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          * @since 1.22
 306          * @var Process cache of VIEWs names in the database
 307          */
 308         protected $allViews = null;
 309
 310 # ------------------------------------------------------------------------------
 311 # Accessors
 312 # ------------------------------------------------------------------------------
 313         # These optionally set a variable and return the previous state
 314
 315         /**
 316          * A string describing the current software version, and possibly
 317          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 318          * Use getServerVersion() to get machine-friendly information.
 319          *
 320          * @return string: Version information from the database server
 321          */
 322         public function getServerInfo() {
 323                 return $this->getServerVersion();
 324         }
 325
 326         /**
 327          * @return string: command delimiter used by this database engine
 328          */
 329         public function getDelimiter() {
 330                 return $this->delimiter;
 331         }
 332
 333         /**
 334          * Boolean, controls output of large amounts of debug information.
 335          * @param $debug bool|null
 336          *   - true to enable debugging
 337          *   - false to disable debugging
 338          *   - omitted or null to do nothing
 339          *
 340          * @return bool|null previous value of the flag
 341          */
 342         public function debug( $debug = null ) {
 343                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 344         }
 345
 346         /**
 347          * Turns buffering of SQL result sets on (true) or off (false). Default is
 348          * "on".
 349          *
 350          * Unbuffered queries are very troublesome in MySQL:
 351          *
 352          *   - If another query is executed while the first query is being read
 353          *     out, the first query is killed. This means you can't call normal
 354          *     MediaWiki functions while you are reading an unbuffered query result
 355          *     from a normal wfGetDB() connection.
 356          *
 357          *   - Unbuffered queries cause the MySQL server to use large amounts of
 358          *     memory and to hold broad locks which block other queries.
 359          *
 360          * If you want to limit client-side memory, it's almost always better to
 361          * split up queries into batches using a LIMIT clause than to switch off
 362          * buffering.
 363          *
 364          * @param $buffer null|bool
 365          *
 366          * @return null|bool The previous value of the flag
 367          */
 368         public function bufferResults( $buffer = null ) {
 369                 if ( is_null( $buffer ) ) {
 370                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 371                 } else {
 372                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 373                 }
 374         }
 375
 376         /**
 377          * Turns on (false) or off (true) the automatic generation and sending
 378          * of a "we're sorry, but there has been a database error" page on
 379          * database errors. Default is on (false). When turned off, the
 380          * code should use lastErrno() and lastError() to handle the
 381          * situation as appropriate.
 382          *
 383          * Do not use this function outside of the Database classes.
 384          *
 385          * @param $ignoreErrors bool|null
 386          *
 387          * @return bool The previous value of the flag.
 388          */
 389         public function ignoreErrors( $ignoreErrors = null ) {
 390                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 391         }
 392
 393         /**
 394          * Gets or sets the current transaction level.
 395          *
 396          * Historically, transactions were allowed to be "nested". This is no
 397          * longer supported, so this function really only returns a boolean.
 398          *
 399          * @param int $level An integer (0 or 1), or omitted to leave it unchanged.
 400          * @return int The previous value
 401          */
 402         public function trxLevel( $level = null ) {
 403                 return wfSetVar( $this->mTrxLevel, $level );
 404         }
 405
 406         /**
 407          * Get/set the number of errors logged. Only useful when errors are ignored
 408          * @param int $count The count to set, or omitted to leave it unchanged.
 409          * @return int The error count
 410          */
 411         public function errorCount( $count = null ) {
 412                 return wfSetVar( $this->mErrorCount, $count );
 413         }
 414
 415         /**
 416          * Get/set the table prefix.
 417          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 418          * @return string The previous table prefix.
 419          */
 420         public function tablePrefix( $prefix = null ) {
 421                 return wfSetVar( $this->mTablePrefix, $prefix );
 422         }
 423
 424         /**
 425          * Set the filehandle to copy write statements to.
 426          *
 427          * @param $fh filehandle
 428          */
 429         public function setFileHandle( $fh ) {
 430                 $this->fileHandle = $fh;
 431         }
 432
 433         /**
 434          * Get properties passed down from the server info array of the load
 435          * balancer.
 436          *
 437          * @param string $name The entry of the info array to get, or null to get the
 438          *   whole array
 439          *
 440          * @return LoadBalancer|null
 441          */
 442         public function getLBInfo( $name = null ) {
 443                 if ( is_null( $name ) ) {
 444                         return $this->mLBInfo;
 445                 } else {
 446                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 447                                 return $this->mLBInfo[$name];
 448                         } else {
 449                                 return null;
 450                         }
 451                 }
 452         }
 453
 454         /**
 455          * Set the LB info array, or a member of it. If called with one parameter,
 456          * the LB info array is set to that parameter. If it is called with two
 457          * parameters, the member with the given name is set to the given value.
 458          *
 459          * @param $name
 460          * @param $value
 461          */
 462         public function setLBInfo( $name, $value = null ) {
 463                 if ( is_null( $value ) ) {
 464                         $this->mLBInfo = $name;
 465                 } else {
 466                         $this->mLBInfo[$name] = $value;
 467                 }
 468         }
 469
 470         /**
 471          * Set lag time in seconds for a fake slave
 472          *
 473          * @param $lag int
 474          */
 475         public function setFakeSlaveLag( $lag ) {
 476                 $this->mFakeSlaveLag = $lag;
 477         }
 478
 479         /**
 480          * Make this connection a fake master
 481          *
 482          * @param $enabled bool
 483          */
 484         public function setFakeMaster( $enabled = true ) {
 485                 $this->mFakeMaster = $enabled;
 486         }
 487
 488         /**
 489          * Returns true if this database supports (and uses) cascading deletes
 490          *
 491          * @return bool
 492          */
 493         public function cascadingDeletes() {
 494                 return false;
 495         }
 496
 497         /**
 498          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 499          *
 500          * @return bool
 501          */
 502         public function cleanupTriggers() {
 503                 return false;
 504         }
 505
 506         /**
 507          * Returns true if this database is strict about what can be put into an IP field.
 508          * Specifically, it uses a NULL value instead of an empty string.
 509          *
 510          * @return bool
 511          */
 512         public function strictIPs() {
 513                 return false;
 514         }
 515
 516         /**
 517          * Returns true if this database uses timestamps rather than integers
 518          *
 519          * @return bool
 520          */
 521         public function realTimestamps() {
 522                 return false;
 523         }
 524
 525         /**
 526          * Returns true if this database does an implicit sort when doing GROUP BY
 527          *
 528          * @return bool
 529          */
 530         public function implicitGroupby() {
 531                 return true;
 532         }
 533
 534         /**
 535          * Returns true if this database does an implicit order by when the column has an index
 536          * For example: SELECT page_title FROM page LIMIT 1
 537          *
 538          * @return bool
 539          */
 540         public function implicitOrderby() {
 541                 return true;
 542         }
 543
 544         /**
 545          * Returns true if this database can do a native search on IP columns
 546          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 547          *
 548          * @return bool
 549          */
 550         public function searchableIPs() {
 551                 return false;
 552         }
 553
 554         /**
 555          * Returns true if this database can use functional indexes
 556          *
 557          * @return bool
 558          */
 559         public function functionalIndexes() {
 560                 return false;
 561         }
 562
 563         /**
 564          * Return the last query that went through DatabaseBase::query()
 565          * @return String
 566          */
 567         public function lastQuery() {
 568                 return $this->mLastQuery;
 569         }
 570
 571         /**
 572          * Returns true if the connection may have been used for write queries.
 573          * Should return true if unsure.
 574          *
 575          * @return bool
 576          */
 577         public function doneWrites() {
 578                 return $this->mDoneWrites;
 579         }
 580
 581         /**
 582          * Returns true if there is a transaction open with possible write
 583          * queries or transaction pre-commit/idle callbacks waiting on it to finish.
 584          *
 585          * @return bool
 586          */
 587         public function writesOrCallbacksPending() {
 588                 return $this->mTrxLevel && (
 589                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 590                 );
 591         }
 592
 593         /**
 594          * Is a connection to the database open?
 595          * @return Boolean
 596          */
 597         public function isOpen() {
 598                 return $this->mOpened;
 599         }
 600
 601         /**
 602          * Set a flag for this connection
 603          *
 604          * @param $flag Integer: DBO_* constants from Defines.php:
 605          *   - DBO_DEBUG: output some debug info (same as debug())
 606          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 607          *   - DBO_TRX: automatically start transactions
 608          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 609          *       and removes it in command line mode
 610          *   - DBO_PERSISTENT: use persistant database connection
 611          */
 612         public function setFlag( $flag ) {
 613                 global $wgDebugDBTransactions;
 614                 $this->mFlags |= $flag;
 615                 if ( ( $flag & DBO_TRX ) & $wgDebugDBTransactions ) {
 616                         wfDebug( "Implicit transactions are now  disabled.\n" );
 617                 }
 618         }
 619
 620         /**
 621          * Clear a flag for this connection
 622          *
 623          * @param $flag: same as setFlag()'s $flag param
 624          */
 625         public function clearFlag( $flag ) {
 626                 global $wgDebugDBTransactions;
 627                 $this->mFlags &= ~$flag;
 628                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 629                         wfDebug( "Implicit transactions are now disabled.\n" );
 630                 }
 631         }
 632
 633         /**
 634          * Returns a boolean whether the flag $flag is set for this connection
 635          *
 636          * @param $flag: same as setFlag()'s $flag param
 637          * @return Boolean
 638          */
 639         public function getFlag( $flag ) {
 640                 return !!( $this->mFlags & $flag );
 641         }
 642
 643         /**
 644          * General read-only accessor
 645          *
 646          * @param $name string
 647          *
 648          * @return string
 649          */
 650         public function getProperty( $name ) {
 651                 return $this->$name;
 652         }
 653
 654         /**
 655          * @return string
 656          */
 657         public function getWikiID() {
 658                 if ( $this->mTablePrefix ) {
 659                         return "{$this->mDBname}-{$this->mTablePrefix}";
 660                 } else {
 661                         return $this->mDBname;
 662                 }
 663         }
 664
 665         /**
 666          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 667          *
 668          * @return string
 669          */
 670         public function getSchemaPath() {
 671                 global $IP;
 672                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 673                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 674                 } else {
 675                         return "$IP/maintenance/tables.sql";
 676                 }
 677         }
 678
 679 # ------------------------------------------------------------------------------
 680 # Other functions
 681 # ------------------------------------------------------------------------------
 682
 683         /**
 684          * Constructor.
 685          *
 686          * FIXME: It is possible to construct a Database object with no associated
 687          * connection object, by specifying no parameters to __construct(). This
 688          * feature is deprecated and should be removed.
 689          *
 690          * DatabaseBase subclasses should not be constructed directly in external
 691          * code. DatabaseBase::factory() should be used instead.
 692          *
 693          * @param array Parameters passed from DatabaseBase::factory()
 694          */
 695         function __construct( $params = null ) {
 696                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 697
 698                 $this->mTrxAtomicLevels = new SplStack;
 699
 700                 if ( is_array( $params ) ) { // MW 1.22
 701                         $server = $params['host'];
 702                         $user = $params['user'];
 703                         $password = $params['password'];
 704                         $dbName = $params['dbname'];
 705                         $flags = $params['flags'];
 706                         $tablePrefix = $params['tablePrefix'];
 707                         $foreign = $params['foreign'];
 708                 } else { // legacy calling pattern
 709                         wfDeprecated( __METHOD__ . " method called without parameter array.", "1.22" );
 710                         $args = func_get_args();
 711                         $server = isset( $args[0] ) ? $args[0] : false;
 712                         $user = isset( $args[1] ) ? $args[1] : false;
 713                         $password = isset( $args[2] ) ? $args[2] : false;
 714                         $dbName = isset( $args[3] ) ? $args[3] : false;
 715                         $flags = isset( $args[4] ) ? $args[4] : 0;
 716                         $tablePrefix = isset( $args[5] ) ? $args[5] : 'get from global';
 717                         $foreign = isset( $args[6] ) ? $args[6] : false;
 718                 }
 719
 720                 $this->mFlags = $flags;
 721                 if ( $this->mFlags & DBO_DEFAULT ) {
 722                         if ( $wgCommandLineMode ) {
 723                                 $this->mFlags &= ~DBO_TRX;
 724                                 if ( $wgDebugDBTransactions ) {
 725                                         wfDebug( "Implicit transaction open disabled.\n" );
 726                                 }
 727                         } else {
 728                                 $this->mFlags |= DBO_TRX;
 729                                 if ( $wgDebugDBTransactions ) {
 730                                         wfDebug( "Implicit transaction open enabled.\n" );
 731                                 }
 732                         }
 733                 }
 734
 735                 /** Get the default table prefix*/
 736                 if ( $tablePrefix == 'get from global' ) {
 737                         $this->mTablePrefix = $wgDBprefix;
 738                 } else {
 739                         $this->mTablePrefix = $tablePrefix;
 740                 }
 741
 742                 $this->mForeign = $foreign;
 743
 744                 if ( $user ) {
 745                         $this->open( $server, $user, $password, $dbName );
 746                 }
 747         }
 748
 749         /**
 750          * Called by serialize. Throw an exception when DB connection is serialized.
 751          * This causes problems on some database engines because the connection is
 752          * not restored on unserialize.
 753          */
 754         public function __sleep() {
 755                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 756         }
 757
 758         /**
 759          * Given a DB type, construct the name of the appropriate child class of
 760          * DatabaseBase. This is designed to replace all of the manual stuff like:
 761          *      $class = 'Database' . ucfirst( strtolower( $dbType ) );
 762          * as well as validate against the canonical list of DB types we have
 763          *
 764          * This factory function is mostly useful for when you need to connect to a
 765          * database other than the MediaWiki default (such as for external auth,
 766          * an extension, et cetera). Do not use this to connect to the MediaWiki
 767          * database. Example uses in core:
 768          * @see LoadBalancer::reallyOpenConnection()
 769          * @see ForeignDBRepo::getMasterDB()
 770          * @see WebInstaller_DBConnect::execute()
 771          *
 772          * @since 1.18
 773          *
 774          * @param string $dbType A possible DB type
 775          * @param array $p An array of options to pass to the constructor.
 776          *    Valid options are: host, user, password, dbname, flags, tablePrefix, driver
 777          * @return DatabaseBase subclass or null
 778          */
 779         final public static function factory( $dbType, $p = array() ) {
 780                 $canonicalDBTypes = array(
 781                         'mysql'    => array( 'mysqli', 'mysql' ),
 782                         'postgres' => array(),
 783                         'sqlite'   => array(),
 784                         'oracle'   => array(),
 785                         'mssql'    => array(),
 786                 );
 787
 788                 $driver = false;
 789                 $dbType = strtolower( $dbType );
 790                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 791                         $possibleDrivers = $canonicalDBTypes[$dbType];
 792                         if ( !empty( $p['driver'] ) ) {
 793                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 794                                         $driver = $p['driver'];
 795                                 } else {
 796                                         throw new MWException( __METHOD__ .
 797                                                 " cannot construct Database with type '$dbType' and driver '{$p['driver']}'" );
 798                                 }
 799                         } else {
 800                                 foreach ( $possibleDrivers as $posDriver ) {
 801                                         if ( extension_loaded( $posDriver ) ) {
 802                                                 $driver = $posDriver;
 803                                                 break;
 804                                         }
 805                                 }
 806                         }
 807                 } else {
 808                         $driver = $dbType;
 809                 }
 810                 if ( $driver === false ) {
 811                         throw new MWException( __METHOD__ .
 812                                 " no viable database extension found for type '$dbType'" );
 813                 }
 814
 815                 $class = 'Database' . ucfirst( $driver );
 816                 if ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 817                         $params = array(
 818                                 'host' => isset( $p['host'] ) ? $p['host'] : false,
 819                                 'user' => isset( $p['user'] ) ? $p['user'] : false,
 820                                 'password' => isset( $p['password'] ) ? $p['password'] : false,
 821                                 'dbname' => isset( $p['dbname'] ) ? $p['dbname'] : false,
 822                                 'flags' => isset( $p['flags'] ) ? $p['flags'] : 0,
 823                                 'tablePrefix' => isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global',
 824                                 'foreign' => isset( $p['foreign'] ) ? $p['foreign'] : false
 825                         );
 826                         return new $class( $params );
 827                 } else {
 828                         return null;
 829                 }
 830         }
 831
 832         protected function installErrorHandler() {
 833                 $this->mPHPError = false;
 834                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 835                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 836         }
 837
 838         /**
 839          * @return bool|string
 840          */
 841         protected function restoreErrorHandler() {
 842                 restore_error_handler();
 843                 if ( $this->htmlErrors !== false ) {
 844                         ini_set( 'html_errors', $this->htmlErrors );
 845                 }
 846                 if ( $this->mPHPError ) {
 847                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 848                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 849                         return $error;
 850                 } else {
 851                         return false;
 852                 }
 853         }
 854
 855         /**
 856          * @param $errno
 857          * @param $errstr
 858          * @access private
 859          */
 860         public function connectionErrorHandler( $errno, $errstr ) {
 861                 $this->mPHPError = $errstr;
 862         }
 863
 864         /**
 865          * Closes a database connection.
 866          * if it is open : commits any open transactions
 867          *
 868          * @throws MWException
 869          * @return Bool operation success. true if already closed.
 870          */
 871         public function close() {
 872                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 873                         throw new MWException( "Transaction idle callbacks still pending." );
 874                 }
 875                 $this->mOpened = false;
 876                 if ( $this->mConn ) {
 877                         if ( $this->trxLevel() ) {
 878                                 if ( !$this->mTrxAutomatic ) {
 879                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 880                                                 " performing implicit commit before closing connection!" );
 881                                 }
 882
 883                                 $this->commit( __METHOD__, 'flush' );
 884                         }
 885
 886                         $ret = $this->closeConnection();
 887                         $this->mConn = false;
 888                         return $ret;
 889                 } else {
 890                         return true;
 891                 }
 892         }
 893
 894         /**
 895          * Closes underlying database connection
 896          * @since 1.20
 897          * @return bool: Whether connection was closed successfully
 898          */
 899         abstract protected function closeConnection();
 900
 901         /**
 902          * @param string $error fallback error message, used if none is given by DB
 903          * @throws DBConnectionError
 904          */
 905         function reportConnectionError( $error = 'Unknown error' ) {
 906                 $myError = $this->lastError();
 907                 if ( $myError ) {
 908                         $error = $myError;
 909                 }
 910
 911                 # New method
 912                 throw new DBConnectionError( $this, $error );
 913         }
 914
 915         /**
 916          * The DBMS-dependent part of query()
 917          *
 918          * @param  $sql String: SQL query.
 919          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 920          */
 921         abstract protected function doQuery( $sql );
 922
 923         /**
 924          * Determine whether a query writes to the DB.
 925          * Should return true if unsure.
 926          *
 927          * @param $sql string
 928          *
 929          * @return bool
 930          */
 931         public function isWriteQuery( $sql ) {
 932                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 933         }
 934
 935         /**
 936          * Run an SQL query and return the result. Normally throws a DBQueryError
 937          * on failure. If errors are ignored, returns false instead.
 938          *
 939          * In new code, the query wrappers select(), insert(), update(), delete(),
 940          * etc. should be used where possible, since they give much better DBMS
 941          * independence and automatically quote or validate user input in a variety
 942          * of contexts. This function is generally only useful for queries which are
 943          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 944          * as CREATE TABLE.
 945          *
 946          * However, the query wrappers themselves should call this function.
 947          *
 948          * @param  $sql        String: SQL query
 949          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 950          *     comment (you can use __METHOD__ or add some extra info)
 951          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 952          *     maybe best to catch the exception instead?
 953          * @throws MWException
 954          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 955          *     for a successful read query, or false on failure if $tempIgnore set
 956          */
 957         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 958                 global $wgUser, $wgDebugDBTransactions;
 959
 960                 $this->mLastQuery = $sql;
 961                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 962                         # Set a flag indicating that writes have been done
 963                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 964                         $this->mDoneWrites = true;
 965                 }
 966
 967                 # Add a comment for easy SHOW PROCESSLIST interpretation
 968                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 969                         $userName = $wgUser->getName();
 970                         if ( mb_strlen( $userName ) > 15 ) {
 971                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 972                         }
 973                         $userName = str_replace( '/', '', $userName );
 974                 } else {
 975                         $userName = '';
 976                 }
 977
 978                 // Add trace comment to the begin of the sql string, right after the operator.
 979                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 980                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 981
 982                 # If DBO_TRX is set, start a transaction
 983                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 984                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' )
 985                 {
 986                         # Avoid establishing transactions for SHOW and SET statements too -
 987                         # that would delay transaction initializations to once connection
 988                         # is really used by application
 989                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 990                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 991                                 if ( $wgDebugDBTransactions ) {
 992                                         wfDebug( "Implicit transaction start.\n" );
 993                                 }
 994                                 $this->begin( __METHOD__ . " ($fname)" );
 995                                 $this->mTrxAutomatic = true;
 996                         }
 997                 }
 998
 999                 # Keep track of whether the transaction has write queries pending
1000                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
1001                         $this->mTrxDoneWrites = true;
1002                         Profiler::instance()->transactionWritingIn( $this->mServer, $this->mDBname );
1003                 }
1004
1005                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1006                 if ( !Profiler::instance()->isStub() ) {
1007                         # generalizeSQL will probably cut down the query to reasonable
1008                         # logging size most of the time. The substr is really just a sanity check.
1009                         if ( $isMaster ) {
1010                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
1011                                 $totalProf = 'DatabaseBase::query-master';
1012                         } else {
1013                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
1014                                 $totalProf = 'DatabaseBase::query';
1015                         }
1016                         wfProfileIn( $totalProf );
1017                         wfProfileIn( $queryProf );
1018                 }
1019
1020                 if ( $this->debug() ) {
1021                         static $cnt = 0;
1022
1023                         $cnt++;
1024                         $sqlx = substr( $commentedSql, 0, 500 );
1025                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
1026
1027                         $master = $isMaster ? 'master' : 'slave';
1028                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
1029                 }
1030
1031                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
1032
1033                 # Do the query and handle errors
1034                 $ret = $this->doQuery( $commentedSql );
1035
1036                 MWDebug::queryTime( $queryId );
1037
1038                 # Try reconnecting if the connection was lost
1039                 if ( false === $ret && $this->wasErrorReissuable() ) {
1040                         # Transaction is gone, like it or not
1041                         $this->mTrxLevel = 0;
1042                         $this->mTrxIdleCallbacks = array(); // cancel
1043                         $this->mTrxPreCommitCallbacks = array(); // cancel
1044                         wfDebug( "Connection lost, reconnecting...\n" );
1045
1046                         if ( $this->ping() ) {
1047                                 wfDebug( "Reconnected\n" );
1048                                 $sqlx = substr( $commentedSql, 0, 500 );
1049                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
1050                                 global $wgRequestTime;
1051                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
1052                                 if ( $elapsed < 300 ) {
1053                                         # Not a database error to lose a transaction after a minute or two
1054                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
1055                                 }
1056                                 $ret = $this->doQuery( $commentedSql );
1057                         } else {
1058                                 wfDebug( "Failed\n" );
1059                         }
1060                 }
1061
1062                 if ( false === $ret ) {
1063                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1064                 }
1065
1066                 if ( !Profiler::instance()->isStub() ) {
1067                         wfProfileOut( $queryProf );
1068                         wfProfileOut( $totalProf );
1069                 }
1070
1071                 return $this->resultObject( $ret );
1072         }
1073
1074         /**
1075          * Report a query error. Log the error, and if neither the object ignore
1076          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1077          *
1078          * @param $error String
1079          * @param $errno Integer
1080          * @param $sql String
1081          * @param $fname String
1082          * @param $tempIgnore Boolean
1083          * @throws DBQueryError
1084          */
1085         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1086                 # Ignore errors during error handling to avoid infinite recursion
1087                 $ignore = $this->ignoreErrors( true );
1088                 ++$this->mErrorCount;
1089
1090                 if ( $ignore || $tempIgnore ) {
1091                         wfDebug( "SQL ERROR (ignored): $error\n" );
1092                         $this->ignoreErrors( $ignore );
1093                 } else {
1094                         $sql1line = str_replace( "\n", "\\n", $sql );
1095                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
1096                         wfDebug( "SQL ERROR: " . $error . "\n" );
1097                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1098                 }
1099         }
1100
1101         /**
1102          * Intended to be compatible with the PEAR::DB wrapper functions.
1103          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1104          *
1105          * ? = scalar value, quoted as necessary
1106          * ! = raw SQL bit (a function for instance)
1107          * & = filename; reads the file and inserts as a blob
1108          *     (we don't use this though...)
1109          *
1110          * @param $sql string
1111          * @param $func string
1112          *
1113          * @return array
1114          */
1115         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1116                 /* MySQL doesn't support prepared statements (yet), so just
1117                    pack up the query for reference. We'll manually replace
1118                    the bits later. */
1119                 return array( 'query' => $sql, 'func' => $func );
1120         }
1121
1122         /**
1123          * Free a prepared query, generated by prepare().
1124          * @param $prepared
1125          */
1126         protected function freePrepared( $prepared ) {
1127                 /* No-op by default */
1128         }
1129
1130         /**
1131          * Execute a prepared query with the various arguments
1132          * @param string $prepared the prepared sql
1133          * @param $args Mixed: Either an array here, or put scalars as varargs
1134          *
1135          * @return ResultWrapper
1136          */
1137         public function execute( $prepared, $args = null ) {
1138                 if ( !is_array( $args ) ) {
1139                         # Pull the var args
1140                         $args = func_get_args();
1141                         array_shift( $args );
1142                 }
1143
1144                 $sql = $this->fillPrepared( $prepared['query'], $args );
1145
1146                 return $this->query( $sql, $prepared['func'] );
1147         }
1148
1149         /**
1150          * For faking prepared SQL statements on DBs that don't support it directly.
1151          *
1152          * @param string $preparedQuery a 'preparable' SQL statement
1153          * @param array $args of arguments to fill it with
1154          * @return string executable SQL
1155          */
1156         public function fillPrepared( $preparedQuery, $args ) {
1157                 reset( $args );
1158                 $this->preparedArgs =& $args;
1159
1160                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1161                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1162         }
1163
1164         /**
1165          * preg_callback func for fillPrepared()
1166          * The arguments should be in $this->preparedArgs and must not be touched
1167          * while we're doing this.
1168          *
1169          * @param $matches Array
1170          * @throws DBUnexpectedError
1171          * @return String
1172          */
1173         protected function fillPreparedArg( $matches ) {
1174                 switch ( $matches[1] ) {
1175                         case '\\?':
1176                                 return '?';
1177                         case '\\!':
1178                                 return '!';
1179                         case '\\&':
1180                                 return '&';
1181                 }
1182
1183                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1184
1185                 switch ( $matches[1] ) {
1186                         case '?':
1187                                 return $this->addQuotes( $arg );
1188                         case '!':
1189                                 return $arg;
1190                         case '&':
1191                                 # return $this->addQuotes( file_get_contents( $arg ) );
1192                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1193                         default:
1194                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1195                 }
1196         }
1197
1198         /**
1199          * Free a result object returned by query() or select(). It's usually not
1200          * necessary to call this, just use unset() or let the variable holding
1201          * the result object go out of scope.
1202          *
1203          * @param $res Mixed: A SQL result
1204          */
1205         public function freeResult( $res ) {
1206         }
1207
1208         /**
1209          * A SELECT wrapper which returns a single field from a single result row.
1210          *
1211          * Usually throws a DBQueryError on failure. If errors are explicitly
1212          * ignored, returns false on failure.
1213          *
1214          * If no result rows are returned from the query, false is returned.
1215          *
1216          * @param string|array $table Table name. See DatabaseBase::select() for details.
1217          * @param string $var The field name to select. This must be a valid SQL
1218          *   fragment: do not use unvalidated user input.
1219          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1220          * @param string $fname The function name of the caller.
1221          * @param string|array $options The query options. See DatabaseBase::select() for details.
1222          *
1223          * @return bool|mixed The value from the field, or false on failure.
1224          */
1225         public function selectField( $table, $var, $cond = '', $fname = __METHOD__,
1226                 $options = array()
1227         ) {
1228                 if ( !is_array( $options ) ) {
1229                         $options = array( $options );
1230                 }
1231
1232                 $options['LIMIT'] = 1;
1233
1234                 $res = $this->select( $table, $var, $cond, $fname, $options );
1235
1236                 if ( $res === false || !$this->numRows( $res ) ) {
1237                         return false;
1238                 }
1239
1240                 $row = $this->fetchRow( $res );
1241
1242                 if ( $row !== false ) {
1243                         return reset( $row );
1244                 } else {
1245                         return false;
1246                 }
1247         }
1248
1249         /**
1250          * Returns an optional USE INDEX clause to go after the table, and a
1251          * string to go at the end of the query.
1252          *
1253          * @param array $options associative array of options to be turned into
1254          *              an SQL query, valid keys are listed in the function.
1255          * @return Array
1256          * @see DatabaseBase::select()
1257          */
1258         public function makeSelectOptions( $options ) {
1259                 $preLimitTail = $postLimitTail = '';
1260                 $startOpts = '';
1261
1262                 $noKeyOptions = array();
1263
1264                 foreach ( $options as $key => $option ) {
1265                         if ( is_numeric( $key ) ) {
1266                                 $noKeyOptions[$option] = true;
1267                         }
1268                 }
1269
1270                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1271
1272                 $preLimitTail .= $this->makeOrderBy( $options );
1273
1274                 // if (isset($options['LIMIT'])) {
1275                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1276                 //              isset($options['OFFSET']) ? $options['OFFSET']
1277                 //              : false);
1278                 // }
1279
1280                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1281                         $postLimitTail .= ' FOR UPDATE';
1282                 }
1283
1284                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1285                         $postLimitTail .= ' LOCK IN SHARE MODE';
1286                 }
1287
1288                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1289                         $startOpts .= 'DISTINCT';
1290                 }
1291
1292                 # Various MySQL extensions
1293                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1294                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1295                 }
1296
1297                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1298                         $startOpts .= ' HIGH_PRIORITY';
1299                 }
1300
1301                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1302                         $startOpts .= ' SQL_BIG_RESULT';
1303                 }
1304
1305                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1306                         $startOpts .= ' SQL_BUFFER_RESULT';
1307                 }
1308
1309                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1310                         $startOpts .= ' SQL_SMALL_RESULT';
1311                 }
1312
1313                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1314                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1315                 }
1316
1317                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1318                         $startOpts .= ' SQL_CACHE';
1319                 }
1320
1321                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1322                         $startOpts .= ' SQL_NO_CACHE';
1323                 }
1324
1325                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1326                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1327                 } else {
1328                         $useIndex = '';
1329                 }
1330
1331                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1332         }
1333
1334         /**
1335          * Returns an optional GROUP BY with an optional HAVING
1336          *
1337          * @param array $options associative array of options
1338          * @return string
1339          * @see DatabaseBase::select()
1340          * @since 1.21
1341          */
1342         public function makeGroupByWithHaving( $options ) {
1343                 $sql = '';
1344                 if ( isset( $options['GROUP BY'] ) ) {
1345                         $gb = is_array( $options['GROUP BY'] )
1346                                 ? implode( ',', $options['GROUP BY'] )
1347                                 : $options['GROUP BY'];
1348                         $sql .= ' GROUP BY ' . $gb;
1349                 }
1350                 if ( isset( $options['HAVING'] ) ) {
1351                         $having = is_array( $options['HAVING'] )
1352                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1353                                 : $options['HAVING'];
1354                         $sql .= ' HAVING ' . $having;
1355                 }
1356                 return $sql;
1357         }
1358
1359         /**
1360          * Returns an optional ORDER BY
1361          *
1362          * @param array $options associative array of options
1363          * @return string
1364          * @see DatabaseBase::select()
1365          * @since 1.21
1366          */
1367         public function makeOrderBy( $options ) {
1368                 if ( isset( $options['ORDER BY'] ) ) {
1369                         $ob = is_array( $options['ORDER BY'] )
1370                                 ? implode( ',', $options['ORDER BY'] )
1371                                 : $options['ORDER BY'];
1372                         return ' ORDER BY ' . $ob;
1373                 }
1374                 return '';
1375         }
1376
1377         /**
1378          * Execute a SELECT query constructed using the various parameters provided.
1379          * See below for full details of the parameters.
1380          *
1381          * @param string|array $table Table name
1382          * @param string|array $vars Field names
1383          * @param string|array $conds Conditions
1384          * @param string $fname Caller function name
1385          * @param array $options Query options
1386          * @param $join_conds Array Join conditions
1387          *
1388          * @param $table string|array
1389          *
1390          * May be either an array of table names, or a single string holding a table
1391          * name. If an array is given, table aliases can be specified, for example:
1392          *
1393          *    array( 'a' => 'user' )
1394          *
1395          * This includes the user table in the query, with the alias "a" available
1396          * for use in field names (e.g. a.user_name).
1397          *
1398          * All of the table names given here are automatically run through
1399          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1400          * added, and various other table name mappings to be performed.
1401          *
1402          *
1403          * @param $vars string|array
1404          *
1405          * May be either a field name or an array of field names. The field names
1406          * can be complete fragments of SQL, for direct inclusion into the SELECT
1407          * query. If an array is given, field aliases can be specified, for example:
1408          *
1409          *   array( 'maxrev' => 'MAX(rev_id)' )
1410          *
1411          * This includes an expression with the alias "maxrev" in the query.
1412          *
1413          * If an expression is given, care must be taken to ensure that it is
1414          * DBMS-independent.
1415          *
1416          *
1417          * @param $conds string|array
1418          *
1419          * May be either a string containing a single condition, or an array of
1420          * conditions. If an array is given, the conditions constructed from each
1421          * element are combined with AND.
1422          *
1423          * Array elements may take one of two forms:
1424          *
1425          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1426          *   - Elements with a string key are interpreted as equality conditions,
1427          *     where the key is the field name.
1428          *     - If the value of such an array element is a scalar (such as a
1429          *       string), it will be treated as data and thus quoted appropriately.
1430          *       If it is null, an IS NULL clause will be added.
1431          *     - If the value is an array, an IN(...) clause will be constructed,
1432          *       such that the field name may match any of the elements in the
1433          *       array. The elements of the array will be quoted.
1434          *
1435          * Note that expressions are often DBMS-dependent in their syntax.
1436          * DBMS-independent wrappers are provided for constructing several types of
1437          * expression commonly used in condition queries. See:
1438          *    - DatabaseBase::buildLike()
1439          *    - DatabaseBase::conditional()
1440          *
1441          *
1442          * @param $options string|array
1443          *
1444          * Optional: Array of query options. Boolean options are specified by
1445          * including them in the array as a string value with a numeric key, for
1446          * example:
1447          *
1448          *    array( 'FOR UPDATE' )
1449          *
1450          * The supported options are:
1451          *
1452          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1453          *     with LIMIT can theoretically be used for paging through a result set,
1454          *     but this is discouraged in MediaWiki for performance reasons.
1455          *
1456          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1457          *     and then the first rows are taken until the limit is reached. LIMIT
1458          *     is applied to a result set after OFFSET.
1459          *
1460          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1461          *     changed until the next COMMIT.
1462          *
1463          *   - DISTINCT: Boolean: return only unique result rows.
1464          *
1465          *   - GROUP BY: May be either an SQL fragment string naming a field or
1466          *     expression to group by, or an array of such SQL fragments.
1467          *
1468          *   - HAVING: May be either an string containing a HAVING clause or an array of
1469          *     conditions building the HAVING clause. If an array is given, the conditions
1470          *     constructed from each element are combined with AND.
1471          *
1472          *   - ORDER BY: May be either an SQL fragment giving a field name or
1473          *     expression to order by, or an array of such SQL fragments.
1474          *
1475          *   - USE INDEX: This may be either a string giving the index name to use
1476          *     for the query, or an array. If it is an associative array, each key
1477          *     gives the table name (or alias), each value gives the index name to
1478          *     use for that table. All strings are SQL fragments and so should be
1479          *     validated by the caller.
1480          *
1481          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1482          *     instead of SELECT.
1483          *
1484          * And also the following boolean MySQL extensions, see the MySQL manual
1485          * for documentation:
1486          *
1487          *    - LOCK IN SHARE MODE
1488          *    - STRAIGHT_JOIN
1489          *    - HIGH_PRIORITY
1490          *    - SQL_BIG_RESULT
1491          *    - SQL_BUFFER_RESULT
1492          *    - SQL_SMALL_RESULT
1493          *    - SQL_CALC_FOUND_ROWS
1494          *    - SQL_CACHE
1495          *    - SQL_NO_CACHE
1496          *
1497          *
1498          * @param $join_conds string|array
1499          *
1500          * Optional associative array of table-specific join conditions. In the
1501          * most common case, this is unnecessary, since the join condition can be
1502          * in $conds. However, it is useful for doing a LEFT JOIN.
1503          *
1504          * The key of the array contains the table name or alias. The value is an
1505          * array with two elements, numbered 0 and 1. The first gives the type of
1506          * join, the second is an SQL fragment giving the join condition for that
1507          * table. For example:
1508          *
1509          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1510          *
1511          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1512          *   with no rows in it will be returned. If there was a query error, a
1513          *   DBQueryError exception will be thrown, except if the "ignore errors"
1514          *   option was set, in which case false will be returned.
1515          */
1516         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1517                 $options = array(), $join_conds = array() ) {
1518                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1519
1520                 return $this->query( $sql, $fname );
1521         }
1522
1523         /**
1524          * The equivalent of DatabaseBase::select() except that the constructed SQL
1525          * is returned, instead of being immediately executed. This can be useful for
1526          * doing UNION queries, where the SQL text of each query is needed. In general,
1527          * however, callers outside of Database classes should just use select().
1528          *
1529          * @param string|array $table Table name
1530          * @param string|array $vars Field names
1531          * @param string|array $conds Conditions
1532          * @param string $fname Caller function name
1533          * @param string|array $options Query options
1534          * @param $join_conds string|array Join conditions
1535          *
1536          * @return string SQL query string.
1537          * @see DatabaseBase::select()
1538          */
1539         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1540                 $options = array(), $join_conds = array() )
1541         {
1542                 if ( is_array( $vars ) ) {
1543                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1544                 }
1545
1546                 $options = (array)$options;
1547                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1548                         ? $options['USE INDEX']
1549                         : array();
1550
1551                 if ( is_array( $table ) ) {
1552                         $from = ' FROM ' .
1553                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1554                 } elseif ( $table != '' ) {
1555                         if ( $table[0] == ' ' ) {
1556                                 $from = ' FROM ' . $table;
1557                         } else {
1558                                 $from = ' FROM ' .
1559                                         $this->tableNamesWithUseIndexOrJOIN( array( $table ), $useIndexes, array() );
1560                         }
1561                 } else {
1562                         $from = '';
1563                 }
1564
1565                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1566                         $this->makeSelectOptions( $options );
1567
1568                 if ( !empty( $conds ) ) {
1569                         if ( is_array( $conds ) ) {
1570                                 $conds = $this->makeList( $conds, LIST_AND );
1571                         }
1572                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1573                 } else {
1574                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1575                 }
1576
1577                 if ( isset( $options['LIMIT'] ) ) {
1578                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1579                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1580                 }
1581                 $sql = "$sql $postLimitTail";
1582
1583                 if ( isset( $options['EXPLAIN'] ) ) {
1584                         $sql = 'EXPLAIN ' . $sql;
1585                 }
1586
1587                 return $sql;
1588         }
1589
1590         /**
1591          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1592          * that a single row object is returned. If the query returns no rows,
1593          * false is returned.
1594          *
1595          * @param string|array $table Table name
1596          * @param string|array $vars Field names
1597          * @param array $conds Conditions
1598          * @param string $fname Caller function name
1599          * @param string|array $options Query options
1600          * @param $join_conds array|string Join conditions
1601          *
1602          * @return object|bool
1603          */
1604         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1605                 $options = array(), $join_conds = array() )
1606         {
1607                 $options = (array)$options;
1608                 $options['LIMIT'] = 1;
1609                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1610
1611                 if ( $res === false ) {
1612                         return false;
1613                 }
1614
1615                 if ( !$this->numRows( $res ) ) {
1616                         return false;
1617                 }
1618
1619                 $obj = $this->fetchObject( $res );
1620
1621                 return $obj;
1622         }
1623
1624         /**
1625          * Estimate rows in dataset.
1626          *
1627          * MySQL allows you to estimate the number of rows that would be returned
1628          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1629          * index cardinality statistics, and is notoriously inaccurate, especially
1630          * when large numbers of rows have recently been added or deleted.
1631          *
1632          * For DBMSs that don't support fast result size estimation, this function
1633          * will actually perform the SELECT COUNT(*).
1634          *
1635          * Takes the same arguments as DatabaseBase::select().
1636          *
1637          * @param string $table table name
1638          * @param array|string $vars : unused
1639          * @param array|string $conds : filters on the table
1640          * @param string $fname function name for profiling
1641          * @param array $options options for select
1642          * @return Integer: row count
1643          */
1644         public function estimateRowCount( $table, $vars = '*', $conds = '',
1645                 $fname = __METHOD__, $options = array() )
1646         {
1647                 $rows = 0;
1648                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1649
1650                 if ( $res ) {
1651                         $row = $this->fetchRow( $res );
1652                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1653                 }
1654
1655                 return $rows;
1656         }
1657
1658         /**
1659          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1660          * It's only slightly flawed. Don't use for anything important.
1661          *
1662          * @param string $sql A SQL Query
1663          *
1664          * @return string
1665          */
1666         static function generalizeSQL( $sql ) {
1667                 # This does the same as the regexp below would do, but in such a way
1668                 # as to avoid crashing php on some large strings.
1669                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1670
1671                 $sql = str_replace( "\\\\", '', $sql );
1672                 $sql = str_replace( "\\'", '', $sql );
1673                 $sql = str_replace( "\\\"", '', $sql );
1674                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1675                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1676
1677                 # All newlines, tabs, etc replaced by single space
1678                 $sql = preg_replace( '/\s+/', ' ', $sql );
1679
1680                 # All numbers => N
1681                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1682                 $sql = preg_replace( '/-?\d+/s', 'N', $sql );
1683
1684                 return $sql;
1685         }
1686
1687         /**
1688          * Determines whether a field exists in a table
1689          *
1690          * @param string $table table name
1691          * @param string $field filed to check on that table
1692          * @param string $fname calling function name (optional)
1693          * @return Boolean: whether $table has filed $field
1694          */
1695         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1696                 $info = $this->fieldInfo( $table, $field );
1697
1698                 return (bool)$info;
1699         }
1700
1701         /**
1702          * Determines whether an index exists
1703          * Usually throws a DBQueryError on failure
1704          * If errors are explicitly ignored, returns NULL on failure
1705          *
1706          * @param $table
1707          * @param $index
1708          * @param $fname string
1709          *
1710          * @return bool|null
1711          */
1712         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1713                 if ( !$this->tableExists( $table ) ) {
1714                         return null;
1715                 }
1716
1717                 $info = $this->indexInfo( $table, $index, $fname );
1718                 if ( is_null( $info ) ) {
1719                         return null;
1720                 } else {
1721                         return $info !== false;
1722                 }
1723         }
1724
1725         /**
1726          * Query whether a given table exists
1727          *
1728          * @param $table string
1729          * @param $fname string
1730          *
1731          * @return bool
1732          */
1733         public function tableExists( $table, $fname = __METHOD__ ) {
1734                 $table = $this->tableName( $table );
1735                 $old = $this->ignoreErrors( true );
1736                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1737                 $this->ignoreErrors( $old );
1738
1739                 return (bool)$res;
1740         }
1741
1742         /**
1743          * mysql_field_type() wrapper
1744          * @param $res
1745          * @param $index
1746          * @return string
1747          */
1748         public function fieldType( $res, $index ) {
1749                 if ( $res instanceof ResultWrapper ) {
1750                         $res = $res->result;
1751                 }
1752
1753                 return mysql_field_type( $res, $index );
1754         }
1755
1756         /**
1757          * Determines if a given index is unique
1758          *
1759          * @param $table string
1760          * @param $index string
1761          *
1762          * @return bool
1763          */
1764         public function indexUnique( $table, $index ) {
1765                 $indexInfo = $this->indexInfo( $table, $index );
1766
1767                 if ( !$indexInfo ) {
1768                         return null;
1769                 }
1770
1771                 return !$indexInfo[0]->Non_unique;
1772         }
1773
1774         /**
1775          * Helper for DatabaseBase::insert().
1776          *
1777          * @param $options array
1778          * @return string
1779          */
1780         protected function makeInsertOptions( $options ) {
1781                 return implode( ' ', $options );
1782         }
1783
1784         /**
1785          * INSERT wrapper, inserts an array into a table.
1786          *
1787          * $a may be either:
1788          *
1789          *   - A single associative array. The array keys are the field names, and
1790          *     the values are the values to insert. The values are treated as data
1791          *     and will be quoted appropriately. If NULL is inserted, this will be
1792          *     converted to a database NULL.
1793          *   - An array with numeric keys, holding a list of associative arrays.
1794          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1795          *     each subarray must be identical to each other, and in the same order.
1796          *
1797          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1798          * returns success.
1799          *
1800          * $options is an array of options, with boolean options encoded as values
1801          * with numeric keys, in the same style as $options in
1802          * DatabaseBase::select(). Supported options are:
1803          *
1804          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1805          *     any rows which cause duplicate key errors are not inserted. It's
1806          *     possible to determine how many rows were successfully inserted using
1807          *     DatabaseBase::affectedRows().
1808          *
1809          * @param $table   String Table name. This will be passed through
1810          *                 DatabaseBase::tableName().
1811          * @param $a       Array of rows to insert
1812          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1813          * @param array $options of options
1814          *
1815          * @return bool
1816          */
1817         public function insert( $table, $a, $fname = __METHOD__, $options = array() ) {
1818                 # No rows to insert, easy just return now
1819                 if ( !count( $a ) ) {
1820                         return true;
1821                 }
1822
1823                 $table = $this->tableName( $table );
1824
1825                 if ( !is_array( $options ) ) {
1826                         $options = array( $options );
1827                 }
1828
1829                 $fh = null;
1830                 if ( isset( $options['fileHandle'] ) ) {
1831                         $fh = $options['fileHandle'];
1832                 }
1833                 $options = $this->makeInsertOptions( $options );
1834
1835                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1836                         $multi = true;
1837                         $keys = array_keys( $a[0] );
1838                 } else {
1839                         $multi = false;
1840                         $keys = array_keys( $a );
1841                 }
1842
1843                 $sql = 'INSERT ' . $options .
1844                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1845
1846                 if ( $multi ) {
1847                         $first = true;
1848                         foreach ( $a as $row ) {
1849                                 if ( $first ) {
1850                                         $first = false;
1851                                 } else {
1852                                         $sql .= ',';
1853                                 }
1854                                 $sql .= '(' . $this->makeList( $row ) . ')';
1855                         }
1856                 } else {
1857                         $sql .= '(' . $this->makeList( $a ) . ')';
1858                 }
1859
1860                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1861                         return false;
1862                 } elseif ( $fh !== null ) {
1863                         return true;
1864                 }
1865
1866                 return (bool)$this->query( $sql, $fname );
1867         }
1868
1869         /**
1870          * Make UPDATE options for the DatabaseBase::update function
1871          *
1872          * @param array $options The options passed to DatabaseBase::update
1873          * @return string
1874          */
1875         protected function makeUpdateOptions( $options ) {
1876                 if ( !is_array( $options ) ) {
1877                         $options = array( $options );
1878                 }
1879
1880                 $opts = array();
1881
1882                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1883                         $opts[] = $this->lowPriorityOption();
1884                 }
1885
1886                 if ( in_array( 'IGNORE', $options ) ) {
1887                         $opts[] = 'IGNORE';
1888                 }
1889
1890                 return implode( ' ', $opts );
1891         }
1892
1893         /**
1894          * UPDATE wrapper. Takes a condition array and a SET array.
1895          *
1896          * @param $table  String name of the table to UPDATE. This will be passed through
1897          *                DatabaseBase::tableName().
1898          *
1899          * @param array $values  An array of values to SET. For each array element,
1900          *                the key gives the field name, and the value gives the data
1901          *                to set that field to. The data will be quoted by
1902          *                DatabaseBase::addQuotes().
1903          *
1904          * @param $conds  Array:  An array of conditions (WHERE). See
1905          *                DatabaseBase::select() for the details of the format of
1906          *                condition arrays. Use '*' to update all rows.
1907          *
1908          * @param $fname  String: The function name of the caller (from __METHOD__),
1909          *                for logging and profiling.
1910          *
1911          * @param array $options An array of UPDATE options, can be:
1912          *                   - IGNORE: Ignore unique key conflicts
1913          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1914          * @return Boolean
1915          */
1916         function update( $table, $values, $conds, $fname = __METHOD__, $options = array() ) {
1917                 $table = $this->tableName( $table );
1918                 $opts = $this->makeUpdateOptions( $options );
1919                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1920
1921                 if ( $conds !== array() && $conds !== '*' ) {
1922                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1923                 }
1924
1925                 return $this->query( $sql, $fname );
1926         }
1927
1928         /**
1929          * Makes an encoded list of strings from an array
1930          * @param array $a containing the data
1931          * @param int $mode Constant
1932          *      - LIST_COMMA:          comma separated, no field names
1933          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1934          *        the documentation for $conds in DatabaseBase::select().
1935          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1936          *      - LIST_SET:            comma separated with field names, like a SET clause
1937          *      - LIST_NAMES:          comma separated field names
1938          *
1939          * @throws MWException|DBUnexpectedError
1940          * @return string
1941          */
1942         public function makeList( $a, $mode = LIST_COMMA ) {
1943                 if ( !is_array( $a ) ) {
1944                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1945                 }
1946
1947                 $first = true;
1948                 $list = '';
1949
1950                 foreach ( $a as $field => $value ) {
1951                         if ( !$first ) {
1952                                 if ( $mode == LIST_AND ) {
1953                                         $list .= ' AND ';
1954                                 } elseif ( $mode == LIST_OR ) {
1955                                         $list .= ' OR ';
1956                                 } else {
1957                                         $list .= ',';
1958                                 }
1959                         } else {
1960                                 $first = false;
1961                         }
1962
1963                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1964                                 $list .= "($value)";
1965                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1966                                 $list .= "$value";
1967                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1968                                 if ( count( $value ) == 0 ) {
1969                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1970                                 } elseif ( count( $value ) == 1 ) {
1971                                         // Special-case single values, as IN isn't terribly efficient
1972                                         // Don't necessarily assume the single key is 0; we don't
1973                                         // enforce linear numeric ordering on other arrays here.
1974                                         $value = array_values( $value );
1975                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1976                                 } else {
1977                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1978                                 }
1979                         } elseif ( $value === null ) {
1980                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1981                                         $list .= "$field IS ";
1982                                 } elseif ( $mode == LIST_SET ) {
1983                                         $list .= "$field = ";
1984                                 }
1985                                 $list .= 'NULL';
1986                         } else {
1987                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1988                                         $list .= "$field = ";
1989                                 }
1990                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1991                         }
1992                 }
1993
1994                 return $list;
1995         }
1996
1997         /**
1998          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1999          * The keys on each level may be either integers or strings.
2000          *
2001          * @param array $data organized as 2-d
2002          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
2003          * @param string $baseKey field name to match the base-level keys to (eg 'pl_namespace')
2004          * @param string $subKey field name to match the sub-level keys to (eg 'pl_title')
2005          * @return Mixed: string SQL fragment, or false if no items in array.
2006          */
2007         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2008                 $conds = array();
2009
2010                 foreach ( $data as $base => $sub ) {
2011                         if ( count( $sub ) ) {
2012                                 $conds[] = $this->makeList(
2013                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
2014                                         LIST_AND );
2015                         }
2016                 }
2017
2018                 if ( $conds ) {
2019                         return $this->makeList( $conds, LIST_OR );
2020                 } else {
2021                         // Nothing to search for...
2022                         return false;
2023                 }
2024         }
2025
2026         /**
2027          * Return aggregated value alias
2028          *
2029          * @param $valuedata
2030          * @param $valuename string
2031          *
2032          * @return string
2033          */
2034         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2035                 return $valuename;
2036         }
2037
2038         /**
2039          * @param $field
2040          * @return string
2041          */
2042         public function bitNot( $field ) {
2043                 return "(~$field)";
2044         }
2045
2046         /**
2047          * @param $fieldLeft
2048          * @param $fieldRight
2049          * @return string
2050          */
2051         public function bitAnd( $fieldLeft, $fieldRight ) {
2052                 return "($fieldLeft & $fieldRight)";
2053         }
2054
2055         /**
2056          * @param  $fieldLeft
2057          * @param  $fieldRight
2058          * @return string
2059          */
2060         public function bitOr( $fieldLeft, $fieldRight ) {
2061                 return "($fieldLeft | $fieldRight)";
2062         }
2063
2064         /**
2065          * Build a concatenation list to feed into a SQL query
2066          * @param array $stringList list of raw SQL expressions; caller is responsible for any quoting
2067          * @return String
2068          */
2069         public function buildConcat( $stringList ) {
2070                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2071         }
2072
2073         /**
2074          * Change the current database
2075          *
2076          * @todo Explain what exactly will fail if this is not overridden.
2077          *
2078          * @param $db
2079          *
2080          * @return bool Success or failure
2081          */
2082         public function selectDB( $db ) {
2083                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
2084                 # if your database engine supports a concept similar to MySQL's
2085                 # databases you may as well.
2086                 $this->mDBname = $db;
2087                 return true;
2088         }
2089
2090         /**
2091          * Get the current DB name
2092          */
2093         public function getDBname() {
2094                 return $this->mDBname;
2095         }
2096
2097         /**
2098          * Get the server hostname or IP address
2099          */
2100         public function getServer() {
2101                 return $this->mServer;
2102         }
2103
2104         /**
2105          * Format a table name ready for use in constructing an SQL query
2106          *
2107          * This does two important things: it quotes the table names to clean them up,
2108          * and it adds a table prefix if only given a table name with no quotes.
2109          *
2110          * All functions of this object which require a table name call this function
2111          * themselves. Pass the canonical name to such functions. This is only needed
2112          * when calling query() directly.
2113          *
2114          * @param string $name database table name
2115          * @param string $format One of:
2116          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2117          *            so that it can be used in a query.
2118          *   raw - Do not add identifier quotes to the table name
2119          * @return String: full database name
2120          */
2121         public function tableName( $name, $format = 'quoted' ) {
2122                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
2123                 # Skip the entire process when we have a string quoted on both ends.
2124                 # Note that we check the end so that we will still quote any use of
2125                 # use of `database`.table. But won't break things if someone wants
2126                 # to query a database table with a dot in the name.
2127                 if ( $this->isQuotedIdentifier( $name ) ) {
2128                         return $name;
2129                 }
2130
2131                 # Lets test for any bits of text that should never show up in a table
2132                 # name. Basically anything like JOIN or ON which are actually part of
2133                 # SQL queries, but may end up inside of the table value to combine
2134                 # sql. Such as how the API is doing.
2135                 # Note that we use a whitespace test rather than a \b test to avoid
2136                 # any remote case where a word like on may be inside of a table name
2137                 # surrounded by symbols which may be considered word breaks.
2138                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2139                         return $name;
2140                 }
2141
2142                 # Split database and table into proper variables.
2143                 # We reverse the explode so that database.table and table both output
2144                 # the correct table.
2145                 $dbDetails = explode( '.', $name, 2 );
2146                 if ( count( $dbDetails ) == 2 ) {
2147                         list( $database, $table ) = $dbDetails;
2148                         # We don't want any prefix added in this case
2149                         $prefix = '';
2150                 } else {
2151                         list( $table ) = $dbDetails;
2152                         if ( $wgSharedDB !== null # We have a shared database
2153                                 && $this->mForeign == false # We're not working on a foreign database
2154                                 && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
2155                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2156                         ) {
2157                                 $database = $wgSharedDB;
2158                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2159                         } else {
2160                                 $database = null;
2161                                 $prefix = $this->mTablePrefix; # Default prefix
2162                         }
2163                 }
2164
2165                 # Quote $table and apply the prefix if not quoted.
2166                 $tableName = "{$prefix}{$table}";
2167                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) ) {
2168                         $tableName = $this->addIdentifierQuotes( $tableName );
2169                 }
2170
2171                 # Quote $database and merge it with the table name if needed
2172                 if ( $database !== null ) {
2173                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2174                                 $database = $this->addIdentifierQuotes( $database );
2175                         }
2176                         $tableName = $database . '.' . $tableName;
2177                 }
2178
2179                 return $tableName;
2180         }
2181
2182         /**
2183          * Fetch a number of table names into an array
2184          * This is handy when you need to construct SQL for joins
2185          *
2186          * Example:
2187          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2188          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2189          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2190          *
2191          * @return array
2192          */
2193         public function tableNames() {
2194                 $inArray = func_get_args();
2195                 $retVal = array();
2196
2197                 foreach ( $inArray as $name ) {
2198                         $retVal[$name] = $this->tableName( $name );
2199                 }
2200
2201                 return $retVal;
2202         }
2203
2204         /**
2205          * Fetch a number of table names into an zero-indexed numerical array
2206          * This is handy when you need to construct SQL for joins
2207          *
2208          * Example:
2209          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2210          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2211          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2212          *
2213          * @return array
2214          */
2215         public function tableNamesN() {
2216                 $inArray = func_get_args();
2217                 $retVal = array();
2218
2219                 foreach ( $inArray as $name ) {
2220                         $retVal[] = $this->tableName( $name );
2221                 }
2222
2223                 return $retVal;
2224         }
2225
2226         /**
2227          * Get an aliased table name
2228          * e.g. tableName AS newTableName
2229          *
2230          * @param string $name Table name, see tableName()
2231          * @param string|bool $alias Alias (optional)
2232          * @return string SQL name for aliased table. Will not alias a table to its own name
2233          */
2234         public function tableNameWithAlias( $name, $alias = false ) {
2235                 if ( !$alias || $alias == $name ) {
2236                         return $this->tableName( $name );
2237                 } else {
2238                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2239                 }
2240         }
2241
2242         /**
2243          * Gets an array of aliased table names
2244          *
2245          * @param $tables array( [alias] => table )
2246          * @return array of strings, see tableNameWithAlias()
2247          */
2248         public function tableNamesWithAlias( $tables ) {
2249                 $retval = array();
2250                 foreach ( $tables as $alias => $table ) {
2251                         if ( is_numeric( $alias ) ) {
2252                                 $alias = $table;
2253                         }
2254                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2255                 }
2256                 return $retval;
2257         }
2258
2259         /**
2260          * Get an aliased field name
2261          * e.g. fieldName AS newFieldName
2262          *
2263          * @param string $name Field name
2264          * @param string|bool $alias Alias (optional)
2265          * @return string SQL name for aliased field. Will not alias a field to its own name
2266          */
2267         public function fieldNameWithAlias( $name, $alias = false ) {
2268                 if ( !$alias || (string)$alias === (string)$name ) {
2269                         return $name;
2270                 } else {
2271                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2272                 }
2273         }
2274
2275         /**
2276          * Gets an array of aliased field names
2277          *
2278          * @param $fields array( [alias] => field )
2279          * @return array of strings, see fieldNameWithAlias()
2280          */
2281         public function fieldNamesWithAlias( $fields ) {
2282                 $retval = array();
2283                 foreach ( $fields as $alias => $field ) {
2284                         if ( is_numeric( $alias ) ) {
2285                                 $alias = $field;
2286                         }
2287                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2288                 }
2289                 return $retval;
2290         }
2291
2292         /**
2293          * Get the aliased table name clause for a FROM clause
2294          * which might have a JOIN and/or USE INDEX clause
2295          *
2296          * @param array $tables ( [alias] => table )
2297          * @param $use_index array Same as for select()
2298          * @param $join_conds array Same as for select()
2299          * @return string
2300          */
2301         protected function tableNamesWithUseIndexOrJOIN(
2302                 $tables, $use_index = array(), $join_conds = array()
2303         ) {
2304                 $ret = array();
2305                 $retJOIN = array();
2306                 $use_index = (array)$use_index;
2307                 $join_conds = (array)$join_conds;
2308
2309                 foreach ( $tables as $alias => $table ) {
2310                         if ( !is_string( $alias ) ) {
2311                                 // No alias? Set it equal to the table name
2312                                 $alias = $table;
2313                         }
2314                         // Is there a JOIN clause for this table?
2315                         if ( isset( $join_conds[$alias] ) ) {
2316                                 list( $joinType, $conds ) = $join_conds[$alias];
2317                                 $tableClause = $joinType;
2318                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2319                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2320                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2321                                         if ( $use != '' ) {
2322                                                 $tableClause .= ' ' . $use;
2323                                         }
2324                                 }
2325                                 $on = $this->makeList( (array)$conds, LIST_AND );
2326                                 if ( $on != '' ) {
2327                                         $tableClause .= ' ON (' . $on . ')';
2328                                 }
2329
2330                                 $retJOIN[] = $tableClause;
2331                         // Is there an INDEX clause for this table?
2332                         } elseif ( isset( $use_index[$alias] ) ) {
2333                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2334                                 $tableClause .= ' ' . $this->useIndexClause(
2335                                         implode( ',', (array)$use_index[$alias] ) );
2336
2337                                 $ret[] = $tableClause;
2338                         } else {
2339                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2340
2341                                 $ret[] = $tableClause;
2342                         }
2343                 }
2344
2345                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2346                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2347                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2348
2349                 // Compile our final table clause
2350                 return implode( ' ', array( $implicitJoins, $explicitJoins ) );
2351         }
2352
2353         /**
2354          * Get the name of an index in a given table
2355          *
2356          * @param $index
2357          *
2358          * @return string
2359          */
2360         protected function indexName( $index ) {
2361                 // Backwards-compatibility hack
2362                 $renamed = array(
2363                         'ar_usertext_timestamp' => 'usertext_timestamp',
2364                         'un_user_id' => 'user_id',
2365                         'un_user_ip' => 'user_ip',
2366                 );
2367
2368                 if ( isset( $renamed[$index] ) ) {
2369                         return $renamed[$index];
2370                 } else {
2371                         return $index;
2372                 }
2373         }
2374
2375         /**
2376          * Adds quotes and backslashes.
2377          *
2378          * @param $s string
2379          *
2380          * @return string
2381          */
2382         public function addQuotes( $s ) {
2383                 if ( $s === null ) {
2384                         return 'NULL';
2385                 } else {
2386                         # This will also quote numeric values. This should be harmless,
2387                         # and protects against weird problems that occur when they really
2388                         # _are_ strings such as article titles and string->number->string
2389                         # conversion is not 1:1.
2390                         return "'" . $this->strencode( $s ) . "'";
2391                 }
2392         }
2393
2394         /**
2395          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2396          * MySQL uses `backticks` while basically everything else uses double quotes.
2397          * Since MySQL is the odd one out here the double quotes are our generic
2398          * and we implement backticks in DatabaseMysql.
2399          *
2400          * @param $s string
2401          *
2402          * @return string
2403          */
2404         public function addIdentifierQuotes( $s ) {
2405                 return '"' . str_replace( '"', '""', $s ) . '"';
2406         }
2407
2408         /**
2409          * Returns if the given identifier looks quoted or not according to
2410          * the database convention for quoting identifiers .
2411          *
2412          * @param $name string
2413          *
2414          * @return boolean
2415          */
2416         public function isQuotedIdentifier( $name ) {
2417                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2418         }
2419
2420         /**
2421          * @param $s string
2422          * @return string
2423          */
2424         protected function escapeLikeInternal( $s ) {
2425                 $s = str_replace( '\\', '\\\\', $s );
2426                 $s = $this->strencode( $s );
2427                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2428
2429                 return $s;
2430         }
2431
2432         /**
2433          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2434          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2435          * Alternatively, the function could be provided with an array of aforementioned parameters.
2436          *
2437          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2438          * for subpages of 'My page title'.
2439          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2440          *
2441          * @since 1.16
2442          * @return String: fully built LIKE statement
2443          */
2444         public function buildLike() {
2445                 $params = func_get_args();
2446
2447                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2448                         $params = $params[0];
2449                 }
2450
2451                 $s = '';
2452
2453                 foreach ( $params as $value ) {
2454                         if ( $value instanceof LikeMatch ) {
2455                                 $s .= $value->toString();
2456                         } else {
2457                                 $s .= $this->escapeLikeInternal( $value );
2458                         }
2459                 }
2460
2461                 return " LIKE '" . $s . "' ";
2462         }
2463
2464         /**
2465          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2466          *
2467          * @return LikeMatch
2468          */
2469         public function anyChar() {
2470                 return new LikeMatch( '_' );
2471         }
2472
2473         /**
2474          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2475          *
2476          * @return LikeMatch
2477          */
2478         public function anyString() {
2479                 return new LikeMatch( '%' );
2480         }
2481
2482         /**
2483          * Returns an appropriately quoted sequence value for inserting a new row.
2484          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2485          * subclass will return an integer, and save the value for insertId()
2486          *
2487          * Any implementation of this function should *not* involve reusing
2488          * sequence numbers created for rolled-back transactions.
2489          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2490          * @param $seqName string
2491          * @return null
2492          */
2493         public function nextSequenceValue( $seqName ) {
2494                 return null;
2495         }
2496
2497         /**
2498          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2499          * is only needed because a) MySQL must be as efficient as possible due to
2500          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2501          * which index to pick.  Anyway, other databases might have different
2502          * indexes on a given table.  So don't bother overriding this unless you're
2503          * MySQL.
2504          * @param $index
2505          * @return string
2506          */
2507         public function useIndexClause( $index ) {
2508                 return '';
2509         }
2510
2511         /**
2512          * REPLACE query wrapper.
2513          *
2514          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2515          * except that when there is a duplicate key error, the old row is deleted
2516          * and the new row is inserted in its place.
2517          *
2518          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2519          * perform the delete, we need to know what the unique indexes are so that
2520          * we know how to find the conflicting rows.
2521          *
2522          * It may be more efficient to leave off unique indexes which are unlikely
2523          * to collide. However if you do this, you run the risk of encountering
2524          * errors which wouldn't have occurred in MySQL.
2525          *
2526          * @param string $table The table to replace the row(s) in.
2527          * @param array $rows Can be either a single row to insert, or multiple rows,
2528          *    in the same format as for DatabaseBase::insert()
2529          * @param array $uniqueIndexes is an array of indexes. Each element may be either
2530          *    a field name or an array of field names
2531          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2532          */
2533         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2534                 $quotedTable = $this->tableName( $table );
2535
2536                 if ( count( $rows ) == 0 ) {
2537                         return;
2538                 }
2539
2540                 # Single row case
2541                 if ( !is_array( reset( $rows ) ) ) {
2542                         $rows = array( $rows );
2543                 }
2544
2545                 foreach ( $rows as $row ) {
2546                         # Delete rows which collide
2547                         if ( $uniqueIndexes ) {
2548                                 $sql = "DELETE FROM $quotedTable WHERE ";
2549                                 $first = true;
2550                                 foreach ( $uniqueIndexes as $index ) {
2551                                         if ( $first ) {
2552                                                 $first = false;
2553                                                 $sql .= '( ';
2554                                         } else {
2555                                                 $sql .= ' ) OR ( ';
2556                                         }
2557                                         if ( is_array( $index ) ) {
2558                                                 $first2 = true;
2559                                                 foreach ( $index as $col ) {
2560                                                         if ( $first2 ) {
2561                                                                 $first2 = false;
2562                                                         } else {
2563                                                                 $sql .= ' AND ';
2564                                                         }
2565                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2566                                                 }
2567                                         } else {
2568                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2569                                         }
2570                                 }
2571                                 $sql .= ' )';
2572                                 $this->query( $sql, $fname );
2573                         }
2574
2575                         # Now insert the row
2576                         $this->insert( $table, $row, $fname );
2577                 }
2578         }
2579
2580         /**
2581          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2582          * statement.
2583          *
2584          * @param string $table Table name
2585          * @param array $rows Rows to insert
2586          * @param string $fname Caller function name
2587          *
2588          * @return ResultWrapper
2589          */
2590         protected function nativeReplace( $table, $rows, $fname ) {
2591                 $table = $this->tableName( $table );
2592
2593                 # Single row case
2594                 if ( !is_array( reset( $rows ) ) ) {
2595                         $rows = array( $rows );
2596                 }
2597
2598                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2599                 $first = true;
2600
2601                 foreach ( $rows as $row ) {
2602                         if ( $first ) {
2603                                 $first = false;
2604                         } else {
2605                                 $sql .= ',';
2606                         }
2607
2608                         $sql .= '(' . $this->makeList( $row ) . ')';
2609                 }
2610
2611                 return $this->query( $sql, $fname );
2612         }
2613
2614         /**
2615          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
2616          *
2617          * This updates any conflicting rows (according to the unique indexes) using
2618          * the provided SET clause and inserts any remaining (non-conflicted) rows.
2619          *
2620          * $rows may be either:
2621          *   - A single associative array. The array keys are the field names, and
2622          *     the values are the values to insert. The values are treated as data
2623          *     and will be quoted appropriately. If NULL is inserted, this will be
2624          *     converted to a database NULL.
2625          *   - An array with numeric keys, holding a list of associative arrays.
2626          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
2627          *     each subarray must be identical to each other, and in the same order.
2628          *
2629          * It may be more efficient to leave off unique indexes which are unlikely
2630          * to collide. However if you do this, you run the risk of encountering
2631          * errors which wouldn't have occurred in MySQL.
2632          *
2633          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
2634          * returns success.
2635          *
2636          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
2637          * @param array $rows A single row or list of rows to insert
2638          * @param array $uniqueIndexes List of single field names or field name tuples
2639          * @param array $set An array of values to SET. For each array element,
2640          *                the key gives the field name, and the value gives the data
2641          *                to set that field to. The data will be quoted by
2642          *                DatabaseBase::addQuotes().
2643          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2644          * @param array $options of options
2645          *
2646          * @return bool
2647          * @since 1.22
2648          */
2649         public function upsert(
2650                 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
2651         ) {
2652                 if ( !count( $rows ) ) {
2653                         return true; // nothing to do
2654                 }
2655                 $rows = is_array( reset( $rows ) ) ? $rows : array( $rows );
2656
2657                 if ( count( $uniqueIndexes ) ) {
2658                         $clauses = array(); // list WHERE clauses that each identify a single row
2659                         foreach ( $rows as $row ) {
2660                                 foreach ( $uniqueIndexes as $index ) {
2661                                         $index = is_array( $index ) ? $index : array( $index ); // columns
2662                                         $rowKey = array(); // unique key to this row
2663                                         foreach ( $index as $column ) {
2664                                                 $rowKey[$column] = $row[$column];
2665                                         }
2666                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2667                                 }
2668                         }
2669                         $where = array( $this->makeList( $clauses, LIST_OR ) );
2670                 } else {
2671                         $where = false;
2672                 }
2673
2674                 $useTrx = !$this->mTrxLevel;
2675                 if ( $useTrx ) {
2676                         $this->begin( $fname );
2677                 }
2678                 try {
2679                         # Update any existing conflicting row(s)
2680                         if ( $where !== false ) {
2681                                 $ok = $this->update( $table, $set, $where, $fname );
2682                         } else {
2683                                 $ok = true;
2684                         }
2685                         # Now insert any non-conflicting row(s)
2686                         $ok = $this->insert( $table, $rows, $fname, array( 'IGNORE' ) ) && $ok;
2687                 } catch ( Exception $e ) {
2688                         if ( $useTrx ) {
2689                                 $this->rollback( $fname );
2690                         }
2691                         throw $e;
2692                 }
2693                 if ( $useTrx ) {
2694                         $this->commit( $fname );
2695                 }
2696
2697                 return $ok;
2698         }
2699
2700         /**
2701          * DELETE where the condition is a join.
2702          *
2703          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2704          * we use sub-selects
2705          *
2706          * For safety, an empty $conds will not delete everything. If you want to
2707          * delete all rows where the join condition matches, set $conds='*'.
2708          *
2709          * DO NOT put the join condition in $conds.
2710          *
2711          * @param $delTable   String: The table to delete from.
2712          * @param $joinTable  String: The other table.
2713          * @param $delVar     String: The variable to join on, in the first table.
2714          * @param $joinVar    String: The variable to join on, in the second table.
2715          * @param $conds      Array: Condition array of field names mapped to variables,
2716          *                    ANDed together in the WHERE clause
2717          * @param $fname      String: Calling function name (use __METHOD__) for
2718          *                    logs/profiling
2719          * @throws DBUnexpectedError
2720          */
2721         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2722                 $fname = __METHOD__ )
2723         {
2724                 if ( !$conds ) {
2725                         throw new DBUnexpectedError( $this,
2726                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2727                 }
2728
2729                 $delTable = $this->tableName( $delTable );
2730                 $joinTable = $this->tableName( $joinTable );
2731                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2732                 if ( $conds != '*' ) {
2733                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2734                 }
2735                 $sql .= ')';
2736
2737                 $this->query( $sql, $fname );
2738         }
2739
2740         /**
2741          * Returns the size of a text field, or -1 for "unlimited"
2742          *
2743          * @param $table string
2744          * @param $field string
2745          *
2746          * @return int
2747          */
2748         public function textFieldSize( $table, $field ) {
2749                 $table = $this->tableName( $table );
2750                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2751                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2752                 $row = $this->fetchObject( $res );
2753
2754                 $m = array();
2755
2756                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2757                         $size = $m[1];
2758                 } else {
2759                         $size = -1;
2760                 }
2761
2762                 return $size;
2763         }
2764
2765         /**
2766          * A string to insert into queries to show that they're low-priority, like
2767          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2768          * string and nothing bad should happen.
2769          *
2770          * @return string Returns the text of the low priority option if it is
2771          *   supported, or a blank string otherwise
2772          */
2773         public function lowPriorityOption() {
2774                 return '';
2775         }
2776
2777         /**
2778          * DELETE query wrapper.
2779          *
2780          * @param array $table Table name
2781          * @param string|array $conds of conditions. See $conds in DatabaseBase::select() for
2782          *               the format. Use $conds == "*" to delete all rows
2783          * @param string $fname name of the calling function
2784          *
2785          * @throws DBUnexpectedError
2786          * @return bool|ResultWrapper
2787          */
2788         public function delete( $table, $conds, $fname = __METHOD__ ) {
2789                 if ( !$conds ) {
2790                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2791                 }
2792
2793                 $table = $this->tableName( $table );
2794                 $sql = "DELETE FROM $table";
2795
2796                 if ( $conds != '*' ) {
2797                         if ( is_array( $conds ) ) {
2798                                 $conds = $this->makeList( $conds, LIST_AND );
2799                         }
2800                         $sql .= ' WHERE ' . $conds;
2801                 }
2802
2803                 return $this->query( $sql, $fname );
2804         }
2805
2806         /**
2807          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2808          * into another table.
2809          *
2810          * @param string $destTable The table name to insert into
2811          * @param string|array $srcTable May be either a table name, or an array of table names
2812          *    to include in a join.
2813          *
2814          * @param array $varMap must be an associative array of the form
2815          *    array( 'dest1' => 'source1', ...). Source items may be literals
2816          *    rather than field names, but strings should be quoted with
2817          *    DatabaseBase::addQuotes()
2818          *
2819          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2820          *    the details of the format of condition arrays. May be "*" to copy the
2821          *    whole table.
2822          *
2823          * @param string $fname The function name of the caller, from __METHOD__
2824          *
2825          * @param array $insertOptions Options for the INSERT part of the query, see
2826          *    DatabaseBase::insert() for details.
2827          * @param array $selectOptions Options for the SELECT part of the query, see
2828          *    DatabaseBase::select() for details.
2829          *
2830          * @return ResultWrapper
2831          */
2832         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2833                 $fname = __METHOD__,
2834                 $insertOptions = array(), $selectOptions = array() )
2835         {
2836                 $destTable = $this->tableName( $destTable );
2837
2838                 if ( is_array( $insertOptions ) ) {
2839                         $insertOptions = implode( ' ', $insertOptions );
2840                 }
2841
2842                 if ( !is_array( $selectOptions ) ) {
2843                         $selectOptions = array( $selectOptions );
2844                 }
2845
2846                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2847
2848                 if ( is_array( $srcTable ) ) {
2849                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2850                 } else {
2851                         $srcTable = $this->tableName( $srcTable );
2852                 }
2853
2854                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2855                         " SELECT $startOpts " . implode( ',', $varMap ) .
2856                         " FROM $srcTable $useIndex ";
2857
2858                 if ( $conds != '*' ) {
2859                         if ( is_array( $conds ) ) {
2860                                 $conds = $this->makeList( $conds, LIST_AND );
2861                         }
2862                         $sql .= " WHERE $conds";
2863                 }
2864
2865                 $sql .= " $tailOpts";
2866
2867                 return $this->query( $sql, $fname );
2868         }
2869
2870         /**
2871          * Construct a LIMIT query with optional offset.  This is used for query
2872          * pages.  The SQL should be adjusted so that only the first $limit rows
2873          * are returned.  If $offset is provided as well, then the first $offset
2874          * rows should be discarded, and the next $limit rows should be returned.
2875          * If the result of the query is not ordered, then the rows to be returned
2876          * are theoretically arbitrary.
2877          *
2878          * $sql is expected to be a SELECT, if that makes a difference.
2879          *
2880          * The version provided by default works in MySQL and SQLite.  It will very
2881          * likely need to be overridden for most other DBMSes.
2882          *
2883          * @param string $sql SQL query we will append the limit too
2884          * @param $limit Integer the SQL limit
2885          * @param $offset Integer|bool the SQL offset (default false)
2886          *
2887          * @throws DBUnexpectedError
2888          * @return string
2889          */
2890         public function limitResult( $sql, $limit, $offset = false ) {
2891                 if ( !is_numeric( $limit ) ) {
2892                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2893                 }
2894                 return "$sql LIMIT "
2895                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2896                         . "{$limit} ";
2897         }
2898
2899         /**
2900          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2901          * within the UNION construct.
2902          * @return Boolean
2903          */
2904         public function unionSupportsOrderAndLimit() {
2905                 return true; // True for almost every DB supported
2906         }
2907
2908         /**
2909          * Construct a UNION query
2910          * This is used for providing overload point for other DB abstractions
2911          * not compatible with the MySQL syntax.
2912          * @param array $sqls SQL statements to combine
2913          * @param $all Boolean: use UNION ALL
2914          * @return String: SQL fragment
2915          */
2916         public function unionQueries( $sqls, $all ) {
2917                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2918                 return '(' . implode( $glue, $sqls ) . ')';
2919         }
2920
2921         /**
2922          * Returns an SQL expression for a simple conditional.  This doesn't need
2923          * to be overridden unless CASE isn't supported in your DBMS.
2924          *
2925          * @param string|array $cond SQL expression which will result in a boolean value
2926          * @param string $trueVal SQL expression to return if true
2927          * @param string $falseVal SQL expression to return if false
2928          * @return String: SQL fragment
2929          */
2930         public function conditional( $cond, $trueVal, $falseVal ) {
2931                 if ( is_array( $cond ) ) {
2932                         $cond = $this->makeList( $cond, LIST_AND );
2933                 }
2934                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2935         }
2936
2937         /**
2938          * Returns a comand for str_replace function in SQL query.
2939          * Uses REPLACE() in MySQL
2940          *
2941          * @param string $orig column to modify
2942          * @param string $old column to seek
2943          * @param string $new column to replace with
2944          *
2945          * @return string
2946          */
2947         public function strreplace( $orig, $old, $new ) {
2948                 return "REPLACE({$orig}, {$old}, {$new})";
2949         }
2950
2951         /**
2952          * Determines how long the server has been up
2953          * STUB
2954          *
2955          * @return int
2956          */
2957         public function getServerUptime() {
2958                 return 0;
2959         }
2960
2961         /**
2962          * Determines if the last failure was due to a deadlock
2963          * STUB
2964          *
2965          * @return bool
2966          */
2967         public function wasDeadlock() {
2968                 return false;
2969         }
2970
2971         /**
2972          * Determines if the last failure was due to a lock timeout
2973          * STUB
2974          *
2975          * @return bool
2976          */
2977         public function wasLockTimeout() {
2978                 return false;
2979         }
2980
2981         /**
2982          * Determines if the last query error was something that should be dealt
2983          * with by pinging the connection and reissuing the query.
2984          * STUB
2985          *
2986          * @return bool
2987          */
2988         public function wasErrorReissuable() {
2989                 return false;
2990         }
2991
2992         /**
2993          * Determines if the last failure was due to the database being read-only.
2994          * STUB
2995          *
2996          * @return bool
2997          */
2998         public function wasReadOnlyError() {
2999                 return false;
3000         }
3001
3002         /**
3003          * Perform a deadlock-prone transaction.
3004          *
3005          * This function invokes a callback function to perform a set of write
3006          * queries. If a deadlock occurs during the processing, the transaction
3007          * will be rolled back and the callback function will be called again.
3008          *
3009          * Usage:
3010          *   $dbw->deadlockLoop( callback, ... );
3011          *
3012          * Extra arguments are passed through to the specified callback function.
3013          *
3014          * Returns whatever the callback function returned on its successful,
3015          * iteration, or false on error, for example if the retry limit was
3016          * reached.
3017          *
3018          * @return bool
3019          */
3020         public function deadlockLoop() {
3021                 $this->begin( __METHOD__ );
3022                 $args = func_get_args();
3023                 $function = array_shift( $args );
3024                 $oldIgnore = $this->ignoreErrors( true );
3025                 $tries = self::DEADLOCK_TRIES;
3026
3027                 if ( is_array( $function ) ) {
3028                         $fname = $function[0];
3029                 } else {
3030                         $fname = $function;
3031                 }
3032
3033                 do {
3034                         $retVal = call_user_func_array( $function, $args );
3035                         $error = $this->lastError();
3036                         $errno = $this->lastErrno();
3037                         $sql = $this->lastQuery();
3038
3039                         if ( $errno ) {
3040                                 if ( $this->wasDeadlock() ) {
3041                                         # Retry
3042                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3043                                 } else {
3044                                         $this->reportQueryError( $error, $errno, $sql, $fname );
3045                                 }
3046                         }
3047                 } while ( $this->wasDeadlock() && --$tries > 0 );
3048
3049                 $this->ignoreErrors( $oldIgnore );
3050
3051                 if ( $tries <= 0 ) {
3052                         $this->rollback( __METHOD__ );
3053                         $this->reportQueryError( $error, $errno, $sql, $fname );
3054                         return false;
3055                 } else {
3056                         $this->commit( __METHOD__ );
3057                         return $retVal;
3058                 }
3059         }
3060
3061         /**
3062          * Wait for the slave to catch up to a given master position.
3063          *
3064          * @param $pos DBMasterPos object
3065          * @param $timeout Integer: the maximum number of seconds to wait for
3066          *   synchronisation
3067          *
3068          * @return integer: zero if the slave was past that position already,
3069          *   greater than zero if we waited for some period of time, less than
3070          *   zero if we timed out.
3071          */
3072         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3073                 wfProfileIn( __METHOD__ );
3074
3075                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3076                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
3077
3078                         if ( $wait > $timeout * 1e6 ) {
3079                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
3080                                 wfProfileOut( __METHOD__ );
3081                                 return -1;
3082                         } elseif ( $wait > 0 ) {
3083                                 wfDebug( "Fake slave waiting $wait us\n" );
3084                                 usleep( $wait );
3085                                 wfProfileOut( __METHOD__ );
3086                                 return 1;
3087                         } else {
3088                                 wfDebug( "Fake slave up to date ($wait us)\n" );
3089                                 wfProfileOut( __METHOD__ );
3090                                 return 0;
3091                         }
3092                 }
3093
3094                 wfProfileOut( __METHOD__ );
3095
3096                 # Real waits are implemented in the subclass.
3097                 return 0;
3098         }
3099
3100         /**
3101          * Get the replication position of this slave
3102          *
3103          * @return DBMasterPos, or false if this is not a slave.
3104          */
3105         public function getSlavePos() {
3106                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3107                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
3108                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
3109                         return $pos;
3110                 } else {
3111                         # Stub
3112                         return false;
3113                 }
3114         }
3115
3116         /**
3117          * Get the position of this master
3118          *
3119          * @return DBMasterPos, or false if this is not a master
3120          */
3121         public function getMasterPos() {
3122                 if ( $this->mFakeMaster ) {
3123                         return new MySQLMasterPos( 'fake', microtime( true ) );
3124                 } else {
3125                         return false;
3126                 }
3127         }
3128
3129         /**
3130          * Run an anonymous function as soon as there is no transaction pending.
3131          * If there is a transaction and it is rolled back, then the callback is cancelled.
3132          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
3133          * Callbacks must commit any transactions that they begin.
3134          *
3135          * This is useful for updates to different systems or when separate transactions are needed.
3136          * For example, one might want to enqueue jobs into a system outside the database, but only
3137          * after the database is updated so that the jobs will see the data when they actually run.
3138          * It can also be used for updates that easily cause deadlocks if locks are held too long.
3139          *
3140          * @param callable $callback
3141          * @since 1.20
3142          */
3143         final public function onTransactionIdle( $callback ) {
3144                 $this->mTrxIdleCallbacks[] = array( $callback, wfGetCaller() );
3145                 if ( !$this->mTrxLevel ) {
3146                         $this->runOnTransactionIdleCallbacks();
3147                 }
3148         }
3149
3150         /**
3151          * Run an anonymous function before the current transaction commits or now if there is none.
3152          * If there is a transaction and it is rolled back, then the callback is cancelled.
3153          * Callbacks must not start nor commit any transactions.
3154          *
3155          * This is useful for updates that easily cause deadlocks if locks are held too long
3156          * but where atomicity is strongly desired for these updates and some related updates.
3157          *
3158          * @param callable $callback
3159          * @since 1.22
3160          */
3161         final public function onTransactionPreCommitOrIdle( $callback ) {
3162                 if ( $this->mTrxLevel ) {
3163                         $this->mTrxPreCommitCallbacks[] = array( $callback, wfGetCaller() );
3164                 } else {
3165                         $this->onTransactionIdle( $callback ); // this will trigger immediately
3166                 }
3167         }
3168
3169         /**
3170          * Actually any "on transaction idle" callbacks.
3171          *
3172          * @since 1.20
3173          */
3174         protected function runOnTransactionIdleCallbacks() {
3175                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
3176
3177                 $e = null; // last exception
3178                 do { // callbacks may add callbacks :)
3179                         $callbacks = $this->mTrxIdleCallbacks;
3180                         $this->mTrxIdleCallbacks = array(); // recursion guard
3181                         foreach ( $callbacks as $callback ) {
3182                                 try {
3183                                         list( $phpCallback ) = $callback;
3184                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
3185                                         call_user_func( $phpCallback );
3186                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3187                                 } catch ( Exception $e ) {}
3188                         }
3189                 } while ( count( $this->mTrxIdleCallbacks ) );
3190
3191                 if ( $e instanceof Exception ) {
3192                         throw $e; // re-throw any last exception
3193                 }
3194         }
3195
3196         /**
3197          * Actually any "on transaction pre-commit" callbacks.
3198          *
3199          * @since 1.22
3200          */
3201         protected function runOnTransactionPreCommitCallbacks() {
3202                 $e = null; // last exception
3203                 do { // callbacks may add callbacks :)
3204                         $callbacks = $this->mTrxPreCommitCallbacks;
3205                         $this->mTrxPreCommitCallbacks = array(); // recursion guard
3206                         foreach ( $callbacks as $callback ) {
3207                                 try {
3208                                         list( $phpCallback ) = $callback;
3209                                         call_user_func( $phpCallback );
3210                                 } catch ( Exception $e ) {}
3211                         }
3212                 } while ( count( $this->mTrxPreCommitCallbacks ) );
3213
3214                 if ( $e instanceof Exception ) {
3215                         throw $e; // re-throw any last exception
3216                 }
3217         }
3218
3219         /**
3220          * Begin an atomic section of statements
3221          *
3222          * If a transaction has been started already, just keep track of the given
3223          * section name to make sure the transaction is not committed pre-maturely.
3224          * This function can be used in layers (with sub-sections), so use a stack
3225          * to keep track of the different atomic sections. If there is no transaction,
3226          * start one implicitly.
3227          *
3228          * The goal of this function is to create an atomic section of SQL queries
3229          * without having to start a new transaction if it already exists.
3230          *
3231          * Atomic sections are more strict than transactions. With transactions,
3232          * attempting to begin a new transaction when one is already running results
3233          * in MediaWiki issuing a brief warning and doing an implicit commit. All
3234          * atomic levels *must* be explicitly closed using DatabaseBase::endAtomic(),
3235          * and any database transactions cannot be began or committed until all atomic
3236          * levels are closed. There is no such thing as implicitly opening or closing
3237          * an atomic section.
3238          *
3239          * @since 1.23
3240          * @param string $fname
3241          */
3242         final public function startAtomic( $fname = __METHOD__ ) {
3243                 if ( !$this->mTrxLevel ) {
3244                         $this->begin( $fname );
3245                         $this->mTrxAutomatic = true;
3246                         $this->mTrxAutomaticAtomic = true;
3247                 }
3248
3249                 $this->mTrxAtomicLevels->push( $fname );
3250         }
3251
3252         /**
3253          * Begin a transaction. If a transaction is already in progress, that transaction will be committed before the
3254          * new transaction is started.
3255          *
3256          * Note that when the DBO_TRX flag is set (which is usually the case for web requests, but not for maintenance scripts),
3257          * any previous database query will have started a transaction automatically.
3258          *
3259          * Nesting of transactions is not supported. Attempts to nest transactions will cause a warning, unless the current
3260          * transaction was started automatically because of the DBO_TRX flag.
3261          *
3262          * @param $fname string
3263          */
3264         final public function begin( $fname = __METHOD__ ) {
3265                 global $wgDebugDBTransactions;
3266
3267                 if ( $this->mTrxLevel ) { // implicit commit
3268                         if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3269                                 // If the current transaction was an automatic atomic one, then we definitely have
3270                                 // a problem. Same if there is any unclosed atomic level.
3271                                 throw new DBUnexpectedError( $this,
3272                                         "Attempted to start explicit transaction when atomic levels are still open."
3273                                 );
3274                         } elseif ( !$this->mTrxAutomatic ) {
3275                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3276                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3277                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3278                                         " performing implicit commit!";
3279                                 wfWarn( $msg );
3280                                 wfLogDBError( $msg );
3281                         } else {
3282                                 // if the transaction was automatic and has done write operations,
3283                                 // log it if $wgDebugDBTransactions is enabled.
3284                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3285                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3286                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3287                                         );
3288                                 }
3289                         }
3290
3291                         $this->runOnTransactionPreCommitCallbacks();
3292                         $this->doCommit( $fname );
3293                         if ( $this->mTrxDoneWrites ) {
3294                                 Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3295                         }
3296                         $this->runOnTransactionIdleCallbacks();
3297                 }
3298
3299                 $this->doBegin( $fname );
3300                 $this->mTrxFname = $fname;
3301                 $this->mTrxDoneWrites = false;
3302                 $this->mTrxAutomatic = false;
3303                 $this->mTrxAutomaticAtomic = false;
3304                 $this->mTrxAtomicLevels = new SplStack;
3305         }
3306
3307         /**
3308          * Issues the BEGIN command to the database server.
3309          *
3310          * @see DatabaseBase::begin()
3311          * @param type $fname
3312          */
3313         protected function doBegin( $fname ) {
3314                 $this->query( 'BEGIN', $fname );
3315                 $this->mTrxLevel = 1;
3316         }
3317
3318         /**
3319          * Ends an atomic section of SQL statements
3320          *
3321          * Ends the next section of atomic SQL statements and commits the transaction
3322          * if necessary.
3323          *
3324          * @since 1.23
3325          * @see DatabaseBase::startAtomic
3326          * @param string $fname
3327          */
3328         final public function endAtomic( $fname = __METHOD__ ) {
3329                 if ( $this->mTrxAtomicLevels->isEmpty() ||
3330                         $this->mTrxAtomicLevels->pop() !== $fname
3331                 ) {
3332                         throw new DBUnexpectedError( $this, 'Invalid atomic section ended.' );
3333                 }
3334
3335                 if ( $this->mTrxAtomicLevels->isEmpty() && $this->mTrxAutomaticAtomic ) {
3336                         $this->commit( $fname, 'flush' );
3337                 }
3338         }
3339
3340         /**
3341          * Commits a transaction previously started using begin().
3342          * If no transaction is in progress, a warning is issued.
3343          *
3344          * Nesting of transactions is not supported.
3345          *
3346          * @param $fname string
3347          * @param string $flush Flush flag, set to 'flush' to disable warnings about explicitly committing implicit
3348          *        transactions, or calling commit when no transaction is in progress.
3349          *        This will silently break any ongoing explicit transaction. Only set the flush flag if you are sure
3350          *        that it is safe to ignore these warnings in your context.
3351          */
3352         final public function commit( $fname = __METHOD__, $flush = '' ) {
3353                 if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3354                         // There are still atomic sections open. This cannot be ignored
3355                         throw new DBUnexpectedError( $this, "Attempted to commit transaction while atomic sections are still open" );
3356                 }
3357
3358                 if ( $flush != 'flush' ) {
3359                         if ( !$this->mTrxLevel ) {
3360                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3361                         } elseif ( $this->mTrxAutomatic ) {
3362                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3363                         }
3364                 } else {
3365                         if ( !$this->mTrxLevel ) {
3366                                 return; // nothing to do
3367                         } elseif ( !$this->mTrxAutomatic ) {
3368                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3369                         }
3370                 }
3371
3372                 $this->runOnTransactionPreCommitCallbacks();
3373                 $this->doCommit( $fname );
3374                 if ( $this->mTrxDoneWrites ) {
3375                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3376                 }
3377                 $this->mTrxDoneWrites = false;
3378                 $this->runOnTransactionIdleCallbacks();
3379         }
3380
3381         /**
3382          * Issues the COMMIT command to the database server.
3383          *
3384          * @see DatabaseBase::commit()
3385          * @param type $fname
3386          */
3387         protected function doCommit( $fname ) {
3388                 if ( $this->mTrxLevel ) {
3389                         $this->query( 'COMMIT', $fname );
3390                         $this->mTrxLevel = 0;
3391                 }
3392         }
3393
3394         /**
3395          * Rollback a transaction previously started using begin().
3396          * If no transaction is in progress, a warning is issued.
3397          *
3398          * No-op on non-transactional databases.
3399          *
3400          * @param $fname string
3401          */
3402         final public function rollback( $fname = __METHOD__ ) {
3403                 if ( !$this->mTrxLevel ) {
3404                         wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3405                 }
3406                 $this->doRollback( $fname );
3407                 $this->mTrxIdleCallbacks = array(); // cancel
3408                 $this->mTrxPreCommitCallbacks = array(); // cancel
3409                 $this->mTrxAtomicLevels = new SplStack;
3410                 if ( $this->mTrxDoneWrites ) {
3411                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3412                 }
3413                 $this->mTrxDoneWrites = false;
3414         }
3415
3416         /**
3417          * Issues the ROLLBACK command to the database server.
3418          *
3419          * @see DatabaseBase::rollback()
3420          * @param type $fname
3421          */
3422         protected function doRollback( $fname ) {
3423                 if ( $this->mTrxLevel ) {
3424                         $this->query( 'ROLLBACK', $fname, true );
3425                         $this->mTrxLevel = 0;
3426                 }
3427         }
3428
3429         /**
3430          * Creates a new table with structure copied from existing table
3431          * Note that unlike most database abstraction functions, this function does not
3432          * automatically append database prefix, because it works at a lower
3433          * abstraction level.
3434          * The table names passed to this function shall not be quoted (this
3435          * function calls addIdentifierQuotes when needed).
3436          *
3437          * @param string $oldName name of table whose structure should be copied
3438          * @param string $newName name of table to be created
3439          * @param $temporary Boolean: whether the new table should be temporary
3440          * @param string $fname calling function name
3441          * @throws MWException
3442          * @return Boolean: true if operation was successful
3443          */
3444         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3445                 $fname = __METHOD__
3446         ) {
3447                 throw new MWException(
3448                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3449         }
3450
3451         /**
3452          * List all tables on the database
3453          *
3454          * @param string $prefix Only show tables with this prefix, e.g. mw_
3455          * @param string $fname calling function name
3456          * @throws MWException
3457          */
3458         function listTables( $prefix = null, $fname = __METHOD__ ) {
3459                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3460         }
3461
3462         /**
3463          * Reset the views process cache set by listViews()
3464          * @since 1.22
3465          */
3466         final public function clearViewsCache() {
3467                 $this->allViews = null;
3468         }
3469
3470         /**
3471          * Lists all the VIEWs in the database
3472          *
3473          * For caching purposes the list of all views should be stored in
3474          * $this->allViews. The process cache can be cleared with clearViewsCache()
3475          *
3476          * @param string $prefix   Only show VIEWs with this prefix, eg. unit_test_
3477          * @param string $fname    Name of calling function
3478          * @throws MWException
3479          * @since 1.22
3480          */
3481         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3482                 throw new MWException( 'DatabaseBase::listViews is not implemented in descendant class' );
3483         }
3484
3485         /**
3486          * Differentiates between a TABLE and a VIEW
3487          *
3488          * @param $name string: Name of the database-structure to test.
3489          * @throws MWException
3490          * @since 1.22
3491          */
3492         public function isView( $name ) {
3493                 throw new MWException( 'DatabaseBase::isView is not implemented in descendant class' );
3494         }
3495
3496         /**
3497          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3498          * to the format used for inserting into timestamp fields in this DBMS.
3499          *
3500          * The result is unquoted, and needs to be passed through addQuotes()
3501          * before it can be included in raw SQL.
3502          *
3503          * @param $ts string|int
3504          *
3505          * @return string
3506          */
3507         public function timestamp( $ts = 0 ) {
3508                 return wfTimestamp( TS_MW, $ts );
3509         }
3510
3511         /**
3512          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3513          * to the format used for inserting into timestamp fields in this DBMS. If
3514          * NULL is input, it is passed through, allowing NULL values to be inserted
3515          * into timestamp fields.
3516          *
3517          * The result is unquoted, and needs to be passed through addQuotes()
3518          * before it can be included in raw SQL.
3519          *
3520          * @param $ts string|int
3521          *
3522          * @return string
3523          */
3524         public function timestampOrNull( $ts = null ) {
3525                 if ( is_null( $ts ) ) {
3526                         return null;
3527                 } else {
3528                         return $this->timestamp( $ts );
3529                 }
3530         }
3531
3532         /**
3533          * Take the result from a query, and wrap it in a ResultWrapper if
3534          * necessary. Boolean values are passed through as is, to indicate success
3535          * of write queries or failure.
3536          *
3537          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3538          * resource, and it was necessary to call this function to convert it to
3539          * a wrapper. Nowadays, raw database objects are never exposed to external
3540          * callers, so this is unnecessary in external code. For compatibility with
3541          * old code, ResultWrapper objects are passed through unaltered.
3542          *
3543          * @param $result bool|ResultWrapper
3544          *
3545          * @return bool|ResultWrapper
3546          */
3547         public function resultObject( $result ) {
3548                 if ( empty( $result ) ) {
3549                         return false;
3550                 } elseif ( $result instanceof ResultWrapper ) {
3551                         return $result;
3552                 } elseif ( $result === true ) {
3553                         // Successful write query
3554                         return $result;
3555                 } else {
3556                         return new ResultWrapper( $this, $result );
3557                 }
3558         }
3559
3560         /**
3561          * Ping the server and try to reconnect if it there is no connection
3562          *
3563          * @return bool Success or failure
3564          */
3565         public function ping() {
3566                 # Stub.  Not essential to override.
3567                 return true;
3568         }
3569
3570         /**
3571          * Get slave lag. Currently supported only by MySQL.
3572          *
3573          * Note that this function will generate a fatal error on many
3574          * installations. Most callers should use LoadBalancer::safeGetLag()
3575          * instead.
3576          *
3577          * @return int Database replication lag in seconds
3578          */
3579         public function getLag() {
3580                 return intval( $this->mFakeSlaveLag );
3581         }
3582
3583         /**
3584          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3585          *
3586          * @return int
3587          */
3588         function maxListLen() {
3589                 return 0;
3590         }
3591
3592         /**
3593          * Some DBMSs have a special format for inserting into blob fields, they
3594          * don't allow simple quoted strings to be inserted. To insert into such
3595          * a field, pass the data through this function before passing it to
3596          * DatabaseBase::insert().
3597          * @param $b string
3598          * @return string
3599          */
3600         public function encodeBlob( $b ) {
3601                 return $b;
3602         }
3603
3604         /**
3605          * Some DBMSs return a special placeholder object representing blob fields
3606          * in result objects. Pass the object through this function to return the
3607          * original string.
3608          * @param $b string
3609          * @return string
3610          */
3611         public function decodeBlob( $b ) {
3612                 return $b;
3613         }
3614
3615         /**
3616          * Override database's default behavior. $options include:
3617          *     'connTimeout' : Set the connection timeout value in seconds.
3618          *                     May be useful for very long batch queries such as
3619          *                     full-wiki dumps, where a single query reads out over
3620          *                     hours or days.
3621          *
3622          * @param $options Array
3623          * @return void
3624          */
3625         public function setSessionOptions( array $options ) {
3626         }
3627
3628         /**
3629          * Read and execute SQL commands from a file.
3630          *
3631          * Returns true on success, error string or exception on failure (depending
3632          * on object's error ignore settings).
3633          *
3634          * @param string $filename File name to open
3635          * @param bool|callable $lineCallback Optional function called before reading each line
3636          * @param bool|callable $resultCallback Optional function called for each MySQL result
3637          * @param bool|string $fname Calling function name or false if name should be
3638          *      generated dynamically using $filename
3639          * @param bool|callable $inputCallback Callback: Optional function called for each complete line sent
3640          * @throws MWException
3641          * @throws Exception|MWException
3642          * @return bool|string
3643          */
3644         public function sourceFile(
3645                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3646         ) {
3647                 wfSuppressWarnings();
3648                 $fp = fopen( $filename, 'r' );
3649                 wfRestoreWarnings();
3650
3651                 if ( false === $fp ) {
3652                         throw new MWException( "Could not open \"{$filename}\".\n" );
3653                 }
3654
3655                 if ( !$fname ) {
3656                         $fname = __METHOD__ . "( $filename )";
3657                 }
3658
3659                 try {
3660                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3661                 }
3662                 catch ( MWException $e ) {
3663                         fclose( $fp );
3664                         throw $e;
3665                 }
3666
3667                 fclose( $fp );
3668
3669                 return $error;
3670         }
3671
3672         /**
3673          * Get the full path of a patch file. Originally based on archive()
3674          * from updaters.inc. Keep in mind this always returns a patch, as
3675          * it fails back to MySQL if no DB-specific patch can be found
3676          *
3677          * @param string $patch The name of the patch, like patch-something.sql
3678          * @return String Full path to patch file
3679          */
3680         public function patchPath( $patch ) {
3681                 global $IP;
3682
3683                 $dbType = $this->getType();
3684                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3685                         return "$IP/maintenance/$dbType/archives/$patch";
3686                 } else {
3687                         return "$IP/maintenance/archives/$patch";
3688                 }
3689         }
3690
3691         /**
3692          * Set variables to be used in sourceFile/sourceStream, in preference to the
3693          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3694          * all. If it's set to false, $GLOBALS will be used.
3695          *
3696          * @param bool|array $vars mapping variable name to value.
3697          */
3698         public function setSchemaVars( $vars ) {
3699                 $this->mSchemaVars = $vars;
3700         }
3701
3702         /**
3703          * Read and execute commands from an open file handle.
3704          *
3705          * Returns true on success, error string or exception on failure (depending
3706          * on object's error ignore settings).
3707          *
3708          * @param $fp Resource: File handle
3709          * @param $lineCallback Callback: Optional function called before reading each query
3710          * @param $resultCallback Callback: Optional function called for each MySQL result
3711          * @param string $fname Calling function name
3712          * @param $inputCallback Callback: Optional function called for each complete query sent
3713          * @return bool|string
3714          */
3715         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3716                 $fname = __METHOD__, $inputCallback = false )
3717         {
3718                 $cmd = '';
3719
3720                 while ( !feof( $fp ) ) {
3721                         if ( $lineCallback ) {
3722                                 call_user_func( $lineCallback );
3723                         }
3724
3725                         $line = trim( fgets( $fp ) );
3726
3727                         if ( $line == '' ) {
3728                                 continue;
3729                         }
3730
3731                         if ( '-' == $line[0] && '-' == $line[1] ) {
3732                                 continue;
3733                         }
3734
3735                         if ( $cmd != '' ) {
3736                                 $cmd .= ' ';
3737                         }
3738
3739                         $done = $this->streamStatementEnd( $cmd, $line );
3740
3741                         $cmd .= "$line\n";
3742
3743                         if ( $done || feof( $fp ) ) {
3744                                 $cmd = $this->replaceVars( $cmd );
3745
3746                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3747                                         $res = $this->query( $cmd, $fname );
3748
3749                                         if ( $resultCallback ) {
3750                                                 call_user_func( $resultCallback, $res, $this );
3751                                         }
3752
3753                                         if ( false === $res ) {
3754                                                 $err = $this->lastError();
3755                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3756                                         }
3757                                 }
3758                                 $cmd = '';
3759                         }
3760                 }
3761
3762                 return true;
3763         }
3764
3765         /**
3766          * Called by sourceStream() to check if we've reached a statement end
3767          *
3768          * @param string $sql SQL assembled so far
3769          * @param string $newLine New line about to be added to $sql
3770          * @return Bool Whether $newLine contains end of the statement
3771          */
3772         public function streamStatementEnd( &$sql, &$newLine ) {
3773                 if ( $this->delimiter ) {
3774                         $prev = $newLine;
3775                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3776                         if ( $newLine != $prev ) {
3777                                 return true;
3778                         }
3779                 }
3780                 return false;
3781         }
3782
3783         /**
3784          * Database independent variable replacement. Replaces a set of variables
3785          * in an SQL statement with their contents as given by $this->getSchemaVars().
3786          *
3787          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3788          *
3789          * - '{$var}' should be used for text and is passed through the database's
3790          *   addQuotes method.
3791          * - `{$var}` should be used for identifiers (eg: table and database names),
3792          *   it is passed through the database's addIdentifierQuotes method which
3793          *   can be overridden if the database uses something other than backticks.
3794          * - / *$var* / is just encoded, besides traditional table prefix and
3795          *   table options its use should be avoided.
3796          *
3797          * @param string $ins SQL statement to replace variables in
3798          * @return String The new SQL statement with variables replaced
3799          */
3800         protected function replaceSchemaVars( $ins ) {
3801                 $vars = $this->getSchemaVars();
3802                 foreach ( $vars as $var => $value ) {
3803                         // replace '{$var}'
3804                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3805                         // replace `{$var}`
3806                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3807                         // replace /*$var*/
3808                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3809                 }
3810                 return $ins;
3811         }
3812
3813         /**
3814          * Replace variables in sourced SQL
3815          *
3816          * @param $ins string
3817          *
3818          * @return string
3819          */
3820         protected function replaceVars( $ins ) {
3821                 $ins = $this->replaceSchemaVars( $ins );
3822
3823                 // Table prefixes
3824                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3825                         array( $this, 'tableNameCallback' ), $ins );
3826
3827                 // Index names
3828                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3829                         array( $this, 'indexNameCallback' ), $ins );
3830
3831                 return $ins;
3832         }
3833
3834         /**
3835          * Get schema variables. If none have been set via setSchemaVars(), then
3836          * use some defaults from the current object.
3837          *
3838          * @return array
3839          */
3840         protected function getSchemaVars() {
3841                 if ( $this->mSchemaVars ) {
3842                         return $this->mSchemaVars;
3843                 } else {
3844                         return $this->getDefaultSchemaVars();
3845                 }
3846         }
3847
3848         /**
3849          * Get schema variables to use if none have been set via setSchemaVars().
3850          *
3851          * Override this in derived classes to provide variables for tables.sql
3852          * and SQL patch files.
3853          *
3854          * @return array
3855          */
3856         protected function getDefaultSchemaVars() {
3857                 return array();
3858         }
3859
3860         /**
3861          * Table name callback
3862          *
3863          * @param $matches array
3864          *
3865          * @return string
3866          */
3867         protected function tableNameCallback( $matches ) {
3868                 return $this->tableName( $matches[1] );
3869         }
3870
3871         /**
3872          * Index name callback
3873          *
3874          * @param $matches array
3875          *
3876          * @return string
3877          */
3878         protected function indexNameCallback( $matches ) {
3879                 return $this->indexName( $matches[1] );
3880         }
3881
3882         /**
3883          * Check to see if a named lock is available. This is non-blocking.
3884          *
3885          * @param string $lockName name of lock to poll
3886          * @param string $method name of method calling us
3887          * @return Boolean
3888          * @since 1.20
3889          */
3890         public function lockIsFree( $lockName, $method ) {
3891                 return true;
3892         }
3893
3894         /**
3895          * Acquire a named lock
3896          *
3897          * Abstracted from Filestore::lock() so child classes can implement for
3898          * their own needs.
3899          *
3900          * @param string $lockName name of lock to aquire
3901          * @param string $method name of method calling us
3902          * @param $timeout Integer: timeout
3903          * @return Boolean
3904          */
3905         public function lock( $lockName, $method, $timeout = 5 ) {
3906                 return true;
3907         }
3908
3909         /**
3910          * Release a lock.
3911          *
3912          * @param string $lockName Name of lock to release
3913          * @param string $method Name of method calling us
3914          *
3915          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3916          * by this thread (in which case the lock is not released), and NULL if the named
3917          * lock did not exist
3918          */
3919         public function unlock( $lockName, $method ) {
3920                 return true;
3921         }
3922
3923         /**
3924          * Lock specific tables
3925          *
3926          * @param array $read of tables to lock for read access
3927          * @param array $write of tables to lock for write access
3928          * @param string $method name of caller
3929          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
3930          *
3931          * @return bool
3932          */
3933         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3934                 return true;
3935         }
3936
3937         /**
3938          * Unlock specific tables
3939          *
3940          * @param string $method the caller
3941          *
3942          * @return bool
3943          */
3944         public function unlockTables( $method ) {
3945                 return true;
3946         }
3947
3948         /**
3949          * Delete a table
3950          * @param $tableName string
3951          * @param $fName string
3952          * @return bool|ResultWrapper
3953          * @since 1.18
3954          */
3955         public function dropTable( $tableName, $fName = __METHOD__ ) {
3956                 if ( !$this->tableExists( $tableName, $fName ) ) {
3957                         return false;
3958                 }
3959                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3960                 if ( $this->cascadingDeletes() ) {
3961                         $sql .= " CASCADE";
3962                 }
3963                 return $this->query( $sql, $fName );
3964         }
3965
3966         /**
3967          * Get search engine class. All subclasses of this need to implement this
3968          * if they wish to use searching.
3969          *
3970          * @return String
3971          */
3972         public function getSearchEngine() {
3973                 return 'SearchEngineDummy';
3974         }
3975
3976         /**
3977          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3978          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3979          * because "i" sorts after all numbers.
3980          *
3981          * @return String
3982          */
3983         public function getInfinity() {
3984                 return 'infinity';
3985         }
3986
3987         /**
3988          * Encode an expiry time into the DBMS dependent format
3989          *
3990          * @param string $expiry timestamp for expiry, or the 'infinity' string
3991          * @return String
3992          */
3993         public function encodeExpiry( $expiry ) {
3994                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3995                         ? $this->getInfinity()
3996                         : $this->timestamp( $expiry );
3997         }
3998
3999         /**
4000          * Decode an expiry time into a DBMS independent format
4001          *
4002          * @param string $expiry DB timestamp field value for expiry
4003          * @param $format integer: TS_* constant, defaults to TS_MW
4004          * @return String
4005          */
4006         public function decodeExpiry( $expiry, $format = TS_MW ) {
4007                 return ( $expiry == '' || $expiry == $this->getInfinity() )
4008                         ? 'infinity'
4009                         : wfTimestamp( $format, $expiry );
4010         }
4011
4012         /**
4013          * Allow or deny "big selects" for this session only. This is done by setting
4014          * the sql_big_selects session variable.
4015          *
4016          * This is a MySQL-specific feature.
4017          *
4018          * @param $value Mixed: true for allow, false for deny, or "default" to
4019          *   restore the initial value
4020          */
4021         public function setBigSelects( $value = true ) {
4022                 // no-op
4023         }
4024
4025         /**
4026          * @since 1.19
4027          */
4028         public function __toString() {
4029                 return (string)$this->mConn;
4030         }
4031
4032         /**
4033          * Run a few simple sanity checks
4034          */
4035         public function __destruct() {
4036                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
4037                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
4038                 }
4039                 if ( count( $this->mTrxIdleCallbacks ) || count( $this->mTrxPreCommitCallbacks ) ) {
4040                         $callers = array();
4041                         foreach ( $this->mTrxIdleCallbacks as $callbackInfo ) {
4042                                 $callers[] = $callbackInfo[1];
4043
4044                         }
4045                         $callers = implode( ', ', $callers );
4046                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
4047                 }
4048         }
4049 }