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