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         protected $mConn = null;
 229         protected $mOpened = false;
 230
 231         /**
 232          * @since 1.20
 233          * @var array of Closure
 234          */
 235         protected $mTrxIdleCallbacks = array();
 236
 237         protected $mTablePrefix;
 238         protected $mFlags;
 239         protected $mTrxLevel = 0;
 240         protected $mErrorCount = 0;
 241         protected $mLBInfo = array();
 242         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 243         protected $mDefaultBigSelects = null;
 244         protected $mSchemaVars = false;
 245
 246         protected $preparedArgs;
 247
 248         protected $htmlErrors;
 249
 250         protected $delimiter = ';';
 251
 252         /**
 253          * Remembers the function name given for starting the most recent transaction via begin().
 254          * Used to provide additional context for error reporting.
 255          *
 256          * @var String
 257          * @see DatabaseBase::mTrxLevel
 258          */
 259         private $mTrxFname = null;
 260
 261         /**
 262          * Record if possible write queries were done in the last transaction started
 263          *
 264          * @var Bool
 265          * @see DatabaseBase::mTrxLevel
 266          */
 267         private $mTrxDoneWrites = false;
 268
 269         /**
 270          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 271          *
 272          * @var Bool
 273          * @see DatabaseBase::mTrxLevel
 274          */
 275         private $mTrxAutomatic = false;
 276
 277 # ------------------------------------------------------------------------------
 278 # Accessors
 279 # ------------------------------------------------------------------------------
 280         # These optionally set a variable and return the previous state
 281
 282         /**
 283          * A string describing the current software version, and possibly
 284          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 285          * Use getServerVersion() to get machine-friendly information.
 286          *
 287          * @return string: Version information from the database server
 288          */
 289         public function getServerInfo() {
 290                 return $this->getServerVersion();
 291         }
 292
 293         /**
 294          * @return string: command delimiter used by this database engine
 295          */
 296         public function getDelimiter() {
 297                 return $this->delimiter;
 298         }
 299
 300         /**
 301          * Boolean, controls output of large amounts of debug information.
 302          * @param $debug bool|null
 303          *   - true to enable debugging
 304          *   - false to disable debugging
 305          *   - omitted or null to do nothing
 306          *
 307          * @return bool|null previous value of the flag
 308          */
 309         public function debug( $debug = null ) {
 310                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 311         }
 312
 313         /**
 314          * Turns buffering of SQL result sets on (true) or off (false). Default is
 315          * "on".
 316          *
 317          * Unbuffered queries are very troublesome in MySQL:
 318          *
 319          *   - If another query is executed while the first query is being read
 320          *     out, the first query is killed. This means you can't call normal
 321          *     MediaWiki functions while you are reading an unbuffered query result
 322          *     from a normal wfGetDB() connection.
 323          *
 324          *   - Unbuffered queries cause the MySQL server to use large amounts of
 325          *     memory and to hold broad locks which block other queries.
 326          *
 327          * If you want to limit client-side memory, it's almost always better to
 328          * split up queries into batches using a LIMIT clause than to switch off
 329          * buffering.
 330          *
 331          * @param $buffer null|bool
 332          *
 333          * @return null|bool The previous value of the flag
 334          */
 335         public function bufferResults( $buffer = null ) {
 336                 if ( is_null( $buffer ) ) {
 337                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 338                 } else {
 339                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 340                 }
 341         }
 342
 343         /**
 344          * Turns on (false) or off (true) the automatic generation and sending
 345          * of a "we're sorry, but there has been a database error" page on
 346          * database errors. Default is on (false). When turned off, the
 347          * code should use lastErrno() and lastError() to handle the
 348          * situation as appropriate.
 349          *
 350          * @param $ignoreErrors bool|null
 351          *
 352          * @return bool The previous value of the flag.
 353          */
 354         public function ignoreErrors( $ignoreErrors = null ) {
 355                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 356         }
 357
 358         /**
 359          * Gets or sets the current transaction level.
 360          *
 361          * Historically, transactions were allowed to be "nested". This is no
 362          * longer supported, so this function really only returns a boolean.
 363          *
 364          * @param $level int An integer (0 or 1), or omitted to leave it unchanged.
 365          * @return int The previous value
 366          */
 367         public function trxLevel( $level = null ) {
 368                 return wfSetVar( $this->mTrxLevel, $level );
 369         }
 370
 371         /**
 372          * Get/set the number of errors logged. Only useful when errors are ignored
 373          * @param $count int The count to set, or omitted to leave it unchanged.
 374          * @return int The error count
 375          */
 376         public function errorCount( $count = null ) {
 377                 return wfSetVar( $this->mErrorCount, $count );
 378         }
 379
 380         /**
 381          * Get/set the table prefix.
 382          * @param $prefix string The table prefix to set, or omitted to leave it unchanged.
 383          * @return string The previous table prefix.
 384          */
 385         public function tablePrefix( $prefix = null ) {
 386                 return wfSetVar( $this->mTablePrefix, $prefix );
 387         }
 388
 389         /**
 390          * Get properties passed down from the server info array of the load
 391          * balancer.
 392          *
 393          * @param $name string The entry of the info array to get, or null to get the
 394          *   whole array
 395          *
 396          * @return LoadBalancer|null
 397          */
 398         public function getLBInfo( $name = null ) {
 399                 if ( is_null( $name ) ) {
 400                         return $this->mLBInfo;
 401                 } else {
 402                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 403                                 return $this->mLBInfo[$name];
 404                         } else {
 405                                 return null;
 406                         }
 407                 }
 408         }
 409
 410         /**
 411          * Set the LB info array, or a member of it. If called with one parameter,
 412          * the LB info array is set to that parameter. If it is called with two
 413          * parameters, the member with the given name is set to the given value.
 414          *
 415          * @param $name
 416          * @param $value
 417          */
 418         public function setLBInfo( $name, $value = null ) {
 419                 if ( is_null( $value ) ) {
 420                         $this->mLBInfo = $name;
 421                 } else {
 422                         $this->mLBInfo[$name] = $value;
 423                 }
 424         }
 425
 426         /**
 427          * Set lag time in seconds for a fake slave
 428          *
 429          * @param $lag int
 430          */
 431         public function setFakeSlaveLag( $lag ) {
 432                 $this->mFakeSlaveLag = $lag;
 433         }
 434
 435         /**
 436          * Make this connection a fake master
 437          *
 438          * @param $enabled bool
 439          */
 440         public function setFakeMaster( $enabled = true ) {
 441                 $this->mFakeMaster = $enabled;
 442         }
 443
 444         /**
 445          * Returns true if this database supports (and uses) cascading deletes
 446          *
 447          * @return bool
 448          */
 449         public function cascadingDeletes() {
 450                 return false;
 451         }
 452
 453         /**
 454          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 455          *
 456          * @return bool
 457          */
 458         public function cleanupTriggers() {
 459                 return false;
 460         }
 461
 462         /**
 463          * Returns true if this database is strict about what can be put into an IP field.
 464          * Specifically, it uses a NULL value instead of an empty string.
 465          *
 466          * @return bool
 467          */
 468         public function strictIPs() {
 469                 return false;
 470         }
 471
 472         /**
 473          * Returns true if this database uses timestamps rather than integers
 474          *
 475          * @return bool
 476         */
 477         public function realTimestamps() {
 478                 return false;
 479         }
 480
 481         /**
 482          * Returns true if this database does an implicit sort when doing GROUP BY
 483          *
 484          * @return bool
 485          */
 486         public function implicitGroupby() {
 487                 return true;
 488         }
 489
 490         /**
 491          * Returns true if this database does an implicit order by when the column has an index
 492          * For example: SELECT page_title FROM page LIMIT 1
 493          *
 494          * @return bool
 495          */
 496         public function implicitOrderby() {
 497                 return true;
 498         }
 499
 500         /**
 501          * Returns true if this database can do a native search on IP columns
 502          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 503          *
 504          * @return bool
 505          */
 506         public function searchableIPs() {
 507                 return false;
 508         }
 509
 510         /**
 511          * Returns true if this database can use functional indexes
 512          *
 513          * @return bool
 514          */
 515         public function functionalIndexes() {
 516                 return false;
 517         }
 518
 519         /**
 520          * Return the last query that went through DatabaseBase::query()
 521          * @return String
 522          */
 523         public function lastQuery() {
 524                 return $this->mLastQuery;
 525         }
 526
 527         /**
 528          * Returns true if the connection may have been used for write queries.
 529          * Should return true if unsure.
 530          *
 531          * @return bool
 532          */
 533         public function doneWrites() {
 534                 return $this->mDoneWrites;
 535         }
 536
 537         /**
 538          * Returns true if there is a transaction open with possible write
 539          * queries or transaction idle callbacks waiting on it to finish.
 540          *
 541          * @return bool
 542          */
 543         public function writesOrCallbacksPending() {
 544                 return $this->mTrxLevel && ( $this->mTrxDoneWrites || $this->mTrxIdleCallbacks );
 545         }
 546
 547         /**
 548          * Is a connection to the database open?
 549          * @return Boolean
 550          */
 551         public function isOpen() {
 552                 return $this->mOpened;
 553         }
 554
 555         /**
 556          * Set a flag for this connection
 557          *
 558          * @param $flag Integer: DBO_* constants from Defines.php:
 559          *   - DBO_DEBUG: output some debug info (same as debug())
 560          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 561          *   - DBO_IGNORE: ignore errors (same as ignoreErrors())
 562          *   - DBO_TRX: automatically start transactions
 563          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 564          *       and removes it in command line mode
 565          *   - DBO_PERSISTENT: use persistant database connection
 566          */
 567         public function setFlag( $flag ) {
 568                 global $wgDebugDBTransactions;
 569                 $this->mFlags |= $flag;
 570                 if ( ( $flag & DBO_TRX) & $wgDebugDBTransactions ) {
 571                         wfDebug("Implicit transactions are now  disabled.\n");
 572                 }
 573         }
 574
 575         /**
 576          * Clear a flag for this connection
 577          *
 578          * @param $flag: same as setFlag()'s $flag param
 579          */
 580         public function clearFlag( $flag ) {
 581                 global $wgDebugDBTransactions;
 582                 $this->mFlags &= ~$flag;
 583                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 584                         wfDebug("Implicit transactions are now disabled.\n");
 585                 }
 586         }
 587
 588         /**
 589          * Returns a boolean whether the flag $flag is set for this connection
 590          *
 591          * @param $flag: same as setFlag()'s $flag param
 592          * @return Boolean
 593          */
 594         public function getFlag( $flag ) {
 595                 return !!( $this->mFlags & $flag );
 596         }
 597
 598         /**
 599          * General read-only accessor
 600          *
 601          * @param $name string
 602          *
 603          * @return string
 604          */
 605         public function getProperty( $name ) {
 606                 return $this->$name;
 607         }
 608
 609         /**
 610          * @return string
 611          */
 612         public function getWikiID() {
 613                 if ( $this->mTablePrefix ) {
 614                         return "{$this->mDBname}-{$this->mTablePrefix}";
 615                 } else {
 616                         return $this->mDBname;
 617                 }
 618         }
 619
 620         /**
 621          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 622          *
 623          * @return string
 624          */
 625         public function getSchemaPath() {
 626                 global $IP;
 627                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 628                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 629                 } else {
 630                         return "$IP/maintenance/tables.sql";
 631                 }
 632         }
 633
 634 # ------------------------------------------------------------------------------
 635 # Other functions
 636 # ------------------------------------------------------------------------------
 637
 638         /**
 639          * Constructor.
 640          * @param $server String: database server host
 641          * @param $user String: database user name
 642          * @param $password String: database user password
 643          * @param $dbName String: database name
 644          * @param $flags
 645          * @param $tablePrefix String: database table prefixes. By default use the prefix gave in LocalSettings.php
 646          */
 647         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 648                 $flags = 0, $tablePrefix = 'get from global'
 649         ) {
 650                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 651
 652                 $this->mFlags = $flags;
 653
 654                 if ( $this->mFlags & DBO_DEFAULT ) {
 655                         if ( $wgCommandLineMode ) {
 656                                 $this->mFlags &= ~DBO_TRX;
 657                                 if ( $wgDebugDBTransactions ) {
 658                                         wfDebug("Implicit transaction open disabled.\n");
 659                                 }
 660                         } else {
 661                                 $this->mFlags |= DBO_TRX;
 662                                 if ( $wgDebugDBTransactions ) {
 663                                         wfDebug("Implicit transaction open enabled.\n");
 664                                 }
 665                         }
 666                 }
 667
 668                 /** Get the default table prefix*/
 669                 if ( $tablePrefix == 'get from global' ) {
 670                         $this->mTablePrefix = $wgDBprefix;
 671                 } else {
 672                         $this->mTablePrefix = $tablePrefix;
 673                 }
 674
 675                 if ( $user ) {
 676                         $this->open( $server, $user, $password, $dbName );
 677                 }
 678         }
 679
 680         /**
 681          * Called by serialize. Throw an exception when DB connection is serialized.
 682          * This causes problems on some database engines because the connection is
 683          * not restored on unserialize.
 684          */
 685         public function __sleep() {
 686                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 687         }
 688
 689         /**
 690          * Given a DB type, construct the name of the appropriate child class of
 691          * DatabaseBase. This is designed to replace all of the manual stuff like:
 692          *      $class = 'Database' . ucfirst( strtolower( $type ) );
 693          * as well as validate against the canonical list of DB types we have
 694          *
 695          * This factory function is mostly useful for when you need to connect to a
 696          * database other than the MediaWiki default (such as for external auth,
 697          * an extension, et cetera). Do not use this to connect to the MediaWiki
 698          * database. Example uses in core:
 699          * @see LoadBalancer::reallyOpenConnection()
 700          * @see ExternalUser_MediaWiki::initFromCond()
 701          * @see ForeignDBRepo::getMasterDB()
 702          * @see WebInstaller_DBConnect::execute()
 703          *
 704          * @since 1.18
 705          *
 706          * @param $dbType String A possible DB type
 707          * @param $p Array An array of options to pass to the constructor.
 708          *    Valid options are: host, user, password, dbname, flags, tablePrefix
 709          * @return DatabaseBase subclass or null
 710          */
 711         public final static function factory( $dbType, $p = array() ) {
 712                 $canonicalDBTypes = array(
 713                         'mysql', 'postgres', 'sqlite', 'oracle', 'mssql', 'ibm_db2'
 714                 );
 715                 $dbType = strtolower( $dbType );
 716                 $class = 'Database' . ucfirst( $dbType );
 717
 718                 if( in_array( $dbType, $canonicalDBTypes ) || ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) ) {
 719                         return new $class(
 720                                 isset( $p['host'] ) ? $p['host'] : false,
 721                                 isset( $p['user'] ) ? $p['user'] : false,
 722                                 isset( $p['password'] ) ? $p['password'] : false,
 723                                 isset( $p['dbname'] ) ? $p['dbname'] : false,
 724                                 isset( $p['flags'] ) ? $p['flags'] : 0,
 725                                 isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global'
 726                         );
 727                 } else {
 728                         return null;
 729                 }
 730         }
 731
 732         protected function installErrorHandler() {
 733                 $this->mPHPError = false;
 734                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 735                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 736         }
 737
 738         /**
 739          * @return bool|string
 740          */
 741         protected function restoreErrorHandler() {
 742                 restore_error_handler();
 743                 if ( $this->htmlErrors !== false ) {
 744                         ini_set( 'html_errors', $this->htmlErrors );
 745                 }
 746                 if ( $this->mPHPError ) {
 747                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 748                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 749                         return $error;
 750                 } else {
 751                         return false;
 752                 }
 753         }
 754
 755         /**
 756          * @param $errno
 757          * @param $errstr
 758          */
 759         protected function connectionErrorHandler( $errno,  $errstr ) {
 760                 $this->mPHPError = $errstr;
 761         }
 762
 763         /**
 764          * Closes a database connection.
 765          * if it is open : commits any open transactions
 766          *
 767          * @return Bool operation success. true if already closed.
 768          */
 769         public function close() {
 770                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 771                         throw new MWException( "Transaction idle callbacks still pending." );
 772                 }
 773                 $this->mOpened = false;
 774                 if ( $this->mConn ) {
 775                         if ( $this->trxLevel() ) {
 776                                 if ( !$this->mTrxAutomatic ) {
 777                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 778                                                 " performing implicit commit before closing connection!" );
 779                                 }
 780
 781                                 $this->commit( __METHOD__, 'flush' );
 782                         }
 783
 784                         $ret = $this->closeConnection();
 785                         $this->mConn = false;
 786                         return $ret;
 787                 } else {
 788                         return true;
 789                 }
 790         }
 791
 792         /**
 793          * Closes underlying database connection
 794          * @since 1.20
 795          * @return bool: Whether connection was closed successfully
 796          */
 797         protected abstract function closeConnection();
 798
 799         /**
 800          * @param $error String: fallback error message, used if none is given by DB
 801          * @throws DBConnectionError
 802          */
 803         function reportConnectionError( $error = 'Unknown error' ) {
 804                 $myError = $this->lastError();
 805                 if ( $myError ) {
 806                         $error = $myError;
 807                 }
 808
 809                 # New method
 810                 throw new DBConnectionError( $this, $error );
 811         }
 812
 813         /**
 814          * The DBMS-dependent part of query()
 815          *
 816          * @param  $sql String: SQL query.
 817          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 818          */
 819         protected abstract function doQuery( $sql );
 820
 821         /**
 822          * Determine whether a query writes to the DB.
 823          * Should return true if unsure.
 824          *
 825          * @param $sql string
 826          *
 827          * @return bool
 828          */
 829         public function isWriteQuery( $sql ) {
 830                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 831         }
 832
 833         /**
 834          * Run an SQL query and return the result. Normally throws a DBQueryError
 835          * on failure. If errors are ignored, returns false instead.
 836          *
 837          * In new code, the query wrappers select(), insert(), update(), delete(),
 838          * etc. should be used where possible, since they give much better DBMS
 839          * independence and automatically quote or validate user input in a variety
 840          * of contexts. This function is generally only useful for queries which are
 841          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 842          * as CREATE TABLE.
 843          *
 844          * However, the query wrappers themselves should call this function.
 845          *
 846          * @param  $sql        String: SQL query
 847          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 848          *     comment (you can use __METHOD__ or add some extra info)
 849          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 850          *     maybe best to catch the exception instead?
 851          * @throws MWException
 852          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 853          *     for a successful read query, or false on failure if $tempIgnore set
 854          */
 855         public function query( $sql, $fname = '', $tempIgnore = false ) {
 856                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 857                 if ( !Profiler::instance()->isStub() ) {
 858                         # generalizeSQL will probably cut down the query to reasonable
 859                         # logging size most of the time. The substr is really just a sanity check.
 860
 861                         if ( $isMaster ) {
 862                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 863                                 $totalProf = 'DatabaseBase::query-master';
 864                         } else {
 865                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 866                                 $totalProf = 'DatabaseBase::query';
 867                         }
 868
 869                         wfProfileIn( $totalProf );
 870                         wfProfileIn( $queryProf );
 871                 }
 872
 873                 $this->mLastQuery = $sql;
 874                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 875                         # Set a flag indicating that writes have been done
 876                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 877                         $this->mDoneWrites = true;
 878                 }
 879
 880                 # Add a comment for easy SHOW PROCESSLIST interpretation
 881                 global $wgUser;
 882                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 883                         $userName = $wgUser->getName();
 884                         if ( mb_strlen( $userName ) > 15 ) {
 885                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 886                         }
 887                         $userName = str_replace( '/', '', $userName );
 888                 } else {
 889                         $userName = '';
 890                 }
 891                 $commentedSql = preg_replace( '/\s/', " /* $fname $userName */ ", $sql, 1 );
 892
 893                 # If DBO_TRX is set, start a transaction
 894                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 895                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' )
 896                 {
 897                         # Avoid establishing transactions for SHOW and SET statements too -
 898                         # that would delay transaction initializations to once connection
 899                         # is really used by application
 900                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 901                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 902                                 global $wgDebugDBTransactions;
 903                                 if ( $wgDebugDBTransactions ) {
 904                                         wfDebug("Implicit transaction start.\n");
 905                                 }
 906                                 $this->begin( __METHOD__ . " ($fname)" );
 907                                 $this->mTrxAutomatic = true;
 908                         }
 909                 }
 910
 911                 # Keep track of whether the transaction has write queries pending
 912                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
 913                         $this->mTrxDoneWrites = true;
 914                 }
 915
 916                 if ( $this->debug() ) {
 917                         static $cnt = 0;
 918
 919                         $cnt++;
 920                         $sqlx = substr( $commentedSql, 0, 500 );
 921                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 922
 923                         $master = $isMaster ? 'master' : 'slave';
 924                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 925                 }
 926
 927                 if ( istainted( $sql ) & TC_MYSQL ) {
 928                         throw new MWException( 'Tainted query found' );
 929                 }
 930
 931                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 932
 933                 # Do the query and handle errors
 934                 $ret = $this->doQuery( $commentedSql );
 935
 936                 MWDebug::queryTime( $queryId );
 937
 938                 # Try reconnecting if the connection was lost
 939                 if ( false === $ret && $this->wasErrorReissuable() ) {
 940                         # Transaction is gone, like it or not
 941                         $this->mTrxLevel = 0;
 942                         $this->mTrxIdleCallbacks = array(); // cancel
 943                         wfDebug( "Connection lost, reconnecting...\n" );
 944
 945                         if ( $this->ping() ) {
 946                                 wfDebug( "Reconnected\n" );
 947                                 $sqlx = substr( $commentedSql, 0, 500 );
 948                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
 949                                 global $wgRequestTime;
 950                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
 951                                 if ( $elapsed < 300 ) {
 952                                         # Not a database error to lose a transaction after a minute or two
 953                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
 954                                 }
 955                                 $ret = $this->doQuery( $commentedSql );
 956                         } else {
 957                                 wfDebug( "Failed\n" );
 958                         }
 959                 }
 960
 961                 if ( false === $ret ) {
 962                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 963                 }
 964
 965                 if ( !Profiler::instance()->isStub() ) {
 966                         wfProfileOut( $queryProf );
 967                         wfProfileOut( $totalProf );
 968                 }
 969
 970                 return $this->resultObject( $ret );
 971         }
 972
 973         /**
 974          * Report a query error. Log the error, and if neither the object ignore
 975          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
 976          *
 977          * @param $error String
 978          * @param $errno Integer
 979          * @param $sql String
 980          * @param $fname String
 981          * @param $tempIgnore Boolean
 982          * @throws DBQueryError
 983          */
 984         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
 985                 # Ignore errors during error handling to avoid infinite recursion
 986                 $ignore = $this->ignoreErrors( true );
 987                 ++$this->mErrorCount;
 988
 989                 if ( $ignore || $tempIgnore ) {
 990                         wfDebug( "SQL ERROR (ignored): $error\n" );
 991                         $this->ignoreErrors( $ignore );
 992                 } else {
 993                         $sql1line = str_replace( "\n", "\\n", $sql );
 994                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
 995                         wfDebug( "SQL ERROR: " . $error . "\n" );
 996                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
 997                 }
 998         }
 999
1000         /**
1001          * Intended to be compatible with the PEAR::DB wrapper functions.
1002          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1003          *
1004          * ? = scalar value, quoted as necessary
1005          * ! = raw SQL bit (a function for instance)
1006          * & = filename; reads the file and inserts as a blob
1007          *     (we don't use this though...)
1008          *
1009          * @param $sql string
1010          * @param $func string
1011          *
1012          * @return array
1013          */
1014         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1015                 /* MySQL doesn't support prepared statements (yet), so just
1016                    pack up the query for reference. We'll manually replace
1017                    the bits later. */
1018                 return array( 'query' => $sql, 'func' => $func );
1019         }
1020
1021         /**
1022          * Free a prepared query, generated by prepare().
1023          * @param $prepared
1024          */
1025         protected function freePrepared( $prepared ) {
1026                 /* No-op by default */
1027         }
1028
1029         /**
1030          * Execute a prepared query with the various arguments
1031          * @param $prepared String: the prepared sql
1032          * @param $args Mixed: Either an array here, or put scalars as varargs
1033          *
1034          * @return ResultWrapper
1035          */
1036         public function execute( $prepared, $args = null ) {
1037                 if ( !is_array( $args ) ) {
1038                         # Pull the var args
1039                         $args = func_get_args();
1040                         array_shift( $args );
1041                 }
1042
1043                 $sql = $this->fillPrepared( $prepared['query'], $args );
1044
1045                 return $this->query( $sql, $prepared['func'] );
1046         }
1047
1048         /**
1049          * For faking prepared SQL statements on DBs that don't support it directly.
1050          *
1051          * @param $preparedQuery String: a 'preparable' SQL statement
1052          * @param $args Array of arguments to fill it with
1053          * @return string executable SQL
1054          */
1055         public function fillPrepared( $preparedQuery, $args ) {
1056                 reset( $args );
1057                 $this->preparedArgs =& $args;
1058
1059                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1060                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1061         }
1062
1063         /**
1064          * preg_callback func for fillPrepared()
1065          * The arguments should be in $this->preparedArgs and must not be touched
1066          * while we're doing this.
1067          *
1068          * @param $matches Array
1069          * @throws DBUnexpectedError
1070          * @return String
1071          */
1072         protected function fillPreparedArg( $matches ) {
1073                 switch( $matches[1] ) {
1074                         case '\\?': return '?';
1075                         case '\\!': return '!';
1076                         case '\\&': return '&';
1077                 }
1078
1079                 list( /* $n */ , $arg ) = each( $this->preparedArgs );
1080
1081                 switch( $matches[1] ) {
1082                         case '?': return $this->addQuotes( $arg );
1083                         case '!': return $arg;
1084                         case '&':
1085                                 # return $this->addQuotes( file_get_contents( $arg ) );
1086                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1087                         default:
1088                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1089                 }
1090         }
1091
1092         /**
1093          * Free a result object returned by query() or select(). It's usually not
1094          * necessary to call this, just use unset() or let the variable holding
1095          * the result object go out of scope.
1096          *
1097          * @param $res Mixed: A SQL result
1098          */
1099         public function freeResult( $res ) {}
1100
1101         /**
1102          * A SELECT wrapper which returns a single field from a single result row.
1103          *
1104          * Usually throws a DBQueryError on failure. If errors are explicitly
1105          * ignored, returns false on failure.
1106          *
1107          * If no result rows are returned from the query, false is returned.
1108          *
1109          * @param $table string|array Table name. See DatabaseBase::select() for details.
1110          * @param $var string The field name to select. This must be a valid SQL
1111          *   fragment: do not use unvalidated user input.
1112          * @param $cond string|array The condition array. See DatabaseBase::select() for details.
1113          * @param $fname string The function name of the caller.
1114          * @param $options string|array The query options. See DatabaseBase::select() for details.
1115          *
1116          * @return bool|mixed The value from the field, or false on failure.
1117          */
1118         public function selectField( $table, $var, $cond = '', $fname = 'DatabaseBase::selectField',
1119                 $options = array() )
1120         {
1121                 if ( !is_array( $options ) ) {
1122                         $options = array( $options );
1123                 }
1124
1125                 $options['LIMIT'] = 1;
1126
1127                 $res = $this->select( $table, $var, $cond, $fname, $options );
1128
1129                 if ( $res === false || !$this->numRows( $res ) ) {
1130                         return false;
1131                 }
1132
1133                 $row = $this->fetchRow( $res );
1134
1135                 if ( $row !== false ) {
1136                         return reset( $row );
1137                 } else {
1138                         return false;
1139                 }
1140         }
1141
1142         /**
1143          * Returns an optional USE INDEX clause to go after the table, and a
1144          * string to go at the end of the query.
1145          *
1146          * @param $options Array: associative array of options to be turned into
1147          *              an SQL query, valid keys are listed in the function.
1148          * @return Array
1149          * @see DatabaseBase::select()
1150          */
1151         public function makeSelectOptions( $options ) {
1152                 $preLimitTail = $postLimitTail = '';
1153                 $startOpts = '';
1154
1155                 $noKeyOptions = array();
1156
1157                 foreach ( $options as $key => $option ) {
1158                         if ( is_numeric( $key ) ) {
1159                                 $noKeyOptions[$option] = true;
1160                         }
1161                 }
1162
1163                 if ( isset( $options['GROUP BY'] ) ) {
1164                         $gb = is_array( $options['GROUP BY'] )
1165                                 ? implode( ',', $options['GROUP BY'] )
1166                                 : $options['GROUP BY'];
1167                         $preLimitTail .= " GROUP BY {$gb}";
1168                 }
1169
1170                 if ( isset( $options['HAVING'] ) ) {
1171                         $having = is_array( $options['HAVING'] )
1172                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1173                                 : $options['HAVING'];
1174                         $preLimitTail .= " HAVING {$having}";
1175                 }
1176
1177                 if ( isset( $options['ORDER BY'] ) ) {
1178                         $ob = is_array( $options['ORDER BY'] )
1179                                 ? implode( ',', $options['ORDER BY'] )
1180                                 : $options['ORDER BY'];
1181                         $preLimitTail .= " ORDER BY {$ob}";
1182                 }
1183
1184                 // if (isset($options['LIMIT'])) {
1185                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1186                 //              isset($options['OFFSET']) ? $options['OFFSET']
1187                 //              : false);
1188                 // }
1189
1190                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1191                         $postLimitTail .= ' FOR UPDATE';
1192                 }
1193
1194                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1195                         $postLimitTail .= ' LOCK IN SHARE MODE';
1196                 }
1197
1198                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1199                         $startOpts .= 'DISTINCT';
1200                 }
1201
1202                 # Various MySQL extensions
1203                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1204                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1205                 }
1206
1207                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1208                         $startOpts .= ' HIGH_PRIORITY';
1209                 }
1210
1211                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1212                         $startOpts .= ' SQL_BIG_RESULT';
1213                 }
1214
1215                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1216                         $startOpts .= ' SQL_BUFFER_RESULT';
1217                 }
1218
1219                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1220                         $startOpts .= ' SQL_SMALL_RESULT';
1221                 }
1222
1223                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1224                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1225                 }
1226
1227                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1228                         $startOpts .= ' SQL_CACHE';
1229                 }
1230
1231                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1232                         $startOpts .= ' SQL_NO_CACHE';
1233                 }
1234
1235                 if ( isset( $options['USE INDEX'] ) && ! is_array( $options['USE INDEX'] ) ) {
1236                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1237                 } else {
1238                         $useIndex = '';
1239                 }
1240
1241                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1242         }
1243
1244         /**
1245          * Execute a SELECT query constructed using the various parameters provided.
1246          * See below for full details of the parameters.
1247          *
1248          * @param $table String|Array Table name
1249          * @param $vars String|Array Field names
1250          * @param $conds String|Array Conditions
1251          * @param $fname String Caller function name
1252          * @param $options Array Query options
1253          * @param $join_conds Array Join conditions
1254          *
1255          * @param $table string|array
1256          *
1257          * May be either an array of table names, or a single string holding a table
1258          * name. If an array is given, table aliases can be specified, for example:
1259          *
1260          *    array( 'a' => 'user' )
1261          *
1262          * This includes the user table in the query, with the alias "a" available
1263          * for use in field names (e.g. a.user_name).
1264          *
1265          * All of the table names given here are automatically run through
1266          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1267          * added, and various other table name mappings to be performed.
1268          *
1269          *
1270          * @param $vars string|array
1271          *
1272          * May be either a field name or an array of field names. The field names
1273          * can be complete fragments of SQL, for direct inclusion into the SELECT
1274          * query. If an array is given, field aliases can be specified, for example:
1275          *
1276          *   array( 'maxrev' => 'MAX(rev_id)' )
1277          *
1278          * This includes an expression with the alias "maxrev" in the query.
1279          *
1280          * If an expression is given, care must be taken to ensure that it is
1281          * DBMS-independent.
1282          *
1283          *
1284          * @param $conds string|array
1285          *
1286          * May be either a string containing a single condition, or an array of
1287          * conditions. If an array is given, the conditions constructed from each
1288          * element are combined with AND.
1289          *
1290          * Array elements may take one of two forms:
1291          *
1292          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1293          *   - Elements with a string key are interpreted as equality conditions,
1294          *     where the key is the field name.
1295          *     - If the value of such an array element is a scalar (such as a
1296          *       string), it will be treated as data and thus quoted appropriately.
1297          *       If it is null, an IS NULL clause will be added.
1298          *     - If the value is an array, an IN(...) clause will be constructed,
1299          *       such that the field name may match any of the elements in the
1300          *       array. The elements of the array will be quoted.
1301          *
1302          * Note that expressions are often DBMS-dependent in their syntax.
1303          * DBMS-independent wrappers are provided for constructing several types of
1304          * expression commonly used in condition queries. See:
1305          *    - DatabaseBase::buildLike()
1306          *    - DatabaseBase::conditional()
1307          *
1308          *
1309          * @param $options string|array
1310          *
1311          * Optional: Array of query options. Boolean options are specified by
1312          * including them in the array as a string value with a numeric key, for
1313          * example:
1314          *
1315          *    array( 'FOR UPDATE' )
1316          *
1317          * The supported options are:
1318          *
1319          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1320          *     with LIMIT can theoretically be used for paging through a result set,
1321          *     but this is discouraged in MediaWiki for performance reasons.
1322          *
1323          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1324          *     and then the first rows are taken until the limit is reached. LIMIT
1325          *     is applied to a result set after OFFSET.
1326          *
1327          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1328          *     changed until the next COMMIT.
1329          *
1330          *   - DISTINCT: Boolean: return only unique result rows.
1331          *
1332          *   - GROUP BY: May be either an SQL fragment string naming a field or
1333          *     expression to group by, or an array of such SQL fragments.
1334          *
1335          *   - HAVING: May be either an string containing a HAVING clause or an array of
1336          *     conditions building the HAVING clause. If an array is given, the conditions
1337          *     constructed from each element are combined with AND.
1338          *
1339          *   - ORDER BY: May be either an SQL fragment giving a field name or
1340          *     expression to order by, or an array of such SQL fragments.
1341          *
1342          *   - USE INDEX: This may be either a string giving the index name to use
1343          *     for the query, or an array. If it is an associative array, each key
1344          *     gives the table name (or alias), each value gives the index name to
1345          *     use for that table. All strings are SQL fragments and so should be
1346          *     validated by the caller.
1347          *
1348          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1349          *     instead of SELECT.
1350          *
1351          * And also the following boolean MySQL extensions, see the MySQL manual
1352          * for documentation:
1353          *
1354          *    - LOCK IN SHARE MODE
1355          *    - STRAIGHT_JOIN
1356          *    - HIGH_PRIORITY
1357          *    - SQL_BIG_RESULT
1358          *    - SQL_BUFFER_RESULT
1359          *    - SQL_SMALL_RESULT
1360          *    - SQL_CALC_FOUND_ROWS
1361          *    - SQL_CACHE
1362          *    - SQL_NO_CACHE
1363          *
1364          *
1365          * @param $join_conds string|array
1366          *
1367          * Optional associative array of table-specific join conditions. In the
1368          * most common case, this is unnecessary, since the join condition can be
1369          * in $conds. However, it is useful for doing a LEFT JOIN.
1370          *
1371          * The key of the array contains the table name or alias. The value is an
1372          * array with two elements, numbered 0 and 1. The first gives the type of
1373          * join, the second is an SQL fragment giving the join condition for that
1374          * table. For example:
1375          *
1376          *    array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
1377          *
1378          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1379          *   with no rows in it will be returned. If there was a query error, a
1380          *   DBQueryError exception will be thrown, except if the "ignore errors"
1381          *   option was set, in which case false will be returned.
1382          */
1383         public function select( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1384                 $options = array(), $join_conds = array() ) {
1385                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1386
1387                 return $this->query( $sql, $fname );
1388         }
1389
1390         /**
1391          * The equivalent of DatabaseBase::select() except that the constructed SQL
1392          * is returned, instead of being immediately executed. This can be useful for
1393          * doing UNION queries, where the SQL text of each query is needed. In general,
1394          * however, callers outside of Database classes should just use select().
1395          *
1396          * @param $table string|array Table name
1397          * @param $vars string|array Field names
1398          * @param $conds string|array Conditions
1399          * @param $fname string Caller function name
1400          * @param $options string|array Query options
1401          * @param $join_conds string|array Join conditions
1402          *
1403          * @return string SQL query string.
1404          * @see DatabaseBase::select()
1405          */
1406         public function selectSQLText( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1407                 $options = array(), $join_conds = array() )
1408         {
1409                 if ( is_array( $vars ) ) {
1410                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1411                 }
1412
1413                 $options = (array)$options;
1414
1415                 if ( is_array( $table ) ) {
1416                         $useIndex = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1417                                 ? $options['USE INDEX']
1418                                 : array();
1419                         if ( count( $join_conds ) || count( $useIndex ) ) {
1420                                 $from = ' FROM ' .
1421                                         $this->tableNamesWithUseIndexOrJOIN( $table, $useIndex, $join_conds );
1422                         } else {
1423                                 $from = ' FROM ' . implode( ',', $this->tableNamesWithAlias( $table ) );
1424                         }
1425                 } elseif ( $table != '' ) {
1426                         if ( $table[0] == ' ' ) {
1427                                 $from = ' FROM ' . $table;
1428                         } else {
1429                                 $from = ' FROM ' . $this->tableName( $table );
1430                         }
1431                 } else {
1432                         $from = '';
1433                 }
1434
1435                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) = $this->makeSelectOptions( $options );
1436
1437                 if ( !empty( $conds ) ) {
1438                         if ( is_array( $conds ) ) {
1439                                 $conds = $this->makeList( $conds, LIST_AND );
1440                         }
1441                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1442                 } else {
1443                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1444                 }
1445
1446                 if ( isset( $options['LIMIT'] ) ) {
1447                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1448                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1449                 }
1450                 $sql = "$sql $postLimitTail";
1451
1452                 if ( isset( $options['EXPLAIN'] ) ) {
1453                         $sql = 'EXPLAIN ' . $sql;
1454                 }
1455
1456                 return $sql;
1457         }
1458
1459         /**
1460          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1461          * that a single row object is returned. If the query returns no rows,
1462          * false is returned.
1463          *
1464          * @param $table string|array Table name
1465          * @param $vars string|array Field names
1466          * @param $conds array Conditions
1467          * @param $fname string Caller function name
1468          * @param $options string|array Query options
1469          * @param $join_conds array|string Join conditions
1470          *
1471          * @return object|bool
1472          */
1473         public function selectRow( $table, $vars, $conds, $fname = 'DatabaseBase::selectRow',
1474                 $options = array(), $join_conds = array() )
1475         {
1476                 $options = (array)$options;
1477                 $options['LIMIT'] = 1;
1478                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1479
1480                 if ( $res === false ) {
1481                         return false;
1482                 }
1483
1484                 if ( !$this->numRows( $res ) ) {
1485                         return false;
1486                 }
1487
1488                 $obj = $this->fetchObject( $res );
1489
1490                 return $obj;
1491         }
1492
1493         /**
1494          * Estimate rows in dataset.
1495          *
1496          * MySQL allows you to estimate the number of rows that would be returned
1497          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1498          * index cardinality statistics, and is notoriously inaccurate, especially
1499          * when large numbers of rows have recently been added or deleted.
1500          *
1501          * For DBMSs that don't support fast result size estimation, this function
1502          * will actually perform the SELECT COUNT(*).
1503          *
1504          * Takes the same arguments as DatabaseBase::select().
1505          *
1506          * @param $table String: table name
1507          * @param Array|string $vars : unused
1508          * @param Array|string $conds : filters on the table
1509          * @param $fname String: function name for profiling
1510          * @param $options Array: options for select
1511          * @return Integer: row count
1512          */
1513         public function estimateRowCount( $table, $vars = '*', $conds = '',
1514                 $fname = 'DatabaseBase::estimateRowCount', $options = array() )
1515         {
1516                 $rows = 0;
1517                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1518
1519                 if ( $res ) {
1520                         $row = $this->fetchRow( $res );
1521                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1522                 }
1523
1524                 return $rows;
1525         }
1526
1527         /**
1528          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1529          * It's only slightly flawed. Don't use for anything important.
1530          *
1531          * @param $sql String A SQL Query
1532          *
1533          * @return string
1534          */
1535         static function generalizeSQL( $sql ) {
1536                 # This does the same as the regexp below would do, but in such a way
1537                 # as to avoid crashing php on some large strings.
1538                 # $sql = preg_replace ( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql);
1539
1540                 $sql = str_replace ( "\\\\", '', $sql );
1541                 $sql = str_replace ( "\\'", '', $sql );
1542                 $sql = str_replace ( "\\\"", '', $sql );
1543                 $sql = preg_replace ( "/'.*'/s", "'X'", $sql );
1544                 $sql = preg_replace ( '/".*"/s', "'X'", $sql );
1545
1546                 # All newlines, tabs, etc replaced by single space
1547                 $sql = preg_replace ( '/\s+/', ' ', $sql );
1548
1549                 # All numbers => N
1550                 $sql = preg_replace ( '/-?[0-9]+/s', 'N', $sql );
1551
1552                 return $sql;
1553         }
1554
1555         /**
1556          * Determines whether a field exists in a table
1557          *
1558          * @param $table String: table name
1559          * @param $field String: filed to check on that table
1560          * @param $fname String: calling function name (optional)
1561          * @return Boolean: whether $table has filed $field
1562          */
1563         public function fieldExists( $table, $field, $fname = 'DatabaseBase::fieldExists' ) {
1564                 $info = $this->fieldInfo( $table, $field );
1565
1566                 return (bool)$info;
1567         }
1568
1569         /**
1570          * Determines whether an index exists
1571          * Usually throws a DBQueryError on failure
1572          * If errors are explicitly ignored, returns NULL on failure
1573          *
1574          * @param $table
1575          * @param $index
1576          * @param $fname string
1577          *
1578          * @return bool|null
1579          */
1580         public function indexExists( $table, $index, $fname = 'DatabaseBase::indexExists' ) {
1581                 $info = $this->indexInfo( $table, $index, $fname );
1582                 if ( is_null( $info ) ) {
1583                         return null;
1584                 } else {
1585                         return $info !== false;
1586                 }
1587         }
1588
1589         /**
1590          * Query whether a given table exists
1591          *
1592          * @param $table string
1593          * @param $fname string
1594          *
1595          * @return bool
1596          */
1597         public function tableExists( $table, $fname = __METHOD__ ) {
1598                 $table = $this->tableName( $table );
1599                 $old = $this->ignoreErrors( true );
1600                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1601                 $this->ignoreErrors( $old );
1602
1603                 return (bool)$res;
1604         }
1605
1606         /**
1607          * mysql_field_type() wrapper
1608          * @param $res
1609          * @param $index
1610          * @return string
1611          */
1612         public function fieldType( $res, $index ) {
1613                 if ( $res instanceof ResultWrapper ) {
1614                         $res = $res->result;
1615                 }
1616
1617                 return mysql_field_type( $res, $index );
1618         }
1619
1620         /**
1621          * Determines if a given index is unique
1622          *
1623          * @param $table string
1624          * @param $index string
1625          *
1626          * @return bool
1627          */
1628         public function indexUnique( $table, $index ) {
1629                 $indexInfo = $this->indexInfo( $table, $index );
1630
1631                 if ( !$indexInfo ) {
1632                         return null;
1633                 }
1634
1635                 return !$indexInfo[0]->Non_unique;
1636         }
1637
1638         /**
1639          * Helper for DatabaseBase::insert().
1640          *
1641          * @param $options array
1642          * @return string
1643          */
1644         protected function makeInsertOptions( $options ) {
1645                 return implode( ' ', $options );
1646         }
1647
1648         /**
1649          * INSERT wrapper, inserts an array into a table.
1650          *
1651          * $a may be either:
1652          *
1653          *   - A single associative array. The array keys are the field names, and
1654          *     the values are the values to insert. The values are treated as data
1655          *     and will be quoted appropriately. If NULL is inserted, this will be
1656          *     converted to a database NULL.
1657          *   - An array with numeric keys, holding a list of associative arrays.
1658          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1659          *     each subarray must be identical to each other, and in the same order.
1660          *
1661          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1662          * returns success.
1663          *
1664          * $options is an array of options, with boolean options encoded as values
1665          * with numeric keys, in the same style as $options in
1666          * DatabaseBase::select(). Supported options are:
1667          *
1668          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1669          *     any rows which cause duplicate key errors are not inserted. It's
1670          *     possible to determine how many rows were successfully inserted using
1671          *     DatabaseBase::affectedRows().
1672          *
1673          * @param $table   String Table name. This will be passed through
1674          *                 DatabaseBase::tableName().
1675          * @param $a       Array of rows to insert
1676          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1677          * @param $options Array of options
1678          *
1679          * @return bool
1680          */
1681         public function insert( $table, $a, $fname = 'DatabaseBase::insert', $options = array() ) {
1682                 # No rows to insert, easy just return now
1683                 if ( !count( $a ) ) {
1684                         return true;
1685                 }
1686
1687                 $table = $this->tableName( $table );
1688
1689                 if ( !is_array( $options ) ) {
1690                         $options = array( $options );
1691                 }
1692
1693                 $options = $this->makeInsertOptions( $options );
1694
1695                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1696                         $multi = true;
1697                         $keys = array_keys( $a[0] );
1698                 } else {
1699                         $multi = false;
1700                         $keys = array_keys( $a );
1701                 }
1702
1703                 $sql = 'INSERT ' . $options .
1704                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1705
1706                 if ( $multi ) {
1707                         $first = true;
1708                         foreach ( $a as $row ) {
1709                                 if ( $first ) {
1710                                         $first = false;
1711                                 } else {
1712                                         $sql .= ',';
1713                                 }
1714                                 $sql .= '(' . $this->makeList( $row ) . ')';
1715                         }
1716                 } else {
1717                         $sql .= '(' . $this->makeList( $a ) . ')';
1718                 }
1719
1720                 return (bool)$this->query( $sql, $fname );
1721         }
1722
1723         /**
1724          * Make UPDATE options for the DatabaseBase::update function
1725          *
1726          * @param $options Array: The options passed to DatabaseBase::update
1727          * @return string
1728          */
1729         protected function makeUpdateOptions( $options ) {
1730                 if ( !is_array( $options ) ) {
1731                         $options = array( $options );
1732                 }
1733
1734                 $opts = array();
1735
1736                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1737                         $opts[] = $this->lowPriorityOption();
1738                 }
1739
1740                 if ( in_array( 'IGNORE', $options ) ) {
1741                         $opts[] = 'IGNORE';
1742                 }
1743
1744                 return implode( ' ', $opts );
1745         }
1746
1747         /**
1748          * UPDATE wrapper. Takes a condition array and a SET array.
1749          *
1750          * @param $table  String name of the table to UPDATE. This will be passed through
1751          *                DatabaseBase::tableName().
1752          *
1753          * @param $values Array:  An array of values to SET. For each array element,
1754          *                the key gives the field name, and the value gives the data
1755          *                to set that field to. The data will be quoted by
1756          *                DatabaseBase::addQuotes().
1757          *
1758          * @param $conds  Array:  An array of conditions (WHERE). See
1759          *                DatabaseBase::select() for the details of the format of
1760          *                condition arrays. Use '*' to update all rows.
1761          *
1762          * @param $fname  String: The function name of the caller (from __METHOD__),
1763          *                for logging and profiling.
1764          *
1765          * @param $options Array: An array of UPDATE options, can be:
1766          *                   - IGNORE: Ignore unique key conflicts
1767          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1768          * @return Boolean
1769          */
1770         function update( $table, $values, $conds, $fname = 'DatabaseBase::update', $options = array() ) {
1771                 $table = $this->tableName( $table );
1772                 $opts = $this->makeUpdateOptions( $options );
1773                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1774
1775                 if ( $conds !== array() && $conds !== '*' ) {
1776                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1777                 }
1778
1779                 return $this->query( $sql, $fname );
1780         }
1781
1782         /**
1783          * Makes an encoded list of strings from an array
1784          * @param $a Array containing the data
1785          * @param int $mode Constant
1786          *      - LIST_COMMA:          comma separated, no field names
1787          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1788          *        the documentation for $conds in DatabaseBase::select().
1789          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1790          *      - LIST_SET:            comma separated with field names, like a SET clause
1791          *      - LIST_NAMES:          comma separated field names
1792          *
1793          * @throws MWException|DBUnexpectedError
1794          * @return string
1795          */
1796         public function makeList( $a, $mode = LIST_COMMA ) {
1797                 if ( !is_array( $a ) ) {
1798                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1799                 }
1800
1801                 $first = true;
1802                 $list = '';
1803
1804                 foreach ( $a as $field => $value ) {
1805                         if ( !$first ) {
1806                                 if ( $mode == LIST_AND ) {
1807                                         $list .= ' AND ';
1808                                 } elseif ( $mode == LIST_OR ) {
1809                                         $list .= ' OR ';
1810                                 } else {
1811                                         $list .= ',';
1812                                 }
1813                         } else {
1814                                 $first = false;
1815                         }
1816
1817                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1818                                 $list .= "($value)";
1819                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1820                                 $list .= "$value";
1821                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1822                                 if ( count( $value ) == 0 ) {
1823                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1824                                 } elseif ( count( $value ) == 1 ) {
1825                                         // Special-case single values, as IN isn't terribly efficient
1826                                         // Don't necessarily assume the single key is 0; we don't
1827                                         // enforce linear numeric ordering on other arrays here.
1828                                         $value = array_values( $value );
1829                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1830                                 } else {
1831                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1832                                 }
1833                         } elseif ( $value === null ) {
1834                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1835                                         $list .= "$field IS ";
1836                                 } elseif ( $mode == LIST_SET ) {
1837                                         $list .= "$field = ";
1838                                 }
1839                                 $list .= 'NULL';
1840                         } else {
1841                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1842                                         $list .= "$field = ";
1843                                 }
1844                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1845                         }
1846                 }
1847
1848                 return $list;
1849         }
1850
1851         /**
1852          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1853          * The keys on each level may be either integers or strings.
1854          *
1855          * @param $data Array: organized as 2-d
1856          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
1857          * @param $baseKey String: field name to match the base-level keys to (eg 'pl_namespace')
1858          * @param $subKey String: field name to match the sub-level keys to (eg 'pl_title')
1859          * @return Mixed: string SQL fragment, or false if no items in array.
1860          */
1861         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1862                 $conds = array();
1863
1864                 foreach ( $data as $base => $sub ) {
1865                         if ( count( $sub ) ) {
1866                                 $conds[] = $this->makeList(
1867                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1868                                         LIST_AND );
1869                         }
1870                 }
1871
1872                 if ( $conds ) {
1873                         return $this->makeList( $conds, LIST_OR );
1874                 } else {
1875                         // Nothing to search for...
1876                         return false;
1877                 }
1878         }
1879
1880         /**
1881          * Return aggregated value alias
1882          *
1883          * @param $valuedata
1884          * @param $valuename string
1885          *
1886          * @return string
1887          */
1888         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1889                 return $valuename;
1890         }
1891
1892         /**
1893          * @param $field
1894          * @return string
1895          */
1896         public function bitNot( $field ) {
1897                 return "(~$field)";
1898         }
1899
1900         /**
1901          * @param $fieldLeft
1902          * @param $fieldRight
1903          * @return string
1904          */
1905         public function bitAnd( $fieldLeft, $fieldRight ) {
1906                 return "($fieldLeft & $fieldRight)";
1907         }
1908
1909         /**
1910          * @param  $fieldLeft
1911          * @param  $fieldRight
1912          * @return string
1913          */
1914         public function bitOr( $fieldLeft, $fieldRight ) {
1915                 return "($fieldLeft | $fieldRight)";
1916         }
1917
1918         /**
1919          * Build a concatenation list to feed into a SQL query
1920          * @param $stringList Array: list of raw SQL expressions; caller is responsible for any quoting
1921          * @return String
1922          */
1923         public function buildConcat( $stringList ) {
1924                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1925         }
1926
1927         /**
1928          * Change the current database
1929          *
1930          * @todo Explain what exactly will fail if this is not overridden.
1931          *
1932          * @param $db
1933          *
1934          * @return bool Success or failure
1935          */
1936         public function selectDB( $db ) {
1937                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
1938                 # if your database engine supports a concept similar to MySQL's
1939                 # databases you may as well.
1940                 $this->mDBname = $db;
1941                 return true;
1942         }
1943
1944         /**
1945          * Get the current DB name
1946          */
1947         public function getDBname() {
1948                 return $this->mDBname;
1949         }
1950
1951         /**
1952          * Get the server hostname or IP address
1953          */
1954         public function getServer() {
1955                 return $this->mServer;
1956         }
1957
1958         /**
1959          * Format a table name ready for use in constructing an SQL query
1960          *
1961          * This does two important things: it quotes the table names to clean them up,
1962          * and it adds a table prefix if only given a table name with no quotes.
1963          *
1964          * All functions of this object which require a table name call this function
1965          * themselves. Pass the canonical name to such functions. This is only needed
1966          * when calling query() directly.
1967          *
1968          * @param $name String: database table name
1969          * @param $format String One of:
1970          *   quoted - Automatically pass the table name through addIdentifierQuotes()
1971          *            so that it can be used in a query.
1972          *   raw - Do not add identifier quotes to the table name
1973          * @return String: full database name
1974          */
1975         public function tableName( $name, $format = 'quoted' ) {
1976                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
1977                 # Skip the entire process when we have a string quoted on both ends.
1978                 # Note that we check the end so that we will still quote any use of
1979                 # use of `database`.table. But won't break things if someone wants
1980                 # to query a database table with a dot in the name.
1981                 if ( $this->isQuotedIdentifier( $name ) ) {
1982                         return $name;
1983                 }
1984
1985                 # Lets test for any bits of text that should never show up in a table
1986                 # name. Basically anything like JOIN or ON which are actually part of
1987                 # SQL queries, but may end up inside of the table value to combine
1988                 # sql. Such as how the API is doing.
1989                 # Note that we use a whitespace test rather than a \b test to avoid
1990                 # any remote case where a word like on may be inside of a table name
1991                 # surrounded by symbols which may be considered word breaks.
1992                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1993                         return $name;
1994                 }
1995
1996                 # Split database and table into proper variables.
1997                 # We reverse the explode so that database.table and table both output
1998                 # the correct table.
1999                 $dbDetails = array_reverse( explode( '.', $name, 2 ) );
2000                 if ( isset( $dbDetails[1] ) ) {
2001                         list( $table, $database ) = $dbDetails;
2002                 } else {
2003                         list( $table ) = $dbDetails;
2004                 }
2005                 $prefix = $this->mTablePrefix; # Default prefix
2006
2007                 # A database name has been specified in input. We don't want any
2008                 # prefixes added.
2009                 if ( isset( $database ) ) {
2010                         $prefix = '';
2011                 }
2012
2013                 # Note that we use the long format because php will complain in in_array if
2014                 # the input is not an array, and will complain in is_array if it is not set.
2015                 if ( !isset( $database ) # Don't use shared database if pre selected.
2016                  && isset( $wgSharedDB ) # We have a shared database
2017                  && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
2018                  && isset( $wgSharedTables )
2019                  && is_array( $wgSharedTables )
2020                  && in_array( $table, $wgSharedTables ) ) { # A shared table is selected
2021                         $database = $wgSharedDB;
2022                         $prefix   = isset( $wgSharedPrefix ) ? $wgSharedPrefix : $prefix;
2023                 }
2024
2025                 # Quote the $database and $table and apply the prefix if not quoted.
2026                 if ( isset( $database ) ) {
2027                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2028                                 $database = $this->addIdentifierQuotes( $database );
2029                         }
2030                 }
2031
2032                 $table = "{$prefix}{$table}";
2033                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $table ) ) {
2034                         $table = $this->addIdentifierQuotes( "{$table}" );
2035                 }
2036
2037                 # Merge our database and table into our final table name.
2038                 $tableName = ( isset( $database ) ? "{$database}.{$table}" : "{$table}" );
2039
2040                 return $tableName;
2041         }
2042
2043         /**
2044          * Fetch a number of table names into an array
2045          * This is handy when you need to construct SQL for joins
2046          *
2047          * Example:
2048          * extract($dbr->tableNames('user','watchlist'));
2049          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2050          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2051          *
2052          * @return array
2053          */
2054         public function tableNames() {
2055                 $inArray = func_get_args();
2056                 $retVal = array();
2057
2058                 foreach ( $inArray as $name ) {
2059                         $retVal[$name] = $this->tableName( $name );
2060                 }
2061
2062                 return $retVal;
2063         }
2064
2065         /**
2066          * Fetch a number of table names into an zero-indexed numerical array
2067          * This is handy when you need to construct SQL for joins
2068          *
2069          * Example:
2070          * list( $user, $watchlist ) = $dbr->tableNamesN('user','watchlist');
2071          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2072          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2073          *
2074          * @return array
2075          */
2076         public function tableNamesN() {
2077                 $inArray = func_get_args();
2078                 $retVal = array();
2079
2080                 foreach ( $inArray as $name ) {
2081                         $retVal[] = $this->tableName( $name );
2082                 }
2083
2084                 return $retVal;
2085         }
2086
2087         /**
2088          * Get an aliased table name
2089          * e.g. tableName AS newTableName
2090          *
2091          * @param $name string Table name, see tableName()
2092          * @param $alias string|bool Alias (optional)
2093          * @return string SQL name for aliased table. Will not alias a table to its own name
2094          */
2095         public function tableNameWithAlias( $name, $alias = false ) {
2096                 if ( !$alias || $alias == $name ) {
2097                         return $this->tableName( $name );
2098                 } else {
2099                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2100                 }
2101         }
2102
2103         /**
2104          * Gets an array of aliased table names
2105          *
2106          * @param $tables array( [alias] => table )
2107          * @return array of strings, see tableNameWithAlias()
2108          */
2109         public function tableNamesWithAlias( $tables ) {
2110                 $retval = array();
2111                 foreach ( $tables as $alias => $table ) {
2112                         if ( is_numeric( $alias ) ) {
2113                                 $alias = $table;
2114                         }
2115                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2116                 }
2117                 return $retval;
2118         }
2119
2120         /**
2121          * Get an aliased field name
2122          * e.g. fieldName AS newFieldName
2123          *
2124          * @param $name string Field name
2125          * @param $alias string|bool Alias (optional)
2126          * @return string SQL name for aliased field. Will not alias a field to its own name
2127          */
2128         public function fieldNameWithAlias( $name, $alias = false ) {
2129                 if ( !$alias || (string)$alias === (string)$name ) {
2130                         return $name;
2131                 } else {
2132                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2133                 }
2134         }
2135
2136         /**
2137          * Gets an array of aliased field names
2138          *
2139          * @param $fields array( [alias] => field )
2140          * @return array of strings, see fieldNameWithAlias()
2141          */
2142         public function fieldNamesWithAlias( $fields ) {
2143                 $retval = array();
2144                 foreach ( $fields as $alias => $field ) {
2145                         if ( is_numeric( $alias ) ) {
2146                                 $alias = $field;
2147                         }
2148                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2149                 }
2150                 return $retval;
2151         }
2152
2153         /**
2154          * Get the aliased table name clause for a FROM clause
2155          * which might have a JOIN and/or USE INDEX clause
2156          *
2157          * @param $tables array ( [alias] => table )
2158          * @param $use_index array Same as for select()
2159          * @param $join_conds array Same as for select()
2160          * @return string
2161          */
2162         protected function tableNamesWithUseIndexOrJOIN(
2163                 $tables, $use_index = array(), $join_conds = array()
2164         ) {
2165                 $ret = array();
2166                 $retJOIN = array();
2167                 $use_index = (array)$use_index;
2168                 $join_conds = (array)$join_conds;
2169
2170                 foreach ( $tables as $alias => $table ) {
2171                         if ( !is_string( $alias ) ) {
2172                                 // No alias? Set it equal to the table name
2173                                 $alias = $table;
2174                         }
2175                         // Is there a JOIN clause for this table?
2176                         if ( isset( $join_conds[$alias] ) ) {
2177                                 list( $joinType, $conds ) = $join_conds[$alias];
2178                                 $tableClause = $joinType;
2179                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2180                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2181                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2182                                         if ( $use != '' ) {
2183                                                 $tableClause .= ' ' . $use;
2184                                         }
2185                                 }
2186                                 $on = $this->makeList( (array)$conds, LIST_AND );
2187                                 if ( $on != '' ) {
2188                                         $tableClause .= ' ON (' . $on . ')';
2189                                 }
2190
2191                                 $retJOIN[] = $tableClause;
2192                         // Is there an INDEX clause for this table?
2193                         } elseif ( isset( $use_index[$alias] ) ) {
2194                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2195                                 $tableClause .= ' ' . $this->useIndexClause(
2196                                         implode( ',', (array)$use_index[$alias] ) );
2197
2198                                 $ret[] = $tableClause;
2199                         } else {
2200                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2201
2202                                 $ret[] = $tableClause;
2203                         }
2204                 }
2205
2206                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2207                 $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2208                 $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2209
2210                 // Compile our final table clause
2211                 return implode( ' ', array( $straightJoins, $otherJoins ) );
2212         }
2213
2214         /**
2215          * Get the name of an index in a given table
2216          *
2217          * @param $index
2218          *
2219          * @return string
2220          */
2221         protected function indexName( $index ) {
2222                 // Backwards-compatibility hack
2223                 $renamed = array(
2224                         'ar_usertext_timestamp' => 'usertext_timestamp',
2225                         'un_user_id'            => 'user_id',
2226                         'un_user_ip'            => 'user_ip',
2227                 );
2228
2229                 if ( isset( $renamed[$index] ) ) {
2230                         return $renamed[$index];
2231                 } else {
2232                         return $index;
2233                 }
2234         }
2235
2236         /**
2237          * If it's a string, adds quotes and backslashes
2238          * Otherwise returns as-is
2239          *
2240          * @param $s string
2241          *
2242          * @return string
2243          */
2244         public function addQuotes( $s ) {
2245                 if ( $s === null ) {
2246                         return 'NULL';
2247                 } else {
2248                         # This will also quote numeric values. This should be harmless,
2249                         # and protects against weird problems that occur when they really
2250                         # _are_ strings such as article titles and string->number->string
2251                         # conversion is not 1:1.
2252                         return "'" . $this->strencode( $s ) . "'";
2253                 }
2254         }
2255
2256         /**
2257          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2258          * MySQL uses `backticks` while basically everything else uses double quotes.
2259          * Since MySQL is the odd one out here the double quotes are our generic
2260          * and we implement backticks in DatabaseMysql.
2261          *
2262          * @param $s string
2263          *
2264          * @return string
2265          */
2266         public function addIdentifierQuotes( $s ) {
2267                 return '"' . str_replace( '"', '""', $s ) . '"';
2268         }
2269
2270         /**
2271          * Returns if the given identifier looks quoted or not according to
2272          * the database convention for quoting identifiers .
2273          *
2274          * @param $name string
2275          *
2276          * @return boolean
2277          */
2278         public function isQuotedIdentifier( $name ) {
2279                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2280         }
2281
2282         /**
2283          * @param $s string
2284          * @return string
2285          */
2286         protected function escapeLikeInternal( $s ) {
2287                 $s = str_replace( '\\', '\\\\', $s );
2288                 $s = $this->strencode( $s );
2289                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2290
2291                 return $s;
2292         }
2293
2294         /**
2295          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2296          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2297          * Alternatively, the function could be provided with an array of aforementioned parameters.
2298          *
2299          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2300          * for subpages of 'My page title'.
2301          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2302          *
2303          * @since 1.16
2304          * @return String: fully built LIKE statement
2305          */
2306         public function buildLike() {
2307                 $params = func_get_args();
2308
2309                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2310                         $params = $params[0];
2311                 }
2312
2313                 $s = '';
2314
2315                 foreach ( $params as $value ) {
2316                         if ( $value instanceof LikeMatch ) {
2317                                 $s .= $value->toString();
2318                         } else {
2319                                 $s .= $this->escapeLikeInternal( $value );
2320                         }
2321                 }
2322
2323                 return " LIKE '" . $s . "' ";
2324         }
2325
2326         /**
2327          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2328          *
2329          * @return LikeMatch
2330          */
2331         public function anyChar() {
2332                 return new LikeMatch( '_' );
2333         }
2334
2335         /**
2336          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2337          *
2338          * @return LikeMatch
2339          */
2340         public function anyString() {
2341                 return new LikeMatch( '%' );
2342         }
2343
2344         /**
2345          * Returns an appropriately quoted sequence value for inserting a new row.
2346          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2347          * subclass will return an integer, and save the value for insertId()
2348          *
2349          * Any implementation of this function should *not* involve reusing
2350          * sequence numbers created for rolled-back transactions.
2351          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2352          * @param $seqName string
2353          * @return null
2354          */
2355         public function nextSequenceValue( $seqName ) {
2356                 return null;
2357         }
2358
2359         /**
2360          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2361          * is only needed because a) MySQL must be as efficient as possible due to
2362          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2363          * which index to pick.  Anyway, other databases might have different
2364          * indexes on a given table.  So don't bother overriding this unless you're
2365          * MySQL.
2366          * @param $index
2367          * @return string
2368          */
2369         public function useIndexClause( $index ) {
2370                 return '';
2371         }
2372
2373         /**
2374          * REPLACE query wrapper.
2375          *
2376          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2377          * except that when there is a duplicate key error, the old row is deleted
2378          * and the new row is inserted in its place.
2379          *
2380          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2381          * perform the delete, we need to know what the unique indexes are so that
2382          * we know how to find the conflicting rows.
2383          *
2384          * It may be more efficient to leave off unique indexes which are unlikely
2385          * to collide. However if you do this, you run the risk of encountering
2386          * errors which wouldn't have occurred in MySQL.
2387          *
2388          * @param $table String: The table to replace the row(s) in.
2389          * @param $rows array Can be either a single row to insert, or multiple rows,
2390          *    in the same format as for DatabaseBase::insert()
2391          * @param $uniqueIndexes array is an array of indexes. Each element may be either
2392          *    a field name or an array of field names
2393          * @param $fname String: Calling function name (use __METHOD__) for logs/profiling
2394          */
2395         public function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseBase::replace' ) {
2396                 $quotedTable = $this->tableName( $table );
2397
2398                 if ( count( $rows ) == 0 ) {
2399                         return;
2400                 }
2401
2402                 # Single row case
2403                 if ( !is_array( reset( $rows ) ) ) {
2404                         $rows = array( $rows );
2405                 }
2406
2407                 foreach( $rows as $row ) {
2408                         # Delete rows which collide
2409                         if ( $uniqueIndexes ) {
2410                                 $sql = "DELETE FROM $quotedTable WHERE ";
2411                                 $first = true;
2412                                 foreach ( $uniqueIndexes as $index ) {
2413                                         if ( $first ) {
2414                                                 $first = false;
2415                                                 $sql .= '( ';
2416                                         } else {
2417                                                 $sql .= ' ) OR ( ';
2418                                         }
2419                                         if ( is_array( $index ) ) {
2420                                                 $first2 = true;
2421                                                 foreach ( $index as $col ) {
2422                                                         if ( $first2 ) {
2423                                                                 $first2 = false;
2424                                                         } else {
2425                                                                 $sql .= ' AND ';
2426                                                         }
2427                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2428                                                 }
2429                                         } else {
2430                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2431                                         }
2432                                 }
2433                                 $sql .= ' )';
2434                                 $this->query( $sql, $fname );
2435                         }
2436
2437                         # Now insert the row
2438                         $this->insert( $table, $row );
2439                 }
2440         }
2441
2442         /**
2443          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2444          * statement.
2445          *
2446          * @param $table string Table name
2447          * @param $rows array Rows to insert
2448          * @param $fname string Caller function name
2449          *
2450          * @return ResultWrapper
2451          */
2452         protected function nativeReplace( $table, $rows, $fname ) {
2453                 $table = $this->tableName( $table );
2454
2455                 # Single row case
2456                 if ( !is_array( reset( $rows ) ) ) {
2457                         $rows = array( $rows );
2458                 }
2459
2460                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2461                 $first = true;
2462
2463                 foreach ( $rows as $row ) {
2464                         if ( $first ) {
2465                                 $first = false;
2466                         } else {
2467                                 $sql .= ',';
2468                         }
2469
2470                         $sql .= '(' . $this->makeList( $row ) . ')';
2471                 }
2472
2473                 return $this->query( $sql, $fname );
2474         }
2475
2476         /**
2477          * DELETE where the condition is a join.
2478          *
2479          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2480          * we use sub-selects
2481          *
2482          * For safety, an empty $conds will not delete everything. If you want to
2483          * delete all rows where the join condition matches, set $conds='*'.
2484          *
2485          * DO NOT put the join condition in $conds.
2486          *
2487          * @param $delTable   String: The table to delete from.
2488          * @param $joinTable  String: The other table.
2489          * @param $delVar     String: The variable to join on, in the first table.
2490          * @param $joinVar    String: The variable to join on, in the second table.
2491          * @param $conds      Array: Condition array of field names mapped to variables,
2492          *                    ANDed together in the WHERE clause
2493          * @param $fname      String: Calling function name (use __METHOD__) for
2494          *                    logs/profiling
2495          * @throws DBUnexpectedError
2496          */
2497         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2498                 $fname = 'DatabaseBase::deleteJoin' )
2499         {
2500                 if ( !$conds ) {
2501                         throw new DBUnexpectedError( $this,
2502                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2503                 }
2504
2505                 $delTable = $this->tableName( $delTable );
2506                 $joinTable = $this->tableName( $joinTable );
2507                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2508                 if ( $conds != '*' ) {
2509                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2510                 }
2511                 $sql .= ')';
2512
2513                 $this->query( $sql, $fname );
2514         }
2515
2516         /**
2517          * Returns the size of a text field, or -1 for "unlimited"
2518          *
2519          * @param $table string
2520          * @param $field string
2521          *
2522          * @return int
2523          */
2524         public function textFieldSize( $table, $field ) {
2525                 $table = $this->tableName( $table );
2526                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2527                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2528                 $row = $this->fetchObject( $res );
2529
2530                 $m = array();
2531
2532                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2533                         $size = $m[1];
2534                 } else {
2535                         $size = -1;
2536                 }
2537
2538                 return $size;
2539         }
2540
2541         /**
2542          * A string to insert into queries to show that they're low-priority, like
2543          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2544          * string and nothing bad should happen.
2545          *
2546          * @return string Returns the text of the low priority option if it is
2547          *   supported, or a blank string otherwise
2548          */
2549         public function lowPriorityOption() {
2550                 return '';
2551         }
2552
2553         /**
2554          * DELETE query wrapper.
2555          *
2556          * @param $table Array Table name
2557          * @param $conds String|Array of conditions. See $conds in DatabaseBase::select() for
2558          *               the format. Use $conds == "*" to delete all rows
2559          * @param $fname String name of the calling function
2560          *
2561          * @throws DBUnexpectedError
2562          * @return bool
2563          */
2564         public function delete( $table, $conds, $fname = 'DatabaseBase::delete' ) {
2565                 if ( !$conds ) {
2566                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2567                 }
2568
2569                 $table = $this->tableName( $table );
2570                 $sql = "DELETE FROM $table";
2571
2572                 if ( $conds != '*' ) {
2573                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2574                 }
2575
2576                 return $this->query( $sql, $fname );
2577         }
2578
2579         /**
2580          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2581          * into another table.
2582          *
2583          * @param $destTable string The table name to insert into
2584          * @param $srcTable string|array May be either a table name, or an array of table names
2585          *    to include in a join.
2586          *
2587          * @param $varMap array must be an associative array of the form
2588          *    array( 'dest1' => 'source1', ...). Source items may be literals
2589          *    rather than field names, but strings should be quoted with
2590          *    DatabaseBase::addQuotes()
2591          *
2592          * @param $conds array Condition array. See $conds in DatabaseBase::select() for
2593          *    the details of the format of condition arrays. May be "*" to copy the
2594          *    whole table.
2595          *
2596          * @param $fname string The function name of the caller, from __METHOD__
2597          *
2598          * @param $insertOptions array Options for the INSERT part of the query, see
2599          *    DatabaseBase::insert() for details.
2600          * @param $selectOptions array Options for the SELECT part of the query, see
2601          *    DatabaseBase::select() for details.
2602          *
2603          * @return ResultWrapper
2604          */
2605         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2606                 $fname = 'DatabaseBase::insertSelect',
2607                 $insertOptions = array(), $selectOptions = array() )
2608         {
2609                 $destTable = $this->tableName( $destTable );
2610
2611                 if ( is_array( $insertOptions ) ) {
2612                         $insertOptions = implode( ' ', $insertOptions );
2613                 }
2614
2615                 if ( !is_array( $selectOptions ) ) {
2616                         $selectOptions = array( $selectOptions );
2617                 }
2618
2619                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2620
2621                 if ( is_array( $srcTable ) ) {
2622                         $srcTable =  implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2623                 } else {
2624                         $srcTable = $this->tableName( $srcTable );
2625                 }
2626
2627                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2628                         " SELECT $startOpts " . implode( ',', $varMap ) .
2629                         " FROM $srcTable $useIndex ";
2630
2631                 if ( $conds != '*' ) {
2632                         if ( is_array( $conds ) ) {
2633                                 $conds = $this->makeList( $conds, LIST_AND );
2634                         }
2635                         $sql .= " WHERE $conds";
2636                 }
2637
2638                 $sql .= " $tailOpts";
2639
2640                 return $this->query( $sql, $fname );
2641         }
2642
2643         /**
2644          * Construct a LIMIT query with optional offset.  This is used for query
2645          * pages.  The SQL should be adjusted so that only the first $limit rows
2646          * are returned.  If $offset is provided as well, then the first $offset
2647          * rows should be discarded, and the next $limit rows should be returned.
2648          * If the result of the query is not ordered, then the rows to be returned
2649          * are theoretically arbitrary.
2650          *
2651          * $sql is expected to be a SELECT, if that makes a difference.
2652          *
2653          * The version provided by default works in MySQL and SQLite.  It will very
2654          * likely need to be overridden for most other DBMSes.
2655          *
2656          * @param $sql String SQL query we will append the limit too
2657          * @param $limit Integer the SQL limit
2658          * @param $offset Integer|bool the SQL offset (default false)
2659          *
2660          * @throws DBUnexpectedError
2661          * @return string
2662          */
2663         public function limitResult( $sql, $limit, $offset = false ) {
2664                 if ( !is_numeric( $limit ) ) {
2665                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2666                 }
2667                 return "$sql LIMIT "
2668                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2669                         . "{$limit} ";
2670         }
2671
2672         /**
2673          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2674          * within the UNION construct.
2675          * @return Boolean
2676          */
2677         public function unionSupportsOrderAndLimit() {
2678                 return true; // True for almost every DB supported
2679         }
2680
2681         /**
2682          * Construct a UNION query
2683          * This is used for providing overload point for other DB abstractions
2684          * not compatible with the MySQL syntax.
2685          * @param $sqls Array: SQL statements to combine
2686          * @param $all Boolean: use UNION ALL
2687          * @return String: SQL fragment
2688          */
2689         public function unionQueries( $sqls, $all ) {
2690                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2691                 return '(' . implode( $glue, $sqls ) . ')';
2692         }
2693
2694         /**
2695          * Returns an SQL expression for a simple conditional.  This doesn't need
2696          * to be overridden unless CASE isn't supported in your DBMS.
2697          *
2698          * @param $cond string|array SQL expression which will result in a boolean value
2699          * @param $trueVal String: SQL expression to return if true
2700          * @param $falseVal String: SQL expression to return if false
2701          * @return String: SQL fragment
2702          */
2703         public function conditional( $cond, $trueVal, $falseVal ) {
2704                 if ( is_array( $cond ) ) {
2705                         $cond = $this->makeList( $cond, LIST_AND );
2706                 }
2707                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2708         }
2709
2710         /**
2711          * Returns a comand for str_replace function in SQL query.
2712          * Uses REPLACE() in MySQL
2713          *
2714          * @param $orig String: column to modify
2715          * @param $old String: column to seek
2716          * @param $new String: column to replace with
2717          *
2718          * @return string
2719          */
2720         public function strreplace( $orig, $old, $new ) {
2721                 return "REPLACE({$orig}, {$old}, {$new})";
2722         }
2723
2724         /**
2725          * Determines how long the server has been up
2726          * STUB
2727          *
2728          * @return int
2729          */
2730         public function getServerUptime() {
2731                 return 0;
2732         }
2733
2734         /**
2735          * Determines if the last failure was due to a deadlock
2736          * STUB
2737          *
2738          * @return bool
2739          */
2740         public function wasDeadlock() {
2741                 return false;
2742         }
2743
2744         /**
2745          * Determines if the last failure was due to a lock timeout
2746          * STUB
2747          *
2748          * @return bool
2749          */
2750         public function wasLockTimeout() {
2751                 return false;
2752         }
2753
2754         /**
2755          * Determines if the last query error was something that should be dealt
2756          * with by pinging the connection and reissuing the query.
2757          * STUB
2758          *
2759          * @return bool
2760          */
2761         public function wasErrorReissuable() {
2762                 return false;
2763         }
2764
2765         /**
2766          * Determines if the last failure was due to the database being read-only.
2767          * STUB
2768          *
2769          * @return bool
2770          */
2771         public function wasReadOnlyError() {
2772                 return false;
2773         }
2774
2775         /**
2776          * Perform a deadlock-prone transaction.
2777          *
2778          * This function invokes a callback function to perform a set of write
2779          * queries. If a deadlock occurs during the processing, the transaction
2780          * will be rolled back and the callback function will be called again.
2781          *
2782          * Usage:
2783          *   $dbw->deadlockLoop( callback, ... );
2784          *
2785          * Extra arguments are passed through to the specified callback function.
2786          *
2787          * Returns whatever the callback function returned on its successful,
2788          * iteration, or false on error, for example if the retry limit was
2789          * reached.
2790          *
2791          * @return bool
2792          */
2793         public function deadlockLoop() {
2794                 $this->begin( __METHOD__ );
2795                 $args = func_get_args();
2796                 $function = array_shift( $args );
2797                 $oldIgnore = $this->ignoreErrors( true );
2798                 $tries = DEADLOCK_TRIES;
2799
2800                 if ( is_array( $function ) ) {
2801                         $fname = $function[0];
2802                 } else {
2803                         $fname = $function;
2804                 }
2805
2806                 do {
2807                         $retVal = call_user_func_array( $function, $args );
2808                         $error = $this->lastError();
2809                         $errno = $this->lastErrno();
2810                         $sql = $this->lastQuery();
2811
2812                         if ( $errno ) {
2813                                 if ( $this->wasDeadlock() ) {
2814                                         # Retry
2815                                         usleep( mt_rand( DEADLOCK_DELAY_MIN, DEADLOCK_DELAY_MAX ) );
2816                                 } else {
2817                                         $this->reportQueryError( $error, $errno, $sql, $fname );
2818                                 }
2819                         }
2820                 } while ( $this->wasDeadlock() && --$tries > 0 );
2821
2822                 $this->ignoreErrors( $oldIgnore );
2823
2824                 if ( $tries <= 0 ) {
2825                         $this->rollback( __METHOD__ );
2826                         $this->reportQueryError( $error, $errno, $sql, $fname );
2827                         return false;
2828                 } else {
2829                         $this->commit( __METHOD__ );
2830                         return $retVal;
2831                 }
2832         }
2833
2834         /**
2835          * Wait for the slave to catch up to a given master position.
2836          *
2837          * @param $pos DBMasterPos object
2838          * @param $timeout Integer: the maximum number of seconds to wait for
2839          *   synchronisation
2840          *
2841          * @return integer: zero if the slave was past that position already,
2842          *   greater than zero if we waited for some period of time, less than
2843          *   zero if we timed out.
2844          */
2845         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2846                 wfProfileIn( __METHOD__ );
2847
2848                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2849                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
2850
2851                         if ( $wait > $timeout * 1e6 ) {
2852                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
2853                                 wfProfileOut( __METHOD__ );
2854                                 return -1;
2855                         } elseif ( $wait > 0 ) {
2856                                 wfDebug( "Fake slave waiting $wait us\n" );
2857                                 usleep( $wait );
2858                                 wfProfileOut( __METHOD__ );
2859                                 return 1;
2860                         } else {
2861                                 wfDebug( "Fake slave up to date ($wait us)\n" );
2862                                 wfProfileOut( __METHOD__ );
2863                                 return 0;
2864                         }
2865                 }
2866
2867                 wfProfileOut( __METHOD__ );
2868
2869                 # Real waits are implemented in the subclass.
2870                 return 0;
2871         }
2872
2873         /**
2874          * Get the replication position of this slave
2875          *
2876          * @return DBMasterPos, or false if this is not a slave.
2877          */
2878         public function getSlavePos() {
2879                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2880                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
2881                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
2882                         return $pos;
2883                 } else {
2884                         # Stub
2885                         return false;
2886                 }
2887         }
2888
2889         /**
2890          * Get the position of this master
2891          *
2892          * @return DBMasterPos, or false if this is not a master
2893          */
2894         public function getMasterPos() {
2895                 if ( $this->mFakeMaster ) {
2896                         return new MySQLMasterPos( 'fake', microtime( true ) );
2897                 } else {
2898                         return false;
2899                 }
2900         }
2901
2902         /**
2903          * Run an anonymous function as soon as there is no transaction pending.
2904          * If there is a transaction and it is rolled back, then the callback is cancelled.
2905          * Callbacks must commit any transactions that they begin.
2906          *
2907          * This is useful for updates to different systems or separate transactions are needed.
2908          *
2909          * @since 1.20
2910          *
2911          * @param Closure $callback
2912          */
2913         final public function onTransactionIdle( Closure $callback ) {
2914                 if ( $this->mTrxLevel ) {
2915                         $this->mTrxIdleCallbacks[] = $callback;
2916                 } else {
2917                         $callback();
2918                 }
2919         }
2920
2921         /**
2922          * Actually run the "on transaction idle" callbacks.
2923          *
2924          * @since 1.20
2925          */
2926         protected function runOnTransactionIdleCallbacks() {
2927                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
2928
2929                 $e = null; // last exception
2930                 do { // callbacks may add callbacks :)
2931                         $callbacks = $this->mTrxIdleCallbacks;
2932                         $this->mTrxIdleCallbacks = array(); // recursion guard
2933                         foreach ( $callbacks as $callback ) {
2934                                 try {
2935                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
2936                                         $callback();
2937                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
2938                                 } catch ( Exception $e ) {}
2939                         }
2940                 } while ( count( $this->mTrxIdleCallbacks ) );
2941
2942                 if ( $e instanceof Exception ) {
2943                         throw $e; // re-throw any last exception
2944                 }
2945         }
2946
2947         /**
2948          * Begin a transaction. If a transaction is already in progress, that transaction will be committed before the
2949          * new transaction is started.
2950          *
2951          * Note that when the DBO_TRX flag is set (which is usually the case for web requests, but not for maintenance scripts),
2952          * any previous database query will have started a transaction automatically.
2953          *
2954          * Nesting of transactions is not supported. Attempts to nest transactions will cause a warning, unless the current
2955          * transaction was started automatically because of the DBO_TRX flag.
2956          *
2957          * @param $fname string
2958          */
2959         final public function begin( $fname = 'DatabaseBase::begin' ) {
2960                 global $wgDebugDBTransactions;
2961
2962                 if ( $this->mTrxLevel ) { // implicit commit
2963                         if ( !$this->mTrxAutomatic ) {
2964                                 // We want to warn about inadvertently nested begin/commit pairs, but not about auto-committing
2965                                 // implicit transactions that were started by query() because DBO_TRX was set.
2966
2967                                 wfWarn( "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
2968                                         " performing implicit commit!" );
2969                         } else {
2970                                 // if the transaction was automatic and has done write operations,
2971                                 // log it if $wgDebugDBTransactions is enabled.
2972
2973                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
2974                                         wfDebug( "$fname: Automatic transaction with writes in progress (from {$this->mTrxFname}), " .
2975                                                 " performing implicit commit!\n" );
2976                                 }
2977                         }
2978
2979                         $this->doCommit( $fname );
2980                         $this->runOnTransactionIdleCallbacks();
2981                 }
2982
2983                 $this->doBegin( $fname );
2984                 $this->mTrxFname = $fname;
2985                 $this->mTrxDoneWrites = false;
2986                 $this->mTrxAutomatic = false;
2987         }
2988
2989         /**
2990          * Issues the BEGIN command to the database server.
2991          *
2992          * @see DatabaseBase::begin()
2993          * @param type $fname
2994          */
2995         protected function doBegin( $fname ) {
2996                 $this->query( 'BEGIN', $fname );
2997                 $this->mTrxLevel = 1;
2998         }
2999
3000         /**
3001          * Commits a transaction previously started using begin().
3002          * If no transaction is in progress, a warning is issued.
3003          *
3004          * Nesting of transactions is not supported.
3005          *
3006          * @param $fname string
3007          * @param $flush String Flush flag, set to 'flush' to disable warnings about explicitly committing implicit
3008          *        transactions, or calling commit when no transaction is in progress.
3009          *        This will silently break any ongoing explicit transaction. Only set the flush flag if you are sure
3010          *        that it is safe to ignore these warnings in your context.
3011          */
3012         final public function commit( $fname = 'DatabaseBase::commit', $flush = '' ) {
3013                 if ( $flush != 'flush' ) {
3014                         if ( !$this->mTrxLevel ) {
3015                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3016                         } elseif( $this->mTrxAutomatic ) {
3017                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3018                         }
3019                 } else {
3020                         if ( !$this->mTrxLevel ) {
3021                                 return; // nothing to do
3022                         } elseif( !$this->mTrxAutomatic ) {
3023                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3024                         }
3025                 }
3026
3027                 $this->doCommit( $fname );
3028                 $this->runOnTransactionIdleCallbacks();
3029         }
3030
3031         /**
3032          * Issues the COMMIT command to the database server.
3033          *
3034          * @see DatabaseBase::commit()
3035          * @param type $fname
3036          */
3037         protected function doCommit( $fname ) {
3038                 if ( $this->mTrxLevel ) {
3039                         $this->query( 'COMMIT', $fname );
3040                         $this->mTrxLevel = 0;
3041                 }
3042         }
3043
3044         /**
3045          * Rollback a transaction previously started using begin().
3046          * If no transaction is in progress, a warning is issued.
3047          *
3048          * No-op on non-transactional databases.
3049          *
3050          * @param $fname string
3051          */
3052         final public function rollback( $fname = 'DatabaseBase::rollback' ) {
3053                 if ( !$this->mTrxLevel ) {
3054                         wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3055                 }
3056                 $this->doRollback( $fname );
3057                 $this->mTrxIdleCallbacks = array(); // cancel
3058         }
3059
3060         /**
3061          * Issues the ROLLBACK command to the database server.
3062          *
3063          * @see DatabaseBase::rollback()
3064          * @param type $fname
3065          */
3066         protected function doRollback( $fname ) {
3067                 if ( $this->mTrxLevel ) {
3068                         $this->query( 'ROLLBACK', $fname, true );
3069                         $this->mTrxLevel = 0;
3070                 }
3071         }
3072
3073         /**
3074          * Creates a new table with structure copied from existing table
3075          * Note that unlike most database abstraction functions, this function does not
3076          * automatically append database prefix, because it works at a lower
3077          * abstraction level.
3078          * The table names passed to this function shall not be quoted (this
3079          * function calls addIdentifierQuotes when needed).
3080          *
3081          * @param $oldName String: name of table whose structure should be copied
3082          * @param $newName String: name of table to be created
3083          * @param $temporary Boolean: whether the new table should be temporary
3084          * @param $fname String: calling function name
3085          * @throws MWException
3086          * @return Boolean: true if operation was successful
3087          */
3088         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3089                 $fname = 'DatabaseBase::duplicateTableStructure' )
3090         {
3091                 throw new MWException(
3092                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3093         }
3094
3095         /**
3096          * List all tables on the database
3097          *
3098          * @param $prefix string Only show tables with this prefix, e.g. mw_
3099          * @param $fname String: calling function name
3100          * @throws MWException
3101          */
3102         function listTables( $prefix = null, $fname = 'DatabaseBase::listTables' ) {
3103                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3104         }
3105
3106         /**
3107          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3108          * to the format used for inserting into timestamp fields in this DBMS.
3109          *
3110          * The result is unquoted, and needs to be passed through addQuotes()
3111          * before it can be included in raw SQL.
3112          *
3113          * @param $ts string|int
3114          *
3115          * @return string
3116          */
3117         public function timestamp( $ts = 0 ) {
3118                 return wfTimestamp( TS_MW, $ts );
3119         }
3120
3121         /**
3122          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3123          * to the format used for inserting into timestamp fields in this DBMS. If
3124          * NULL is input, it is passed through, allowing NULL values to be inserted
3125          * into timestamp fields.
3126          *
3127          * The result is unquoted, and needs to be passed through addQuotes()
3128          * before it can be included in raw SQL.
3129          *
3130          * @param $ts string|int
3131          *
3132          * @return string
3133          */
3134         public function timestampOrNull( $ts = null ) {
3135                 if ( is_null( $ts ) ) {
3136                         return null;
3137                 } else {
3138                         return $this->timestamp( $ts );
3139                 }
3140         }
3141
3142         /**
3143          * Take the result from a query, and wrap it in a ResultWrapper if
3144          * necessary. Boolean values are passed through as is, to indicate success
3145          * of write queries or failure.
3146          *
3147          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3148          * resource, and it was necessary to call this function to convert it to
3149          * a wrapper. Nowadays, raw database objects are never exposed to external
3150          * callers, so this is unnecessary in external code. For compatibility with
3151          * old code, ResultWrapper objects are passed through unaltered.
3152          *
3153          * @param $result bool|ResultWrapper
3154          *
3155          * @return bool|ResultWrapper
3156          */
3157         public function resultObject( $result ) {
3158                 if ( empty( $result ) ) {
3159                         return false;
3160                 } elseif ( $result instanceof ResultWrapper ) {
3161                         return $result;
3162                 } elseif ( $result === true ) {
3163                         // Successful write query
3164                         return $result;
3165                 } else {
3166                         return new ResultWrapper( $this, $result );
3167                 }
3168         }
3169
3170         /**
3171          * Ping the server and try to reconnect if it there is no connection
3172          *
3173          * @return bool Success or failure
3174          */
3175         public function ping() {
3176                 # Stub.  Not essential to override.
3177                 return true;
3178         }
3179
3180         /**
3181          * Get slave lag. Currently supported only by MySQL.
3182          *
3183          * Note that this function will generate a fatal error on many
3184          * installations. Most callers should use LoadBalancer::safeGetLag()
3185          * instead.
3186          *
3187          * @return int Database replication lag in seconds
3188          */
3189         public function getLag() {
3190                 return intval( $this->mFakeSlaveLag );
3191         }
3192
3193         /**
3194          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3195          *
3196          * @return int
3197          */
3198         function maxListLen() {
3199                 return 0;
3200         }
3201
3202         /**
3203          * Some DBMSs have a special format for inserting into blob fields, they
3204          * don't allow simple quoted strings to be inserted. To insert into such
3205          * a field, pass the data through this function before passing it to
3206          * DatabaseBase::insert().
3207          * @param $b string
3208          * @return string
3209          */
3210         public function encodeBlob( $b ) {
3211                 return $b;
3212         }
3213
3214         /**
3215          * Some DBMSs return a special placeholder object representing blob fields
3216          * in result objects. Pass the object through this function to return the
3217          * original string.
3218          * @param $b string
3219          * @return string
3220          */
3221         public function decodeBlob( $b ) {
3222                 return $b;
3223         }
3224
3225         /**
3226          * Override database's default behavior. $options include:
3227          *     'connTimeout' : Set the connection timeout value in seconds.
3228          *                     May be useful for very long batch queries such as
3229          *                     full-wiki dumps, where a single query reads out over
3230          *                     hours or days.
3231          *
3232          * @param $options Array
3233          * @return void
3234          */
3235         public function setSessionOptions( array $options ) {}
3236
3237         /**
3238          * Read and execute SQL commands from a file.
3239          *
3240          * Returns true on success, error string or exception on failure (depending
3241          * on object's error ignore settings).
3242          *
3243          * @param $filename String: File name to open
3244          * @param bool|callable $lineCallback Optional function called before reading each line
3245          * @param bool|callable $resultCallback Optional function called for each MySQL result
3246          * @param bool|string $fname Calling function name or false if name should be
3247          *      generated dynamically using $filename
3248          * @throws MWException
3249          * @return bool|string
3250          */
3251         public function sourceFile(
3252                 $filename, $lineCallback = false, $resultCallback = false, $fname = false
3253         ) {
3254                 wfSuppressWarnings();
3255                 $fp = fopen( $filename, 'r' );
3256                 wfRestoreWarnings();
3257
3258                 if ( false === $fp ) {
3259                         throw new MWException( "Could not open \"{$filename}\".\n" );
3260                 }
3261
3262                 if ( !$fname ) {
3263                         $fname = __METHOD__ . "( $filename )";
3264                 }
3265
3266                 try {
3267                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname );
3268                 }
3269                 catch ( MWException $e ) {
3270                         fclose( $fp );
3271                         throw $e;
3272                 }
3273
3274                 fclose( $fp );
3275
3276                 return $error;
3277         }
3278
3279         /**
3280          * Get the full path of a patch file. Originally based on archive()
3281          * from updaters.inc. Keep in mind this always returns a patch, as
3282          * it fails back to MySQL if no DB-specific patch can be found
3283          *
3284          * @param $patch String The name of the patch, like patch-something.sql
3285          * @return String Full path to patch file
3286          */
3287         public function patchPath( $patch ) {
3288                 global $IP;
3289
3290                 $dbType = $this->getType();
3291                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3292                         return "$IP/maintenance/$dbType/archives/$patch";
3293                 } else {
3294                         return "$IP/maintenance/archives/$patch";
3295                 }
3296         }
3297
3298         /**
3299          * Set variables to be used in sourceFile/sourceStream, in preference to the
3300          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3301          * all. If it's set to false, $GLOBALS will be used.
3302          *
3303          * @param $vars bool|array mapping variable name to value.
3304          */
3305         public function setSchemaVars( $vars ) {
3306                 $this->mSchemaVars = $vars;
3307         }
3308
3309         /**
3310          * Read and execute commands from an open file handle.
3311          *
3312          * Returns true on success, error string or exception on failure (depending
3313          * on object's error ignore settings).
3314          *
3315          * @param $fp Resource: File handle
3316          * @param $lineCallback Callback: Optional function called before reading each line
3317          * @param $resultCallback Callback: Optional function called for each MySQL result
3318          * @param $fname String: Calling function name
3319          * @param $inputCallback Callback: Optional function called for each complete line (ended with ;) sent
3320          * @return bool|string
3321          */
3322         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3323                 $fname = 'DatabaseBase::sourceStream', $inputCallback = false )
3324         {
3325                 $cmd = '';
3326
3327                 while ( !feof( $fp ) ) {
3328                         if ( $lineCallback ) {
3329                                 call_user_func( $lineCallback );
3330                         }
3331
3332                         $line = trim( fgets( $fp ) );
3333
3334                         if ( $line == '' ) {
3335                                 continue;
3336                         }
3337
3338                         if ( '-' == $line[0] && '-' == $line[1] ) {
3339                                 continue;
3340                         }
3341
3342                         if ( $cmd != '' ) {
3343                                 $cmd .= ' ';
3344                         }
3345
3346                         $done = $this->streamStatementEnd( $cmd, $line );
3347
3348                         $cmd .= "$line\n";
3349
3350                         if ( $done || feof( $fp ) ) {
3351                                 $cmd = $this->replaceVars( $cmd );
3352                                 if ( $inputCallback ) {
3353                                         call_user_func( $inputCallback, $cmd );
3354                                 }
3355                                 $res = $this->query( $cmd, $fname );
3356
3357                                 if ( $resultCallback ) {
3358                                         call_user_func( $resultCallback, $res, $this );
3359                                 }
3360
3361                                 if ( false === $res ) {
3362                                         $err = $this->lastError();
3363                                         return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3364                                 }
3365
3366                                 $cmd = '';
3367                         }
3368                 }
3369
3370                 return true;
3371         }
3372
3373         /**
3374          * Called by sourceStream() to check if we've reached a statement end
3375          *
3376          * @param $sql String SQL assembled so far
3377          * @param $newLine String New line about to be added to $sql
3378          * @return Bool Whether $newLine contains end of the statement
3379          */
3380         public function streamStatementEnd( &$sql, &$newLine ) {
3381                 if ( $this->delimiter ) {
3382                         $prev = $newLine;
3383                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3384                         if ( $newLine != $prev ) {
3385                                 return true;
3386                         }
3387                 }
3388                 return false;
3389         }
3390
3391         /**
3392          * Database independent variable replacement. Replaces a set of variables
3393          * in an SQL statement with their contents as given by $this->getSchemaVars().
3394          *
3395          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3396          *
3397          * - '{$var}' should be used for text and is passed through the database's
3398          *   addQuotes method.
3399          * - `{$var}` should be used for identifiers (eg: table and database names),
3400          *   it is passed through the database's addIdentifierQuotes method which
3401          *   can be overridden if the database uses something other than backticks.
3402          * - / *$var* / is just encoded, besides traditional table prefix and
3403          *   table options its use should be avoided.
3404          *
3405          * @param $ins String: SQL statement to replace variables in
3406          * @return String The new SQL statement with variables replaced
3407          */
3408         protected function replaceSchemaVars( $ins ) {
3409                 $vars = $this->getSchemaVars();
3410                 foreach ( $vars as $var => $value ) {
3411                         // replace '{$var}'
3412                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3413                         // replace `{$var}`
3414                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3415                         // replace /*$var*/
3416                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ) , $ins );
3417                 }
3418                 return $ins;
3419         }
3420
3421         /**
3422          * Replace variables in sourced SQL
3423          *
3424          * @param $ins string
3425          *
3426          * @return string
3427          */
3428         protected function replaceVars( $ins ) {
3429                 $ins = $this->replaceSchemaVars( $ins );
3430
3431                 // Table prefixes
3432                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3433                         array( $this, 'tableNameCallback' ), $ins );
3434
3435                 // Index names
3436                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3437                         array( $this, 'indexNameCallback' ), $ins );
3438
3439                 return $ins;
3440         }
3441
3442         /**
3443          * Get schema variables. If none have been set via setSchemaVars(), then
3444          * use some defaults from the current object.
3445          *
3446          * @return array
3447          */
3448         protected function getSchemaVars() {
3449                 if ( $this->mSchemaVars ) {
3450                         return $this->mSchemaVars;
3451                 } else {
3452                         return $this->getDefaultSchemaVars();
3453                 }
3454         }
3455
3456         /**
3457          * Get schema variables to use if none have been set via setSchemaVars().
3458          *
3459          * Override this in derived classes to provide variables for tables.sql
3460          * and SQL patch files.
3461          *
3462          * @return array
3463          */
3464         protected function getDefaultSchemaVars() {
3465                 return array();
3466         }
3467
3468         /**
3469          * Table name callback
3470          *
3471          * @param $matches array
3472          *
3473          * @return string
3474          */
3475         protected function tableNameCallback( $matches ) {
3476                 return $this->tableName( $matches[1] );
3477         }
3478
3479         /**
3480          * Index name callback
3481          *
3482          * @param $matches array
3483          *
3484          * @return string
3485          */
3486         protected function indexNameCallback( $matches ) {
3487                 return $this->indexName( $matches[1] );
3488         }
3489
3490         /**
3491          * Check to see if a named lock is available. This is non-blocking.
3492          *
3493          * @param $lockName String: name of lock to poll
3494          * @param $method String: name of method calling us
3495          * @return Boolean
3496          * @since 1.20
3497          */
3498         public function lockIsFree( $lockName, $method ) {
3499                 return true;
3500         }
3501
3502         /**
3503          * Acquire a named lock
3504          *
3505          * Abstracted from Filestore::lock() so child classes can implement for
3506          * their own needs.
3507          *
3508          * @param $lockName String: name of lock to aquire
3509          * @param $method String: name of method calling us
3510          * @param $timeout Integer: timeout
3511          * @return Boolean
3512          */
3513         public function lock( $lockName, $method, $timeout = 5 ) {
3514                 return true;
3515         }
3516
3517         /**
3518          * Release a lock.
3519          *
3520          * @param $lockName String: Name of lock to release
3521          * @param $method String: Name of method calling us
3522          *
3523          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3524          * by this thread (in which case the lock is not released), and NULL if the named
3525          * lock did not exist
3526          */
3527         public function unlock( $lockName, $method ) {
3528                 return true;
3529         }
3530
3531         /**
3532          * Lock specific tables
3533          *
3534          * @param $read Array of tables to lock for read access
3535          * @param $write Array of tables to lock for write access
3536          * @param $method String name of caller
3537          * @param $lowPriority bool Whether to indicate writes to be LOW PRIORITY
3538          *
3539          * @return bool
3540          */
3541         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3542                 return true;
3543         }
3544
3545         /**
3546          * Unlock specific tables
3547          *
3548          * @param $method String the caller
3549          *
3550          * @return bool
3551          */
3552         public function unlockTables( $method ) {
3553                 return true;
3554         }
3555
3556         /**
3557          * Delete a table
3558          * @param $tableName string
3559          * @param $fName string
3560          * @return bool|ResultWrapper
3561          * @since 1.18
3562          */
3563         public function dropTable( $tableName, $fName = 'DatabaseBase::dropTable' ) {
3564                 if( !$this->tableExists( $tableName, $fName ) ) {
3565                         return false;
3566                 }
3567                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3568                 if( $this->cascadingDeletes() ) {
3569                         $sql .= " CASCADE";
3570                 }
3571                 return $this->query( $sql, $fName );
3572         }
3573
3574         /**
3575          * Get search engine class. All subclasses of this need to implement this
3576          * if they wish to use searching.
3577          *
3578          * @return String
3579          */
3580         public function getSearchEngine() {
3581                 return 'SearchEngineDummy';
3582         }
3583
3584         /**
3585          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3586          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3587          * because "i" sorts after all numbers.
3588          *
3589          * @return String
3590          */
3591         public function getInfinity() {
3592                 return 'infinity';
3593         }
3594
3595         /**
3596          * Encode an expiry time into the DBMS dependent format
3597          *
3598          * @param $expiry String: timestamp for expiry, or the 'infinity' string
3599          * @return String
3600          */
3601         public function encodeExpiry( $expiry ) {
3602                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3603                         ? $this->getInfinity()
3604                         : $this->timestamp( $expiry );
3605         }
3606
3607         /**
3608          * Decode an expiry time into a DBMS independent format
3609          *
3610          * @param $expiry String: DB timestamp field value for expiry
3611          * @param $format integer: TS_* constant, defaults to TS_MW
3612          * @return String
3613          */
3614         public function decodeExpiry( $expiry, $format = TS_MW ) {
3615                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3616                         ? 'infinity'
3617                         : wfTimestamp( $format, $expiry );
3618         }
3619
3620         /**
3621          * Allow or deny "big selects" for this session only. This is done by setting
3622          * the sql_big_selects session variable.
3623          *
3624          * This is a MySQL-specific feature.
3625          *
3626          * @param $value Mixed: true for allow, false for deny, or "default" to
3627          *   restore the initial value
3628          */
3629         public function setBigSelects( $value = true ) {
3630                 // no-op
3631         }
3632
3633         /**
3634          * @since 1.19
3635          */
3636         public function __toString() {
3637                 return (string)$this->mConn;
3638         }
3639
3640         public function __destruct() {
3641                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
3642                         trigger_error( "Transaction idle callbacks still pending." );
3643                 }
3644         }
3645 }