includes/db/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * This file deals with database interface functions
   6  * and query specifics/optimisations.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Database
  25  */
  26
  27 /**
  28  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  29  * following must be implemented to support MediaWiki
  30  *
  31  * @file
  32  * @ingroup Database
  33  */
  34 interface DatabaseType {
  35         /**
  36          * Get the type of the DBMS, as it appears in $wgDBtype.
  37          *
  38          * @return string
  39          */
  40         function getType();
  41
  42         /**
  43          * Open a connection to the database. Usually aborts on failure
  44          *
  45          * @param string $server database server host
  46          * @param string $user database user name
  47          * @param string $password database user password
  48          * @param string $dbName database name
  49          * @return bool
  50          * @throws DBConnectionError
  51          */
  52         function open( $server, $user, $password, $dbName );
  53
  54         /**
  55          * Fetch the next row from the given result object, in object form.
  56          * Fields can be retrieved with $row->fieldname, with fields acting like
  57          * member variables.
  58          * If no more rows are available, false is returned.
  59          *
  60          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  61          * @return object|bool
  62          * @throws DBUnexpectedError Thrown if the database returns an error
  63          */
  64         function fetchObject( $res );
  65
  66         /**
  67          * Fetch the next row from the given result object, in associative array
  68          * form.  Fields are retrieved with $row['fieldname'].
  69          * If no more rows are available, false is returned.
  70          *
  71          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  72          * @return array|bool
  73          * @throws DBUnexpectedError Thrown if the database returns an error
  74          */
  75         function fetchRow( $res );
  76
  77         /**
  78          * Get the number of rows in a result object
  79          *
  80          * @param $res Mixed: A SQL result
  81          * @return int
  82          */
  83         function numRows( $res );
  84
  85         /**
  86          * Get the number of fields in a result object
  87          * @see http://www.php.net/mysql_num_fields
  88          *
  89          * @param $res Mixed: A SQL result
  90          * @return int
  91          */
  92         function numFields( $res );
  93
  94         /**
  95          * Get a field name in a result object
  96          * @see http://www.php.net/mysql_field_name
  97          *
  98          * @param $res Mixed: A SQL result
  99          * @param $n Integer
 100          * @return string
 101          */
 102         function fieldName( $res, $n );
 103
 104         /**
 105          * Get the inserted value of an auto-increment row
 106          *
 107          * The value inserted should be fetched from nextSequenceValue()
 108          *
 109          * Example:
 110          * $id = $dbw->nextSequenceValue( 'page_page_id_seq' );
 111          * $dbw->insert( 'page', array( 'page_id' => $id ) );
 112          * $id = $dbw->insertId();
 113          *
 114          * @return int
 115          */
 116         function insertId();
 117
 118         /**
 119          * Change the position of the cursor in a result object
 120          * @see http://www.php.net/mysql_data_seek
 121          *
 122          * @param $res Mixed: A SQL result
 123          * @param $row Mixed: Either MySQL row or ResultWrapper
 124          */
 125         function dataSeek( $res, $row );
 126
 127         /**
 128          * Get the last error number
 129          * @see http://www.php.net/mysql_errno
 130          *
 131          * @return int
 132          */
 133         function lastErrno();
 134
 135         /**
 136          * Get a description of the last error
 137          * @see http://www.php.net/mysql_error
 138          *
 139          * @return string
 140          */
 141         function lastError();
 142
 143         /**
 144          * mysql_fetch_field() wrapper
 145          * Returns false if the field doesn't exist
 146          *
 147          * @param string $table table name
 148          * @param string $field field name
 149          *
 150          * @return Field
 151          */
 152         function fieldInfo( $table, $field );
 153
 154         /**
 155          * Get information about an index into an object
 156          * @param string $table Table name
 157          * @param string $index Index name
 158          * @param string $fname Calling function name
 159          * @return Mixed: Database-specific index description class or false if the index does not exist
 160          */
 161         function indexInfo( $table, $index, $fname = __METHOD__ );
 162
 163         /**
 164          * Get the number of rows affected by the last write query
 165          * @see http://www.php.net/mysql_affected_rows
 166          *
 167          * @return int
 168          */
 169         function affectedRows();
 170
 171         /**
 172          * Wrapper for addslashes()
 173          *
 174          * @param string $s to be slashed.
 175          * @return string: slashed string.
 176          */
 177         function strencode( $s );
 178
 179         /**
 180          * Returns a wikitext link to the DB's website, e.g.,
 181          *     return "[http://www.mysql.com/ MySQL]";
 182          * Should at least contain plain text, if for some reason
 183          * your database has no website.
 184          *
 185          * @return string: wikitext of a link to the server software's web site
 186          */
 187         function getSoftwareLink();
 188
 189         /**
 190          * A string describing the current software version, like from
 191          * mysql_get_server_info().
 192          *
 193          * @return string: Version information from the database server.
 194          */
 195         function getServerVersion();
 196
 197         /**
 198          * A string describing the current software version, and possibly
 199          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 200          * Use getServerVersion() to get machine-friendly information.
 201          *
 202          * @return string: Version information from the database server
 203          */
 204         function getServerInfo();
 205 }
 206
 207 /**
 208  * Interface for classes that implement or wrap DatabaseBase
 209  * @ingroup Database
 210  */
 211 interface IDatabase {}
 212
 213 /**
 214  * Database abstraction object
 215  * @ingroup Database
 216  */
 217 abstract class DatabaseBase implements IDatabase, DatabaseType {
 218         /** Number of times to re-try an operation in case of deadlock */
 219         const DEADLOCK_TRIES = 4;
 220         /** Minimum time to wait before retry, in microseconds */
 221         const DEADLOCK_DELAY_MIN = 500000;
 222         /** Maximum time to wait before retry */
 223         const DEADLOCK_DELAY_MAX = 1500000;
 224
 225 # ------------------------------------------------------------------------------
 226 # Variables
 227 # ------------------------------------------------------------------------------
 228
 229         protected $mLastQuery = '';
 230         protected $mDoneWrites = false;
 231         protected $mPHPError = false;
 232
 233         protected $mServer, $mUser, $mPassword, $mDBname;
 234
 235         protected $mConn = null;
 236         protected $mOpened = false;
 237
 238         /** @var callable[] */
 239         protected $mTrxIdleCallbacks = array();
 240         /** @var callable[] */
 241         protected $mTrxPreCommitCallbacks = array();
 242
 243         protected $mTablePrefix;
 244         protected $mFlags;
 245         protected $mForeign;
 246         protected $mTrxLevel = 0;
 247         protected $mErrorCount = 0;
 248         protected $mLBInfo = array();
 249         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 250         protected $mDefaultBigSelects = null;
 251         protected $mSchemaVars = false;
 252
 253         protected $preparedArgs;
 254
 255         protected $htmlErrors;
 256
 257         protected $delimiter = ';';
 258
 259         /**
 260          * Remembers the function name given for starting the most recent transaction via begin().
 261          * Used to provide additional context for error reporting.
 262          *
 263          * @var String
 264          * @see DatabaseBase::mTrxLevel
 265          */
 266         private $mTrxFname = null;
 267
 268         /**
 269          * Record if possible write queries were done in the last transaction started
 270          *
 271          * @var Bool
 272          * @see DatabaseBase::mTrxLevel
 273          */
 274         private $mTrxDoneWrites = false;
 275
 276         /**
 277          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 278          *
 279          * @var Bool
 280          * @see DatabaseBase::mTrxLevel
 281          */
 282         private $mTrxAutomatic = false;
 283
 284         /**
 285          * Array of levels of atomicity within transactions
 286          *
 287          * @var SplStack
 288          */
 289         private $mTrxAtomicLevels;
 290
 291         /**
 292          * Record if the current transaction was started implicitly by DatabaseBase::startAtomic
 293          *
 294          * @var Bool
 295          */
 296         private $mTrxAutomaticAtomic = false;
 297
 298         /**
 299          * @since 1.21
 300          * @var file handle for upgrade
 301          */
 302         protected $fileHandle = null;
 303
 304 # ------------------------------------------------------------------------------
 305 # Accessors
 306 # ------------------------------------------------------------------------------
 307         # These optionally set a variable and return the previous state
 308
 309         /**
 310          * A string describing the current software version, and possibly
 311          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 312          * Use getServerVersion() to get machine-friendly information.
 313          *
 314          * @return string: Version information from the database server
 315          */
 316         public function getServerInfo() {
 317                 return $this->getServerVersion();
 318         }
 319
 320         /**
 321          * @return string: command delimiter used by this database engine
 322          */
 323         public function getDelimiter() {
 324                 return $this->delimiter;
 325         }
 326
 327         /**
 328          * Boolean, controls output of large amounts of debug information.
 329          * @param $debug bool|null
 330          *   - true to enable debugging
 331          *   - false to disable debugging
 332          *   - omitted or null to do nothing
 333          *
 334          * @return bool|null previous value of the flag
 335          */
 336         public function debug( $debug = null ) {
 337                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 338         }
 339
 340         /**
 341          * Turns buffering of SQL result sets on (true) or off (false). Default is
 342          * "on".
 343          *
 344          * Unbuffered queries are very troublesome in MySQL:
 345          *
 346          *   - If another query is executed while the first query is being read
 347          *     out, the first query is killed. This means you can't call normal
 348          *     MediaWiki functions while you are reading an unbuffered query result
 349          *     from a normal wfGetDB() connection.
 350          *
 351          *   - Unbuffered queries cause the MySQL server to use large amounts of
 352          *     memory and to hold broad locks which block other queries.
 353          *
 354          * If you want to limit client-side memory, it's almost always better to
 355          * split up queries into batches using a LIMIT clause than to switch off
 356          * buffering.
 357          *
 358          * @param $buffer null|bool
 359          *
 360          * @return null|bool The previous value of the flag
 361          */
 362         public function bufferResults( $buffer = null ) {
 363                 if ( is_null( $buffer ) ) {
 364                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 365                 } else {
 366                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 367                 }
 368         }
 369
 370         /**
 371          * Turns on (false) or off (true) the automatic generation and sending
 372          * of a "we're sorry, but there has been a database error" page on
 373          * database errors. Default is on (false). When turned off, the
 374          * code should use lastErrno() and lastError() to handle the
 375          * situation as appropriate.
 376          *
 377          * Do not use this function outside of the Database classes.
 378          *
 379          * @param $ignoreErrors bool|null
 380          *
 381          * @return bool The previous value of the flag.
 382          */
 383         public function ignoreErrors( $ignoreErrors = null ) {
 384                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 385         }
 386
 387         /**
 388          * Gets or sets the current transaction level.
 389          *
 390          * Historically, transactions were allowed to be "nested". This is no
 391          * longer supported, so this function really only returns a boolean.
 392          *
 393          * @param int $level An integer (0 or 1), or omitted to leave it unchanged.
 394          * @return int The previous value
 395          */
 396         public function trxLevel( $level = null ) {
 397                 return wfSetVar( $this->mTrxLevel, $level );
 398         }
 399
 400         /**
 401          * Get/set the number of errors logged. Only useful when errors are ignored
 402          * @param int $count The count to set, or omitted to leave it unchanged.
 403          * @return int The error count
 404          */
 405         public function errorCount( $count = null ) {
 406                 return wfSetVar( $this->mErrorCount, $count );
 407         }
 408
 409         /**
 410          * Get/set the table prefix.
 411          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 412          * @return string The previous table prefix.
 413          */
 414         public function tablePrefix( $prefix = null ) {
 415                 return wfSetVar( $this->mTablePrefix, $prefix );
 416         }
 417
 418         /**
 419          * Set the filehandle to copy write statements to.
 420          *
 421          * @param $fh filehandle
 422          */
 423         public function setFileHandle( $fh ) {
 424                 $this->fileHandle = $fh;
 425         }
 426
 427         /**
 428          * Get properties passed down from the server info array of the load
 429          * balancer.
 430          *
 431          * @param string $name The entry of the info array to get, or null to get the
 432          *   whole array
 433          *
 434          * @return LoadBalancer|null
 435          */
 436         public function getLBInfo( $name = null ) {
 437                 if ( is_null( $name ) ) {
 438                         return $this->mLBInfo;
 439                 } else {
 440                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 441                                 return $this->mLBInfo[$name];
 442                         } else {
 443                                 return null;
 444                         }
 445                 }
 446         }
 447
 448         /**
 449          * Set the LB info array, or a member of it. If called with one parameter,
 450          * the LB info array is set to that parameter. If it is called with two
 451          * parameters, the member with the given name is set to the given value.
 452          *
 453          * @param $name
 454          * @param $value
 455          */
 456         public function setLBInfo( $name, $value = null ) {
 457                 if ( is_null( $value ) ) {
 458                         $this->mLBInfo = $name;
 459                 } else {
 460                         $this->mLBInfo[$name] = $value;
 461                 }
 462         }
 463
 464         /**
 465          * Set lag time in seconds for a fake slave
 466          *
 467          * @param $lag int
 468          */
 469         public function setFakeSlaveLag( $lag ) {
 470                 $this->mFakeSlaveLag = $lag;
 471         }
 472
 473         /**
 474          * Make this connection a fake master
 475          *
 476          * @param $enabled bool
 477          */
 478         public function setFakeMaster( $enabled = true ) {
 479                 $this->mFakeMaster = $enabled;
 480         }
 481
 482         /**
 483          * Returns true if this database supports (and uses) cascading deletes
 484          *
 485          * @return bool
 486          */
 487         public function cascadingDeletes() {
 488                 return false;
 489         }
 490
 491         /**
 492          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 493          *
 494          * @return bool
 495          */
 496         public function cleanupTriggers() {
 497                 return false;
 498         }
 499
 500         /**
 501          * Returns true if this database is strict about what can be put into an IP field.
 502          * Specifically, it uses a NULL value instead of an empty string.
 503          *
 504          * @return bool
 505          */
 506         public function strictIPs() {
 507                 return false;
 508         }
 509
 510         /**
 511          * Returns true if this database uses timestamps rather than integers
 512          *
 513          * @return bool
 514          */
 515         public function realTimestamps() {
 516                 return false;
 517         }
 518
 519         /**
 520          * Returns true if this database does an implicit sort when doing GROUP BY
 521          *
 522          * @return bool
 523          */
 524         public function implicitGroupby() {
 525                 return true;
 526         }
 527
 528         /**
 529          * Returns true if this database does an implicit order by when the column has an index
 530          * For example: SELECT page_title FROM page LIMIT 1
 531          *
 532          * @return bool
 533          */
 534         public function implicitOrderby() {
 535                 return true;
 536         }
 537
 538         /**
 539          * Returns true if this database can do a native search on IP columns
 540          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 541          *
 542          * @return bool
 543          */
 544         public function searchableIPs() {
 545                 return false;
 546         }
 547
 548         /**
 549          * Returns true if this database can use functional indexes
 550          *
 551          * @return bool
 552          */
 553         public function functionalIndexes() {
 554                 return false;
 555         }
 556
 557         /**
 558          * Return the last query that went through DatabaseBase::query()
 559          * @return String
 560          */
 561         public function lastQuery() {
 562                 return $this->mLastQuery;
 563         }
 564
 565         /**
 566          * Returns true if the connection may have been used for write queries.
 567          * Should return true if unsure.
 568          *
 569          * @return bool
 570          */
 571         public function doneWrites() {
 572                 return $this->mDoneWrites;
 573         }
 574
 575         /**
 576          * Returns true if there is a transaction open with possible write
 577          * queries or transaction pre-commit/idle callbacks waiting on it to finish.
 578          *
 579          * @return bool
 580          */
 581         public function writesOrCallbacksPending() {
 582                 return $this->mTrxLevel && (
 583                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 584                 );
 585         }
 586
 587         /**
 588          * Is a connection to the database open?
 589          * @return Boolean
 590          */
 591         public function isOpen() {
 592                 return $this->mOpened;
 593         }
 594
 595         /**
 596          * Set a flag for this connection
 597          *
 598          * @param $flag Integer: DBO_* constants from Defines.php:
 599          *   - DBO_DEBUG: output some debug info (same as debug())
 600          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 601          *   - DBO_TRX: automatically start transactions
 602          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 603          *       and removes it in command line mode
 604          *   - DBO_PERSISTENT: use persistant database connection
 605          */
 606         public function setFlag( $flag ) {
 607                 global $wgDebugDBTransactions;
 608                 $this->mFlags |= $flag;
 609                 if ( ( $flag & DBO_TRX ) & $wgDebugDBTransactions ) {
 610                         wfDebug( "Implicit transactions are now  disabled.\n" );
 611                 }
 612         }
 613
 614         /**
 615          * Clear a flag for this connection
 616          *
 617          * @param $flag: same as setFlag()'s $flag param
 618          */
 619         public function clearFlag( $flag ) {
 620                 global $wgDebugDBTransactions;
 621                 $this->mFlags &= ~$flag;
 622                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 623                         wfDebug( "Implicit transactions are now disabled.\n" );
 624                 }
 625         }
 626
 627         /**
 628          * Returns a boolean whether the flag $flag is set for this connection
 629          *
 630          * @param $flag: same as setFlag()'s $flag param
 631          * @return Boolean
 632          */
 633         public function getFlag( $flag ) {
 634                 return !!( $this->mFlags & $flag );
 635         }
 636
 637         /**
 638          * General read-only accessor
 639          *
 640          * @param $name string
 641          *
 642          * @return string
 643          */
 644         public function getProperty( $name ) {
 645                 return $this->$name;
 646         }
 647
 648         /**
 649          * @return string
 650          */
 651         public function getWikiID() {
 652                 if ( $this->mTablePrefix ) {
 653                         return "{$this->mDBname}-{$this->mTablePrefix}";
 654                 } else {
 655                         return $this->mDBname;
 656                 }
 657         }
 658
 659         /**
 660          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 661          *
 662          * @return string
 663          */
 664         public function getSchemaPath() {
 665                 global $IP;
 666                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 667                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 668                 } else {
 669                         return "$IP/maintenance/tables.sql";
 670                 }
 671         }
 672
 673 # ------------------------------------------------------------------------------
 674 # Other functions
 675 # ------------------------------------------------------------------------------
 676
 677         /**
 678          * Constructor.
 679          *
 680          * FIXME: It is possible to construct a Database object with no associated
 681          * connection object, by specifying no parameters to __construct(). This
 682          * feature is deprecated and should be removed.
 683          *
 684          * DatabaseBase subclasses should not be constructed directly in external
 685          * code. DatabaseBase::factory() should be used instead.
 686          *
 687          * @param array Parameters passed from DatabaseBase::factory()
 688          */
 689         function __construct( $params = null ) {
 690                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 691
 692                 $this->mTrxAtomicLevels = new SplStack;
 693
 694                 if ( is_array( $params ) ) { // MW 1.22
 695                         $server = $params['host'];
 696                         $user = $params['user'];
 697                         $password = $params['password'];
 698                         $dbName = $params['dbname'];
 699                         $flags = $params['flags'];
 700                         $tablePrefix = $params['tablePrefix'];
 701                         $foreign = $params['foreign'];
 702                 } else { // legacy calling pattern
 703                         wfDeprecated( __METHOD__ . " method called without parameter array.", "1.22" );
 704                         $args = func_get_args();
 705                         $server = isset( $args[0] ) ? $args[0] : false;
 706                         $user = isset( $args[1] ) ? $args[1] : false;
 707                         $password = isset( $args[2] ) ? $args[2] : false;
 708                         $dbName = isset( $args[3] ) ? $args[3] : false;
 709                         $flags = isset( $args[4] ) ? $args[4] : 0;
 710                         $tablePrefix = isset( $args[5] ) ? $args[5] : 'get from global';
 711                         $foreign = isset( $args[6] ) ? $args[6] : false;
 712                 }
 713
 714                 $this->mFlags = $flags;
 715                 if ( $this->mFlags & DBO_DEFAULT ) {
 716                         if ( $wgCommandLineMode ) {
 717                                 $this->mFlags &= ~DBO_TRX;
 718                                 if ( $wgDebugDBTransactions ) {
 719                                         wfDebug( "Implicit transaction open disabled.\n" );
 720                                 }
 721                         } else {
 722                                 $this->mFlags |= DBO_TRX;
 723                                 if ( $wgDebugDBTransactions ) {
 724                                         wfDebug( "Implicit transaction open enabled.\n" );
 725                                 }
 726                         }
 727                 }
 728
 729                 /** Get the default table prefix*/
 730                 if ( $tablePrefix == 'get from global' ) {
 731                         $this->mTablePrefix = $wgDBprefix;
 732                 } else {
 733                         $this->mTablePrefix = $tablePrefix;
 734                 }
 735
 736                 $this->mForeign = $foreign;
 737
 738                 if ( $user ) {
 739                         $this->open( $server, $user, $password, $dbName );
 740                 }
 741         }
 742
 743         /**
 744          * Called by serialize. Throw an exception when DB connection is serialized.
 745          * This causes problems on some database engines because the connection is
 746          * not restored on unserialize.
 747          */
 748         public function __sleep() {
 749                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 750         }
 751
 752         /**
 753          * Given a DB type, construct the name of the appropriate child class of
 754          * DatabaseBase. This is designed to replace all of the manual stuff like:
 755          *      $class = 'Database' . ucfirst( strtolower( $dbType ) );
 756          * as well as validate against the canonical list of DB types we have
 757          *
 758          * This factory function is mostly useful for when you need to connect to a
 759          * database other than the MediaWiki default (such as for external auth,
 760          * an extension, et cetera). Do not use this to connect to the MediaWiki
 761          * database. Example uses in core:
 762          * @see LoadBalancer::reallyOpenConnection()
 763          * @see ForeignDBRepo::getMasterDB()
 764          * @see WebInstaller_DBConnect::execute()
 765          *
 766          * @since 1.18
 767          *
 768          * @param string $dbType A possible DB type
 769          * @param array $p An array of options to pass to the constructor.
 770          *    Valid options are: host, user, password, dbname, flags, tablePrefix, driver
 771          * @return DatabaseBase subclass or null
 772          */
 773         final public static function factory( $dbType, $p = array() ) {
 774                 $canonicalDBTypes = array(
 775                         'mysql'    => array( 'mysqli', 'mysql' ),
 776                         'postgres' => array(),
 777                         'sqlite'   => array(),
 778                         'oracle'   => array(),
 779                         'mssql'    => array(),
 780                 );
 781
 782                 $driver = false;
 783                 $dbType = strtolower( $dbType );
 784                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 785                         $possibleDrivers = $canonicalDBTypes[$dbType];
 786                         if ( !empty( $p['driver'] ) ) {
 787                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 788                                         $driver = $p['driver'];
 789                                 } else {
 790                                         throw new MWException( __METHOD__ .
 791                                                 " cannot construct Database with type '$dbType' and driver '{$p['driver']}'" );
 792                                 }
 793                         } else {
 794                                 foreach ( $possibleDrivers as $posDriver ) {
 795                                         if ( extension_loaded( $posDriver ) ) {
 796                                                 $driver = $posDriver;
 797                                                 break;
 798                                         }
 799                                 }
 800                         }
 801                 } else {
 802                         $driver = $dbType;
 803                 }
 804                 if ( $driver === false ) {
 805                         throw new MWException( __METHOD__ .
 806                                 " no viable database extension found for type '$dbType'" );
 807                 }
 808
 809                 $class = 'Database' . ucfirst( $driver );
 810                 if ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 811                         $params = array(
 812                                 'host' => isset( $p['host'] ) ? $p['host'] : false,
 813                                 'user' => isset( $p['user'] ) ? $p['user'] : false,
 814                                 'password' => isset( $p['password'] ) ? $p['password'] : false,
 815                                 'dbname' => isset( $p['dbname'] ) ? $p['dbname'] : false,
 816                                 'flags' => isset( $p['flags'] ) ? $p['flags'] : 0,
 817                                 'tablePrefix' => isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global',
 818                                 'foreign' => isset( $p['foreign'] ) ? $p['foreign'] : false
 819                         );
 820                         return new $class( $params );
 821                 } else {
 822                         return null;
 823                 }
 824         }
 825
 826         protected function installErrorHandler() {
 827                 $this->mPHPError = false;
 828                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 829                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 830         }
 831
 832         /**
 833          * @return bool|string
 834          */
 835         protected function restoreErrorHandler() {
 836                 restore_error_handler();
 837                 if ( $this->htmlErrors !== false ) {
 838                         ini_set( 'html_errors', $this->htmlErrors );
 839                 }
 840                 if ( $this->mPHPError ) {
 841                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 842                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 843                         return $error;
 844                 } else {
 845                         return false;
 846                 }
 847         }
 848
 849         /**
 850          * @param $errno
 851          * @param $errstr
 852          * @access private
 853          */
 854         public function connectionErrorHandler( $errno, $errstr ) {
 855                 $this->mPHPError = $errstr;
 856         }
 857
 858         /**
 859          * Closes a database connection.
 860          * if it is open : commits any open transactions
 861          *
 862          * @throws MWException
 863          * @return Bool operation success. true if already closed.
 864          */
 865         public function close() {
 866                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 867                         throw new MWException( "Transaction idle callbacks still pending." );
 868                 }
 869                 $this->mOpened = false;
 870                 if ( $this->mConn ) {
 871                         if ( $this->trxLevel() ) {
 872                                 if ( !$this->mTrxAutomatic ) {
 873                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 874                                                 " performing implicit commit before closing connection!" );
 875                                 }
 876
 877                                 $this->commit( __METHOD__, 'flush' );
 878                         }
 879
 880                         $ret = $this->closeConnection();
 881                         $this->mConn = false;
 882                         return $ret;
 883                 } else {
 884                         return true;
 885                 }
 886         }
 887
 888         /**
 889          * Closes underlying database connection
 890          * @since 1.20
 891          * @return bool: Whether connection was closed successfully
 892          */
 893         abstract protected function closeConnection();
 894
 895         /**
 896          * @param string $error fallback error message, used if none is given by DB
 897          * @throws DBConnectionError
 898          */
 899         function reportConnectionError( $error = 'Unknown error' ) {
 900                 $myError = $this->lastError();
 901                 if ( $myError ) {
 902                         $error = $myError;
 903                 }
 904
 905                 # New method
 906                 throw new DBConnectionError( $this, $error );
 907         }
 908
 909         /**
 910          * The DBMS-dependent part of query()
 911          *
 912          * @param  $sql String: SQL query.
 913          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 914          */
 915         abstract protected function doQuery( $sql );
 916
 917         /**
 918          * Determine whether a query writes to the DB.
 919          * Should return true if unsure.
 920          *
 921          * @param $sql string
 922          *
 923          * @return bool
 924          */
 925         public function isWriteQuery( $sql ) {
 926                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 927         }
 928
 929         /**
 930          * Run an SQL query and return the result. Normally throws a DBQueryError
 931          * on failure. If errors are ignored, returns false instead.
 932          *
 933          * In new code, the query wrappers select(), insert(), update(), delete(),
 934          * etc. should be used where possible, since they give much better DBMS
 935          * independence and automatically quote or validate user input in a variety
 936          * of contexts. This function is generally only useful for queries which are
 937          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 938          * as CREATE TABLE.
 939          *
 940          * However, the query wrappers themselves should call this function.
 941          *
 942          * @param  $sql        String: SQL query
 943          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 944          *     comment (you can use __METHOD__ or add some extra info)
 945          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 946          *     maybe best to catch the exception instead?
 947          * @throws MWException
 948          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 949          *     for a successful read query, or false on failure if $tempIgnore set
 950          */
 951         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 952                 global $wgUser, $wgDebugDBTransactions;
 953
 954                 $this->mLastQuery = $sql;
 955                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 956                         # Set a flag indicating that writes have been done
 957                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 958                         $this->mDoneWrites = true;
 959                 }
 960
 961                 # Add a comment for easy SHOW PROCESSLIST interpretation
 962                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 963                         $userName = $wgUser->getName();
 964                         if ( mb_strlen( $userName ) > 15 ) {
 965                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 966                         }
 967                         $userName = str_replace( '/', '', $userName );
 968                 } else {
 969                         $userName = '';
 970                 }
 971
 972                 // Add trace comment to the begin of the sql string, right after the operator.
 973                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 974                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 975
 976                 # If DBO_TRX is set, start a transaction
 977                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 978                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' )
 979                 {
 980                         # Avoid establishing transactions for SHOW and SET statements too -
 981                         # that would delay transaction initializations to once connection
 982                         # is really used by application
 983                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 984                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 985                                 if ( $wgDebugDBTransactions ) {
 986                                         wfDebug( "Implicit transaction start.\n" );
 987                                 }
 988                                 $this->begin( __METHOD__ . " ($fname)" );
 989                                 $this->mTrxAutomatic = true;
 990                         }
 991                 }
 992
 993                 # Keep track of whether the transaction has write queries pending
 994                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
 995                         $this->mTrxDoneWrites = true;
 996                         Profiler::instance()->transactionWritingIn( $this->mServer, $this->mDBname );
 997                 }
 998
 999                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1000                 if ( !Profiler::instance()->isStub() ) {
1001                         # generalizeSQL will probably cut down the query to reasonable
1002                         # logging size most of the time. The substr is really just a sanity check.
1003                         if ( $isMaster ) {
1004                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
1005                                 $totalProf = 'DatabaseBase::query-master';
1006                         } else {
1007                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
1008                                 $totalProf = 'DatabaseBase::query';
1009                         }
1010                         wfProfileIn( $totalProf );
1011                         wfProfileIn( $queryProf );
1012                 }
1013
1014                 if ( $this->debug() ) {
1015                         static $cnt = 0;
1016
1017                         $cnt++;
1018                         $sqlx = substr( $commentedSql, 0, 500 );
1019                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
1020
1021                         $master = $isMaster ? 'master' : 'slave';
1022                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
1023                 }
1024
1025                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
1026
1027                 # Do the query and handle errors
1028                 $ret = $this->doQuery( $commentedSql );
1029
1030                 MWDebug::queryTime( $queryId );
1031
1032                 # Try reconnecting if the connection was lost
1033                 if ( false === $ret && $this->wasErrorReissuable() ) {
1034                         # Transaction is gone, like it or not
1035                         $this->mTrxLevel = 0;
1036                         $this->mTrxIdleCallbacks = array(); // cancel
1037                         $this->mTrxPreCommitCallbacks = array(); // cancel
1038                         wfDebug( "Connection lost, reconnecting...\n" );
1039
1040                         if ( $this->ping() ) {
1041                                 wfDebug( "Reconnected\n" );
1042                                 $sqlx = substr( $commentedSql, 0, 500 );
1043                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
1044                                 global $wgRequestTime;
1045                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
1046                                 if ( $elapsed < 300 ) {
1047                                         # Not a database error to lose a transaction after a minute or two
1048                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
1049                                 }
1050                                 $ret = $this->doQuery( $commentedSql );
1051                         } else {
1052                                 wfDebug( "Failed\n" );
1053                         }
1054                 }
1055
1056                 if ( false === $ret ) {
1057                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1058                 }
1059
1060                 if ( !Profiler::instance()->isStub() ) {
1061                         wfProfileOut( $queryProf );
1062                         wfProfileOut( $totalProf );
1063                 }
1064
1065                 return $this->resultObject( $ret );
1066         }
1067
1068         /**
1069          * Report a query error. Log the error, and if neither the object ignore
1070          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1071          *
1072          * @param $error String
1073          * @param $errno Integer
1074          * @param $sql String
1075          * @param $fname String
1076          * @param $tempIgnore Boolean
1077          * @throws DBQueryError
1078          */
1079         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1080                 # Ignore errors during error handling to avoid infinite recursion
1081                 $ignore = $this->ignoreErrors( true );
1082                 ++$this->mErrorCount;
1083
1084                 if ( $ignore || $tempIgnore ) {
1085                         wfDebug( "SQL ERROR (ignored): $error\n" );
1086                         $this->ignoreErrors( $ignore );
1087                 } else {
1088                         $sql1line = str_replace( "\n", "\\n", $sql );
1089                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
1090                         wfDebug( "SQL ERROR: " . $error . "\n" );
1091                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1092                 }
1093         }
1094
1095         /**
1096          * Intended to be compatible with the PEAR::DB wrapper functions.
1097          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1098          *
1099          * ? = scalar value, quoted as necessary
1100          * ! = raw SQL bit (a function for instance)
1101          * & = filename; reads the file and inserts as a blob
1102          *     (we don't use this though...)
1103          *
1104          * @param $sql string
1105          * @param $func string
1106          *
1107          * @return array
1108          */
1109         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1110                 /* MySQL doesn't support prepared statements (yet), so just
1111                    pack up the query for reference. We'll manually replace
1112                    the bits later. */
1113                 return array( 'query' => $sql, 'func' => $func );
1114         }
1115
1116         /**
1117          * Free a prepared query, generated by prepare().
1118          * @param $prepared
1119          */
1120         protected function freePrepared( $prepared ) {
1121                 /* No-op by default */
1122         }
1123
1124         /**
1125          * Execute a prepared query with the various arguments
1126          * @param string $prepared the prepared sql
1127          * @param $args Mixed: Either an array here, or put scalars as varargs
1128          *
1129          * @return ResultWrapper
1130          */
1131         public function execute( $prepared, $args = null ) {
1132                 if ( !is_array( $args ) ) {
1133                         # Pull the var args
1134                         $args = func_get_args();
1135                         array_shift( $args );
1136                 }
1137
1138                 $sql = $this->fillPrepared( $prepared['query'], $args );
1139
1140                 return $this->query( $sql, $prepared['func'] );
1141         }
1142
1143         /**
1144          * For faking prepared SQL statements on DBs that don't support it directly.
1145          *
1146          * @param string $preparedQuery a 'preparable' SQL statement
1147          * @param array $args of arguments to fill it with
1148          * @return string executable SQL
1149          */
1150         public function fillPrepared( $preparedQuery, $args ) {
1151                 reset( $args );
1152                 $this->preparedArgs =& $args;
1153
1154                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1155                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1156         }
1157
1158         /**
1159          * preg_callback func for fillPrepared()
1160          * The arguments should be in $this->preparedArgs and must not be touched
1161          * while we're doing this.
1162          *
1163          * @param $matches Array
1164          * @throws DBUnexpectedError
1165          * @return String
1166          */
1167         protected function fillPreparedArg( $matches ) {
1168                 switch ( $matches[1] ) {
1169                         case '\\?':
1170                                 return '?';
1171                         case '\\!':
1172                                 return '!';
1173                         case '\\&':
1174                                 return '&';
1175                 }
1176
1177                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1178
1179                 switch ( $matches[1] ) {
1180                         case '?':
1181                                 return $this->addQuotes( $arg );
1182                         case '!':
1183                                 return $arg;
1184                         case '&':
1185                                 # return $this->addQuotes( file_get_contents( $arg ) );
1186                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1187                         default:
1188                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1189                 }
1190         }
1191
1192         /**
1193          * Free a result object returned by query() or select(). It's usually not
1194          * necessary to call this, just use unset() or let the variable holding
1195          * the result object go out of scope.
1196          *
1197          * @param $res Mixed: A SQL result
1198          */
1199         public function freeResult( $res ) {
1200         }
1201
1202         /**
1203          * A SELECT wrapper which returns a single field from a single result row.
1204          *
1205          * Usually throws a DBQueryError on failure. If errors are explicitly
1206          * ignored, returns false on failure.
1207          *
1208          * If no result rows are returned from the query, false is returned.
1209          *
1210          * @param string|array $table Table name. See DatabaseBase::select() for details.
1211          * @param string $var The field name to select. This must be a valid SQL
1212          *   fragment: do not use unvalidated user input.
1213          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1214          * @param string $fname The function name of the caller.
1215          * @param string|array $options The query options. See DatabaseBase::select() for details.
1216          *
1217          * @return bool|mixed The value from the field, or false on failure.
1218          */
1219         public function selectField( $table, $var, $cond = '', $fname = __METHOD__,
1220                 $options = array()
1221         ) {
1222                 if ( !is_array( $options ) ) {
1223                         $options = array( $options );
1224                 }
1225
1226                 $options['LIMIT'] = 1;
1227
1228                 $res = $this->select( $table, $var, $cond, $fname, $options );
1229
1230                 if ( $res === false || !$this->numRows( $res ) ) {
1231                         return false;
1232                 }
1233
1234                 $row = $this->fetchRow( $res );
1235
1236                 if ( $row !== false ) {
1237                         return reset( $row );
1238                 } else {
1239                         return false;
1240                 }
1241         }
1242
1243         /**
1244          * Returns an optional USE INDEX clause to go after the table, and a
1245          * string to go at the end of the query.
1246          *
1247          * @param array $options associative array of options to be turned into
1248          *              an SQL query, valid keys are listed in the function.
1249          * @return Array
1250          * @see DatabaseBase::select()
1251          */
1252         public function makeSelectOptions( $options ) {
1253                 $preLimitTail = $postLimitTail = '';
1254                 $startOpts = '';
1255
1256                 $noKeyOptions = array();
1257
1258                 foreach ( $options as $key => $option ) {
1259                         if ( is_numeric( $key ) ) {
1260                                 $noKeyOptions[$option] = true;
1261                         }
1262                 }
1263
1264                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1265
1266                 $preLimitTail .= $this->makeOrderBy( $options );
1267
1268                 // if (isset($options['LIMIT'])) {
1269                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1270                 //              isset($options['OFFSET']) ? $options['OFFSET']
1271                 //              : false);
1272                 // }
1273
1274                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1275                         $postLimitTail .= ' FOR UPDATE';
1276                 }
1277
1278                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1279                         $postLimitTail .= ' LOCK IN SHARE MODE';
1280                 }
1281
1282                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1283                         $startOpts .= 'DISTINCT';
1284                 }
1285
1286                 # Various MySQL extensions
1287                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1288                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1289                 }
1290
1291                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1292                         $startOpts .= ' HIGH_PRIORITY';
1293                 }
1294
1295                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1296                         $startOpts .= ' SQL_BIG_RESULT';
1297                 }
1298
1299                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1300                         $startOpts .= ' SQL_BUFFER_RESULT';
1301                 }
1302
1303                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1304                         $startOpts .= ' SQL_SMALL_RESULT';
1305                 }
1306
1307                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1308                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1309                 }
1310
1311                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1312                         $startOpts .= ' SQL_CACHE';
1313                 }
1314
1315                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1316                         $startOpts .= ' SQL_NO_CACHE';
1317                 }
1318
1319                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1320                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1321                 } else {
1322                         $useIndex = '';
1323                 }
1324
1325                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1326         }
1327
1328         /**
1329          * Returns an optional GROUP BY with an optional HAVING
1330          *
1331          * @param array $options associative array of options
1332          * @return string
1333          * @see DatabaseBase::select()
1334          * @since 1.21
1335          */
1336         public function makeGroupByWithHaving( $options ) {
1337                 $sql = '';
1338                 if ( isset( $options['GROUP BY'] ) ) {
1339                         $gb = is_array( $options['GROUP BY'] )
1340                                 ? implode( ',', $options['GROUP BY'] )
1341                                 : $options['GROUP BY'];
1342                         $sql .= ' GROUP BY ' . $gb;
1343                 }
1344                 if ( isset( $options['HAVING'] ) ) {
1345                         $having = is_array( $options['HAVING'] )
1346                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1347                                 : $options['HAVING'];
1348                         $sql .= ' HAVING ' . $having;
1349                 }
1350                 return $sql;
1351         }
1352
1353         /**
1354          * Returns an optional ORDER BY
1355          *
1356          * @param array $options associative array of options
1357          * @return string
1358          * @see DatabaseBase::select()
1359          * @since 1.21
1360          */
1361         public function makeOrderBy( $options ) {
1362                 if ( isset( $options['ORDER BY'] ) ) {
1363                         $ob = is_array( $options['ORDER BY'] )
1364                                 ? implode( ',', $options['ORDER BY'] )
1365                                 : $options['ORDER BY'];
1366                         return ' ORDER BY ' . $ob;
1367                 }
1368                 return '';
1369         }
1370
1371         /**
1372          * Execute a SELECT query constructed using the various parameters provided.
1373          * See below for full details of the parameters.
1374          *
1375          * @param string|array $table Table name
1376          * @param string|array $vars Field names
1377          * @param string|array $conds Conditions
1378          * @param string $fname Caller function name
1379          * @param array $options Query options
1380          * @param $join_conds Array Join conditions
1381          *
1382          * @param $table string|array
1383          *
1384          * May be either an array of table names, or a single string holding a table
1385          * name. If an array is given, table aliases can be specified, for example:
1386          *
1387          *    array( 'a' => 'user' )
1388          *
1389          * This includes the user table in the query, with the alias "a" available
1390          * for use in field names (e.g. a.user_name).
1391          *
1392          * All of the table names given here are automatically run through
1393          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1394          * added, and various other table name mappings to be performed.
1395          *
1396          *
1397          * @param $vars string|array
1398          *
1399          * May be either a field name or an array of field names. The field names
1400          * can be complete fragments of SQL, for direct inclusion into the SELECT
1401          * query. If an array is given, field aliases can be specified, for example:
1402          *
1403          *   array( 'maxrev' => 'MAX(rev_id)' )
1404          *
1405          * This includes an expression with the alias "maxrev" in the query.
1406          *
1407          * If an expression is given, care must be taken to ensure that it is
1408          * DBMS-independent.
1409          *
1410          *
1411          * @param $conds string|array
1412          *
1413          * May be either a string containing a single condition, or an array of
1414          * conditions. If an array is given, the conditions constructed from each
1415          * element are combined with AND.
1416          *
1417          * Array elements may take one of two forms:
1418          *
1419          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1420          *   - Elements with a string key are interpreted as equality conditions,
1421          *     where the key is the field name.
1422          *     - If the value of such an array element is a scalar (such as a
1423          *       string), it will be treated as data and thus quoted appropriately.
1424          *       If it is null, an IS NULL clause will be added.
1425          *     - If the value is an array, an IN(...) clause will be constructed,
1426          *       such that the field name may match any of the elements in the
1427          *       array. The elements of the array will be quoted.
1428          *
1429          * Note that expressions are often DBMS-dependent in their syntax.
1430          * DBMS-independent wrappers are provided for constructing several types of
1431          * expression commonly used in condition queries. See:
1432          *    - DatabaseBase::buildLike()
1433          *    - DatabaseBase::conditional()
1434          *
1435          *
1436          * @param $options string|array
1437          *
1438          * Optional: Array of query options. Boolean options are specified by
1439          * including them in the array as a string value with a numeric key, for
1440          * example:
1441          *
1442          *    array( 'FOR UPDATE' )
1443          *
1444          * The supported options are:
1445          *
1446          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1447          *     with LIMIT can theoretically be used for paging through a result set,
1448          *     but this is discouraged in MediaWiki for performance reasons.
1449          *
1450          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1451          *     and then the first rows are taken until the limit is reached. LIMIT
1452          *     is applied to a result set after OFFSET.
1453          *
1454          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1455          *     changed until the next COMMIT.
1456          *
1457          *   - DISTINCT: Boolean: return only unique result rows.
1458          *
1459          *   - GROUP BY: May be either an SQL fragment string naming a field or
1460          *     expression to group by, or an array of such SQL fragments.
1461          *
1462          *   - HAVING: May be either an string containing a HAVING clause or an array of
1463          *     conditions building the HAVING clause. If an array is given, the conditions
1464          *     constructed from each element are combined with AND.
1465          *
1466          *   - ORDER BY: May be either an SQL fragment giving a field name or
1467          *     expression to order by, or an array of such SQL fragments.
1468          *
1469          *   - USE INDEX: This may be either a string giving the index name to use
1470          *     for the query, or an array. If it is an associative array, each key
1471          *     gives the table name (or alias), each value gives the index name to
1472          *     use for that table. All strings are SQL fragments and so should be
1473          *     validated by the caller.
1474          *
1475          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1476          *     instead of SELECT.
1477          *
1478          * And also the following boolean MySQL extensions, see the MySQL manual
1479          * for documentation:
1480          *
1481          *    - LOCK IN SHARE MODE
1482          *    - STRAIGHT_JOIN
1483          *    - HIGH_PRIORITY
1484          *    - SQL_BIG_RESULT
1485          *    - SQL_BUFFER_RESULT
1486          *    - SQL_SMALL_RESULT
1487          *    - SQL_CALC_FOUND_ROWS
1488          *    - SQL_CACHE
1489          *    - SQL_NO_CACHE
1490          *
1491          *
1492          * @param $join_conds string|array
1493          *
1494          * Optional associative array of table-specific join conditions. In the
1495          * most common case, this is unnecessary, since the join condition can be
1496          * in $conds. However, it is useful for doing a LEFT JOIN.
1497          *
1498          * The key of the array contains the table name or alias. The value is an
1499          * array with two elements, numbered 0 and 1. The first gives the type of
1500          * join, the second is an SQL fragment giving the join condition for that
1501          * table. For example:
1502          *
1503          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1504          *
1505          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1506          *   with no rows in it will be returned. If there was a query error, a
1507          *   DBQueryError exception will be thrown, except if the "ignore errors"
1508          *   option was set, in which case false will be returned.
1509          */
1510         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1511                 $options = array(), $join_conds = array() ) {
1512                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1513
1514                 return $this->query( $sql, $fname );
1515         }
1516
1517         /**
1518          * The equivalent of DatabaseBase::select() except that the constructed SQL
1519          * is returned, instead of being immediately executed. This can be useful for
1520          * doing UNION queries, where the SQL text of each query is needed. In general,
1521          * however, callers outside of Database classes should just use select().
1522          *
1523          * @param string|array $table Table name
1524          * @param string|array $vars Field names
1525          * @param string|array $conds Conditions
1526          * @param string $fname Caller function name
1527          * @param string|array $options Query options
1528          * @param $join_conds string|array Join conditions
1529          *
1530          * @return string SQL query string.
1531          * @see DatabaseBase::select()
1532          */
1533         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1534                 $options = array(), $join_conds = array() )
1535         {
1536                 if ( is_array( $vars ) ) {
1537                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1538                 }
1539
1540                 $options = (array)$options;
1541                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1542                         ? $options['USE INDEX']
1543                         : array();
1544
1545                 if ( is_array( $table ) ) {
1546                         $from = ' FROM ' .
1547                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1548                 } elseif ( $table != '' ) {
1549                         if ( $table[0] == ' ' ) {
1550                                 $from = ' FROM ' . $table;
1551                         } else {
1552                                 $from = ' FROM ' .
1553                                         $this->tableNamesWithUseIndexOrJOIN( array( $table ), $useIndexes, array() );
1554                         }
1555                 } else {
1556                         $from = '';
1557                 }
1558
1559                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1560                         $this->makeSelectOptions( $options );
1561
1562                 if ( !empty( $conds ) ) {
1563                         if ( is_array( $conds ) ) {
1564                                 $conds = $this->makeList( $conds, LIST_AND );
1565                         }
1566                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1567                 } else {
1568                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1569                 }
1570
1571                 if ( isset( $options['LIMIT'] ) ) {
1572                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1573                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1574                 }
1575                 $sql = "$sql $postLimitTail";
1576
1577                 if ( isset( $options['EXPLAIN'] ) ) {
1578                         $sql = 'EXPLAIN ' . $sql;
1579                 }
1580
1581                 return $sql;
1582         }
1583
1584         /**
1585          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1586          * that a single row object is returned. If the query returns no rows,
1587          * false is returned.
1588          *
1589          * @param string|array $table Table name
1590          * @param string|array $vars Field names
1591          * @param array $conds Conditions
1592          * @param string $fname Caller function name
1593          * @param string|array $options Query options
1594          * @param $join_conds array|string Join conditions
1595          *
1596          * @return object|bool
1597          */
1598         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1599                 $options = array(), $join_conds = array() )
1600         {
1601                 $options = (array)$options;
1602                 $options['LIMIT'] = 1;
1603                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1604
1605                 if ( $res === false ) {
1606                         return false;
1607                 }
1608
1609                 if ( !$this->numRows( $res ) ) {
1610                         return false;
1611                 }
1612
1613                 $obj = $this->fetchObject( $res );
1614
1615                 return $obj;
1616         }
1617
1618         /**
1619          * Estimate rows in dataset.
1620          *
1621          * MySQL allows you to estimate the number of rows that would be returned
1622          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1623          * index cardinality statistics, and is notoriously inaccurate, especially
1624          * when large numbers of rows have recently been added or deleted.
1625          *
1626          * For DBMSs that don't support fast result size estimation, this function
1627          * will actually perform the SELECT COUNT(*).
1628          *
1629          * Takes the same arguments as DatabaseBase::select().
1630          *
1631          * @param string $table table name
1632          * @param array|string $vars : unused
1633          * @param array|string $conds : filters on the table
1634          * @param string $fname function name for profiling
1635          * @param array $options options for select
1636          * @return Integer: row count
1637          */
1638         public function estimateRowCount( $table, $vars = '*', $conds = '',
1639                 $fname = __METHOD__, $options = array() )
1640         {
1641                 $rows = 0;
1642                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1643
1644                 if ( $res ) {
1645                         $row = $this->fetchRow( $res );
1646                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1647                 }
1648
1649                 return $rows;
1650         }
1651
1652         /**
1653          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1654          * It's only slightly flawed. Don't use for anything important.
1655          *
1656          * @param string $sql A SQL Query
1657          *
1658          * @return string
1659          */
1660         static function generalizeSQL( $sql ) {
1661                 # This does the same as the regexp below would do, but in such a way
1662                 # as to avoid crashing php on some large strings.
1663                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1664
1665                 $sql = str_replace( "\\\\", '', $sql );
1666                 $sql = str_replace( "\\'", '', $sql );
1667                 $sql = str_replace( "\\\"", '', $sql );
1668                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1669                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1670
1671                 # All newlines, tabs, etc replaced by single space
1672                 $sql = preg_replace( '/\s+/', ' ', $sql );
1673
1674                 # All numbers => N
1675                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1676                 $sql = preg_replace( '/-?\d+/s', 'N', $sql );
1677
1678                 return $sql;
1679         }
1680
1681         /**
1682          * Determines whether a field exists in a table
1683          *
1684          * @param string $table table name
1685          * @param string $field filed to check on that table
1686          * @param string $fname calling function name (optional)
1687          * @return Boolean: whether $table has filed $field
1688          */
1689         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1690                 $info = $this->fieldInfo( $table, $field );
1691
1692                 return (bool)$info;
1693         }
1694
1695         /**
1696          * Determines whether an index exists
1697          * Usually throws a DBQueryError on failure
1698          * If errors are explicitly ignored, returns NULL on failure
1699          *
1700          * @param $table
1701          * @param $index
1702          * @param $fname string
1703          *
1704          * @return bool|null
1705          */
1706         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1707                 if ( !$this->tableExists( $table ) ) {
1708                         return null;
1709                 }
1710
1711                 $info = $this->indexInfo( $table, $index, $fname );
1712                 if ( is_null( $info ) ) {
1713                         return null;
1714                 } else {
1715                         return $info !== false;
1716                 }
1717         }
1718
1719         /**
1720          * Query whether a given table exists
1721          *
1722          * @param $table string
1723          * @param $fname string
1724          *
1725          * @return bool
1726          */
1727         public function tableExists( $table, $fname = __METHOD__ ) {
1728                 $table = $this->tableName( $table );
1729                 $old = $this->ignoreErrors( true );
1730                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1731                 $this->ignoreErrors( $old );
1732
1733                 return (bool)$res;
1734         }
1735
1736         /**
1737          * mysql_field_type() wrapper
1738          * @param $res
1739          * @param $index
1740          * @return string
1741          */
1742         public function fieldType( $res, $index ) {
1743                 if ( $res instanceof ResultWrapper ) {
1744                         $res = $res->result;
1745                 }
1746
1747                 return mysql_field_type( $res, $index );
1748         }
1749
1750         /**
1751          * Determines if a given index is unique
1752          *
1753          * @param $table string
1754          * @param $index string
1755          *
1756          * @return bool
1757          */
1758         public function indexUnique( $table, $index ) {
1759                 $indexInfo = $this->indexInfo( $table, $index );
1760
1761                 if ( !$indexInfo ) {
1762                         return null;
1763                 }
1764
1765                 return !$indexInfo[0]->Non_unique;
1766         }
1767
1768         /**
1769          * Helper for DatabaseBase::insert().
1770          *
1771          * @param $options array
1772          * @return string
1773          */
1774         protected function makeInsertOptions( $options ) {
1775                 return implode( ' ', $options );
1776         }
1777
1778         /**
1779          * INSERT wrapper, inserts an array into a table.
1780          *
1781          * $a may be either:
1782          *
1783          *   - A single associative array. The array keys are the field names, and
1784          *     the values are the values to insert. The values are treated as data
1785          *     and will be quoted appropriately. If NULL is inserted, this will be
1786          *     converted to a database NULL.
1787          *   - An array with numeric keys, holding a list of associative arrays.
1788          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1789          *     each subarray must be identical to each other, and in the same order.
1790          *
1791          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1792          * returns success.
1793          *
1794          * $options is an array of options, with boolean options encoded as values
1795          * with numeric keys, in the same style as $options in
1796          * DatabaseBase::select(). Supported options are:
1797          *
1798          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1799          *     any rows which cause duplicate key errors are not inserted. It's
1800          *     possible to determine how many rows were successfully inserted using
1801          *     DatabaseBase::affectedRows().
1802          *
1803          * @param $table   String Table name. This will be passed through
1804          *                 DatabaseBase::tableName().
1805          * @param $a       Array of rows to insert
1806          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1807          * @param array $options of options
1808          *
1809          * @return bool
1810          */
1811         public function insert( $table, $a, $fname = __METHOD__, $options = array() ) {
1812                 # No rows to insert, easy just return now
1813                 if ( !count( $a ) ) {
1814                         return true;
1815                 }
1816
1817                 $table = $this->tableName( $table );
1818
1819                 if ( !is_array( $options ) ) {
1820                         $options = array( $options );
1821                 }
1822
1823                 $fh = null;
1824                 if ( isset( $options['fileHandle'] ) ) {
1825                         $fh = $options['fileHandle'];
1826                 }
1827                 $options = $this->makeInsertOptions( $options );
1828
1829                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1830                         $multi = true;
1831                         $keys = array_keys( $a[0] );
1832                 } else {
1833                         $multi = false;
1834                         $keys = array_keys( $a );
1835                 }
1836
1837                 $sql = 'INSERT ' . $options .
1838                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1839
1840                 if ( $multi ) {
1841                         $first = true;
1842                         foreach ( $a as $row ) {
1843                                 if ( $first ) {
1844                                         $first = false;
1845                                 } else {
1846                                         $sql .= ',';
1847                                 }
1848                                 $sql .= '(' . $this->makeList( $row ) . ')';
1849                         }
1850                 } else {
1851                         $sql .= '(' . $this->makeList( $a ) . ')';
1852                 }
1853
1854                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1855                         return false;
1856                 } elseif ( $fh !== null ) {
1857                         return true;
1858                 }
1859
1860                 return (bool)$this->query( $sql, $fname );
1861         }
1862
1863         /**
1864          * Make UPDATE options for the DatabaseBase::update function
1865          *
1866          * @param array $options The options passed to DatabaseBase::update
1867          * @return string
1868          */
1869         protected function makeUpdateOptions( $options ) {
1870                 if ( !is_array( $options ) ) {
1871                         $options = array( $options );
1872                 }
1873
1874                 $opts = array();
1875
1876                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1877                         $opts[] = $this->lowPriorityOption();
1878                 }
1879
1880                 if ( in_array( 'IGNORE', $options ) ) {
1881                         $opts[] = 'IGNORE';
1882                 }
1883
1884                 return implode( ' ', $opts );
1885         }
1886
1887         /**
1888          * UPDATE wrapper. Takes a condition array and a SET array.
1889          *
1890          * @param $table  String name of the table to UPDATE. This will be passed through
1891          *                DatabaseBase::tableName().
1892          *
1893          * @param array $values  An array of values to SET. For each array element,
1894          *                the key gives the field name, and the value gives the data
1895          *                to set that field to. The data will be quoted by
1896          *                DatabaseBase::addQuotes().
1897          *
1898          * @param $conds  Array:  An array of conditions (WHERE). See
1899          *                DatabaseBase::select() for the details of the format of
1900          *                condition arrays. Use '*' to update all rows.
1901          *
1902          * @param $fname  String: The function name of the caller (from __METHOD__),
1903          *                for logging and profiling.
1904          *
1905          * @param array $options An array of UPDATE options, can be:
1906          *                   - IGNORE: Ignore unique key conflicts
1907          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1908          * @return Boolean
1909          */
1910         function update( $table, $values, $conds, $fname = __METHOD__, $options = array() ) {
1911                 $table = $this->tableName( $table );
1912                 $opts = $this->makeUpdateOptions( $options );
1913                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1914
1915                 if ( $conds !== array() && $conds !== '*' ) {
1916                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1917                 }
1918
1919                 return $this->query( $sql, $fname );
1920         }
1921
1922         /**
1923          * Makes an encoded list of strings from an array
1924          * @param array $a containing the data
1925          * @param int $mode Constant
1926          *      - LIST_COMMA:          comma separated, no field names
1927          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1928          *        the documentation for $conds in DatabaseBase::select().
1929          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1930          *      - LIST_SET:            comma separated with field names, like a SET clause
1931          *      - LIST_NAMES:          comma separated field names
1932          *
1933          * @throws MWException|DBUnexpectedError
1934          * @return string
1935          */
1936         public function makeList( $a, $mode = LIST_COMMA ) {
1937                 if ( !is_array( $a ) ) {
1938                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1939                 }
1940
1941                 $first = true;
1942                 $list = '';
1943
1944                 foreach ( $a as $field => $value ) {
1945                         if ( !$first ) {
1946                                 if ( $mode == LIST_AND ) {
1947                                         $list .= ' AND ';
1948                                 } elseif ( $mode == LIST_OR ) {
1949                                         $list .= ' OR ';
1950                                 } else {
1951                                         $list .= ',';
1952                                 }
1953                         } else {
1954                                 $first = false;
1955                         }
1956
1957                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1958                                 $list .= "($value)";
1959                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1960                                 $list .= "$value";
1961                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1962                                 if ( count( $value ) == 0 ) {
1963                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1964                                 } elseif ( count( $value ) == 1 ) {
1965                                         // Special-case single values, as IN isn't terribly efficient
1966                                         // Don't necessarily assume the single key is 0; we don't
1967                                         // enforce linear numeric ordering on other arrays here.
1968                                         $value = array_values( $value );
1969                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1970                                 } else {
1971                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1972                                 }
1973                         } elseif ( $value === null ) {
1974                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1975                                         $list .= "$field IS ";
1976                                 } elseif ( $mode == LIST_SET ) {
1977                                         $list .= "$field = ";
1978                                 }
1979                                 $list .= 'NULL';
1980                         } else {
1981                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1982                                         $list .= "$field = ";
1983                                 }
1984                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1985                         }
1986                 }
1987
1988                 return $list;
1989         }
1990
1991         /**
1992          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1993          * The keys on each level may be either integers or strings.
1994          *
1995          * @param array $data organized as 2-d
1996          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
1997          * @param string $baseKey field name to match the base-level keys to (eg 'pl_namespace')
1998          * @param string $subKey field name to match the sub-level keys to (eg 'pl_title')
1999          * @return Mixed: string SQL fragment, or false if no items in array.
2000          */
2001         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2002                 $conds = array();
2003
2004                 foreach ( $data as $base => $sub ) {
2005                         if ( count( $sub ) ) {
2006                                 $conds[] = $this->makeList(
2007                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
2008                                         LIST_AND );
2009                         }
2010                 }
2011
2012                 if ( $conds ) {
2013                         return $this->makeList( $conds, LIST_OR );
2014                 } else {
2015                         // Nothing to search for...
2016                         return false;
2017                 }
2018         }
2019
2020         /**
2021          * Return aggregated value alias
2022          *
2023          * @param $valuedata
2024          * @param $valuename string
2025          *
2026          * @return string
2027          */
2028         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2029                 return $valuename;
2030         }
2031
2032         /**
2033          * @param $field
2034          * @return string
2035          */
2036         public function bitNot( $field ) {
2037                 return "(~$field)";
2038         }
2039
2040         /**
2041          * @param $fieldLeft
2042          * @param $fieldRight
2043          * @return string
2044          */
2045         public function bitAnd( $fieldLeft, $fieldRight ) {
2046                 return "($fieldLeft & $fieldRight)";
2047         }
2048
2049         /**
2050          * @param  $fieldLeft
2051          * @param  $fieldRight
2052          * @return string
2053          */
2054         public function bitOr( $fieldLeft, $fieldRight ) {
2055                 return "($fieldLeft | $fieldRight)";
2056         }
2057
2058         /**
2059          * Build a concatenation list to feed into a SQL query
2060          * @param array $stringList list of raw SQL expressions; caller is responsible for any quoting
2061          * @return String
2062          */
2063         public function buildConcat( $stringList ) {
2064                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2065         }
2066
2067         /**
2068          * Change the current database
2069          *
2070          * @todo Explain what exactly will fail if this is not overridden.
2071          *
2072          * @param $db
2073          *
2074          * @return bool Success or failure
2075          */
2076         public function selectDB( $db ) {
2077                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
2078                 # if your database engine supports a concept similar to MySQL's
2079                 # databases you may as well.
2080                 $this->mDBname = $db;
2081                 return true;
2082         }
2083
2084         /**
2085          * Get the current DB name
2086          */
2087         public function getDBname() {
2088                 return $this->mDBname;
2089         }
2090
2091         /**
2092          * Get the server hostname or IP address
2093          */
2094         public function getServer() {
2095                 return $this->mServer;
2096         }
2097
2098         /**
2099          * Format a table name ready for use in constructing an SQL query
2100          *
2101          * This does two important things: it quotes the table names to clean them up,
2102          * and it adds a table prefix if only given a table name with no quotes.
2103          *
2104          * All functions of this object which require a table name call this function
2105          * themselves. Pass the canonical name to such functions. This is only needed
2106          * when calling query() directly.
2107          *
2108          * @param string $name database table name
2109          * @param string $format One of:
2110          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2111          *            so that it can be used in a query.
2112          *   raw - Do not add identifier quotes to the table name
2113          * @return String: full database name
2114          */
2115         public function tableName( $name, $format = 'quoted' ) {
2116                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
2117                 # Skip the entire process when we have a string quoted on both ends.
2118                 # Note that we check the end so that we will still quote any use of
2119                 # use of `database`.table. But won't break things if someone wants
2120                 # to query a database table with a dot in the name.
2121                 if ( $this->isQuotedIdentifier( $name ) ) {
2122                         return $name;
2123                 }
2124
2125                 # Lets test for any bits of text that should never show up in a table
2126                 # name. Basically anything like JOIN or ON which are actually part of
2127                 # SQL queries, but may end up inside of the table value to combine
2128                 # sql. Such as how the API is doing.
2129                 # Note that we use a whitespace test rather than a \b test to avoid
2130                 # any remote case where a word like on may be inside of a table name
2131                 # surrounded by symbols which may be considered word breaks.
2132                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2133                         return $name;
2134                 }
2135
2136                 # Split database and table into proper variables.
2137                 # We reverse the explode so that database.table and table both output
2138                 # the correct table.
2139                 $dbDetails = explode( '.', $name, 2 );
2140                 if ( count( $dbDetails ) == 2 ) {
2141                         list( $database, $table ) = $dbDetails;
2142                         # We don't want any prefix added in this case
2143                         $prefix = '';
2144                 } else {
2145                         list( $table ) = $dbDetails;
2146                         if ( $wgSharedDB !== null # We have a shared database
2147                                 && $this->mForeign == false # We're not working on a foreign database
2148                                 && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
2149                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2150                         ) {
2151                                 $database = $wgSharedDB;
2152                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2153                         } else {
2154                                 $database = null;
2155                                 $prefix = $this->mTablePrefix; # Default prefix
2156                         }
2157                 }
2158
2159                 # Quote $table and apply the prefix if not quoted.
2160                 $tableName = "{$prefix}{$table}";
2161                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) ) {
2162                         $tableName = $this->addIdentifierQuotes( $tableName );
2163                 }
2164
2165                 # Quote $database and merge it with the table name if needed
2166                 if ( $database !== null ) {
2167                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2168                                 $database = $this->addIdentifierQuotes( $database );
2169                         }
2170                         $tableName = $database . '.' . $tableName;
2171                 }
2172
2173                 return $tableName;
2174         }
2175
2176         /**
2177          * Fetch a number of table names into an array
2178          * This is handy when you need to construct SQL for joins
2179          *
2180          * Example:
2181          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2182          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2183          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2184          *
2185          * @return array
2186          */
2187         public function tableNames() {
2188                 $inArray = func_get_args();
2189                 $retVal = array();
2190
2191                 foreach ( $inArray as $name ) {
2192                         $retVal[$name] = $this->tableName( $name );
2193                 }
2194
2195                 return $retVal;
2196         }
2197
2198         /**
2199          * Fetch a number of table names into an zero-indexed numerical array
2200          * This is handy when you need to construct SQL for joins
2201          *
2202          * Example:
2203          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2204          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2205          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2206          *
2207          * @return array
2208          */
2209         public function tableNamesN() {
2210                 $inArray = func_get_args();
2211                 $retVal = array();
2212
2213                 foreach ( $inArray as $name ) {
2214                         $retVal[] = $this->tableName( $name );
2215                 }
2216
2217                 return $retVal;
2218         }
2219
2220         /**
2221          * Get an aliased table name
2222          * e.g. tableName AS newTableName
2223          *
2224          * @param string $name Table name, see tableName()
2225          * @param string|bool $alias Alias (optional)
2226          * @return string SQL name for aliased table. Will not alias a table to its own name
2227          */
2228         public function tableNameWithAlias( $name, $alias = false ) {
2229                 if ( !$alias || $alias == $name ) {
2230                         return $this->tableName( $name );
2231                 } else {
2232                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2233                 }
2234         }
2235
2236         /**
2237          * Gets an array of aliased table names
2238          *
2239          * @param $tables array( [alias] => table )
2240          * @return array of strings, see tableNameWithAlias()
2241          */
2242         public function tableNamesWithAlias( $tables ) {
2243                 $retval = array();
2244                 foreach ( $tables as $alias => $table ) {
2245                         if ( is_numeric( $alias ) ) {
2246                                 $alias = $table;
2247                         }
2248                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2249                 }
2250                 return $retval;
2251         }
2252
2253         /**
2254          * Get an aliased field name
2255          * e.g. fieldName AS newFieldName
2256          *
2257          * @param string $name Field name
2258          * @param string|bool $alias Alias (optional)
2259          * @return string SQL name for aliased field. Will not alias a field to its own name
2260          */
2261         public function fieldNameWithAlias( $name, $alias = false ) {
2262                 if ( !$alias || (string)$alias === (string)$name ) {
2263                         return $name;
2264                 } else {
2265                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2266                 }
2267         }
2268
2269         /**
2270          * Gets an array of aliased field names
2271          *
2272          * @param $fields array( [alias] => field )
2273          * @return array of strings, see fieldNameWithAlias()
2274          */
2275         public function fieldNamesWithAlias( $fields ) {
2276                 $retval = array();
2277                 foreach ( $fields as $alias => $field ) {
2278                         if ( is_numeric( $alias ) ) {
2279                                 $alias = $field;
2280                         }
2281                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2282                 }
2283                 return $retval;
2284         }
2285
2286         /**
2287          * Get the aliased table name clause for a FROM clause
2288          * which might have a JOIN and/or USE INDEX clause
2289          *
2290          * @param array $tables ( [alias] => table )
2291          * @param $use_index array Same as for select()
2292          * @param $join_conds array Same as for select()
2293          * @return string
2294          */
2295         protected function tableNamesWithUseIndexOrJOIN(
2296                 $tables, $use_index = array(), $join_conds = array()
2297         ) {
2298                 $ret = array();
2299                 $retJOIN = array();
2300                 $use_index = (array)$use_index;
2301                 $join_conds = (array)$join_conds;
2302
2303                 foreach ( $tables as $alias => $table ) {
2304                         if ( !is_string( $alias ) ) {
2305                                 // No alias? Set it equal to the table name
2306                                 $alias = $table;
2307                         }
2308                         // Is there a JOIN clause for this table?
2309                         if ( isset( $join_conds[$alias] ) ) {
2310                                 list( $joinType, $conds ) = $join_conds[$alias];
2311                                 $tableClause = $joinType;
2312                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2313                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2314                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2315                                         if ( $use != '' ) {
2316                                                 $tableClause .= ' ' . $use;
2317                                         }
2318                                 }
2319                                 $on = $this->makeList( (array)$conds, LIST_AND );
2320                                 if ( $on != '' ) {
2321                                         $tableClause .= ' ON (' . $on . ')';
2322                                 }
2323
2324                                 $retJOIN[] = $tableClause;
2325                         // Is there an INDEX clause for this table?
2326                         } elseif ( isset( $use_index[$alias] ) ) {
2327                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2328                                 $tableClause .= ' ' . $this->useIndexClause(
2329                                         implode( ',', (array)$use_index[$alias] ) );
2330
2331                                 $ret[] = $tableClause;
2332                         } else {
2333                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2334
2335                                 $ret[] = $tableClause;
2336                         }
2337                 }
2338
2339                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2340                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2341                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2342
2343                 // Compile our final table clause
2344                 return implode( ' ', array( $implicitJoins, $explicitJoins ) );
2345         }
2346
2347         /**
2348          * Get the name of an index in a given table
2349          *
2350          * @param $index
2351          *
2352          * @return string
2353          */
2354         protected function indexName( $index ) {
2355                 // Backwards-compatibility hack
2356                 $renamed = array(
2357                         'ar_usertext_timestamp' => 'usertext_timestamp',
2358                         'un_user_id' => 'user_id',
2359                         'un_user_ip' => 'user_ip',
2360                 );
2361
2362                 if ( isset( $renamed[$index] ) ) {
2363                         return $renamed[$index];
2364                 } else {
2365                         return $index;
2366                 }
2367         }
2368
2369         /**
2370          * Adds quotes and backslashes.
2371          *
2372          * @param $s string
2373          *
2374          * @return string
2375          */
2376         public function addQuotes( $s ) {
2377                 if ( $s === null ) {
2378                         return 'NULL';
2379                 } else {
2380                         # This will also quote numeric values. This should be harmless,
2381                         # and protects against weird problems that occur when they really
2382                         # _are_ strings such as article titles and string->number->string
2383                         # conversion is not 1:1.
2384                         return "'" . $this->strencode( $s ) . "'";
2385                 }
2386         }
2387
2388         /**
2389          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2390          * MySQL uses `backticks` while basically everything else uses double quotes.
2391          * Since MySQL is the odd one out here the double quotes are our generic
2392          * and we implement backticks in DatabaseMysql.
2393          *
2394          * @param $s string
2395          *
2396          * @return string
2397          */
2398         public function addIdentifierQuotes( $s ) {
2399                 return '"' . str_replace( '"', '""', $s ) . '"';
2400         }
2401
2402         /**
2403          * Returns if the given identifier looks quoted or not according to
2404          * the database convention for quoting identifiers .
2405          *
2406          * @param $name string
2407          *
2408          * @return boolean
2409          */
2410         public function isQuotedIdentifier( $name ) {
2411                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2412         }
2413
2414         /**
2415          * @param $s string
2416          * @return string
2417          */
2418         protected function escapeLikeInternal( $s ) {
2419                 $s = str_replace( '\\', '\\\\', $s );
2420                 $s = $this->strencode( $s );
2421                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2422
2423                 return $s;
2424         }
2425
2426         /**
2427          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2428          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2429          * Alternatively, the function could be provided with an array of aforementioned parameters.
2430          *
2431          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2432          * for subpages of 'My page title'.
2433          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2434          *
2435          * @since 1.16
2436          * @return String: fully built LIKE statement
2437          */
2438         public function buildLike() {
2439                 $params = func_get_args();
2440
2441                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2442                         $params = $params[0];
2443                 }
2444
2445                 $s = '';
2446
2447                 foreach ( $params as $value ) {
2448                         if ( $value instanceof LikeMatch ) {
2449                                 $s .= $value->toString();
2450                         } else {
2451                                 $s .= $this->escapeLikeInternal( $value );
2452                         }
2453                 }
2454
2455                 return " LIKE '" . $s . "' ";
2456         }
2457
2458         /**
2459          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2460          *
2461          * @return LikeMatch
2462          */
2463         public function anyChar() {
2464                 return new LikeMatch( '_' );
2465         }
2466
2467         /**
2468          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2469          *
2470          * @return LikeMatch
2471          */
2472         public function anyString() {
2473                 return new LikeMatch( '%' );
2474         }
2475
2476         /**
2477          * Returns an appropriately quoted sequence value for inserting a new row.
2478          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2479          * subclass will return an integer, and save the value for insertId()
2480          *
2481          * Any implementation of this function should *not* involve reusing
2482          * sequence numbers created for rolled-back transactions.
2483          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2484          * @param $seqName string
2485          * @return null
2486          */
2487         public function nextSequenceValue( $seqName ) {
2488                 return null;
2489         }
2490
2491         /**
2492          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2493          * is only needed because a) MySQL must be as efficient as possible due to
2494          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2495          * which index to pick.  Anyway, other databases might have different
2496          * indexes on a given table.  So don't bother overriding this unless you're
2497          * MySQL.
2498          * @param $index
2499          * @return string
2500          */
2501         public function useIndexClause( $index ) {
2502                 return '';
2503         }
2504
2505         /**
2506          * REPLACE query wrapper.
2507          *
2508          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2509          * except that when there is a duplicate key error, the old row is deleted
2510          * and the new row is inserted in its place.
2511          *
2512          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2513          * perform the delete, we need to know what the unique indexes are so that
2514          * we know how to find the conflicting rows.
2515          *
2516          * It may be more efficient to leave off unique indexes which are unlikely
2517          * to collide. However if you do this, you run the risk of encountering
2518          * errors which wouldn't have occurred in MySQL.
2519          *
2520          * @param string $table The table to replace the row(s) in.
2521          * @param array $rows Can be either a single row to insert, or multiple rows,
2522          *    in the same format as for DatabaseBase::insert()
2523          * @param array $uniqueIndexes is an array of indexes. Each element may be either
2524          *    a field name or an array of field names
2525          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2526          */
2527         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2528                 $quotedTable = $this->tableName( $table );
2529
2530                 if ( count( $rows ) == 0 ) {
2531                         return;
2532                 }
2533
2534                 # Single row case
2535                 if ( !is_array( reset( $rows ) ) ) {
2536                         $rows = array( $rows );
2537                 }
2538
2539                 foreach ( $rows as $row ) {
2540                         # Delete rows which collide
2541                         if ( $uniqueIndexes ) {
2542                                 $sql = "DELETE FROM $quotedTable WHERE ";
2543                                 $first = true;
2544                                 foreach ( $uniqueIndexes as $index ) {
2545                                         if ( $first ) {
2546                                                 $first = false;
2547                                                 $sql .= '( ';
2548                                         } else {
2549                                                 $sql .= ' ) OR ( ';
2550                                         }
2551                                         if ( is_array( $index ) ) {
2552                                                 $first2 = true;
2553                                                 foreach ( $index as $col ) {
2554                                                         if ( $first2 ) {
2555                                                                 $first2 = false;
2556                                                         } else {
2557                                                                 $sql .= ' AND ';
2558                                                         }
2559                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2560                                                 }
2561                                         } else {
2562                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2563                                         }
2564                                 }
2565                                 $sql .= ' )';
2566                                 $this->query( $sql, $fname );
2567                         }
2568
2569                         # Now insert the row
2570                         $this->insert( $table, $row, $fname );
2571                 }
2572         }
2573
2574         /**
2575          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2576          * statement.
2577          *
2578          * @param string $table Table name
2579          * @param array $rows Rows to insert
2580          * @param string $fname Caller function name
2581          *
2582          * @return ResultWrapper
2583          */
2584         protected function nativeReplace( $table, $rows, $fname ) {
2585                 $table = $this->tableName( $table );
2586
2587                 # Single row case
2588                 if ( !is_array( reset( $rows ) ) ) {
2589                         $rows = array( $rows );
2590                 }
2591
2592                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2593                 $first = true;
2594
2595                 foreach ( $rows as $row ) {
2596                         if ( $first ) {
2597                                 $first = false;
2598                         } else {
2599                                 $sql .= ',';
2600                         }
2601
2602                         $sql .= '(' . $this->makeList( $row ) . ')';
2603                 }
2604
2605                 return $this->query( $sql, $fname );
2606         }
2607
2608         /**
2609          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
2610          *
2611          * This updates any conflicting rows (according to the unique indexes) using
2612          * the provided SET clause and inserts any remaining (non-conflicted) rows.
2613          *
2614          * $rows may be either:
2615          *   - A single associative array. The array keys are the field names, and
2616          *     the values are the values to insert. The values are treated as data
2617          *     and will be quoted appropriately. If NULL is inserted, this will be
2618          *     converted to a database NULL.
2619          *   - An array with numeric keys, holding a list of associative arrays.
2620          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
2621          *     each subarray must be identical to each other, and in the same order.
2622          *
2623          * It may be more efficient to leave off unique indexes which are unlikely
2624          * to collide. However if you do this, you run the risk of encountering
2625          * errors which wouldn't have occurred in MySQL.
2626          *
2627          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
2628          * returns success.
2629          *
2630          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
2631          * @param array $rows A single row or list of rows to insert
2632          * @param array $uniqueIndexes List of single field names or field name tuples
2633          * @param array $set An array of values to SET. For each array element,
2634          *                the key gives the field name, and the value gives the data
2635          *                to set that field to. The data will be quoted by
2636          *                DatabaseBase::addQuotes().
2637          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2638          * @param array $options of options
2639          *
2640          * @return bool
2641          * @since 1.22
2642          */
2643         public function upsert(
2644                 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
2645         ) {
2646                 if ( !count( $rows ) ) {
2647                         return true; // nothing to do
2648                 }
2649                 $rows = is_array( reset( $rows ) ) ? $rows : array( $rows );
2650
2651                 if ( count( $uniqueIndexes ) ) {
2652                         $clauses = array(); // list WHERE clauses that each identify a single row
2653                         foreach ( $rows as $row ) {
2654                                 foreach ( $uniqueIndexes as $index ) {
2655                                         $index = is_array( $index ) ? $index : array( $index ); // columns
2656                                         $rowKey = array(); // unique key to this row
2657                                         foreach ( $index as $column ) {
2658                                                 $rowKey[$column] = $row[$column];
2659                                         }
2660                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2661                                 }
2662                         }
2663                         $where = array( $this->makeList( $clauses, LIST_OR ) );
2664                 } else {
2665                         $where = false;
2666                 }
2667
2668                 $useTrx = !$this->mTrxLevel;
2669                 if ( $useTrx ) {
2670                         $this->begin( $fname );
2671                 }
2672                 try {
2673                         # Update any existing conflicting row(s)
2674                         if ( $where !== false ) {
2675                                 $ok = $this->update( $table, $set, $where, $fname );
2676                         } else {
2677                                 $ok = true;
2678                         }
2679                         # Now insert any non-conflicting row(s)
2680                         $ok = $this->insert( $table, $rows, $fname, array( 'IGNORE' ) ) && $ok;
2681                 } catch ( Exception $e ) {
2682                         if ( $useTrx ) {
2683                                 $this->rollback( $fname );
2684                         }
2685                         throw $e;
2686                 }
2687                 if ( $useTrx ) {
2688                         $this->commit( $fname );
2689                 }
2690
2691                 return $ok;
2692         }
2693
2694         /**
2695          * DELETE where the condition is a join.
2696          *
2697          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2698          * we use sub-selects
2699          *
2700          * For safety, an empty $conds will not delete everything. If you want to
2701          * delete all rows where the join condition matches, set $conds='*'.
2702          *
2703          * DO NOT put the join condition in $conds.
2704          *
2705          * @param $delTable   String: The table to delete from.
2706          * @param $joinTable  String: The other table.
2707          * @param $delVar     String: The variable to join on, in the first table.
2708          * @param $joinVar    String: The variable to join on, in the second table.
2709          * @param $conds      Array: Condition array of field names mapped to variables,
2710          *                    ANDed together in the WHERE clause
2711          * @param $fname      String: Calling function name (use __METHOD__) for
2712          *                    logs/profiling
2713          * @throws DBUnexpectedError
2714          */
2715         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2716                 $fname = __METHOD__ )
2717         {
2718                 if ( !$conds ) {
2719                         throw new DBUnexpectedError( $this,
2720                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2721                 }
2722
2723                 $delTable = $this->tableName( $delTable );
2724                 $joinTable = $this->tableName( $joinTable );
2725                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2726                 if ( $conds != '*' ) {
2727                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2728                 }
2729                 $sql .= ')';
2730
2731                 $this->query( $sql, $fname );
2732         }
2733
2734         /**
2735          * Returns the size of a text field, or -1 for "unlimited"
2736          *
2737          * @param $table string
2738          * @param $field string
2739          *
2740          * @return int
2741          */
2742         public function textFieldSize( $table, $field ) {
2743                 $table = $this->tableName( $table );
2744                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2745                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2746                 $row = $this->fetchObject( $res );
2747
2748                 $m = array();
2749
2750                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2751                         $size = $m[1];
2752                 } else {
2753                         $size = -1;
2754                 }
2755
2756                 return $size;
2757         }
2758
2759         /**
2760          * A string to insert into queries to show that they're low-priority, like
2761          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2762          * string and nothing bad should happen.
2763          *
2764          * @return string Returns the text of the low priority option if it is
2765          *   supported, or a blank string otherwise
2766          */
2767         public function lowPriorityOption() {
2768                 return '';
2769         }
2770
2771         /**
2772          * DELETE query wrapper.
2773          *
2774          * @param array $table Table name
2775          * @param string|array $conds of conditions. See $conds in DatabaseBase::select() for
2776          *               the format. Use $conds == "*" to delete all rows
2777          * @param string $fname name of the calling function
2778          *
2779          * @throws DBUnexpectedError
2780          * @return bool|ResultWrapper
2781          */
2782         public function delete( $table, $conds, $fname = __METHOD__ ) {
2783                 if ( !$conds ) {
2784                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2785                 }
2786
2787                 $table = $this->tableName( $table );
2788                 $sql = "DELETE FROM $table";
2789
2790                 if ( $conds != '*' ) {
2791                         if ( is_array( $conds ) ) {
2792                                 $conds = $this->makeList( $conds, LIST_AND );
2793                         }
2794                         $sql .= ' WHERE ' . $conds;
2795                 }
2796
2797                 return $this->query( $sql, $fname );
2798         }
2799
2800         /**
2801          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2802          * into another table.
2803          *
2804          * @param string $destTable The table name to insert into
2805          * @param string|array $srcTable May be either a table name, or an array of table names
2806          *    to include in a join.
2807          *
2808          * @param array $varMap must be an associative array of the form
2809          *    array( 'dest1' => 'source1', ...). Source items may be literals
2810          *    rather than field names, but strings should be quoted with
2811          *    DatabaseBase::addQuotes()
2812          *
2813          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2814          *    the details of the format of condition arrays. May be "*" to copy the
2815          *    whole table.
2816          *
2817          * @param string $fname The function name of the caller, from __METHOD__
2818          *
2819          * @param array $insertOptions Options for the INSERT part of the query, see
2820          *    DatabaseBase::insert() for details.
2821          * @param array $selectOptions Options for the SELECT part of the query, see
2822          *    DatabaseBase::select() for details.
2823          *
2824          * @return ResultWrapper
2825          */
2826         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2827                 $fname = __METHOD__,
2828                 $insertOptions = array(), $selectOptions = array() )
2829         {
2830                 $destTable = $this->tableName( $destTable );
2831
2832                 if ( is_array( $insertOptions ) ) {
2833                         $insertOptions = implode( ' ', $insertOptions );
2834                 }
2835
2836                 if ( !is_array( $selectOptions ) ) {
2837                         $selectOptions = array( $selectOptions );
2838                 }
2839
2840                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2841
2842                 if ( is_array( $srcTable ) ) {
2843                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2844                 } else {
2845                         $srcTable = $this->tableName( $srcTable );
2846                 }
2847
2848                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2849                         " SELECT $startOpts " . implode( ',', $varMap ) .
2850                         " FROM $srcTable $useIndex ";
2851
2852                 if ( $conds != '*' ) {
2853                         if ( is_array( $conds ) ) {
2854                                 $conds = $this->makeList( $conds, LIST_AND );
2855                         }
2856                         $sql .= " WHERE $conds";
2857                 }
2858
2859                 $sql .= " $tailOpts";
2860
2861                 return $this->query( $sql, $fname );
2862         }
2863
2864         /**
2865          * Construct a LIMIT query with optional offset.  This is used for query
2866          * pages.  The SQL should be adjusted so that only the first $limit rows
2867          * are returned.  If $offset is provided as well, then the first $offset
2868          * rows should be discarded, and the next $limit rows should be returned.
2869          * If the result of the query is not ordered, then the rows to be returned
2870          * are theoretically arbitrary.
2871          *
2872          * $sql is expected to be a SELECT, if that makes a difference.
2873          *
2874          * The version provided by default works in MySQL and SQLite.  It will very
2875          * likely need to be overridden for most other DBMSes.
2876          *
2877          * @param string $sql SQL query we will append the limit too
2878          * @param $limit Integer the SQL limit
2879          * @param $offset Integer|bool the SQL offset (default false)
2880          *
2881          * @throws DBUnexpectedError
2882          * @return string
2883          */
2884         public function limitResult( $sql, $limit, $offset = false ) {
2885                 if ( !is_numeric( $limit ) ) {
2886                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2887                 }
2888                 return "$sql LIMIT "
2889                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2890                         . "{$limit} ";
2891         }
2892
2893         /**
2894          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2895          * within the UNION construct.
2896          * @return Boolean
2897          */
2898         public function unionSupportsOrderAndLimit() {
2899                 return true; // True for almost every DB supported
2900         }
2901
2902         /**
2903          * Construct a UNION query
2904          * This is used for providing overload point for other DB abstractions
2905          * not compatible with the MySQL syntax.
2906          * @param array $sqls SQL statements to combine
2907          * @param $all Boolean: use UNION ALL
2908          * @return String: SQL fragment
2909          */
2910         public function unionQueries( $sqls, $all ) {
2911                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2912                 return '(' . implode( $glue, $sqls ) . ')';
2913         }
2914
2915         /**
2916          * Returns an SQL expression for a simple conditional.  This doesn't need
2917          * to be overridden unless CASE isn't supported in your DBMS.
2918          *
2919          * @param string|array $cond SQL expression which will result in a boolean value
2920          * @param string $trueVal SQL expression to return if true
2921          * @param string $falseVal SQL expression to return if false
2922          * @return String: SQL fragment
2923          */
2924         public function conditional( $cond, $trueVal, $falseVal ) {
2925                 if ( is_array( $cond ) ) {
2926                         $cond = $this->makeList( $cond, LIST_AND );
2927                 }
2928                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2929         }
2930
2931         /**
2932          * Returns a comand for str_replace function in SQL query.
2933          * Uses REPLACE() in MySQL
2934          *
2935          * @param string $orig column to modify
2936          * @param string $old column to seek
2937          * @param string $new column to replace with
2938          *
2939          * @return string
2940          */
2941         public function strreplace( $orig, $old, $new ) {
2942                 return "REPLACE({$orig}, {$old}, {$new})";
2943         }
2944
2945         /**
2946          * Determines how long the server has been up
2947          * STUB
2948          *
2949          * @return int
2950          */
2951         public function getServerUptime() {
2952                 return 0;
2953         }
2954
2955         /**
2956          * Determines if the last failure was due to a deadlock
2957          * STUB
2958          *
2959          * @return bool
2960          */
2961         public function wasDeadlock() {
2962                 return false;
2963         }
2964
2965         /**
2966          * Determines if the last failure was due to a lock timeout
2967          * STUB
2968          *
2969          * @return bool
2970          */
2971         public function wasLockTimeout() {
2972                 return false;
2973         }
2974
2975         /**
2976          * Determines if the last query error was something that should be dealt
2977          * with by pinging the connection and reissuing the query.
2978          * STUB
2979          *
2980          * @return bool
2981          */
2982         public function wasErrorReissuable() {
2983                 return false;
2984         }
2985
2986         /**
2987          * Determines if the last failure was due to the database being read-only.
2988          * STUB
2989          *
2990          * @return bool
2991          */
2992         public function wasReadOnlyError() {
2993                 return false;
2994         }
2995
2996         /**
2997          * Perform a deadlock-prone transaction.
2998          *
2999          * This function invokes a callback function to perform a set of write
3000          * queries. If a deadlock occurs during the processing, the transaction
3001          * will be rolled back and the callback function will be called again.
3002          *
3003          * Usage:
3004          *   $dbw->deadlockLoop( callback, ... );
3005          *
3006          * Extra arguments are passed through to the specified callback function.
3007          *
3008          * Returns whatever the callback function returned on its successful,
3009          * iteration, or false on error, for example if the retry limit was
3010          * reached.
3011          *
3012          * @return bool
3013          */
3014         public function deadlockLoop() {
3015                 $this->begin( __METHOD__ );
3016                 $args = func_get_args();
3017                 $function = array_shift( $args );
3018                 $oldIgnore = $this->ignoreErrors( true );
3019                 $tries = self::DEADLOCK_TRIES;
3020
3021                 if ( is_array( $function ) ) {
3022                         $fname = $function[0];
3023                 } else {
3024                         $fname = $function;
3025                 }
3026
3027                 do {
3028                         $retVal = call_user_func_array( $function, $args );
3029                         $error = $this->lastError();
3030                         $errno = $this->lastErrno();
3031                         $sql = $this->lastQuery();
3032
3033                         if ( $errno ) {
3034                                 if ( $this->wasDeadlock() ) {
3035                                         # Retry
3036                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3037                                 } else {
3038                                         $this->reportQueryError( $error, $errno, $sql, $fname );
3039                                 }
3040                         }
3041                 } while ( $this->wasDeadlock() && --$tries > 0 );
3042
3043                 $this->ignoreErrors( $oldIgnore );
3044
3045                 if ( $tries <= 0 ) {
3046                         $this->rollback( __METHOD__ );
3047                         $this->reportQueryError( $error, $errno, $sql, $fname );
3048                         return false;
3049                 } else {
3050                         $this->commit( __METHOD__ );
3051                         return $retVal;
3052                 }
3053         }
3054
3055         /**
3056          * Wait for the slave to catch up to a given master position.
3057          *
3058          * @param $pos DBMasterPos object
3059          * @param $timeout Integer: the maximum number of seconds to wait for
3060          *   synchronisation
3061          *
3062          * @return integer: zero if the slave was past that position already,
3063          *   greater than zero if we waited for some period of time, less than
3064          *   zero if we timed out.
3065          */
3066         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3067                 wfProfileIn( __METHOD__ );
3068
3069                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3070                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
3071
3072                         if ( $wait > $timeout * 1e6 ) {
3073                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
3074                                 wfProfileOut( __METHOD__ );
3075                                 return -1;
3076                         } elseif ( $wait > 0 ) {
3077                                 wfDebug( "Fake slave waiting $wait us\n" );
3078                                 usleep( $wait );
3079                                 wfProfileOut( __METHOD__ );
3080                                 return 1;
3081                         } else {
3082                                 wfDebug( "Fake slave up to date ($wait us)\n" );
3083                                 wfProfileOut( __METHOD__ );
3084                                 return 0;
3085                         }
3086                 }
3087
3088                 wfProfileOut( __METHOD__ );
3089
3090                 # Real waits are implemented in the subclass.
3091                 return 0;
3092         }
3093
3094         /**
3095          * Get the replication position of this slave
3096          *
3097          * @return DBMasterPos, or false if this is not a slave.
3098          */
3099         public function getSlavePos() {
3100                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3101                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
3102                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
3103                         return $pos;
3104                 } else {
3105                         # Stub
3106                         return false;
3107                 }
3108         }
3109
3110         /**
3111          * Get the position of this master
3112          *
3113          * @return DBMasterPos, or false if this is not a master
3114          */
3115         public function getMasterPos() {
3116                 if ( $this->mFakeMaster ) {
3117                         return new MySQLMasterPos( 'fake', microtime( true ) );
3118                 } else {
3119                         return false;
3120                 }
3121         }
3122
3123         /**
3124          * Run an anonymous function as soon as there is no transaction pending.
3125          * If there is a transaction and it is rolled back, then the callback is cancelled.
3126          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
3127          * Callbacks must commit any transactions that they begin.
3128          *
3129          * This is useful for updates to different systems or when separate transactions are needed.
3130          * For example, one might want to enqueue jobs into a system outside the database, but only
3131          * after the database is updated so that the jobs will see the data when they actually run.
3132          * It can also be used for updates that easily cause deadlocks if locks are held too long.
3133          *
3134          * @param callable $callback
3135          * @since 1.20
3136          */
3137         final public function onTransactionIdle( $callback ) {
3138                 $this->mTrxIdleCallbacks[] = array( $callback, wfGetCaller() );
3139                 if ( !$this->mTrxLevel ) {
3140                         $this->runOnTransactionIdleCallbacks();
3141                 }
3142         }
3143
3144         /**
3145          * Run an anonymous function before the current transaction commits or now if there is none.
3146          * If there is a transaction and it is rolled back, then the callback is cancelled.
3147          * Callbacks must not start nor commit any transactions.
3148          *
3149          * This is useful for updates that easily cause deadlocks if locks are held too long
3150          * but where atomicity is strongly desired for these updates and some related updates.
3151          *
3152          * @param callable $callback
3153          * @since 1.22
3154          */
3155         final public function onTransactionPreCommitOrIdle( $callback ) {
3156                 if ( $this->mTrxLevel ) {
3157                         $this->mTrxPreCommitCallbacks[] = array( $callback, wfGetCaller() );
3158                 } else {
3159                         $this->onTransactionIdle( $callback ); // this will trigger immediately
3160                 }
3161         }
3162
3163         /**
3164          * Actually any "on transaction idle" callbacks.
3165          *
3166          * @since 1.20
3167          */
3168         protected function runOnTransactionIdleCallbacks() {
3169                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
3170
3171                 $e = null; // last exception
3172                 do { // callbacks may add callbacks :)
3173                         $callbacks = $this->mTrxIdleCallbacks;
3174                         $this->mTrxIdleCallbacks = array(); // recursion guard
3175                         foreach ( $callbacks as $callback ) {
3176                                 try {
3177                                         list( $phpCallback ) = $callback;
3178                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
3179                                         call_user_func( $phpCallback );
3180                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3181                                 } catch ( Exception $e ) {}
3182                         }
3183                 } while ( count( $this->mTrxIdleCallbacks ) );
3184
3185                 if ( $e instanceof Exception ) {
3186                         throw $e; // re-throw any last exception
3187                 }
3188         }
3189
3190         /**
3191          * Actually any "on transaction pre-commit" callbacks.
3192          *
3193          * @since 1.22
3194          */
3195         protected function runOnTransactionPreCommitCallbacks() {
3196                 $e = null; // last exception
3197                 do { // callbacks may add callbacks :)
3198                         $callbacks = $this->mTrxPreCommitCallbacks;
3199                         $this->mTrxPreCommitCallbacks = array(); // recursion guard
3200                         foreach ( $callbacks as $callback ) {
3201                                 try {
3202                                         list( $phpCallback ) = $callback;
3203                                         call_user_func( $phpCallback );
3204                                 } catch ( Exception $e ) {}
3205                         }
3206                 } while ( count( $this->mTrxPreCommitCallbacks ) );
3207
3208                 if ( $e instanceof Exception ) {
3209                         throw $e; // re-throw any last exception
3210                 }
3211         }
3212
3213         /**
3214          * Begin an atomic section of statements
3215          *
3216          * If a transaction has been started already, just keep track of the given
3217          * section name to make sure the transaction is not committed pre-maturely.
3218          * This function can be used in layers (with sub-sections), so use a stack
3219          * to keep track of the different atomic sections. If there is no transaction,
3220          * start one implicitly.
3221          *
3222          * The goal of this function is to create an atomic section of SQL queries
3223          * without having to start a new transaction if it already exists.
3224          *
3225          * Atomic sections are more strict than transactions. With transactions,
3226          * attempting to begin a new transaction when one is already running results
3227          * in MediaWiki issuing a brief warning and doing an implicit commit. All
3228          * atomic levels *must* be explicitly closed using DatabaseBase::endAtomic(),
3229          * and any database transactions cannot be began or committed until all atomic
3230          * levels are closed. There is no such thing as implicitly opening or closing
3231          * an atomic section.
3232          *
3233          * @since 1.23
3234          * @param string $fname
3235          */
3236         final public function startAtomic( $fname = __METHOD__ ) {
3237                 if ( !$this->mTrxLevel ) {
3238                         $this->begin( $fname );
3239                         $this->mTrxAutomatic = true;
3240                         $this->mTrxAutomaticAtomic = true;
3241                 }
3242
3243                 $this->mTrxAtomicLevels->push( $fname );
3244         }
3245
3246         /**
3247          * Begin a transaction. If a transaction is already in progress, that transaction will be committed before the
3248          * new transaction is started.
3249          *
3250          * Note that when the DBO_TRX flag is set (which is usually the case for web requests, but not for maintenance scripts),
3251          * any previous database query will have started a transaction automatically.
3252          *
3253          * Nesting of transactions is not supported. Attempts to nest transactions will cause a warning, unless the current
3254          * transaction was started automatically because of the DBO_TRX flag.
3255          *
3256          * @param $fname string
3257          */
3258         final public function begin( $fname = __METHOD__ ) {
3259                 global $wgDebugDBTransactions;
3260
3261                 if ( $this->mTrxLevel ) { // implicit commit
3262                         if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3263                                 // If the current transaction was an automatic atomic one, then we definitely have
3264                                 // a problem. Same if there is any unclosed atomic level.
3265                                 throw new DBUnexpectedError( $this,
3266                                         "Attempted to start explicit transaction when atomic levels are still open."
3267                                 );
3268                         } elseif ( !$this->mTrxAutomatic ) {
3269                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3270                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3271                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3272                                         " performing implicit commit!";
3273                                 wfWarn( $msg );
3274                                 wfLogDBError( $msg );
3275                         } else {
3276                                 // if the transaction was automatic and has done write operations,
3277                                 // log it if $wgDebugDBTransactions is enabled.
3278                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3279                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3280                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3281                                         );
3282                                 }
3283                         }
3284
3285                         $this->runOnTransactionPreCommitCallbacks();
3286                         $this->doCommit( $fname );
3287                         if ( $this->mTrxDoneWrites ) {
3288                                 Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3289                         }
3290                         $this->runOnTransactionIdleCallbacks();
3291                 }
3292
3293                 $this->doBegin( $fname );
3294                 $this->mTrxFname = $fname;
3295                 $this->mTrxDoneWrites = false;
3296                 $this->mTrxAutomatic = false;
3297                 $this->mTrxAutomaticAtomic = false;
3298                 $this->mTrxAtomicLevels = new SplStack;
3299         }
3300
3301         /**
3302          * Issues the BEGIN command to the database server.
3303          *
3304          * @see DatabaseBase::begin()
3305          * @param type $fname
3306          */
3307         protected function doBegin( $fname ) {
3308                 $this->query( 'BEGIN', $fname );
3309                 $this->mTrxLevel = 1;
3310         }
3311
3312         /**
3313          * Ends an atomic section of SQL statements
3314          *
3315          * Ends the next section of atomic SQL statements and commits the transaction
3316          * if necessary.
3317          *
3318          * @since 1.23
3319          * @see DatabaseBase::startAtomic
3320          * @param string $fname
3321          */
3322         final public function endAtomic( $fname = __METHOD__ ) {
3323                 if ( $this->mTrxAtomicLevels->isEmpty() ||
3324                         $this->mTrxAtomicLevels->pop() !== $fname
3325                 ) {
3326                         throw new DBUnexpectedError( $this, 'Invalid atomic section ended.' );
3327                 }
3328
3329                 if ( $this->mTrxAtomicLevels->isEmpty() && $this->mTrxAutomaticAtomic ) {
3330                         $this->commit( $fname, 'flush' );
3331                 }
3332         }
3333
3334         /**
3335          * Commits a transaction previously started using begin().
3336          * If no transaction is in progress, a warning is issued.
3337          *
3338          * Nesting of transactions is not supported.
3339          *
3340          * @param $fname string
3341          * @param string $flush Flush flag, set to 'flush' to disable warnings about explicitly committing implicit
3342          *        transactions, or calling commit when no transaction is in progress.
3343          *        This will silently break any ongoing explicit transaction. Only set the flush flag if you are sure
3344          *        that it is safe to ignore these warnings in your context.
3345          */
3346         final public function commit( $fname = __METHOD__, $flush = '' ) {
3347                 if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3348                         // There are still atomic sections open. This cannot be ignored
3349                         throw new DBUnexpectedError( $this, "Attempted to commit transaction while atomic sections are still open" );
3350                 }
3351
3352                 if ( $flush != 'flush' ) {
3353                         if ( !$this->mTrxLevel ) {
3354                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3355                         } elseif ( $this->mTrxAutomatic ) {
3356                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3357                         }
3358                 } else {
3359                         if ( !$this->mTrxLevel ) {
3360                                 return; // nothing to do
3361                         } elseif ( !$this->mTrxAutomatic ) {
3362                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3363                         }
3364                 }
3365
3366                 $this->runOnTransactionPreCommitCallbacks();
3367                 $this->doCommit( $fname );
3368                 if ( $this->mTrxDoneWrites ) {
3369                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3370                 }
3371                 $this->mTrxDoneWrites = false;
3372                 $this->runOnTransactionIdleCallbacks();
3373         }
3374
3375         /**
3376          * Issues the COMMIT command to the database server.
3377          *
3378          * @see DatabaseBase::commit()
3379          * @param type $fname
3380          */
3381         protected function doCommit( $fname ) {
3382                 if ( $this->mTrxLevel ) {
3383                         $this->query( 'COMMIT', $fname );
3384                         $this->mTrxLevel = 0;
3385                 }
3386         }
3387
3388         /**
3389          * Rollback a transaction previously started using begin().
3390          * If no transaction is in progress, a warning is issued.
3391          *
3392          * No-op on non-transactional databases.
3393          *
3394          * @param $fname string
3395          */
3396         final public function rollback( $fname = __METHOD__ ) {
3397                 if ( !$this->mTrxLevel ) {
3398                         wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3399                 }
3400                 $this->doRollback( $fname );
3401                 $this->mTrxIdleCallbacks = array(); // cancel
3402                 $this->mTrxPreCommitCallbacks = array(); // cancel
3403                 $this->mTrxAtomicLevels = new SplStack;
3404                 if ( $this->mTrxDoneWrites ) {
3405                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3406                 }
3407                 $this->mTrxDoneWrites = false;
3408         }
3409
3410         /**
3411          * Issues the ROLLBACK command to the database server.
3412          *
3413          * @see DatabaseBase::rollback()
3414          * @param type $fname
3415          */
3416         protected function doRollback( $fname ) {
3417                 if ( $this->mTrxLevel ) {
3418                         $this->query( 'ROLLBACK', $fname, true );
3419                         $this->mTrxLevel = 0;
3420                 }
3421         }
3422
3423         /**
3424          * Creates a new table with structure copied from existing table
3425          * Note that unlike most database abstraction functions, this function does not
3426          * automatically append database prefix, because it works at a lower
3427          * abstraction level.
3428          * The table names passed to this function shall not be quoted (this
3429          * function calls addIdentifierQuotes when needed).
3430          *
3431          * @param string $oldName name of table whose structure should be copied
3432          * @param string $newName name of table to be created
3433          * @param $temporary Boolean: whether the new table should be temporary
3434          * @param string $fname calling function name
3435          * @throws MWException
3436          * @return Boolean: true if operation was successful
3437          */
3438         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3439                 $fname = __METHOD__
3440         ) {
3441                 throw new MWException(
3442                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3443         }
3444
3445         /**
3446          * List all tables on the database
3447          *
3448          * @param string $prefix Only show tables with this prefix, e.g. mw_
3449          * @param string $fname calling function name
3450          * @throws MWException
3451          */
3452         function listTables( $prefix = null, $fname = __METHOD__ ) {
3453                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3454         }
3455
3456         /**
3457          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3458          * to the format used for inserting into timestamp fields in this DBMS.
3459          *
3460          * The result is unquoted, and needs to be passed through addQuotes()
3461          * before it can be included in raw SQL.
3462          *
3463          * @param $ts string|int
3464          *
3465          * @return string
3466          */
3467         public function timestamp( $ts = 0 ) {
3468                 return wfTimestamp( TS_MW, $ts );
3469         }
3470
3471         /**
3472          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3473          * to the format used for inserting into timestamp fields in this DBMS. If
3474          * NULL is input, it is passed through, allowing NULL values to be inserted
3475          * into timestamp fields.
3476          *
3477          * The result is unquoted, and needs to be passed through addQuotes()
3478          * before it can be included in raw SQL.
3479          *
3480          * @param $ts string|int
3481          *
3482          * @return string
3483          */
3484         public function timestampOrNull( $ts = null ) {
3485                 if ( is_null( $ts ) ) {
3486                         return null;
3487                 } else {
3488                         return $this->timestamp( $ts );
3489                 }
3490         }
3491
3492         /**
3493          * Take the result from a query, and wrap it in a ResultWrapper if
3494          * necessary. Boolean values are passed through as is, to indicate success
3495          * of write queries or failure.
3496          *
3497          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3498          * resource, and it was necessary to call this function to convert it to
3499          * a wrapper. Nowadays, raw database objects are never exposed to external
3500          * callers, so this is unnecessary in external code. For compatibility with
3501          * old code, ResultWrapper objects are passed through unaltered.
3502          *
3503          * @param $result bool|ResultWrapper
3504          *
3505          * @return bool|ResultWrapper
3506          */
3507         public function resultObject( $result ) {
3508                 if ( empty( $result ) ) {
3509                         return false;
3510                 } elseif ( $result instanceof ResultWrapper ) {
3511                         return $result;
3512                 } elseif ( $result === true ) {
3513                         // Successful write query
3514                         return $result;
3515                 } else {
3516                         return new ResultWrapper( $this, $result );
3517                 }
3518         }
3519
3520         /**
3521          * Ping the server and try to reconnect if it there is no connection
3522          *
3523          * @return bool Success or failure
3524          */
3525         public function ping() {
3526                 # Stub.  Not essential to override.
3527                 return true;
3528         }
3529
3530         /**
3531          * Get slave lag. Currently supported only by MySQL.
3532          *
3533          * Note that this function will generate a fatal error on many
3534          * installations. Most callers should use LoadBalancer::safeGetLag()
3535          * instead.
3536          *
3537          * @return int Database replication lag in seconds
3538          */
3539         public function getLag() {
3540                 return intval( $this->mFakeSlaveLag );
3541         }
3542
3543         /**
3544          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3545          *
3546          * @return int
3547          */
3548         function maxListLen() {
3549                 return 0;
3550         }
3551
3552         /**
3553          * Some DBMSs have a special format for inserting into blob fields, they
3554          * don't allow simple quoted strings to be inserted. To insert into such
3555          * a field, pass the data through this function before passing it to
3556          * DatabaseBase::insert().
3557          * @param $b string
3558          * @return string
3559          */
3560         public function encodeBlob( $b ) {
3561                 return $b;
3562         }
3563
3564         /**
3565          * Some DBMSs return a special placeholder object representing blob fields
3566          * in result objects. Pass the object through this function to return the
3567          * original string.
3568          * @param $b string
3569          * @return string
3570          */
3571         public function decodeBlob( $b ) {
3572                 return $b;
3573         }
3574
3575         /**
3576          * Override database's default behavior. $options include:
3577          *     'connTimeout' : Set the connection timeout value in seconds.
3578          *                     May be useful for very long batch queries such as
3579          *                     full-wiki dumps, where a single query reads out over
3580          *                     hours or days.
3581          *
3582          * @param $options Array
3583          * @return void
3584          */
3585         public function setSessionOptions( array $options ) {
3586         }
3587
3588         /**
3589          * Read and execute SQL commands from a file.
3590          *
3591          * Returns true on success, error string or exception on failure (depending
3592          * on object's error ignore settings).
3593          *
3594          * @param string $filename File name to open
3595          * @param bool|callable $lineCallback Optional function called before reading each line
3596          * @param bool|callable $resultCallback Optional function called for each MySQL result
3597          * @param bool|string $fname Calling function name or false if name should be
3598          *      generated dynamically using $filename
3599          * @param bool|callable $inputCallback Callback: Optional function called for each complete line sent
3600          * @throws MWException
3601          * @throws Exception|MWException
3602          * @return bool|string
3603          */
3604         public function sourceFile(
3605                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3606         ) {
3607                 wfSuppressWarnings();
3608                 $fp = fopen( $filename, 'r' );
3609                 wfRestoreWarnings();
3610
3611                 if ( false === $fp ) {
3612                         throw new MWException( "Could not open \"{$filename}\".\n" );
3613                 }
3614
3615                 if ( !$fname ) {
3616                         $fname = __METHOD__ . "( $filename )";
3617                 }
3618
3619                 try {
3620                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3621                 }
3622                 catch ( MWException $e ) {
3623                         fclose( $fp );
3624                         throw $e;
3625                 }
3626
3627                 fclose( $fp );
3628
3629                 return $error;
3630         }
3631
3632         /**
3633          * Get the full path of a patch file. Originally based on archive()
3634          * from updaters.inc. Keep in mind this always returns a patch, as
3635          * it fails back to MySQL if no DB-specific patch can be found
3636          *
3637          * @param string $patch The name of the patch, like patch-something.sql
3638          * @return String Full path to patch file
3639          */
3640         public function patchPath( $patch ) {
3641                 global $IP;
3642
3643                 $dbType = $this->getType();
3644                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3645                         return "$IP/maintenance/$dbType/archives/$patch";
3646                 } else {
3647                         return "$IP/maintenance/archives/$patch";
3648                 }
3649         }
3650
3651         /**
3652          * Set variables to be used in sourceFile/sourceStream, in preference to the
3653          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3654          * all. If it's set to false, $GLOBALS will be used.
3655          *
3656          * @param bool|array $vars mapping variable name to value.
3657          */
3658         public function setSchemaVars( $vars ) {
3659                 $this->mSchemaVars = $vars;
3660         }
3661
3662         /**
3663          * Read and execute commands from an open file handle.
3664          *
3665          * Returns true on success, error string or exception on failure (depending
3666          * on object's error ignore settings).
3667          *
3668          * @param $fp Resource: File handle
3669          * @param $lineCallback Callback: Optional function called before reading each query
3670          * @param $resultCallback Callback: Optional function called for each MySQL result
3671          * @param string $fname Calling function name
3672          * @param $inputCallback Callback: Optional function called for each complete query sent
3673          * @return bool|string
3674          */
3675         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3676                 $fname = __METHOD__, $inputCallback = false )
3677         {
3678                 $cmd = '';
3679
3680                 while ( !feof( $fp ) ) {
3681                         if ( $lineCallback ) {
3682                                 call_user_func( $lineCallback );
3683                         }
3684
3685                         $line = trim( fgets( $fp ) );
3686
3687                         if ( $line == '' ) {
3688                                 continue;
3689                         }
3690
3691                         if ( '-' == $line[0] && '-' == $line[1] ) {
3692                                 continue;
3693                         }
3694
3695                         if ( $cmd != '' ) {
3696                                 $cmd .= ' ';
3697                         }
3698
3699                         $done = $this->streamStatementEnd( $cmd, $line );
3700
3701                         $cmd .= "$line\n";
3702
3703                         if ( $done || feof( $fp ) ) {
3704                                 $cmd = $this->replaceVars( $cmd );
3705
3706                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3707                                         $res = $this->query( $cmd, $fname );
3708
3709                                         if ( $resultCallback ) {
3710                                                 call_user_func( $resultCallback, $res, $this );
3711                                         }
3712
3713                                         if ( false === $res ) {
3714                                                 $err = $this->lastError();
3715                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3716                                         }
3717                                 }
3718                                 $cmd = '';
3719                         }
3720                 }
3721
3722                 return true;
3723         }
3724
3725         /**
3726          * Called by sourceStream() to check if we've reached a statement end
3727          *
3728          * @param string $sql SQL assembled so far
3729          * @param string $newLine New line about to be added to $sql
3730          * @return Bool Whether $newLine contains end of the statement
3731          */
3732         public function streamStatementEnd( &$sql, &$newLine ) {
3733                 if ( $this->delimiter ) {
3734                         $prev = $newLine;
3735                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3736                         if ( $newLine != $prev ) {
3737                                 return true;
3738                         }
3739                 }
3740                 return false;
3741         }
3742
3743         /**
3744          * Database independent variable replacement. Replaces a set of variables
3745          * in an SQL statement with their contents as given by $this->getSchemaVars().
3746          *
3747          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3748          *
3749          * - '{$var}' should be used for text and is passed through the database's
3750          *   addQuotes method.
3751          * - `{$var}` should be used for identifiers (eg: table and database names),
3752          *   it is passed through the database's addIdentifierQuotes method which
3753          *   can be overridden if the database uses something other than backticks.
3754          * - / *$var* / is just encoded, besides traditional table prefix and
3755          *   table options its use should be avoided.
3756          *
3757          * @param string $ins SQL statement to replace variables in
3758          * @return String The new SQL statement with variables replaced
3759          */
3760         protected function replaceSchemaVars( $ins ) {
3761                 $vars = $this->getSchemaVars();
3762                 foreach ( $vars as $var => $value ) {
3763                         // replace '{$var}'
3764                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3765                         // replace `{$var}`
3766                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3767                         // replace /*$var*/
3768                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3769                 }
3770                 return $ins;
3771         }
3772
3773         /**
3774          * Replace variables in sourced SQL
3775          *
3776          * @param $ins string
3777          *
3778          * @return string
3779          */
3780         protected function replaceVars( $ins ) {
3781                 $ins = $this->replaceSchemaVars( $ins );
3782
3783                 // Table prefixes
3784                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3785                         array( $this, 'tableNameCallback' ), $ins );
3786
3787                 // Index names
3788                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3789                         array( $this, 'indexNameCallback' ), $ins );
3790
3791                 return $ins;
3792         }
3793
3794         /**
3795          * Get schema variables. If none have been set via setSchemaVars(), then
3796          * use some defaults from the current object.
3797          *
3798          * @return array
3799          */
3800         protected function getSchemaVars() {
3801                 if ( $this->mSchemaVars ) {
3802                         return $this->mSchemaVars;
3803                 } else {
3804                         return $this->getDefaultSchemaVars();
3805                 }
3806         }
3807
3808         /**
3809          * Get schema variables to use if none have been set via setSchemaVars().
3810          *
3811          * Override this in derived classes to provide variables for tables.sql
3812          * and SQL patch files.
3813          *
3814          * @return array
3815          */
3816         protected function getDefaultSchemaVars() {
3817                 return array();
3818         }
3819
3820         /**
3821          * Table name callback
3822          *
3823          * @param $matches array
3824          *
3825          * @return string
3826          */
3827         protected function tableNameCallback( $matches ) {
3828                 return $this->tableName( $matches[1] );
3829         }
3830
3831         /**
3832          * Index name callback
3833          *
3834          * @param $matches array
3835          *
3836          * @return string
3837          */
3838         protected function indexNameCallback( $matches ) {
3839                 return $this->indexName( $matches[1] );
3840         }
3841
3842         /**
3843          * Check to see if a named lock is available. This is non-blocking.
3844          *
3845          * @param string $lockName name of lock to poll
3846          * @param string $method name of method calling us
3847          * @return Boolean
3848          * @since 1.20
3849          */
3850         public function lockIsFree( $lockName, $method ) {
3851                 return true;
3852         }
3853
3854         /**
3855          * Acquire a named lock
3856          *
3857          * Abstracted from Filestore::lock() so child classes can implement for
3858          * their own needs.
3859          *
3860          * @param string $lockName name of lock to aquire
3861          * @param string $method name of method calling us
3862          * @param $timeout Integer: timeout
3863          * @return Boolean
3864          */
3865         public function lock( $lockName, $method, $timeout = 5 ) {
3866                 return true;
3867         }
3868
3869         /**
3870          * Release a lock.
3871          *
3872          * @param string $lockName Name of lock to release
3873          * @param string $method Name of method calling us
3874          *
3875          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3876          * by this thread (in which case the lock is not released), and NULL if the named
3877          * lock did not exist
3878          */
3879         public function unlock( $lockName, $method ) {
3880                 return true;
3881         }
3882
3883         /**
3884          * Lock specific tables
3885          *
3886          * @param array $read of tables to lock for read access
3887          * @param array $write of tables to lock for write access
3888          * @param string $method name of caller
3889          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
3890          *
3891          * @return bool
3892          */
3893         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3894                 return true;
3895         }
3896
3897         /**
3898          * Unlock specific tables
3899          *
3900          * @param string $method the caller
3901          *
3902          * @return bool
3903          */
3904         public function unlockTables( $method ) {
3905                 return true;
3906         }
3907
3908         /**
3909          * Delete a table
3910          * @param $tableName string
3911          * @param $fName string
3912          * @return bool|ResultWrapper
3913          * @since 1.18
3914          */
3915         public function dropTable( $tableName, $fName = __METHOD__ ) {
3916                 if ( !$this->tableExists( $tableName, $fName ) ) {
3917                         return false;
3918                 }
3919                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3920                 if ( $this->cascadingDeletes() ) {
3921                         $sql .= " CASCADE";
3922                 }
3923                 return $this->query( $sql, $fName );
3924         }
3925
3926         /**
3927          * Get search engine class. All subclasses of this need to implement this
3928          * if they wish to use searching.
3929          *
3930          * @return String
3931          */
3932         public function getSearchEngine() {
3933                 return 'SearchEngineDummy';
3934         }
3935
3936         /**
3937          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3938          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3939          * because "i" sorts after all numbers.
3940          *
3941          * @return String
3942          */
3943         public function getInfinity() {
3944                 return 'infinity';
3945         }
3946
3947         /**
3948          * Encode an expiry time into the DBMS dependent format
3949          *
3950          * @param string $expiry timestamp for expiry, or the 'infinity' string
3951          * @return String
3952          */
3953         public function encodeExpiry( $expiry ) {
3954                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3955                         ? $this->getInfinity()
3956                         : $this->timestamp( $expiry );
3957         }
3958
3959         /**
3960          * Decode an expiry time into a DBMS independent format
3961          *
3962          * @param string $expiry DB timestamp field value for expiry
3963          * @param $format integer: TS_* constant, defaults to TS_MW
3964          * @return String
3965          */
3966         public function decodeExpiry( $expiry, $format = TS_MW ) {
3967                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3968                         ? 'infinity'
3969                         : wfTimestamp( $format, $expiry );
3970         }
3971
3972         /**
3973          * Allow or deny "big selects" for this session only. This is done by setting
3974          * the sql_big_selects session variable.
3975          *
3976          * This is a MySQL-specific feature.
3977          *
3978          * @param $value Mixed: true for allow, false for deny, or "default" to
3979          *   restore the initial value
3980          */
3981         public function setBigSelects( $value = true ) {
3982                 // no-op
3983         }
3984
3985         /**
3986          * @since 1.19
3987          */
3988         public function __toString() {
3989                 return (string)$this->mConn;
3990         }
3991
3992         /**
3993          * Run a few simple sanity checks
3994          */
3995         public function __destruct() {
3996                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
3997                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
3998                 }
3999                 if ( count( $this->mTrxIdleCallbacks ) || count( $this->mTrxPreCommitCallbacks ) ) {
4000                         $callers = array();
4001                         foreach ( $this->mTrxIdleCallbacks as $callbackInfo ) {
4002                                 $callers[] = $callbackInfo[1];
4003
4004                         }
4005                         $callers = implode( ', ', $callers );
4006                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
4007                 }
4008         }
4009 }