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