includes/db/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * This file deals with database interface functions
   6  * and query specifics/optimisations.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Database
  25  */
  26
  27 /** Number of times to re-try an operation in case of deadlock */
  28 define( 'DEADLOCK_TRIES', 4 );
  29 /** Minimum time to wait before retry, in microseconds */
  30 define( 'DEADLOCK_DELAY_MIN', 500000 );
  31 /** Maximum time to wait before retry */
  32 define( 'DEADLOCK_DELAY_MAX', 1500000 );
  33
  34 /**
  35  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  36  * following must be implemented to support MediaWiki
  37  *
  38  * @file
  39  * @ingroup Database
  40  */
  41 interface DatabaseType {
  42         /**
  43          * Get the type of the DBMS, as it appears in $wgDBtype.
  44          *
  45          * @return string
  46          */
  47         function getType();
  48
  49         /**
  50          * Open a connection to the database. Usually aborts on failure
  51          *
  52          * @param $server String: database server host
  53          * @param $user String: database user name
  54          * @param $password String: database user password
  55          * @param $dbName String: database name
  56          * @return bool
  57          * @throws DBConnectionError
  58          */
  59         function open( $server, $user, $password, $dbName );
  60
  61         /**
  62          * Fetch the next row from the given result object, in object form.
  63          * Fields can be retrieved with $row->fieldname, with fields acting like
  64          * member variables.
  65          *
  66          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  67          * @return Row object
  68          * @throws DBUnexpectedError Thrown if the database returns an error
  69          */
  70         function fetchObject( $res );
  71
  72         /**
  73          * Fetch the next row from the given result object, in associative array
  74          * form.  Fields are retrieved with $row['fieldname'].
  75          *
  76          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  77          * @return Row object
  78          * @throws DBUnexpectedError Thrown if the database returns an error
  79          */
  80         function fetchRow( $res );
  81
  82         /**
  83          * Get the number of rows in a result object
  84          *
  85          * @param $res Mixed: A SQL result
  86          * @return int
  87          */
  88         function numRows( $res );
  89
  90         /**
  91          * Get the number of fields in a result object
  92          * @see http://www.php.net/mysql_num_fields
  93          *
  94          * @param $res Mixed: A SQL result
  95          * @return int
  96          */
  97         function numFields( $res );
  98
  99         /**
 100          * Get a field name in a result object
 101          * @see http://www.php.net/mysql_field_name
 102          *
 103          * @param $res Mixed: A SQL result
 104          * @param $n Integer
 105          * @return string
 106          */
 107         function fieldName( $res, $n );
 108
 109         /**
 110          * Get the inserted value of an auto-increment row
 111          *
 112          * The value inserted should be fetched from nextSequenceValue()
 113          *
 114          * Example:
 115          * $id = $dbw->nextSequenceValue('page_page_id_seq');
 116          * $dbw->insert('page',array('page_id' => $id));
 117          * $id = $dbw->insertId();
 118          *
 119          * @return int
 120          */
 121         function insertId();
 122
 123         /**
 124          * Change the position of the cursor in a result object
 125          * @see http://www.php.net/mysql_data_seek
 126          *
 127          * @param $res Mixed: A SQL result
 128          * @param $row Mixed: Either MySQL row or ResultWrapper
 129          */
 130         function dataSeek( $res, $row );
 131
 132         /**
 133          * Get the last error number
 134          * @see http://www.php.net/mysql_errno
 135          *
 136          * @return int
 137          */
 138         function lastErrno();
 139
 140         /**
 141          * Get a description of the last error
 142          * @see http://www.php.net/mysql_error
 143          *
 144          * @return string
 145          */
 146         function lastError();
 147
 148         /**
 149          * mysql_fetch_field() wrapper
 150          * Returns false if the field doesn't exist
 151          *
 152          * @param $table string: table name
 153          * @param $field string: field name
 154          *
 155          * @return Field
 156          */
 157         function fieldInfo( $table, $field );
 158
 159         /**
 160          * Get information about an index into an object
 161          * @param $table string: Table name
 162          * @param $index string: Index name
 163          * @param $fname string: Calling function name
 164          * @return Mixed: Database-specific index description class or false if the index does not exist
 165          */
 166         function indexInfo( $table, $index, $fname = 'Database::indexInfo' );
 167
 168         /**
 169          * Get the number of rows affected by the last write query
 170          * @see http://www.php.net/mysql_affected_rows
 171          *
 172          * @return int
 173          */
 174         function affectedRows();
 175
 176         /**
 177          * Wrapper for addslashes()
 178          *
 179          * @param $s string: to be slashed.
 180          * @return string: slashed string.
 181          */
 182         function strencode( $s );
 183
 184         /**
 185          * Returns a wikitext link to the DB's website, e.g.,
 186          *     return "[http://www.mysql.com/ MySQL]";
 187          * Should at least contain plain text, if for some reason
 188          * your database has no website.
 189          *
 190          * @return string: wikitext of a link to the server software's web site
 191          */
 192         static function getSoftwareLink();
 193
 194         /**
 195          * A string describing the current software version, like from
 196          * mysql_get_server_info().
 197          *
 198          * @return string: Version information from the database server.
 199          */
 200         function getServerVersion();
 201
 202         /**
 203          * A string describing the current software version, and possibly
 204          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 205          * Use getServerVersion() to get machine-friendly information.
 206          *
 207          * @return string: Version information from the database server
 208          */
 209         function getServerInfo();
 210 }
 211
 212 /**
 213  * Database abstraction object
 214  * @ingroup Database
 215  */
 216 abstract class DatabaseBase implements DatabaseType {
 217
 218 # ------------------------------------------------------------------------------
 219 # Variables
 220 # ------------------------------------------------------------------------------
 221
 222         protected $mLastQuery = '';
 223         protected $mDoneWrites = false;
 224         protected $mPHPError = false;
 225
 226         protected $mServer, $mUser, $mPassword, $mDBname;
 227
 228         /**
 229          * @var DatabaseBase
 230          */
 231         protected $mConn = null;
 232         protected $mOpened = false;
 233
 234         protected $mTablePrefix;
 235         protected $mFlags;
 236         protected $mTrxLevel = 0;
 237         protected $mErrorCount = 0;
 238         protected $mLBInfo = array();
 239         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 240         protected $mDefaultBigSelects = null;
 241         protected $mSchemaVars = false;
 242
 243         protected $preparedArgs;
 244
 245         protected $htmlErrors;
 246
 247         protected $delimiter = ';';
 248
 249 # ------------------------------------------------------------------------------
 250 # Accessors
 251 # ------------------------------------------------------------------------------
 252         # These optionally set a variable and return the previous state
 253
 254         /**
 255          * A string describing the current software version, and possibly
 256          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 257          * Use getServerVersion() to get machine-friendly information.
 258          *
 259          * @return string: Version information from the database server
 260          */
 261         public function getServerInfo() {
 262                 return $this->getServerVersion();
 263         }
 264
 265         /**
 266          * Boolean, controls output of large amounts of debug information.
 267          * @param $debug bool|null
 268          *   - true to enable debugging
 269          *   - false to disable debugging
 270          *   - omitted or null to do nothing
 271          *
 272          * @return bool|null previous value of the flag
 273          */
 274         function debug( $debug = null ) {
 275                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 276         }
 277
 278         /**
 279          * Turns buffering of SQL result sets on (true) or off (false). Default is
 280          * "on".
 281          *
 282          * Unbuffered queries are very troublesome in MySQL:
 283          *
 284          *   - If another query is executed while the first query is being read
 285          *     out, the first query is killed. This means you can't call normal
 286          *     MediaWiki functions while you are reading an unbuffered query result
 287          *     from a normal wfGetDB() connection.
 288          *
 289          *   - Unbuffered queries cause the MySQL server to use large amounts of
 290          *     memory and to hold broad locks which block other queries.
 291          *
 292          * If you want to limit client-side memory, it's almost always better to
 293          * split up queries into batches using a LIMIT clause than to switch off
 294          * buffering.
 295          *
 296          * @param $buffer null|bool
 297          *
 298          * @return null|bool The previous value of the flag
 299          */
 300         function bufferResults( $buffer = null ) {
 301                 if ( is_null( $buffer ) ) {
 302                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 303                 } else {
 304                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 305                 }
 306         }
 307
 308         /**
 309          * Turns on (false) or off (true) the automatic generation and sending
 310          * of a "we're sorry, but there has been a database error" page on
 311          * database errors. Default is on (false). When turned off, the
 312          * code should use lastErrno() and lastError() to handle the
 313          * situation as appropriate.
 314          *
 315          * @param $ignoreErrors bool|null
 316          *
 317          * @return bool The previous value of the flag.
 318          */
 319         function ignoreErrors( $ignoreErrors = null ) {
 320                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 321         }
 322
 323         /**
 324          * Gets or sets the current transaction level.
 325          *
 326          * Historically, transactions were allowed to be "nested". This is no
 327          * longer supported, so this function really only returns a boolean.
 328          *
 329          * @param $level int An integer (0 or 1), or omitted to leave it unchanged.
 330          * @return int The previous value
 331          */
 332         function trxLevel( $level = null ) {
 333                 return wfSetVar( $this->mTrxLevel, $level );
 334         }
 335
 336         /**
 337          * Get/set the number of errors logged. Only useful when errors are ignored
 338          * @param $count int The count to set, or omitted to leave it unchanged.
 339          * @return int The error count
 340          */
 341         function errorCount( $count = null ) {
 342                 return wfSetVar( $this->mErrorCount, $count );
 343         }
 344
 345         /**
 346          * Get/set the table prefix.
 347          * @param $prefix string The table prefix to set, or omitted to leave it unchanged.
 348          * @return string The previous table prefix.
 349          */
 350         function tablePrefix( $prefix = null ) {
 351                 return wfSetVar( $this->mTablePrefix, $prefix );
 352         }
 353
 354         /**
 355          * Get properties passed down from the server info array of the load
 356          * balancer.
 357          *
 358          * @param $name string The entry of the info array to get, or null to get the
 359          *   whole array
 360          *
 361          * @return LoadBalancer|null
 362          */
 363         function getLBInfo( $name = null ) {
 364                 if ( is_null( $name ) ) {
 365                         return $this->mLBInfo;
 366                 } else {
 367                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 368                                 return $this->mLBInfo[$name];
 369                         } else {
 370                                 return null;
 371                         }
 372                 }
 373         }
 374
 375         /**
 376          * Set the LB info array, or a member of it. If called with one parameter,
 377          * the LB info array is set to that parameter. If it is called with two
 378          * parameters, the member with the given name is set to the given value.
 379          *
 380          * @param $name
 381          * @param $value
 382          */
 383         function setLBInfo( $name, $value = null ) {
 384                 if ( is_null( $value ) ) {
 385                         $this->mLBInfo = $name;
 386                 } else {
 387                         $this->mLBInfo[$name] = $value;
 388                 }
 389         }
 390
 391         /**
 392          * Set lag time in seconds for a fake slave
 393          *
 394          * @param $lag int
 395          */
 396         function setFakeSlaveLag( $lag ) {
 397                 $this->mFakeSlaveLag = $lag;
 398         }
 399
 400         /**
 401          * Make this connection a fake master
 402          *
 403          * @param $enabled bool
 404          */
 405         function setFakeMaster( $enabled = true ) {
 406                 $this->mFakeMaster = $enabled;
 407         }
 408
 409         /**
 410          * Returns true if this database supports (and uses) cascading deletes
 411          *
 412          * @return bool
 413          */
 414         function cascadingDeletes() {
 415                 return false;
 416         }
 417
 418         /**
 419          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 420          *
 421          * @return bool
 422          */
 423         function cleanupTriggers() {
 424                 return false;
 425         }
 426
 427         /**
 428          * Returns true if this database is strict about what can be put into an IP field.
 429          * Specifically, it uses a NULL value instead of an empty string.
 430          *
 431          * @return bool
 432          */
 433         function strictIPs() {
 434                 return false;
 435         }
 436
 437         /**
 438          * Returns true if this database uses timestamps rather than integers
 439          *
 440          * @return bool
 441         */
 442         function realTimestamps() {
 443                 return false;
 444         }
 445
 446         /**
 447          * Returns true if this database does an implicit sort when doing GROUP BY
 448          *
 449          * @return bool
 450          */
 451         function implicitGroupby() {
 452                 return true;
 453         }
 454
 455         /**
 456          * Returns true if this database does an implicit order by when the column has an index
 457          * For example: SELECT page_title FROM page LIMIT 1
 458          *
 459          * @return bool
 460          */
 461         function implicitOrderby() {
 462                 return true;
 463         }
 464
 465         /**
 466          * Returns true if this database requires that SELECT DISTINCT queries require that all
 467            ORDER BY expressions occur in the SELECT list per the SQL92 standard
 468          *
 469          * @return bool
 470          */
 471         function standardSelectDistinct() {
 472                 return true;
 473         }
 474
 475         /**
 476          * Returns true if this database can do a native search on IP columns
 477          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 478          *
 479          * @return bool
 480          */
 481         function searchableIPs() {
 482                 return false;
 483         }
 484
 485         /**
 486          * Returns true if this database can use functional indexes
 487          *
 488          * @return bool
 489          */
 490         function functionalIndexes() {
 491                 return false;
 492         }
 493
 494         /**
 495          * Return the last query that went through DatabaseBase::query()
 496          * @return String
 497          */
 498         function lastQuery() {
 499                 return $this->mLastQuery;
 500         }
 501
 502         /**
 503          * Returns true if the connection may have been used for write queries.
 504          * Should return true if unsure.
 505          *
 506          * @return bool
 507          */
 508         function doneWrites() {
 509                 return $this->mDoneWrites;
 510         }
 511
 512         /**
 513          * Is a connection to the database open?
 514          * @return Boolean
 515          */
 516         function isOpen() {
 517                 return $this->mOpened;
 518         }
 519
 520         /**
 521          * Set a flag for this connection
 522          *
 523          * @param $flag Integer: DBO_* constants from Defines.php:
 524          *   - DBO_DEBUG: output some debug info (same as debug())
 525          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 526          *   - DBO_IGNORE: ignore errors (same as ignoreErrors())
 527          *   - DBO_TRX: automatically start transactions
 528          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 529          *       and removes it in command line mode
 530          *   - DBO_PERSISTENT: use persistant database connection
 531          */
 532         function setFlag( $flag ) {
 533                 global $wgDebugDBTransactions;
 534                 $this->mFlags |= $flag;
 535                 if ( ( $flag & DBO_TRX) & $wgDebugDBTransactions ) {
 536                         wfDebug("Implicit transactions are now  disabled.\n");
 537                 }
 538         }
 539
 540         /**
 541          * Clear a flag for this connection
 542          *
 543          * @param $flag: same as setFlag()'s $flag param
 544          */
 545         function clearFlag( $flag ) {
 546                 global $wgDebugDBTransactions;
 547                 $this->mFlags &= ~$flag;
 548                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 549                         wfDebug("Implicit transactions are now disabled.\n");
 550                 }
 551         }
 552
 553         /**
 554          * Returns a boolean whether the flag $flag is set for this connection
 555          *
 556          * @param $flag: same as setFlag()'s $flag param
 557          * @return Boolean
 558          */
 559         function getFlag( $flag ) {
 560                 return !!( $this->mFlags & $flag );
 561         }
 562
 563         /**
 564          * General read-only accessor
 565          *
 566          * @param $name string
 567          *
 568          * @return string
 569          */
 570         function getProperty( $name ) {
 571                 return $this->$name;
 572         }
 573
 574         /**
 575          * @return string
 576          */
 577         function getWikiID() {
 578                 if ( $this->mTablePrefix ) {
 579                         return "{$this->mDBname}-{$this->mTablePrefix}";
 580                 } else {
 581                         return $this->mDBname;
 582                 }
 583         }
 584
 585         /**
 586          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 587          *
 588          * @return string
 589          */
 590         public function getSchemaPath() {
 591                 global $IP;
 592                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 593                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 594                 } else {
 595                         return "$IP/maintenance/tables.sql";
 596                 }
 597         }
 598
 599 # ------------------------------------------------------------------------------
 600 # Other functions
 601 # ------------------------------------------------------------------------------
 602
 603         /**
 604          * Constructor.
 605          * @param $server String: database server host
 606          * @param $user String: database user name
 607          * @param $password String: database user password
 608          * @param $dbName String: database name
 609          * @param $flags
 610          * @param $tablePrefix String: database table prefixes. By default use the prefix gave in LocalSettings.php
 611          */
 612         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 613                 $flags = 0, $tablePrefix = 'get from global'
 614         ) {
 615                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 616
 617                 $this->mFlags = $flags;
 618
 619                 if ( $this->mFlags & DBO_DEFAULT ) {
 620                         if ( $wgCommandLineMode ) {
 621                                 $this->mFlags &= ~DBO_TRX;
 622                                 if ( $wgDebugDBTransactions ) {
 623                                         wfDebug("Implicit transaction open disabled.\n");
 624                                 }
 625                         } else {
 626                                 $this->mFlags |= DBO_TRX;
 627                                 if ( $wgDebugDBTransactions ) {
 628                                         wfDebug("Implicit transaction open enabled.\n");
 629                                 }
 630                         }
 631                 }
 632
 633                 /** Get the default table prefix*/
 634                 if ( $tablePrefix == 'get from global' ) {
 635                         $this->mTablePrefix = $wgDBprefix;
 636                 } else {
 637                         $this->mTablePrefix = $tablePrefix;
 638                 }
 639
 640                 if ( $user ) {
 641                         $this->open( $server, $user, $password, $dbName );
 642                 }
 643         }
 644
 645         /**
 646          * Called by serialize. Throw an exception when DB connection is serialized.
 647          * This causes problems on some database engines because the connection is
 648          * not restored on unserialize.
 649          */
 650         public function __sleep() {
 651                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 652         }
 653
 654         /**
 655          * Same as new DatabaseMysql( ... ), kept for backward compatibility
 656          * @deprecated since 1.17
 657          *
 658          * @param $server
 659          * @param $user
 660          * @param $password
 661          * @param $dbName
 662          * @param $flags int
 663          * @return DatabaseMysql
 664          */
 665         static function newFromParams( $server, $user, $password, $dbName, $flags = 0 ) {
 666                 wfDeprecated( __METHOD__, '1.17' );
 667                 return new DatabaseMysql( $server, $user, $password, $dbName, $flags );
 668         }
 669
 670         /**
 671          * Same as new factory( ... ), kept for backward compatibility
 672          * @deprecated since 1.18
 673          * @see Database::factory()
 674          * @return DatabaseBase
 675          */
 676         public final static function newFromType( $dbType, $p = array() ) {
 677                 wfDeprecated( __METHOD__, '1.18' );
 678                 if ( isset( $p['tableprefix'] ) ) {
 679                         $p['tablePrefix'] = $p['tableprefix'];
 680                 }
 681                 return self::factory( $dbType, $p );
 682         }
 683
 684         /**
 685          * Given a DB type, construct the name of the appropriate child class of
 686          * DatabaseBase. This is designed to replace all of the manual stuff like:
 687          *      $class = 'Database' . ucfirst( strtolower( $type ) );
 688          * as well as validate against the canonical list of DB types we have
 689          *
 690          * This factory function is mostly useful for when you need to connect to a
 691          * database other than the MediaWiki default (such as for external auth,
 692          * an extension, et cetera). Do not use this to connect to the MediaWiki
 693          * database. Example uses in core:
 694          * @see LoadBalancer::reallyOpenConnection()
 695          * @see ExternalUser_MediaWiki::initFromCond()
 696          * @see ForeignDBRepo::getMasterDB()
 697          * @see WebInstaller_DBConnect::execute()
 698          *
 699          * @since 1.18
 700          *
 701          * @param $dbType String A possible DB type
 702          * @param $p Array An array of options to pass to the constructor.
 703          *    Valid options are: host, user, password, dbname, flags, tablePrefix
 704          * @return DatabaseBase subclass or null
 705          */
 706         public final static function factory( $dbType, $p = array() ) {
 707                 $canonicalDBTypes = array(
 708                         'mysql', 'postgres', 'sqlite', 'oracle', 'mssql', 'ibm_db2'
 709                 );
 710                 $dbType = strtolower( $dbType );
 711                 $class = 'Database' . ucfirst( $dbType );
 712
 713                 if( in_array( $dbType, $canonicalDBTypes ) || ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) ) {
 714                         return new $class(
 715                                 isset( $p['host'] ) ? $p['host'] : false,
 716                                 isset( $p['user'] ) ? $p['user'] : false,
 717                                 isset( $p['password'] ) ? $p['password'] : false,
 718                                 isset( $p['dbname'] ) ? $p['dbname'] : false,
 719                                 isset( $p['flags'] ) ? $p['flags'] : 0,
 720                                 isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global'
 721                         );
 722                 } else {
 723                         return null;
 724                 }
 725         }
 726
 727         protected function installErrorHandler() {
 728                 $this->mPHPError = false;
 729                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 730                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 731         }
 732
 733         /**
 734          * @return bool|string
 735          */
 736         protected function restoreErrorHandler() {
 737                 restore_error_handler();
 738                 if ( $this->htmlErrors !== false ) {
 739                         ini_set( 'html_errors', $this->htmlErrors );
 740                 }
 741                 if ( $this->mPHPError ) {
 742                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 743                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 744                         return $error;
 745                 } else {
 746                         return false;
 747                 }
 748         }
 749
 750         /**
 751          * @param $errno
 752          * @param $errstr
 753          */
 754         protected function connectionErrorHandler( $errno,  $errstr ) {
 755                 $this->mPHPError = $errstr;
 756         }
 757
 758         /**
 759          * Closes a database connection.
 760          * if it is open : commits any open transactions
 761          *
 762          * @return Bool operation success. true if already closed.
 763          */
 764         public function close() {
 765                 $this->mOpened = false;
 766                 if ( $this->mConn ) {
 767                         if ( $this->trxLevel() ) {
 768                                 $this->commit( __METHOD__ );
 769                         }
 770                         $ret = $this->closeConnection();
 771                         $this->mConn = false;
 772                         return $ret;
 773                 } else {
 774                         return true;
 775                 }
 776         }
 777
 778         /**
 779          * Closes underlying database connection
 780          * @since 1.20
 781          * @return bool: Whether connection was closed successfully
 782          */
 783         protected abstract function closeConnection();
 784
 785         /**
 786          * @param $error String: fallback error message, used if none is given by DB
 787          */
 788         function reportConnectionError( $error = 'Unknown error' ) {
 789                 $myError = $this->lastError();
 790                 if ( $myError ) {
 791                         $error = $myError;
 792                 }
 793
 794                 # New method
 795                 throw new DBConnectionError( $this, $error );
 796         }
 797
 798         /**
 799          * The DBMS-dependent part of query()
 800          *
 801          * @param  $sql String: SQL query.
 802          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 803          */
 804         protected abstract function doQuery( $sql );
 805
 806         /**
 807          * Determine whether a query writes to the DB.
 808          * Should return true if unsure.
 809          *
 810          * @param $sql string
 811          *
 812          * @return bool
 813          */
 814         function isWriteQuery( $sql ) {
 815                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 816         }
 817
 818         /**
 819          * Run an SQL query and return the result. Normally throws a DBQueryError
 820          * on failure. If errors are ignored, returns false instead.
 821          *
 822          * In new code, the query wrappers select(), insert(), update(), delete(),
 823          * etc. should be used where possible, since they give much better DBMS
 824          * independence and automatically quote or validate user input in a variety
 825          * of contexts. This function is generally only useful for queries which are
 826          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 827          * as CREATE TABLE.
 828          *
 829          * However, the query wrappers themselves should call this function.
 830          *
 831          * @param  $sql        String: SQL query
 832          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 833          *     comment (you can use __METHOD__ or add some extra info)
 834          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 835          *     maybe best to catch the exception instead?
 836          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 837          *     for a successful read query, or false on failure if $tempIgnore set
 838          * @throws DBQueryError Thrown when the database returns an error of any kind
 839          */
 840         public function query( $sql, $fname = '', $tempIgnore = false ) {
 841                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 842                 if ( !Profiler::instance()->isStub() ) {
 843                         # generalizeSQL will probably cut down the query to reasonable
 844                         # logging size most of the time. The substr is really just a sanity check.
 845
 846                         if ( $isMaster ) {
 847                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 848                                 $totalProf = 'DatabaseBase::query-master';
 849                         } else {
 850                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 851                                 $totalProf = 'DatabaseBase::query';
 852                         }
 853
 854                         wfProfileIn( $totalProf );
 855                         wfProfileIn( $queryProf );
 856                 }
 857
 858                 $this->mLastQuery = $sql;
 859                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 860                         # Set a flag indicating that writes have been done
 861                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 862                         $this->mDoneWrites = true;
 863                 }
 864
 865                 # Add a comment for easy SHOW PROCESSLIST interpretation
 866                 global $wgUser;
 867                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 868                         $userName = $wgUser->getName();
 869                         if ( mb_strlen( $userName ) > 15 ) {
 870                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 871                         }
 872                         $userName = str_replace( '/', '', $userName );
 873                 } else {
 874                         $userName = '';
 875                 }
 876                 $commentedSql = preg_replace( '/\s/', " /* $fname $userName */ ", $sql, 1 );
 877
 878                 # If DBO_TRX is set, start a transaction
 879                 if ( ( $this->mFlags & DBO_TRX ) && !$this->trxLevel() &&
 880                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' ) {
 881                         # avoid establishing transactions for SHOW and SET statements too -
 882                         # that would delay transaction initializations to once connection
 883                         # is really used by application
 884                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 885                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 886                                 global $wgDebugDBTransactions;
 887                                 if ( $wgDebugDBTransactions ) {
 888                                         wfDebug("Implicit transaction start.\n");
 889                                 }
 890                                 $this->begin( __METHOD__ . " ($fname)" );
 891                         }
 892                 }
 893
 894                 if ( $this->debug() ) {
 895                         static $cnt = 0;
 896
 897                         $cnt++;
 898                         $sqlx = substr( $commentedSql, 0, 500 );
 899                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 900
 901                         $master = $isMaster ? 'master' : 'slave';
 902                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 903                 }
 904
 905                 if ( istainted( $sql ) & TC_MYSQL ) {
 906                         throw new MWException( 'Tainted query found' );
 907                 }
 908
 909                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 910
 911                 # Do the query and handle errors
 912                 $ret = $this->doQuery( $commentedSql );
 913
 914                 MWDebug::queryTime( $queryId );
 915
 916                 # Try reconnecting if the connection was lost
 917                 if ( false === $ret && $this->wasErrorReissuable() ) {
 918                         # Transaction is gone, like it or not
 919                         $this->mTrxLevel = 0;
 920                         wfDebug( "Connection lost, reconnecting...\n" );
 921
 922                         if ( $this->ping() ) {
 923                                 wfDebug( "Reconnected\n" );
 924                                 $sqlx = substr( $commentedSql, 0, 500 );
 925                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
 926                                 global $wgRequestTime;
 927                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
 928                                 if ( $elapsed < 300 ) {
 929                                         # Not a database error to lose a transaction after a minute or two
 930                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
 931                                 }
 932                                 $ret = $this->doQuery( $commentedSql );
 933                         } else {
 934                                 wfDebug( "Failed\n" );
 935                         }
 936                 }
 937
 938                 if ( false === $ret ) {
 939                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 940                 }
 941
 942                 if ( !Profiler::instance()->isStub() ) {
 943                         wfProfileOut( $queryProf );
 944                         wfProfileOut( $totalProf );
 945                 }
 946
 947                 return $this->resultObject( $ret );
 948         }
 949
 950         /**
 951          * Report a query error. Log the error, and if neither the object ignore
 952          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
 953          *
 954          * @param $error String
 955          * @param $errno Integer
 956          * @param $sql String
 957          * @param $fname String
 958          * @param $tempIgnore Boolean
 959          */
 960         function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
 961                 # Ignore errors during error handling to avoid infinite recursion
 962                 $ignore = $this->ignoreErrors( true );
 963                 ++$this->mErrorCount;
 964
 965                 if ( $ignore || $tempIgnore ) {
 966                         wfDebug( "SQL ERROR (ignored): $error\n" );
 967                         $this->ignoreErrors( $ignore );
 968                 } else {
 969                         $sql1line = str_replace( "\n", "\\n", $sql );
 970                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
 971                         wfDebug( "SQL ERROR: " . $error . "\n" );
 972                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
 973                 }
 974         }
 975
 976         /**
 977          * Intended to be compatible with the PEAR::DB wrapper functions.
 978          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
 979          *
 980          * ? = scalar value, quoted as necessary
 981          * ! = raw SQL bit (a function for instance)
 982          * & = filename; reads the file and inserts as a blob
 983          *     (we don't use this though...)
 984          *
 985          * This function should not be used directly by new code outside of the
 986          * database classes. The query wrapper functions (select() etc.) should be
 987          * used instead.
 988          *
 989          * @param $sql string
 990          * @param $func string
 991          *
 992          * @return array
 993          */
 994         function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
 995                 /* MySQL doesn't support prepared statements (yet), so just
 996                    pack up the query for reference. We'll manually replace
 997                    the bits later. */
 998                 return array( 'query' => $sql, 'func' => $func );
 999         }
1000
1001         /**
1002          * Free a prepared query, generated by prepare().
1003          * @param $prepared
1004          */
1005         function freePrepared( $prepared ) {
1006                 /* No-op by default */
1007         }
1008
1009         /**
1010          * Execute a prepared query with the various arguments
1011          * @param $prepared String: the prepared sql
1012          * @param $args Mixed: Either an array here, or put scalars as varargs
1013          *
1014          * @return ResultWrapper
1015          */
1016         function execute( $prepared, $args = null ) {
1017                 if ( !is_array( $args ) ) {
1018                         # Pull the var args
1019                         $args = func_get_args();
1020                         array_shift( $args );
1021                 }
1022
1023                 $sql = $this->fillPrepared( $prepared['query'], $args );
1024
1025                 return $this->query( $sql, $prepared['func'] );
1026         }
1027
1028         /**
1029          * Prepare & execute an SQL statement, quoting and inserting arguments
1030          * in the appropriate places.
1031          *
1032          * This function should not be used directly by new code outside of the
1033          * database classes. The query wrapper functions (select() etc.) should be
1034          * used instead.
1035          *
1036          * @param $query String
1037          * @param $args ...
1038          *
1039          * @return ResultWrapper
1040          */
1041         function safeQuery( $query, $args = null ) {
1042                 $prepared = $this->prepare( $query, 'DatabaseBase::safeQuery' );
1043
1044                 if ( !is_array( $args ) ) {
1045                         # Pull the var args
1046                         $args = func_get_args();
1047                         array_shift( $args );
1048                 }
1049
1050                 $retval = $this->execute( $prepared, $args );
1051                 $this->freePrepared( $prepared );
1052
1053                 return $retval;
1054         }
1055
1056         /**
1057          * For faking prepared SQL statements on DBs that don't support
1058          * it directly.
1059          * @param $preparedQuery String: a 'preparable' SQL statement
1060          * @param $args Array of arguments to fill it with
1061          * @return string executable SQL
1062          */
1063         function fillPrepared( $preparedQuery, $args ) {
1064                 reset( $args );
1065                 $this->preparedArgs =& $args;
1066
1067                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1068                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1069         }
1070
1071         /**
1072          * preg_callback func for fillPrepared()
1073          * The arguments should be in $this->preparedArgs and must not be touched
1074          * while we're doing this.
1075          *
1076          * @param $matches Array
1077          * @return String
1078          */
1079         function fillPreparedArg( $matches ) {
1080                 switch( $matches[1] ) {
1081                         case '\\?': return '?';
1082                         case '\\!': return '!';
1083                         case '\\&': return '&';
1084                 }
1085
1086                 list( /* $n */ , $arg ) = each( $this->preparedArgs );
1087
1088                 switch( $matches[1] ) {
1089                         case '?': return $this->addQuotes( $arg );
1090                         case '!': return $arg;
1091                         case '&':
1092                                 # return $this->addQuotes( file_get_contents( $arg ) );
1093                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1094                         default:
1095                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1096                 }
1097         }
1098
1099         /**
1100          * Free a result object returned by query() or select(). It's usually not
1101          * necessary to call this, just use unset() or let the variable holding
1102          * the result object go out of scope.
1103          *
1104          * @param $res Mixed: A SQL result
1105          */
1106         function freeResult( $res ) {
1107         }
1108
1109         /**
1110          * Simple UPDATE wrapper.
1111          * Usually throws a DBQueryError on failure.
1112          * If errors are explicitly ignored, returns success
1113          *
1114          * This function exists for historical reasons, DatabaseBase::update() has a more standard
1115          * calling convention and feature set
1116          *
1117          * @param $table string
1118          * @param $var
1119          * @param $value
1120          * @param $cond
1121          * @param $fname string
1122          *
1123          * @return bool
1124          */
1125         function set( $table, $var, $value, $cond, $fname = 'DatabaseBase::set' ) {
1126                 $table = $this->tableName( $table );
1127                 $sql = "UPDATE $table SET $var = '" .
1128                   $this->strencode( $value ) . "' WHERE ($cond)";
1129
1130                 return (bool)$this->query( $sql, $fname );
1131         }
1132
1133         /**
1134          * A SELECT wrapper which returns a single field from a single result row.
1135          *
1136          * Usually throws a DBQueryError on failure. If errors are explicitly
1137          * ignored, returns false on failure.
1138          *
1139          * If no result rows are returned from the query, false is returned.
1140          *
1141          * @param $table string|array Table name. See DatabaseBase::select() for details.
1142          * @param $var string The field name to select. This must be a valid SQL
1143          *   fragment: do not use unvalidated user input.
1144          * @param $cond string|array The condition array. See DatabaseBase::select() for details.
1145          * @param $fname string The function name of the caller.
1146          * @param $options string|array The query options. See DatabaseBase::select() for details.
1147          *
1148          * @return bool|mixed The value from the field, or false on failure.
1149          */
1150         function selectField( $table, $var, $cond = '', $fname = 'DatabaseBase::selectField',
1151                 $options = array() )
1152         {
1153                 if ( !is_array( $options ) ) {
1154                         $options = array( $options );
1155                 }
1156
1157                 $options['LIMIT'] = 1;
1158
1159                 $res = $this->select( $table, $var, $cond, $fname, $options );
1160
1161                 if ( $res === false || !$this->numRows( $res ) ) {
1162                         return false;
1163                 }
1164
1165                 $row = $this->fetchRow( $res );
1166
1167                 if ( $row !== false ) {
1168                         return reset( $row );
1169                 } else {
1170                         return false;
1171                 }
1172         }
1173
1174         /**
1175          * Returns an optional USE INDEX clause to go after the table, and a
1176          * string to go at the end of the query.
1177          *
1178          * @param $options Array: associative array of options to be turned into
1179          *              an SQL query, valid keys are listed in the function.
1180          * @return Array
1181          * @see DatabaseBase::select()
1182          */
1183         function makeSelectOptions( $options ) {
1184                 $preLimitTail = $postLimitTail = '';
1185                 $startOpts = '';
1186
1187                 $noKeyOptions = array();
1188
1189                 foreach ( $options as $key => $option ) {
1190                         if ( is_numeric( $key ) ) {
1191                                 $noKeyOptions[$option] = true;
1192                         }
1193                 }
1194
1195                 if ( isset( $options['GROUP BY'] ) ) {
1196                         $gb = is_array( $options['GROUP BY'] )
1197                                 ? implode( ',', $options['GROUP BY'] )
1198                                 : $options['GROUP BY'];
1199                         $preLimitTail .= " GROUP BY {$gb}";
1200                 }
1201
1202                 if ( isset( $options['HAVING'] ) ) {
1203                         $preLimitTail .= " HAVING {$options['HAVING']}";
1204                 }
1205
1206                 if ( isset( $options['ORDER BY'] ) ) {
1207                         $ob = is_array( $options['ORDER BY'] )
1208                                 ? implode( ',', $options['ORDER BY'] )
1209                                 : $options['ORDER BY'];
1210                         $preLimitTail .= " ORDER BY {$ob}";
1211                 }
1212
1213                 // if (isset($options['LIMIT'])) {
1214                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1215                 //              isset($options['OFFSET']) ? $options['OFFSET']
1216                 //              : false);
1217                 // }
1218
1219                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1220                         $postLimitTail .= ' FOR UPDATE';
1221                 }
1222
1223                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1224                         $postLimitTail .= ' LOCK IN SHARE MODE';
1225                 }
1226
1227                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1228                         $startOpts .= 'DISTINCT';
1229                 }
1230
1231                 # Various MySQL extensions
1232                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1233                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1234                 }
1235
1236                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1237                         $startOpts .= ' HIGH_PRIORITY';
1238                 }
1239
1240                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1241                         $startOpts .= ' SQL_BIG_RESULT';
1242                 }
1243
1244                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1245                         $startOpts .= ' SQL_BUFFER_RESULT';
1246                 }
1247
1248                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1249                         $startOpts .= ' SQL_SMALL_RESULT';
1250                 }
1251
1252                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1253                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1254                 }
1255
1256                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1257                         $startOpts .= ' SQL_CACHE';
1258                 }
1259
1260                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1261                         $startOpts .= ' SQL_NO_CACHE';
1262                 }
1263
1264                 if ( isset( $options['USE INDEX'] ) && ! is_array( $options['USE INDEX'] ) ) {
1265                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1266                 } else {
1267                         $useIndex = '';
1268                 }
1269
1270                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1271         }
1272
1273         /**
1274          * Execute a SELECT query constructed using the various parameters provided.
1275          * See below for full details of the parameters.
1276          *
1277          * @param $table String|Array Table name
1278          * @param $vars String|Array Field names
1279          * @param $conds String|Array Conditions
1280          * @param $fname String Caller function name
1281          * @param $options Array Query options
1282          * @param $join_conds Array Join conditions
1283          *
1284          * @param $table string|array
1285          *
1286          * May be either an array of table names, or a single string holding a table
1287          * name. If an array is given, table aliases can be specified, for example:
1288          *
1289          *    array( 'a' => 'user' )
1290          *
1291          * This includes the user table in the query, with the alias "a" available
1292          * for use in field names (e.g. a.user_name).
1293          *
1294          * All of the table names given here are automatically run through
1295          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1296          * added, and various other table name mappings to be performed.
1297          *
1298          *
1299          * @param $vars string|array
1300          *
1301          * May be either a field name or an array of field names. The field names
1302          * here are complete fragments of SQL, for direct inclusion into the SELECT
1303          * query. Expressions and aliases may be specified as in SQL, for example:
1304          *
1305          *   array( 'MAX(rev_id) AS maxrev' )
1306          *
1307          * If an expression is given, care must be taken to ensure that it is
1308          * DBMS-independent.
1309          *
1310          *
1311          * @param $conds string|array
1312          *
1313          * May be either a string containing a single condition, or an array of
1314          * conditions. If an array is given, the conditions constructed from each
1315          * element are combined with AND.
1316          *
1317          * Array elements may take one of two forms:
1318          *
1319          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1320          *   - Elements with a string key are interpreted as equality conditions,
1321          *     where the key is the field name.
1322          *     - If the value of such an array element is a scalar (such as a
1323          *       string), it will be treated as data and thus quoted appropriately.
1324          *       If it is null, an IS NULL clause will be added.
1325          *     - If the value is an array, an IN(...) clause will be constructed,
1326          *       such that the field name may match any of the elements in the
1327          *       array. The elements of the array will be quoted.
1328          *
1329          * Note that expressions are often DBMS-dependent in their syntax.
1330          * DBMS-independent wrappers are provided for constructing several types of
1331          * expression commonly used in condition queries. See:
1332          *    - DatabaseBase::buildLike()
1333          *    - DatabaseBase::conditional()
1334          *
1335          *
1336          * @param $options string|array
1337          *
1338          * Optional: Array of query options. Boolean options are specified by
1339          * including them in the array as a string value with a numeric key, for
1340          * example:
1341          *
1342          *    array( 'FOR UPDATE' )
1343          *
1344          * The supported options are:
1345          *
1346          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1347          *     with LIMIT can theoretically be used for paging through a result set,
1348          *     but this is discouraged in MediaWiki for performance reasons.
1349          *
1350          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1351          *     and then the first rows are taken until the limit is reached. LIMIT
1352          *     is applied to a result set after OFFSET.
1353          *
1354          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1355          *     changed until the next COMMIT.
1356          *
1357          *   - DISTINCT: Boolean: return only unique result rows.
1358          *
1359          *   - GROUP BY: May be either an SQL fragment string naming a field or
1360          *     expression to group by, or an array of such SQL fragments.
1361          *
1362          *   - HAVING: A string containing a HAVING clause.
1363          *
1364          *   - ORDER BY: May be either an SQL fragment giving a field name or
1365          *     expression to order by, or an array of such SQL fragments.
1366          *
1367          *   - USE INDEX: This may be either a string giving the index name to use
1368          *     for the query, or an array. If it is an associative array, each key
1369          *     gives the table name (or alias), each value gives the index name to
1370          *     use for that table. All strings are SQL fragments and so should be
1371          *     validated by the caller.
1372          *
1373          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1374          *     instead of SELECT.
1375          *
1376          * And also the following boolean MySQL extensions, see the MySQL manual
1377          * for documentation:
1378          *
1379          *    - LOCK IN SHARE MODE
1380          *    - STRAIGHT_JOIN
1381          *    - HIGH_PRIORITY
1382          *    - SQL_BIG_RESULT
1383          *    - SQL_BUFFER_RESULT
1384          *    - SQL_SMALL_RESULT
1385          *    - SQL_CALC_FOUND_ROWS
1386          *    - SQL_CACHE
1387          *    - SQL_NO_CACHE
1388          *
1389          *
1390          * @param $join_conds string|array
1391          *
1392          * Optional associative array of table-specific join conditions. In the
1393          * most common case, this is unnecessary, since the join condition can be
1394          * in $conds. However, it is useful for doing a LEFT JOIN.
1395          *
1396          * The key of the array contains the table name or alias. The value is an
1397          * array with two elements, numbered 0 and 1. The first gives the type of
1398          * join, the second is an SQL fragment giving the join condition for that
1399          * table. For example:
1400          *
1401          *    array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
1402          *
1403          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1404          *   with no rows in it will be returned. If there was a query error, a
1405          *   DBQueryError exception will be thrown, except if the "ignore errors"
1406          *   option was set, in which case false will be returned.
1407          */
1408         function select( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1409                 $options = array(), $join_conds = array() ) {
1410                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1411
1412                 return $this->query( $sql, $fname );
1413         }
1414
1415         /**
1416          * The equivalent of DatabaseBase::select() except that the constructed SQL
1417          * is returned, instead of being immediately executed.
1418          *
1419          * @param $table string|array Table name
1420          * @param $vars string|array Field names
1421          * @param $conds string|array Conditions
1422          * @param $fname string Caller function name
1423          * @param $options string|array Query options
1424          * @param $join_conds string|array Join conditions
1425          *
1426          * @return string SQL query string.
1427          * @see DatabaseBase::select()
1428          */
1429         function selectSQLText( $table, $vars, $conds = '', $fname = 'DatabaseBase::select', $options = array(), $join_conds = array() ) {
1430                 if ( is_array( $vars ) ) {
1431                         $vars = implode( ',', $vars );
1432                 }
1433
1434                 $options = (array)$options;
1435
1436                 if ( is_array( $table ) ) {
1437                         $useIndex = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1438                                 ? $options['USE INDEX']
1439                                 : array();
1440                         if ( count( $join_conds ) || count( $useIndex ) ) {
1441                                 $from = ' FROM ' .
1442                                         $this->tableNamesWithUseIndexOrJOIN( $table, $useIndex, $join_conds );
1443                         } else {
1444                                 $from = ' FROM ' . implode( ',', $this->tableNamesWithAlias( $table ) );
1445                         }
1446                 } elseif ( $table != '' ) {
1447                         if ( $table[0] == ' ' ) {
1448                                 $from = ' FROM ' . $table;
1449                         } else {
1450                                 $from = ' FROM ' . $this->tableName( $table );
1451                         }
1452                 } else {
1453                         $from = '';
1454                 }
1455
1456                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) = $this->makeSelectOptions( $options );
1457
1458                 if ( !empty( $conds ) ) {
1459                         if ( is_array( $conds ) ) {
1460                                 $conds = $this->makeList( $conds, LIST_AND );
1461                         }
1462                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1463                 } else {
1464                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1465                 }
1466
1467                 if ( isset( $options['LIMIT'] ) ) {
1468                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1469                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1470                 }
1471                 $sql = "$sql $postLimitTail";
1472
1473                 if ( isset( $options['EXPLAIN'] ) ) {
1474                         $sql = 'EXPLAIN ' . $sql;
1475                 }
1476
1477                 return $sql;
1478         }
1479
1480         /**
1481          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1482          * that a single row object is returned. If the query returns no rows,
1483          * false is returned.
1484          *
1485          * @param $table string|array Table name
1486          * @param $vars string|array Field names
1487          * @param $conds array Conditions
1488          * @param $fname string Caller function name
1489          * @param $options string|array Query options
1490          * @param $join_conds array|string Join conditions
1491          *
1492          * @return object|bool
1493          */
1494         function selectRow( $table, $vars, $conds, $fname = 'DatabaseBase::selectRow',
1495                 $options = array(), $join_conds = array() )
1496         {
1497                 $options = (array)$options;
1498                 $options['LIMIT'] = 1;
1499                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1500
1501                 if ( $res === false ) {
1502                         return false;
1503                 }
1504
1505                 if ( !$this->numRows( $res ) ) {
1506                         return false;
1507                 }
1508
1509                 $obj = $this->fetchObject( $res );
1510
1511                 return $obj;
1512         }
1513
1514         /**
1515          * Estimate rows in dataset.
1516          *
1517          * MySQL allows you to estimate the number of rows that would be returned
1518          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1519          * index cardinality statistics, and is notoriously inaccurate, especially
1520          * when large numbers of rows have recently been added or deleted.
1521          *
1522          * For DBMSs that don't support fast result size estimation, this function
1523          * will actually perform the SELECT COUNT(*).
1524          *
1525          * Takes the same arguments as DatabaseBase::select().
1526          *
1527          * @param $table String: table name
1528          * @param Array|string $vars : unused
1529          * @param Array|string $conds : filters on the table
1530          * @param $fname String: function name for profiling
1531          * @param $options Array: options for select
1532          * @return Integer: row count
1533          */
1534         public function estimateRowCount( $table, $vars = '*', $conds = '',
1535                 $fname = 'DatabaseBase::estimateRowCount', $options = array() )
1536         {
1537                 $rows = 0;
1538                 $res = $this->select ( $table, 'COUNT(*) AS rowcount', $conds, $fname, $options );
1539
1540                 if ( $res ) {
1541                         $row = $this->fetchRow( $res );
1542                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1543                 }
1544
1545                 return $rows;
1546         }
1547
1548         /**
1549          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1550          * It's only slightly flawed. Don't use for anything important.
1551          *
1552          * @param $sql String A SQL Query
1553          *
1554          * @return string
1555          */
1556         static function generalizeSQL( $sql ) {
1557                 # This does the same as the regexp below would do, but in such a way
1558                 # as to avoid crashing php on some large strings.
1559                 # $sql = preg_replace ( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql);
1560
1561                 $sql = str_replace ( "\\\\", '', $sql );
1562                 $sql = str_replace ( "\\'", '', $sql );
1563                 $sql = str_replace ( "\\\"", '', $sql );
1564                 $sql = preg_replace ( "/'.*'/s", "'X'", $sql );
1565                 $sql = preg_replace ( '/".*"/s', "'X'", $sql );
1566
1567                 # All newlines, tabs, etc replaced by single space
1568                 $sql = preg_replace ( '/\s+/', ' ', $sql );
1569
1570                 # All numbers => N
1571                 $sql = preg_replace ( '/-?[0-9]+/s', 'N', $sql );
1572
1573                 return $sql;
1574         }
1575
1576         /**
1577          * Determines whether a field exists in a table
1578          *
1579          * @param $table String: table name
1580          * @param $field String: filed to check on that table
1581          * @param $fname String: calling function name (optional)
1582          * @return Boolean: whether $table has filed $field
1583          */
1584         function fieldExists( $table, $field, $fname = 'DatabaseBase::fieldExists' ) {
1585                 $info = $this->fieldInfo( $table, $field );
1586
1587                 return (bool)$info;
1588         }
1589
1590         /**
1591          * Determines whether an index exists
1592          * Usually throws a DBQueryError on failure
1593          * If errors are explicitly ignored, returns NULL on failure
1594          *
1595          * @param $table
1596          * @param $index
1597          * @param $fname string
1598          *
1599          * @return bool|null
1600          */
1601         function indexExists( $table, $index, $fname = 'DatabaseBase::indexExists' ) {
1602                 $info = $this->indexInfo( $table, $index, $fname );
1603                 if ( is_null( $info ) ) {
1604                         return null;
1605                 } else {
1606                         return $info !== false;
1607                 }
1608         }
1609
1610         /**
1611          * Query whether a given table exists
1612          *
1613          * @param $table string
1614          * @param $fname string
1615          *
1616          * @return bool
1617          */
1618         function tableExists( $table, $fname = __METHOD__ ) {
1619                 $table = $this->tableName( $table );
1620                 $old = $this->ignoreErrors( true );
1621                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1622                 $this->ignoreErrors( $old );
1623
1624                 return (bool)$res;
1625         }
1626
1627         /**
1628          * mysql_field_type() wrapper
1629          * @param $res
1630          * @param $index
1631          * @return string
1632          */
1633         function fieldType( $res, $index ) {
1634                 if ( $res instanceof ResultWrapper ) {
1635                         $res = $res->result;
1636                 }
1637
1638                 return mysql_field_type( $res, $index );
1639         }
1640
1641         /**
1642          * Determines if a given index is unique
1643          *
1644          * @param $table string
1645          * @param $index string
1646          *
1647          * @return bool
1648          */
1649         function indexUnique( $table, $index ) {
1650                 $indexInfo = $this->indexInfo( $table, $index );
1651
1652                 if ( !$indexInfo ) {
1653                         return null;
1654                 }
1655
1656                 return !$indexInfo[0]->Non_unique;
1657         }
1658
1659         /**
1660          * Helper for DatabaseBase::insert().
1661          *
1662          * @param $options array
1663          * @return string
1664          */
1665         function makeInsertOptions( $options ) {
1666                 return implode( ' ', $options );
1667         }
1668
1669         /**
1670          * INSERT wrapper, inserts an array into a table.
1671          *
1672          * $a may be either:
1673          *
1674          *   - A single associative array. The array keys are the field names, and
1675          *     the values are the values to insert. The values are treated as data
1676          *     and will be quoted appropriately. If NULL is inserted, this will be
1677          *     converted to a database NULL.
1678          *   - An array with numeric keys, holding a list of associative arrays.
1679          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1680          *     each subarray must be identical to each other, and in the same order.
1681          *
1682          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1683          * returns success.
1684          *
1685          * $options is an array of options, with boolean options encoded as values
1686          * with numeric keys, in the same style as $options in
1687          * DatabaseBase::select(). Supported options are:
1688          *
1689          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1690          *     any rows which cause duplicate key errors are not inserted. It's
1691          *     possible to determine how many rows were successfully inserted using
1692          *     DatabaseBase::affectedRows().
1693          *
1694          * @param $table   String Table name. This will be passed through
1695          *                 DatabaseBase::tableName().
1696          * @param $a       Array of rows to insert
1697          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1698          * @param $options Array of options
1699          *
1700          * @return bool
1701          */
1702         function insert( $table, $a, $fname = 'DatabaseBase::insert', $options = array() ) {
1703                 # No rows to insert, easy just return now
1704                 if ( !count( $a ) ) {
1705                         return true;
1706                 }
1707
1708                 $table = $this->tableName( $table );
1709
1710                 if ( !is_array( $options ) ) {
1711                         $options = array( $options );
1712                 }
1713
1714                 $options = $this->makeInsertOptions( $options );
1715
1716                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1717                         $multi = true;
1718                         $keys = array_keys( $a[0] );
1719                 } else {
1720                         $multi = false;
1721                         $keys = array_keys( $a );
1722                 }
1723
1724                 $sql = 'INSERT ' . $options .
1725                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1726
1727                 if ( $multi ) {
1728                         $first = true;
1729                         foreach ( $a as $row ) {
1730                                 if ( $first ) {
1731                                         $first = false;
1732                                 } else {
1733                                         $sql .= ',';
1734                                 }
1735                                 $sql .= '(' . $this->makeList( $row ) . ')';
1736                         }
1737                 } else {
1738                         $sql .= '(' . $this->makeList( $a ) . ')';
1739                 }
1740
1741                 return (bool)$this->query( $sql, $fname );
1742         }
1743
1744         /**
1745          * Make UPDATE options for the DatabaseBase::update function
1746          *
1747          * @param $options Array: The options passed to DatabaseBase::update
1748          * @return string
1749          */
1750         function makeUpdateOptions( $options ) {
1751                 if ( !is_array( $options ) ) {
1752                         $options = array( $options );
1753                 }
1754
1755                 $opts = array();
1756
1757                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1758                         $opts[] = $this->lowPriorityOption();
1759                 }
1760
1761                 if ( in_array( 'IGNORE', $options ) ) {
1762                         $opts[] = 'IGNORE';
1763                 }
1764
1765                 return implode( ' ', $opts );
1766         }
1767
1768         /**
1769          * UPDATE wrapper. Takes a condition array and a SET array.
1770          *
1771          * @param $table  String name of the table to UPDATE. This will be passed through
1772          *                DatabaseBase::tableName().
1773          *
1774          * @param $values Array:  An array of values to SET. For each array element,
1775          *                the key gives the field name, and the value gives the data
1776          *                to set that field to. The data will be quoted by
1777          *                DatabaseBase::addQuotes().
1778          *
1779          * @param $conds  Array:  An array of conditions (WHERE). See
1780          *                DatabaseBase::select() for the details of the format of
1781          *                condition arrays. Use '*' to update all rows.
1782          *
1783          * @param $fname  String: The function name of the caller (from __METHOD__),
1784          *                for logging and profiling.
1785          *
1786          * @param $options Array: An array of UPDATE options, can be:
1787          *                   - IGNORE: Ignore unique key conflicts
1788          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1789          * @return Boolean
1790          */
1791         function update( $table, $values, $conds, $fname = 'DatabaseBase::update', $options = array() ) {
1792                 $table = $this->tableName( $table );
1793                 $opts = $this->makeUpdateOptions( $options );
1794                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1795
1796                 if ( $conds !== array() && $conds !== '*' ) {
1797                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1798                 }
1799
1800                 return $this->query( $sql, $fname );
1801         }
1802
1803         /**
1804          * Makes an encoded list of strings from an array
1805          * @param $a Array containing the data
1806          * @param $mode int Constant
1807          *      - LIST_COMMA:          comma separated, no field names
1808          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1809          *        the documentation for $conds in DatabaseBase::select().
1810          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1811          *      - LIST_SET:            comma separated with field names, like a SET clause
1812          *      - LIST_NAMES:          comma separated field names
1813          *
1814          * @return string
1815          */
1816         function makeList( $a, $mode = LIST_COMMA ) {
1817                 if ( !is_array( $a ) ) {
1818                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1819                 }
1820
1821                 $first = true;
1822                 $list = '';
1823
1824                 foreach ( $a as $field => $value ) {
1825                         if ( !$first ) {
1826                                 if ( $mode == LIST_AND ) {
1827                                         $list .= ' AND ';
1828                                 } elseif ( $mode == LIST_OR ) {
1829                                         $list .= ' OR ';
1830                                 } else {
1831                                         $list .= ',';
1832                                 }
1833                         } else {
1834                                 $first = false;
1835                         }
1836
1837                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1838                                 $list .= "($value)";
1839                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1840                                 $list .= "$value";
1841                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1842                                 if ( count( $value ) == 0 ) {
1843                                         throw new MWException( __METHOD__ . ': empty input' );
1844                                 } elseif ( count( $value ) == 1 ) {
1845                                         // Special-case single values, as IN isn't terribly efficient
1846                                         // Don't necessarily assume the single key is 0; we don't
1847                                         // enforce linear numeric ordering on other arrays here.
1848                                         $value = array_values( $value );
1849                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1850                                 } else {
1851                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1852                                 }
1853                         } elseif ( $value === null ) {
1854                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1855                                         $list .= "$field IS ";
1856                                 } elseif ( $mode == LIST_SET ) {
1857                                         $list .= "$field = ";
1858                                 }
1859                                 $list .= 'NULL';
1860                         } else {
1861                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1862                                         $list .= "$field = ";
1863                                 }
1864                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1865                         }
1866                 }
1867
1868                 return $list;
1869         }
1870
1871         /**
1872          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1873          * The keys on each level may be either integers or strings.
1874          *
1875          * @param $data Array: organized as 2-d
1876          *              array(baseKeyVal => array(subKeyVal => <ignored>, ...), ...)
1877          * @param $baseKey String: field name to match the base-level keys to (eg 'pl_namespace')
1878          * @param $subKey String: field name to match the sub-level keys to (eg 'pl_title')
1879          * @return Mixed: string SQL fragment, or false if no items in array.
1880          */
1881         function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1882                 $conds = array();
1883
1884                 foreach ( $data as $base => $sub ) {
1885                         if ( count( $sub ) ) {
1886                                 $conds[] = $this->makeList(
1887                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1888                                         LIST_AND );
1889                         }
1890                 }
1891
1892                 if ( $conds ) {
1893                         return $this->makeList( $conds, LIST_OR );
1894                 } else {
1895                         // Nothing to search for...
1896                         return false;
1897                 }
1898         }
1899
1900         /**
1901          * Bitwise operations
1902          */
1903
1904         /**
1905          * @param $field
1906          * @return string
1907          */
1908         function bitNot( $field ) {
1909                 return "(~$field)";
1910         }
1911
1912         /**
1913          * @param $fieldLeft
1914          * @param $fieldRight
1915          * @return string
1916          */
1917         function bitAnd( $fieldLeft, $fieldRight ) {
1918                 return "($fieldLeft & $fieldRight)";
1919         }
1920
1921         /**
1922          * @param  $fieldLeft
1923          * @param  $fieldRight
1924          * @return string
1925          */
1926         function bitOr( $fieldLeft, $fieldRight ) {
1927                 return "($fieldLeft | $fieldRight)";
1928         }
1929
1930         /**
1931          * Change the current database
1932          *
1933          * @todo Explain what exactly will fail if this is not overridden.
1934          *
1935          * @param $db
1936          *
1937          * @return bool Success or failure
1938          */
1939         function selectDB( $db ) {
1940                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
1941                 # if your database engine supports a concept similar to MySQL's
1942                 # databases you may as well.
1943                 $this->mDBname = $db;
1944                 return true;
1945         }
1946
1947         /**
1948          * Get the current DB name
1949          */
1950         function getDBname() {
1951                 return $this->mDBname;
1952         }
1953
1954         /**
1955          * Get the server hostname or IP address
1956          */
1957         function getServer() {
1958                 return $this->mServer;
1959         }
1960
1961         /**
1962          * Format a table name ready for use in constructing an SQL query
1963          *
1964          * This does two important things: it quotes the table names to clean them up,
1965          * and it adds a table prefix if only given a table name with no quotes.
1966          *
1967          * All functions of this object which require a table name call this function
1968          * themselves. Pass the canonical name to such functions. This is only needed
1969          * when calling query() directly.
1970          *
1971          * @param $name String: database table name
1972          * @param $format String One of:
1973          *   quoted - Automatically pass the table name through addIdentifierQuotes()
1974          *            so that it can be used in a query.
1975          *   raw - Do not add identifier quotes to the table name
1976          * @return String: full database name
1977          */
1978         function tableName( $name, $format = 'quoted' ) {
1979                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
1980                 # Skip the entire process when we have a string quoted on both ends.
1981                 # Note that we check the end so that we will still quote any use of
1982                 # use of `database`.table. But won't break things if someone wants
1983                 # to query a database table with a dot in the name.
1984                 if ( $this->isQuotedIdentifier( $name ) ) {
1985                         return $name;
1986                 }
1987
1988                 # Lets test for any bits of text that should never show up in a table
1989                 # name. Basically anything like JOIN or ON which are actually part of
1990                 # SQL queries, but may end up inside of the table value to combine
1991                 # sql. Such as how the API is doing.
1992                 # Note that we use a whitespace test rather than a \b test to avoid
1993                 # any remote case where a word like on may be inside of a table name
1994                 # surrounded by symbols which may be considered word breaks.
1995                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1996                         return $name;
1997                 }
1998
1999                 # Split database and table into proper variables.
2000                 # We reverse the explode so that database.table and table both output
2001                 # the correct table.
2002                 $dbDetails = array_reverse( explode( '.', $name, 2 ) );
2003                 if ( isset( $dbDetails[1] ) ) {
2004                         list( $table, $database ) = $dbDetails;
2005                 } else {
2006                         list( $table ) = $dbDetails;
2007                 }
2008                 $prefix = $this->mTablePrefix; # Default prefix
2009
2010                 # A database name has been specified in input. We don't want any
2011                 # prefixes added.
2012                 if ( isset( $database ) ) {
2013                         $prefix = '';
2014                 }
2015
2016                 # Note that we use the long format because php will complain in in_array if
2017                 # the input is not an array, and will complain in is_array if it is not set.
2018                 if ( !isset( $database ) # Don't use shared database if pre selected.
2019                  && isset( $wgSharedDB ) # We have a shared database
2020                  && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
2021                  && isset( $wgSharedTables )
2022                  && is_array( $wgSharedTables )
2023                  && in_array( $table, $wgSharedTables ) ) { # A shared table is selected
2024                         $database = $wgSharedDB;
2025                         $prefix   = isset( $wgSharedPrefix ) ? $wgSharedPrefix : $prefix;
2026                 }
2027
2028                 # Quote the $database and $table and apply the prefix if not quoted.
2029                 if ( isset( $database ) ) {
2030                         $database = ( $format == 'quoted' || $this->isQuotedIdentifier( $database ) ? $database : $this->addIdentifierQuotes( $database ) );
2031                 }
2032
2033                 $table = "{$prefix}{$table}";
2034                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $table ) ) {
2035                         $table = $this->addIdentifierQuotes( "{$table}" );
2036                 }
2037
2038                 # Merge our database and table into our final table name.
2039                 $tableName = ( isset( $database ) ? "{$database}.{$table}" : "{$table}" );
2040
2041                 return $tableName;
2042         }
2043
2044         /**
2045          * Fetch a number of table names into an array
2046          * This is handy when you need to construct SQL for joins
2047          *
2048          * Example:
2049          * extract($dbr->tableNames('user','watchlist'));
2050          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2051          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2052          *
2053          * @return array
2054          */
2055         public function tableNames() {
2056                 $inArray = func_get_args();
2057                 $retVal = array();
2058
2059                 foreach ( $inArray as $name ) {
2060                         $retVal[$name] = $this->tableName( $name );
2061                 }
2062
2063                 return $retVal;
2064         }
2065
2066         /**
2067          * Fetch a number of table names into an zero-indexed numerical array
2068          * This is handy when you need to construct SQL for joins
2069          *
2070          * Example:
2071          * list( $user, $watchlist ) = $dbr->tableNamesN('user','watchlist');
2072          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2073          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2074          *
2075          * @return array
2076          */
2077         public function tableNamesN() {
2078                 $inArray = func_get_args();
2079                 $retVal = array();
2080
2081                 foreach ( $inArray as $name ) {
2082                         $retVal[] = $this->tableName( $name );
2083                 }
2084
2085                 return $retVal;
2086         }
2087
2088         /**
2089          * Get an aliased table name
2090          * e.g. tableName AS newTableName
2091          *
2092          * @param $name string Table name, see tableName()
2093          * @param $alias string|bool Alias (optional)
2094          * @return string SQL name for aliased table. Will not alias a table to its own name
2095          */
2096         public function tableNameWithAlias( $name, $alias = false ) {
2097                 if ( !$alias || $alias == $name ) {
2098                         return $this->tableName( $name );
2099                 } else {
2100                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2101                 }
2102         }
2103
2104         /**
2105          * Gets an array of aliased table names
2106          *
2107          * @param $tables array( [alias] => table )
2108          * @return array of strings, see tableNameWithAlias()
2109          */
2110         public function tableNamesWithAlias( $tables ) {
2111                 $retval = array();
2112                 foreach ( $tables as $alias => $table ) {
2113                         if ( is_numeric( $alias ) ) {
2114                                 $alias = $table;
2115                         }
2116                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2117                 }
2118                 return $retval;
2119         }
2120
2121         /**
2122          * Get the aliased table name clause for a FROM clause
2123          * which might have a JOIN and/or USE INDEX clause
2124          *
2125          * @param $tables array ( [alias] => table )
2126          * @param $use_index array Same as for select()
2127          * @param $join_conds array Same as for select()
2128          * @return string
2129          */
2130         protected function tableNamesWithUseIndexOrJOIN(
2131                 $tables, $use_index = array(), $join_conds = array()
2132         ) {
2133                 $ret = array();
2134                 $retJOIN = array();
2135                 $use_index = (array)$use_index;
2136                 $join_conds = (array)$join_conds;
2137
2138                 foreach ( $tables as $alias => $table ) {
2139                         if ( !is_string( $alias ) ) {
2140                                 // No alias? Set it equal to the table name
2141                                 $alias = $table;
2142                         }
2143                         // Is there a JOIN clause for this table?
2144                         if ( isset( $join_conds[$alias] ) ) {
2145                                 list( $joinType, $conds ) = $join_conds[$alias];
2146                                 $tableClause = $joinType;
2147                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2148                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2149                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2150                                         if ( $use != '' ) {
2151                                                 $tableClause .= ' ' . $use;
2152                                         }
2153                                 }
2154                                 $on = $this->makeList( (array)$conds, LIST_AND );
2155                                 if ( $on != '' ) {
2156                                         $tableClause .= ' ON (' . $on . ')';
2157                                 }
2158
2159                                 $retJOIN[] = $tableClause;
2160                         // Is there an INDEX clause for this table?
2161                         } elseif ( isset( $use_index[$alias] ) ) {
2162                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2163                                 $tableClause .= ' ' . $this->useIndexClause(
2164                                         implode( ',', (array)$use_index[$alias] ) );
2165
2166                                 $ret[] = $tableClause;
2167                         } else {
2168                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2169
2170                                 $ret[] = $tableClause;
2171                         }
2172                 }
2173
2174                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2175                 $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2176                 $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2177
2178                 // Compile our final table clause
2179                 return implode( ' ', array( $straightJoins, $otherJoins ) );
2180         }
2181
2182         /**
2183          * Get the name of an index in a given table
2184          *
2185          * @param $index
2186          *
2187          * @return string
2188          */
2189         function indexName( $index ) {
2190                 // Backwards-compatibility hack
2191                 $renamed = array(
2192                         'ar_usertext_timestamp' => 'usertext_timestamp',
2193                         'un_user_id'            => 'user_id',
2194                         'un_user_ip'            => 'user_ip',
2195                 );
2196
2197                 if ( isset( $renamed[$index] ) ) {
2198                         return $renamed[$index];
2199                 } else {
2200                         return $index;
2201                 }
2202         }
2203
2204         /**
2205          * If it's a string, adds quotes and backslashes
2206          * Otherwise returns as-is
2207          *
2208          * @param $s string
2209          *
2210          * @return string
2211          */
2212         function addQuotes( $s ) {
2213                 if ( $s === null ) {
2214                         return 'NULL';
2215                 } else {
2216                         # This will also quote numeric values. This should be harmless,
2217                         # and protects against weird problems that occur when they really
2218                         # _are_ strings such as article titles and string->number->string
2219                         # conversion is not 1:1.
2220                         return "'" . $this->strencode( $s ) . "'";
2221                 }
2222         }
2223
2224         /**
2225          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2226          * MySQL uses `backticks` while basically everything else uses double quotes.
2227          * Since MySQL is the odd one out here the double quotes are our generic
2228          * and we implement backticks in DatabaseMysql.
2229          *
2230          * @param $s string
2231          *
2232          * @return string
2233          */
2234         public function addIdentifierQuotes( $s ) {
2235                 return '"' . str_replace( '"', '""', $s ) . '"';
2236         }
2237
2238         /**
2239          * Returns if the given identifier looks quoted or not according to
2240          * the database convention for quoting identifiers .
2241          *
2242          * @param $name string
2243          *
2244          * @return boolean
2245          */
2246         public function isQuotedIdentifier( $name ) {
2247                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2248         }
2249
2250         /**
2251          * Backwards compatibility, identifier quoting originated in DatabasePostgres
2252          * which used quote_ident which does not follow our naming conventions
2253          * was renamed to addIdentifierQuotes.
2254          * @deprecated since 1.18 use addIdentifierQuotes
2255          *
2256          * @param $s string
2257          *
2258          * @return string
2259          */
2260         function quote_ident( $s ) {
2261                 wfDeprecated( __METHOD__, '1.18' );
2262                 return $this->addIdentifierQuotes( $s );
2263         }
2264
2265         /**
2266          * Escape string for safe LIKE usage.
2267          * WARNING: you should almost never use this function directly,
2268          * instead use buildLike() that escapes everything automatically
2269          * @deprecated since 1.17, warnings in 1.17, removed in ???
2270          *
2271          * @param $s string
2272          *
2273          * @return string
2274          */
2275         public function escapeLike( $s ) {
2276                 wfDeprecated( __METHOD__, '1.17' );
2277                 return $this->escapeLikeInternal( $s );
2278         }
2279
2280         /**
2281          * @param $s string
2282          * @return string
2283          */
2284         protected function escapeLikeInternal( $s ) {
2285                 $s = str_replace( '\\', '\\\\', $s );
2286                 $s = $this->strencode( $s );
2287                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2288
2289                 return $s;
2290         }
2291
2292         /**
2293          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2294          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2295          * Alternatively, the function could be provided with an array of aforementioned parameters.
2296          *
2297          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2298          * for subpages of 'My page title'.
2299          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2300          *
2301          * @since 1.16
2302          * @return String: fully built LIKE statement
2303          */
2304         function buildLike() {
2305                 $params = func_get_args();
2306
2307                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2308                         $params = $params[0];
2309                 }
2310
2311                 $s = '';
2312
2313                 foreach ( $params as $value ) {
2314                         if ( $value instanceof LikeMatch ) {
2315                                 $s .= $value->toString();
2316                         } else {
2317                                 $s .= $this->escapeLikeInternal( $value );
2318                         }
2319                 }
2320
2321                 return " LIKE '" . $s . "' ";
2322         }
2323
2324         /**
2325          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2326          *
2327          * @return LikeMatch
2328          */
2329         function anyChar() {
2330                 return new LikeMatch( '_' );
2331         }
2332
2333         /**
2334          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2335          *
2336          * @return LikeMatch
2337          */
2338         function anyString() {
2339                 return new LikeMatch( '%' );
2340         }
2341
2342         /**
2343          * Returns an appropriately quoted sequence value for inserting a new row.
2344          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2345          * subclass will return an integer, and save the value for insertId()
2346          *
2347          * Any implementation of this function should *not* involve reusing
2348          * sequence numbers created for rolled-back transactions.
2349          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2350          * @param $seqName string
2351          * @return null
2352          */
2353         function nextSequenceValue( $seqName ) {
2354                 return null;
2355         }
2356
2357         /**
2358          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2359          * is only needed because a) MySQL must be as efficient as possible due to
2360          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2361          * which index to pick.  Anyway, other databases might have different
2362          * indexes on a given table.  So don't bother overriding this unless you're
2363          * MySQL.
2364          * @param $index
2365          * @return string
2366          */
2367         function useIndexClause( $index ) {
2368                 return '';
2369         }
2370
2371         /**
2372          * REPLACE query wrapper.
2373          *
2374          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2375          * except that when there is a duplicate key error, the old row is deleted
2376          * and the new row is inserted in its place.
2377          *
2378          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2379          * perform the delete, we need to know what the unique indexes are so that
2380          * we know how to find the conflicting rows.
2381          *
2382          * It may be more efficient to leave off unique indexes which are unlikely
2383          * to collide. However if you do this, you run the risk of encountering
2384          * errors which wouldn't have occurred in MySQL.
2385          *
2386          * @param $table String: The table to replace the row(s) in.
2387          * @param $rows array Can be either a single row to insert, or multiple rows,
2388          *    in the same format as for DatabaseBase::insert()
2389          * @param $uniqueIndexes array is an array of indexes. Each element may be either
2390          *    a field name or an array of field names
2391          * @param $fname String: Calling function name (use __METHOD__) for logs/profiling
2392          */
2393         function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseBase::replace' ) {
2394                 $quotedTable = $this->tableName( $table );
2395
2396                 if ( count( $rows ) == 0 ) {
2397                         return;
2398                 }
2399
2400                 # Single row case
2401                 if ( !is_array( reset( $rows ) ) ) {
2402                         $rows = array( $rows );
2403                 }
2404
2405                 foreach( $rows as $row ) {
2406                         # Delete rows which collide
2407                         if ( $uniqueIndexes ) {
2408                                 $sql = "DELETE FROM $quotedTable WHERE ";
2409                                 $first = true;
2410                                 foreach ( $uniqueIndexes as $index ) {
2411                                         if ( $first ) {
2412                                                 $first = false;
2413                                                 $sql .= '( ';
2414                                         } else {
2415                                                 $sql .= ' ) OR ( ';
2416                                         }
2417                                         if ( is_array( $index ) ) {
2418                                                 $first2 = true;
2419                                                 foreach ( $index as $col ) {
2420                                                         if ( $first2 ) {
2421                                                                 $first2 = false;
2422                                                         } else {
2423                                                                 $sql .= ' AND ';
2424                                                         }
2425                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2426                                                 }
2427                                         } else {
2428                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2429                                         }
2430                                 }
2431                                 $sql .= ' )';
2432                                 $this->query( $sql, $fname );
2433                         }
2434
2435                         # Now insert the row
2436                         $this->insert( $table, $row );
2437                 }
2438         }
2439
2440         /**
2441          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2442          * statement.
2443          *
2444          * @param $table string Table name
2445          * @param $rows array Rows to insert
2446          * @param $fname string Caller function name
2447          *
2448          * @return ResultWrapper
2449          */
2450         protected function nativeReplace( $table, $rows, $fname ) {
2451                 $table = $this->tableName( $table );
2452
2453                 # Single row case
2454                 if ( !is_array( reset( $rows ) ) ) {
2455                         $rows = array( $rows );
2456                 }
2457
2458                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2459                 $first = true;
2460
2461                 foreach ( $rows as $row ) {
2462                         if ( $first ) {
2463                                 $first = false;
2464                         } else {
2465                                 $sql .= ',';
2466                         }
2467
2468                         $sql .= '(' . $this->makeList( $row ) . ')';
2469                 }
2470
2471                 return $this->query( $sql, $fname );
2472         }
2473
2474         /**
2475          * DELETE where the condition is a join.
2476          *
2477          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2478          * we use sub-selects
2479          *
2480          * For safety, an empty $conds will not delete everything. If you want to
2481          * delete all rows where the join condition matches, set $conds='*'.
2482          *
2483          * DO NOT put the join condition in $conds.
2484          *
2485          * @param $delTable   String: The table to delete from.
2486          * @param $joinTable  String: The other table.
2487          * @param $delVar     String: The variable to join on, in the first table.
2488          * @param $joinVar    String: The variable to join on, in the second table.
2489          * @param $conds      Array: Condition array of field names mapped to variables,
2490          *                    ANDed together in the WHERE clause
2491          * @param $fname      String: Calling function name (use __METHOD__) for
2492          *                    logs/profiling
2493          */
2494         function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2495                 $fname = 'DatabaseBase::deleteJoin' )
2496         {
2497                 if ( !$conds ) {
2498                         throw new DBUnexpectedError( $this,
2499                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2500                 }
2501
2502                 $delTable = $this->tableName( $delTable );
2503                 $joinTable = $this->tableName( $joinTable );
2504                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2505                 if ( $conds != '*' ) {
2506                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2507                 }
2508                 $sql .= ')';
2509
2510                 $this->query( $sql, $fname );
2511         }
2512
2513         /**
2514          * Returns the size of a text field, or -1 for "unlimited"
2515          *
2516          * @param $table string
2517          * @param $field string
2518          *
2519          * @return int
2520          */
2521         function textFieldSize( $table, $field ) {
2522                 $table = $this->tableName( $table );
2523                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2524                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2525                 $row = $this->fetchObject( $res );
2526
2527                 $m = array();
2528
2529                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2530                         $size = $m[1];
2531                 } else {
2532                         $size = -1;
2533                 }
2534
2535                 return $size;
2536         }
2537
2538         /**
2539          * A string to insert into queries to show that they're low-priority, like
2540          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2541          * string and nothing bad should happen.
2542          *
2543          * @return string Returns the text of the low priority option if it is
2544          *   supported, or a blank string otherwise
2545          */
2546         function lowPriorityOption() {
2547                 return '';
2548         }
2549
2550         /**
2551          * DELETE query wrapper.
2552          *
2553          * @param $table Array Table name
2554          * @param $conds String|Array of conditions. See $conds in DatabaseBase::select() for
2555          *               the format. Use $conds == "*" to delete all rows
2556          * @param $fname String name of the calling function
2557          *
2558          * @return bool
2559          */
2560         function delete( $table, $conds, $fname = 'DatabaseBase::delete' ) {
2561                 if ( !$conds ) {
2562                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2563                 }
2564
2565                 $table = $this->tableName( $table );
2566                 $sql = "DELETE FROM $table";
2567
2568                 if ( $conds != '*' ) {
2569                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2570                 }
2571
2572                 return $this->query( $sql, $fname );
2573         }
2574
2575         /**
2576          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2577          * into another table.
2578          *
2579          * @param $destTable string The table name to insert into
2580          * @param $srcTable string|array May be either a table name, or an array of table names
2581          *    to include in a join.
2582          *
2583          * @param $varMap array must be an associative array of the form
2584          *    array( 'dest1' => 'source1', ...). Source items may be literals
2585          *    rather than field names, but strings should be quoted with
2586          *    DatabaseBase::addQuotes()
2587          *
2588          * @param $conds array Condition array. See $conds in DatabaseBase::select() for
2589          *    the details of the format of condition arrays. May be "*" to copy the
2590          *    whole table.
2591          *
2592          * @param $fname string The function name of the caller, from __METHOD__
2593          *
2594          * @param $insertOptions array Options for the INSERT part of the query, see
2595          *    DatabaseBase::insert() for details.
2596          * @param $selectOptions array Options for the SELECT part of the query, see
2597          *    DatabaseBase::select() for details.
2598          *
2599          * @return ResultWrapper
2600          */
2601         function insertSelect( $destTable, $srcTable, $varMap, $conds,
2602                 $fname = 'DatabaseBase::insertSelect',
2603                 $insertOptions = array(), $selectOptions = array() )
2604         {
2605                 $destTable = $this->tableName( $destTable );
2606
2607                 if ( is_array( $insertOptions ) ) {
2608                         $insertOptions = implode( ' ', $insertOptions );
2609                 }
2610
2611                 if ( !is_array( $selectOptions ) ) {
2612                         $selectOptions = array( $selectOptions );
2613                 }
2614
2615                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2616
2617                 if ( is_array( $srcTable ) ) {
2618                         $srcTable =  implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2619                 } else {
2620                         $srcTable = $this->tableName( $srcTable );
2621                 }
2622
2623                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2624                         " SELECT $startOpts " . implode( ',', $varMap ) .
2625                         " FROM $srcTable $useIndex ";
2626
2627                 if ( $conds != '*' ) {
2628                         if ( is_array( $conds ) ) {
2629                                 $conds = $this->makeList( $conds, LIST_AND );
2630                         }
2631                         $sql .= " WHERE $conds";
2632                 }
2633
2634                 $sql .= " $tailOpts";
2635
2636                 return $this->query( $sql, $fname );
2637         }
2638
2639         /**
2640          * Construct a LIMIT query with optional offset.  This is used for query
2641          * pages.  The SQL should be adjusted so that only the first $limit rows
2642          * are returned.  If $offset is provided as well, then the first $offset
2643          * rows should be discarded, and the next $limit rows should be returned.
2644          * If the result of the query is not ordered, then the rows to be returned
2645          * are theoretically arbitrary.
2646          *
2647          * $sql is expected to be a SELECT, if that makes a difference.  For
2648          * UPDATE, limitResultForUpdate should be used.
2649          *
2650          * The version provided by default works in MySQL and SQLite.  It will very
2651          * likely need to be overridden for most other DBMSes.
2652          *
2653          * @param $sql String SQL query we will append the limit too
2654          * @param $limit Integer the SQL limit
2655          * @param $offset Integer|bool the SQL offset (default false)
2656          *
2657          * @return string
2658          */
2659         function limitResult( $sql, $limit, $offset = false ) {
2660                 if ( !is_numeric( $limit ) ) {
2661                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2662                 }
2663
2664                 return "$sql LIMIT "
2665                                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2666                                 . "{$limit} ";
2667         }
2668
2669         /**
2670          * @param $sql
2671          * @param $num
2672          * @return string
2673          */
2674         function limitResultForUpdate( $sql, $num ) {
2675                 return $this->limitResult( $sql, $num, 0 );
2676         }
2677
2678         /**
2679          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2680          * within the UNION construct.
2681          * @return Boolean
2682          */
2683         function unionSupportsOrderAndLimit() {
2684                 return true; // True for almost every DB supported
2685         }
2686
2687         /**
2688          * Construct a UNION query
2689          * This is used for providing overload point for other DB abstractions
2690          * not compatible with the MySQL syntax.
2691          * @param $sqls Array: SQL statements to combine
2692          * @param $all Boolean: use UNION ALL
2693          * @return String: SQL fragment
2694          */
2695         function unionQueries( $sqls, $all ) {
2696                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2697                 return '(' . implode( $glue, $sqls ) . ')';
2698         }
2699
2700         /**
2701          * Returns an SQL expression for a simple conditional.  This doesn't need
2702          * to be overridden unless CASE isn't supported in your DBMS.
2703          *
2704          * @param $cond String: SQL expression which will result in a boolean value
2705          * @param $trueVal String: SQL expression to return if true
2706          * @param $falseVal String: SQL expression to return if false
2707          * @return String: SQL fragment
2708          */
2709         function conditional( $cond, $trueVal, $falseVal ) {
2710                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2711         }
2712
2713         /**
2714          * Returns a comand for str_replace function in SQL query.
2715          * Uses REPLACE() in MySQL
2716          *
2717          * @param $orig String: column to modify
2718          * @param $old String: column to seek
2719          * @param $new String: column to replace with
2720          *
2721          * @return string
2722          */
2723         function strreplace( $orig, $old, $new ) {
2724                 return "REPLACE({$orig}, {$old}, {$new})";
2725         }
2726
2727         /**
2728          * Determines how long the server has been up
2729          * STUB
2730          *
2731          * @return int
2732          */
2733         function getServerUptime() {
2734                 return 0;
2735         }
2736
2737         /**
2738          * Determines if the last failure was due to a deadlock
2739          * STUB
2740          *
2741          * @return bool
2742          */
2743         function wasDeadlock() {
2744                 return false;
2745         }
2746
2747         /**
2748          * Determines if the last failure was due to a lock timeout
2749          * STUB
2750          *
2751          * @return bool
2752          */
2753         function wasLockTimeout() {
2754                 return false;
2755         }
2756
2757         /**
2758          * Determines if the last query error was something that should be dealt
2759          * with by pinging the connection and reissuing the query.
2760          * STUB
2761          *
2762          * @return bool
2763          */
2764         function wasErrorReissuable() {
2765                 return false;
2766         }
2767
2768         /**
2769          * Determines if the last failure was due to the database being read-only.
2770          * STUB
2771          *
2772          * @return bool
2773          */
2774         function wasReadOnlyError() {
2775                 return false;
2776         }
2777
2778         /**
2779          * Perform a deadlock-prone transaction.
2780          *
2781          * This function invokes a callback function to perform a set of write
2782          * queries. If a deadlock occurs during the processing, the transaction
2783          * will be rolled back and the callback function will be called again.
2784          *
2785          * Usage:
2786          *   $dbw->deadlockLoop( callback, ... );
2787          *
2788          * Extra arguments are passed through to the specified callback function.
2789          *
2790          * Returns whatever the callback function returned on its successful,
2791          * iteration, or false on error, for example if the retry limit was
2792          * reached.
2793          *
2794          * @return bool
2795          */
2796         function deadlockLoop() {
2797
2798                 $this->begin( __METHOD__ );
2799                 $args = func_get_args();
2800                 $function = array_shift( $args );
2801                 $oldIgnore = $this->ignoreErrors( true );
2802                 $tries = DEADLOCK_TRIES;
2803
2804                 if ( is_array( $function ) ) {
2805                         $fname = $function[0];
2806                 } else {
2807                         $fname = $function;
2808                 }
2809
2810                 do {
2811                         $retVal = call_user_func_array( $function, $args );
2812                         $error = $this->lastError();
2813                         $errno = $this->lastErrno();
2814                         $sql = $this->lastQuery();
2815
2816                         if ( $errno ) {
2817                                 if ( $this->wasDeadlock() ) {
2818                                         # Retry
2819                                         usleep( mt_rand( DEADLOCK_DELAY_MIN, DEADLOCK_DELAY_MAX ) );
2820                                 } else {
2821                                         $this->reportQueryError( $error, $errno, $sql, $fname );
2822                                 }
2823                         }
2824                 } while ( $this->wasDeadlock() && --$tries > 0 );
2825
2826                 $this->ignoreErrors( $oldIgnore );
2827
2828                 if ( $tries <= 0 ) {
2829                         $this->rollback( __METHOD__ );
2830                         $this->reportQueryError( $error, $errno, $sql, $fname );
2831                         return false;
2832                 } else {
2833                         $this->commit( __METHOD__ );
2834                         return $retVal;
2835                 }
2836         }
2837
2838         /**
2839          * Wait for the slave to catch up to a given master position.
2840          *
2841          * @param $pos DBMasterPos object
2842          * @param $timeout Integer: the maximum number of seconds to wait for
2843          *   synchronisation
2844          *
2845          * @return integer: zero if the slave was past that position already,
2846          *   greater than zero if we waited for some period of time, less than
2847          *   zero if we timed out.
2848          */
2849         function masterPosWait( DBMasterPos $pos, $timeout ) {
2850                 wfProfileIn( __METHOD__ );
2851
2852                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2853                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
2854
2855                         if ( $wait > $timeout * 1e6 ) {
2856                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
2857                                 wfProfileOut( __METHOD__ );
2858                                 return -1;
2859                         } elseif ( $wait > 0 ) {
2860                                 wfDebug( "Fake slave waiting $wait us\n" );
2861                                 usleep( $wait );
2862                                 wfProfileOut( __METHOD__ );
2863                                 return 1;
2864                         } else {
2865                                 wfDebug( "Fake slave up to date ($wait us)\n" );
2866                                 wfProfileOut( __METHOD__ );
2867                                 return 0;
2868                         }
2869                 }
2870
2871                 wfProfileOut( __METHOD__ );
2872
2873                 # Real waits are implemented in the subclass.
2874                 return 0;
2875         }
2876
2877         /**
2878          * Get the replication position of this slave
2879          *
2880          * @return DBMasterPos, or false if this is not a slave.
2881          */
2882         function getSlavePos() {
2883                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2884                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
2885                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
2886                         return $pos;
2887                 } else {
2888                         # Stub
2889                         return false;
2890                 }
2891         }
2892
2893         /**
2894          * Get the position of this master
2895          *
2896          * @return DBMasterPos, or false if this is not a master
2897          */
2898         function getMasterPos() {
2899                 if ( $this->mFakeMaster ) {
2900                         return new MySQLMasterPos( 'fake', microtime( true ) );
2901                 } else {
2902                         return false;
2903                 }
2904         }
2905
2906         /**
2907          * Begin a transaction
2908          *
2909          * @param $fname string
2910          */
2911         function begin( $fname = 'DatabaseBase::begin' ) {
2912                 $this->query( 'BEGIN', $fname );
2913                 $this->mTrxLevel = 1;
2914         }
2915
2916         /**
2917          * End a transaction
2918          *
2919          * @param $fname string
2920          */
2921         function commit( $fname = 'DatabaseBase::commit' ) {
2922                 if ( $this->mTrxLevel ) {
2923                         $this->query( 'COMMIT', $fname );
2924                         $this->mTrxLevel = 0;
2925                 }
2926         }
2927
2928         /**
2929          * Rollback a transaction.
2930          * No-op on non-transactional databases.
2931          *
2932          * @param $fname string
2933          */
2934         function rollback( $fname = 'DatabaseBase::rollback' ) {
2935                 if ( $this->mTrxLevel ) {
2936                         $this->query( 'ROLLBACK', $fname, true );
2937                         $this->mTrxLevel = 0;
2938                 }
2939         }
2940
2941         /**
2942          * Creates a new table with structure copied from existing table
2943          * Note that unlike most database abstraction functions, this function does not
2944          * automatically append database prefix, because it works at a lower
2945          * abstraction level.
2946          * The table names passed to this function shall not be quoted (this
2947          * function calls addIdentifierQuotes when needed).
2948          *
2949          * @param $oldName String: name of table whose structure should be copied
2950          * @param $newName String: name of table to be created
2951          * @param $temporary Boolean: whether the new table should be temporary
2952          * @param $fname String: calling function name
2953          * @return Boolean: true if operation was successful
2954          */
2955         function duplicateTableStructure( $oldName, $newName, $temporary = false,
2956                 $fname = 'DatabaseBase::duplicateTableStructure' )
2957         {
2958                 throw new MWException(
2959                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
2960         }
2961
2962         /**
2963          * List all tables on the database
2964          *
2965          * @param $prefix string Only show tables with this prefix, e.g. mw_
2966          * @param $fname String: calling function name
2967          */
2968         function listTables( $prefix = null, $fname = 'DatabaseBase::listTables' ) {
2969                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
2970         }
2971
2972         /**
2973          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2974          * to the format used for inserting into timestamp fields in this DBMS.
2975          *
2976          * The result is unquoted, and needs to be passed through addQuotes()
2977          * before it can be included in raw SQL.
2978          *
2979          * @param $ts string|int
2980          *
2981          * @return string
2982          */
2983         function timestamp( $ts = 0 ) {
2984                 return wfTimestamp( TS_MW, $ts );
2985         }
2986
2987         /**
2988          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2989          * to the format used for inserting into timestamp fields in this DBMS. If
2990          * NULL is input, it is passed through, allowing NULL values to be inserted
2991          * into timestamp fields.
2992          *
2993          * The result is unquoted, and needs to be passed through addQuotes()
2994          * before it can be included in raw SQL.
2995          *
2996          * @param $ts string|int
2997          *
2998          * @return string
2999          */
3000         function timestampOrNull( $ts = null ) {
3001                 if ( is_null( $ts ) ) {
3002                         return null;
3003                 } else {
3004                         return $this->timestamp( $ts );
3005                 }
3006         }
3007
3008         /**
3009          * Take the result from a query, and wrap it in a ResultWrapper if
3010          * necessary. Boolean values are passed through as is, to indicate success
3011          * of write queries or failure.
3012          *
3013          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3014          * resource, and it was necessary to call this function to convert it to
3015          * a wrapper. Nowadays, raw database objects are never exposed to external
3016          * callers, so this is unnecessary in external code. For compatibility with
3017          * old code, ResultWrapper objects are passed through unaltered.
3018          *
3019          * @param $result bool|ResultWrapper
3020          *
3021          * @return bool|ResultWrapper
3022          */
3023         function resultObject( $result ) {
3024                 if ( empty( $result ) ) {
3025                         return false;
3026                 } elseif ( $result instanceof ResultWrapper ) {
3027                         return $result;
3028                 } elseif ( $result === true ) {
3029                         // Successful write query
3030                         return $result;
3031                 } else {
3032                         return new ResultWrapper( $this, $result );
3033                 }
3034         }
3035
3036         /**
3037          * Return aggregated value alias
3038          *
3039          * @param $valuedata
3040          * @param $valuename string
3041          *
3042          * @return string
3043          */
3044         function aggregateValue ( $valuedata, $valuename = 'value' ) {
3045                 return $valuename;
3046         }
3047
3048         /**
3049          * Ping the server and try to reconnect if it there is no connection
3050          *
3051          * @return bool Success or failure
3052          */
3053         function ping() {
3054                 # Stub.  Not essential to override.
3055                 return true;
3056         }
3057
3058         /**
3059          * Get slave lag. Currently supported only by MySQL.
3060          *
3061          * Note that this function will generate a fatal error on many
3062          * installations. Most callers should use LoadBalancer::safeGetLag()
3063          * instead.
3064          *
3065          * @return int Database replication lag in seconds
3066          */
3067         function getLag() {
3068                 return intval( $this->mFakeSlaveLag );
3069         }
3070
3071         /**
3072          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3073          *
3074          * @return int
3075          */
3076         function maxListLen() {
3077                 return 0;
3078         }
3079
3080         /**
3081          * Some DBMSs have a special format for inserting into blob fields, they
3082          * don't allow simple quoted strings to be inserted. To insert into such
3083          * a field, pass the data through this function before passing it to
3084          * DatabaseBase::insert().
3085          * @param $b string
3086          * @return string
3087          */
3088         function encodeBlob( $b ) {
3089                 return $b;
3090         }
3091
3092         /**
3093          * Some DBMSs return a special placeholder object representing blob fields
3094          * in result objects. Pass the object through this function to return the
3095          * original string.
3096          * @param $b string
3097          * @return string
3098          */
3099         function decodeBlob( $b ) {
3100                 return $b;
3101         }
3102
3103         /**
3104          * Override database's default connection timeout
3105          *
3106          * @param $timeout Integer in seconds
3107          * @return void
3108          * @deprecated since 1.19; use setSessionOptions()
3109          */
3110         public function setTimeout( $timeout ) {
3111                 wfDeprecated( __METHOD__, '1.19' );
3112                 $this->setSessionOptions( array( 'connTimeout' => $timeout ) );
3113         }
3114
3115         /**
3116          * Override database's default behavior. $options include:
3117          *     'connTimeout' : Set the connection timeout value in seconds.
3118          *                     May be useful for very long batch queries such as
3119          *                     full-wiki dumps, where a single query reads out over
3120          *                     hours or days.
3121          *
3122          * @param $options Array
3123          * @return void
3124          */
3125         public function setSessionOptions( array $options ) {}
3126
3127         /**
3128          * Read and execute SQL commands from a file.
3129          *
3130          * Returns true on success, error string or exception on failure (depending
3131          * on object's error ignore settings).
3132          *
3133          * @param $filename String: File name to open
3134          * @param $lineCallback Callback: Optional function called before reading each line
3135          * @param $resultCallback Callback: Optional function called for each MySQL result
3136          * @param $fname String: Calling function name or false if name should be
3137          *      generated dynamically using $filename
3138          * @return bool|string
3139          */
3140         function sourceFile( $filename, $lineCallback = false, $resultCallback = false, $fname = false ) {
3141                 wfSuppressWarnings();
3142                 $fp = fopen( $filename, 'r' );
3143                 wfRestoreWarnings();
3144
3145                 if ( false === $fp ) {
3146                         throw new MWException( "Could not open \"{$filename}\".\n" );
3147                 }
3148
3149                 if ( !$fname ) {
3150                         $fname = __METHOD__ . "( $filename )";
3151                 }
3152
3153                 try {
3154                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname );
3155                 }
3156                 catch ( MWException $e ) {
3157                         fclose( $fp );
3158                         throw $e;
3159                 }
3160
3161                 fclose( $fp );
3162
3163                 return $error;
3164         }
3165
3166         /**
3167          * Get the full path of a patch file. Originally based on archive()
3168          * from updaters.inc. Keep in mind this always returns a patch, as
3169          * it fails back to MySQL if no DB-specific patch can be found
3170          *
3171          * @param $patch String The name of the patch, like patch-something.sql
3172          * @return String Full path to patch file
3173          */
3174         public function patchPath( $patch ) {
3175                 global $IP;
3176
3177                 $dbType = $this->getType();
3178                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3179                         return "$IP/maintenance/$dbType/archives/$patch";
3180                 } else {
3181                         return "$IP/maintenance/archives/$patch";
3182                 }
3183         }
3184
3185         /**
3186          * Set variables to be used in sourceFile/sourceStream, in preference to the
3187          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3188          * all. If it's set to false, $GLOBALS will be used.
3189          *
3190          * @param $vars bool|array mapping variable name to value.
3191          */
3192         function setSchemaVars( $vars ) {
3193                 $this->mSchemaVars = $vars;
3194         }
3195
3196         /**
3197          * Read and execute commands from an open file handle.
3198          *
3199          * Returns true on success, error string or exception on failure (depending
3200          * on object's error ignore settings).
3201          *
3202          * @param $fp Resource: File handle
3203          * @param $lineCallback Callback: Optional function called before reading each line
3204          * @param $resultCallback Callback: Optional function called for each MySQL result
3205          * @param $fname String: Calling function name
3206          * @param $inputCallback Callback: Optional function called for each complete line (ended with ;) sent
3207          * @return bool|string
3208          */
3209         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3210                 $fname = 'DatabaseBase::sourceStream', $inputCallback = false )
3211         {
3212                 $cmd = '';
3213
3214                 while ( !feof( $fp ) ) {
3215                         if ( $lineCallback ) {
3216                                 call_user_func( $lineCallback );
3217                         }
3218
3219                         $line = trim( fgets( $fp ) );
3220
3221                         if ( $line == '' ) {
3222                                 continue;
3223                         }
3224
3225                         if ( '-' == $line[0] && '-' == $line[1] ) {
3226                                 continue;
3227                         }
3228
3229                         if ( $cmd != '' ) {
3230                                 $cmd .= ' ';
3231                         }
3232
3233                         $done = $this->streamStatementEnd( $cmd, $line );
3234
3235                         $cmd .= "$line\n";
3236
3237                         if ( $done || feof( $fp ) ) {
3238                                 $cmd = $this->replaceVars( $cmd );
3239                                 if ( $inputCallback ) {
3240                                         call_user_func( $inputCallback, $cmd );
3241                                 }
3242                                 $res = $this->query( $cmd, $fname );
3243
3244                                 if ( $resultCallback ) {
3245                                         call_user_func( $resultCallback, $res, $this );
3246                                 }
3247
3248                                 if ( false === $res ) {
3249                                         $err = $this->lastError();
3250                                         return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3251                                 }
3252
3253                                 $cmd = '';
3254                         }
3255                 }
3256
3257                 return true;
3258         }
3259
3260         /**
3261          * Called by sourceStream() to check if we've reached a statement end
3262          *
3263          * @param $sql String SQL assembled so far
3264          * @param $newLine String New line about to be added to $sql
3265          * @return Bool Whether $newLine contains end of the statement
3266          */
3267         public function streamStatementEnd( &$sql, &$newLine ) {
3268                 if ( $this->delimiter ) {
3269                         $prev = $newLine;
3270                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3271                         if ( $newLine != $prev ) {
3272                                 return true;
3273                         }
3274                 }
3275                 return false;
3276         }
3277
3278         /**
3279          * Database independent variable replacement. Replaces a set of variables
3280          * in an SQL statement with their contents as given by $this->getSchemaVars().
3281          *
3282          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3283          *
3284          * - '{$var}' should be used for text and is passed through the database's
3285          *   addQuotes method.
3286          * - `{$var}` should be used for identifiers (eg: table and database names),
3287          *   it is passed through the database's addIdentifierQuotes method which
3288          *   can be overridden if the database uses something other than backticks.
3289          * - / *$var* / is just encoded, besides traditional table prefix and
3290          *   table options its use should be avoided.
3291          *
3292          * @param $ins String: SQL statement to replace variables in
3293          * @return String The new SQL statement with variables replaced
3294          */
3295         protected function replaceSchemaVars( $ins ) {
3296                 $vars = $this->getSchemaVars();
3297                 foreach ( $vars as $var => $value ) {
3298                         // replace '{$var}'
3299                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3300                         // replace `{$var}`
3301                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3302                         // replace /*$var*/
3303                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ) , $ins );
3304                 }
3305                 return $ins;
3306         }
3307
3308         /**
3309          * Replace variables in sourced SQL
3310          *
3311          * @param $ins string
3312          *
3313          * @return string
3314          */
3315         protected function replaceVars( $ins ) {
3316                 $ins = $this->replaceSchemaVars( $ins );
3317
3318                 // Table prefixes
3319                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3320                         array( $this, 'tableNameCallback' ), $ins );
3321
3322                 // Index names
3323                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3324                         array( $this, 'indexNameCallback' ), $ins );
3325
3326                 return $ins;
3327         }
3328
3329         /**
3330          * Get schema variables. If none have been set via setSchemaVars(), then
3331          * use some defaults from the current object.
3332          *
3333          * @return array
3334          */
3335         protected function getSchemaVars() {
3336                 if ( $this->mSchemaVars ) {
3337                         return $this->mSchemaVars;
3338                 } else {
3339                         return $this->getDefaultSchemaVars();
3340                 }
3341         }
3342
3343         /**
3344          * Get schema variables to use if none have been set via setSchemaVars().
3345          *
3346          * Override this in derived classes to provide variables for tables.sql
3347          * and SQL patch files.
3348          *
3349          * @return array
3350          */
3351         protected function getDefaultSchemaVars() {
3352                 return array();
3353         }
3354
3355         /**
3356          * Table name callback
3357          *
3358          * @param $matches array
3359          *
3360          * @return string
3361          */
3362         protected function tableNameCallback( $matches ) {
3363                 return $this->tableName( $matches[1] );
3364         }
3365
3366         /**
3367          * Index name callback
3368          *
3369          * @param $matches array
3370          *
3371          * @return string
3372          */
3373         protected function indexNameCallback( $matches ) {
3374                 return $this->indexName( $matches[1] );
3375         }
3376
3377         /**
3378          * Build a concatenation list to feed into a SQL query
3379          * @param $stringList Array: list of raw SQL expressions; caller is responsible for any quoting
3380          * @return String
3381          */
3382         function buildConcat( $stringList ) {
3383                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
3384         }
3385
3386         /**
3387          * Check to see if a named lock is available. This is non-blocking.
3388          *
3389          * @param $lockName String: name of lock to poll
3390          * @param $method String: name of method calling us
3391          * @return Boolean
3392          * @since 1.20
3393          */
3394         public function lockIsFree( $lockName, $method ) {
3395                 return true;
3396         }
3397
3398         /**
3399          * Acquire a named lock
3400          *
3401          * Abstracted from Filestore::lock() so child classes can implement for
3402          * their own needs.
3403          *
3404          * @param $lockName String: name of lock to aquire
3405          * @param $method String: name of method calling us
3406          * @param $timeout Integer: timeout
3407          * @return Boolean
3408          */
3409         public function lock( $lockName, $method, $timeout = 5 ) {
3410                 return true;
3411         }
3412
3413         /**
3414          * Release a lock.
3415          *
3416          * @param $lockName String: Name of lock to release
3417          * @param $method String: Name of method calling us
3418          *
3419          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3420          * by this thread (in which case the lock is not released), and NULL if the named
3421          * lock did not exist
3422          */
3423         public function unlock( $lockName, $method ) {
3424                 return true;
3425         }
3426
3427         /**
3428          * Lock specific tables
3429          *
3430          * @param $read Array of tables to lock for read access
3431          * @param $write Array of tables to lock for write access
3432          * @param $method String name of caller
3433          * @param $lowPriority bool Whether to indicate writes to be LOW PRIORITY
3434          *
3435          * @return bool
3436          */
3437         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3438                 return true;
3439         }
3440
3441         /**
3442          * Unlock specific tables
3443          *
3444          * @param $method String the caller
3445          *
3446          * @return bool
3447          */
3448         public function unlockTables( $method ) {
3449                 return true;
3450         }
3451
3452         /**
3453          * Delete a table
3454          * @param $tableName string
3455          * @param $fName string
3456          * @return bool|ResultWrapper
3457          * @since 1.18
3458          */
3459         public function dropTable( $tableName, $fName = 'DatabaseBase::dropTable' ) {
3460                 if( !$this->tableExists( $tableName, $fName ) ) {
3461                         return false;
3462                 }
3463                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3464                 if( $this->cascadingDeletes() ) {
3465                         $sql .= " CASCADE";
3466                 }
3467                 return $this->query( $sql, $fName );
3468         }
3469
3470         /**
3471          * Get search engine class. All subclasses of this need to implement this
3472          * if they wish to use searching.
3473          *
3474          * @return String
3475          */
3476         public function getSearchEngine() {
3477                 return 'SearchEngineDummy';
3478         }
3479
3480         /**
3481          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3482          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3483          * because "i" sorts after all numbers.
3484          *
3485          * @return String
3486          */
3487         public function getInfinity() {
3488                 return 'infinity';
3489         }
3490
3491         /**
3492          * Encode an expiry time into the DBMS dependent format
3493          *
3494          * @param $expiry String: timestamp for expiry, or the 'infinity' string
3495          * @return String
3496          */
3497         public function encodeExpiry( $expiry ) {
3498                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3499                         ? $this->getInfinity()
3500                         : $this->timestamp( $expiry );
3501         }
3502
3503         /**
3504          * Decode an expiry time into a DBMS independent format
3505          *
3506          * @param $expiry String: DB timestamp field value for expiry
3507          * @param $format integer: TS_* constant, defaults to TS_MW
3508          * @return String
3509          */
3510         public function decodeExpiry( $expiry, $format = TS_MW ) {
3511                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3512                         ? 'infinity'
3513                         : wfTimestamp( $format, $expiry );
3514         }
3515
3516         /**
3517          * Allow or deny "big selects" for this session only. This is done by setting
3518          * the sql_big_selects session variable.
3519          *
3520          * This is a MySQL-specific feature.
3521          *
3522          * @param $value Mixed: true for allow, false for deny, or "default" to
3523          *   restore the initial value
3524          */
3525         public function setBigSelects( $value = true ) {
3526                 // no-op
3527         }
3528
3529         /**
3530          * @since 1.19
3531          */
3532         public function __toString() {
3533                 return (string)$this->mConn;
3534         }
3535 }