includes/db/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * This file deals with database interface functions
   6  * and query specifics/optimisations.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Database
  25  */
  26
  27 /**
  28  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  29  * following must be implemented to support MediaWiki
  30  *
  31  * @file
  32  * @ingroup Database
  33  */
  34 interface DatabaseType {
  35         /**
  36          * Get the type of the DBMS, as it appears in $wgDBtype.
  37          *
  38          * @return string
  39          */
  40         function getType();
  41
  42         /**
  43          * Open a connection to the database. Usually aborts on failure
  44          *
  45          * @param string $server database server host
  46          * @param string $user database user name
  47          * @param string $password database user password
  48          * @param string $dbName database name
  49          * @return bool
  50          * @throws DBConnectionError
  51          */
  52         function open( $server, $user, $password, $dbName );
  53
  54         /**
  55          * Fetch the next row from the given result object, in object form.
  56          * Fields can be retrieved with $row->fieldname, with fields acting like
  57          * member variables.
  58          * If no more rows are available, false is returned.
  59          *
  60          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  61          * @return object|bool
  62          * @throws DBUnexpectedError Thrown if the database returns an error
  63          */
  64         function fetchObject( $res );
  65
  66         /**
  67          * Fetch the next row from the given result object, in associative array
  68          * form.  Fields are retrieved with $row['fieldname'].
  69          * If no more rows are available, false is returned.
  70          *
  71          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  72          * @return array|bool
  73          * @throws DBUnexpectedError Thrown if the database returns an error
  74          */
  75         function fetchRow( $res );
  76
  77         /**
  78          * Get the number of rows in a result object
  79          *
  80          * @param $res Mixed: A SQL result
  81          * @return int
  82          */
  83         function numRows( $res );
  84
  85         /**
  86          * Get the number of fields in a result object
  87          * @see http://www.php.net/mysql_num_fields
  88          *
  89          * @param $res Mixed: A SQL result
  90          * @return int
  91          */
  92         function numFields( $res );
  93
  94         /**
  95          * Get a field name in a result object
  96          * @see http://www.php.net/mysql_field_name
  97          *
  98          * @param $res Mixed: A SQL result
  99          * @param $n Integer
 100          * @return string
 101          */
 102         function fieldName( $res, $n );
 103
 104         /**
 105          * Get the inserted value of an auto-increment row
 106          *
 107          * The value inserted should be fetched from nextSequenceValue()
 108          *
 109          * Example:
 110          * $id = $dbw->nextSequenceValue( 'page_page_id_seq' );
 111          * $dbw->insert( 'page', array( 'page_id' => $id ) );
 112          * $id = $dbw->insertId();
 113          *
 114          * @return int
 115          */
 116         function insertId();
 117
 118         /**
 119          * Change the position of the cursor in a result object
 120          * @see http://www.php.net/mysql_data_seek
 121          *
 122          * @param $res Mixed: A SQL result
 123          * @param $row Mixed: Either MySQL row or ResultWrapper
 124          */
 125         function dataSeek( $res, $row );
 126
 127         /**
 128          * Get the last error number
 129          * @see http://www.php.net/mysql_errno
 130          *
 131          * @return int
 132          */
 133         function lastErrno();
 134
 135         /**
 136          * Get a description of the last error
 137          * @see http://www.php.net/mysql_error
 138          *
 139          * @return string
 140          */
 141         function lastError();
 142
 143         /**
 144          * mysql_fetch_field() wrapper
 145          * Returns false if the field doesn't exist
 146          *
 147          * @param string $table table name
 148          * @param string $field field name
 149          *
 150          * @return Field
 151          */
 152         function fieldInfo( $table, $field );
 153
 154         /**
 155          * Get information about an index into an object
 156          * @param string $table Table name
 157          * @param string $index Index name
 158          * @param string $fname Calling function name
 159          * @return Mixed: Database-specific index description class or false if the index does not exist
 160          */
 161         function indexInfo( $table, $index, $fname = __METHOD__ );
 162
 163         /**
 164          * Get the number of rows affected by the last write query
 165          * @see http://www.php.net/mysql_affected_rows
 166          *
 167          * @return int
 168          */
 169         function affectedRows();
 170
 171         /**
 172          * Wrapper for addslashes()
 173          *
 174          * @param string $s to be slashed.
 175          * @return string: slashed string.
 176          */
 177         function strencode( $s );
 178
 179         /**
 180          * Returns a wikitext link to the DB's website, e.g.,
 181          *     return "[http://www.mysql.com/ MySQL]";
 182          * Should at least contain plain text, if for some reason
 183          * your database has no website.
 184          *
 185          * @return string: wikitext of a link to the server software's web site
 186          */
 187         function getSoftwareLink();
 188
 189         /**
 190          * A string describing the current software version, like from
 191          * mysql_get_server_info().
 192          *
 193          * @return string: Version information from the database server.
 194          */
 195         function getServerVersion();
 196
 197         /**
 198          * A string describing the current software version, and possibly
 199          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 200          * Use getServerVersion() to get machine-friendly information.
 201          *
 202          * @return string: Version information from the database server
 203          */
 204         function getServerInfo();
 205 }
 206
 207 /**
 208  * Interface for classes that implement or wrap DatabaseBase
 209  * @ingroup Database
 210  */
 211 interface IDatabase {}
 212
 213 /**
 214  * Database abstraction object
 215  * @ingroup Database
 216  */
 217 abstract class DatabaseBase implements IDatabase, DatabaseType {
 218         /** Number of times to re-try an operation in case of deadlock */
 219         const DEADLOCK_TRIES = 4;
 220         /** Minimum time to wait before retry, in microseconds */
 221         const DEADLOCK_DELAY_MIN = 500000;
 222         /** Maximum time to wait before retry */
 223         const DEADLOCK_DELAY_MAX = 1500000;
 224
 225 # ------------------------------------------------------------------------------
 226 # Variables
 227 # ------------------------------------------------------------------------------
 228
 229         protected $mLastQuery = '';
 230         protected $mDoneWrites = false;
 231         protected $mPHPError = false;
 232
 233         protected $mServer, $mUser, $mPassword, $mDBname;
 234
 235         protected $mConn = null;
 236         protected $mOpened = false;
 237
 238         /** @var callable[] */
 239         protected $mTrxIdleCallbacks = array();
 240         /** @var callable[] */
 241         protected $mTrxPreCommitCallbacks = array();
 242
 243         protected $mTablePrefix;
 244         protected $mFlags;
 245         protected $mForeign;
 246         protected $mTrxLevel = 0;
 247         protected $mErrorCount = 0;
 248         protected $mLBInfo = array();
 249         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 250         protected $mDefaultBigSelects = null;
 251         protected $mSchemaVars = false;
 252
 253         protected $preparedArgs;
 254
 255         protected $htmlErrors;
 256
 257         protected $delimiter = ';';
 258
 259         /**
 260          * Remembers the function name given for starting the most recent transaction via begin().
 261          * Used to provide additional context for error reporting.
 262          *
 263          * @var String
 264          * @see DatabaseBase::mTrxLevel
 265          */
 266         private $mTrxFname = null;
 267
 268         /**
 269          * Record if possible write queries were done in the last transaction started
 270          *
 271          * @var Bool
 272          * @see DatabaseBase::mTrxLevel
 273          */
 274         private $mTrxDoneWrites = false;
 275
 276         /**
 277          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 278          *
 279          * @var Bool
 280          * @see DatabaseBase::mTrxLevel
 281          */
 282         private $mTrxAutomatic = false;
 283
 284         /**
 285          * Array of levels of atomicity within transactions
 286          *
 287          * @var SplStack
 288          */
 289         private $mTrxAtomicLevels;
 290
 291         /**
 292          * Record if the current transaction was started implicitly by DatabaseBase::startAtomic
 293          *
 294          * @var Bool
 295          */
 296         private $mTrxAutomaticAtomic = false;
 297
 298         /**
 299          * @since 1.21
 300          * @var file handle for upgrade
 301          */
 302         protected $fileHandle = null;
 303
 304 # ------------------------------------------------------------------------------
 305 # Accessors
 306 # ------------------------------------------------------------------------------
 307         # These optionally set a variable and return the previous state
 308
 309         /**
 310          * A string describing the current software version, and possibly
 311          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 312          * Use getServerVersion() to get machine-friendly information.
 313          *
 314          * @return string: Version information from the database server
 315          */
 316         public function getServerInfo() {
 317                 return $this->getServerVersion();
 318         }
 319
 320         /**
 321          * @return string: command delimiter used by this database engine
 322          */
 323         public function getDelimiter() {
 324                 return $this->delimiter;
 325         }
 326
 327         /**
 328          * Boolean, controls output of large amounts of debug information.
 329          * @param $debug bool|null
 330          *   - true to enable debugging
 331          *   - false to disable debugging
 332          *   - omitted or null to do nothing
 333          *
 334          * @return bool|null previous value of the flag
 335          */
 336         public function debug( $debug = null ) {
 337                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 338         }
 339
 340         /**
 341          * Turns buffering of SQL result sets on (true) or off (false). Default is
 342          * "on".
 343          *
 344          * Unbuffered queries are very troublesome in MySQL:
 345          *
 346          *   - If another query is executed while the first query is being read
 347          *     out, the first query is killed. This means you can't call normal
 348          *     MediaWiki functions while you are reading an unbuffered query result
 349          *     from a normal wfGetDB() connection.
 350          *
 351          *   - Unbuffered queries cause the MySQL server to use large amounts of
 352          *     memory and to hold broad locks which block other queries.
 353          *
 354          * If you want to limit client-side memory, it's almost always better to
 355          * split up queries into batches using a LIMIT clause than to switch off
 356          * buffering.
 357          *
 358          * @param $buffer null|bool
 359          *
 360          * @return null|bool The previous value of the flag
 361          */
 362         public function bufferResults( $buffer = null ) {
 363                 if ( is_null( $buffer ) ) {
 364                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 365                 } else {
 366                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 367                 }
 368         }
 369
 370         /**
 371          * Turns on (false) or off (true) the automatic generation and sending
 372          * of a "we're sorry, but there has been a database error" page on
 373          * database errors. Default is on (false). When turned off, the
 374          * code should use lastErrno() and lastError() to handle the
 375          * situation as appropriate.
 376          *
 377          * Do not use this function outside of the Database classes.
 378          *
 379          * @param $ignoreErrors bool|null
 380          *
 381          * @return bool The previous value of the flag.
 382          */
 383         public function ignoreErrors( $ignoreErrors = null ) {
 384                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 385         }
 386
 387         /**
 388          * Gets or sets the current transaction level.
 389          *
 390          * Historically, transactions were allowed to be "nested". This is no
 391          * longer supported, so this function really only returns a boolean.
 392          *
 393          * @param int $level An integer (0 or 1), or omitted to leave it unchanged.
 394          * @return int The previous value
 395          */
 396         public function trxLevel( $level = null ) {
 397                 return wfSetVar( $this->mTrxLevel, $level );
 398         }
 399
 400         /**
 401          * Get/set the number of errors logged. Only useful when errors are ignored
 402          * @param int $count The count to set, or omitted to leave it unchanged.
 403          * @return int The error count
 404          */
 405         public function errorCount( $count = null ) {
 406                 return wfSetVar( $this->mErrorCount, $count );
 407         }
 408
 409         /**
 410          * Get/set the table prefix.
 411          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 412          * @return string The previous table prefix.
 413          */
 414         public function tablePrefix( $prefix = null ) {
 415                 return wfSetVar( $this->mTablePrefix, $prefix );
 416         }
 417
 418         /**
 419          * Set the filehandle to copy write statements to.
 420          *
 421          * @param $fh filehandle
 422          */
 423         public function setFileHandle( $fh ) {
 424                 $this->fileHandle = $fh;
 425         }
 426
 427         /**
 428          * Get properties passed down from the server info array of the load
 429          * balancer.
 430          *
 431          * @param string $name The entry of the info array to get, or null to get the
 432          *   whole array
 433          *
 434          * @return LoadBalancer|null
 435          */
 436         public function getLBInfo( $name = null ) {
 437                 if ( is_null( $name ) ) {
 438                         return $this->mLBInfo;
 439                 } else {
 440                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 441                                 return $this->mLBInfo[$name];
 442                         } else {
 443                                 return null;
 444                         }
 445                 }
 446         }
 447
 448         /**
 449          * Set the LB info array, or a member of it. If called with one parameter,
 450          * the LB info array is set to that parameter. If it is called with two
 451          * parameters, the member with the given name is set to the given value.
 452          *
 453          * @param $name
 454          * @param $value
 455          */
 456         public function setLBInfo( $name, $value = null ) {
 457                 if ( is_null( $value ) ) {
 458                         $this->mLBInfo = $name;
 459                 } else {
 460                         $this->mLBInfo[$name] = $value;
 461                 }
 462         }
 463
 464         /**
 465          * Set lag time in seconds for a fake slave
 466          *
 467          * @param $lag int
 468          */
 469         public function setFakeSlaveLag( $lag ) {
 470                 $this->mFakeSlaveLag = $lag;
 471         }
 472
 473         /**
 474          * Make this connection a fake master
 475          *
 476          * @param $enabled bool
 477          */
 478         public function setFakeMaster( $enabled = true ) {
 479                 $this->mFakeMaster = $enabled;
 480         }
 481
 482         /**
 483          * Returns true if this database supports (and uses) cascading deletes
 484          *
 485          * @return bool
 486          */
 487         public function cascadingDeletes() {
 488                 return false;
 489         }
 490
 491         /**
 492          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 493          *
 494          * @return bool
 495          */
 496         public function cleanupTriggers() {
 497                 return false;
 498         }
 499
 500         /**
 501          * Returns true if this database is strict about what can be put into an IP field.
 502          * Specifically, it uses a NULL value instead of an empty string.
 503          *
 504          * @return bool
 505          */
 506         public function strictIPs() {
 507                 return false;
 508         }
 509
 510         /**
 511          * Returns true if this database uses timestamps rather than integers
 512          *
 513          * @return bool
 514          */
 515         public function realTimestamps() {
 516                 return false;
 517         }
 518
 519         /**
 520          * Returns true if this database does an implicit sort when doing GROUP BY
 521          *
 522          * @return bool
 523          */
 524         public function implicitGroupby() {
 525                 return true;
 526         }
 527
 528         /**
 529          * Returns true if this database does an implicit order by when the column has an index
 530          * For example: SELECT page_title FROM page LIMIT 1
 531          *
 532          * @return bool
 533          */
 534         public function implicitOrderby() {
 535                 return true;
 536         }
 537
 538         /**
 539          * Returns true if this database can do a native search on IP columns
 540          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 541          *
 542          * @return bool
 543          */
 544         public function searchableIPs() {
 545                 return false;
 546         }
 547
 548         /**
 549          * Returns true if this database can use functional indexes
 550          *
 551          * @return bool
 552          */
 553         public function functionalIndexes() {
 554                 return false;
 555         }
 556
 557         /**
 558          * Return the last query that went through DatabaseBase::query()
 559          * @return String
 560          */
 561         public function lastQuery() {
 562                 return $this->mLastQuery;
 563         }
 564
 565         /**
 566          * Returns true if the connection may have been used for write queries.
 567          * Should return true if unsure.
 568          *
 569          * @return bool
 570          */
 571         public function doneWrites() {
 572                 return $this->mDoneWrites;
 573         }
 574
 575         /**
 576          * Returns true if there is a transaction open with possible write
 577          * queries or transaction pre-commit/idle callbacks waiting on it to finish.
 578          *
 579          * @return bool
 580          */
 581         public function writesOrCallbacksPending() {
 582                 return $this->mTrxLevel && (
 583                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 584                 );
 585         }
 586
 587         /**
 588          * Is a connection to the database open?
 589          * @return Boolean
 590          */
 591         public function isOpen() {
 592                 return $this->mOpened;
 593         }
 594
 595         /**
 596          * Set a flag for this connection
 597          *
 598          * @param $flag Integer: DBO_* constants from Defines.php:
 599          *   - DBO_DEBUG: output some debug info (same as debug())
 600          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 601          *   - DBO_TRX: automatically start transactions
 602          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 603          *       and removes it in command line mode
 604          *   - DBO_PERSISTENT: use persistant database connection
 605          */
 606         public function setFlag( $flag ) {
 607                 global $wgDebugDBTransactions;
 608                 $this->mFlags |= $flag;
 609                 if ( ( $flag & DBO_TRX ) & $wgDebugDBTransactions ) {
 610                         wfDebug( "Implicit transactions are now  disabled.\n" );
 611                 }
 612         }
 613
 614         /**
 615          * Clear a flag for this connection
 616          *
 617          * @param $flag: same as setFlag()'s $flag param
 618          */
 619         public function clearFlag( $flag ) {
 620                 global $wgDebugDBTransactions;
 621                 $this->mFlags &= ~$flag;
 622                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 623                         wfDebug( "Implicit transactions are now disabled.\n" );
 624                 }
 625         }
 626
 627         /**
 628          * Returns a boolean whether the flag $flag is set for this connection
 629          *
 630          * @param $flag: same as setFlag()'s $flag param
 631          * @return Boolean
 632          */
 633         public function getFlag( $flag ) {
 634                 return !!( $this->mFlags & $flag );
 635         }
 636
 637         /**
 638          * General read-only accessor
 639          *
 640          * @param $name string
 641          *
 642          * @return string
 643          */
 644         public function getProperty( $name ) {
 645                 return $this->$name;
 646         }
 647
 648         /**
 649          * @return string
 650          */
 651         public function getWikiID() {
 652                 if ( $this->mTablePrefix ) {
 653                         return "{$this->mDBname}-{$this->mTablePrefix}";
 654                 } else {
 655                         return $this->mDBname;
 656                 }
 657         }
 658
 659         /**
 660          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 661          *
 662          * @return string
 663          */
 664         public function getSchemaPath() {
 665                 global $IP;
 666                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 667                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 668                 } else {
 669                         return "$IP/maintenance/tables.sql";
 670                 }
 671         }
 672
 673 # ------------------------------------------------------------------------------
 674 # Other functions
 675 # ------------------------------------------------------------------------------
 676
 677         /**
 678          * Constructor.
 679          *
 680          * FIXME: It is possible to construct a Database object with no associated
 681          * connection object, by specifying no parameters to __construct(). This
 682          * feature is deprecated and should be removed.
 683          *
 684          * FIXME: The long list of formal parameters here is not really appropriate
 685          * for MySQL, and not at all appropriate for any other DBMS. It should be
 686          * replaced by named parameters as in DatabaseBase::factory().
 687          *
 688          * DatabaseBase subclasses should not be constructed directly in external
 689          * code. DatabaseBase::factory() should be used instead.
 690          *
 691          * @param string $server database server host
 692          * @param string $user database user name
 693          * @param string $password database user password
 694          * @param string $dbName database name
 695          * @param $flags
 696          * @param string $tablePrefix database table prefixes. By default use the prefix gave in LocalSettings.php
 697          * @param bool $foreign disable some operations specific to local databases
 698          */
 699         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 700                 $flags = 0, $tablePrefix = 'get from global', $foreign = false
 701         ) {
 702                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 703
 704                 $this->mTrxAtomicLevels = new SplStack;
 705                 $this->mFlags = $flags;
 706
 707                 if ( $this->mFlags & DBO_DEFAULT ) {
 708                         if ( $wgCommandLineMode ) {
 709                                 $this->mFlags &= ~DBO_TRX;
 710                                 if ( $wgDebugDBTransactions ) {
 711                                         wfDebug( "Implicit transaction open disabled.\n" );
 712                                 }
 713                         } else {
 714                                 $this->mFlags |= DBO_TRX;
 715                                 if ( $wgDebugDBTransactions ) {
 716                                         wfDebug( "Implicit transaction open enabled.\n" );
 717                                 }
 718                         }
 719                 }
 720
 721                 /** Get the default table prefix*/
 722                 if ( $tablePrefix == 'get from global' ) {
 723                         $this->mTablePrefix = $wgDBprefix;
 724                 } else {
 725                         $this->mTablePrefix = $tablePrefix;
 726                 }
 727
 728                 $this->mForeign = $foreign;
 729
 730                 if ( $user ) {
 731                         $this->open( $server, $user, $password, $dbName );
 732                 }
 733         }
 734
 735         /**
 736          * Called by serialize. Throw an exception when DB connection is serialized.
 737          * This causes problems on some database engines because the connection is
 738          * not restored on unserialize.
 739          */
 740         public function __sleep() {
 741                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 742         }
 743
 744         /**
 745          * Given a DB type, construct the name of the appropriate child class of
 746          * DatabaseBase. This is designed to replace all of the manual stuff like:
 747          *      $class = 'Database' . ucfirst( strtolower( $dbType ) );
 748          * as well as validate against the canonical list of DB types we have
 749          *
 750          * This factory function is mostly useful for when you need to connect to a
 751          * database other than the MediaWiki default (such as for external auth,
 752          * an extension, et cetera). Do not use this to connect to the MediaWiki
 753          * database. Example uses in core:
 754          * @see LoadBalancer::reallyOpenConnection()
 755          * @see ForeignDBRepo::getMasterDB()
 756          * @see WebInstaller_DBConnect::execute()
 757          *
 758          * @since 1.18
 759          *
 760          * @param string $dbType A possible DB type
 761          * @param array $p An array of options to pass to the constructor.
 762          *    Valid options are: host, user, password, dbname, flags, tablePrefix, driver
 763          * @return DatabaseBase subclass or null
 764          */
 765         final public static function factory( $dbType, $p = array() ) {
 766                 $canonicalDBTypes = array(
 767                         'mysql'    => array( 'mysqli', 'mysql' ),
 768                         'postgres' => array(),
 769                         'sqlite'   => array(),
 770                         'oracle'   => array(),
 771                         'mssql'    => array(),
 772                 );
 773
 774                 $driver = false;
 775                 $dbType = strtolower( $dbType );
 776                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 777                         $possibleDrivers = $canonicalDBTypes[$dbType];
 778                         if ( !empty( $p['driver'] ) ) {
 779                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 780                                         $driver = $p['driver'];
 781                                 } else {
 782                                         throw new MWException( __METHOD__ .
 783                                                 " cannot construct Database with type '$dbType' and driver '{$p['driver']}'" );
 784                                 }
 785                         } else {
 786                                 foreach ( $possibleDrivers as $posDriver ) {
 787                                         if ( extension_loaded( $posDriver ) ) {
 788                                                 $driver = $posDriver;
 789                                                 break;
 790                                         }
 791                                 }
 792                         }
 793                 } else {
 794                         $driver = $dbType;
 795                 }
 796                 if ( $driver === false ) {
 797                         throw new MWException( __METHOD__ .
 798                                 " no viable database extension found for type '$dbType'" );
 799                 }
 800
 801                 $class = 'Database' . ucfirst( $driver );
 802                 if ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 803                         return new $class(
 804                                 isset( $p['host'] ) ? $p['host'] : false,
 805                                 isset( $p['user'] ) ? $p['user'] : false,
 806                                 isset( $p['password'] ) ? $p['password'] : false,
 807                                 isset( $p['dbname'] ) ? $p['dbname'] : false,
 808                                 isset( $p['flags'] ) ? $p['flags'] : 0,
 809                                 isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global',
 810                                 isset( $p['foreign'] ) ? $p['foreign'] : false
 811                         );
 812                 } else {
 813                         return null;
 814                 }
 815         }
 816
 817         protected function installErrorHandler() {
 818                 $this->mPHPError = false;
 819                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 820                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 821         }
 822
 823         /**
 824          * @return bool|string
 825          */
 826         protected function restoreErrorHandler() {
 827                 restore_error_handler();
 828                 if ( $this->htmlErrors !== false ) {
 829                         ini_set( 'html_errors', $this->htmlErrors );
 830                 }
 831                 if ( $this->mPHPError ) {
 832                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 833                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 834                         return $error;
 835                 } else {
 836                         return false;
 837                 }
 838         }
 839
 840         /**
 841          * @param $errno
 842          * @param $errstr
 843          * @access private
 844          */
 845         public function connectionErrorHandler( $errno, $errstr ) {
 846                 $this->mPHPError = $errstr;
 847         }
 848
 849         /**
 850          * Closes a database connection.
 851          * if it is open : commits any open transactions
 852          *
 853          * @throws MWException
 854          * @return Bool operation success. true if already closed.
 855          */
 856         public function close() {
 857                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 858                         throw new MWException( "Transaction idle callbacks still pending." );
 859                 }
 860                 $this->mOpened = false;
 861                 if ( $this->mConn ) {
 862                         if ( $this->trxLevel() ) {
 863                                 if ( !$this->mTrxAutomatic ) {
 864                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 865                                                 " performing implicit commit before closing connection!" );
 866                                 }
 867
 868                                 $this->commit( __METHOD__, 'flush' );
 869                         }
 870
 871                         $ret = $this->closeConnection();
 872                         $this->mConn = false;
 873                         return $ret;
 874                 } else {
 875                         return true;
 876                 }
 877         }
 878
 879         /**
 880          * Closes underlying database connection
 881          * @since 1.20
 882          * @return bool: Whether connection was closed successfully
 883          */
 884         abstract protected function closeConnection();
 885
 886         /**
 887          * @param string $error fallback error message, used if none is given by DB
 888          * @throws DBConnectionError
 889          */
 890         function reportConnectionError( $error = 'Unknown error' ) {
 891                 $myError = $this->lastError();
 892                 if ( $myError ) {
 893                         $error = $myError;
 894                 }
 895
 896                 # New method
 897                 throw new DBConnectionError( $this, $error );
 898         }
 899
 900         /**
 901          * The DBMS-dependent part of query()
 902          *
 903          * @param  $sql String: SQL query.
 904          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 905          */
 906         abstract protected function doQuery( $sql );
 907
 908         /**
 909          * Determine whether a query writes to the DB.
 910          * Should return true if unsure.
 911          *
 912          * @param $sql string
 913          *
 914          * @return bool
 915          */
 916         public function isWriteQuery( $sql ) {
 917                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 918         }
 919
 920         /**
 921          * Run an SQL query and return the result. Normally throws a DBQueryError
 922          * on failure. If errors are ignored, returns false instead.
 923          *
 924          * In new code, the query wrappers select(), insert(), update(), delete(),
 925          * etc. should be used where possible, since they give much better DBMS
 926          * independence and automatically quote or validate user input in a variety
 927          * of contexts. This function is generally only useful for queries which are
 928          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 929          * as CREATE TABLE.
 930          *
 931          * However, the query wrappers themselves should call this function.
 932          *
 933          * @param  $sql        String: SQL query
 934          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 935          *     comment (you can use __METHOD__ or add some extra info)
 936          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 937          *     maybe best to catch the exception instead?
 938          * @throws MWException
 939          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 940          *     for a successful read query, or false on failure if $tempIgnore set
 941          */
 942         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 943                 global $wgUser, $wgDebugDBTransactions;
 944
 945                 $this->mLastQuery = $sql;
 946                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 947                         # Set a flag indicating that writes have been done
 948                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 949                         $this->mDoneWrites = true;
 950                 }
 951
 952                 # Add a comment for easy SHOW PROCESSLIST interpretation
 953                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 954                         $userName = $wgUser->getName();
 955                         if ( mb_strlen( $userName ) > 15 ) {
 956                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 957                         }
 958                         $userName = str_replace( '/', '', $userName );
 959                 } else {
 960                         $userName = '';
 961                 }
 962
 963                 // Add trace comment to the begin of the sql string, right after the operator.
 964                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 965                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 966
 967                 # If DBO_TRX is set, start a transaction
 968                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 969                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' )
 970                 {
 971                         # Avoid establishing transactions for SHOW and SET statements too -
 972                         # that would delay transaction initializations to once connection
 973                         # is really used by application
 974                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 975                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 976                                 if ( $wgDebugDBTransactions ) {
 977                                         wfDebug( "Implicit transaction start.\n" );
 978                                 }
 979                                 $this->begin( __METHOD__ . " ($fname)" );
 980                                 $this->mTrxAutomatic = true;
 981                         }
 982                 }
 983
 984                 # Keep track of whether the transaction has write queries pending
 985                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
 986                         $this->mTrxDoneWrites = true;
 987                         Profiler::instance()->transactionWritingIn( $this->mServer, $this->mDBname );
 988                 }
 989
 990                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 991                 if ( !Profiler::instance()->isStub() ) {
 992                         # generalizeSQL will probably cut down the query to reasonable
 993                         # logging size most of the time. The substr is really just a sanity check.
 994                         if ( $isMaster ) {
 995                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 996                                 $totalProf = 'DatabaseBase::query-master';
 997                         } else {
 998                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 999                                 $totalProf = 'DatabaseBase::query';
1000                         }
1001                         wfProfileIn( $totalProf );
1002                         wfProfileIn( $queryProf );
1003                 }
1004
1005                 if ( $this->debug() ) {
1006                         static $cnt = 0;
1007
1008                         $cnt++;
1009                         $sqlx = substr( $commentedSql, 0, 500 );
1010                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
1011
1012                         $master = $isMaster ? 'master' : 'slave';
1013                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
1014                 }
1015
1016                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
1017
1018                 # Do the query and handle errors
1019                 $ret = $this->doQuery( $commentedSql );
1020
1021                 MWDebug::queryTime( $queryId );
1022
1023                 # Try reconnecting if the connection was lost
1024                 if ( false === $ret && $this->wasErrorReissuable() ) {
1025                         # Transaction is gone, like it or not
1026                         $this->mTrxLevel = 0;
1027                         $this->mTrxIdleCallbacks = array(); // cancel
1028                         $this->mTrxPreCommitCallbacks = array(); // cancel
1029                         wfDebug( "Connection lost, reconnecting...\n" );
1030
1031                         if ( $this->ping() ) {
1032                                 wfDebug( "Reconnected\n" );
1033                                 $sqlx = substr( $commentedSql, 0, 500 );
1034                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
1035                                 global $wgRequestTime;
1036                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
1037                                 if ( $elapsed < 300 ) {
1038                                         # Not a database error to lose a transaction after a minute or two
1039                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
1040                                 }
1041                                 $ret = $this->doQuery( $commentedSql );
1042                         } else {
1043                                 wfDebug( "Failed\n" );
1044                         }
1045                 }
1046
1047                 if ( false === $ret ) {
1048                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1049                 }
1050
1051                 if ( !Profiler::instance()->isStub() ) {
1052                         wfProfileOut( $queryProf );
1053                         wfProfileOut( $totalProf );
1054                 }
1055
1056                 return $this->resultObject( $ret );
1057         }
1058
1059         /**
1060          * Report a query error. Log the error, and if neither the object ignore
1061          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1062          *
1063          * @param $error String
1064          * @param $errno Integer
1065          * @param $sql String
1066          * @param $fname String
1067          * @param $tempIgnore Boolean
1068          * @throws DBQueryError
1069          */
1070         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1071                 # Ignore errors during error handling to avoid infinite recursion
1072                 $ignore = $this->ignoreErrors( true );
1073                 ++$this->mErrorCount;
1074
1075                 if ( $ignore || $tempIgnore ) {
1076                         wfDebug( "SQL ERROR (ignored): $error\n" );
1077                         $this->ignoreErrors( $ignore );
1078                 } else {
1079                         $sql1line = str_replace( "\n", "\\n", $sql );
1080                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
1081                         wfDebug( "SQL ERROR: " . $error . "\n" );
1082                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1083                 }
1084         }
1085
1086         /**
1087          * Intended to be compatible with the PEAR::DB wrapper functions.
1088          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1089          *
1090          * ? = scalar value, quoted as necessary
1091          * ! = raw SQL bit (a function for instance)
1092          * & = filename; reads the file and inserts as a blob
1093          *     (we don't use this though...)
1094          *
1095          * @param $sql string
1096          * @param $func string
1097          *
1098          * @return array
1099          */
1100         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1101                 /* MySQL doesn't support prepared statements (yet), so just
1102                    pack up the query for reference. We'll manually replace
1103                    the bits later. */
1104                 return array( 'query' => $sql, 'func' => $func );
1105         }
1106
1107         /**
1108          * Free a prepared query, generated by prepare().
1109          * @param $prepared
1110          */
1111         protected function freePrepared( $prepared ) {
1112                 /* No-op by default */
1113         }
1114
1115         /**
1116          * Execute a prepared query with the various arguments
1117          * @param string $prepared the prepared sql
1118          * @param $args Mixed: Either an array here, or put scalars as varargs
1119          *
1120          * @return ResultWrapper
1121          */
1122         public function execute( $prepared, $args = null ) {
1123                 if ( !is_array( $args ) ) {
1124                         # Pull the var args
1125                         $args = func_get_args();
1126                         array_shift( $args );
1127                 }
1128
1129                 $sql = $this->fillPrepared( $prepared['query'], $args );
1130
1131                 return $this->query( $sql, $prepared['func'] );
1132         }
1133
1134         /**
1135          * For faking prepared SQL statements on DBs that don't support it directly.
1136          *
1137          * @param string $preparedQuery a 'preparable' SQL statement
1138          * @param array $args of arguments to fill it with
1139          * @return string executable SQL
1140          */
1141         public function fillPrepared( $preparedQuery, $args ) {
1142                 reset( $args );
1143                 $this->preparedArgs =& $args;
1144
1145                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1146                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1147         }
1148
1149         /**
1150          * preg_callback func for fillPrepared()
1151          * The arguments should be in $this->preparedArgs and must not be touched
1152          * while we're doing this.
1153          *
1154          * @param $matches Array
1155          * @throws DBUnexpectedError
1156          * @return String
1157          */
1158         protected function fillPreparedArg( $matches ) {
1159                 switch ( $matches[1] ) {
1160                         case '\\?':
1161                                 return '?';
1162                         case '\\!':
1163                                 return '!';
1164                         case '\\&':
1165                                 return '&';
1166                 }
1167
1168                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1169
1170                 switch ( $matches[1] ) {
1171                         case '?':
1172                                 return $this->addQuotes( $arg );
1173                         case '!':
1174                                 return $arg;
1175                         case '&':
1176                                 # return $this->addQuotes( file_get_contents( $arg ) );
1177                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1178                         default:
1179                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1180                 }
1181         }
1182
1183         /**
1184          * Free a result object returned by query() or select(). It's usually not
1185          * necessary to call this, just use unset() or let the variable holding
1186          * the result object go out of scope.
1187          *
1188          * @param $res Mixed: A SQL result
1189          */
1190         public function freeResult( $res ) {
1191         }
1192
1193         /**
1194          * A SELECT wrapper which returns a single field from a single result row.
1195          *
1196          * Usually throws a DBQueryError on failure. If errors are explicitly
1197          * ignored, returns false on failure.
1198          *
1199          * If no result rows are returned from the query, false is returned.
1200          *
1201          * @param string|array $table Table name. See DatabaseBase::select() for details.
1202          * @param string $var The field name to select. This must be a valid SQL
1203          *   fragment: do not use unvalidated user input.
1204          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1205          * @param string $fname The function name of the caller.
1206          * @param string|array $options The query options. See DatabaseBase::select() for details.
1207          *
1208          * @return bool|mixed The value from the field, or false on failure.
1209          */
1210         public function selectField( $table, $var, $cond = '', $fname = __METHOD__,
1211                 $options = array()
1212         ) {
1213                 if ( !is_array( $options ) ) {
1214                         $options = array( $options );
1215                 }
1216
1217                 $options['LIMIT'] = 1;
1218
1219                 $res = $this->select( $table, $var, $cond, $fname, $options );
1220
1221                 if ( $res === false || !$this->numRows( $res ) ) {
1222                         return false;
1223                 }
1224
1225                 $row = $this->fetchRow( $res );
1226
1227                 if ( $row !== false ) {
1228                         return reset( $row );
1229                 } else {
1230                         return false;
1231                 }
1232         }
1233
1234         /**
1235          * Returns an optional USE INDEX clause to go after the table, and a
1236          * string to go at the end of the query.
1237          *
1238          * @param array $options associative array of options to be turned into
1239          *              an SQL query, valid keys are listed in the function.
1240          * @return Array
1241          * @see DatabaseBase::select()
1242          */
1243         public function makeSelectOptions( $options ) {
1244                 $preLimitTail = $postLimitTail = '';
1245                 $startOpts = '';
1246
1247                 $noKeyOptions = array();
1248
1249                 foreach ( $options as $key => $option ) {
1250                         if ( is_numeric( $key ) ) {
1251                                 $noKeyOptions[$option] = true;
1252                         }
1253                 }
1254
1255                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1256
1257                 $preLimitTail .= $this->makeOrderBy( $options );
1258
1259                 // if (isset($options['LIMIT'])) {
1260                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1261                 //              isset($options['OFFSET']) ? $options['OFFSET']
1262                 //              : false);
1263                 // }
1264
1265                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1266                         $postLimitTail .= ' FOR UPDATE';
1267                 }
1268
1269                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1270                         $postLimitTail .= ' LOCK IN SHARE MODE';
1271                 }
1272
1273                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1274                         $startOpts .= 'DISTINCT';
1275                 }
1276
1277                 # Various MySQL extensions
1278                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1279                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1280                 }
1281
1282                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1283                         $startOpts .= ' HIGH_PRIORITY';
1284                 }
1285
1286                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1287                         $startOpts .= ' SQL_BIG_RESULT';
1288                 }
1289
1290                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1291                         $startOpts .= ' SQL_BUFFER_RESULT';
1292                 }
1293
1294                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1295                         $startOpts .= ' SQL_SMALL_RESULT';
1296                 }
1297
1298                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1299                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1300                 }
1301
1302                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1303                         $startOpts .= ' SQL_CACHE';
1304                 }
1305
1306                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1307                         $startOpts .= ' SQL_NO_CACHE';
1308                 }
1309
1310                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1311                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1312                 } else {
1313                         $useIndex = '';
1314                 }
1315
1316                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1317         }
1318
1319         /**
1320          * Returns an optional GROUP BY with an optional HAVING
1321          *
1322          * @param array $options associative array of options
1323          * @return string
1324          * @see DatabaseBase::select()
1325          * @since 1.21
1326          */
1327         public function makeGroupByWithHaving( $options ) {
1328                 $sql = '';
1329                 if ( isset( $options['GROUP BY'] ) ) {
1330                         $gb = is_array( $options['GROUP BY'] )
1331                                 ? implode( ',', $options['GROUP BY'] )
1332                                 : $options['GROUP BY'];
1333                         $sql .= ' GROUP BY ' . $gb;
1334                 }
1335                 if ( isset( $options['HAVING'] ) ) {
1336                         $having = is_array( $options['HAVING'] )
1337                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1338                                 : $options['HAVING'];
1339                         $sql .= ' HAVING ' . $having;
1340                 }
1341                 return $sql;
1342         }
1343
1344         /**
1345          * Returns an optional ORDER BY
1346          *
1347          * @param array $options associative array of options
1348          * @return string
1349          * @see DatabaseBase::select()
1350          * @since 1.21
1351          */
1352         public function makeOrderBy( $options ) {
1353                 if ( isset( $options['ORDER BY'] ) ) {
1354                         $ob = is_array( $options['ORDER BY'] )
1355                                 ? implode( ',', $options['ORDER BY'] )
1356                                 : $options['ORDER BY'];
1357                         return ' ORDER BY ' . $ob;
1358                 }
1359                 return '';
1360         }
1361
1362         /**
1363          * Execute a SELECT query constructed using the various parameters provided.
1364          * See below for full details of the parameters.
1365          *
1366          * @param string|array $table Table name
1367          * @param string|array $vars Field names
1368          * @param string|array $conds Conditions
1369          * @param string $fname Caller function name
1370          * @param array $options Query options
1371          * @param $join_conds Array Join conditions
1372          *
1373          * @param $table string|array
1374          *
1375          * May be either an array of table names, or a single string holding a table
1376          * name. If an array is given, table aliases can be specified, for example:
1377          *
1378          *    array( 'a' => 'user' )
1379          *
1380          * This includes the user table in the query, with the alias "a" available
1381          * for use in field names (e.g. a.user_name).
1382          *
1383          * All of the table names given here are automatically run through
1384          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1385          * added, and various other table name mappings to be performed.
1386          *
1387          *
1388          * @param $vars string|array
1389          *
1390          * May be either a field name or an array of field names. The field names
1391          * can be complete fragments of SQL, for direct inclusion into the SELECT
1392          * query. If an array is given, field aliases can be specified, for example:
1393          *
1394          *   array( 'maxrev' => 'MAX(rev_id)' )
1395          *
1396          * This includes an expression with the alias "maxrev" in the query.
1397          *
1398          * If an expression is given, care must be taken to ensure that it is
1399          * DBMS-independent.
1400          *
1401          *
1402          * @param $conds string|array
1403          *
1404          * May be either a string containing a single condition, or an array of
1405          * conditions. If an array is given, the conditions constructed from each
1406          * element are combined with AND.
1407          *
1408          * Array elements may take one of two forms:
1409          *
1410          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1411          *   - Elements with a string key are interpreted as equality conditions,
1412          *     where the key is the field name.
1413          *     - If the value of such an array element is a scalar (such as a
1414          *       string), it will be treated as data and thus quoted appropriately.
1415          *       If it is null, an IS NULL clause will be added.
1416          *     - If the value is an array, an IN(...) clause will be constructed,
1417          *       such that the field name may match any of the elements in the
1418          *       array. The elements of the array will be quoted.
1419          *
1420          * Note that expressions are often DBMS-dependent in their syntax.
1421          * DBMS-independent wrappers are provided for constructing several types of
1422          * expression commonly used in condition queries. See:
1423          *    - DatabaseBase::buildLike()
1424          *    - DatabaseBase::conditional()
1425          *
1426          *
1427          * @param $options string|array
1428          *
1429          * Optional: Array of query options. Boolean options are specified by
1430          * including them in the array as a string value with a numeric key, for
1431          * example:
1432          *
1433          *    array( 'FOR UPDATE' )
1434          *
1435          * The supported options are:
1436          *
1437          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1438          *     with LIMIT can theoretically be used for paging through a result set,
1439          *     but this is discouraged in MediaWiki for performance reasons.
1440          *
1441          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1442          *     and then the first rows are taken until the limit is reached. LIMIT
1443          *     is applied to a result set after OFFSET.
1444          *
1445          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1446          *     changed until the next COMMIT.
1447          *
1448          *   - DISTINCT: Boolean: return only unique result rows.
1449          *
1450          *   - GROUP BY: May be either an SQL fragment string naming a field or
1451          *     expression to group by, or an array of such SQL fragments.
1452          *
1453          *   - HAVING: May be either an string containing a HAVING clause or an array of
1454          *     conditions building the HAVING clause. If an array is given, the conditions
1455          *     constructed from each element are combined with AND.
1456          *
1457          *   - ORDER BY: May be either an SQL fragment giving a field name or
1458          *     expression to order by, or an array of such SQL fragments.
1459          *
1460          *   - USE INDEX: This may be either a string giving the index name to use
1461          *     for the query, or an array. If it is an associative array, each key
1462          *     gives the table name (or alias), each value gives the index name to
1463          *     use for that table. All strings are SQL fragments and so should be
1464          *     validated by the caller.
1465          *
1466          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1467          *     instead of SELECT.
1468          *
1469          * And also the following boolean MySQL extensions, see the MySQL manual
1470          * for documentation:
1471          *
1472          *    - LOCK IN SHARE MODE
1473          *    - STRAIGHT_JOIN
1474          *    - HIGH_PRIORITY
1475          *    - SQL_BIG_RESULT
1476          *    - SQL_BUFFER_RESULT
1477          *    - SQL_SMALL_RESULT
1478          *    - SQL_CALC_FOUND_ROWS
1479          *    - SQL_CACHE
1480          *    - SQL_NO_CACHE
1481          *
1482          *
1483          * @param $join_conds string|array
1484          *
1485          * Optional associative array of table-specific join conditions. In the
1486          * most common case, this is unnecessary, since the join condition can be
1487          * in $conds. However, it is useful for doing a LEFT JOIN.
1488          *
1489          * The key of the array contains the table name or alias. The value is an
1490          * array with two elements, numbered 0 and 1. The first gives the type of
1491          * join, the second is an SQL fragment giving the join condition for that
1492          * table. For example:
1493          *
1494          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1495          *
1496          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1497          *   with no rows in it will be returned. If there was a query error, a
1498          *   DBQueryError exception will be thrown, except if the "ignore errors"
1499          *   option was set, in which case false will be returned.
1500          */
1501         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1502                 $options = array(), $join_conds = array() ) {
1503                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1504
1505                 return $this->query( $sql, $fname );
1506         }
1507
1508         /**
1509          * The equivalent of DatabaseBase::select() except that the constructed SQL
1510          * is returned, instead of being immediately executed. This can be useful for
1511          * doing UNION queries, where the SQL text of each query is needed. In general,
1512          * however, callers outside of Database classes should just use select().
1513          *
1514          * @param string|array $table Table name
1515          * @param string|array $vars Field names
1516          * @param string|array $conds Conditions
1517          * @param string $fname Caller function name
1518          * @param string|array $options Query options
1519          * @param $join_conds string|array Join conditions
1520          *
1521          * @return string SQL query string.
1522          * @see DatabaseBase::select()
1523          */
1524         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1525                 $options = array(), $join_conds = array() )
1526         {
1527                 if ( is_array( $vars ) ) {
1528                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1529                 }
1530
1531                 $options = (array)$options;
1532                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1533                         ? $options['USE INDEX']
1534                         : array();
1535
1536                 if ( is_array( $table ) ) {
1537                         $from = ' FROM ' .
1538                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1539                 } elseif ( $table != '' ) {
1540                         if ( $table[0] == ' ' ) {
1541                                 $from = ' FROM ' . $table;
1542                         } else {
1543                                 $from = ' FROM ' .
1544                                         $this->tableNamesWithUseIndexOrJOIN( array( $table ), $useIndexes, array() );
1545                         }
1546                 } else {
1547                         $from = '';
1548                 }
1549
1550                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1551                         $this->makeSelectOptions( $options );
1552
1553                 if ( !empty( $conds ) ) {
1554                         if ( is_array( $conds ) ) {
1555                                 $conds = $this->makeList( $conds, LIST_AND );
1556                         }
1557                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1558                 } else {
1559                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1560                 }
1561
1562                 if ( isset( $options['LIMIT'] ) ) {
1563                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1564                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1565                 }
1566                 $sql = "$sql $postLimitTail";
1567
1568                 if ( isset( $options['EXPLAIN'] ) ) {
1569                         $sql = 'EXPLAIN ' . $sql;
1570                 }
1571
1572                 return $sql;
1573         }
1574
1575         /**
1576          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1577          * that a single row object is returned. If the query returns no rows,
1578          * false is returned.
1579          *
1580          * @param string|array $table Table name
1581          * @param string|array $vars Field names
1582          * @param array $conds Conditions
1583          * @param string $fname Caller function name
1584          * @param string|array $options Query options
1585          * @param $join_conds array|string Join conditions
1586          *
1587          * @return object|bool
1588          */
1589         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1590                 $options = array(), $join_conds = array() )
1591         {
1592                 $options = (array)$options;
1593                 $options['LIMIT'] = 1;
1594                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1595
1596                 if ( $res === false ) {
1597                         return false;
1598                 }
1599
1600                 if ( !$this->numRows( $res ) ) {
1601                         return false;
1602                 }
1603
1604                 $obj = $this->fetchObject( $res );
1605
1606                 return $obj;
1607         }
1608
1609         /**
1610          * Estimate rows in dataset.
1611          *
1612          * MySQL allows you to estimate the number of rows that would be returned
1613          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1614          * index cardinality statistics, and is notoriously inaccurate, especially
1615          * when large numbers of rows have recently been added or deleted.
1616          *
1617          * For DBMSs that don't support fast result size estimation, this function
1618          * will actually perform the SELECT COUNT(*).
1619          *
1620          * Takes the same arguments as DatabaseBase::select().
1621          *
1622          * @param string $table table name
1623          * @param array|string $vars : unused
1624          * @param array|string $conds : filters on the table
1625          * @param string $fname function name for profiling
1626          * @param array $options options for select
1627          * @return Integer: row count
1628          */
1629         public function estimateRowCount( $table, $vars = '*', $conds = '',
1630                 $fname = __METHOD__, $options = array() )
1631         {
1632                 $rows = 0;
1633                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1634
1635                 if ( $res ) {
1636                         $row = $this->fetchRow( $res );
1637                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1638                 }
1639
1640                 return $rows;
1641         }
1642
1643         /**
1644          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1645          * It's only slightly flawed. Don't use for anything important.
1646          *
1647          * @param string $sql A SQL Query
1648          *
1649          * @return string
1650          */
1651         static function generalizeSQL( $sql ) {
1652                 # This does the same as the regexp below would do, but in such a way
1653                 # as to avoid crashing php on some large strings.
1654                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1655
1656                 $sql = str_replace( "\\\\", '', $sql );
1657                 $sql = str_replace( "\\'", '', $sql );
1658                 $sql = str_replace( "\\\"", '', $sql );
1659                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1660                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1661
1662                 # All newlines, tabs, etc replaced by single space
1663                 $sql = preg_replace( '/\s+/', ' ', $sql );
1664
1665                 # All numbers => N
1666                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1667                 $sql = preg_replace( '/-?\d+/s', 'N', $sql );
1668
1669                 return $sql;
1670         }
1671
1672         /**
1673          * Determines whether a field exists in a table
1674          *
1675          * @param string $table table name
1676          * @param string $field filed to check on that table
1677          * @param string $fname calling function name (optional)
1678          * @return Boolean: whether $table has filed $field
1679          */
1680         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1681                 $info = $this->fieldInfo( $table, $field );
1682
1683                 return (bool)$info;
1684         }
1685
1686         /**
1687          * Determines whether an index exists
1688          * Usually throws a DBQueryError on failure
1689          * If errors are explicitly ignored, returns NULL on failure
1690          *
1691          * @param $table
1692          * @param $index
1693          * @param $fname string
1694          *
1695          * @return bool|null
1696          */
1697         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1698                 if ( !$this->tableExists( $table ) ) {
1699                         return null;
1700                 }
1701
1702                 $info = $this->indexInfo( $table, $index, $fname );
1703                 if ( is_null( $info ) ) {
1704                         return null;
1705                 } else {
1706                         return $info !== false;
1707                 }
1708         }
1709
1710         /**
1711          * Query whether a given table exists
1712          *
1713          * @param $table string
1714          * @param $fname string
1715          *
1716          * @return bool
1717          */
1718         public function tableExists( $table, $fname = __METHOD__ ) {
1719                 $table = $this->tableName( $table );
1720                 $old = $this->ignoreErrors( true );
1721                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1722                 $this->ignoreErrors( $old );
1723
1724                 return (bool)$res;
1725         }
1726
1727         /**
1728          * mysql_field_type() wrapper
1729          * @param $res
1730          * @param $index
1731          * @return string
1732          */
1733         public function fieldType( $res, $index ) {
1734                 if ( $res instanceof ResultWrapper ) {
1735                         $res = $res->result;
1736                 }
1737
1738                 return mysql_field_type( $res, $index );
1739         }
1740
1741         /**
1742          * Determines if a given index is unique
1743          *
1744          * @param $table string
1745          * @param $index string
1746          *
1747          * @return bool
1748          */
1749         public function indexUnique( $table, $index ) {
1750                 $indexInfo = $this->indexInfo( $table, $index );
1751
1752                 if ( !$indexInfo ) {
1753                         return null;
1754                 }
1755
1756                 return !$indexInfo[0]->Non_unique;
1757         }
1758
1759         /**
1760          * Helper for DatabaseBase::insert().
1761          *
1762          * @param $options array
1763          * @return string
1764          */
1765         protected function makeInsertOptions( $options ) {
1766                 return implode( ' ', $options );
1767         }
1768
1769         /**
1770          * INSERT wrapper, inserts an array into a table.
1771          *
1772          * $a may be either:
1773          *
1774          *   - A single associative array. The array keys are the field names, and
1775          *     the values are the values to insert. The values are treated as data
1776          *     and will be quoted appropriately. If NULL is inserted, this will be
1777          *     converted to a database NULL.
1778          *   - An array with numeric keys, holding a list of associative arrays.
1779          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1780          *     each subarray must be identical to each other, and in the same order.
1781          *
1782          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1783          * returns success.
1784          *
1785          * $options is an array of options, with boolean options encoded as values
1786          * with numeric keys, in the same style as $options in
1787          * DatabaseBase::select(). Supported options are:
1788          *
1789          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1790          *     any rows which cause duplicate key errors are not inserted. It's
1791          *     possible to determine how many rows were successfully inserted using
1792          *     DatabaseBase::affectedRows().
1793          *
1794          * @param $table   String Table name. This will be passed through
1795          *                 DatabaseBase::tableName().
1796          * @param $a       Array of rows to insert
1797          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1798          * @param array $options of options
1799          *
1800          * @return bool
1801          */
1802         public function insert( $table, $a, $fname = __METHOD__, $options = array() ) {
1803                 # No rows to insert, easy just return now
1804                 if ( !count( $a ) ) {
1805                         return true;
1806                 }
1807
1808                 $table = $this->tableName( $table );
1809
1810                 if ( !is_array( $options ) ) {
1811                         $options = array( $options );
1812                 }
1813
1814                 $fh = null;
1815                 if ( isset( $options['fileHandle'] ) ) {
1816                         $fh = $options['fileHandle'];
1817                 }
1818                 $options = $this->makeInsertOptions( $options );
1819
1820                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1821                         $multi = true;
1822                         $keys = array_keys( $a[0] );
1823                 } else {
1824                         $multi = false;
1825                         $keys = array_keys( $a );
1826                 }
1827
1828                 $sql = 'INSERT ' . $options .
1829                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1830
1831                 if ( $multi ) {
1832                         $first = true;
1833                         foreach ( $a as $row ) {
1834                                 if ( $first ) {
1835                                         $first = false;
1836                                 } else {
1837                                         $sql .= ',';
1838                                 }
1839                                 $sql .= '(' . $this->makeList( $row ) . ')';
1840                         }
1841                 } else {
1842                         $sql .= '(' . $this->makeList( $a ) . ')';
1843                 }
1844
1845                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1846                         return false;
1847                 } elseif ( $fh !== null ) {
1848                         return true;
1849                 }
1850
1851                 return (bool)$this->query( $sql, $fname );
1852         }
1853
1854         /**
1855          * Make UPDATE options for the DatabaseBase::update function
1856          *
1857          * @param array $options The options passed to DatabaseBase::update
1858          * @return string
1859          */
1860         protected function makeUpdateOptions( $options ) {
1861                 if ( !is_array( $options ) ) {
1862                         $options = array( $options );
1863                 }
1864
1865                 $opts = array();
1866
1867                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1868                         $opts[] = $this->lowPriorityOption();
1869                 }
1870
1871                 if ( in_array( 'IGNORE', $options ) ) {
1872                         $opts[] = 'IGNORE';
1873                 }
1874
1875                 return implode( ' ', $opts );
1876         }
1877
1878         /**
1879          * UPDATE wrapper. Takes a condition array and a SET array.
1880          *
1881          * @param $table  String name of the table to UPDATE. This will be passed through
1882          *                DatabaseBase::tableName().
1883          *
1884          * @param array $values  An array of values to SET. For each array element,
1885          *                the key gives the field name, and the value gives the data
1886          *                to set that field to. The data will be quoted by
1887          *                DatabaseBase::addQuotes().
1888          *
1889          * @param $conds  Array:  An array of conditions (WHERE). See
1890          *                DatabaseBase::select() for the details of the format of
1891          *                condition arrays. Use '*' to update all rows.
1892          *
1893          * @param $fname  String: The function name of the caller (from __METHOD__),
1894          *                for logging and profiling.
1895          *
1896          * @param array $options An array of UPDATE options, can be:
1897          *                   - IGNORE: Ignore unique key conflicts
1898          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1899          * @return Boolean
1900          */
1901         function update( $table, $values, $conds, $fname = __METHOD__, $options = array() ) {
1902                 $table = $this->tableName( $table );
1903                 $opts = $this->makeUpdateOptions( $options );
1904                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1905
1906                 if ( $conds !== array() && $conds !== '*' ) {
1907                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1908                 }
1909
1910                 return $this->query( $sql, $fname );
1911         }
1912
1913         /**
1914          * Makes an encoded list of strings from an array
1915          * @param array $a containing the data
1916          * @param int $mode Constant
1917          *      - LIST_COMMA:          comma separated, no field names
1918          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1919          *        the documentation for $conds in DatabaseBase::select().
1920          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1921          *      - LIST_SET:            comma separated with field names, like a SET clause
1922          *      - LIST_NAMES:          comma separated field names
1923          *
1924          * @throws MWException|DBUnexpectedError
1925          * @return string
1926          */
1927         public function makeList( $a, $mode = LIST_COMMA ) {
1928                 if ( !is_array( $a ) ) {
1929                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1930                 }
1931
1932                 $first = true;
1933                 $list = '';
1934
1935                 foreach ( $a as $field => $value ) {
1936                         if ( !$first ) {
1937                                 if ( $mode == LIST_AND ) {
1938                                         $list .= ' AND ';
1939                                 } elseif ( $mode == LIST_OR ) {
1940                                         $list .= ' OR ';
1941                                 } else {
1942                                         $list .= ',';
1943                                 }
1944                         } else {
1945                                 $first = false;
1946                         }
1947
1948                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1949                                 $list .= "($value)";
1950                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1951                                 $list .= "$value";
1952                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1953                                 if ( count( $value ) == 0 ) {
1954                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1955                                 } elseif ( count( $value ) == 1 ) {
1956                                         // Special-case single values, as IN isn't terribly efficient
1957                                         // Don't necessarily assume the single key is 0; we don't
1958                                         // enforce linear numeric ordering on other arrays here.
1959                                         $value = array_values( $value );
1960                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1961                                 } else {
1962                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1963                                 }
1964                         } elseif ( $value === null ) {
1965                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1966                                         $list .= "$field IS ";
1967                                 } elseif ( $mode == LIST_SET ) {
1968                                         $list .= "$field = ";
1969                                 }
1970                                 $list .= 'NULL';
1971                         } else {
1972                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1973                                         $list .= "$field = ";
1974                                 }
1975                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1976                         }
1977                 }
1978
1979                 return $list;
1980         }
1981
1982         /**
1983          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1984          * The keys on each level may be either integers or strings.
1985          *
1986          * @param array $data organized as 2-d
1987          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
1988          * @param string $baseKey field name to match the base-level keys to (eg 'pl_namespace')
1989          * @param string $subKey field name to match the sub-level keys to (eg 'pl_title')
1990          * @return Mixed: string SQL fragment, or false if no items in array.
1991          */
1992         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1993                 $conds = array();
1994
1995                 foreach ( $data as $base => $sub ) {
1996                         if ( count( $sub ) ) {
1997                                 $conds[] = $this->makeList(
1998                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1999                                         LIST_AND );
2000                         }
2001                 }
2002
2003                 if ( $conds ) {
2004                         return $this->makeList( $conds, LIST_OR );
2005                 } else {
2006                         // Nothing to search for...
2007                         return false;
2008                 }
2009         }
2010
2011         /**
2012          * Return aggregated value alias
2013          *
2014          * @param $valuedata
2015          * @param $valuename string
2016          *
2017          * @return string
2018          */
2019         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2020                 return $valuename;
2021         }
2022
2023         /**
2024          * @param $field
2025          * @return string
2026          */
2027         public function bitNot( $field ) {
2028                 return "(~$field)";
2029         }
2030
2031         /**
2032          * @param $fieldLeft
2033          * @param $fieldRight
2034          * @return string
2035          */
2036         public function bitAnd( $fieldLeft, $fieldRight ) {
2037                 return "($fieldLeft & $fieldRight)";
2038         }
2039
2040         /**
2041          * @param  $fieldLeft
2042          * @param  $fieldRight
2043          * @return string
2044          */
2045         public function bitOr( $fieldLeft, $fieldRight ) {
2046                 return "($fieldLeft | $fieldRight)";
2047         }
2048
2049         /**
2050          * Build a concatenation list to feed into a SQL query
2051          * @param array $stringList list of raw SQL expressions; caller is responsible for any quoting
2052          * @return String
2053          */
2054         public function buildConcat( $stringList ) {
2055                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2056         }
2057
2058         /**
2059          * Change the current database
2060          *
2061          * @todo Explain what exactly will fail if this is not overridden.
2062          *
2063          * @param $db
2064          *
2065          * @return bool Success or failure
2066          */
2067         public function selectDB( $db ) {
2068                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
2069                 # if your database engine supports a concept similar to MySQL's
2070                 # databases you may as well.
2071                 $this->mDBname = $db;
2072                 return true;
2073         }
2074
2075         /**
2076          * Get the current DB name
2077          */
2078         public function getDBname() {
2079                 return $this->mDBname;
2080         }
2081
2082         /**
2083          * Get the server hostname or IP address
2084          */
2085         public function getServer() {
2086                 return $this->mServer;
2087         }
2088
2089         /**
2090          * Format a table name ready for use in constructing an SQL query
2091          *
2092          * This does two important things: it quotes the table names to clean them up,
2093          * and it adds a table prefix if only given a table name with no quotes.
2094          *
2095          * All functions of this object which require a table name call this function
2096          * themselves. Pass the canonical name to such functions. This is only needed
2097          * when calling query() directly.
2098          *
2099          * @param string $name database table name
2100          * @param string $format One of:
2101          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2102          *            so that it can be used in a query.
2103          *   raw - Do not add identifier quotes to the table name
2104          * @return String: full database name
2105          */
2106         public function tableName( $name, $format = 'quoted' ) {
2107                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
2108                 # Skip the entire process when we have a string quoted on both ends.
2109                 # Note that we check the end so that we will still quote any use of
2110                 # use of `database`.table. But won't break things if someone wants
2111                 # to query a database table with a dot in the name.
2112                 if ( $this->isQuotedIdentifier( $name ) ) {
2113                         return $name;
2114                 }
2115
2116                 # Lets test for any bits of text that should never show up in a table
2117                 # name. Basically anything like JOIN or ON which are actually part of
2118                 # SQL queries, but may end up inside of the table value to combine
2119                 # sql. Such as how the API is doing.
2120                 # Note that we use a whitespace test rather than a \b test to avoid
2121                 # any remote case where a word like on may be inside of a table name
2122                 # surrounded by symbols which may be considered word breaks.
2123                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2124                         return $name;
2125                 }
2126
2127                 # Split database and table into proper variables.
2128                 # We reverse the explode so that database.table and table both output
2129                 # the correct table.
2130                 $dbDetails = explode( '.', $name, 2 );
2131                 if ( count( $dbDetails ) == 2 ) {
2132                         list( $database, $table ) = $dbDetails;
2133                         # We don't want any prefix added in this case
2134                         $prefix = '';
2135                 } else {
2136                         list( $table ) = $dbDetails;
2137                         if ( $wgSharedDB !== null # We have a shared database
2138                                 && $this->mForeign == false # We're not working on a foreign database
2139                                 && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
2140                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2141                         ) {
2142                                 $database = $wgSharedDB;
2143                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2144                         } else {
2145                                 $database = null;
2146                                 $prefix = $this->mTablePrefix; # Default prefix
2147                         }
2148                 }
2149
2150                 # Quote $table and apply the prefix if not quoted.
2151                 $tableName = "{$prefix}{$table}";
2152                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) ) {
2153                         $tableName = $this->addIdentifierQuotes( $tableName );
2154                 }
2155
2156                 # Quote $database and merge it with the table name if needed
2157                 if ( $database !== null ) {
2158                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2159                                 $database = $this->addIdentifierQuotes( $database );
2160                         }
2161                         $tableName = $database . '.' . $tableName;
2162                 }
2163
2164                 return $tableName;
2165         }
2166
2167         /**
2168          * Fetch a number of table names into an array
2169          * This is handy when you need to construct SQL for joins
2170          *
2171          * Example:
2172          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2173          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2174          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2175          *
2176          * @return array
2177          */
2178         public function tableNames() {
2179                 $inArray = func_get_args();
2180                 $retVal = array();
2181
2182                 foreach ( $inArray as $name ) {
2183                         $retVal[$name] = $this->tableName( $name );
2184                 }
2185
2186                 return $retVal;
2187         }
2188
2189         /**
2190          * Fetch a number of table names into an zero-indexed numerical array
2191          * This is handy when you need to construct SQL for joins
2192          *
2193          * Example:
2194          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2195          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2196          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2197          *
2198          * @return array
2199          */
2200         public function tableNamesN() {
2201                 $inArray = func_get_args();
2202                 $retVal = array();
2203
2204                 foreach ( $inArray as $name ) {
2205                         $retVal[] = $this->tableName( $name );
2206                 }
2207
2208                 return $retVal;
2209         }
2210
2211         /**
2212          * Get an aliased table name
2213          * e.g. tableName AS newTableName
2214          *
2215          * @param string $name Table name, see tableName()
2216          * @param string|bool $alias Alias (optional)
2217          * @return string SQL name for aliased table. Will not alias a table to its own name
2218          */
2219         public function tableNameWithAlias( $name, $alias = false ) {
2220                 if ( !$alias || $alias == $name ) {
2221                         return $this->tableName( $name );
2222                 } else {
2223                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2224                 }
2225         }
2226
2227         /**
2228          * Gets an array of aliased table names
2229          *
2230          * @param $tables array( [alias] => table )
2231          * @return array of strings, see tableNameWithAlias()
2232          */
2233         public function tableNamesWithAlias( $tables ) {
2234                 $retval = array();
2235                 foreach ( $tables as $alias => $table ) {
2236                         if ( is_numeric( $alias ) ) {
2237                                 $alias = $table;
2238                         }
2239                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2240                 }
2241                 return $retval;
2242         }
2243
2244         /**
2245          * Get an aliased field name
2246          * e.g. fieldName AS newFieldName
2247          *
2248          * @param string $name Field name
2249          * @param string|bool $alias Alias (optional)
2250          * @return string SQL name for aliased field. Will not alias a field to its own name
2251          */
2252         public function fieldNameWithAlias( $name, $alias = false ) {
2253                 if ( !$alias || (string)$alias === (string)$name ) {
2254                         return $name;
2255                 } else {
2256                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2257                 }
2258         }
2259
2260         /**
2261          * Gets an array of aliased field names
2262          *
2263          * @param $fields array( [alias] => field )
2264          * @return array of strings, see fieldNameWithAlias()
2265          */
2266         public function fieldNamesWithAlias( $fields ) {
2267                 $retval = array();
2268                 foreach ( $fields as $alias => $field ) {
2269                         if ( is_numeric( $alias ) ) {
2270                                 $alias = $field;
2271                         }
2272                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2273                 }
2274                 return $retval;
2275         }
2276
2277         /**
2278          * Get the aliased table name clause for a FROM clause
2279          * which might have a JOIN and/or USE INDEX clause
2280          *
2281          * @param array $tables ( [alias] => table )
2282          * @param $use_index array Same as for select()
2283          * @param $join_conds array Same as for select()
2284          * @return string
2285          */
2286         protected function tableNamesWithUseIndexOrJOIN(
2287                 $tables, $use_index = array(), $join_conds = array()
2288         ) {
2289                 $ret = array();
2290                 $retJOIN = array();
2291                 $use_index = (array)$use_index;
2292                 $join_conds = (array)$join_conds;
2293
2294                 foreach ( $tables as $alias => $table ) {
2295                         if ( !is_string( $alias ) ) {
2296                                 // No alias? Set it equal to the table name
2297                                 $alias = $table;
2298                         }
2299                         // Is there a JOIN clause for this table?
2300                         if ( isset( $join_conds[$alias] ) ) {
2301                                 list( $joinType, $conds ) = $join_conds[$alias];
2302                                 $tableClause = $joinType;
2303                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2304                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2305                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2306                                         if ( $use != '' ) {
2307                                                 $tableClause .= ' ' . $use;
2308                                         }
2309                                 }
2310                                 $on = $this->makeList( (array)$conds, LIST_AND );
2311                                 if ( $on != '' ) {
2312                                         $tableClause .= ' ON (' . $on . ')';
2313                                 }
2314
2315                                 $retJOIN[] = $tableClause;
2316                         // Is there an INDEX clause for this table?
2317                         } elseif ( isset( $use_index[$alias] ) ) {
2318                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2319                                 $tableClause .= ' ' . $this->useIndexClause(
2320                                         implode( ',', (array)$use_index[$alias] ) );
2321
2322                                 $ret[] = $tableClause;
2323                         } else {
2324                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2325
2326                                 $ret[] = $tableClause;
2327                         }
2328                 }
2329
2330                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2331                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2332                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2333
2334                 // Compile our final table clause
2335                 return implode( ' ', array( $implicitJoins, $explicitJoins ) );
2336         }
2337
2338         /**
2339          * Get the name of an index in a given table
2340          *
2341          * @param $index
2342          *
2343          * @return string
2344          */
2345         protected function indexName( $index ) {
2346                 // Backwards-compatibility hack
2347                 $renamed = array(
2348                         'ar_usertext_timestamp' => 'usertext_timestamp',
2349                         'un_user_id' => 'user_id',
2350                         'un_user_ip' => 'user_ip',
2351                 );
2352
2353                 if ( isset( $renamed[$index] ) ) {
2354                         return $renamed[$index];
2355                 } else {
2356                         return $index;
2357                 }
2358         }
2359
2360         /**
2361          * Adds quotes and backslashes.
2362          *
2363          * @param $s string
2364          *
2365          * @return string
2366          */
2367         public function addQuotes( $s ) {
2368                 if ( $s === null ) {
2369                         return 'NULL';
2370                 } else {
2371                         # This will also quote numeric values. This should be harmless,
2372                         # and protects against weird problems that occur when they really
2373                         # _are_ strings such as article titles and string->number->string
2374                         # conversion is not 1:1.
2375                         return "'" . $this->strencode( $s ) . "'";
2376                 }
2377         }
2378
2379         /**
2380          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2381          * MySQL uses `backticks` while basically everything else uses double quotes.
2382          * Since MySQL is the odd one out here the double quotes are our generic
2383          * and we implement backticks in DatabaseMysql.
2384          *
2385          * @param $s string
2386          *
2387          * @return string
2388          */
2389         public function addIdentifierQuotes( $s ) {
2390                 return '"' . str_replace( '"', '""', $s ) . '"';
2391         }
2392
2393         /**
2394          * Returns if the given identifier looks quoted or not according to
2395          * the database convention for quoting identifiers .
2396          *
2397          * @param $name string
2398          *
2399          * @return boolean
2400          */
2401         public function isQuotedIdentifier( $name ) {
2402                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2403         }
2404
2405         /**
2406          * @param $s string
2407          * @return string
2408          */
2409         protected function escapeLikeInternal( $s ) {
2410                 $s = str_replace( '\\', '\\\\', $s );
2411                 $s = $this->strencode( $s );
2412                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2413
2414                 return $s;
2415         }
2416
2417         /**
2418          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2419          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2420          * Alternatively, the function could be provided with an array of aforementioned parameters.
2421          *
2422          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2423          * for subpages of 'My page title'.
2424          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2425          *
2426          * @since 1.16
2427          * @return String: fully built LIKE statement
2428          */
2429         public function buildLike() {
2430                 $params = func_get_args();
2431
2432                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2433                         $params = $params[0];
2434                 }
2435
2436                 $s = '';
2437
2438                 foreach ( $params as $value ) {
2439                         if ( $value instanceof LikeMatch ) {
2440                                 $s .= $value->toString();
2441                         } else {
2442                                 $s .= $this->escapeLikeInternal( $value );
2443                         }
2444                 }
2445
2446                 return " LIKE '" . $s . "' ";
2447         }
2448
2449         /**
2450          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2451          *
2452          * @return LikeMatch
2453          */
2454         public function anyChar() {
2455                 return new LikeMatch( '_' );
2456         }
2457
2458         /**
2459          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2460          *
2461          * @return LikeMatch
2462          */
2463         public function anyString() {
2464                 return new LikeMatch( '%' );
2465         }
2466
2467         /**
2468          * Returns an appropriately quoted sequence value for inserting a new row.
2469          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2470          * subclass will return an integer, and save the value for insertId()
2471          *
2472          * Any implementation of this function should *not* involve reusing
2473          * sequence numbers created for rolled-back transactions.
2474          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2475          * @param $seqName string
2476          * @return null
2477          */
2478         public function nextSequenceValue( $seqName ) {
2479                 return null;
2480         }
2481
2482         /**
2483          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2484          * is only needed because a) MySQL must be as efficient as possible due to
2485          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2486          * which index to pick.  Anyway, other databases might have different
2487          * indexes on a given table.  So don't bother overriding this unless you're
2488          * MySQL.
2489          * @param $index
2490          * @return string
2491          */
2492         public function useIndexClause( $index ) {
2493                 return '';
2494         }
2495
2496         /**
2497          * REPLACE query wrapper.
2498          *
2499          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2500          * except that when there is a duplicate key error, the old row is deleted
2501          * and the new row is inserted in its place.
2502          *
2503          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2504          * perform the delete, we need to know what the unique indexes are so that
2505          * we know how to find the conflicting rows.
2506          *
2507          * It may be more efficient to leave off unique indexes which are unlikely
2508          * to collide. However if you do this, you run the risk of encountering
2509          * errors which wouldn't have occurred in MySQL.
2510          *
2511          * @param string $table The table to replace the row(s) in.
2512          * @param array $rows Can be either a single row to insert, or multiple rows,
2513          *    in the same format as for DatabaseBase::insert()
2514          * @param array $uniqueIndexes is an array of indexes. Each element may be either
2515          *    a field name or an array of field names
2516          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2517          */
2518         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2519                 $quotedTable = $this->tableName( $table );
2520
2521                 if ( count( $rows ) == 0 ) {
2522                         return;
2523                 }
2524
2525                 # Single row case
2526                 if ( !is_array( reset( $rows ) ) ) {
2527                         $rows = array( $rows );
2528                 }
2529
2530                 foreach ( $rows as $row ) {
2531                         # Delete rows which collide
2532                         if ( $uniqueIndexes ) {
2533                                 $sql = "DELETE FROM $quotedTable WHERE ";
2534                                 $first = true;
2535                                 foreach ( $uniqueIndexes as $index ) {
2536                                         if ( $first ) {
2537                                                 $first = false;
2538                                                 $sql .= '( ';
2539                                         } else {
2540                                                 $sql .= ' ) OR ( ';
2541                                         }
2542                                         if ( is_array( $index ) ) {
2543                                                 $first2 = true;
2544                                                 foreach ( $index as $col ) {
2545                                                         if ( $first2 ) {
2546                                                                 $first2 = false;
2547                                                         } else {
2548                                                                 $sql .= ' AND ';
2549                                                         }
2550                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2551                                                 }
2552                                         } else {
2553                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2554                                         }
2555                                 }
2556                                 $sql .= ' )';
2557                                 $this->query( $sql, $fname );
2558                         }
2559
2560                         # Now insert the row
2561                         $this->insert( $table, $row, $fname );
2562                 }
2563         }
2564
2565         /**
2566          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2567          * statement.
2568          *
2569          * @param string $table Table name
2570          * @param array $rows Rows to insert
2571          * @param string $fname Caller function name
2572          *
2573          * @return ResultWrapper
2574          */
2575         protected function nativeReplace( $table, $rows, $fname ) {
2576                 $table = $this->tableName( $table );
2577
2578                 # Single row case
2579                 if ( !is_array( reset( $rows ) ) ) {
2580                         $rows = array( $rows );
2581                 }
2582
2583                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2584                 $first = true;
2585
2586                 foreach ( $rows as $row ) {
2587                         if ( $first ) {
2588                                 $first = false;
2589                         } else {
2590                                 $sql .= ',';
2591                         }
2592
2593                         $sql .= '(' . $this->makeList( $row ) . ')';
2594                 }
2595
2596                 return $this->query( $sql, $fname );
2597         }
2598
2599         /**
2600          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
2601          *
2602          * This updates any conflicting rows (according to the unique indexes) using
2603          * the provided SET clause and inserts any remaining (non-conflicted) rows.
2604          *
2605          * $rows may be either:
2606          *   - A single associative array. The array keys are the field names, and
2607          *     the values are the values to insert. The values are treated as data
2608          *     and will be quoted appropriately. If NULL is inserted, this will be
2609          *     converted to a database NULL.
2610          *   - An array with numeric keys, holding a list of associative arrays.
2611          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
2612          *     each subarray must be identical to each other, and in the same order.
2613          *
2614          * It may be more efficient to leave off unique indexes which are unlikely
2615          * to collide. However if you do this, you run the risk of encountering
2616          * errors which wouldn't have occurred in MySQL.
2617          *
2618          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
2619          * returns success.
2620          *
2621          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
2622          * @param array $rows A single row or list of rows to insert
2623          * @param array $uniqueIndexes List of single field names or field name tuples
2624          * @param array $set An array of values to SET. For each array element,
2625          *                the key gives the field name, and the value gives the data
2626          *                to set that field to. The data will be quoted by
2627          *                DatabaseBase::addQuotes().
2628          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2629          * @param array $options of options
2630          *
2631          * @return bool
2632          * @since 1.22
2633          */
2634         public function upsert(
2635                 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
2636         ) {
2637                 if ( !count( $rows ) ) {
2638                         return true; // nothing to do
2639                 }
2640                 $rows = is_array( reset( $rows ) ) ? $rows : array( $rows );
2641
2642                 if ( count( $uniqueIndexes ) ) {
2643                         $clauses = array(); // list WHERE clauses that each identify a single row
2644                         foreach ( $rows as $row ) {
2645                                 foreach ( $uniqueIndexes as $index ) {
2646                                         $index = is_array( $index ) ? $index : array( $index ); // columns
2647                                         $rowKey = array(); // unique key to this row
2648                                         foreach ( $index as $column ) {
2649                                                 $rowKey[$column] = $row[$column];
2650                                         }
2651                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2652                                 }
2653                         }
2654                         $where = array( $this->makeList( $clauses, LIST_OR ) );
2655                 } else {
2656                         $where = false;
2657                 }
2658
2659                 $useTrx = !$this->mTrxLevel;
2660                 if ( $useTrx ) {
2661                         $this->begin( $fname );
2662                 }
2663                 try {
2664                         # Update any existing conflicting row(s)
2665                         if ( $where !== false ) {
2666                                 $ok = $this->update( $table, $set, $where, $fname );
2667                         } else {
2668                                 $ok = true;
2669                         }
2670                         # Now insert any non-conflicting row(s)
2671                         $ok = $this->insert( $table, $rows, $fname, array( 'IGNORE' ) ) && $ok;
2672                 } catch ( Exception $e ) {
2673                         if ( $useTrx ) {
2674                                 $this->rollback( $fname );
2675                         }
2676                         throw $e;
2677                 }
2678                 if ( $useTrx ) {
2679                         $this->commit( $fname );
2680                 }
2681
2682                 return $ok;
2683         }
2684
2685         /**
2686          * DELETE where the condition is a join.
2687          *
2688          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2689          * we use sub-selects
2690          *
2691          * For safety, an empty $conds will not delete everything. If you want to
2692          * delete all rows where the join condition matches, set $conds='*'.
2693          *
2694          * DO NOT put the join condition in $conds.
2695          *
2696          * @param $delTable   String: The table to delete from.
2697          * @param $joinTable  String: The other table.
2698          * @param $delVar     String: The variable to join on, in the first table.
2699          * @param $joinVar    String: The variable to join on, in the second table.
2700          * @param $conds      Array: Condition array of field names mapped to variables,
2701          *                    ANDed together in the WHERE clause
2702          * @param $fname      String: Calling function name (use __METHOD__) for
2703          *                    logs/profiling
2704          * @throws DBUnexpectedError
2705          */
2706         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2707                 $fname = __METHOD__ )
2708         {
2709                 if ( !$conds ) {
2710                         throw new DBUnexpectedError( $this,
2711                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2712                 }
2713
2714                 $delTable = $this->tableName( $delTable );
2715                 $joinTable = $this->tableName( $joinTable );
2716                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2717                 if ( $conds != '*' ) {
2718                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2719                 }
2720                 $sql .= ')';
2721
2722                 $this->query( $sql, $fname );
2723         }
2724
2725         /**
2726          * Returns the size of a text field, or -1 for "unlimited"
2727          *
2728          * @param $table string
2729          * @param $field string
2730          *
2731          * @return int
2732          */
2733         public function textFieldSize( $table, $field ) {
2734                 $table = $this->tableName( $table );
2735                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2736                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2737                 $row = $this->fetchObject( $res );
2738
2739                 $m = array();
2740
2741                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2742                         $size = $m[1];
2743                 } else {
2744                         $size = -1;
2745                 }
2746
2747                 return $size;
2748         }
2749
2750         /**
2751          * A string to insert into queries to show that they're low-priority, like
2752          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2753          * string and nothing bad should happen.
2754          *
2755          * @return string Returns the text of the low priority option if it is
2756          *   supported, or a blank string otherwise
2757          */
2758         public function lowPriorityOption() {
2759                 return '';
2760         }
2761
2762         /**
2763          * DELETE query wrapper.
2764          *
2765          * @param array $table Table name
2766          * @param string|array $conds of conditions. See $conds in DatabaseBase::select() for
2767          *               the format. Use $conds == "*" to delete all rows
2768          * @param string $fname name of the calling function
2769          *
2770          * @throws DBUnexpectedError
2771          * @return bool|ResultWrapper
2772          */
2773         public function delete( $table, $conds, $fname = __METHOD__ ) {
2774                 if ( !$conds ) {
2775                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2776                 }
2777
2778                 $table = $this->tableName( $table );
2779                 $sql = "DELETE FROM $table";
2780
2781                 if ( $conds != '*' ) {
2782                         if ( is_array( $conds ) ) {
2783                                 $conds = $this->makeList( $conds, LIST_AND );
2784                         }
2785                         $sql .= ' WHERE ' . $conds;
2786                 }
2787
2788                 return $this->query( $sql, $fname );
2789         }
2790
2791         /**
2792          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2793          * into another table.
2794          *
2795          * @param string $destTable The table name to insert into
2796          * @param string|array $srcTable May be either a table name, or an array of table names
2797          *    to include in a join.
2798          *
2799          * @param array $varMap must be an associative array of the form
2800          *    array( 'dest1' => 'source1', ...). Source items may be literals
2801          *    rather than field names, but strings should be quoted with
2802          *    DatabaseBase::addQuotes()
2803          *
2804          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2805          *    the details of the format of condition arrays. May be "*" to copy the
2806          *    whole table.
2807          *
2808          * @param string $fname The function name of the caller, from __METHOD__
2809          *
2810          * @param array $insertOptions Options for the INSERT part of the query, see
2811          *    DatabaseBase::insert() for details.
2812          * @param array $selectOptions Options for the SELECT part of the query, see
2813          *    DatabaseBase::select() for details.
2814          *
2815          * @return ResultWrapper
2816          */
2817         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2818                 $fname = __METHOD__,
2819                 $insertOptions = array(), $selectOptions = array() )
2820         {
2821                 $destTable = $this->tableName( $destTable );
2822
2823                 if ( is_array( $insertOptions ) ) {
2824                         $insertOptions = implode( ' ', $insertOptions );
2825                 }
2826
2827                 if ( !is_array( $selectOptions ) ) {
2828                         $selectOptions = array( $selectOptions );
2829                 }
2830
2831                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2832
2833                 if ( is_array( $srcTable ) ) {
2834                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2835                 } else {
2836                         $srcTable = $this->tableName( $srcTable );
2837                 }
2838
2839                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2840                         " SELECT $startOpts " . implode( ',', $varMap ) .
2841                         " FROM $srcTable $useIndex ";
2842
2843                 if ( $conds != '*' ) {
2844                         if ( is_array( $conds ) ) {
2845                                 $conds = $this->makeList( $conds, LIST_AND );
2846                         }
2847                         $sql .= " WHERE $conds";
2848                 }
2849
2850                 $sql .= " $tailOpts";
2851
2852                 return $this->query( $sql, $fname );
2853         }
2854
2855         /**
2856          * Construct a LIMIT query with optional offset.  This is used for query
2857          * pages.  The SQL should be adjusted so that only the first $limit rows
2858          * are returned.  If $offset is provided as well, then the first $offset
2859          * rows should be discarded, and the next $limit rows should be returned.
2860          * If the result of the query is not ordered, then the rows to be returned
2861          * are theoretically arbitrary.
2862          *
2863          * $sql is expected to be a SELECT, if that makes a difference.
2864          *
2865          * The version provided by default works in MySQL and SQLite.  It will very
2866          * likely need to be overridden for most other DBMSes.
2867          *
2868          * @param string $sql SQL query we will append the limit too
2869          * @param $limit Integer the SQL limit
2870          * @param $offset Integer|bool the SQL offset (default false)
2871          *
2872          * @throws DBUnexpectedError
2873          * @return string
2874          */
2875         public function limitResult( $sql, $limit, $offset = false ) {
2876                 if ( !is_numeric( $limit ) ) {
2877                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2878                 }
2879                 return "$sql LIMIT "
2880                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2881                         . "{$limit} ";
2882         }
2883
2884         /**
2885          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2886          * within the UNION construct.
2887          * @return Boolean
2888          */
2889         public function unionSupportsOrderAndLimit() {
2890                 return true; // True for almost every DB supported
2891         }
2892
2893         /**
2894          * Construct a UNION query
2895          * This is used for providing overload point for other DB abstractions
2896          * not compatible with the MySQL syntax.
2897          * @param array $sqls SQL statements to combine
2898          * @param $all Boolean: use UNION ALL
2899          * @return String: SQL fragment
2900          */
2901         public function unionQueries( $sqls, $all ) {
2902                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2903                 return '(' . implode( $glue, $sqls ) . ')';
2904         }
2905
2906         /**
2907          * Returns an SQL expression for a simple conditional.  This doesn't need
2908          * to be overridden unless CASE isn't supported in your DBMS.
2909          *
2910          * @param string|array $cond SQL expression which will result in a boolean value
2911          * @param string $trueVal SQL expression to return if true
2912          * @param string $falseVal SQL expression to return if false
2913          * @return String: SQL fragment
2914          */
2915         public function conditional( $cond, $trueVal, $falseVal ) {
2916                 if ( is_array( $cond ) ) {
2917                         $cond = $this->makeList( $cond, LIST_AND );
2918                 }
2919                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2920         }
2921
2922         /**
2923          * Returns a comand for str_replace function in SQL query.
2924          * Uses REPLACE() in MySQL
2925          *
2926          * @param string $orig column to modify
2927          * @param string $old column to seek
2928          * @param string $new column to replace with
2929          *
2930          * @return string
2931          */
2932         public function strreplace( $orig, $old, $new ) {
2933                 return "REPLACE({$orig}, {$old}, {$new})";
2934         }
2935
2936         /**
2937          * Determines how long the server has been up
2938          * STUB
2939          *
2940          * @return int
2941          */
2942         public function getServerUptime() {
2943                 return 0;
2944         }
2945
2946         /**
2947          * Determines if the last failure was due to a deadlock
2948          * STUB
2949          *
2950          * @return bool
2951          */
2952         public function wasDeadlock() {
2953                 return false;
2954         }
2955
2956         /**
2957          * Determines if the last failure was due to a lock timeout
2958          * STUB
2959          *
2960          * @return bool
2961          */
2962         public function wasLockTimeout() {
2963                 return false;
2964         }
2965
2966         /**
2967          * Determines if the last query error was something that should be dealt
2968          * with by pinging the connection and reissuing the query.
2969          * STUB
2970          *
2971          * @return bool
2972          */
2973         public function wasErrorReissuable() {
2974                 return false;
2975         }
2976
2977         /**
2978          * Determines if the last failure was due to the database being read-only.
2979          * STUB
2980          *
2981          * @return bool
2982          */
2983         public function wasReadOnlyError() {
2984                 return false;
2985         }
2986
2987         /**
2988          * Perform a deadlock-prone transaction.
2989          *
2990          * This function invokes a callback function to perform a set of write
2991          * queries. If a deadlock occurs during the processing, the transaction
2992          * will be rolled back and the callback function will be called again.
2993          *
2994          * Usage:
2995          *   $dbw->deadlockLoop( callback, ... );
2996          *
2997          * Extra arguments are passed through to the specified callback function.
2998          *
2999          * Returns whatever the callback function returned on its successful,
3000          * iteration, or false on error, for example if the retry limit was
3001          * reached.
3002          *
3003          * @return bool
3004          */
3005         public function deadlockLoop() {
3006                 $this->begin( __METHOD__ );
3007                 $args = func_get_args();
3008                 $function = array_shift( $args );
3009                 $oldIgnore = $this->ignoreErrors( true );
3010                 $tries = self::DEADLOCK_TRIES;
3011
3012                 if ( is_array( $function ) ) {
3013                         $fname = $function[0];
3014                 } else {
3015                         $fname = $function;
3016                 }
3017
3018                 do {
3019                         $retVal = call_user_func_array( $function, $args );
3020                         $error = $this->lastError();
3021                         $errno = $this->lastErrno();
3022                         $sql = $this->lastQuery();
3023
3024                         if ( $errno ) {
3025                                 if ( $this->wasDeadlock() ) {
3026                                         # Retry
3027                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3028                                 } else {
3029                                         $this->reportQueryError( $error, $errno, $sql, $fname );
3030                                 }
3031                         }
3032                 } while ( $this->wasDeadlock() && --$tries > 0 );
3033
3034                 $this->ignoreErrors( $oldIgnore );
3035
3036                 if ( $tries <= 0 ) {
3037                         $this->rollback( __METHOD__ );
3038                         $this->reportQueryError( $error, $errno, $sql, $fname );
3039                         return false;
3040                 } else {
3041                         $this->commit( __METHOD__ );
3042                         return $retVal;
3043                 }
3044         }
3045
3046         /**
3047          * Wait for the slave to catch up to a given master position.
3048          *
3049          * @param $pos DBMasterPos object
3050          * @param $timeout Integer: the maximum number of seconds to wait for
3051          *   synchronisation
3052          *
3053          * @return integer: zero if the slave was past that position already,
3054          *   greater than zero if we waited for some period of time, less than
3055          *   zero if we timed out.
3056          */
3057         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3058                 wfProfileIn( __METHOD__ );
3059
3060                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3061                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
3062
3063                         if ( $wait > $timeout * 1e6 ) {
3064                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
3065                                 wfProfileOut( __METHOD__ );
3066                                 return -1;
3067                         } elseif ( $wait > 0 ) {
3068                                 wfDebug( "Fake slave waiting $wait us\n" );
3069                                 usleep( $wait );
3070                                 wfProfileOut( __METHOD__ );
3071                                 return 1;
3072                         } else {
3073                                 wfDebug( "Fake slave up to date ($wait us)\n" );
3074                                 wfProfileOut( __METHOD__ );
3075                                 return 0;
3076                         }
3077                 }
3078
3079                 wfProfileOut( __METHOD__ );
3080
3081                 # Real waits are implemented in the subclass.
3082                 return 0;
3083         }
3084
3085         /**
3086          * Get the replication position of this slave
3087          *
3088          * @return DBMasterPos, or false if this is not a slave.
3089          */
3090         public function getSlavePos() {
3091                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3092                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
3093                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
3094                         return $pos;
3095                 } else {
3096                         # Stub
3097                         return false;
3098                 }
3099         }
3100
3101         /**
3102          * Get the position of this master
3103          *
3104          * @return DBMasterPos, or false if this is not a master
3105          */
3106         public function getMasterPos() {
3107                 if ( $this->mFakeMaster ) {
3108                         return new MySQLMasterPos( 'fake', microtime( true ) );
3109                 } else {
3110                         return false;
3111                 }
3112         }
3113
3114         /**
3115          * Run an anonymous function as soon as there is no transaction pending.
3116          * If there is a transaction and it is rolled back, then the callback is cancelled.
3117          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
3118          * Callbacks must commit any transactions that they begin.
3119          *
3120          * This is useful for updates to different systems or when separate transactions are needed.
3121          * For example, one might want to enqueue jobs into a system outside the database, but only
3122          * after the database is updated so that the jobs will see the data when they actually run.
3123          * It can also be used for updates that easily cause deadlocks if locks are held too long.
3124          *
3125          * @param callable $callback
3126          * @since 1.20
3127          */
3128         final public function onTransactionIdle( $callback ) {
3129                 $this->mTrxIdleCallbacks[] = array( $callback, wfGetCaller() );
3130                 if ( !$this->mTrxLevel ) {
3131                         $this->runOnTransactionIdleCallbacks();
3132                 }
3133         }
3134
3135         /**
3136          * Run an anonymous function before the current transaction commits or now if there is none.
3137          * If there is a transaction and it is rolled back, then the callback is cancelled.
3138          * Callbacks must not start nor commit any transactions.
3139          *
3140          * This is useful for updates that easily cause deadlocks if locks are held too long
3141          * but where atomicity is strongly desired for these updates and some related updates.
3142          *
3143          * @param callable $callback
3144          * @since 1.22
3145          */
3146         final public function onTransactionPreCommitOrIdle( $callback ) {
3147                 if ( $this->mTrxLevel ) {
3148                         $this->mTrxPreCommitCallbacks[] = array( $callback, wfGetCaller() );
3149                 } else {
3150                         $this->onTransactionIdle( $callback ); // this will trigger immediately
3151                 }
3152         }
3153
3154         /**
3155          * Actually any "on transaction idle" callbacks.
3156          *
3157          * @since 1.20
3158          */
3159         protected function runOnTransactionIdleCallbacks() {
3160                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
3161
3162                 $e = null; // last exception
3163                 do { // callbacks may add callbacks :)
3164                         $callbacks = $this->mTrxIdleCallbacks;
3165                         $this->mTrxIdleCallbacks = array(); // recursion guard
3166                         foreach ( $callbacks as $callback ) {
3167                                 try {
3168                                         list( $phpCallback ) = $callback;
3169                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
3170                                         call_user_func( $phpCallback );
3171                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3172                                 } catch ( Exception $e ) {}
3173                         }
3174                 } while ( count( $this->mTrxIdleCallbacks ) );
3175
3176                 if ( $e instanceof Exception ) {
3177                         throw $e; // re-throw any last exception
3178                 }
3179         }
3180
3181         /**
3182          * Actually any "on transaction pre-commit" callbacks.
3183          *
3184          * @since 1.22
3185          */
3186         protected function runOnTransactionPreCommitCallbacks() {
3187                 $e = null; // last exception
3188                 do { // callbacks may add callbacks :)
3189                         $callbacks = $this->mTrxPreCommitCallbacks;
3190                         $this->mTrxPreCommitCallbacks = array(); // recursion guard
3191                         foreach ( $callbacks as $callback ) {
3192                                 try {
3193                                         list( $phpCallback ) = $callback;
3194                                         call_user_func( $phpCallback );
3195                                 } catch ( Exception $e ) {}
3196                         }
3197                 } while ( count( $this->mTrxPreCommitCallbacks ) );
3198
3199                 if ( $e instanceof Exception ) {
3200                         throw $e; // re-throw any last exception
3201                 }
3202         }
3203
3204         /**
3205          * Begin an atomic section of statements
3206          *
3207          * If a transaction has been started already, just keep track of the given
3208          * section name to make sure the transaction is not committed pre-maturely.
3209          * This function can be used in layers (with sub-sections), so use a stack
3210          * to keep track of the different atomic sections. If there is no transaction,
3211          * start one implicitly.
3212          *
3213          * The goal of this function is to create an atomic section of SQL queries
3214          * without having to start a new transaction if it already exists.
3215          *
3216          * Atomic sections are more strict than transactions. With transactions,
3217          * attempting to begin a new transaction when one is already running results
3218          * in MediaWiki issuing a brief warning and doing an implicit commit. All
3219          * atomic levels *must* be explicitly closed using DatabaseBase::endAtomic(),
3220          * and any database transactions cannot be began or committed until all atomic
3221          * levels are closed. There is no such thing as implicitly opening or closing
3222          * an atomic section.
3223          *
3224          * @since 1.23
3225          * @param string $fname
3226          */
3227         final public function startAtomic( $fname = __METHOD__ ) {
3228                 if ( !$this->mTrxLevel ) {
3229                         $this->begin( $fname );
3230                         $this->mTrxAutomatic = true;
3231                         $this->mTrxAutomaticAtomic = true;
3232                 }
3233
3234                 $this->mTrxAtomicLevels->push( $fname );
3235         }
3236
3237         /**
3238          * Begin a transaction. If a transaction is already in progress, that transaction will be committed before the
3239          * new transaction is started.
3240          *
3241          * Note that when the DBO_TRX flag is set (which is usually the case for web requests, but not for maintenance scripts),
3242          * any previous database query will have started a transaction automatically.
3243          *
3244          * Nesting of transactions is not supported. Attempts to nest transactions will cause a warning, unless the current
3245          * transaction was started automatically because of the DBO_TRX flag.
3246          *
3247          * @param $fname string
3248          */
3249         final public function begin( $fname = __METHOD__ ) {
3250                 global $wgDebugDBTransactions;
3251
3252                 if ( $this->mTrxLevel ) { // implicit commit
3253                         if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3254                                 // If the current transaction was an automatic atomic one, then we definitely have
3255                                 // a problem. Same if there is any unclosed atomic level.
3256                                 throw new DBUnexpectedError( $this,
3257                                         "Attempted to start explicit transaction when atomic levels are still open."
3258                                 );
3259                         } elseif ( !$this->mTrxAutomatic ) {
3260                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3261                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3262                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3263                                         " performing implicit commit!";
3264                                 wfWarn( $msg );
3265                                 wfLogDBError( $msg );
3266                         } else {
3267                                 // if the transaction was automatic and has done write operations,
3268                                 // log it if $wgDebugDBTransactions is enabled.
3269                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3270                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3271                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3272                                         );
3273                                 }
3274                         }
3275
3276                         $this->runOnTransactionPreCommitCallbacks();
3277                         $this->doCommit( $fname );
3278                         if ( $this->mTrxDoneWrites ) {
3279                                 Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3280                         }
3281                         $this->runOnTransactionIdleCallbacks();
3282                 }
3283
3284                 $this->doBegin( $fname );
3285                 $this->mTrxFname = $fname;
3286                 $this->mTrxDoneWrites = false;
3287                 $this->mTrxAutomatic = false;
3288                 $this->mTrxAutomaticAtomic = false;
3289                 $this->mTrxAtomicLevels = new SplStack;
3290         }
3291
3292         /**
3293          * Issues the BEGIN command to the database server.
3294          *
3295          * @see DatabaseBase::begin()
3296          * @param type $fname
3297          */
3298         protected function doBegin( $fname ) {
3299                 $this->query( 'BEGIN', $fname );
3300                 $this->mTrxLevel = 1;
3301         }
3302
3303         /**
3304          * Ends an atomic section of SQL statements
3305          *
3306          * Ends the next section of atomic SQL statements and commits the transaction
3307          * if necessary.
3308          *
3309          * @since 1.23
3310          * @see DatabaseBase::startAtomic
3311          * @param string $fname
3312          */
3313         final public function endAtomic( $fname = __METHOD__ ) {
3314                 if ( $this->mTrxAtomicLevels->isEmpty() ||
3315                         $this->mTrxAtomicLevels->pop() !== $fname
3316                 ) {
3317                         throw new DBUnexpectedError( $this, 'Invalid atomic section ended.' );
3318                 }
3319
3320                 if ( $this->mTrxAtomicLevels->isEmpty() && $this->mTrxAutomaticAtomic ) {
3321                         $this->commit( $fname, 'flush' );
3322                 }
3323         }
3324
3325         /**
3326          * Commits a transaction previously started using begin().
3327          * If no transaction is in progress, a warning is issued.
3328          *
3329          * Nesting of transactions is not supported.
3330          *
3331          * @param $fname string
3332          * @param string $flush Flush flag, set to 'flush' to disable warnings about explicitly committing implicit
3333          *        transactions, or calling commit when no transaction is in progress.
3334          *        This will silently break any ongoing explicit transaction. Only set the flush flag if you are sure
3335          *        that it is safe to ignore these warnings in your context.
3336          */
3337         final public function commit( $fname = __METHOD__, $flush = '' ) {
3338                 if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3339                         // There are still atomic sections open. This cannot be ignored
3340                         throw new DBUnexpectedError( $this, "Attempted to commit transaction while atomic sections are still open" );
3341                 }
3342
3343                 if ( $flush != 'flush' ) {
3344                         if ( !$this->mTrxLevel ) {
3345                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3346                         } elseif ( $this->mTrxAutomatic ) {
3347                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3348                         }
3349                 } else {
3350                         if ( !$this->mTrxLevel ) {
3351                                 return; // nothing to do
3352                         } elseif ( !$this->mTrxAutomatic ) {
3353                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3354                         }
3355                 }
3356
3357                 $this->runOnTransactionPreCommitCallbacks();
3358                 $this->doCommit( $fname );
3359                 if ( $this->mTrxDoneWrites ) {
3360                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3361                 }
3362                 $this->mTrxDoneWrites = false;
3363                 $this->runOnTransactionIdleCallbacks();
3364         }
3365
3366         /**
3367          * Issues the COMMIT command to the database server.
3368          *
3369          * @see DatabaseBase::commit()
3370          * @param type $fname
3371          */
3372         protected function doCommit( $fname ) {
3373                 if ( $this->mTrxLevel ) {
3374                         $this->query( 'COMMIT', $fname );
3375                         $this->mTrxLevel = 0;
3376                 }
3377         }
3378
3379         /**
3380          * Rollback a transaction previously started using begin().
3381          * If no transaction is in progress, a warning is issued.
3382          *
3383          * No-op on non-transactional databases.
3384          *
3385          * @param $fname string
3386          */
3387         final public function rollback( $fname = __METHOD__ ) {
3388                 if ( !$this->mTrxLevel ) {
3389                         wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3390                 }
3391                 $this->doRollback( $fname );
3392                 $this->mTrxIdleCallbacks = array(); // cancel
3393                 $this->mTrxPreCommitCallbacks = array(); // cancel
3394                 $this->mTrxAtomicLevels = new SplStack;
3395                 if ( $this->mTrxDoneWrites ) {
3396                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3397                 }
3398                 $this->mTrxDoneWrites = false;
3399         }
3400
3401         /**
3402          * Issues the ROLLBACK command to the database server.
3403          *
3404          * @see DatabaseBase::rollback()
3405          * @param type $fname
3406          */
3407         protected function doRollback( $fname ) {
3408                 if ( $this->mTrxLevel ) {
3409                         $this->query( 'ROLLBACK', $fname, true );
3410                         $this->mTrxLevel = 0;
3411                 }
3412         }
3413
3414         /**
3415          * Creates a new table with structure copied from existing table
3416          * Note that unlike most database abstraction functions, this function does not
3417          * automatically append database prefix, because it works at a lower
3418          * abstraction level.
3419          * The table names passed to this function shall not be quoted (this
3420          * function calls addIdentifierQuotes when needed).
3421          *
3422          * @param string $oldName name of table whose structure should be copied
3423          * @param string $newName name of table to be created
3424          * @param $temporary Boolean: whether the new table should be temporary
3425          * @param string $fname calling function name
3426          * @throws MWException
3427          * @return Boolean: true if operation was successful
3428          */
3429         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3430                 $fname = __METHOD__
3431         ) {
3432                 throw new MWException(
3433                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3434         }
3435
3436         /**
3437          * List all tables on the database
3438          *
3439          * @param string $prefix Only show tables with this prefix, e.g. mw_
3440          * @param string $fname calling function name
3441          * @throws MWException
3442          */
3443         function listTables( $prefix = null, $fname = __METHOD__ ) {
3444                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3445         }
3446
3447         /**
3448          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3449          * to the format used for inserting into timestamp fields in this DBMS.
3450          *
3451          * The result is unquoted, and needs to be passed through addQuotes()
3452          * before it can be included in raw SQL.
3453          *
3454          * @param $ts string|int
3455          *
3456          * @return string
3457          */
3458         public function timestamp( $ts = 0 ) {
3459                 return wfTimestamp( TS_MW, $ts );
3460         }
3461
3462         /**
3463          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3464          * to the format used for inserting into timestamp fields in this DBMS. If
3465          * NULL is input, it is passed through, allowing NULL values to be inserted
3466          * into timestamp fields.
3467          *
3468          * The result is unquoted, and needs to be passed through addQuotes()
3469          * before it can be included in raw SQL.
3470          *
3471          * @param $ts string|int
3472          *
3473          * @return string
3474          */
3475         public function timestampOrNull( $ts = null ) {
3476                 if ( is_null( $ts ) ) {
3477                         return null;
3478                 } else {
3479                         return $this->timestamp( $ts );
3480                 }
3481         }
3482
3483         /**
3484          * Take the result from a query, and wrap it in a ResultWrapper if
3485          * necessary. Boolean values are passed through as is, to indicate success
3486          * of write queries or failure.
3487          *
3488          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3489          * resource, and it was necessary to call this function to convert it to
3490          * a wrapper. Nowadays, raw database objects are never exposed to external
3491          * callers, so this is unnecessary in external code. For compatibility with
3492          * old code, ResultWrapper objects are passed through unaltered.
3493          *
3494          * @param $result bool|ResultWrapper
3495          *
3496          * @return bool|ResultWrapper
3497          */
3498         public function resultObject( $result ) {
3499                 if ( empty( $result ) ) {
3500                         return false;
3501                 } elseif ( $result instanceof ResultWrapper ) {
3502                         return $result;
3503                 } elseif ( $result === true ) {
3504                         // Successful write query
3505                         return $result;
3506                 } else {
3507                         return new ResultWrapper( $this, $result );
3508                 }
3509         }
3510
3511         /**
3512          * Ping the server and try to reconnect if it there is no connection
3513          *
3514          * @return bool Success or failure
3515          */
3516         public function ping() {
3517                 # Stub.  Not essential to override.
3518                 return true;
3519         }
3520
3521         /**
3522          * Get slave lag. Currently supported only by MySQL.
3523          *
3524          * Note that this function will generate a fatal error on many
3525          * installations. Most callers should use LoadBalancer::safeGetLag()
3526          * instead.
3527          *
3528          * @return int Database replication lag in seconds
3529          */
3530         public function getLag() {
3531                 return intval( $this->mFakeSlaveLag );
3532         }
3533
3534         /**
3535          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3536          *
3537          * @return int
3538          */
3539         function maxListLen() {
3540                 return 0;
3541         }
3542
3543         /**
3544          * Some DBMSs have a special format for inserting into blob fields, they
3545          * don't allow simple quoted strings to be inserted. To insert into such
3546          * a field, pass the data through this function before passing it to
3547          * DatabaseBase::insert().
3548          * @param $b string
3549          * @return string
3550          */
3551         public function encodeBlob( $b ) {
3552                 return $b;
3553         }
3554
3555         /**
3556          * Some DBMSs return a special placeholder object representing blob fields
3557          * in result objects. Pass the object through this function to return the
3558          * original string.
3559          * @param $b string
3560          * @return string
3561          */
3562         public function decodeBlob( $b ) {
3563                 return $b;
3564         }
3565
3566         /**
3567          * Override database's default behavior. $options include:
3568          *     'connTimeout' : Set the connection timeout value in seconds.
3569          *                     May be useful for very long batch queries such as
3570          *                     full-wiki dumps, where a single query reads out over
3571          *                     hours or days.
3572          *
3573          * @param $options Array
3574          * @return void
3575          */
3576         public function setSessionOptions( array $options ) {
3577         }
3578
3579         /**
3580          * Read and execute SQL commands from a file.
3581          *
3582          * Returns true on success, error string or exception on failure (depending
3583          * on object's error ignore settings).
3584          *
3585          * @param string $filename File name to open
3586          * @param bool|callable $lineCallback Optional function called before reading each line
3587          * @param bool|callable $resultCallback Optional function called for each MySQL result
3588          * @param bool|string $fname Calling function name or false if name should be
3589          *      generated dynamically using $filename
3590          * @param bool|callable $inputCallback Callback: Optional function called for each complete line sent
3591          * @throws MWException
3592          * @throws Exception|MWException
3593          * @return bool|string
3594          */
3595         public function sourceFile(
3596                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3597         ) {
3598                 wfSuppressWarnings();
3599                 $fp = fopen( $filename, 'r' );
3600                 wfRestoreWarnings();
3601
3602                 if ( false === $fp ) {
3603                         throw new MWException( "Could not open \"{$filename}\".\n" );
3604                 }
3605
3606                 if ( !$fname ) {
3607                         $fname = __METHOD__ . "( $filename )";
3608                 }
3609
3610                 try {
3611                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3612                 }
3613                 catch ( MWException $e ) {
3614                         fclose( $fp );
3615                         throw $e;
3616                 }
3617
3618                 fclose( $fp );
3619
3620                 return $error;
3621         }
3622
3623         /**
3624          * Get the full path of a patch file. Originally based on archive()
3625          * from updaters.inc. Keep in mind this always returns a patch, as
3626          * it fails back to MySQL if no DB-specific patch can be found
3627          *
3628          * @param string $patch The name of the patch, like patch-something.sql
3629          * @return String Full path to patch file
3630          */
3631         public function patchPath( $patch ) {
3632                 global $IP;
3633
3634                 $dbType = $this->getType();
3635                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3636                         return "$IP/maintenance/$dbType/archives/$patch";
3637                 } else {
3638                         return "$IP/maintenance/archives/$patch";
3639                 }
3640         }
3641
3642         /**
3643          * Set variables to be used in sourceFile/sourceStream, in preference to the
3644          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3645          * all. If it's set to false, $GLOBALS will be used.
3646          *
3647          * @param bool|array $vars mapping variable name to value.
3648          */
3649         public function setSchemaVars( $vars ) {
3650                 $this->mSchemaVars = $vars;
3651         }
3652
3653         /**
3654          * Read and execute commands from an open file handle.
3655          *
3656          * Returns true on success, error string or exception on failure (depending
3657          * on object's error ignore settings).
3658          *
3659          * @param $fp Resource: File handle
3660          * @param $lineCallback Callback: Optional function called before reading each query
3661          * @param $resultCallback Callback: Optional function called for each MySQL result
3662          * @param string $fname Calling function name
3663          * @param $inputCallback Callback: Optional function called for each complete query sent
3664          * @return bool|string
3665          */
3666         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3667                 $fname = __METHOD__, $inputCallback = false )
3668         {
3669                 $cmd = '';
3670
3671                 while ( !feof( $fp ) ) {
3672                         if ( $lineCallback ) {
3673                                 call_user_func( $lineCallback );
3674                         }
3675
3676                         $line = trim( fgets( $fp ) );
3677
3678                         if ( $line == '' ) {
3679                                 continue;
3680                         }
3681
3682                         if ( '-' == $line[0] && '-' == $line[1] ) {
3683                                 continue;
3684                         }
3685
3686                         if ( $cmd != '' ) {
3687                                 $cmd .= ' ';
3688                         }
3689
3690                         $done = $this->streamStatementEnd( $cmd, $line );
3691
3692                         $cmd .= "$line\n";
3693
3694                         if ( $done || feof( $fp ) ) {
3695                                 $cmd = $this->replaceVars( $cmd );
3696
3697                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3698                                         $res = $this->query( $cmd, $fname );
3699
3700                                         if ( $resultCallback ) {
3701                                                 call_user_func( $resultCallback, $res, $this );
3702                                         }
3703
3704                                         if ( false === $res ) {
3705                                                 $err = $this->lastError();
3706                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3707                                         }
3708                                 }
3709                                 $cmd = '';
3710                         }
3711                 }
3712
3713                 return true;
3714         }
3715
3716         /**
3717          * Called by sourceStream() to check if we've reached a statement end
3718          *
3719          * @param string $sql SQL assembled so far
3720          * @param string $newLine New line about to be added to $sql
3721          * @return Bool Whether $newLine contains end of the statement
3722          */
3723         public function streamStatementEnd( &$sql, &$newLine ) {
3724                 if ( $this->delimiter ) {
3725                         $prev = $newLine;
3726                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3727                         if ( $newLine != $prev ) {
3728                                 return true;
3729                         }
3730                 }
3731                 return false;
3732         }
3733
3734         /**
3735          * Database independent variable replacement. Replaces a set of variables
3736          * in an SQL statement with their contents as given by $this->getSchemaVars().
3737          *
3738          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3739          *
3740          * - '{$var}' should be used for text and is passed through the database's
3741          *   addQuotes method.
3742          * - `{$var}` should be used for identifiers (eg: table and database names),
3743          *   it is passed through the database's addIdentifierQuotes method which
3744          *   can be overridden if the database uses something other than backticks.
3745          * - / *$var* / is just encoded, besides traditional table prefix and
3746          *   table options its use should be avoided.
3747          *
3748          * @param string $ins SQL statement to replace variables in
3749          * @return String The new SQL statement with variables replaced
3750          */
3751         protected function replaceSchemaVars( $ins ) {
3752                 $vars = $this->getSchemaVars();
3753                 foreach ( $vars as $var => $value ) {
3754                         // replace '{$var}'
3755                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3756                         // replace `{$var}`
3757                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3758                         // replace /*$var*/
3759                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3760                 }
3761                 return $ins;
3762         }
3763
3764         /**
3765          * Replace variables in sourced SQL
3766          *
3767          * @param $ins string
3768          *
3769          * @return string
3770          */
3771         protected function replaceVars( $ins ) {
3772                 $ins = $this->replaceSchemaVars( $ins );
3773
3774                 // Table prefixes
3775                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3776                         array( $this, 'tableNameCallback' ), $ins );
3777
3778                 // Index names
3779                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3780                         array( $this, 'indexNameCallback' ), $ins );
3781
3782                 return $ins;
3783         }
3784
3785         /**
3786          * Get schema variables. If none have been set via setSchemaVars(), then
3787          * use some defaults from the current object.
3788          *
3789          * @return array
3790          */
3791         protected function getSchemaVars() {
3792                 if ( $this->mSchemaVars ) {
3793                         return $this->mSchemaVars;
3794                 } else {
3795                         return $this->getDefaultSchemaVars();
3796                 }
3797         }
3798
3799         /**
3800          * Get schema variables to use if none have been set via setSchemaVars().
3801          *
3802          * Override this in derived classes to provide variables for tables.sql
3803          * and SQL patch files.
3804          *
3805          * @return array
3806          */
3807         protected function getDefaultSchemaVars() {
3808                 return array();
3809         }
3810
3811         /**
3812          * Table name callback
3813          *
3814          * @param $matches array
3815          *
3816          * @return string
3817          */
3818         protected function tableNameCallback( $matches ) {
3819                 return $this->tableName( $matches[1] );
3820         }
3821
3822         /**
3823          * Index name callback
3824          *
3825          * @param $matches array
3826          *
3827          * @return string
3828          */
3829         protected function indexNameCallback( $matches ) {
3830                 return $this->indexName( $matches[1] );
3831         }
3832
3833         /**
3834          * Check to see if a named lock is available. This is non-blocking.
3835          *
3836          * @param string $lockName name of lock to poll
3837          * @param string $method name of method calling us
3838          * @return Boolean
3839          * @since 1.20
3840          */
3841         public function lockIsFree( $lockName, $method ) {
3842                 return true;
3843         }
3844
3845         /**
3846          * Acquire a named lock
3847          *
3848          * Abstracted from Filestore::lock() so child classes can implement for
3849          * their own needs.
3850          *
3851          * @param string $lockName name of lock to aquire
3852          * @param string $method name of method calling us
3853          * @param $timeout Integer: timeout
3854          * @return Boolean
3855          */
3856         public function lock( $lockName, $method, $timeout = 5 ) {
3857                 return true;
3858         }
3859
3860         /**
3861          * Release a lock.
3862          *
3863          * @param string $lockName Name of lock to release
3864          * @param string $method Name of method calling us
3865          *
3866          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3867          * by this thread (in which case the lock is not released), and NULL if the named
3868          * lock did not exist
3869          */
3870         public function unlock( $lockName, $method ) {
3871                 return true;
3872         }
3873
3874         /**
3875          * Lock specific tables
3876          *
3877          * @param array $read of tables to lock for read access
3878          * @param array $write of tables to lock for write access
3879          * @param string $method name of caller
3880          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
3881          *
3882          * @return bool
3883          */
3884         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3885                 return true;
3886         }
3887
3888         /**
3889          * Unlock specific tables
3890          *
3891          * @param string $method the caller
3892          *
3893          * @return bool
3894          */
3895         public function unlockTables( $method ) {
3896                 return true;
3897         }
3898
3899         /**
3900          * Delete a table
3901          * @param $tableName string
3902          * @param $fName string
3903          * @return bool|ResultWrapper
3904          * @since 1.18
3905          */
3906         public function dropTable( $tableName, $fName = __METHOD__ ) {
3907                 if ( !$this->tableExists( $tableName, $fName ) ) {
3908                         return false;
3909                 }
3910                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3911                 if ( $this->cascadingDeletes() ) {
3912                         $sql .= " CASCADE";
3913                 }
3914                 return $this->query( $sql, $fName );
3915         }
3916
3917         /**
3918          * Get search engine class. All subclasses of this need to implement this
3919          * if they wish to use searching.
3920          *
3921          * @return String
3922          */
3923         public function getSearchEngine() {
3924                 return 'SearchEngineDummy';
3925         }
3926
3927         /**
3928          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3929          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3930          * because "i" sorts after all numbers.
3931          *
3932          * @return String
3933          */
3934         public function getInfinity() {
3935                 return 'infinity';
3936         }
3937
3938         /**
3939          * Encode an expiry time into the DBMS dependent format
3940          *
3941          * @param string $expiry timestamp for expiry, or the 'infinity' string
3942          * @return String
3943          */
3944         public function encodeExpiry( $expiry ) {
3945                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3946                         ? $this->getInfinity()
3947                         : $this->timestamp( $expiry );
3948         }
3949
3950         /**
3951          * Decode an expiry time into a DBMS independent format
3952          *
3953          * @param string $expiry DB timestamp field value for expiry
3954          * @param $format integer: TS_* constant, defaults to TS_MW
3955          * @return String
3956          */
3957         public function decodeExpiry( $expiry, $format = TS_MW ) {
3958                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3959                         ? 'infinity'
3960                         : wfTimestamp( $format, $expiry );
3961         }
3962
3963         /**
3964          * Allow or deny "big selects" for this session only. This is done by setting
3965          * the sql_big_selects session variable.
3966          *
3967          * This is a MySQL-specific feature.
3968          *
3969          * @param $value Mixed: true for allow, false for deny, or "default" to
3970          *   restore the initial value
3971          */
3972         public function setBigSelects( $value = true ) {
3973                 // no-op
3974         }
3975
3976         /**
3977          * @since 1.19
3978          */
3979         public function __toString() {
3980                 return (string)$this->mConn;
3981         }
3982
3983         /**
3984          * Run a few simple sanity checks
3985          */
3986         public function __destruct() {
3987                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
3988                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
3989                 }
3990                 if ( count( $this->mTrxIdleCallbacks ) || count( $this->mTrxPreCommitCallbacks ) ) {
3991                         $callers = array();
3992                         foreach ( $this->mTrxIdleCallbacks as $callbackInfo ) {
3993                                 $callers[] = $callbackInfo[1];
3994
3995                         }
3996                         $callers = implode( ', ', $callers );
3997                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
3998                 }
3999         }
4000 }