includes/db/Database.php

   1 <?php
   2
   3 /**
   4  * @defgroup Database Database
   5  *
   6  * This file deals with database interface functions
   7  * and query specifics/optimisations.
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write to the Free Software Foundation, Inc.,
  21  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  22  * http://www.gnu.org/copyleft/gpl.html
  23  *
  24  * @file
  25  * @ingroup Database
  26  */
  27
  28 /**
  29  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  30  * following must be implemented to support MediaWiki
  31  *
  32  * @file
  33  * @ingroup Database
  34  */
  35 interface DatabaseType {
  36         /**
  37          * Get the type of the DBMS, as it appears in $wgDBtype.
  38          *
  39          * @return string
  40          */
  41         function getType();
  42
  43         /**
  44          * Open a connection to the database. Usually aborts on failure
  45          *
  46          * @param string $server Database server host
  47          * @param string $user Database user name
  48          * @param string $password Database user password
  49          * @param string $dbName Database name
  50          * @return bool
  51          * @throws DBConnectionError
  52          */
  53         function open( $server, $user, $password, $dbName );
  54
  55         /**
  56          * Fetch the next row from the given result object, in object form.
  57          * Fields can be retrieved with $row->fieldname, with fields acting like
  58          * member variables.
  59          * If no more rows are available, false is returned.
  60          *
  61          * @param ResultWrapper|stdClass $res Object as returned from DatabaseBase::query(), etc.
  62          * @return stdClass|bool
  63          * @throws DBUnexpectedError Thrown if the database returns an error
  64          */
  65         function fetchObject( $res );
  66
  67         /**
  68          * Fetch the next row from the given result object, in associative array
  69          * form. Fields are retrieved with $row['fieldname'].
  70          * If no more rows are available, false is returned.
  71          *
  72          * @param ResultWrapper $res Result object as returned from DatabaseBase::query(), etc.
  73          * @return array|bool
  74          * @throws DBUnexpectedError Thrown if the database returns an error
  75          */
  76         function fetchRow( $res );
  77
  78         /**
  79          * Get the number of rows in a result object
  80          *
  81          * @param mixed $res A SQL result
  82          * @return int
  83          */
  84         function numRows( $res );
  85
  86         /**
  87          * Get the number of fields in a result object
  88          * @see http://www.php.net/mysql_num_fields
  89          *
  90          * @param mixed $res A SQL result
  91          * @return int
  92          */
  93         function numFields( $res );
  94
  95         /**
  96          * Get a field name in a result object
  97          * @see http://www.php.net/mysql_field_name
  98          *
  99          * @param mixed $res A SQL result
 100          * @param int $n
 101          * @return string
 102          */
 103         function fieldName( $res, $n );
 104
 105         /**
 106          * Get the inserted value of an auto-increment row
 107          *
 108          * The value inserted should be fetched from nextSequenceValue()
 109          *
 110          * Example:
 111          * $id = $dbw->nextSequenceValue( 'page_page_id_seq' );
 112          * $dbw->insert( 'page', array( 'page_id' => $id ) );
 113          * $id = $dbw->insertId();
 114          *
 115          * @return int
 116          */
 117         function insertId();
 118
 119         /**
 120          * Change the position of the cursor in a result object
 121          * @see http://www.php.net/mysql_data_seek
 122          *
 123          * @param mixed $res A SQL result
 124          * @param int $row
 125          */
 126         function dataSeek( $res, $row );
 127
 128         /**
 129          * Get the last error number
 130          * @see http://www.php.net/mysql_errno
 131          *
 132          * @return int
 133          */
 134         function lastErrno();
 135
 136         /**
 137          * Get a description of the last error
 138          * @see http://www.php.net/mysql_error
 139          *
 140          * @return string
 141          */
 142         function lastError();
 143
 144         /**
 145          * mysql_fetch_field() wrapper
 146          * Returns false if the field doesn't exist
 147          *
 148          * @param string $table Table name
 149          * @param string $field Field name
 150          *
 151          * @return Field
 152          */
 153         function fieldInfo( $table, $field );
 154
 155         /**
 156          * Get information about an index into an object
 157          * @param string $table Table name
 158          * @param string $index Index name
 159          * @param string $fname Calling function name
 160          * @return mixed Database-specific index description class or false if the index does not exist
 161          */
 162         function indexInfo( $table, $index, $fname = __METHOD__ );
 163
 164         /**
 165          * Get the number of rows affected by the last write query
 166          * @see http://www.php.net/mysql_affected_rows
 167          *
 168          * @return int
 169          */
 170         function affectedRows();
 171
 172         /**
 173          * Wrapper for addslashes()
 174          *
 175          * @param string $s String to be slashed.
 176          * @return string Slashed string.
 177          */
 178         function strencode( $s );
 179
 180         /**
 181          * Returns a wikitext link to the DB's website, e.g.,
 182          *   return "[http://www.mysql.com/ MySQL]";
 183          * Should at least contain plain text, if for some reason
 184          * your database has no website.
 185          *
 186          * @return string Wikitext of a link to the server software's web site
 187          */
 188         function getSoftwareLink();
 189
 190         /**
 191          * A string describing the current software version, like from
 192          * mysql_get_server_info().
 193          *
 194          * @return string Version information from the database server.
 195          */
 196         function getServerVersion();
 197
 198         /**
 199          * A string describing the current software version, and possibly
 200          * other details in a user-friendly way. Will be listed on Special:Version, etc.
 201          * Use getServerVersion() to get machine-friendly information.
 202          *
 203          * @return string Version information from the database server
 204          */
 205         function getServerInfo();
 206 }
 207
 208 /**
 209  * Interface for classes that implement or wrap DatabaseBase
 210  * @ingroup Database
 211  */
 212 interface IDatabase {
 213 }
 214
 215 /**
 216  * Database abstraction object
 217  * @ingroup Database
 218  */
 219 abstract class DatabaseBase implements IDatabase, DatabaseType {
 220         /** Number of times to re-try an operation in case of deadlock */
 221         const DEADLOCK_TRIES = 4;
 222
 223         /** Minimum time to wait before retry, in microseconds */
 224         const DEADLOCK_DELAY_MIN = 500000;
 225
 226         /** Maximum time to wait before retry */
 227         const DEADLOCK_DELAY_MAX = 1500000;
 228
 229 # ------------------------------------------------------------------------------
 230 # Variables
 231 # ------------------------------------------------------------------------------
 232
 233         protected $mLastQuery = '';
 234         protected $mDoneWrites = false;
 235         protected $mPHPError = false;
 236
 237         protected $mServer, $mUser, $mPassword, $mDBname;
 238
 239         /** @var resource Database connection */
 240         protected $mConn = null;
 241         protected $mOpened = false;
 242
 243         /** @var callable[] */
 244         protected $mTrxIdleCallbacks = array();
 245         /** @var callable[] */
 246         protected $mTrxPreCommitCallbacks = array();
 247
 248         protected $mTablePrefix;
 249         protected $mSchema;
 250         protected $mFlags;
 251         protected $mForeign;
 252         protected $mErrorCount = 0;
 253         protected $mLBInfo = array();
 254         protected $mDefaultBigSelects = null;
 255         protected $mSchemaVars = false;
 256
 257         protected $preparedArgs;
 258
 259         protected $htmlErrors;
 260
 261         protected $delimiter = ';';
 262
 263         /**
 264          * Either 1 if a transaction is active or 0 otherwise.
 265          * The other Trx fields may not be meaningfull if this is 0.
 266          *
 267          * @var int
 268          */
 269         protected $mTrxLevel = 0;
 270
 271         /**
 272          * Either a short hexidecimal string if a transaction is active or ""
 273          *
 274          * @var string
 275          */
 276         protected $mTrxShortId = '';
 277
 278         /**
 279          * Remembers the function name given for starting the most recent transaction via begin().
 280          * Used to provide additional context for error reporting.
 281          *
 282          * @var string
 283          * @see DatabaseBase::mTrxLevel
 284          */
 285         private $mTrxFname = null;
 286
 287         /**
 288          * Record if possible write queries were done in the last transaction started
 289          *
 290          * @var bool
 291          * @see DatabaseBase::mTrxLevel
 292          */
 293         private $mTrxDoneWrites = false;
 294
 295         /**
 296          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 297          *
 298          * @var bool
 299          * @see DatabaseBase::mTrxLevel
 300          */
 301         private $mTrxAutomatic = false;
 302
 303         /**
 304          * Array of levels of atomicity within transactions
 305          *
 306          * @var SplStack
 307          */
 308         private $mTrxAtomicLevels;
 309
 310         /**
 311          * Record if the current transaction was started implicitly by DatabaseBase::startAtomic
 312          *
 313          * @var bool
 314          */
 315         private $mTrxAutomaticAtomic = false;
 316
 317         /**
 318          * @since 1.21
 319          * @var resource File handle for upgrade
 320          */
 321         protected $fileHandle = null;
 322
 323         /**
 324          * @since 1.22
 325          * @var string[] Process cache of VIEWs names in the database
 326          */
 327         protected $allViews = null;
 328
 329 # ------------------------------------------------------------------------------
 330 # Accessors
 331 # ------------------------------------------------------------------------------
 332         # These optionally set a variable and return the previous state
 333
 334         /**
 335          * A string describing the current software version, and possibly
 336          * other details in a user-friendly way. Will be listed on Special:Version, etc.
 337          * Use getServerVersion() to get machine-friendly information.
 338          *
 339          * @return string Version information from the database server
 340          */
 341         public function getServerInfo() {
 342                 return $this->getServerVersion();
 343         }
 344
 345         /**
 346          * @return string Command delimiter used by this database engine
 347          */
 348         public function getDelimiter() {
 349                 return $this->delimiter;
 350         }
 351
 352         /**
 353          * Boolean, controls output of large amounts of debug information.
 354          * @param bool|null $debug
 355          *   - true to enable debugging
 356          *   - false to disable debugging
 357          *   - omitted or null to do nothing
 358          *
 359          * @return bool|null Previous value of the flag
 360          */
 361         public function debug( $debug = null ) {
 362                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 363         }
 364
 365         /**
 366          * Turns buffering of SQL result sets on (true) or off (false). Default is
 367          * "on".
 368          *
 369          * Unbuffered queries are very troublesome in MySQL:
 370          *
 371          *   - If another query is executed while the first query is being read
 372          *     out, the first query is killed. This means you can't call normal
 373          *     MediaWiki functions while you are reading an unbuffered query result
 374          *     from a normal wfGetDB() connection.
 375          *
 376          *   - Unbuffered queries cause the MySQL server to use large amounts of
 377          *     memory and to hold broad locks which block other queries.
 378          *
 379          * If you want to limit client-side memory, it's almost always better to
 380          * split up queries into batches using a LIMIT clause than to switch off
 381          * buffering.
 382          *
 383          * @param null|bool $buffer
 384          * @return null|bool The previous value of the flag
 385          */
 386         public function bufferResults( $buffer = null ) {
 387                 if ( is_null( $buffer ) ) {
 388                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 389                 } else {
 390                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 391                 }
 392         }
 393
 394         /**
 395          * Turns on (false) or off (true) the automatic generation and sending
 396          * of a "we're sorry, but there has been a database error" page on
 397          * database errors. Default is on (false). When turned off, the
 398          * code should use lastErrno() and lastError() to handle the
 399          * situation as appropriate.
 400          *
 401          * Do not use this function outside of the Database classes.
 402          *
 403          * @param null|bool $ignoreErrors
 404          * @return bool The previous value of the flag.
 405          */
 406         public function ignoreErrors( $ignoreErrors = null ) {
 407                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 408         }
 409
 410         /**
 411          * Gets the current transaction level.
 412          *
 413          * Historically, transactions were allowed to be "nested". This is no
 414          * longer supported, so this function really only returns a boolean.
 415          *
 416          * @return int The previous value
 417          */
 418         public function trxLevel() {
 419                 return $this->mTrxLevel;
 420         }
 421
 422         /**
 423          * Get/set the number of errors logged. Only useful when errors are ignored
 424          * @param int $count The count to set, or omitted to leave it unchanged.
 425          * @return int The error count
 426          */
 427         public function errorCount( $count = null ) {
 428                 return wfSetVar( $this->mErrorCount, $count );
 429         }
 430
 431         /**
 432          * Get/set the table prefix.
 433          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 434          * @return string The previous table prefix.
 435          */
 436         public function tablePrefix( $prefix = null ) {
 437                 return wfSetVar( $this->mTablePrefix, $prefix );
 438         }
 439
 440         /**
 441          * Get/set the db schema.
 442          * @param string $schema The database schema to set, or omitted to leave it unchanged.
 443          * @return string The previous db schema.
 444          */
 445         public function dbSchema( $schema = null ) {
 446                 return wfSetVar( $this->mSchema, $schema );
 447         }
 448
 449         /**
 450          * Set the filehandle to copy write statements to.
 451          *
 452          * @param resource $fh File handle
 453          */
 454         public function setFileHandle( $fh ) {
 455                 $this->fileHandle = $fh;
 456         }
 457
 458         /**
 459          * Get properties passed down from the server info array of the load
 460          * balancer.
 461          *
 462          * @param string $name The entry of the info array to get, or null to get the
 463          *   whole array
 464          *
 465          * @return array|mixed|null
 466          */
 467         public function getLBInfo( $name = null ) {
 468                 if ( is_null( $name ) ) {
 469                         return $this->mLBInfo;
 470                 } else {
 471                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 472                                 return $this->mLBInfo[$name];
 473                         } else {
 474                                 return null;
 475                         }
 476                 }
 477         }
 478
 479         /**
 480          * Set the LB info array, or a member of it. If called with one parameter,
 481          * the LB info array is set to that parameter. If it is called with two
 482          * parameters, the member with the given name is set to the given value.
 483          *
 484          * @param string $name
 485          * @param array $value
 486          */
 487         public function setLBInfo( $name, $value = null ) {
 488                 if ( is_null( $value ) ) {
 489                         $this->mLBInfo = $name;
 490                 } else {
 491                         $this->mLBInfo[$name] = $value;
 492                 }
 493         }
 494
 495         /**
 496          * Set lag time in seconds for a fake slave
 497          *
 498          * @param mixed $lag Valid values for this parameter are determined by the
 499          *   subclass, but should be a PHP scalar or array that would be sensible
 500          *   as part of $wgLBFactoryConf.
 501          */
 502         public function setFakeSlaveLag( $lag ) {
 503         }
 504
 505         /**
 506          * Make this connection a fake master
 507          *
 508          * @param bool $enabled
 509          */
 510         public function setFakeMaster( $enabled = true ) {
 511         }
 512
 513         /**
 514          * Returns true if this database supports (and uses) cascading deletes
 515          *
 516          * @return bool
 517          */
 518         public function cascadingDeletes() {
 519                 return false;
 520         }
 521
 522         /**
 523          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 524          *
 525          * @return bool
 526          */
 527         public function cleanupTriggers() {
 528                 return false;
 529         }
 530
 531         /**
 532          * Returns true if this database is strict about what can be put into an IP field.
 533          * Specifically, it uses a NULL value instead of an empty string.
 534          *
 535          * @return bool
 536          */
 537         public function strictIPs() {
 538                 return false;
 539         }
 540
 541         /**
 542          * Returns true if this database uses timestamps rather than integers
 543          *
 544          * @return bool
 545          */
 546         public function realTimestamps() {
 547                 return false;
 548         }
 549
 550         /**
 551          * Returns true if this database does an implicit sort when doing GROUP BY
 552          *
 553          * @return bool
 554          */
 555         public function implicitGroupby() {
 556                 return true;
 557         }
 558
 559         /**
 560          * Returns true if this database does an implicit order by when the column has an index
 561          * For example: SELECT page_title FROM page LIMIT 1
 562          *
 563          * @return bool
 564          */
 565         public function implicitOrderby() {
 566                 return true;
 567         }
 568
 569         /**
 570          * Returns true if this database can do a native search on IP columns
 571          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 572          *
 573          * @return bool
 574          */
 575         public function searchableIPs() {
 576                 return false;
 577         }
 578
 579         /**
 580          * Returns true if this database can use functional indexes
 581          *
 582          * @return bool
 583          */
 584         public function functionalIndexes() {
 585                 return false;
 586         }
 587
 588         /**
 589          * Return the last query that went through DatabaseBase::query()
 590          * @return string
 591          */
 592         public function lastQuery() {
 593                 return $this->mLastQuery;
 594         }
 595
 596         /**
 597          * Returns true if the connection may have been used for write queries.
 598          * Should return true if unsure.
 599          *
 600          * @return bool
 601          */
 602         public function doneWrites() {
 603                 return (bool)$this->mDoneWrites;
 604         }
 605
 606         /**
 607          * Returns the last time the connection may have been used for write queries.
 608          * Should return a timestamp if unsure.
 609          *
 610          * @return int|float UNIX timestamp or false
 611          * @since 1.24
 612          */
 613         public function lastDoneWrites() {
 614                 return $this->mDoneWrites ?: false;
 615         }
 616
 617         /**
 618          * Returns true if there is a transaction open with possible write
 619          * queries or transaction pre-commit/idle callbacks waiting on it to finish.
 620          *
 621          * @return bool
 622          */
 623         public function writesOrCallbacksPending() {
 624                 return $this->mTrxLevel && (
 625                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 626                 );
 627         }
 628
 629         /**
 630          * Is a connection to the database open?
 631          * @return bool
 632          */
 633         public function isOpen() {
 634                 return $this->mOpened;
 635         }
 636
 637         /**
 638          * Set a flag for this connection
 639          *
 640          * @param int $flag DBO_* constants from Defines.php:
 641          *   - DBO_DEBUG: output some debug info (same as debug())
 642          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 643          *   - DBO_TRX: automatically start transactions
 644          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 645          *       and removes it in command line mode
 646          *   - DBO_PERSISTENT: use persistant database connection
 647          */
 648         public function setFlag( $flag ) {
 649                 global $wgDebugDBTransactions;
 650                 $this->mFlags |= $flag;
 651                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 652                         wfDebug( "Implicit transactions are now enabled.\n" );
 653                 }
 654         }
 655
 656         /**
 657          * Clear a flag for this connection
 658          *
 659          * @param int $flag DBO_* constants from Defines.php:
 660          *   - DBO_DEBUG: output some debug info (same as debug())
 661          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 662          *   - DBO_TRX: automatically start transactions
 663          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 664          *       and removes it in command line mode
 665          *   - DBO_PERSISTENT: use persistant database connection
 666          */
 667         public function clearFlag( $flag ) {
 668                 global $wgDebugDBTransactions;
 669                 $this->mFlags &= ~$flag;
 670                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 671                         wfDebug( "Implicit transactions are now disabled.\n" );
 672                 }
 673         }
 674
 675         /**
 676          * Returns a boolean whether the flag $flag is set for this connection
 677          *
 678          * @param int $flag DBO_* constants from Defines.php:
 679          *   - DBO_DEBUG: output some debug info (same as debug())
 680          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 681          *   - DBO_TRX: automatically start transactions
 682          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 683          *       and removes it in command line mode
 684          *   - DBO_PERSISTENT: use persistant database connection
 685          * @return bool
 686          */
 687         public function getFlag( $flag ) {
 688                 return !!( $this->mFlags & $flag );
 689         }
 690
 691         /**
 692          * General read-only accessor
 693          *
 694          * @param string $name
 695          * @return string
 696          */
 697         public function getProperty( $name ) {
 698                 return $this->$name;
 699         }
 700
 701         /**
 702          * @return string
 703          */
 704         public function getWikiID() {
 705                 if ( $this->mTablePrefix ) {
 706                         return "{$this->mDBname}-{$this->mTablePrefix}";
 707                 } else {
 708                         return $this->mDBname;
 709                 }
 710         }
 711
 712         /**
 713          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 714          *
 715          * @return string
 716          */
 717         public function getSchemaPath() {
 718                 global $IP;
 719                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 720                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 721                 } else {
 722                         return "$IP/maintenance/tables.sql";
 723                 }
 724         }
 725
 726 # ------------------------------------------------------------------------------
 727 # Other functions
 728 # ------------------------------------------------------------------------------
 729
 730         /**
 731          * Constructor.
 732          *
 733          * FIXME: It is possible to construct a Database object with no associated
 734          * connection object, by specifying no parameters to __construct(). This
 735          * feature is deprecated and should be removed.
 736          *
 737          * DatabaseBase subclasses should not be constructed directly in external
 738          * code. DatabaseBase::factory() should be used instead.
 739          *
 740          * @param array $params Parameters passed from DatabaseBase::factory()
 741          */
 742         function __construct( $params = null ) {
 743                 global $wgDBprefix, $wgDBmwschema, $wgCommandLineMode, $wgDebugDBTransactions;
 744
 745                 $this->mTrxAtomicLevels = new SplStack;
 746
 747                 if ( is_array( $params ) ) { // MW 1.22
 748                         $server = $params['host'];
 749                         $user = $params['user'];
 750                         $password = $params['password'];
 751                         $dbName = $params['dbname'];
 752                         $flags = $params['flags'];
 753                         $tablePrefix = $params['tablePrefix'];
 754                         $schema = $params['schema'];
 755                         $foreign = $params['foreign'];
 756                 } else { // legacy calling pattern
 757                         wfDeprecated( __METHOD__ . " method called without parameter array.", "1.23" );
 758                         $args = func_get_args();
 759                         $server = isset( $args[0] ) ? $args[0] : false;
 760                         $user = isset( $args[1] ) ? $args[1] : false;
 761                         $password = isset( $args[2] ) ? $args[2] : false;
 762                         $dbName = isset( $args[3] ) ? $args[3] : false;
 763                         $flags = isset( $args[4] ) ? $args[4] : 0;
 764                         $tablePrefix = isset( $args[5] ) ? $args[5] : 'get from global';
 765                         $schema = 'get from global';
 766                         $foreign = isset( $args[6] ) ? $args[6] : false;
 767                 }
 768
 769                 $this->mFlags = $flags;
 770                 if ( $this->mFlags & DBO_DEFAULT ) {
 771                         if ( $wgCommandLineMode ) {
 772                                 $this->mFlags &= ~DBO_TRX;
 773                                 if ( $wgDebugDBTransactions ) {
 774                                         wfDebug( "Implicit transaction open disabled.\n" );
 775                                 }
 776                         } else {
 777                                 $this->mFlags |= DBO_TRX;
 778                                 if ( $wgDebugDBTransactions ) {
 779                                         wfDebug( "Implicit transaction open enabled.\n" );
 780                                 }
 781                         }
 782                 }
 783
 784                 /** Get the default table prefix*/
 785                 if ( $tablePrefix == 'get from global' ) {
 786                         $this->mTablePrefix = $wgDBprefix;
 787                 } else {
 788                         $this->mTablePrefix = $tablePrefix;
 789                 }
 790
 791                 /** Get the database schema*/
 792                 if ( $schema == 'get from global' ) {
 793                         $this->mSchema = $wgDBmwschema;
 794                 } else {
 795                         $this->mSchema = $schema;
 796                 }
 797
 798                 $this->mForeign = $foreign;
 799
 800                 if ( $user ) {
 801                         $this->open( $server, $user, $password, $dbName );
 802                 }
 803         }
 804
 805         /**
 806          * Called by serialize. Throw an exception when DB connection is serialized.
 807          * This causes problems on some database engines because the connection is
 808          * not restored on unserialize.
 809          */
 810         public function __sleep() {
 811                 throw new MWException( 'Database serialization may cause problems, since ' .
 812                         'the connection is not restored on wakeup.' );
 813         }
 814
 815         /**
 816          * Given a DB type, construct the name of the appropriate child class of
 817          * DatabaseBase. This is designed to replace all of the manual stuff like:
 818          *    $class = 'Database' . ucfirst( strtolower( $dbType ) );
 819          * as well as validate against the canonical list of DB types we have
 820          *
 821          * This factory function is mostly useful for when you need to connect to a
 822          * database other than the MediaWiki default (such as for external auth,
 823          * an extension, et cetera). Do not use this to connect to the MediaWiki
 824          * database. Example uses in core:
 825          * @see LoadBalancer::reallyOpenConnection()
 826          * @see ForeignDBRepo::getMasterDB()
 827          * @see WebInstallerDBConnect::execute()
 828          *
 829          * @since 1.18
 830          *
 831          * @param string $dbType A possible DB type
 832          * @param array $p An array of options to pass to the constructor.
 833          *    Valid options are: host, user, password, dbname, flags, tablePrefix, schema, driver
 834          * @throws MWException If the database driver or extension cannot be found
 835          * @return DatabaseBase|null DatabaseBase subclass or null
 836          */
 837         final public static function factory( $dbType, $p = array() ) {
 838                 $canonicalDBTypes = array(
 839                         'mysql' => array( 'mysqli', 'mysql' ),
 840                         'postgres' => array(),
 841                         'sqlite' => array(),
 842                         'oracle' => array(),
 843                         'mssql' => array(),
 844                 );
 845
 846                 $driver = false;
 847                 $dbType = strtolower( $dbType );
 848                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 849                         $possibleDrivers = $canonicalDBTypes[$dbType];
 850                         if ( !empty( $p['driver'] ) ) {
 851                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 852                                         $driver = $p['driver'];
 853                                 } else {
 854                                         throw new MWException( __METHOD__ .
 855                                                 " cannot construct Database with type '$dbType' and driver '{$p['driver']}'" );
 856                                 }
 857                         } else {
 858                                 foreach ( $possibleDrivers as $posDriver ) {
 859                                         if ( extension_loaded( $posDriver ) ) {
 860                                                 $driver = $posDriver;
 861                                                 break;
 862                                         }
 863                                 }
 864                         }
 865                 } else {
 866                         $driver = $dbType;
 867                 }
 868                 if ( $driver === false ) {
 869                         throw new MWException( __METHOD__ .
 870                                 " no viable database extension found for type '$dbType'" );
 871                 }
 872
 873                 // Determine schema defaults. Currently Microsoft SQL Server uses $wgDBmwschema,
 874                 // and everything else doesn't use a schema (e.g. null)
 875                 // Although postgres and oracle support schemas, we don't use them (yet)
 876                 // to maintain backwards compatibility
 877                 $defaultSchemas = array(
 878                         'mysql' => null,
 879                         'postgres' => null,
 880                         'sqlite' => null,
 881                         'oracle' => null,
 882                         'mssql' => 'get from global',
 883                 );
 884
 885                 $class = 'Database' . ucfirst( $driver );
 886                 if ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 887                         $params = array(
 888                                 'host' => isset( $p['host'] ) ? $p['host'] : false,
 889                                 'user' => isset( $p['user'] ) ? $p['user'] : false,
 890                                 'password' => isset( $p['password'] ) ? $p['password'] : false,
 891                                 'dbname' => isset( $p['dbname'] ) ? $p['dbname'] : false,
 892                                 'flags' => isset( $p['flags'] ) ? $p['flags'] : 0,
 893                                 'tablePrefix' => isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global',
 894                                 'schema' => isset( $p['schema'] ) ? $p['schema'] : $defaultSchemas[$dbType],
 895                                 'foreign' => isset( $p['foreign'] ) ? $p['foreign'] : false
 896                         );
 897
 898                         return new $class( $params );
 899                 } else {
 900                         return null;
 901                 }
 902         }
 903
 904         protected function installErrorHandler() {
 905                 $this->mPHPError = false;
 906                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 907                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 908         }
 909
 910         /**
 911          * @return bool|string
 912          */
 913         protected function restoreErrorHandler() {
 914                 restore_error_handler();
 915                 if ( $this->htmlErrors !== false ) {
 916                         ini_set( 'html_errors', $this->htmlErrors );
 917                 }
 918                 if ( $this->mPHPError ) {
 919                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 920                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 921
 922                         return $error;
 923                 } else {
 924                         return false;
 925                 }
 926         }
 927
 928         /**
 929          * @param int $errno
 930          * @param string $errstr
 931          */
 932         public function connectionErrorHandler( $errno, $errstr ) {
 933                 $this->mPHPError = $errstr;
 934         }
 935
 936         /**
 937          * Closes a database connection.
 938          * if it is open : commits any open transactions
 939          *
 940          * @throws MWException
 941          * @return bool Operation success. true if already closed.
 942          */
 943         public function close() {
 944                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 945                         throw new MWException( "Transaction idle callbacks still pending." );
 946                 }
 947                 if ( $this->mConn ) {
 948                         if ( $this->trxLevel() ) {
 949                                 if ( !$this->mTrxAutomatic ) {
 950                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 951                                                 " performing implicit commit before closing connection!" );
 952                                 }
 953
 954                                 $this->commit( __METHOD__, 'flush' );
 955                         }
 956
 957                         $closed = $this->closeConnection();
 958                         $this->mConn = false;
 959                 } else {
 960                         $closed = true;
 961                 }
 962                 $this->mOpened = false;
 963
 964                 return $closed;
 965         }
 966
 967         /**
 968          * Closes underlying database connection
 969          * @since 1.20
 970          * @return bool Whether connection was closed successfully
 971          */
 972         abstract protected function closeConnection();
 973
 974         /**
 975          * @param string $error Fallback error message, used if none is given by DB
 976          * @throws DBConnectionError
 977          */
 978         function reportConnectionError( $error = 'Unknown error' ) {
 979                 $myError = $this->lastError();
 980                 if ( $myError ) {
 981                         $error = $myError;
 982                 }
 983
 984                 # New method
 985                 throw new DBConnectionError( $this, $error );
 986         }
 987
 988         /**
 989          * The DBMS-dependent part of query()
 990          *
 991          * @param string $sql SQL query.
 992          * @return ResultWrapper|bool Result object to feed to fetchObject,
 993          *   fetchRow, ...; or false on failure
 994          */
 995         abstract protected function doQuery( $sql );
 996
 997         /**
 998          * Determine whether a query writes to the DB.
 999          * Should return true if unsure.
1000          *
1001          * @param string $sql
1002          * @return bool
1003          */
1004         public function isWriteQuery( $sql ) {
1005                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
1006         }
1007
1008         /**
1009          * Run an SQL query and return the result. Normally throws a DBQueryError
1010          * on failure. If errors are ignored, returns false instead.
1011          *
1012          * In new code, the query wrappers select(), insert(), update(), delete(),
1013          * etc. should be used where possible, since they give much better DBMS
1014          * independence and automatically quote or validate user input in a variety
1015          * of contexts. This function is generally only useful for queries which are
1016          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
1017          * as CREATE TABLE.
1018          *
1019          * However, the query wrappers themselves should call this function.
1020          *
1021          * @param string $sql SQL query
1022          * @param string $fname Name of the calling function, for profiling/SHOW PROCESSLIST
1023          *     comment (you can use __METHOD__ or add some extra info)
1024          * @param bool $tempIgnore Whether to avoid throwing an exception on errors...
1025          *     maybe best to catch the exception instead?
1026          * @throws MWException
1027          * @return bool|ResultWrapper True for a successful write query, ResultWrapper object
1028          *     for a successful read query, or false on failure if $tempIgnore set
1029          */
1030         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
1031                 global $wgUser, $wgDebugDBTransactions;
1032
1033                 $this->mLastQuery = $sql;
1034                 if ( $this->isWriteQuery( $sql ) ) {
1035                         # Set a flag indicating that writes have been done
1036                         wfDebug( __METHOD__ . ': Writes done: ' . DatabaseBase::generalizeSQL( $sql ) . "\n" );
1037                         $this->mDoneWrites = microtime( true );
1038                 }
1039
1040                 # Add a comment for easy SHOW PROCESSLIST interpretation
1041                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
1042                         $userName = $wgUser->getName();
1043                         if ( mb_strlen( $userName ) > 15 ) {
1044                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
1045                         }
1046                         $userName = str_replace( '/', '', $userName );
1047                 } else {
1048                         $userName = '';
1049                 }
1050
1051                 // Add trace comment to the begin of the sql string, right after the operator.
1052                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
1053                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
1054
1055                 # If DBO_TRX is set, start a transaction
1056                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
1057                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK'
1058                 ) {
1059                         # Avoid establishing transactions for SHOW and SET statements too -
1060                         # that would delay transaction initializations to once connection
1061                         # is really used by application
1062                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
1063                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
1064                                 if ( $wgDebugDBTransactions ) {
1065                                         wfDebug( "Implicit transaction start.\n" );
1066                                 }
1067                                 $this->begin( __METHOD__ . " ($fname)" );
1068                                 $this->mTrxAutomatic = true;
1069                         }
1070                 }
1071
1072                 # Keep track of whether the transaction has write queries pending
1073                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
1074                         $this->mTrxDoneWrites = true;
1075                         Profiler::instance()->transactionWritingIn(
1076                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
1077                 }
1078
1079                 $queryProf = '';
1080                 $totalProf = '';
1081                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1082
1083                 if ( !Profiler::instance()->isStub() ) {
1084                         # generalizeSQL will probably cut down the query to reasonable
1085                         # logging size most of the time. The substr is really just a sanity check.
1086                         if ( $isMaster ) {
1087                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
1088                                 $totalProf = 'DatabaseBase::query-master';
1089                         } else {
1090                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
1091                                 $totalProf = 'DatabaseBase::query';
1092                         }
1093                         # Include query transaction state
1094                         $queryProf .= $this->mTrxShortId ? " [TRX#{$this->mTrxShortId}]" : "";
1095
1096                         $trx = $this->mTrxLevel ? 'TRX=yes' : 'TRX=no';
1097                         wfProfileIn( $totalProf );
1098                         wfProfileIn( $queryProf );
1099                 }
1100
1101                 if ( $this->debug() ) {
1102                         static $cnt = 0;
1103
1104                         $cnt++;
1105                         $sqlx = substr( $commentedSql, 0, 500 );
1106                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
1107
1108                         $master = $isMaster ? 'master' : 'slave';
1109                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
1110                 }
1111
1112                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
1113
1114                 # Avoid fatals if close() was called
1115                 if ( !$this->isOpen() ) {
1116                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
1117                 }
1118
1119                 # Do the query and handle errors
1120                 $ret = $this->doQuery( $commentedSql );
1121
1122                 MWDebug::queryTime( $queryId );
1123
1124                 # Try reconnecting if the connection was lost
1125                 if ( false === $ret && $this->wasErrorReissuable() ) {
1126                         # Transaction is gone, like it or not
1127                         $hadTrx = $this->mTrxLevel; // possible lost transaction
1128                         $this->mTrxLevel = 0;
1129                         $this->mTrxIdleCallbacks = array(); // bug 65263
1130                         $this->mTrxPreCommitCallbacks = array(); // bug 65263
1131                         wfDebug( "Connection lost, reconnecting...\n" );
1132
1133                         if ( $this->ping() ) {
1134                                 global $wgRequestTime;
1135                                 wfDebug( "Reconnected\n" );
1136                                 $sqlx = substr( $commentedSql, 0, 500 );
1137                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
1138                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
1139                                 if ( $elapsed < 300 ) {
1140                                         # Not a database error to lose a transaction after a minute or two
1141                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx" );
1142                                 }
1143                                 if ( $hadTrx ) {
1144                                         # Leave $ret as false and let an error be reported.
1145                                         # Callers may catch the exception and continue to use the DB.
1146                                 } else {
1147                                         # Should be safe to silently retry (no trx and thus no callbacks)
1148                                         $ret = $this->doQuery( $commentedSql );
1149                                 }
1150                         } else {
1151                                 wfDebug( "Failed\n" );
1152                         }
1153                 }
1154
1155                 if ( false === $ret ) {
1156                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1157                 }
1158
1159                 if ( !Profiler::instance()->isStub() ) {
1160                         wfProfileOut( $queryProf );
1161                         wfProfileOut( $totalProf );
1162                 }
1163
1164                 return $this->resultObject( $ret );
1165         }
1166
1167         /**
1168          * Report a query error. Log the error, and if neither the object ignore
1169          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1170          *
1171          * @param string $error
1172          * @param int $errno
1173          * @param string $sql
1174          * @param string $fname
1175          * @param bool $tempIgnore
1176          * @throws DBQueryError
1177          */
1178         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1179                 # Ignore errors during error handling to avoid infinite recursion
1180                 $ignore = $this->ignoreErrors( true );
1181                 ++$this->mErrorCount;
1182
1183                 if ( $ignore || $tempIgnore ) {
1184                         wfDebug( "SQL ERROR (ignored): $error\n" );
1185                         $this->ignoreErrors( $ignore );
1186                 } else {
1187                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1188                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line" );
1189                         wfDebug( "SQL ERROR: " . $error . "\n" );
1190                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1191                 }
1192         }
1193
1194         /**
1195          * Intended to be compatible with the PEAR::DB wrapper functions.
1196          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1197          *
1198          * ? = scalar value, quoted as necessary
1199          * ! = raw SQL bit (a function for instance)
1200          * & = filename; reads the file and inserts as a blob
1201          *     (we don't use this though...)
1202          *
1203          * @param string $sql
1204          * @param string $func
1205          *
1206          * @return array
1207          */
1208         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1209                 /* MySQL doesn't support prepared statements (yet), so just
1210                  * pack up the query for reference. We'll manually replace
1211                  * the bits later.
1212                  */
1213                 return array( 'query' => $sql, 'func' => $func );
1214         }
1215
1216         /**
1217          * Free a prepared query, generated by prepare().
1218          * @param string $prepared
1219          */
1220         protected function freePrepared( $prepared ) {
1221                 /* No-op by default */
1222         }
1223
1224         /**
1225          * Execute a prepared query with the various arguments
1226          * @param string $prepared The prepared sql
1227          * @param mixed $args Either an array here, or put scalars as varargs
1228          *
1229          * @return ResultWrapper
1230          */
1231         public function execute( $prepared, $args = null ) {
1232                 if ( !is_array( $args ) ) {
1233                         # Pull the var args
1234                         $args = func_get_args();
1235                         array_shift( $args );
1236                 }
1237
1238                 $sql = $this->fillPrepared( $prepared['query'], $args );
1239
1240                 return $this->query( $sql, $prepared['func'] );
1241         }
1242
1243         /**
1244          * For faking prepared SQL statements on DBs that don't support it directly.
1245          *
1246          * @param string $preparedQuery A 'preparable' SQL statement
1247          * @param array $args Array of Arguments to fill it with
1248          * @return string Executable SQL
1249          */
1250         public function fillPrepared( $preparedQuery, $args ) {
1251                 reset( $args );
1252                 $this->preparedArgs =& $args;
1253
1254                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1255                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1256         }
1257
1258         /**
1259          * preg_callback func for fillPrepared()
1260          * The arguments should be in $this->preparedArgs and must not be touched
1261          * while we're doing this.
1262          *
1263          * @param array $matches
1264          * @throws DBUnexpectedError
1265          * @return string
1266          */
1267         protected function fillPreparedArg( $matches ) {
1268                 switch ( $matches[1] ) {
1269                         case '\\?':
1270                                 return '?';
1271                         case '\\!':
1272                                 return '!';
1273                         case '\\&':
1274                                 return '&';
1275                 }
1276
1277                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1278
1279                 switch ( $matches[1] ) {
1280                         case '?':
1281                                 return $this->addQuotes( $arg );
1282                         case '!':
1283                                 return $arg;
1284                         case '&':
1285                                 # return $this->addQuotes( file_get_contents( $arg ) );
1286                                 throw new DBUnexpectedError(
1287                                         $this,
1288                                         '& mode is not implemented. If it\'s really needed, uncomment the line above.'
1289                                 );
1290                         default:
1291                                 throw new DBUnexpectedError(
1292                                         $this,
1293                                         'Received invalid match. This should never happen!'
1294                                 );
1295                 }
1296         }
1297
1298         /**
1299          * Free a result object returned by query() or select(). It's usually not
1300          * necessary to call this, just use unset() or let the variable holding
1301          * the result object go out of scope.
1302          *
1303          * @param mixed $res A SQL result
1304          */
1305         public function freeResult( $res ) {
1306         }
1307
1308         /**
1309          * A SELECT wrapper which returns a single field from a single result row.
1310          *
1311          * Usually throws a DBQueryError on failure. If errors are explicitly
1312          * ignored, returns false on failure.
1313          *
1314          * If no result rows are returned from the query, false is returned.
1315          *
1316          * @param string|array $table Table name. See DatabaseBase::select() for details.
1317          * @param string $var The field name to select. This must be a valid SQL
1318          *   fragment: do not use unvalidated user input.
1319          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1320          * @param string $fname The function name of the caller.
1321          * @param string|array $options The query options. See DatabaseBase::select() for details.
1322          *
1323          * @return bool|mixed The value from the field, or false on failure.
1324          */
1325         public function selectField( $table, $var, $cond = '', $fname = __METHOD__,
1326                 $options = array()
1327         ) {
1328                 if ( !is_array( $options ) ) {
1329                         $options = array( $options );
1330                 }
1331
1332                 $options['LIMIT'] = 1;
1333
1334                 $res = $this->select( $table, $var, $cond, $fname, $options );
1335
1336                 if ( $res === false || !$this->numRows( $res ) ) {
1337                         return false;
1338                 }
1339
1340                 $row = $this->fetchRow( $res );
1341
1342                 if ( $row !== false ) {
1343                         return reset( $row );
1344                 } else {
1345                         return false;
1346                 }
1347         }
1348
1349         /**
1350          * Returns an optional USE INDEX clause to go after the table, and a
1351          * string to go at the end of the query.
1352          *
1353          * @param array $options Associative array of options to be turned into
1354          *   an SQL query, valid keys are listed in the function.
1355          * @return array
1356          * @see DatabaseBase::select()
1357          */
1358         public function makeSelectOptions( $options ) {
1359                 $preLimitTail = $postLimitTail = '';
1360                 $startOpts = '';
1361
1362                 $noKeyOptions = array();
1363
1364                 foreach ( $options as $key => $option ) {
1365                         if ( is_numeric( $key ) ) {
1366                                 $noKeyOptions[$option] = true;
1367                         }
1368                 }
1369
1370                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1371
1372                 $preLimitTail .= $this->makeOrderBy( $options );
1373
1374                 // if (isset($options['LIMIT'])) {
1375                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1376                 //              isset($options['OFFSET']) ? $options['OFFSET']
1377                 //              : false);
1378                 // }
1379
1380                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1381                         $postLimitTail .= ' FOR UPDATE';
1382                 }
1383
1384                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1385                         $postLimitTail .= ' LOCK IN SHARE MODE';
1386                 }
1387
1388                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1389                         $startOpts .= 'DISTINCT';
1390                 }
1391
1392                 # Various MySQL extensions
1393                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1394                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1395                 }
1396
1397                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1398                         $startOpts .= ' HIGH_PRIORITY';
1399                 }
1400
1401                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1402                         $startOpts .= ' SQL_BIG_RESULT';
1403                 }
1404
1405                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1406                         $startOpts .= ' SQL_BUFFER_RESULT';
1407                 }
1408
1409                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1410                         $startOpts .= ' SQL_SMALL_RESULT';
1411                 }
1412
1413                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1414                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1415                 }
1416
1417                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1418                         $startOpts .= ' SQL_CACHE';
1419                 }
1420
1421                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1422                         $startOpts .= ' SQL_NO_CACHE';
1423                 }
1424
1425                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1426                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1427                 } else {
1428                         $useIndex = '';
1429                 }
1430
1431                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1432         }
1433
1434         /**
1435          * Returns an optional GROUP BY with an optional HAVING
1436          *
1437          * @param array $options Associative array of options
1438          * @return string
1439          * @see DatabaseBase::select()
1440          * @since 1.21
1441          */
1442         public function makeGroupByWithHaving( $options ) {
1443                 $sql = '';
1444                 if ( isset( $options['GROUP BY'] ) ) {
1445                         $gb = is_array( $options['GROUP BY'] )
1446                                 ? implode( ',', $options['GROUP BY'] )
1447                                 : $options['GROUP BY'];
1448                         $sql .= ' GROUP BY ' . $gb;
1449                 }
1450                 if ( isset( $options['HAVING'] ) ) {
1451                         $having = is_array( $options['HAVING'] )
1452                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1453                                 : $options['HAVING'];
1454                         $sql .= ' HAVING ' . $having;
1455                 }
1456
1457                 return $sql;
1458         }
1459
1460         /**
1461          * Returns an optional ORDER BY
1462          *
1463          * @param array $options Associative array of options
1464          * @return string
1465          * @see DatabaseBase::select()
1466          * @since 1.21
1467          */
1468         public function makeOrderBy( $options ) {
1469                 if ( isset( $options['ORDER BY'] ) ) {
1470                         $ob = is_array( $options['ORDER BY'] )
1471                                 ? implode( ',', $options['ORDER BY'] )
1472                                 : $options['ORDER BY'];
1473
1474                         return ' ORDER BY ' . $ob;
1475                 }
1476
1477                 return '';
1478         }
1479
1480         /**
1481          * Execute a SELECT query constructed using the various parameters provided.
1482          * See below for full details of the parameters.
1483          *
1484          * @param string|array $table Table name
1485          * @param string|array $vars Field names
1486          * @param string|array $conds Conditions
1487          * @param string $fname Caller function name
1488          * @param array $options Query options
1489          * @param array $join_conds Join conditions
1490          *
1491          * @param string|array $table
1492          *
1493          * May be either an array of table names, or a single string holding a table
1494          * name. If an array is given, table aliases can be specified, for example:
1495          *
1496          *    array( 'a' => 'user' )
1497          *
1498          * This includes the user table in the query, with the alias "a" available
1499          * for use in field names (e.g. a.user_name).
1500          *
1501          * All of the table names given here are automatically run through
1502          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1503          * added, and various other table name mappings to be performed.
1504          *
1505          *
1506          * @param string|array $vars
1507          *
1508          * May be either a field name or an array of field names. The field names
1509          * can be complete fragments of SQL, for direct inclusion into the SELECT
1510          * query. If an array is given, field aliases can be specified, for example:
1511          *
1512          *   array( 'maxrev' => 'MAX(rev_id)' )
1513          *
1514          * This includes an expression with the alias "maxrev" in the query.
1515          *
1516          * If an expression is given, care must be taken to ensure that it is
1517          * DBMS-independent.
1518          *
1519          *
1520          * @param string|array $conds
1521          *
1522          * May be either a string containing a single condition, or an array of
1523          * conditions. If an array is given, the conditions constructed from each
1524          * element are combined with AND.
1525          *
1526          * Array elements may take one of two forms:
1527          *
1528          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1529          *   - Elements with a string key are interpreted as equality conditions,
1530          *     where the key is the field name.
1531          *     - If the value of such an array element is a scalar (such as a
1532          *       string), it will be treated as data and thus quoted appropriately.
1533          *       If it is null, an IS NULL clause will be added.
1534          *     - If the value is an array, an IN(...) clause will be constructed,
1535          *       such that the field name may match any of the elements in the
1536          *       array. The elements of the array will be quoted.
1537          *
1538          * Note that expressions are often DBMS-dependent in their syntax.
1539          * DBMS-independent wrappers are provided for constructing several types of
1540          * expression commonly used in condition queries. See:
1541          *    - DatabaseBase::buildLike()
1542          *    - DatabaseBase::conditional()
1543          *
1544          *
1545          * @param string|array $options
1546          *
1547          * Optional: Array of query options. Boolean options are specified by
1548          * including them in the array as a string value with a numeric key, for
1549          * example:
1550          *
1551          *    array( 'FOR UPDATE' )
1552          *
1553          * The supported options are:
1554          *
1555          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1556          *     with LIMIT can theoretically be used for paging through a result set,
1557          *     but this is discouraged in MediaWiki for performance reasons.
1558          *
1559          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1560          *     and then the first rows are taken until the limit is reached. LIMIT
1561          *     is applied to a result set after OFFSET.
1562          *
1563          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1564          *     changed until the next COMMIT.
1565          *
1566          *   - DISTINCT: Boolean: return only unique result rows.
1567          *
1568          *   - GROUP BY: May be either an SQL fragment string naming a field or
1569          *     expression to group by, or an array of such SQL fragments.
1570          *
1571          *   - HAVING: May be either an string containing a HAVING clause or an array of
1572          *     conditions building the HAVING clause. If an array is given, the conditions
1573          *     constructed from each element are combined with AND.
1574          *
1575          *   - ORDER BY: May be either an SQL fragment giving a field name or
1576          *     expression to order by, or an array of such SQL fragments.
1577          *
1578          *   - USE INDEX: This may be either a string giving the index name to use
1579          *     for the query, or an array. If it is an associative array, each key
1580          *     gives the table name (or alias), each value gives the index name to
1581          *     use for that table. All strings are SQL fragments and so should be
1582          *     validated by the caller.
1583          *
1584          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1585          *     instead of SELECT.
1586          *
1587          * And also the following boolean MySQL extensions, see the MySQL manual
1588          * for documentation:
1589          *
1590          *    - LOCK IN SHARE MODE
1591          *    - STRAIGHT_JOIN
1592          *    - HIGH_PRIORITY
1593          *    - SQL_BIG_RESULT
1594          *    - SQL_BUFFER_RESULT
1595          *    - SQL_SMALL_RESULT
1596          *    - SQL_CALC_FOUND_ROWS
1597          *    - SQL_CACHE
1598          *    - SQL_NO_CACHE
1599          *
1600          *
1601          * @param string|array $join_conds
1602          *
1603          * Optional associative array of table-specific join conditions. In the
1604          * most common case, this is unnecessary, since the join condition can be
1605          * in $conds. However, it is useful for doing a LEFT JOIN.
1606          *
1607          * The key of the array contains the table name or alias. The value is an
1608          * array with two elements, numbered 0 and 1. The first gives the type of
1609          * join, the second is an SQL fragment giving the join condition for that
1610          * table. For example:
1611          *
1612          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1613          *
1614          * @return ResultWrapper|bool If the query returned no rows, a ResultWrapper
1615          *   with no rows in it will be returned. If there was a query error, a
1616          *   DBQueryError exception will be thrown, except if the "ignore errors"
1617          *   option was set, in which case false will be returned.
1618          */
1619         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1620                 $options = array(), $join_conds = array() ) {
1621                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1622
1623                 return $this->query( $sql, $fname );
1624         }
1625
1626         /**
1627          * The equivalent of DatabaseBase::select() except that the constructed SQL
1628          * is returned, instead of being immediately executed. This can be useful for
1629          * doing UNION queries, where the SQL text of each query is needed. In general,
1630          * however, callers outside of Database classes should just use select().
1631          *
1632          * @param string|array $table Table name
1633          * @param string|array $vars Field names
1634          * @param string|array $conds Conditions
1635          * @param string $fname Caller function name
1636          * @param string|array $options Query options
1637          * @param string|array $join_conds Join conditions
1638          *
1639          * @return string SQL query string.
1640          * @see DatabaseBase::select()
1641          */
1642         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1643                 $options = array(), $join_conds = array()
1644         ) {
1645                 if ( is_array( $vars ) ) {
1646                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1647                 }
1648
1649                 $options = (array)$options;
1650                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1651                         ? $options['USE INDEX']
1652                         : array();
1653
1654                 if ( is_array( $table ) ) {
1655                         $from = ' FROM ' .
1656                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1657                 } elseif ( $table != '' ) {
1658                         if ( $table[0] == ' ' ) {
1659                                 $from = ' FROM ' . $table;
1660                         } else {
1661                                 $from = ' FROM ' .
1662                                         $this->tableNamesWithUseIndexOrJOIN( array( $table ), $useIndexes, array() );
1663                         }
1664                 } else {
1665                         $from = '';
1666                 }
1667
1668                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1669                         $this->makeSelectOptions( $options );
1670
1671                 if ( !empty( $conds ) ) {
1672                         if ( is_array( $conds ) ) {
1673                                 $conds = $this->makeList( $conds, LIST_AND );
1674                         }
1675                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1676                 } else {
1677                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1678                 }
1679
1680                 if ( isset( $options['LIMIT'] ) ) {
1681                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1682                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1683                 }
1684                 $sql = "$sql $postLimitTail";
1685
1686                 if ( isset( $options['EXPLAIN'] ) ) {
1687                         $sql = 'EXPLAIN ' . $sql;
1688                 }
1689
1690                 return $sql;
1691         }
1692
1693         /**
1694          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1695          * that a single row object is returned. If the query returns no rows,
1696          * false is returned.
1697          *
1698          * @param string|array $table Table name
1699          * @param string|array $vars Field names
1700          * @param array $conds Conditions
1701          * @param string $fname Caller function name
1702          * @param string|array $options Query options
1703          * @param array|string $join_conds Join conditions
1704          *
1705          * @return stdClass|bool
1706          */
1707         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1708                 $options = array(), $join_conds = array()
1709         ) {
1710                 $options = (array)$options;
1711                 $options['LIMIT'] = 1;
1712                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1713
1714                 if ( $res === false ) {
1715                         return false;
1716                 }
1717
1718                 if ( !$this->numRows( $res ) ) {
1719                         return false;
1720                 }
1721
1722                 $obj = $this->fetchObject( $res );
1723
1724                 return $obj;
1725         }
1726
1727         /**
1728          * Estimate rows in dataset.
1729          *
1730          * MySQL allows you to estimate the number of rows that would be returned
1731          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1732          * index cardinality statistics, and is notoriously inaccurate, especially
1733          * when large numbers of rows have recently been added or deleted.
1734          *
1735          * For DBMSs that don't support fast result size estimation, this function
1736          * will actually perform the SELECT COUNT(*).
1737          *
1738          * Takes the same arguments as DatabaseBase::select().
1739          *
1740          * @param string $table Table name
1741          * @param string $vars Unused
1742          * @param array|string $conds Filters on the table
1743          * @param string $fname Function name for profiling
1744          * @param array $options Options for select
1745          * @return int Row count
1746          */
1747         public function estimateRowCount( $table, $vars = '*', $conds = '',
1748                 $fname = __METHOD__, $options = array()
1749         ) {
1750                 $rows = 0;
1751                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1752
1753                 if ( $res ) {
1754                         $row = $this->fetchRow( $res );
1755                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1756                 }
1757
1758                 return $rows;
1759         }
1760
1761         /**
1762          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1763          * It's only slightly flawed. Don't use for anything important.
1764          *
1765          * @param string $sql A SQL Query
1766          *
1767          * @return string
1768          */
1769         static function generalizeSQL( $sql ) {
1770                 # This does the same as the regexp below would do, but in such a way
1771                 # as to avoid crashing php on some large strings.
1772                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1773
1774                 $sql = str_replace( "\\\\", '', $sql );
1775                 $sql = str_replace( "\\'", '', $sql );
1776                 $sql = str_replace( "\\\"", '', $sql );
1777                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1778                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1779
1780                 # All newlines, tabs, etc replaced by single space
1781                 $sql = preg_replace( '/\s+/', ' ', $sql );
1782
1783                 # All numbers => N,
1784                 # except the ones surrounded by characters, e.g. l10n
1785                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1786                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1787
1788                 return $sql;
1789         }
1790
1791         /**
1792          * Determines whether a field exists in a table
1793          *
1794          * @param string $table Table name
1795          * @param string $field Filed to check on that table
1796          * @param string $fname Calling function name (optional)
1797          * @return bool Whether $table has filed $field
1798          */
1799         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1800                 $info = $this->fieldInfo( $table, $field );
1801
1802                 return (bool)$info;
1803         }
1804
1805         /**
1806          * Determines whether an index exists
1807          * Usually throws a DBQueryError on failure
1808          * If errors are explicitly ignored, returns NULL on failure
1809          *
1810          * @param string $table
1811          * @param string $index
1812          * @param string $fname
1813          * @return bool|null
1814          */
1815         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1816                 if ( !$this->tableExists( $table ) ) {
1817                         return null;
1818                 }
1819
1820                 $info = $this->indexInfo( $table, $index, $fname );
1821                 if ( is_null( $info ) ) {
1822                         return null;
1823                 } else {
1824                         return $info !== false;
1825                 }
1826         }
1827
1828         /**
1829          * Query whether a given table exists
1830          *
1831          * @param string $table
1832          * @param string $fname
1833          * @return bool
1834          */
1835         public function tableExists( $table, $fname = __METHOD__ ) {
1836                 $table = $this->tableName( $table );
1837                 $old = $this->ignoreErrors( true );
1838                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1839                 $this->ignoreErrors( $old );
1840
1841                 return (bool)$res;
1842         }
1843
1844         /**
1845          * Determines if a given index is unique
1846          *
1847          * @param string $table
1848          * @param string $index
1849          *
1850          * @return bool
1851          */
1852         public function indexUnique( $table, $index ) {
1853                 $indexInfo = $this->indexInfo( $table, $index );
1854
1855                 if ( !$indexInfo ) {
1856                         return null;
1857                 }
1858
1859                 return !$indexInfo[0]->Non_unique;
1860         }
1861
1862         /**
1863          * Helper for DatabaseBase::insert().
1864          *
1865          * @param array $options
1866          * @return string
1867          */
1868         protected function makeInsertOptions( $options ) {
1869                 return implode( ' ', $options );
1870         }
1871
1872         /**
1873          * INSERT wrapper, inserts an array into a table.
1874          *
1875          * $a may be either:
1876          *
1877          *   - A single associative array. The array keys are the field names, and
1878          *     the values are the values to insert. The values are treated as data
1879          *     and will be quoted appropriately. If NULL is inserted, this will be
1880          *     converted to a database NULL.
1881          *   - An array with numeric keys, holding a list of associative arrays.
1882          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1883          *     each subarray must be identical to each other, and in the same order.
1884          *
1885          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1886          * returns success.
1887          *
1888          * $options is an array of options, with boolean options encoded as values
1889          * with numeric keys, in the same style as $options in
1890          * DatabaseBase::select(). Supported options are:
1891          *
1892          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1893          *     any rows which cause duplicate key errors are not inserted. It's
1894          *     possible to determine how many rows were successfully inserted using
1895          *     DatabaseBase::affectedRows().
1896          *
1897          * @param string $table Table name. This will be passed through
1898          *   DatabaseBase::tableName().
1899          * @param array $a Array of rows to insert
1900          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1901          * @param array $options of options
1902          *
1903          * @return bool
1904          */
1905         public function insert( $table, $a, $fname = __METHOD__, $options = array() ) {
1906                 # No rows to insert, easy just return now
1907                 if ( !count( $a ) ) {
1908                         return true;
1909                 }
1910
1911                 $table = $this->tableName( $table );
1912
1913                 if ( !is_array( $options ) ) {
1914                         $options = array( $options );
1915                 }
1916
1917                 $fh = null;
1918                 if ( isset( $options['fileHandle'] ) ) {
1919                         $fh = $options['fileHandle'];
1920                 }
1921                 $options = $this->makeInsertOptions( $options );
1922
1923                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1924                         $multi = true;
1925                         $keys = array_keys( $a[0] );
1926                 } else {
1927                         $multi = false;
1928                         $keys = array_keys( $a );
1929                 }
1930
1931                 $sql = 'INSERT ' . $options .
1932                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1933
1934                 if ( $multi ) {
1935                         $first = true;
1936                         foreach ( $a as $row ) {
1937                                 if ( $first ) {
1938                                         $first = false;
1939                                 } else {
1940                                         $sql .= ',';
1941                                 }
1942                                 $sql .= '(' . $this->makeList( $row ) . ')';
1943                         }
1944                 } else {
1945                         $sql .= '(' . $this->makeList( $a ) . ')';
1946                 }
1947
1948                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1949                         return false;
1950                 } elseif ( $fh !== null ) {
1951                         return true;
1952                 }
1953
1954                 return (bool)$this->query( $sql, $fname );
1955         }
1956
1957         /**
1958          * Make UPDATE options array for DatabaseBase::makeUpdateOptions
1959          *
1960          * @param array $options
1961          * @return array
1962          */
1963         protected function makeUpdateOptionsArray( $options ) {
1964                 if ( !is_array( $options ) ) {
1965                         $options = array( $options );
1966                 }
1967
1968                 $opts = array();
1969
1970                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1971                         $opts[] = $this->lowPriorityOption();
1972                 }
1973
1974                 if ( in_array( 'IGNORE', $options ) ) {
1975                         $opts[] = 'IGNORE';
1976                 }
1977
1978                 return $opts;
1979         }
1980
1981         /**
1982          * Make UPDATE options for the DatabaseBase::update function
1983          *
1984          * @param array $options The options passed to DatabaseBase::update
1985          * @return string
1986          */
1987         protected function makeUpdateOptions( $options ) {
1988                 $opts = $this->makeUpdateOptionsArray( $options );
1989
1990                 return implode( ' ', $opts );
1991         }
1992
1993         /**
1994          * UPDATE wrapper. Takes a condition array and a SET array.
1995          *
1996          * @param string $table Name of the table to UPDATE. This will be passed through
1997          *   DatabaseBase::tableName().
1998          * @param array $values An array of values to SET. For each array element,
1999          *   the key gives the field name, and the value gives the data to set
2000          *   that field to. The data will be quoted by DatabaseBase::addQuotes().
2001          * @param array $conds An array of conditions (WHERE). See
2002          *   DatabaseBase::select() for the details of the format of condition
2003          *   arrays. Use '*' to update all rows.
2004          * @param string $fname The function name of the caller (from __METHOD__),
2005          *   for logging and profiling.
2006          * @param array $options An array of UPDATE options, can be:
2007          *   - IGNORE: Ignore unique key conflicts
2008          *   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
2009          * @return bool
2010          */
2011         function update( $table, $values, $conds, $fname = __METHOD__, $options = array() ) {
2012                 $table = $this->tableName( $table );
2013                 $opts = $this->makeUpdateOptions( $options );
2014                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
2015
2016                 if ( $conds !== array() && $conds !== '*' ) {
2017                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
2018                 }
2019
2020                 return $this->query( $sql, $fname );
2021         }
2022
2023         /**
2024          * Makes an encoded list of strings from an array
2025          *
2026          * @param array $a Containing the data
2027          * @param int $mode Constant
2028          *    - LIST_COMMA: Comma separated, no field names
2029          *    - LIST_AND:   ANDed WHERE clause (without the WHERE). See the
2030          *      documentation for $conds in DatabaseBase::select().
2031          *    - LIST_OR:    ORed WHERE clause (without the WHERE)
2032          *    - LIST_SET:   Comma separated with field names, like a SET clause
2033          *    - LIST_NAMES: Comma separated field names
2034          * @throws MWException|DBUnexpectedError
2035          * @return string
2036          */
2037         public function makeList( $a, $mode = LIST_COMMA ) {
2038                 if ( !is_array( $a ) ) {
2039                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
2040                 }
2041
2042                 $first = true;
2043                 $list = '';
2044
2045                 foreach ( $a as $field => $value ) {
2046                         if ( !$first ) {
2047                                 if ( $mode == LIST_AND ) {
2048                                         $list .= ' AND ';
2049                                 } elseif ( $mode == LIST_OR ) {
2050                                         $list .= ' OR ';
2051                                 } else {
2052                                         $list .= ',';
2053                                 }
2054                         } else {
2055                                 $first = false;
2056                         }
2057
2058                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
2059                                 $list .= "($value)";
2060                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
2061                                 $list .= "$value";
2062                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
2063                                 if ( count( $value ) == 0 ) {
2064                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
2065                                 } elseif ( count( $value ) == 1 ) {
2066                                         // Special-case single values, as IN isn't terribly efficient
2067                                         // Don't necessarily assume the single key is 0; we don't
2068                                         // enforce linear numeric ordering on other arrays here.
2069                                         $value = array_values( $value );
2070                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
2071                                 } else {
2072                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
2073                                 }
2074                         } elseif ( $value === null ) {
2075                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
2076                                         $list .= "$field IS ";
2077                                 } elseif ( $mode == LIST_SET ) {
2078                                         $list .= "$field = ";
2079                                 }
2080                                 $list .= 'NULL';
2081                         } else {
2082                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
2083                                         $list .= "$field = ";
2084                                 }
2085                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
2086                         }
2087                 }
2088
2089                 return $list;
2090         }
2091
2092         /**
2093          * Build a partial where clause from a 2-d array such as used for LinkBatch.
2094          * The keys on each level may be either integers or strings.
2095          *
2096          * @param array $data organized as 2-d
2097          *    array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
2098          * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
2099          * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
2100          * @return string|bool string SQL fragment, or false if no items in array.
2101          */
2102         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2103                 $conds = array();
2104
2105                 foreach ( $data as $base => $sub ) {
2106                         if ( count( $sub ) ) {
2107                                 $conds[] = $this->makeList(
2108                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
2109                                         LIST_AND );
2110                         }
2111                 }
2112
2113                 if ( $conds ) {
2114                         return $this->makeList( $conds, LIST_OR );
2115                 } else {
2116                         // Nothing to search for...
2117                         return false;
2118                 }
2119         }
2120
2121         /**
2122          * Return aggregated value alias
2123          *
2124          * @param array $valuedata
2125          * @param string $valuename
2126          *
2127          * @return string
2128          */
2129         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2130                 return $valuename;
2131         }
2132
2133         /**
2134          * @param string $field
2135          * @return string
2136          */
2137         public function bitNot( $field ) {
2138                 return "(~$field)";
2139         }
2140
2141         /**
2142          * @param string $fieldLeft
2143          * @param string $fieldRight
2144          * @return string
2145          */
2146         public function bitAnd( $fieldLeft, $fieldRight ) {
2147                 return "($fieldLeft & $fieldRight)";
2148         }
2149
2150         /**
2151          * @param string $fieldLeft
2152          * @param string $fieldRight
2153          * @return string
2154          */
2155         public function bitOr( $fieldLeft, $fieldRight ) {
2156                 return "($fieldLeft | $fieldRight)";
2157         }
2158
2159         /**
2160          * Build a concatenation list to feed into a SQL query
2161          * @param array $stringList List of raw SQL expressions; caller is
2162          *   responsible for any quoting
2163          * @return string
2164          */
2165         public function buildConcat( $stringList ) {
2166                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2167         }
2168
2169         /**
2170          * Build a GROUP_CONCAT or equivalent statement for a query.
2171          *
2172          * This is useful for combining a field for several rows into a single string.
2173          * NULL values will not appear in the output, duplicated values will appear,
2174          * and the resulting delimiter-separated values have no defined sort order.
2175          * Code using the results may need to use the PHP unique() or sort() methods.
2176          *
2177          * @param string $delim Glue to bind the results together
2178          * @param string|array $table Table name
2179          * @param string $field Field name
2180          * @param string|array $conds Conditions
2181          * @param string|array $join_conds Join conditions
2182          * @return string SQL text
2183          * @since 1.23
2184          */
2185         public function buildGroupConcatField(
2186                 $delim, $table, $field, $conds = '', $join_conds = array()
2187         ) {
2188                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
2189
2190                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, array(), $join_conds ) . ')';
2191         }
2192
2193         /**
2194          * Change the current database
2195          *
2196          * @todo Explain what exactly will fail if this is not overridden.
2197          *
2198          * @param string $db
2199          *
2200          * @return bool Success or failure
2201          */
2202         public function selectDB( $db ) {
2203                 # Stub. Shouldn't cause serious problems if it's not overridden, but
2204                 # if your database engine supports a concept similar to MySQL's
2205                 # databases you may as well.
2206                 $this->mDBname = $db;
2207
2208                 return true;
2209         }
2210
2211         /**
2212          * Get the current DB name
2213          * @return string
2214          */
2215         public function getDBname() {
2216                 return $this->mDBname;
2217         }
2218
2219         /**
2220          * Get the server hostname or IP address
2221          * @return string
2222          */
2223         public function getServer() {
2224                 return $this->mServer;
2225         }
2226
2227         /**
2228          * Format a table name ready for use in constructing an SQL query
2229          *
2230          * This does two important things: it quotes the table names to clean them up,
2231          * and it adds a table prefix if only given a table name with no quotes.
2232          *
2233          * All functions of this object which require a table name call this function
2234          * themselves. Pass the canonical name to such functions. This is only needed
2235          * when calling query() directly.
2236          *
2237          * @param string $name Database table name
2238          * @param string $format One of:
2239          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2240          *            so that it can be used in a query.
2241          *   raw - Do not add identifier quotes to the table name
2242          * @return string Full database name
2243          */
2244         public function tableName( $name, $format = 'quoted' ) {
2245                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables, $wgSharedSchema;
2246                 # Skip the entire process when we have a string quoted on both ends.
2247                 # Note that we check the end so that we will still quote any use of
2248                 # use of `database`.table. But won't break things if someone wants
2249                 # to query a database table with a dot in the name.
2250                 if ( $this->isQuotedIdentifier( $name ) ) {
2251                         return $name;
2252                 }
2253
2254                 # Lets test for any bits of text that should never show up in a table
2255                 # name. Basically anything like JOIN or ON which are actually part of
2256                 # SQL queries, but may end up inside of the table value to combine
2257                 # sql. Such as how the API is doing.
2258                 # Note that we use a whitespace test rather than a \b test to avoid
2259                 # any remote case where a word like on may be inside of a table name
2260                 # surrounded by symbols which may be considered word breaks.
2261                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2262                         return $name;
2263                 }
2264
2265                 # Split database and table into proper variables.
2266                 # We reverse the explode so that database.table and table both output
2267                 # the correct table.
2268                 $dbDetails = explode( '.', $name, 2 );
2269                 if ( count( $dbDetails ) == 3 ) {
2270                         list( $database, $schema, $table ) = $dbDetails;
2271                         # We don't want any prefix added in this case
2272                         $prefix = '';
2273                 } elseif ( count( $dbDetails ) == 2 ) {
2274                         list( $database, $table ) = $dbDetails;
2275                         # We don't want any prefix added in this case
2276                         # In dbs that support it, $database may actually be the schema
2277                         # but that doesn't affect any of the functionality here
2278                         $prefix = '';
2279                         $schema = null;
2280                 } else {
2281                         list( $table ) = $dbDetails;
2282                         if ( $wgSharedDB !== null # We have a shared database
2283                                 && $this->mForeign == false # We're not working on a foreign database
2284                                 && !$this->isQuotedIdentifier( $table ) # Prevent shared tables listing '`table`'
2285                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2286                         ) {
2287                                 $database = $wgSharedDB;
2288                                 $schema = $wgSharedSchema === null ? $this->mSchema : $wgSharedSchema;
2289                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2290                         } else {
2291                                 $database = null;
2292                                 $schema = $this->mSchema; # Default schema
2293                                 $prefix = $this->mTablePrefix; # Default prefix
2294                         }
2295                 }
2296
2297                 # Quote $table and apply the prefix if not quoted.
2298                 # $tableName might be empty if this is called from Database::replaceVars()
2299                 $tableName = "{$prefix}{$table}";
2300                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) && $tableName !== '' ) {
2301                         $tableName = $this->addIdentifierQuotes( $tableName );
2302                 }
2303
2304                 # Quote $schema and merge it with the table name if needed
2305                 if ( $schema !== null ) {
2306                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $schema ) ) {
2307                                 $schema = $this->addIdentifierQuotes( $schema );
2308                         }
2309                         $tableName = $schema . '.' . $tableName;
2310                 }
2311
2312                 # Quote $database and merge it with the table name if needed
2313                 if ( $database !== null ) {
2314                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2315                                 $database = $this->addIdentifierQuotes( $database );
2316                         }
2317                         $tableName = $database . '.' . $tableName;
2318                 }
2319
2320                 return $tableName;
2321         }
2322
2323         /**
2324          * Fetch a number of table names into an array
2325          * This is handy when you need to construct SQL for joins
2326          *
2327          * Example:
2328          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2329          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2330          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2331          *
2332          * @return array
2333          */
2334         public function tableNames() {
2335                 $inArray = func_get_args();
2336                 $retVal = array();
2337
2338                 foreach ( $inArray as $name ) {
2339                         $retVal[$name] = $this->tableName( $name );
2340                 }
2341
2342                 return $retVal;
2343         }
2344
2345         /**
2346          * Fetch a number of table names into an zero-indexed numerical array
2347          * This is handy when you need to construct SQL for joins
2348          *
2349          * Example:
2350          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2351          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2352          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2353          *
2354          * @return array
2355          */
2356         public function tableNamesN() {
2357                 $inArray = func_get_args();
2358                 $retVal = array();
2359
2360                 foreach ( $inArray as $name ) {
2361                         $retVal[] = $this->tableName( $name );
2362                 }
2363
2364                 return $retVal;
2365         }
2366
2367         /**
2368          * Get an aliased table name
2369          * e.g. tableName AS newTableName
2370          *
2371          * @param string $name Table name, see tableName()
2372          * @param string|bool $alias Alias (optional)
2373          * @return string SQL name for aliased table. Will not alias a table to its own name
2374          */
2375         public function tableNameWithAlias( $name, $alias = false ) {
2376                 if ( !$alias || $alias == $name ) {
2377                         return $this->tableName( $name );
2378                 } else {
2379                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2380                 }
2381         }
2382
2383         /**
2384          * Gets an array of aliased table names
2385          *
2386          * @param array $tables array( [alias] => table )
2387          * @return string[] See tableNameWithAlias()
2388          */
2389         public function tableNamesWithAlias( $tables ) {
2390                 $retval = array();
2391                 foreach ( $tables as $alias => $table ) {
2392                         if ( is_numeric( $alias ) ) {
2393                                 $alias = $table;
2394                         }
2395                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2396                 }
2397
2398                 return $retval;
2399         }
2400
2401         /**
2402          * Get an aliased field name
2403          * e.g. fieldName AS newFieldName
2404          *
2405          * @param string $name Field name
2406          * @param string|bool $alias Alias (optional)
2407          * @return string SQL name for aliased field. Will not alias a field to its own name
2408          */
2409         public function fieldNameWithAlias( $name, $alias = false ) {
2410                 if ( !$alias || (string)$alias === (string)$name ) {
2411                         return $name;
2412                 } else {
2413                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2414                 }
2415         }
2416
2417         /**
2418          * Gets an array of aliased field names
2419          *
2420          * @param array $fields array( [alias] => field )
2421          * @return string[] See fieldNameWithAlias()
2422          */
2423         public function fieldNamesWithAlias( $fields ) {
2424                 $retval = array();
2425                 foreach ( $fields as $alias => $field ) {
2426                         if ( is_numeric( $alias ) ) {
2427                                 $alias = $field;
2428                         }
2429                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2430                 }
2431
2432                 return $retval;
2433         }
2434
2435         /**
2436          * Get the aliased table name clause for a FROM clause
2437          * which might have a JOIN and/or USE INDEX clause
2438          *
2439          * @param array $tables ( [alias] => table )
2440          * @param array $use_index Same as for select()
2441          * @param array $join_conds Same as for select()
2442          * @return string
2443          */
2444         protected function tableNamesWithUseIndexOrJOIN(
2445                 $tables, $use_index = array(), $join_conds = array()
2446         ) {
2447                 $ret = array();
2448                 $retJOIN = array();
2449                 $use_index = (array)$use_index;
2450                 $join_conds = (array)$join_conds;
2451
2452                 foreach ( $tables as $alias => $table ) {
2453                         if ( !is_string( $alias ) ) {
2454                                 // No alias? Set it equal to the table name
2455                                 $alias = $table;
2456                         }
2457                         // Is there a JOIN clause for this table?
2458                         if ( isset( $join_conds[$alias] ) ) {
2459                                 list( $joinType, $conds ) = $join_conds[$alias];
2460                                 $tableClause = $joinType;
2461                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2462                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2463                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2464                                         if ( $use != '' ) {
2465                                                 $tableClause .= ' ' . $use;
2466                                         }
2467                                 }
2468                                 $on = $this->makeList( (array)$conds, LIST_AND );
2469                                 if ( $on != '' ) {
2470                                         $tableClause .= ' ON (' . $on . ')';
2471                                 }
2472
2473                                 $retJOIN[] = $tableClause;
2474                         } elseif ( isset( $use_index[$alias] ) ) {
2475                                 // Is there an INDEX clause for this table?
2476                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2477                                 $tableClause .= ' ' . $this->useIndexClause(
2478                                         implode( ',', (array)$use_index[$alias] )
2479                                 );
2480
2481                                 $ret[] = $tableClause;
2482                         } else {
2483                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2484
2485                                 $ret[] = $tableClause;
2486                         }
2487                 }
2488
2489                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2490                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2491                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2492
2493                 // Compile our final table clause
2494                 return implode( ' ', array( $implicitJoins, $explicitJoins ) );
2495         }
2496
2497         /**
2498          * Get the name of an index in a given table
2499          *
2500          * @param string $index
2501          * @return string
2502          */
2503         protected function indexName( $index ) {
2504                 // Backwards-compatibility hack
2505                 $renamed = array(
2506                         'ar_usertext_timestamp' => 'usertext_timestamp',
2507                         'un_user_id' => 'user_id',
2508                         'un_user_ip' => 'user_ip',
2509                 );
2510
2511                 if ( isset( $renamed[$index] ) ) {
2512                         return $renamed[$index];
2513                 } else {
2514                         return $index;
2515                 }
2516         }
2517
2518         /**
2519          * Adds quotes and backslashes.
2520          *
2521          * @param string $s
2522          * @return string
2523          */
2524         public function addQuotes( $s ) {
2525                 if ( $s === null ) {
2526                         return 'NULL';
2527                 } else {
2528                         # This will also quote numeric values. This should be harmless,
2529                         # and protects against weird problems that occur when they really
2530                         # _are_ strings such as article titles and string->number->string
2531                         # conversion is not 1:1.
2532                         return "'" . $this->strencode( $s ) . "'";
2533                 }
2534         }
2535
2536         /**
2537          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2538          * MySQL uses `backticks` while basically everything else uses double quotes.
2539          * Since MySQL is the odd one out here the double quotes are our generic
2540          * and we implement backticks in DatabaseMysql.
2541          *
2542          * @param string $s
2543          * @return string
2544          */
2545         public function addIdentifierQuotes( $s ) {
2546                 return '"' . str_replace( '"', '""', $s ) . '"';
2547         }
2548
2549         /**
2550          * Returns if the given identifier looks quoted or not according to
2551          * the database convention for quoting identifiers .
2552          *
2553          * @param string $name
2554          * @return bool
2555          */
2556         public function isQuotedIdentifier( $name ) {
2557                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2558         }
2559
2560         /**
2561          * @param string $s
2562          * @return string
2563          */
2564         protected function escapeLikeInternal( $s ) {
2565                 return addcslashes( $s, '\%_' );
2566         }
2567
2568         /**
2569          * LIKE statement wrapper, receives a variable-length argument list with
2570          * parts of pattern to match containing either string literals that will be
2571          * escaped or tokens returned by anyChar() or anyString(). Alternatively,
2572          * the function could be provided with an array of aforementioned
2573          * parameters.
2574          *
2575          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
2576          * a LIKE clause that searches for subpages of 'My page title'.
2577          * Alternatively:
2578          *   $pattern = array( 'My_page_title/', $dbr->anyString() );
2579          *   $query .= $dbr->buildLike( $pattern );
2580          *
2581          * @since 1.16
2582          * @return string Fully built LIKE statement
2583          */
2584         public function buildLike() {
2585                 $params = func_get_args();
2586
2587                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2588                         $params = $params[0];
2589                 }
2590
2591                 $s = '';
2592
2593                 foreach ( $params as $value ) {
2594                         if ( $value instanceof LikeMatch ) {
2595                                 $s .= $value->toString();
2596                         } else {
2597                                 $s .= $this->escapeLikeInternal( $value );
2598                         }
2599                 }
2600
2601                 return " LIKE {$this->addQuotes( $s )} ";
2602         }
2603
2604         /**
2605          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2606          *
2607          * @return LikeMatch
2608          */
2609         public function anyChar() {
2610                 return new LikeMatch( '_' );
2611         }
2612
2613         /**
2614          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2615          *
2616          * @return LikeMatch
2617          */
2618         public function anyString() {
2619                 return new LikeMatch( '%' );
2620         }
2621
2622         /**
2623          * Returns an appropriately quoted sequence value for inserting a new row.
2624          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2625          * subclass will return an integer, and save the value for insertId()
2626          *
2627          * Any implementation of this function should *not* involve reusing
2628          * sequence numbers created for rolled-back transactions.
2629          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2630          * @param string $seqName
2631          * @return null|int
2632          */
2633         public function nextSequenceValue( $seqName ) {
2634                 return null;
2635         }
2636
2637         /**
2638          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2639          * is only needed because a) MySQL must be as efficient as possible due to
2640          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2641          * which index to pick. Anyway, other databases might have different
2642          * indexes on a given table. So don't bother overriding this unless you're
2643          * MySQL.
2644          * @param string $index
2645          * @return string
2646          */
2647         public function useIndexClause( $index ) {
2648                 return '';
2649         }
2650
2651         /**
2652          * REPLACE query wrapper.
2653          *
2654          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2655          * except that when there is a duplicate key error, the old row is deleted
2656          * and the new row is inserted in its place.
2657          *
2658          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2659          * perform the delete, we need to know what the unique indexes are so that
2660          * we know how to find the conflicting rows.
2661          *
2662          * It may be more efficient to leave off unique indexes which are unlikely
2663          * to collide. However if you do this, you run the risk of encountering
2664          * errors which wouldn't have occurred in MySQL.
2665          *
2666          * @param string $table The table to replace the row(s) in.
2667          * @param array $uniqueIndexes Is an array of indexes. Each element may be either
2668          *    a field name or an array of field names
2669          * @param array $rows Can be either a single row to insert, or multiple rows,
2670          *    in the same format as for DatabaseBase::insert()
2671          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2672          */
2673         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2674                 $quotedTable = $this->tableName( $table );
2675
2676                 if ( count( $rows ) == 0 ) {
2677                         return;
2678                 }
2679
2680                 # Single row case
2681                 if ( !is_array( reset( $rows ) ) ) {
2682                         $rows = array( $rows );
2683                 }
2684
2685                 foreach ( $rows as $row ) {
2686                         # Delete rows which collide
2687                         if ( $uniqueIndexes ) {
2688                                 $sql = "DELETE FROM $quotedTable WHERE ";
2689                                 $first = true;
2690                                 foreach ( $uniqueIndexes as $index ) {
2691                                         if ( $first ) {
2692                                                 $first = false;
2693                                                 $sql .= '( ';
2694                                         } else {
2695                                                 $sql .= ' ) OR ( ';
2696                                         }
2697                                         if ( is_array( $index ) ) {
2698                                                 $first2 = true;
2699                                                 foreach ( $index as $col ) {
2700                                                         if ( $first2 ) {
2701                                                                 $first2 = false;
2702                                                         } else {
2703                                                                 $sql .= ' AND ';
2704                                                         }
2705                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2706                                                 }
2707                                         } else {
2708                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2709                                         }
2710                                 }
2711                                 $sql .= ' )';
2712                                 $this->query( $sql, $fname );
2713                         }
2714
2715                         # Now insert the row
2716                         $this->insert( $table, $row, $fname );
2717                 }
2718         }
2719
2720         /**
2721          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2722          * statement.
2723          *
2724          * @param string $table Table name
2725          * @param array|string $rows Row(s) to insert
2726          * @param string $fname Caller function name
2727          *
2728          * @return ResultWrapper
2729          */
2730         protected function nativeReplace( $table, $rows, $fname ) {
2731                 $table = $this->tableName( $table );
2732
2733                 # Single row case
2734                 if ( !is_array( reset( $rows ) ) ) {
2735                         $rows = array( $rows );
2736                 }
2737
2738                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2739                 $first = true;
2740
2741                 foreach ( $rows as $row ) {
2742                         if ( $first ) {
2743                                 $first = false;
2744                         } else {
2745                                 $sql .= ',';
2746                         }
2747
2748                         $sql .= '(' . $this->makeList( $row ) . ')';
2749                 }
2750
2751                 return $this->query( $sql, $fname );
2752         }
2753
2754         /**
2755          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
2756          *
2757          * This updates any conflicting rows (according to the unique indexes) using
2758          * the provided SET clause and inserts any remaining (non-conflicted) rows.
2759          *
2760          * $rows may be either:
2761          *   - A single associative array. The array keys are the field names, and
2762          *     the values are the values to insert. The values are treated as data
2763          *     and will be quoted appropriately. If NULL is inserted, this will be
2764          *     converted to a database NULL.
2765          *   - An array with numeric keys, holding a list of associative arrays.
2766          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
2767          *     each subarray must be identical to each other, and in the same order.
2768          *
2769          * It may be more efficient to leave off unique indexes which are unlikely
2770          * to collide. However if you do this, you run the risk of encountering
2771          * errors which wouldn't have occurred in MySQL.
2772          *
2773          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
2774          * returns success.
2775          *
2776          * @since 1.22
2777          *
2778          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
2779          * @param array $rows A single row or list of rows to insert
2780          * @param array $uniqueIndexes List of single field names or field name tuples
2781          * @param array $set An array of values to SET. For each array element, the
2782          *   key gives the field name, and the value gives the data to set that
2783          *   field to. The data will be quoted by DatabaseBase::addQuotes().
2784          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2785          * @throws Exception
2786          * @return bool
2787          */
2788         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2789                 $fname = __METHOD__
2790         ) {
2791                 if ( !count( $rows ) ) {
2792                         return true; // nothing to do
2793                 }
2794
2795                 if ( !is_array( reset( $rows ) ) ) {
2796                         $rows = array( $rows );
2797                 }
2798
2799                 if ( count( $uniqueIndexes ) ) {
2800                         $clauses = array(); // list WHERE clauses that each identify a single row
2801                         foreach ( $rows as $row ) {
2802                                 foreach ( $uniqueIndexes as $index ) {
2803                                         $index = is_array( $index ) ? $index : array( $index ); // columns
2804                                         $rowKey = array(); // unique key to this row
2805                                         foreach ( $index as $column ) {
2806                                                 $rowKey[$column] = $row[$column];
2807                                         }
2808                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2809                                 }
2810                         }
2811                         $where = array( $this->makeList( $clauses, LIST_OR ) );
2812                 } else {
2813                         $where = false;
2814                 }
2815
2816                 $useTrx = !$this->mTrxLevel;
2817                 if ( $useTrx ) {
2818                         $this->begin( $fname );
2819                 }
2820                 try {
2821                         # Update any existing conflicting row(s)
2822                         if ( $where !== false ) {
2823                                 $ok = $this->update( $table, $set, $where, $fname );
2824                         } else {
2825                                 $ok = true;
2826                         }
2827                         # Now insert any non-conflicting row(s)
2828                         $ok = $this->insert( $table, $rows, $fname, array( 'IGNORE' ) ) && $ok;
2829                 } catch ( Exception $e ) {
2830                         if ( $useTrx ) {
2831                                 $this->rollback( $fname );
2832                         }
2833                         throw $e;
2834                 }
2835                 if ( $useTrx ) {
2836                         $this->commit( $fname );
2837                 }
2838
2839                 return $ok;
2840         }
2841
2842         /**
2843          * DELETE where the condition is a join.
2844          *
2845          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2846          * we use sub-selects
2847          *
2848          * For safety, an empty $conds will not delete everything. If you want to
2849          * delete all rows where the join condition matches, set $conds='*'.
2850          *
2851          * DO NOT put the join condition in $conds.
2852          *
2853          * @param string $delTable The table to delete from.
2854          * @param string $joinTable The other table.
2855          * @param string $delVar The variable to join on, in the first table.
2856          * @param string $joinVar The variable to join on, in the second table.
2857          * @param array $conds Condition array of field names mapped to variables,
2858          *   ANDed together in the WHERE clause
2859          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2860          * @throws DBUnexpectedError
2861          */
2862         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2863                 $fname = __METHOD__
2864         ) {
2865                 if ( !$conds ) {
2866                         throw new DBUnexpectedError( $this,
2867                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2868                 }
2869
2870                 $delTable = $this->tableName( $delTable );
2871                 $joinTable = $this->tableName( $joinTable );
2872                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2873                 if ( $conds != '*' ) {
2874                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2875                 }
2876                 $sql .= ')';
2877
2878                 $this->query( $sql, $fname );
2879         }
2880
2881         /**
2882          * Returns the size of a text field, or -1 for "unlimited"
2883          *
2884          * @param string $table
2885          * @param string $field
2886          * @return int
2887          */
2888         public function textFieldSize( $table, $field ) {
2889                 $table = $this->tableName( $table );
2890                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2891                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2892                 $row = $this->fetchObject( $res );
2893
2894                 $m = array();
2895
2896                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2897                         $size = $m[1];
2898                 } else {
2899                         $size = -1;
2900                 }
2901
2902                 return $size;
2903         }
2904
2905         /**
2906          * A string to insert into queries to show that they're low-priority, like
2907          * MySQL's LOW_PRIORITY. If no such feature exists, return an empty
2908          * string and nothing bad should happen.
2909          *
2910          * @return string Returns the text of the low priority option if it is
2911          *   supported, or a blank string otherwise
2912          */
2913         public function lowPriorityOption() {
2914                 return '';
2915         }
2916
2917         /**
2918          * DELETE query wrapper.
2919          *
2920          * @param array $table Table name
2921          * @param string|array $conds of conditions. See $conds in DatabaseBase::select()
2922          *   for the format. Use $conds == "*" to delete all rows
2923          * @param string $fname name of the calling function
2924          * @throws DBUnexpectedError
2925          * @return bool|ResultWrapper
2926          */
2927         public function delete( $table, $conds, $fname = __METHOD__ ) {
2928                 if ( !$conds ) {
2929                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2930                 }
2931
2932                 $table = $this->tableName( $table );
2933                 $sql = "DELETE FROM $table";
2934
2935                 if ( $conds != '*' ) {
2936                         if ( is_array( $conds ) ) {
2937                                 $conds = $this->makeList( $conds, LIST_AND );
2938                         }
2939                         $sql .= ' WHERE ' . $conds;
2940                 }
2941
2942                 return $this->query( $sql, $fname );
2943         }
2944
2945         /**
2946          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2947          * into another table.
2948          *
2949          * @param string $destTable The table name to insert into
2950          * @param string|array $srcTable May be either a table name, or an array of table names
2951          *    to include in a join.
2952          *
2953          * @param array $varMap Must be an associative array of the form
2954          *    array( 'dest1' => 'source1', ...). Source items may be literals
2955          *    rather than field names, but strings should be quoted with
2956          *    DatabaseBase::addQuotes()
2957          *
2958          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2959          *    the details of the format of condition arrays. May be "*" to copy the
2960          *    whole table.
2961          *
2962          * @param string $fname The function name of the caller, from __METHOD__
2963          *
2964          * @param array $insertOptions Options for the INSERT part of the query, see
2965          *    DatabaseBase::insert() for details.
2966          * @param array $selectOptions Options for the SELECT part of the query, see
2967          *    DatabaseBase::select() for details.
2968          *
2969          * @return ResultWrapper
2970          */
2971         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2972                 $fname = __METHOD__,
2973                 $insertOptions = array(), $selectOptions = array()
2974         ) {
2975                 $destTable = $this->tableName( $destTable );
2976
2977                 if ( !is_array( $insertOptions ) ) {
2978                         $insertOptions = array( $insertOptions );
2979                 }
2980
2981                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2982
2983                 if ( !is_array( $selectOptions ) ) {
2984                         $selectOptions = array( $selectOptions );
2985                 }
2986
2987                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2988
2989                 if ( is_array( $srcTable ) ) {
2990                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2991                 } else {
2992                         $srcTable = $this->tableName( $srcTable );
2993                 }
2994
2995                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2996                         " SELECT $startOpts " . implode( ',', $varMap ) .
2997                         " FROM $srcTable $useIndex ";
2998
2999                 if ( $conds != '*' ) {
3000                         if ( is_array( $conds ) ) {
3001                                 $conds = $this->makeList( $conds, LIST_AND );
3002                         }
3003                         $sql .= " WHERE $conds";
3004                 }
3005
3006                 $sql .= " $tailOpts";
3007
3008                 return $this->query( $sql, $fname );
3009         }
3010
3011         /**
3012          * Construct a LIMIT query with optional offset. This is used for query
3013          * pages. The SQL should be adjusted so that only the first $limit rows
3014          * are returned. If $offset is provided as well, then the first $offset
3015          * rows should be discarded, and the next $limit rows should be returned.
3016          * If the result of the query is not ordered, then the rows to be returned
3017          * are theoretically arbitrary.
3018          *
3019          * $sql is expected to be a SELECT, if that makes a difference.
3020          *
3021          * The version provided by default works in MySQL and SQLite. It will very
3022          * likely need to be overridden for most other DBMSes.
3023          *
3024          * @param string $sql SQL query we will append the limit too
3025          * @param int $limit The SQL limit
3026          * @param int|bool $offset The SQL offset (default false)
3027          * @throws DBUnexpectedError
3028          * @return string
3029          */
3030         public function limitResult( $sql, $limit, $offset = false ) {
3031                 if ( !is_numeric( $limit ) ) {
3032                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
3033                 }
3034
3035                 return "$sql LIMIT "
3036                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
3037                         . "{$limit} ";
3038         }
3039
3040         /**
3041          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
3042          * within the UNION construct.
3043          * @return bool
3044          */
3045         public function unionSupportsOrderAndLimit() {
3046                 return true; // True for almost every DB supported
3047         }
3048
3049         /**
3050          * Construct a UNION query
3051          * This is used for providing overload point for other DB abstractions
3052          * not compatible with the MySQL syntax.
3053          * @param array $sqls SQL statements to combine
3054          * @param bool $all Use UNION ALL
3055          * @return string SQL fragment
3056          */
3057         public function unionQueries( $sqls, $all ) {
3058                 $glue = $all ? ') UNION ALL (' : ') UNION (';
3059
3060                 return '(' . implode( $glue, $sqls ) . ')';
3061         }
3062
3063         /**
3064          * Returns an SQL expression for a simple conditional. This doesn't need
3065          * to be overridden unless CASE isn't supported in your DBMS.
3066          *
3067          * @param string|array $cond SQL expression which will result in a boolean value
3068          * @param string $trueVal SQL expression to return if true
3069          * @param string $falseVal SQL expression to return if false
3070          * @return string SQL fragment
3071          */
3072         public function conditional( $cond, $trueVal, $falseVal ) {
3073                 if ( is_array( $cond ) ) {
3074                         $cond = $this->makeList( $cond, LIST_AND );
3075                 }
3076
3077                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
3078         }
3079
3080         /**
3081          * Returns a comand for str_replace function in SQL query.
3082          * Uses REPLACE() in MySQL
3083          *
3084          * @param string $orig Column to modify
3085          * @param string $old Column to seek
3086          * @param string $new Column to replace with
3087          *
3088          * @return string
3089          */
3090         public function strreplace( $orig, $old, $new ) {
3091                 return "REPLACE({$orig}, {$old}, {$new})";
3092         }
3093
3094         /**
3095          * Determines how long the server has been up
3096          * STUB
3097          *
3098          * @return int
3099          */
3100         public function getServerUptime() {
3101                 return 0;
3102         }
3103
3104         /**
3105          * Determines if the last failure was due to a deadlock
3106          * STUB
3107          *
3108          * @return bool
3109          */
3110         public function wasDeadlock() {
3111                 return false;
3112         }
3113
3114         /**
3115          * Determines if the last failure was due to a lock timeout
3116          * STUB
3117          *
3118          * @return bool
3119          */
3120         public function wasLockTimeout() {
3121                 return false;
3122         }
3123
3124         /**
3125          * Determines if the last query error was something that should be dealt
3126          * with by pinging the connection and reissuing the query.
3127          * STUB
3128          *
3129          * @return bool
3130          */
3131         public function wasErrorReissuable() {
3132                 return false;
3133         }
3134
3135         /**
3136          * Determines if the last failure was due to the database being read-only.
3137          * STUB
3138          *
3139          * @return bool
3140          */
3141         public function wasReadOnlyError() {
3142                 return false;
3143         }
3144
3145         /**
3146          * Perform a deadlock-prone transaction.
3147          *
3148          * This function invokes a callback function to perform a set of write
3149          * queries. If a deadlock occurs during the processing, the transaction
3150          * will be rolled back and the callback function will be called again.
3151          *
3152          * Usage:
3153          *   $dbw->deadlockLoop( callback, ... );
3154          *
3155          * Extra arguments are passed through to the specified callback function.
3156          *
3157          * Returns whatever the callback function returned on its successful,
3158          * iteration, or false on error, for example if the retry limit was
3159          * reached.
3160          *
3161          * @return bool
3162          */
3163         public function deadlockLoop() {
3164                 $this->begin( __METHOD__ );
3165                 $args = func_get_args();
3166                 $function = array_shift( $args );
3167                 $oldIgnore = $this->ignoreErrors( true );
3168                 $tries = self::DEADLOCK_TRIES;
3169
3170                 if ( is_array( $function ) ) {
3171                         $fname = $function[0];
3172                 } else {
3173                         $fname = $function;
3174                 }
3175
3176                 do {
3177                         $retVal = call_user_func_array( $function, $args );
3178                         $error = $this->lastError();
3179                         $errno = $this->lastErrno();
3180                         $sql = $this->lastQuery();
3181
3182                         if ( $errno ) {
3183                                 if ( $this->wasDeadlock() ) {
3184                                         # Retry
3185                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3186                                 } else {
3187                                         $this->reportQueryError( $error, $errno, $sql, $fname );
3188                                 }
3189                         }
3190                 } while ( $this->wasDeadlock() && --$tries > 0 );
3191
3192                 $this->ignoreErrors( $oldIgnore );
3193
3194                 if ( $tries <= 0 ) {
3195                         $this->rollback( __METHOD__ );
3196                         $this->reportQueryError( $error, $errno, $sql, $fname );
3197
3198                         return false;
3199                 } else {
3200                         $this->commit( __METHOD__ );
3201
3202                         return $retVal;
3203                 }
3204         }
3205
3206         /**
3207          * Wait for the slave to catch up to a given master position.
3208          *
3209          * @param DBMasterPos $pos
3210          * @param int $timeout The maximum number of seconds to wait for
3211          *   synchronisation
3212          * @return int Zzero if the slave was past that position already,
3213          *   greater than zero if we waited for some period of time, less than
3214          *   zero if we timed out.
3215          */
3216         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3217                 # Real waits are implemented in the subclass.
3218                 return 0;
3219         }
3220
3221         /**
3222          * Get the replication position of this slave
3223          *
3224          * @return DBMasterPos|bool False if this is not a slave.
3225          */
3226         public function getSlavePos() {
3227                 # Stub
3228                 return false;
3229         }
3230
3231         /**
3232          * Get the position of this master
3233          *
3234          * @return DBMasterPos|bool False if this is not a master
3235          */
3236         public function getMasterPos() {
3237                 # Stub
3238                 return false;
3239         }
3240
3241         /**
3242          * Run an anonymous function as soon as there is no transaction pending.
3243          * If there is a transaction and it is rolled back, then the callback is cancelled.
3244          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
3245          * Callbacks must commit any transactions that they begin.
3246          *
3247          * This is useful for updates to different systems or when separate transactions are needed.
3248          * For example, one might want to enqueue jobs into a system outside the database, but only
3249          * after the database is updated so that the jobs will see the data when they actually run.
3250          * It can also be used for updates that easily cause deadlocks if locks are held too long.
3251          *
3252          * @param callable $callback
3253          * @since 1.20
3254          */
3255         final public function onTransactionIdle( $callback ) {
3256                 $this->mTrxIdleCallbacks[] = array( $callback, wfGetCaller() );
3257                 if ( !$this->mTrxLevel ) {
3258                         $this->runOnTransactionIdleCallbacks();
3259                 }
3260         }
3261
3262         /**
3263          * Run an anonymous function before the current transaction commits or now if there is none.
3264          * If there is a transaction and it is rolled back, then the callback is cancelled.
3265          * Callbacks must not start nor commit any transactions.
3266          *
3267          * This is useful for updates that easily cause deadlocks if locks are held too long
3268          * but where atomicity is strongly desired for these updates and some related updates.
3269          *
3270          * @param callable $callback
3271          * @since 1.22
3272          */
3273         final public function onTransactionPreCommitOrIdle( $callback ) {
3274                 if ( $this->mTrxLevel ) {
3275                         $this->mTrxPreCommitCallbacks[] = array( $callback, wfGetCaller() );
3276                 } else {
3277                         $this->onTransactionIdle( $callback ); // this will trigger immediately
3278                 }
3279         }
3280
3281         /**
3282          * Actually any "on transaction idle" callbacks.
3283          *
3284          * @since 1.20
3285          */
3286         protected function runOnTransactionIdleCallbacks() {
3287                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
3288
3289                 $e = null; // last exception
3290                 do { // callbacks may add callbacks :)
3291                         $callbacks = $this->mTrxIdleCallbacks;
3292                         $this->mTrxIdleCallbacks = array(); // recursion guard
3293                         foreach ( $callbacks as $callback ) {
3294                                 try {
3295                                         list( $phpCallback ) = $callback;
3296                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
3297                                         call_user_func( $phpCallback );
3298                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3299                                 } catch ( Exception $e ) {
3300                                 }
3301                         }
3302                 } while ( count( $this->mTrxIdleCallbacks ) );
3303
3304                 if ( $e instanceof Exception ) {
3305                         throw $e; // re-throw any last exception
3306                 }
3307         }
3308
3309         /**
3310          * Actually any "on transaction pre-commit" callbacks.
3311          *
3312          * @since 1.22
3313          */
3314         protected function runOnTransactionPreCommitCallbacks() {
3315                 $e = null; // last exception
3316                 do { // callbacks may add callbacks :)
3317                         $callbacks = $this->mTrxPreCommitCallbacks;
3318                         $this->mTrxPreCommitCallbacks = array(); // recursion guard
3319                         foreach ( $callbacks as $callback ) {
3320                                 try {
3321                                         list( $phpCallback ) = $callback;
3322                                         call_user_func( $phpCallback );
3323                                 } catch ( Exception $e ) {
3324                                 }
3325                         }
3326                 } while ( count( $this->mTrxPreCommitCallbacks ) );
3327
3328                 if ( $e instanceof Exception ) {
3329                         throw $e; // re-throw any last exception
3330                 }
3331         }
3332
3333         /**
3334          * Begin an atomic section of statements
3335          *
3336          * If a transaction has been started already, just keep track of the given
3337          * section name to make sure the transaction is not committed pre-maturely.
3338          * This function can be used in layers (with sub-sections), so use a stack
3339          * to keep track of the different atomic sections. If there is no transaction,
3340          * start one implicitly.
3341          *
3342          * The goal of this function is to create an atomic section of SQL queries
3343          * without having to start a new transaction if it already exists.
3344          *
3345          * Atomic sections are more strict than transactions. With transactions,
3346          * attempting to begin a new transaction when one is already running results
3347          * in MediaWiki issuing a brief warning and doing an implicit commit. All
3348          * atomic levels *must* be explicitly closed using DatabaseBase::endAtomic(),
3349          * and any database transactions cannot be began or committed until all atomic
3350          * levels are closed. There is no such thing as implicitly opening or closing
3351          * an atomic section.
3352          *
3353          * @since 1.23
3354          * @param string $fname
3355          * @throws DBError
3356          */
3357         final public function startAtomic( $fname = __METHOD__ ) {
3358                 if ( !$this->mTrxLevel ) {
3359                         $this->begin( $fname );
3360                         $this->mTrxAutomatic = true;
3361                         $this->mTrxAutomaticAtomic = true;
3362                 }
3363
3364                 $this->mTrxAtomicLevels->push( $fname );
3365         }
3366
3367         /**
3368          * Ends an atomic section of SQL statements
3369          *
3370          * Ends the next section of atomic SQL statements and commits the transaction
3371          * if necessary.
3372          *
3373          * @since 1.23
3374          * @see DatabaseBase::startAtomic
3375          * @param string $fname
3376          * @throws DBError
3377          */
3378         final public function endAtomic( $fname = __METHOD__ ) {
3379                 if ( !$this->mTrxLevel ) {
3380                         throw new DBUnexpectedError( $this, 'No atomic transaction is open.' );
3381                 }
3382                 if ( $this->mTrxAtomicLevels->isEmpty() ||
3383                         $this->mTrxAtomicLevels->pop() !== $fname
3384                 ) {
3385                         throw new DBUnexpectedError( $this, 'Invalid atomic section ended.' );
3386                 }
3387
3388                 if ( $this->mTrxAtomicLevels->isEmpty() && $this->mTrxAutomaticAtomic ) {
3389                         $this->commit( $fname, 'flush' );
3390                 }
3391         }
3392
3393         /**
3394          * Begin a transaction. If a transaction is already in progress,
3395          * that transaction will be committed before the new transaction is started.
3396          *
3397          * Note that when the DBO_TRX flag is set (which is usually the case for web
3398          * requests, but not for maintenance scripts), any previous database query
3399          * will have started a transaction automatically.
3400          *
3401          * Nesting of transactions is not supported. Attempts to nest transactions
3402          * will cause a warning, unless the current transaction was started
3403          * automatically because of the DBO_TRX flag.
3404          *
3405          * @param string $fname
3406          * @throws DBError
3407          */
3408         final public function begin( $fname = __METHOD__ ) {
3409                 global $wgDebugDBTransactions;
3410
3411                 if ( $this->mTrxLevel ) { // implicit commit
3412                         if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3413                                 // If the current transaction was an automatic atomic one, then we definitely have
3414                                 // a problem. Same if there is any unclosed atomic level.
3415                                 throw new DBUnexpectedError( $this,
3416                                         "Attempted to start explicit transaction when atomic levels are still open."
3417                                 );
3418                         } elseif ( !$this->mTrxAutomatic ) {
3419                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3420                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3421                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3422                                         " performing implicit commit!";
3423                                 wfWarn( $msg );
3424                                 wfLogDBError( $msg );
3425                         } else {
3426                                 // if the transaction was automatic and has done write operations,
3427                                 // log it if $wgDebugDBTransactions is enabled.
3428                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3429                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3430                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3431                                         );
3432                                 }
3433                         }
3434
3435                         $this->runOnTransactionPreCommitCallbacks();
3436                         $this->doCommit( $fname );
3437                         if ( $this->mTrxDoneWrites ) {
3438                                 Profiler::instance()->transactionWritingOut(
3439                                         $this->mServer, $this->mDBname, $this->mTrxShortId );
3440                         }
3441                         $this->runOnTransactionIdleCallbacks();
3442                 }
3443
3444                 # Avoid fatals if close() was called
3445                 if ( !$this->isOpen() ) {
3446                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3447                 }
3448
3449                 $this->doBegin( $fname );
3450                 $this->mTrxFname = $fname;
3451                 $this->mTrxDoneWrites = false;
3452                 $this->mTrxAutomatic = false;
3453                 $this->mTrxAutomaticAtomic = false;
3454                 $this->mTrxAtomicLevels = new SplStack;
3455                 $this->mTrxIdleCallbacks = array();
3456                 $this->mTrxPreCommitCallbacks = array();
3457                 $this->mTrxShortId = wfRandomString( 12 );
3458         }
3459
3460         /**
3461          * Issues the BEGIN command to the database server.
3462          *
3463          * @see DatabaseBase::begin()
3464          * @param string $fname
3465          */
3466         protected function doBegin( $fname ) {
3467                 $this->query( 'BEGIN', $fname );
3468                 $this->mTrxLevel = 1;
3469         }
3470
3471         /**
3472          * Commits a transaction previously started using begin().
3473          * If no transaction is in progress, a warning is issued.
3474          *
3475          * Nesting of transactions is not supported.
3476          *
3477          * @param string $fname
3478          * @param string $flush Flush flag, set to 'flush' to disable warnings about
3479          *   explicitly committing implicit transactions, or calling commit when no
3480          *   transaction is in progress. This will silently break any ongoing
3481          *   explicit transaction. Only set the flush flag if you are sure that it
3482          *   is safe to ignore these warnings in your context.
3483          * @throws DBUnexpectedError
3484          */
3485         final public function commit( $fname = __METHOD__, $flush = '' ) {
3486                 if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3487                         // There are still atomic sections open. This cannot be ignored
3488                         throw new DBUnexpectedError(
3489                                 $this,
3490                                 "Attempted to commit transaction while atomic sections are still open"
3491                         );
3492                 }
3493
3494                 if ( $flush === 'flush' ) {
3495                         if ( !$this->mTrxLevel ) {
3496                                 return; // nothing to do
3497                         } elseif ( !$this->mTrxAutomatic ) {
3498                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3499                         }
3500                 } else {
3501                         if ( !$this->mTrxLevel ) {
3502                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3503                                 return; // nothing to do
3504                         } elseif ( $this->mTrxAutomatic ) {
3505                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3506                         }
3507                 }
3508
3509                 # Avoid fatals if close() was called
3510                 if ( !$this->isOpen() ) {
3511                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3512                 }
3513
3514                 $this->runOnTransactionPreCommitCallbacks();
3515                 $this->doCommit( $fname );
3516                 if ( $this->mTrxDoneWrites ) {
3517                         Profiler::instance()->transactionWritingOut(
3518                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
3519                 }
3520                 $this->runOnTransactionIdleCallbacks();
3521         }
3522
3523         /**
3524          * Issues the COMMIT command to the database server.
3525          *
3526          * @see DatabaseBase::commit()
3527          * @param string $fname
3528          */
3529         protected function doCommit( $fname ) {
3530                 if ( $this->mTrxLevel ) {
3531                         $this->query( 'COMMIT', $fname );
3532                         $this->mTrxLevel = 0;
3533                 }
3534         }
3535
3536         /**
3537          * Rollback a transaction previously started using begin().
3538          * If no transaction is in progress, a warning is issued.
3539          *
3540          * No-op on non-transactional databases.
3541          *
3542          * @param string $fname
3543          * @param string $flush Flush flag, set to 'flush' to disable warnings about
3544          *   calling rollback when no transaction is in progress. This will silently
3545          *   break any ongoing explicit transaction. Only set the flush flag if you
3546          *   are sure that it is safe to ignore these warnings in your context.
3547          * @since 1.23 Added $flush parameter
3548          */
3549         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3550                 if ( $flush !== 'flush' ) {
3551                         if ( !$this->mTrxLevel ) {
3552                                 wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3553                                 return; // nothing to do
3554                         } elseif ( $this->mTrxAutomatic ) {
3555                                 wfWarn( "$fname: Explicit rollback of implicit transaction. Something may be out of sync!" );
3556                         }
3557                 } else {
3558                         if ( !$this->mTrxLevel ) {
3559                                 return; // nothing to do
3560                         } elseif ( !$this->mTrxAutomatic ) {
3561                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3562                         }
3563                 }
3564
3565                 # Avoid fatals if close() was called
3566                 if ( !$this->isOpen() ) {
3567                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
3568                 }
3569
3570                 $this->doRollback( $fname );
3571                 $this->mTrxIdleCallbacks = array(); // cancel
3572                 $this->mTrxPreCommitCallbacks = array(); // cancel
3573                 $this->mTrxAtomicLevels = new SplStack;
3574                 if ( $this->mTrxDoneWrites ) {
3575                         Profiler::instance()->transactionWritingOut(
3576                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
3577                 }
3578         }
3579
3580         /**
3581          * Issues the ROLLBACK command to the database server.
3582          *
3583          * @see DatabaseBase::rollback()
3584          * @param string $fname
3585          */
3586         protected function doRollback( $fname ) {
3587                 if ( $this->mTrxLevel ) {
3588                         $this->query( 'ROLLBACK', $fname, true );
3589                         $this->mTrxLevel = 0;
3590                 }
3591         }
3592
3593         /**
3594          * Creates a new table with structure copied from existing table
3595          * Note that unlike most database abstraction functions, this function does not
3596          * automatically append database prefix, because it works at a lower
3597          * abstraction level.
3598          * The table names passed to this function shall not be quoted (this
3599          * function calls addIdentifierQuotes when needed).
3600          *
3601          * @param string $oldName Name of table whose structure should be copied
3602          * @param string $newName Name of table to be created
3603          * @param bool $temporary Whether the new table should be temporary
3604          * @param string $fname Calling function name
3605          * @throws MWException
3606          * @return bool True if operation was successful
3607          */
3608         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3609                 $fname = __METHOD__
3610         ) {
3611                 throw new MWException(
3612                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3613         }
3614
3615         /**
3616          * List all tables on the database
3617          *
3618          * @param string $prefix Only show tables with this prefix, e.g. mw_
3619          * @param string $fname Calling function name
3620          * @throws MWException
3621          */
3622         function listTables( $prefix = null, $fname = __METHOD__ ) {
3623                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3624         }
3625
3626         /**
3627          * Reset the views process cache set by listViews()
3628          * @since 1.22
3629          */
3630         final public function clearViewsCache() {
3631                 $this->allViews = null;
3632         }
3633
3634         /**
3635          * Lists all the VIEWs in the database
3636          *
3637          * For caching purposes the list of all views should be stored in
3638          * $this->allViews. The process cache can be cleared with clearViewsCache()
3639          *
3640          * @param string $prefix Only show VIEWs with this prefix, eg. unit_test_
3641          * @param string $fname Name of calling function
3642          * @throws MWException
3643          * @since 1.22
3644          */
3645         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3646                 throw new MWException( 'DatabaseBase::listViews is not implemented in descendant class' );
3647         }
3648
3649         /**
3650          * Differentiates between a TABLE and a VIEW
3651          *
3652          * @param string $name Name of the database-structure to test.
3653          * @throws MWException
3654          * @since 1.22
3655          */
3656         public function isView( $name ) {
3657                 throw new MWException( 'DatabaseBase::isView is not implemented in descendant class' );
3658         }
3659
3660         /**
3661          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3662          * to the format used for inserting into timestamp fields in this DBMS.
3663          *
3664          * The result is unquoted, and needs to be passed through addQuotes()
3665          * before it can be included in raw SQL.
3666          *
3667          * @param string|int $ts
3668          *
3669          * @return string
3670          */
3671         public function timestamp( $ts = 0 ) {
3672                 return wfTimestamp( TS_MW, $ts );
3673         }
3674
3675         /**
3676          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3677          * to the format used for inserting into timestamp fields in this DBMS. If
3678          * NULL is input, it is passed through, allowing NULL values to be inserted
3679          * into timestamp fields.
3680          *
3681          * The result is unquoted, and needs to be passed through addQuotes()
3682          * before it can be included in raw SQL.
3683          *
3684          * @param string|int $ts
3685          *
3686          * @return string
3687          */
3688         public function timestampOrNull( $ts = null ) {
3689                 if ( is_null( $ts ) ) {
3690                         return null;
3691                 } else {
3692                         return $this->timestamp( $ts );
3693                 }
3694         }
3695
3696         /**
3697          * Take the result from a query, and wrap it in a ResultWrapper if
3698          * necessary. Boolean values are passed through as is, to indicate success
3699          * of write queries or failure.
3700          *
3701          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3702          * resource, and it was necessary to call this function to convert it to
3703          * a wrapper. Nowadays, raw database objects are never exposed to external
3704          * callers, so this is unnecessary in external code. For compatibility with
3705          * old code, ResultWrapper objects are passed through unaltered.
3706          *
3707          * @param bool|ResultWrapper|resource $result
3708          * @return bool|ResultWrapper
3709          */
3710         public function resultObject( $result ) {
3711                 if ( empty( $result ) ) {
3712                         return false;
3713                 } elseif ( $result instanceof ResultWrapper ) {
3714                         return $result;
3715                 } elseif ( $result === true ) {
3716                         // Successful write query
3717                         return $result;
3718                 } else {
3719                         return new ResultWrapper( $this, $result );
3720                 }
3721         }
3722
3723         /**
3724          * Ping the server and try to reconnect if it there is no connection
3725          *
3726          * @return bool Success or failure
3727          */
3728         public function ping() {
3729                 # Stub. Not essential to override.
3730                 return true;
3731         }
3732
3733         /**
3734          * Get slave lag. Currently supported only by MySQL.
3735          *
3736          * Note that this function will generate a fatal error on many
3737          * installations. Most callers should use LoadBalancer::safeGetLag()
3738          * instead.
3739          *
3740          * @return int Database replication lag in seconds
3741          */
3742         public function getLag() {
3743                 return 0;
3744         }
3745
3746         /**
3747          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3748          *
3749          * @return int
3750          */
3751         function maxListLen() {
3752                 return 0;
3753         }
3754
3755         /**
3756          * Some DBMSs have a special format for inserting into blob fields, they
3757          * don't allow simple quoted strings to be inserted. To insert into such
3758          * a field, pass the data through this function before passing it to
3759          * DatabaseBase::insert().
3760          *
3761          * @param string $b
3762          * @return string
3763          */
3764         public function encodeBlob( $b ) {
3765                 return $b;
3766         }
3767
3768         /**
3769          * Some DBMSs return a special placeholder object representing blob fields
3770          * in result objects. Pass the object through this function to return the
3771          * original string.
3772          *
3773          * @param string $b
3774          * @return string
3775          */
3776         public function decodeBlob( $b ) {
3777                 return $b;
3778         }
3779
3780         /**
3781          * Override database's default behavior. $options include:
3782          *     'connTimeout' : Set the connection timeout value in seconds.
3783          *                     May be useful for very long batch queries such as
3784          *                     full-wiki dumps, where a single query reads out over
3785          *                     hours or days.
3786          *
3787          * @param array $options
3788          * @return void
3789          */
3790         public function setSessionOptions( array $options ) {
3791         }
3792
3793         /**
3794          * Read and execute SQL commands from a file.
3795          *
3796          * Returns true on success, error string or exception on failure (depending
3797          * on object's error ignore settings).
3798          *
3799          * @param string $filename File name to open
3800          * @param bool|callable $lineCallback Optional function called before reading each line
3801          * @param bool|callable $resultCallback Optional function called for each MySQL result
3802          * @param bool|string $fname Calling function name or false if name should be
3803          *   generated dynamically using $filename
3804          * @param bool|callable $inputCallback Optional function called for each
3805          *   complete line sent
3806          * @throws Exception|MWException
3807          * @return bool|string
3808          */
3809         public function sourceFile(
3810                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3811         ) {
3812                 wfSuppressWarnings();
3813                 $fp = fopen( $filename, 'r' );
3814                 wfRestoreWarnings();
3815
3816                 if ( false === $fp ) {
3817                         throw new MWException( "Could not open \"{$filename}\".\n" );
3818                 }
3819
3820                 if ( !$fname ) {
3821                         $fname = __METHOD__ . "( $filename )";
3822                 }
3823
3824                 try {
3825                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3826                 } catch ( MWException $e ) {
3827                         fclose( $fp );
3828                         throw $e;
3829                 }
3830
3831                 fclose( $fp );
3832
3833                 return $error;
3834         }
3835
3836         /**
3837          * Get the full path of a patch file. Originally based on archive()
3838          * from updaters.inc. Keep in mind this always returns a patch, as
3839          * it fails back to MySQL if no DB-specific patch can be found
3840          *
3841          * @param string $patch The name of the patch, like patch-something.sql
3842          * @return string Full path to patch file
3843          */
3844         public function patchPath( $patch ) {
3845                 global $IP;
3846
3847                 $dbType = $this->getType();
3848                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3849                         return "$IP/maintenance/$dbType/archives/$patch";
3850                 } else {
3851                         return "$IP/maintenance/archives/$patch";
3852                 }
3853         }
3854
3855         /**
3856          * Set variables to be used in sourceFile/sourceStream, in preference to the
3857          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3858          * all. If it's set to false, $GLOBALS will be used.
3859          *
3860          * @param bool|array $vars Mapping variable name to value.
3861          */
3862         public function setSchemaVars( $vars ) {
3863                 $this->mSchemaVars = $vars;
3864         }
3865
3866         /**
3867          * Read and execute commands from an open file handle.
3868          *
3869          * Returns true on success, error string or exception on failure (depending
3870          * on object's error ignore settings).
3871          *
3872          * @param resource $fp File handle
3873          * @param bool|callable $lineCallback Optional function called before reading each query
3874          * @param bool|callable $resultCallback Optional function called for each MySQL result
3875          * @param string $fname Calling function name
3876          * @param bool|callable $inputCallback Optional function called for each complete query sent
3877          * @return bool|string
3878          */
3879         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3880                 $fname = __METHOD__, $inputCallback = false
3881         ) {
3882                 $cmd = '';
3883
3884                 while ( !feof( $fp ) ) {
3885                         if ( $lineCallback ) {
3886                                 call_user_func( $lineCallback );
3887                         }
3888
3889                         $line = trim( fgets( $fp ) );
3890
3891                         if ( $line == '' ) {
3892                                 continue;
3893                         }
3894
3895                         if ( '-' == $line[0] && '-' == $line[1] ) {
3896                                 continue;
3897                         }
3898
3899                         if ( $cmd != '' ) {
3900                                 $cmd .= ' ';
3901                         }
3902
3903                         $done = $this->streamStatementEnd( $cmd, $line );
3904
3905                         $cmd .= "$line\n";
3906
3907                         if ( $done || feof( $fp ) ) {
3908                                 $cmd = $this->replaceVars( $cmd );
3909
3910                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3911                                         $res = $this->query( $cmd, $fname );
3912
3913                                         if ( $resultCallback ) {
3914                                                 call_user_func( $resultCallback, $res, $this );
3915                                         }
3916
3917                                         if ( false === $res ) {
3918                                                 $err = $this->lastError();
3919
3920                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3921                                         }
3922                                 }
3923                                 $cmd = '';
3924                         }
3925                 }
3926
3927                 return true;
3928         }
3929
3930         /**
3931          * Called by sourceStream() to check if we've reached a statement end
3932          *
3933          * @param string $sql SQL assembled so far
3934          * @param string $newLine New line about to be added to $sql
3935          * @return bool Whether $newLine contains end of the statement
3936          */
3937         public function streamStatementEnd( &$sql, &$newLine ) {
3938                 if ( $this->delimiter ) {
3939                         $prev = $newLine;
3940                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3941                         if ( $newLine != $prev ) {
3942                                 return true;
3943                         }
3944                 }
3945
3946                 return false;
3947         }
3948
3949         /**
3950          * Database independent variable replacement. Replaces a set of variables
3951          * in an SQL statement with their contents as given by $this->getSchemaVars().
3952          *
3953          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3954          *
3955          * - '{$var}' should be used for text and is passed through the database's
3956          *   addQuotes method.
3957          * - `{$var}` should be used for identifiers (eg: table and database names),
3958          *   it is passed through the database's addIdentifierQuotes method which
3959          *   can be overridden if the database uses something other than backticks.
3960          * - / *$var* / is just encoded, besides traditional table prefix and
3961          *   table options its use should be avoided.
3962          *
3963          * @param string $ins SQL statement to replace variables in
3964          * @return string The new SQL statement with variables replaced
3965          */
3966         protected function replaceSchemaVars( $ins ) {
3967                 $vars = $this->getSchemaVars();
3968                 foreach ( $vars as $var => $value ) {
3969                         // replace '{$var}'
3970                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3971                         // replace `{$var}`
3972                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3973                         // replace /*$var*/
3974                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3975                 }
3976
3977                 return $ins;
3978         }
3979
3980         /**
3981          * Replace variables in sourced SQL
3982          *
3983          * @param string $ins
3984          * @return string
3985          */
3986         protected function replaceVars( $ins ) {
3987                 $ins = $this->replaceSchemaVars( $ins );
3988
3989                 // Table prefixes
3990                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3991                         array( $this, 'tableNameCallback' ), $ins );
3992
3993                 // Index names
3994                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3995                         array( $this, 'indexNameCallback' ), $ins );
3996
3997                 return $ins;
3998         }
3999
4000         /**
4001          * Get schema variables. If none have been set via setSchemaVars(), then
4002          * use some defaults from the current object.
4003          *
4004          * @return array
4005          */
4006         protected function getSchemaVars() {
4007                 if ( $this->mSchemaVars ) {
4008                         return $this->mSchemaVars;
4009                 } else {
4010                         return $this->getDefaultSchemaVars();
4011                 }
4012         }
4013
4014         /**
4015          * Get schema variables to use if none have been set via setSchemaVars().
4016          *
4017          * Override this in derived classes to provide variables for tables.sql
4018          * and SQL patch files.
4019          *
4020          * @return array
4021          */
4022         protected function getDefaultSchemaVars() {
4023                 return array();
4024         }
4025
4026         /**
4027          * Table name callback
4028          *
4029          * @param array $matches
4030          * @return string
4031          */
4032         protected function tableNameCallback( $matches ) {
4033                 return $this->tableName( $matches[1] );
4034         }
4035
4036         /**
4037          * Index name callback
4038          *
4039          * @param array $matches
4040          * @return string
4041          */
4042         protected function indexNameCallback( $matches ) {
4043                 return $this->indexName( $matches[1] );
4044         }
4045
4046         /**
4047          * Check to see if a named lock is available. This is non-blocking.
4048          *
4049          * @param string $lockName Name of lock to poll
4050          * @param string $method Name of method calling us
4051          * @return bool
4052          * @since 1.20
4053          */
4054         public function lockIsFree( $lockName, $method ) {
4055                 return true;
4056         }
4057
4058         /**
4059          * Acquire a named lock
4060          *
4061          * Abstracted from Filestore::lock() so child classes can implement for
4062          * their own needs.
4063          *
4064          * @param string $lockName Name of lock to aquire
4065          * @param string $method Name of method calling us
4066          * @param int $timeout
4067          * @return bool
4068          */
4069         public function lock( $lockName, $method, $timeout = 5 ) {
4070                 return true;
4071         }
4072
4073         /**
4074          * Release a lock.
4075          *
4076          * @param string $lockName Name of lock to release
4077          * @param string $method Name of method calling us
4078          *
4079          * @return int Returns 1 if the lock was released, 0 if the lock was not established
4080          * by this thread (in which case the lock is not released), and NULL if the named
4081          * lock did not exist
4082          */
4083         public function unlock( $lockName, $method ) {
4084                 return true;
4085         }
4086
4087         /**
4088          * Lock specific tables
4089          *
4090          * @param array $read Array of tables to lock for read access
4091          * @param array $write Array of tables to lock for write access
4092          * @param string $method Name of caller
4093          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
4094          * @return bool
4095          */
4096         public function lockTables( $read, $write, $method, $lowPriority = true ) {
4097                 return true;
4098         }
4099
4100         /**
4101          * Unlock specific tables
4102          *
4103          * @param string $method The caller
4104          * @return bool
4105          */
4106         public function unlockTables( $method ) {
4107                 return true;
4108         }
4109
4110         /**
4111          * Delete a table
4112          * @param string $tableName
4113          * @param string $fName
4114          * @return bool|ResultWrapper
4115          * @since 1.18
4116          */
4117         public function dropTable( $tableName, $fName = __METHOD__ ) {
4118                 if ( !$this->tableExists( $tableName, $fName ) ) {
4119                         return false;
4120                 }
4121                 $sql = "DROP TABLE " . $this->tableName( $tableName );
4122                 if ( $this->cascadingDeletes() ) {
4123                         $sql .= " CASCADE";
4124                 }
4125
4126                 return $this->query( $sql, $fName );
4127         }
4128
4129         /**
4130          * Get search engine class. All subclasses of this need to implement this
4131          * if they wish to use searching.
4132          *
4133          * @return string
4134          */
4135         public function getSearchEngine() {
4136                 return 'SearchEngineDummy';
4137         }
4138
4139         /**
4140          * Find out when 'infinity' is. Most DBMSes support this. This is a special
4141          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
4142          * because "i" sorts after all numbers.
4143          *
4144          * @return string
4145          */
4146         public function getInfinity() {
4147                 return 'infinity';
4148         }
4149
4150         /**
4151          * Encode an expiry time into the DBMS dependent format
4152          *
4153          * @param string $expiry timestamp for expiry, or the 'infinity' string
4154          * @return string
4155          */
4156         public function encodeExpiry( $expiry ) {
4157                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4158                         ? $this->getInfinity()
4159                         : $this->timestamp( $expiry );
4160         }
4161
4162         /**
4163          * Decode an expiry time into a DBMS independent format
4164          *
4165          * @param string $expiry DB timestamp field value for expiry
4166          * @param int $format TS_* constant, defaults to TS_MW
4167          * @return string
4168          */
4169         public function decodeExpiry( $expiry, $format = TS_MW ) {
4170                 return ( $expiry == '' || $expiry == $this->getInfinity() )
4171                         ? 'infinity'
4172                         : wfTimestamp( $format, $expiry );
4173         }
4174
4175         /**
4176          * Allow or deny "big selects" for this session only. This is done by setting
4177          * the sql_big_selects session variable.
4178          *
4179          * This is a MySQL-specific feature.
4180          *
4181          * @param bool|string $value True for allow, false for deny, or "default" to
4182          *   restore the initial value
4183          */
4184         public function setBigSelects( $value = true ) {
4185                 // no-op
4186         }
4187
4188         /**
4189          * @since 1.19
4190          */
4191         public function __toString() {
4192                 return (string)$this->mConn;
4193         }
4194
4195         /**
4196          * Run a few simple sanity checks
4197          */
4198         public function __destruct() {
4199                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
4200                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
4201                 }
4202                 if ( count( $this->mTrxIdleCallbacks ) || count( $this->mTrxPreCommitCallbacks ) ) {
4203                         $callers = array();
4204                         foreach ( $this->mTrxIdleCallbacks as $callbackInfo ) {
4205                                 $callers[] = $callbackInfo[1];
4206                         }
4207                         $callers = implode( ', ', $callers );
4208                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
4209                 }
4210         }
4211 }