tableName( $name );
2305                 }
2306
2307                 return $retVal;
2308         }
2309
2310         /**
2311          * Get an aliased table name
2312          * e.g. tableName AS newTableName
2313          *
2314          * @param string $name Table name, see tableName()
2315          * @param string|bool $alias Alias (optional)
2316          * @return string SQL name for aliased table. Will not alias a table to its own name
2317          */
2318         public function tableNameWithAlias( $name, $alias = false ) {
2319                 if ( !$alias || $alias == $name ) {
2320                         return $this->tableName( $name );
2321                 } else {
2322                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2323                 }
2324         }
2325
2326         /**
2327          * Gets an array of aliased table names
2328          *
2329          * @param array $tables Array( [alias] => table )
2330          * @return string[] See tableNameWithAlias()
2331          */
2332         public function tableNamesWithAlias( $tables ) {
2333                 $retval = array();
2334                 foreach ( $tables as $alias => $table ) {
2335                         if ( is_numeric( $alias ) ) {
2336                                 $alias = $table;
2337                         }
2338                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2339                 }
2340
2341                 return $retval;
2342         }
2343
2344         /**
2345          * Get an aliased field name
2346          * e.g. fieldName AS newFieldName
2347          *
2348          * @param string $name Field name
2349          * @param string|bool $alias Alias (optional)
2350          * @return string SQL name for aliased field. Will not alias a field to its own name
2351          */
2352         public function fieldNameWithAlias( $name, $alias = false ) {
2353                 if ( !$alias || (string)$alias === (string)$name ) {
2354                         return $name;
2355                 } else {
2356                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2357                 }
2358         }
2359
2360         /**
2361          * Gets an array of aliased field names
2362          *
2363          * @param array $fields Array( [alias] => field )
2364          * @return string[] See fieldNameWithAlias()
2365          */
2366         public function fieldNamesWithAlias( $fields ) {
2367                 $retval = array();
2368                 foreach ( $fields as $alias => $field ) {
2369                         if ( is_numeric( $alias ) ) {
2370                                 $alias = $field;
2371                         }
2372                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2373                 }
2374
2375                 return $retval;
2376         }
2377
2378         /**
2379          * Get the aliased table name clause for a FROM clause
2380          * which might have a JOIN and/or USE INDEX clause
2381          *
2382          * @param array $tables ( [alias] => table )
2383          * @param array $use_index Same as for select()
2384          * @param array $join_conds Same as for select()
2385          * @return string
2386          */
2387         protected function tableNamesWithUseIndexOrJOIN(
2388                 $tables, $use_index = array(), $join_conds = array()
2389         ) {
2390                 $ret = array();
2391                 $retJOIN = array();
2392                 $use_index = (array)$use_index;
2393                 $join_conds = (array)$join_conds;
2394
2395                 foreach ( $tables as $alias => $table ) {
2396                         if ( !is_string( $alias ) ) {
2397                                 // No alias? Set it equal to the table name
2398                                 $alias = $table;
2399                         }
2400                         // Is there a JOIN clause for this table?
2401                         if ( isset( $join_conds[$alias] ) ) {
2402                                 list( $joinType, $conds ) = $join_conds[$alias];
2403                                 $tableClause = $joinType;
2404                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2405                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2406                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2407                                         if ( $use != '' ) {
2408                                                 $tableClause .= ' ' . $use;
2409                                         }
2410                                 }
2411                                 $on = $this->makeList( (array)$conds, LIST_AND );
2412                                 if ( $on != '' ) {
2413                                         $tableClause .= ' ON (' . $on . ')';
2414                                 }
2415
2416                                 $retJOIN[] = $tableClause;
2417                         } elseif ( isset( $use_index[$alias] ) ) {
2418                                 // Is there an INDEX clause for this table?
2419                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2420                                 $tableClause .= ' ' . $this->useIndexClause(
2421                                         implode( ',', (array)$use_index[$alias] )
2422                                 );
2423
2424                                 $ret[] = $tableClause;
2425                         } else {
2426                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2427
2428                                 $ret[] = $tableClause;
2429                         }
2430                 }
2431
2432                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2433                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2434                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2435
2436                 // Compile our final table clause
2437                 return implode( ' ', array( $implicitJoins, $explicitJoins ) );
2438         }
2439
2440         /**
2441          * Get the name of an index in a given table
2442          *
2443          * @param string $index
2444          * @return string
2445          */
2446         protected function indexName( $index ) {
2447                 // Backwards-compatibility hack
2448                 $renamed = array(
2449                         'ar_usertext_timestamp' => 'usertext_timestamp',
2450                         'un_user_id' => 'user_id',
2451                         'un_user_ip' => 'user_ip',
2452                 );
2453
2454                 if ( isset( $renamed[$index] ) ) {
2455                         return $renamed[$index];
2456                 } else {
2457                         return $index;
2458                 }
2459         }
2460
2461         /**
2462          * Adds quotes and backslashes.
2463          *
2464          * @param string $s
2465          * @return string
2466          */
2467         public function addQuotes( $s ) {
2468                 if ( $s === null ) {
2469                         return 'NULL';
2470                 } else {
2471                         # This will also quote numeric values. This should be harmless,
2472                         # and protects against weird problems that occur when they really
2473                         # _are_ strings such as article titles and string->number->string
2474                         # conversion is not 1:1.
2475                         return "'" . $this->strencode( $s ) . "'";
2476                 }
2477         }
2478
2479         /**
2480          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2481          * MySQL uses `backticks` while basically everything else uses double quotes.
2482          * Since MySQL is the odd one out here the double quotes are our generic
2483          * and we implement backticks in DatabaseMysql.
2484          *
2485          * @param string $s
2486          * @return string
2487          */
2488         public function addIdentifierQuotes( $s ) {
2489                 return '"' . str_replace( '"', '""', $s ) . '"';
2490         }
2491
2492         /**
2493          * Returns if the given identifier looks quoted or not according to
2494          * the database convention for quoting identifiers .
2495          *
2496          * @param string $name
2497          * @return bool
2498          */
2499         public function isQuotedIdentifier( $name ) {
2500                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2501         }
2502
2503         /**
2504          * @param string $s
2505          * @return string
2506          */
2507         protected function escapeLikeInternal( $s ) {
2508                 return addcslashes( $s, '\%_' );
2509         }
2510
2511         /**
2512          * LIKE statement wrapper, receives a variable-length argument list with
2513          * parts of pattern to match containing either string literals that will be
2514          * escaped or tokens returned by anyChar() or anyString(). Alternatively,
2515          * the function could be provided with an array of aforementioned
2516          * parameters.
2517          *
2518          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
2519          * a LIKE clause that searches for subpages of 'My page title'.
2520          * Alternatively:
2521          *   $pattern = array( 'My_page_title/', $dbr->anyString() );
2522          *   $query .= $dbr->buildLike( $pattern );
2523          *
2524          * @since 1.16
2525          * @return string Fully built LIKE statement
2526          */
2527         public function buildLike() {
2528                 $params = func_get_args();
2529
2530                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2531                         $params = $params[0];
2532                 }
2533
2534                 $s = '';
2535
2536                 foreach ( $params as $value ) {
2537                         if ( $value instanceof LikeMatch ) {
2538                                 $s .= $value->toString();
2539                         } else {
2540                                 $s .= $this->escapeLikeInternal( $value );
2541                         }
2542                 }
2543
2544                 return " LIKE {$this->addQuotes( $s )} ";
2545         }
2546
2547         /**
2548          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2549          *
2550          * @return LikeMatch
2551          */
2552         public function anyChar() {
2553                 return new LikeMatch( '_' );
2554         }
2555
2556         /**
2557          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2558          *
2559          * @return LikeMatch
2560          */
2561         public function anyString() {
2562                 return new LikeMatch( '%' );
2563         }
2564
2565         /**
2566          * Returns an appropriately quoted sequence value for inserting a new row.
2567          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2568          * subclass will return an integer, and save the value for insertId()
2569          *
2570          * Any implementation of this function should *not* involve reusing
2571          * sequence numbers created for rolled-back transactions.
2572          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2573          * @param string $seqName
2574          * @return null|int
2575          */
2576         public function nextSequenceValue( $seqName ) {
2577                 return null;
2578         }
2579
2580         /**
2581          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2582          * is only needed because a) MySQL must be as efficient as possible due to
2583          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2584          * which index to pick. Anyway, other databases might have different
2585          * indexes on a given table. So don't bother overriding this unless you're
2586          * MySQL.
2587          * @param string $index
2588          * @return string
2589          */
2590         public function useIndexClause( $index ) {
2591                 return '';
2592         }
2593
2594         /**
2595          * REPLACE query wrapper.
2596          *
2597          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2598          * except that when there is a duplicate key error, the old row is deleted
2599          * and the new row is inserted in its place.
2600          *
2601          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2602          * perform the delete, we need to know what the unique indexes are so that
2603          * we know how to find the conflicting rows.
2604          *
2605          * It may be more efficient to leave off unique indexes which are unlikely
2606          * to collide. However if you do this, you run the risk of encountering
2607          * errors which wouldn't have occurred in MySQL.
2608          *
2609          * @param string $table The table to replace the row(s) in.
2610          * @param array $uniqueIndexes Is an array of indexes. Each element may be either
2611          *    a field name or an array of field names
2612          * @param array $rows Can be either a single row to insert, or multiple rows,
2613          *    in the same format as for DatabaseBase::insert()
2614          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2615          */
2616         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2617                 $quotedTable = $this->tableName( $table );
2618
2619                 if ( count( $rows ) == 0 ) {
2620                         return;
2621                 }
2622
2623                 # Single row case
2624                 if ( !is_array( reset( $rows ) ) ) {
2625                         $rows = array( $rows );
2626                 }
2627
2628                 foreach ( $rows as $row ) {
2629                         # Delete rows which collide
2630                         if ( $uniqueIndexes ) {
2631                                 $sql = "DELETE FROM $quotedTable WHERE ";
2632                                 $first = true;
2633                                 foreach ( $uniqueIndexes as $index ) {
2634                                         if ( $first ) {
2635                                                 $first = false;
2636                                                 $sql .= '( ';
2637                                         } else {
2638                                                 $sql .= ' ) OR ( ';
2639                                         }
2640                                         if ( is_array( $index ) ) {
2641                                                 $first2 = true;
2642                                                 foreach ( $index as $col ) {
2643                                                         if ( $first2 ) {
2644                                                                 $first2 = false;
2645                                                         } else {
2646                                                                 $sql .= ' AND ';
2647                                                         }
2648                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2649                                                 }
2650                                         } else {
2651                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2652                                         }
2653                                 }
2654                                 $sql .= ' )';
2655                                 $this->query( $sql, $fname );
2656                         }
2657
2658                         # Now insert the row
2659                         $this->insert( $table, $row, $fname );
2660                 }
2661         }
2662
2663         /**
2664          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2665          * statement.
2666          *
2667          * @param string $table Table name
2668          * @param array|string $rows Row(s) to insert
2669          * @param string $fname Caller function name
2670          *
2671          * @return ResultWrapper
2672          */
2673         protected function nativeReplace( $table, $rows, $fname ) {
2674                 $table = $this->tableName( $table );
2675
2676                 # Single row case
2677                 if ( !is_array( reset( $rows ) ) ) {
2678                         $rows = array( $rows );
2679                 }
2680
2681                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2682                 $first = true;
2683
2684                 foreach ( $rows as $row ) {
2685                         if ( $first ) {
2686                                 $first = false;
2687                         } else {
2688                                 $sql .= ',';
2689                         }
2690
2691                         $sql .= '(' . $this->makeList( $row ) . ')';
2692                 }
2693
2694                 return $this->query( $sql, $fname );
2695         }
2696
2697         /**
2698          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
2699          *
2700          * This updates any conflicting rows (according to the unique indexes) using
2701          * the provided SET clause and inserts any remaining (non-conflicted) rows.
2702          *
2703          * $rows may be either:
2704          *   - A single associative array. The array keys are the field names, and
2705          *     the values are the values to insert. The values are treated as data
2706          *     and will be quoted appropriately. If NULL is inserted, this will be
2707          *     converted to a database NULL.
2708          *   - An array with numeric keys, holding a list of associative arrays.
2709          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
2710          *     each subarray must be identical to each other, and in the same order.
2711          *
2712          * It may be more efficient to leave off unique indexes which are unlikely
2713          * to collide. However if you do this, you run the risk of encountering
2714          * errors which wouldn't have occurred in MySQL.
2715          *
2716          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
2717          * returns success.
2718          *
2719          * @since 1.22
2720          *
2721          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
2722          * @param array $rows A single row or list of rows to insert
2723          * @param array $uniqueIndexes List of single field names or field name tuples
2724          * @param array $set An array of values to SET. For each array element, the
2725          *   key gives the field name, and the value gives the data to set that
2726          *   field to. The data will be quoted by DatabaseBase::addQuotes().
2727          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2728          * @throws Exception
2729          * @return bool
2730          */
2731         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2732                 $fname = __METHOD__
2733         ) {
2734                 if ( !count( $rows ) ) {
2735                         return true; // nothing to do
2736                 }
2737
2738                 if ( !is_array( reset( $rows ) ) ) {
2739                         $rows = array( $rows );
2740                 }
2741
2742                 if ( count( $uniqueIndexes ) ) {
2743                         $clauses = array(); // list WHERE clauses that each identify a single row
2744                         foreach ( $rows as $row ) {
2745                                 foreach ( $uniqueIndexes as $index ) {
2746                                         $index = is_array( $index ) ? $index : array( $index ); // columns
2747                                         $rowKey = array(); // unique key to this row
2748                                         foreach ( $index as $column ) {
2749                                                 $rowKey[$column] = $row[$column];
2750                                         }
2751                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2752                                 }
2753                         }
2754                         $where = array( $this->makeList( $clauses, LIST_OR ) );
2755                 } else {
2756                         $where = false;
2757                 }
2758
2759                 $useTrx = !$this->mTrxLevel;
2760                 if ( $useTrx ) {
2761                         $this->begin( $fname );
2762                 }
2763                 try {
2764                         # Update any existing conflicting row(s)
2765                         if ( $where !== false ) {
2766                                 $ok = $this->update( $table, $set, $where, $fname );
2767                         } else {
2768                                 $ok = true;
2769                         }
2770                         # Now insert any non-conflicting row(s)
2771                         $ok = $this->insert( $table, $rows, $fname, array( 'IGNORE' ) ) && $ok;
2772                 } catch ( Exception $e ) {
2773                         if ( $useTrx ) {
2774                                 $this->rollback( $fname );
2775                         }
2776                         throw $e;
2777                 }
2778                 if ( $useTrx ) {
2779                         $this->commit( $fname );
2780                 }
2781
2782                 return $ok;
2783         }
2784
2785         /**
2786          * DELETE where the condition is a join.
2787          *
2788          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2789          * we use sub-selects
2790          *
2791          * For safety, an empty $conds will not delete everything. If you want to
2792          * delete all rows where the join condition matches, set $conds='*'.
2793          *
2794          * DO NOT put the join condition in $conds.
2795          *
2796          * @param string $delTable The table to delete from.
2797          * @param string $joinTable The other table.
2798          * @param string $delVar The variable to join on, in the first table.
2799          * @param string $joinVar The variable to join on, in the second table.
2800          * @param array $conds Condition array of field names mapped to variables,
2801          *   ANDed together in the WHERE clause
2802          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2803          * @throws DBUnexpectedError
2804          */
2805         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2806                 $fname = __METHOD__
2807         ) {
2808                 if ( !$conds ) {
2809                         throw new DBUnexpectedError( $this,
2810                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2811                 }
2812
2813                 $delTable = $this->tableName( $delTable );
2814                 $joinTable = $this->tableName( $joinTable );
2815                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2816                 if ( $conds != '*' ) {
2817                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2818                 }
2819                 $sql .= ')';
2820
2821                 $this->query( $sql, $fname );
2822         }
2823
2824         /**
2825          * Returns the size of a text field, or -1 for "unlimited"
2826          *
2827          * @param string $table
2828          * @param string $field
2829          * @return int
2830          */
2831         public function textFieldSize( $table, $field ) {
2832                 $table = $this->tableName( $table );
2833                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2834                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2835                 $row = $this->fetchObject( $res );
2836
2837                 $m = array();
2838
2839                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2840                         $size = $m[1];
2841                 } else {
2842                         $size = -1;
2843                 }
2844
2845                 return $size;
2846         }
2847
2848         /**
2849          * A string to insert into queries to show that they're low-priority, like
2850          * MySQL's LOW_PRIORITY. If no such feature exists, return an empty
2851          * string and nothing bad should happen.
2852          *
2853          * @return string Returns the text of the low priority option if it is
2854          *   supported, or a blank string otherwise
2855          */
2856         public function lowPriorityOption() {
2857                 return '';
2858         }
2859
2860         /**
2861          * DELETE query wrapper.
2862          *
2863          * @param array $table Table name
2864          * @param string|array $conds Array of conditions. See $conds in DatabaseBase::select()
2865          *   for the format. Use $conds == "*" to delete all rows
2866          * @param string $fname Name of the calling function
2867          * @throws DBUnexpectedError
2868          * @return bool|ResultWrapper
2869          */
2870         public function delete( $table, $conds, $fname = __METHOD__ ) {
2871                 if ( !$conds ) {
2872                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2873                 }
2874
2875                 $table = $this->tableName( $table );
2876                 $sql = "DELETE FROM $table";
2877
2878                 if ( $conds != '*' ) {
2879                         if ( is_array( $conds ) ) {
2880                                 $conds = $this->makeList( $conds, LIST_AND );
2881                         }
2882                         $sql .= ' WHERE ' . $conds;
2883                 }
2884
2885                 return $this->query( $sql, $fname );
2886         }
2887
2888         /**
2889          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2890          * into another table.
2891          *
2892          * @param string $destTable The table name to insert into
2893          * @param string|array $srcTable May be either a table name, or an array of table names
2894          *    to include in a join.
2895          *
2896          * @param array $varMap Must be an associative array of the form
2897          *    array( 'dest1' => 'source1', ...). Source items may be literals
2898          *    rather than field names, but strings should be quoted with
2899          *    DatabaseBase::addQuotes()
2900          *
2901          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2902          *    the details of the format of condition arrays. May be "*" to copy the
2903          *    whole table.
2904          *
2905          * @param string $fname The function name of the caller, from __METHOD__
2906          *
2907          * @param array $insertOptions Options for the INSERT part of the query, see
2908          *    DatabaseBase::insert() for details.
2909          * @param array $selectOptions Options for the SELECT part of the query, see
2910          *    DatabaseBase::select() for details.
2911          *
2912          * @return ResultWrapper
2913          */
2914         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2915                 $fname = __METHOD__,
2916                 $insertOptions = array(), $selectOptions = array()
2917         ) {
2918                 $destTable = $this->tableName( $destTable );
2919
2920                 if ( !is_array( $insertOptions ) ) {
2921                         $insertOptions = array( $insertOptions );
2922                 }
2923
2924                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2925
2926                 if ( !is_array( $selectOptions ) ) {
2927                         $selectOptions = array( $selectOptions );
2928                 }
2929
2930                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2931
2932                 if ( is_array( $srcTable ) ) {
2933                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2934                 } else {
2935                         $srcTable = $this->tableName( $srcTable );
2936                 }
2937
2938                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2939                         " SELECT $startOpts " . implode( ',', $varMap ) .
2940                         " FROM $srcTable $useIndex ";
2941
2942                 if ( $conds != '*' ) {
2943                         if ( is_array( $conds ) ) {
2944                                 $conds = $this->makeList( $conds, LIST_AND );
2945                         }
2946                         $sql .= " WHERE $conds";
2947                 }
2948
2949                 $sql .= " $tailOpts";
2950
2951                 return $this->query( $sql, $fname );
2952         }
2953
2954         /**
2955          * Construct a LIMIT query with optional offset. This is used for query
2956          * pages. The SQL should be adjusted so that only the first $limit rows
2957          * are returned. If $offset is provided as well, then the first $offset
2958          * rows should be discarded, and the next $limit rows should be returned.
2959          * If the result of the query is not ordered, then the rows to be returned
2960          * are theoretically arbitrary.
2961          *
2962          * $sql is expected to be a SELECT, if that makes a difference.
2963          *
2964          * The version provided by default works in MySQL and SQLite. It will very
2965          * likely need to be overridden for most other DBMSes.
2966          *
2967          * @param string $sql SQL query we will append the limit too
2968          * @param int $limit The SQL limit
2969          * @param int|bool $offset The SQL offset (default false)
2970          * @throws DBUnexpectedError
2971          * @return string
2972          */
2973         public function limitResult( $sql, $limit, $offset = false ) {
2974                 if ( !is_numeric( $limit ) ) {
2975                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2976                 }
2977
2978                 return "$sql LIMIT "
2979                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2980                         . "{$limit} ";
2981         }
2982
2983         /**
2984          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2985          * within the UNION construct.
2986          * @return bool
2987          */
2988         public function unionSupportsOrderAndLimit() {
2989                 return true; // True for almost every DB supported
2990         }
2991
2992         /**
2993          * Construct a UNION query
2994          * This is used for providing overload point for other DB abstractions
2995          * not compatible with the MySQL syntax.
2996          * @param array $sqls SQL statements to combine
2997          * @param bool $all Use UNION ALL
2998          * @return string SQL fragment
2999          */
3000         public function unionQueries( $sqls, $all ) {
3001                 $glue = $all ? ') UNION ALL (' : ') UNION (';
3002
3003                 return '(' . implode( $glue, $sqls ) . ')';
3004         }
3005
3006         /**
3007          * Returns an SQL expression for a simple conditional. This doesn't need
3008          * to be overridden unless CASE isn't supported in your DBMS.
3009          *
3010          * @param string|array $cond SQL expression which will result in a boolean value
3011          * @param string $trueVal SQL expression to return if true
3012          * @param string $falseVal SQL expression to return if false
3013          * @return string SQL fragment
3014          */
3015         public function conditional( $cond, $trueVal, $falseVal ) {
3016                 if ( is_array( $cond ) ) {
3017                         $cond = $this->makeList( $cond, LIST_AND );
3018                 }
3019
3020                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
3021         }
3022
3023         /**
3024          * Returns a comand for str_replace function in SQL query.
3025          * Uses REPLACE() in MySQL
3026          *
3027          * @param string $orig Column to modify
3028          * @param string $old Column to seek
3029          * @param string $new Column to replace with
3030          *
3031          * @return string
3032          */
3033         public function strreplace( $orig, $old, $new ) {
3034                 return "REPLACE({$orig}, {$old}, {$new})";
3035         }
3036
3037         /**
3038          * Determines how long the server has been up
3039          * STUB
3040          *
3041          * @return int
3042          */
3043         public function getServerUptime() {
3044                 return 0;
3045         }
3046
3047         /**
3048          * Determines if the last failure was due to a deadlock
3049          * STUB
3050          *
3051          * @return bool
3052          */
3053         public function wasDeadlock() {
3054                 return false;
3055         }
3056
3057         /**
3058          * Determines if the last failure was due to a lock timeout
3059          * STUB
3060          *
3061          * @return bool
3062          */
3063         public function wasLockTimeout() {
3064                 return false;
3065         }
3066
3067         /**
3068          * Determines if the last query error was something that should be dealt
3069          * with by pinging the connection and reissuing the query.
3070          * STUB
3071          *
3072          * @return bool
3073          */
3074         public function wasErrorReissuable() {
3075                 return false;
3076         }
3077
3078         /**
3079          * Determines if the last failure was due to the database being read-only.
3080          * STUB
3081          *
3082          * @return bool
3083          */
3084         public function wasReadOnlyError() {
3085                 return false;
3086         }
3087
3088         /**
3089          * Perform a deadlock-prone transaction.
3090          *
3091          * This function invokes a callback function to perform a set of write
3092          * queries. If a deadlock occurs during the processing, the transaction
3093          * will be rolled back and the callback function will be called again.
3094          *
3095          * Usage:
3096          *   $dbw->deadlockLoop( callback, ... );
3097          *
3098          * Extra arguments are passed through to the specified callback function.
3099          *
3100          * Returns whatever the callback function returned on its successful,
3101          * iteration, or false on error, for example if the retry limit was
3102          * reached.
3103          *
3104          * @return bool
3105          */
3106         public function deadlockLoop() {
3107                 $this->begin( __METHOD__ );
3108                 $args = func_get_args();
3109                 $function = array_shift( $args );
3110                 $oldIgnore = $this->ignoreErrors( true );
3111                 $tries = self::DEADLOCK_TRIES;
3112
3113                 if ( is_array( $function ) ) {
3114                         $fname = $function[0];
3115                 } else {
3116                         $fname = $function;
3117                 }
3118
3119                 do {
3120                         $retVal = call_user_func_array( $function, $args );
3121                         $error = $this->lastError();
3122                         $errno = $this->lastErrno();
3123                         $sql = $this->lastQuery();
3124
3125                         if ( $errno ) {
3126                                 if ( $this->wasDeadlock() ) {
3127                                         # Retry
3128                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3129                                 } else {
3130                                         $this->reportQueryError( $error, $errno, $sql, $fname );
3131                                 }
3132                         }
3133                 } while ( $this->wasDeadlock() && --$tries > 0 );
3134
3135                 $this->ignoreErrors( $oldIgnore );
3136
3137                 if ( $tries <= 0 ) {
3138                         $this->rollback( __METHOD__ );
3139                         $this->reportQueryError( $error, $errno, $sql, $fname );
3140
3141                         return false;
3142                 } else {
3143                         $this->commit( __METHOD__ );
3144
3145                         return $retVal;
3146                 }
3147         }
3148
3149         /**
3150          * Wait for the slave to catch up to a given master position.
3151          *
3152          * @param DBMasterPos $pos
3153          * @param int $timeout The maximum number of seconds to wait for
3154          *   synchronisation
3155          * @return int Zero if the slave was past that position already,
3156          *   greater than zero if we waited for some period of time, less than
3157          *   zero if we timed out.
3158          */
3159         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3160                 # Real waits are implemented in the subclass.
3161                 return 0;
3162         }
3163
3164         /**
3165          * Get the replication position of this slave
3166          *
3167          * @return DBMasterPos|bool False if this is not a slave.
3168          */
3169         public function getSlavePos() {
3170                 # Stub
3171                 return false;
3172         }
3173
3174         /**
3175          * Get the position of this master
3176          *
3177          * @return DBMasterPos|bool False if this is not a master
3178          */
3179         public function getMasterPos() {
3180                 # Stub
3181                 return false;
3182         }
3183
3184         /**
3185          * Run an anonymous function as soon as there is no transaction pending.
3186          * If there is a transaction and it is rolled back, then the callback is cancelled.
3187          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
3188          * Callbacks must commit any transactions that they begin.
3189          *
3190          * This is useful for updates to different systems or when separate transactions are needed.
3191          * For example, one might want to enqueue jobs into a system outside the database, but only
3192          * after the database is updated so that the jobs will see the data when they actually run.
3193          * It can also be used for updates that easily cause deadlocks if locks are held too long.
3194          *
3195          * @param callable $callback
3196          * @since 1.20
3197          */
3198         final public function onTransactionIdle( $callback ) {
3199                 $this->mTrxIdleCallbacks[] = array( $callback, wfGetCaller() );
3200                 if ( !$this->mTrxLevel ) {
3201                         $this->runOnTransactionIdleCallbacks();
3202                 }
3203         }
3204
3205         /**
3206          * Run an anonymous function before the current transaction commits or now if there is none.
3207          * If there is a transaction and it is rolled back, then the callback is cancelled.
3208          * Callbacks must not start nor commit any transactions.
3209          *
3210          * This is useful for updates that easily cause deadlocks if locks are held too long
3211          * but where atomicity is strongly desired for these updates and some related updates.
3212          *
3213          * @param callable $callback
3214          * @since 1.22
3215          */
3216         final public function onTransactionPreCommitOrIdle( $callback ) {
3217                 if ( $this->mTrxLevel ) {
3218                         $this->mTrxPreCommitCallbacks[] = array( $callback, wfGetCaller() );
3219                 } else {
3220                         $this->onTransactionIdle( $callback ); // this will trigger immediately
3221                 }
3222         }
3223
3224         /**
3225          * Actually any "on transaction idle" callbacks.
3226          *
3227          * @since 1.20
3228          */
3229         protected function runOnTransactionIdleCallbacks() {
3230                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
3231
3232                 $e = $ePrior = null; // last exception
3233                 do { // callbacks may add callbacks :)
3234                         $callbacks = $this->mTrxIdleCallbacks;
3235                         $this->mTrxIdleCallbacks = array(); // recursion guard
3236                         foreach ( $callbacks as $callback ) {
3237                                 try {
3238                                         list( $phpCallback ) = $callback;
3239                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
3240                                         call_user_func( $phpCallback );
3241                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3242                                 } catch ( Exception $e ) {
3243                                         if ( $ePrior ) {
3244                                                 MWExceptionHandler::logException( $ePrior );
3245                                         }
3246                                         $ePrior = $e;
3247                                 }
3248                         }
3249                 } while ( count( $this->mTrxIdleCallbacks ) );
3250
3251                 if ( $e instanceof Exception ) {
3252                         throw $e; // re-throw any last exception
3253                 }
3254         }
3255
3256         /**
3257          * Actually any "on transaction pre-commit" callbacks.
3258          *
3259          * @since 1.22
3260          */
3261         protected function runOnTransactionPreCommitCallbacks() {
3262                 $e = $ePrior = null; // last exception
3263                 do { // callbacks may add callbacks :)
3264                         $callbacks = $this->mTrxPreCommitCallbacks;
3265                         $this->mTrxPreCommitCallbacks = array(); // recursion guard
3266                         foreach ( $callbacks as $callback ) {
3267                                 try {
3268                                         list( $phpCallback ) = $callback;
3269                                         call_user_func( $phpCallback );
3270                                 } catch ( Exception $e ) {
3271                                         if ( $ePrior ) {
3272                                                 MWExceptionHandler::logException( $ePrior );
3273                                         }
3274                                         $ePrior = $e;
3275                                 }
3276                         }
3277                 } while ( count( $this->mTrxPreCommitCallbacks ) );
3278
3279                 if ( $e instanceof Exception ) {
3280                         throw $e; // re-throw any last exception
3281                 }
3282         }
3283
3284         /**
3285          * Begin an atomic section of statements
3286          *
3287          * If a transaction has been started already, just keep track of the given
3288          * section name to make sure the transaction is not committed pre-maturely.
3289          * This function can be used in layers (with sub-sections), so use a stack
3290          * to keep track of the different atomic sections. If there is no transaction,
3291          * start one implicitly.
3292          *
3293          * The goal of this function is to create an atomic section of SQL queries
3294          * without having to start a new transaction if it already exists.
3295          *
3296          * Atomic sections are more strict than transactions. With transactions,
3297          * attempting to begin a new transaction when one is already running results
3298          * in MediaWiki issuing a brief warning and doing an implicit commit. All
3299          * atomic levels *must* be explicitly closed using DatabaseBase::endAtomic(),
3300          * and any database transactions cannot be began or committed until all atomic
3301          * levels are closed. There is no such thing as implicitly opening or closing
3302          * an atomic section.
3303          *
3304          * @since 1.23
3305          * @param string $fname
3306          * @throws DBError
3307          */
3308         final public function startAtomic( $fname = __METHOD__ ) {
3309                 if ( !$this->mTrxLevel ) {
3310                         $this->begin( $fname );
3311                         $this->mTrxAutomatic = true;
3312                         $this->mTrxAutomaticAtomic = true;
3313                 }
3314
3315                 $this->mTrxAtomicLevels->push( $fname );
3316         }
3317
3318         /**
3319          * Ends an atomic section of SQL statements
3320          *
3321          * Ends the next section of atomic SQL statements and commits the transaction
3322          * if necessary.
3323          *
3324          * @since 1.23
3325          * @see DatabaseBase::startAtomic
3326          * @param string $fname
3327          * @throws DBError
3328          */
3329         final public function endAtomic( $fname = __METHOD__ ) {
3330                 if ( !$this->mTrxLevel ) {
3331                         throw new DBUnexpectedError( $this, 'No atomic transaction is open.' );
3332                 }
3333                 if ( $this->mTrxAtomicLevels->isEmpty() ||
3334                         $this->mTrxAtomicLevels->pop() !== $fname
3335                 ) {
3336                         throw new DBUnexpectedError( $this, 'Invalid atomic section ended.' );
3337                 }
3338
3339                 if ( $this->mTrxAtomicLevels->isEmpty() && $this->mTrxAutomaticAtomic ) {
3340                         $this->commit( $fname, 'flush' );
3341                 }
3342         }
3343
3344         /**
3345          * Begin a transaction. If a transaction is already in progress,
3346          * that transaction will be committed before the new transaction is started.
3347          *
3348          * Note that when the DBO_TRX flag is set (which is usually the case for web
3349          * requests, but not for maintenance scripts), any previous database query
3350          * will have started a transaction automatically.
3351          *
3352          * Nesting of transactions is not supported. Attempts to nest transactions
3353          * will cause a warning, unless the current transaction was started
3354          * automatically because of the DBO_TRX flag.
3355          *
3356          * @param string $fname
3357          * @throws DBError
3358          */
3359         final public function begin( $fname = __METHOD__ ) {
3360                 global $wgDebugDBTransactions;
3361
3362                 if ( $this->mTrxLevel ) { // implicit commit
3363                         if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3364                                 // If the current transaction was an automatic atomic one, then we definitely have
3365                                 // a problem. Same if there is any unclosed atomic level.
3366                                 throw new DBUnexpectedError( $this,
3367                                         "Attempted to start explicit transaction when atomic levels are still open."
3368                                 );
3369                         } elseif ( !$this->mTrxAutomatic ) {
3370                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3371                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3372                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3373                                         " performing implicit commit!";
3374                                 wfWarn( $msg );
3375                                 wfLogDBError( $msg,
3376                                         $this->getLogContext( array(
3377                                                 'method' => __METHOD__,
3378                                                 'fname' => $fname,
3379                                         ) )
3380                                 );
3381                         } else {
3382                                 // if the transaction was automatic and has done write operations,
3383                                 // log it if $wgDebugDBTransactions is enabled.
3384                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3385                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3386                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3387                                         );
3388                                 }
3389                         }
3390
3391                         $this->runOnTransactionPreCommitCallbacks();
3392                         $this->doCommit( $fname );
3393                         if ( $this->mTrxDoneWrites ) {
3394                                 Profiler::instance()->getTransactionProfiler()->transactionWritingOut(
3395                                         $this->mServer, $this->mDBname, $this->mTrxShortId );
3396                         }
3397                         $this->runOnTransactionIdleCallbacks();
3398                 }
3399
3400                 # Avoid fatals if close() was called
3401                 if ( !$this->isOpen() ) {
3402                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3403                 }
3404
3405                 $this->doBegin( $fname );
3406                 $this->mTrxTimestamp = microtime( true );
3407                 $this->mTrxFname = $fname;
3408                 $this->mTrxDoneWrites = false;
3409                 $this->mTrxAutomatic = false;
3410                 $this->mTrxAutomaticAtomic = false;
3411                 $this->mTrxAtomicLevels = new SplStack;
3412                 $this->mTrxIdleCallbacks = array();
3413                 $this->mTrxPreCommitCallbacks = array();
3414                 $this->mTrxShortId = wfRandomString( 12 );
3415         }
3416
3417         /**
3418          * Issues the BEGIN command to the database server.
3419          *
3420          * @see DatabaseBase::begin()
3421          * @param string $fname
3422          */
3423         protected function doBegin( $fname ) {
3424                 $this->query( 'BEGIN', $fname );
3425                 $this->mTrxLevel = 1;
3426         }
3427
3428         /**
3429          * Commits a transaction previously started using begin().
3430          * If no transaction is in progress, a warning is issued.
3431          *
3432          * Nesting of transactions is not supported.
3433          *
3434          * @param string $fname
3435          * @param string $flush Flush flag, set to 'flush' to disable warnings about
3436          *   explicitly committing implicit transactions, or calling commit when no
3437          *   transaction is in progress. This will silently break any ongoing
3438          *   explicit transaction. Only set the flush flag if you are sure that it
3439          *   is safe to ignore these warnings in your context.
3440          * @throws DBUnexpectedError
3441          */
3442         final public function commit( $fname = __METHOD__, $flush = '' ) {
3443                 if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3444                         // There are still atomic sections open. This cannot be ignored
3445                         throw new DBUnexpectedError(
3446                                 $this,
3447                                 "Attempted to commit transaction while atomic sections are still open"
3448                         );
3449                 }
3450
3451                 if ( $flush === 'flush' ) {
3452                         if ( !$this->mTrxLevel ) {
3453                                 return; // nothing to do
3454                         } elseif ( !$this->mTrxAutomatic ) {
3455                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3456                         }
3457                 } else {
3458                         if ( !$this->mTrxLevel ) {
3459                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3460                                 return; // nothing to do
3461                         } elseif ( $this->mTrxAutomatic ) {
3462                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3463                         }
3464                 }
3465
3466                 # Avoid fatals if close() was called
3467                 if ( !$this->isOpen() ) {
3468                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3469                 }
3470
3471                 $this->runOnTransactionPreCommitCallbacks();
3472                 $this->doCommit( $fname );
3473                 if ( $this->mTrxDoneWrites ) {
3474                         Profiler::instance()->getTransactionProfiler()->transactionWritingOut(
3475                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
3476                 }
3477                 $this->runOnTransactionIdleCallbacks();
3478         }
3479
3480         /**
3481          * Issues the COMMIT command to the database server.
3482          *
3483          * @see DatabaseBase::commit()
3484          * @param string $fname
3485          */
3486         protected function doCommit( $fname ) {
3487                 if ( $this->mTrxLevel ) {
3488                         $this->query( 'COMMIT', $fname );
3489                         $this->mTrxLevel = 0;
3490                 }
3491         }
3492
3493         /**
3494          * Rollback a transaction previously started using begin().
3495          * If no transaction is in progress, a warning is issued.
3496          *
3497          * No-op on non-transactional databases.
3498          *
3499          * @param string $fname
3500          * @param string $flush Flush flag, set to 'flush' to disable warnings about
3501          *   calling rollback when no transaction is in progress. This will silently
3502          *   break any ongoing explicit transaction. Only set the flush flag if you
3503          *   are sure that it is safe to ignore these warnings in your context.
3504          * @since 1.23 Added $flush parameter
3505          */
3506         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3507                 if ( $flush !== 'flush' ) {
3508                         if ( !$this->mTrxLevel ) {
3509                                 wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3510                                 return; // nothing to do
3511                         } elseif ( $this->mTrxAutomatic ) {
3512                                 wfWarn( "$fname: Explicit rollback of implicit transaction. Something may be out of sync!" );
3513                         }
3514                 } else {
3515                         if ( !$this->mTrxLevel ) {
3516                                 return; // nothing to do
3517                         } elseif ( !$this->mTrxAutomatic ) {
3518                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3519                         }
3520                 }
3521
3522                 # Avoid fatals if close() was called
3523                 if ( !$this->isOpen() ) {
3524                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3525                 }
3526
3527                 $this->doRollback( $fname );
3528                 $this->mTrxIdleCallbacks = array(); // cancel
3529                 $this->mTrxPreCommitCallbacks = array(); // cancel
3530                 $this->mTrxAtomicLevels = new SplStack;
3531                 if ( $this->mTrxDoneWrites ) {
3532                         Profiler::instance()->getTransactionProfiler()->transactionWritingOut(
3533                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
3534                 }
3535         }
3536
3537         /**
3538          * Issues the ROLLBACK command to the database server.
3539          *
3540          * @see DatabaseBase::rollback()
3541          * @param string $fname
3542          */
3543         protected function doRollback( $fname ) {
3544                 if ( $this->mTrxLevel ) {
3545                         $this->query( 'ROLLBACK', $fname, true );
3546                         $this->mTrxLevel = 0;
3547                 }
3548         }
3549
3550         /**
3551          * Creates a new table with structure copied from existing table
3552          * Note that unlike most database abstraction functions, this function does not
3553          * automatically append database prefix, because it works at a lower
3554          * abstraction level.
3555          * The table names passed to this function shall not be quoted (this
3556          * function calls addIdentifierQuotes when needed).
3557          *
3558          * @param string $oldName Name of table whose structure should be copied
3559          * @param string $newName Name of table to be created
3560          * @param bool $temporary Whether the new table should be temporary
3561          * @param string $fname Calling function name
3562          * @throws MWException
3563          * @return bool True if operation was successful
3564          */
3565         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3566                 $fname = __METHOD__
3567         ) {
3568                 throw new MWException(
3569                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3570         }
3571
3572         /**
3573          * List all tables on the database
3574          *
3575          * @param string $prefix Only show tables with this prefix, e.g. mw_
3576          * @param string $fname Calling function name
3577          * @throws MWException
3578          */
3579         function listTables( $prefix = null, $fname = __METHOD__ ) {
3580                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3581         }
3582
3583         /**
3584          * Reset the views process cache set by listViews()
3585          * @since 1.22
3586          */
3587         final public function clearViewsCache() {
3588                 $this->allViews = null;
3589         }
3590
3591         /**
3592          * Lists all the VIEWs in the database
3593          *
3594          * For caching purposes the list of all views should be stored in
3595          * $this->allViews. The process cache can be cleared with clearViewsCache()
3596          *
3597          * @param string $prefix Only show VIEWs with this prefix, eg. unit_test_
3598          * @param string $fname Name of calling function
3599          * @throws MWException
3600          * @since 1.22
3601          */
3602         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3603                 throw new MWException( 'DatabaseBase::listViews is not implemented in descendant class' );
3604         }
3605
3606         /**
3607          * Differentiates between a TABLE and a VIEW
3608          *
3609          * @param string $name Name of the database-structure to test.
3610          * @throws MWException
3611          * @since 1.22
3612          */
3613         public function isView( $name ) {
3614                 throw new MWException( 'DatabaseBase::isView is not implemented in descendant class' );
3615         }
3616
3617         /**
3618          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3619          * to the format used for inserting into timestamp fields in this DBMS.
3620          *
3621          * The result is unquoted, and needs to be passed through addQuotes()
3622          * before it can be included in raw SQL.
3623          *
3624          * @param string|int $ts
3625          *
3626          * @return string
3627          */
3628         public function timestamp( $ts = 0 ) {
3629                 return wfTimestamp( TS_MW, $ts );
3630         }
3631
3632         /**
3633          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3634          * to the format used for inserting into timestamp fields in this DBMS. If
3635          * NULL is input, it is passed through, allowing NULL values to be inserted
3636          * into timestamp fields.
3637          *
3638          * The result is unquoted, and needs to be passed through addQuotes()
3639          * before it can be included in raw SQL.
3640          *
3641          * @param string|int $ts
3642          *
3643          * @return string
3644          */
3645         public function timestampOrNull( $ts = null ) {
3646                 if ( is_null( $ts ) ) {
3647                         return null;
3648                 } else {
3649                         return $this->timestamp( $ts );
3650                 }
3651         }
3652
3653         /**
3654          * Take the result from a query, and wrap it in a ResultWrapper if
3655          * necessary. Boolean values are passed through as is, to indicate success
3656          * of write queries or failure.
3657          *
3658          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3659          * resource, and it was necessary to call this function to convert it to
3660          * a wrapper. Nowadays, raw database objects are never exposed to external
3661          * callers, so this is unnecessary in external code. For compatibility with
3662          * old code, ResultWrapper objects are passed through unaltered.
3663          *
3664          * @param bool|ResultWrapper|resource $result
3665          * @return bool|ResultWrapper
3666          */
3667         public function resultObject( $result ) {
3668                 if ( empty( $result ) ) {
3669                         return false;
3670                 } elseif ( $result instanceof ResultWrapper ) {
3671                         return $result;
3672                 } elseif ( $result === true ) {
3673                         // Successful write query
3674                         return $result;
3675                 } else {
3676                         return new ResultWrapper( $this, $result );
3677                 }
3678         }
3679
3680         /**
3681          * Ping the server and try to reconnect if it there is no connection
3682          *
3683          * @return bool Success or failure
3684          */
3685         public function ping() {
3686                 # Stub. Not essential to override.
3687                 return true;
3688         }
3689
3690         /**
3691          * Get slave lag. Currently supported only by MySQL.
3692          *
3693          * Note that this function will generate a fatal error on many
3694          * installations. Most callers should use LoadBalancer::safeGetLag()
3695          * instead.
3696          *
3697          * @return int Database replication lag in seconds
3698          */
3699         public function getLag() {
3700                 return 0;
3701         }
3702
3703         /**
3704          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3705          *
3706          * @return int
3707          */
3708         function maxListLen() {
3709                 return 0;
3710         }
3711
3712         /**
3713          * Some DBMSs have a special format for inserting into blob fields, they
3714          * don't allow simple quoted strings to be inserted. To insert into such
3715          * a field, pass the data through this function before passing it to
3716          * DatabaseBase::insert().
3717          *
3718          * @param string $b
3719          * @return string
3720          */
3721         public function encodeBlob( $b ) {
3722                 return $b;
3723         }
3724
3725         /**
3726          * Some DBMSs return a special placeholder object representing blob fields
3727          * in result objects. Pass the object through this function to return the
3728          * original string.
3729          *
3730          * @param string $b
3731          * @return string
3732          */
3733         public function decodeBlob( $b ) {
3734                 return $b;
3735         }
3736
3737         /**
3738          * Override database's default behavior. $options include:
3739          *     'connTimeout' : Set the connection timeout value in seconds.
3740          *                     May be useful for very long batch queries such as
3741          *                     full-wiki dumps, where a single query reads out over
3742          *                     hours or days.
3743          *
3744          * @param array $options
3745          * @return void
3746          */
3747         public function setSessionOptions( array $options ) {
3748         }
3749
3750         /**
3751          * Read and execute SQL commands from a file.
3752          *
3753          * Returns true on success, error string or exception on failure (depending
3754          * on object's error ignore settings).
3755          *
3756          * @param string $filename File name to open
3757          * @param bool|callable $lineCallback Optional function called before reading each line
3758          * @param bool|callable $resultCallback Optional function called for each MySQL result
3759          * @param bool|string $fname Calling function name or false if name should be
3760          *   generated dynamically using $filename
3761          * @param bool|callable $inputCallback Optional function called for each
3762          *   complete line sent
3763          * @throws Exception|MWException
3764          * @return bool|string
3765          */
3766         public function sourceFile(
3767                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3768         ) {
3769                 wfSuppressWarnings();
3770                 $fp = fopen( $filename, 'r' );
3771                 wfRestoreWarnings();
3772
3773                 if ( false === $fp ) {
3774                         throw new MWException( "Could not open \"{$filename}\".\n" );
3775                 }
3776
3777                 if ( !$fname ) {
3778                         $fname = __METHOD__ . "( $filename )";
3779                 }
3780
3781                 try {
3782                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3783                 } catch ( MWException $e ) {
3784                         fclose( $fp );
3785                         throw $e;
3786                 }
3787
3788                 fclose( $fp );
3789
3790                 return $error;
3791         }
3792
3793         /**
3794          * Get the full path of a patch file. Originally based on archive()
3795          * from updaters.inc. Keep in mind this always returns a patch, as
3796          * it fails back to MySQL if no DB-specific patch can be found
3797          *
3798          * @param string $patch The name of the patch, like patch-something.sql
3799          * @return string Full path to patch file
3800          */
3801         public function patchPath( $patch ) {
3802                 global $IP;
3803
3804                 $dbType = $this->getType();
3805                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3806                         return "$IP/maintenance/$dbType/archives/$patch";
3807                 } else {
3808                         return "$IP/maintenance/archives/$patch";
3809                 }
3810         }
3811
3812         /**
3813          * Set variables to be used in sourceFile/sourceStream, in preference to the
3814          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3815          * all. If it's set to false, $GLOBALS will be used.
3816          *
3817          * @param bool|array $vars Mapping variable name to value.
3818          */
3819         public function setSchemaVars( $vars ) {
3820                 $this->mSchemaVars = $vars;
3821         }
3822
3823         /**
3824          * Read and execute commands from an open file handle.
3825          *
3826          * Returns true on success, error string or exception on failure (depending
3827          * on object's error ignore settings).
3828          *
3829          * @param resource $fp File handle
3830          * @param bool|callable $lineCallback Optional function called before reading each query
3831          * @param bool|callable $resultCallback Optional function called for each MySQL result
3832          * @param string $fname Calling function name
3833          * @param bool|callable $inputCallback Optional function called for each complete query sent
3834          * @return bool|string
3835          */
3836         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3837                 $fname = __METHOD__, $inputCallback = false
3838         ) {
3839                 $cmd = '';
3840
3841                 while ( !feof( $fp ) ) {
3842                         if ( $lineCallback ) {
3843                                 call_user_func( $lineCallback );
3844                         }
3845
3846                         $line = trim( fgets( $fp ) );
3847
3848                         if ( $line == '' ) {
3849                                 continue;
3850                         }
3851
3852                         if ( '-' == $line[0] && '-' == $line[1] ) {
3853                                 continue;
3854                         }
3855
3856                         if ( $cmd != '' ) {
3857                                 $cmd .= ' ';
3858                         }
3859
3860                         $done = $this->streamStatementEnd( $cmd, $line );
3861
3862                         $cmd .= "$line\n";
3863
3864                         if ( $done || feof( $fp ) ) {
3865                                 $cmd = $this->replaceVars( $cmd );
3866
3867                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3868                                         $res = $this->query( $cmd, $fname );
3869
3870                                         if ( $resultCallback ) {
3871                                                 call_user_func( $resultCallback, $res, $this );
3872                                         }
3873
3874                                         if ( false === $res ) {
3875                                                 $err = $this->lastError();
3876
3877                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3878                                         }
3879                                 }
3880                                 $cmd = '';
3881                         }
3882                 }
3883
3884                 return true;
3885         }
3886
3887         /**
3888          * Called by sourceStream() to check if we've reached a statement end
3889          *
3890          * @param string $sql SQL assembled so far
3891          * @param string $newLine New line about to be added to $sql
3892          * @return bool Whether $newLine contains end of the statement
3893          */
3894         public function streamStatementEnd( &$sql, &$newLine ) {
3895                 if ( $this->delimiter ) {
3896                         $prev = $newLine;
3897                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3898                         if ( $newLine != $prev ) {
3899                                 return true;
3900                         }
3901                 }
3902
3903                 return false;
3904         }
3905
3906         /**
3907          * Database independent variable replacement. Replaces a set of variables
3908          * in an SQL statement with their contents as given by $this->getSchemaVars().
3909          *
3910          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3911          *
3912          * - '{$var}' should be used for text and is passed through the database's
3913          *   addQuotes method.
3914          * - `{$var}` should be used for identifiers (eg: table and database names),
3915          *   it is passed through the database's addIdentifierQuotes method which
3916          *   can be overridden if the database uses something other than backticks.
3917          * - / *$var* / is just encoded, besides traditional table prefix and
3918          *   table options its use should be avoided.
3919          *
3920          * @param string $ins SQL statement to replace variables in
3921          * @return string The new SQL statement with variables replaced
3922          */
3923         protected function replaceSchemaVars( $ins ) {
3924                 $vars = $this->getSchemaVars();
3925                 foreach ( $vars as $var => $value ) {
3926                         // replace '{$var}'
3927                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3928                         // replace `{$var}`
3929                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3930                         // replace /*$var*/
3931                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3932                 }
3933
3934                 return $ins;
3935         }
3936
3937         /**
3938          * Replace variables in sourced SQL
3939          *
3940          * @param string $ins
3941          * @return string
3942          */
3943         protected function replaceVars( $ins ) {
3944                 $ins = $this->replaceSchemaVars( $ins );
3945
3946                 // Table prefixes
3947                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3948                         array( $this, 'tableNameCallback' ), $ins );
3949
3950                 // Index names
3951                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3952                         array( $this, 'indexNameCallback' ), $ins );
3953
3954                 return $ins;
3955         }
3956
3957         /**
3958          * Get schema variables. If none have been set via setSchemaVars(), then
3959          * use some defaults from the current object.
3960          *
3961          * @return array
3962          */
3963         protected function getSchemaVars() {
3964                 if ( $this->mSchemaVars ) {
3965                         return $this->mSchemaVars;
3966                 } else {
3967                         return $this->getDefaultSchemaVars();
3968                 }
3969         }
3970
3971         /**
3972          * Get schema variables to use if none have been set via setSchemaVars().
3973          *
3974          * Override this in derived classes to provide variables for tables.sql
3975          * and SQL patch files.
3976          *
3977          * @return array
3978          */
3979         protected function getDefaultSchemaVars() {
3980                 return array();
3981         }
3982
3983         /**
3984          * Table name callback
3985          *
3986          * @param array $matches
3987          * @return string
3988          */
3989         protected function tableNameCallback( $matches ) {
3990                 return $this->tableName( $matches[1] );
3991         }
3992
3993         /**
3994          * Index name callback
3995          *
3996          * @param array $matches
3997          * @return string
3998          */
3999         protected function indexNameCallback( $matches ) {
4000                 return $this->indexName( $matches[1] );
4001         }
4002
4003         /**
4004          * Check to see if a named lock is available. This is non-blocking.
4005          *
4006          * @param string $lockName Name of lock to poll
4007          * @param string $method Name of method calling us
4008          * @return bool
4009          * @since 1.20
4010          */
4011         public function lockIsFree( $lockName, $method ) {
4012                 return true;
4013         }
4014
4015         /**
4016          * Acquire a named lock
4017          *
4018          * Abstracted from Filestore::lock() so child classes can implement for
4019          * their own needs.
4020          *
4021          * @param string $lockName Name of lock to aquire
4022          * @param string $method Name of method calling us
4023          * @param int $timeout
4024          * @return bool
4025          */
4026         public function lock( $lockName, $method, $timeout = 5 ) {
4027                 return true;
4028         }
4029
4030         /**
4031          * Release a lock.
4032          *
4033          * @param string $lockName Name of lock to release
4034          * @param string $method Name of method calling us
4035          *
4036          * @return int Returns 1 if the lock was released, 0 if the lock was not established
4037          * by this thread (in which case the lock is not released), and NULL if the named
4038          * lock did not exist
4039          */
4040         public function unlock( $lockName, $method ) {
4041                 return true;
4042         }
4043
4044         /**
4045          * Lock specific tables
4046          *
4047          * @param array $read Array of tables to lock for read access
4048          * @param array $write Array of tables to lock for write access
4049          * @param string $method Name of caller
4050          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
4051          * @return bool
4052          */
4053         public function lockTables( $read, $write, $method, $lowPriority = true ) {
4054                 return true;
4055         }
4056
4057         /**
4058          * Unlock specific tables
4059          *
4060          * @param string $method The caller
4061          * @return bool
4062          */
4063         public function unlockTables( $method ) {
4064                 return true;
4065         }
4066
4067         /**
4068          * Delete a table
4069          * @param string $tableName
4070          * @param string $fName
4071          * @return bool|ResultWrapper
4072          * @since 1.18
4073          */
4074         public function dropTable( $tableName, $fName = __METHOD__ ) {
4075                 if ( !$this->tableExists( $tableName, $fName ) ) {
4076                         return false;
4077                 }
4078                 $sql = "DROP TABLE " . $this->tableName( $tableName );
4079                 if ( $this->cascadingDeletes() ) {
4080                         $sql .= " CASCADE";
4081                 }
4082
4083                 return $this->query( $sql, $fName );
4084         }
4085
4086         /**
4087          * Get search engine class. All subclasses of this need to implement this
4088          * if they wish to use searching.
4089          *
4090          * @return string
4091          */
4092         public function getSearchEngine() {
4093                 return 'SearchEngineDummy';
4094         }
4095
4096         /**
4097          * Find out when 'infinity' is. Most DBMSes support this. This is a special
4098          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
4099          * because "i" sorts after all numbers.
4100          *
4101          * @return string
4102          */
4103         public function getInfinity() {
4104                 return 'infinity';
4105         }
4106
4107         /**
4108          * Encode an expiry time into the DBMS dependent format
4109          *
4110          * @param string $expiry Timestamp for expiry, or the 'infinity' string
4111          * @return string
4112          */
4113         public function encodeExpiry( $expiry ) {
4114                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4115                         ? $this->getInfinity()
4116                         : $this->timestamp( $expiry );
4117         }
4118
4119         /**
4120          * Decode an expiry time into a DBMS independent format
4121          *
4122          * @param string $expiry DB timestamp field value for expiry
4123          * @param int $format TS_* constant, defaults to TS_MW
4124          * @return string
4125          */
4126         public function decodeExpiry( $expiry, $format = TS_MW ) {
4127                 return ( $expiry == '' || $expiry == $this->getInfinity() )
4128                         ? 'infinity'
4129                         : wfTimestamp( $format, $expiry );
4130         }
4131
4132         /**
4133          * Allow or deny "big selects" for this session only. This is done by setting
4134          * the sql_big_selects session variable.
4135          *
4136          * This is a MySQL-specific feature.
4137          *
4138          * @param bool|string $value True for allow, false for deny, or "default" to
4139          *   restore the initial value
4140          */
4141         public function setBigSelects( $value = true ) {
4142                 // no-op
4143         }
4144
4145         /**
4146          * @since 1.19
4147          * @return string
4148          */
4149         public function __toString() {
4150                 return (string)$this->mConn;
4151         }
4152
4153         /**
4154          * Run a few simple sanity checks
4155          */
4156         public function __destruct() {
4157                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
4158                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
4159                 }
4160                 if ( count( $this->mTrxIdleCallbacks ) || count( $this->mTrxPreCommitCallbacks ) ) {
4161                         $callers = array();
4162                         foreach ( $this->mTrxIdleCallbacks as $callbackInfo ) {
4163                                 $callers[] = $callbackInfo[1];
4164                         }
4165                         $callers = implode( ', ', $callers );
4166                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
4167                 }
4168         }
4169 }