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