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