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