includes/db/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * This file deals with database interface functions
   6  * and query specifics/optimisations.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Database
  25  */
  26
  27 /** Number of times to re-try an operation in case of deadlock */
  28 define( 'DEADLOCK_TRIES', 4 );
  29 /** Minimum time to wait before retry, in microseconds */
  30 define( 'DEADLOCK_DELAY_MIN', 500000 );
  31 /** Maximum time to wait before retry */
  32 define( 'DEADLOCK_DELAY_MAX', 1500000 );
  33
  34 /**
  35  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  36  * following must be implemented to support MediaWiki
  37  *
  38  * @file
  39  * @ingroup Database
  40  */
  41 interface DatabaseType {
  42         /**
  43          * Get the type of the DBMS, as it appears in $wgDBtype.
  44          *
  45          * @return string
  46          */
  47         function getType();
  48
  49         /**
  50          * Open a connection to the database. Usually aborts on failure
  51          *
  52          * @param $server String: database server host
  53          * @param $user String: database user name
  54          * @param $password String: database user password
  55          * @param $dbName String: database name
  56          * @return bool
  57          * @throws DBConnectionError
  58          */
  59         function open( $server, $user, $password, $dbName );
  60
  61         /**
  62          * Fetch the next row from the given result object, in object form.
  63          * Fields can be retrieved with $row->fieldname, with fields acting like
  64          * member variables.
  65          *
  66          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  67          * @return Row object
  68          * @throws DBUnexpectedError Thrown if the database returns an error
  69          */
  70         function fetchObject( $res );
  71
  72         /**
  73          * Fetch the next row from the given result object, in associative array
  74          * form.  Fields are retrieved with $row['fieldname'].
  75          *
  76          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  77          * @return Row object
  78          * @throws DBUnexpectedError Thrown if the database returns an error
  79          */
  80         function fetchRow( $res );
  81
  82         /**
  83          * Get the number of rows in a result object
  84          *
  85          * @param $res Mixed: A SQL result
  86          * @return int
  87          */
  88         function numRows( $res );
  89
  90         /**
  91          * Get the number of fields in a result object
  92          * @see http://www.php.net/mysql_num_fields
  93          *
  94          * @param $res Mixed: A SQL result
  95          * @return int
  96          */
  97         function numFields( $res );
  98
  99         /**
 100          * Get a field name in a result object
 101          * @see http://www.php.net/mysql_field_name
 102          *
 103          * @param $res Mixed: A SQL result
 104          * @param $n Integer
 105          * @return string
 106          */
 107         function fieldName( $res, $n );
 108
 109         /**
 110          * Get the inserted value of an auto-increment row
 111          *
 112          * The value inserted should be fetched from nextSequenceValue()
 113          *
 114          * Example:
 115          * $id = $dbw->nextSequenceValue('page_page_id_seq');
 116          * $dbw->insert('page',array('page_id' => $id));
 117          * $id = $dbw->insertId();
 118          *
 119          * @return int
 120          */
 121         function insertId();
 122
 123         /**
 124          * Change the position of the cursor in a result object
 125          * @see http://www.php.net/mysql_data_seek
 126          *
 127          * @param $res Mixed: A SQL result
 128          * @param $row Mixed: Either MySQL row or ResultWrapper
 129          */
 130         function dataSeek( $res, $row );
 131
 132         /**
 133          * Get the last error number
 134          * @see http://www.php.net/mysql_errno
 135          *
 136          * @return int
 137          */
 138         function lastErrno();
 139
 140         /**
 141          * Get a description of the last error
 142          * @see http://www.php.net/mysql_error
 143          *
 144          * @return string
 145          */
 146         function lastError();
 147
 148         /**
 149          * mysql_fetch_field() wrapper
 150          * Returns false if the field doesn't exist
 151          *
 152          * @param $table string: table name
 153          * @param $field string: field name
 154          *
 155          * @return Field
 156          */
 157         function fieldInfo( $table, $field );
 158
 159         /**
 160          * Get information about an index into an object
 161          * @param $table string: Table name
 162          * @param $index string: Index name
 163          * @param $fname string: Calling function name
 164          * @return Mixed: Database-specific index description class or false if the index does not exist
 165          */
 166         function indexInfo( $table, $index, $fname = 'Database::indexInfo' );
 167
 168         /**
 169          * Get the number of rows affected by the last write query
 170          * @see http://www.php.net/mysql_affected_rows
 171          *
 172          * @return int
 173          */
 174         function affectedRows();
 175
 176         /**
 177          * Wrapper for addslashes()
 178          *
 179          * @param $s string: to be slashed.
 180          * @return string: slashed string.
 181          */
 182         function strencode( $s );
 183
 184         /**
 185          * Returns a wikitext link to the DB's website, e.g.,
 186          *     return "[http://www.mysql.com/ MySQL]";
 187          * Should at least contain plain text, if for some reason
 188          * your database has no website.
 189          *
 190          * @return string: wikitext of a link to the server software's web site
 191          */
 192         static function getSoftwareLink();
 193
 194         /**
 195          * A string describing the current software version, like from
 196          * mysql_get_server_info().
 197          *
 198          * @return string: Version information from the database server.
 199          */
 200         function getServerVersion();
 201
 202         /**
 203          * A string describing the current software version, and possibly
 204          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 205          * Use getServerVersion() to get machine-friendly information.
 206          *
 207          * @return string: Version information from the database server
 208          */
 209         function getServerInfo();
 210 }
 211
 212 /**
 213  * Database abstraction object
 214  * @ingroup Database
 215  */
 216 abstract class DatabaseBase implements DatabaseType {
 217
 218 # ------------------------------------------------------------------------------
 219 # Variables
 220 # ------------------------------------------------------------------------------
 221
 222         protected $mLastQuery = '';
 223         protected $mDoneWrites = false;
 224         protected $mPHPError = false;
 225
 226         protected $mServer, $mUser, $mPassword, $mDBname;
 227
 228         protected $mConn = null;
 229         protected $mOpened = false;
 230
 231         /**
 232          * @since 1.20
 233          * @var array of Closure
 234          */
 235         protected $mTrxIdleCallbacks = array();
 236
 237         protected $mTablePrefix;
 238         protected $mFlags;
 239         protected $mTrxLevel = 0;
 240         protected $mErrorCount = 0;
 241         protected $mLBInfo = array();
 242         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 243         protected $mDefaultBigSelects = null;
 244         protected $mSchemaVars = false;
 245
 246         protected $preparedArgs;
 247
 248         protected $htmlErrors;
 249
 250         protected $delimiter = ';';
 251
 252         /**
 253          * Remembers the function name given for starting the most recent transaction via begin().
 254          * Used to provide additional context for error reporting.
 255          *
 256          * @var String
 257          * @see DatabaseBase::mTrxLevel
 258          */
 259         private $mTrxFname = null;
 260
 261         /**
 262          * Record if possible write queries were done in the last transaction started
 263          *
 264          * @var Bool
 265          * @see DatabaseBase::mTrxLevel
 266          */
 267         private $mTrxDoneWrites = false;
 268
 269         /**
 270          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 271          *
 272          * @var Bool
 273          * @see DatabaseBase::mTrxLevel
 274          */
 275         private $mTrxAutomatic = false;
 276
 277         /**
 278          * @since 1.21
 279          * @var file handle for upgrade
 280          */
 281         protected $fileHandle = null;
 282
 283
 284 # ------------------------------------------------------------------------------
 285 # Accessors
 286 # ------------------------------------------------------------------------------
 287         # These optionally set a variable and return the previous state
 288
 289         /**
 290          * A string describing the current software version, and possibly
 291          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 292          * Use getServerVersion() to get machine-friendly information.
 293          *
 294          * @return string: Version information from the database server
 295          */
 296         public function getServerInfo() {
 297                 return $this->getServerVersion();
 298         }
 299
 300         /**
 301          * @return string: command delimiter used by this database engine
 302          */
 303         public function getDelimiter() {
 304                 return $this->delimiter;
 305         }
 306
 307         /**
 308          * Boolean, controls output of large amounts of debug information.
 309          * @param $debug bool|null
 310          *   - true to enable debugging
 311          *   - false to disable debugging
 312          *   - omitted or null to do nothing
 313          *
 314          * @return bool|null previous value of the flag
 315          */
 316         public function debug( $debug = null ) {
 317                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 318         }
 319
 320         /**
 321          * Turns buffering of SQL result sets on (true) or off (false). Default is
 322          * "on".
 323          *
 324          * Unbuffered queries are very troublesome in MySQL:
 325          *
 326          *   - If another query is executed while the first query is being read
 327          *     out, the first query is killed. This means you can't call normal
 328          *     MediaWiki functions while you are reading an unbuffered query result
 329          *     from a normal wfGetDB() connection.
 330          *
 331          *   - Unbuffered queries cause the MySQL server to use large amounts of
 332          *     memory and to hold broad locks which block other queries.
 333          *
 334          * If you want to limit client-side memory, it's almost always better to
 335          * split up queries into batches using a LIMIT clause than to switch off
 336          * buffering.
 337          *
 338          * @param $buffer null|bool
 339          *
 340          * @return null|bool The previous value of the flag
 341          */
 342         public function bufferResults( $buffer = null ) {
 343                 if ( is_null( $buffer ) ) {
 344                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 345                 } else {
 346                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 347                 }
 348         }
 349
 350         /**
 351          * Turns on (false) or off (true) the automatic generation and sending
 352          * of a "we're sorry, but there has been a database error" page on
 353          * database errors. Default is on (false). When turned off, the
 354          * code should use lastErrno() and lastError() to handle the
 355          * situation as appropriate.
 356          *
 357          * @param $ignoreErrors bool|null
 358          *
 359          * @return bool The previous value of the flag.
 360          */
 361         public function ignoreErrors( $ignoreErrors = null ) {
 362                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 363         }
 364
 365         /**
 366          * Gets or sets the current transaction level.
 367          *
 368          * Historically, transactions were allowed to be "nested". This is no
 369          * longer supported, so this function really only returns a boolean.
 370          *
 371          * @param $level int An integer (0 or 1), or omitted to leave it unchanged.
 372          * @return int The previous value
 373          */
 374         public function trxLevel( $level = null ) {
 375                 return wfSetVar( $this->mTrxLevel, $level );
 376         }
 377
 378         /**
 379          * Get/set the number of errors logged. Only useful when errors are ignored
 380          * @param $count int The count to set, or omitted to leave it unchanged.
 381          * @return int The error count
 382          */
 383         public function errorCount( $count = null ) {
 384                 return wfSetVar( $this->mErrorCount, $count );
 385         }
 386
 387         /**
 388          * Get/set the table prefix.
 389          * @param $prefix string The table prefix to set, or omitted to leave it unchanged.
 390          * @return string The previous table prefix.
 391          */
 392         public function tablePrefix( $prefix = null ) {
 393                 return wfSetVar( $this->mTablePrefix, $prefix );
 394         }
 395
 396         /**
 397          * Set the filehandle to copy write statements to.
 398          *
 399          * @param $fh filehandle
 400          */
 401         public function setFileHandle( $fh ) {
 402                 $this->fileHandle = $fh;
 403         }
 404
 405         /**
 406          * Get properties passed down from the server info array of the load
 407          * balancer.
 408          *
 409          * @param $name string The entry of the info array to get, or null to get the
 410          *   whole array
 411          *
 412          * @return LoadBalancer|null
 413          */
 414         public function getLBInfo( $name = null ) {
 415                 if ( is_null( $name ) ) {
 416                         return $this->mLBInfo;
 417                 } else {
 418                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 419                                 return $this->mLBInfo[$name];
 420                         } else {
 421                                 return null;
 422                         }
 423                 }
 424         }
 425
 426         /**
 427          * Set the LB info array, or a member of it. If called with one parameter,
 428          * the LB info array is set to that parameter. If it is called with two
 429          * parameters, the member with the given name is set to the given value.
 430          *
 431          * @param $name
 432          * @param $value
 433          */
 434         public function setLBInfo( $name, $value = null ) {
 435                 if ( is_null( $value ) ) {
 436                         $this->mLBInfo = $name;
 437                 } else {
 438                         $this->mLBInfo[$name] = $value;
 439                 }
 440         }
 441
 442         /**
 443          * Set lag time in seconds for a fake slave
 444          *
 445          * @param $lag int
 446          */
 447         public function setFakeSlaveLag( $lag ) {
 448                 $this->mFakeSlaveLag = $lag;
 449         }
 450
 451         /**
 452          * Make this connection a fake master
 453          *
 454          * @param $enabled bool
 455          */
 456         public function setFakeMaster( $enabled = true ) {
 457                 $this->mFakeMaster = $enabled;
 458         }
 459
 460         /**
 461          * Returns true if this database supports (and uses) cascading deletes
 462          *
 463          * @return bool
 464          */
 465         public function cascadingDeletes() {
 466                 return false;
 467         }
 468
 469         /**
 470          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 471          *
 472          * @return bool
 473          */
 474         public function cleanupTriggers() {
 475                 return false;
 476         }
 477
 478         /**
 479          * Returns true if this database is strict about what can be put into an IP field.
 480          * Specifically, it uses a NULL value instead of an empty string.
 481          *
 482          * @return bool
 483          */
 484         public function strictIPs() {
 485                 return false;
 486         }
 487
 488         /**
 489          * Returns true if this database uses timestamps rather than integers
 490          *
 491          * @return bool
 492         */
 493         public function realTimestamps() {
 494                 return false;
 495         }
 496
 497         /**
 498          * Returns true if this database does an implicit sort when doing GROUP BY
 499          *
 500          * @return bool
 501          */
 502         public function implicitGroupby() {
 503                 return true;
 504         }
 505
 506         /**
 507          * Returns true if this database does an implicit order by when the column has an index
 508          * For example: SELECT page_title FROM page LIMIT 1
 509          *
 510          * @return bool
 511          */
 512         public function implicitOrderby() {
 513                 return true;
 514         }
 515
 516         /**
 517          * Returns true if this database can do a native search on IP columns
 518          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 519          *
 520          * @return bool
 521          */
 522         public function searchableIPs() {
 523                 return false;
 524         }
 525
 526         /**
 527          * Returns true if this database can use functional indexes
 528          *
 529          * @return bool
 530          */
 531         public function functionalIndexes() {
 532                 return false;
 533         }
 534
 535         /**
 536          * Return the last query that went through DatabaseBase::query()
 537          * @return String
 538          */
 539         public function lastQuery() {
 540                 return $this->mLastQuery;
 541         }
 542
 543         /**
 544          * Returns true if the connection may have been used for write queries.
 545          * Should return true if unsure.
 546          *
 547          * @return bool
 548          */
 549         public function doneWrites() {
 550                 return $this->mDoneWrites;
 551         }
 552
 553         /**
 554          * Returns true if there is a transaction open with possible write
 555          * queries or transaction idle callbacks waiting on it to finish.
 556          *
 557          * @return bool
 558          */
 559         public function writesOrCallbacksPending() {
 560                 return $this->mTrxLevel && ( $this->mTrxDoneWrites || $this->mTrxIdleCallbacks );
 561         }
 562
 563         /**
 564          * Is a connection to the database open?
 565          * @return Boolean
 566          */
 567         public function isOpen() {
 568                 return $this->mOpened;
 569         }
 570
 571         /**
 572          * Set a flag for this connection
 573          *
 574          * @param $flag Integer: DBO_* constants from Defines.php:
 575          *   - DBO_DEBUG: output some debug info (same as debug())
 576          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 577          *   - DBO_IGNORE: ignore errors (same as ignoreErrors())
 578          *   - DBO_TRX: automatically start transactions
 579          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 580          *       and removes it in command line mode
 581          *   - DBO_PERSISTENT: use persistant database connection
 582          */
 583         public function setFlag( $flag ) {
 584                 global $wgDebugDBTransactions;
 585                 $this->mFlags |= $flag;
 586                 if ( ( $flag & DBO_TRX) & $wgDebugDBTransactions ) {
 587                         wfDebug("Implicit transactions are now  disabled.\n");
 588                 }
 589         }
 590
 591         /**
 592          * Clear a flag for this connection
 593          *
 594          * @param $flag: same as setFlag()'s $flag param
 595          */
 596         public function clearFlag( $flag ) {
 597                 global $wgDebugDBTransactions;
 598                 $this->mFlags &= ~$flag;
 599                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 600                         wfDebug("Implicit transactions are now disabled.\n");
 601                 }
 602         }
 603
 604         /**
 605          * Returns a boolean whether the flag $flag is set for this connection
 606          *
 607          * @param $flag: same as setFlag()'s $flag param
 608          * @return Boolean
 609          */
 610         public function getFlag( $flag ) {
 611                 return !!( $this->mFlags & $flag );
 612         }
 613
 614         /**
 615          * General read-only accessor
 616          *
 617          * @param $name string
 618          *
 619          * @return string
 620          */
 621         public function getProperty( $name ) {
 622                 return $this->$name;
 623         }
 624
 625         /**
 626          * @return string
 627          */
 628         public function getWikiID() {
 629                 if ( $this->mTablePrefix ) {
 630                         return "{$this->mDBname}-{$this->mTablePrefix}";
 631                 } else {
 632                         return $this->mDBname;
 633                 }
 634         }
 635
 636         /**
 637          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 638          *
 639          * @return string
 640          */
 641         public function getSchemaPath() {
 642                 global $IP;
 643                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 644                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 645                 } else {
 646                         return "$IP/maintenance/tables.sql";
 647                 }
 648         }
 649
 650 # ------------------------------------------------------------------------------
 651 # Other functions
 652 # ------------------------------------------------------------------------------
 653
 654         /**
 655          * Constructor.
 656          * @param $server String: database server host
 657          * @param $user String: database user name
 658          * @param $password String: database user password
 659          * @param $dbName String: database name
 660          * @param $flags
 661          * @param $tablePrefix String: database table prefixes. By default use the prefix gave in LocalSettings.php
 662          */
 663         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 664                 $flags = 0, $tablePrefix = 'get from global'
 665         ) {
 666                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 667
 668                 $this->mFlags = $flags;
 669
 670                 if ( $this->mFlags & DBO_DEFAULT ) {
 671                         if ( $wgCommandLineMode ) {
 672                                 $this->mFlags &= ~DBO_TRX;
 673                                 if ( $wgDebugDBTransactions ) {
 674                                         wfDebug("Implicit transaction open disabled.\n");
 675                                 }
 676                         } else {
 677                                 $this->mFlags |= DBO_TRX;
 678                                 if ( $wgDebugDBTransactions ) {
 679                                         wfDebug("Implicit transaction open enabled.\n");
 680                                 }
 681                         }
 682                 }
 683
 684                 /** Get the default table prefix*/
 685                 if ( $tablePrefix == 'get from global' ) {
 686                         $this->mTablePrefix = $wgDBprefix;
 687                 } else {
 688                         $this->mTablePrefix = $tablePrefix;
 689                 }
 690
 691                 if ( $user ) {
 692                         $this->open( $server, $user, $password, $dbName );
 693                 }
 694         }
 695
 696         /**
 697          * Called by serialize. Throw an exception when DB connection is serialized.
 698          * This causes problems on some database engines because the connection is
 699          * not restored on unserialize.
 700          */
 701         public function __sleep() {
 702                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 703         }
 704
 705         /**
 706          * Given a DB type, construct the name of the appropriate child class of
 707          * DatabaseBase. This is designed to replace all of the manual stuff like:
 708          *      $class = 'Database' . ucfirst( strtolower( $type ) );
 709          * as well as validate against the canonical list of DB types we have
 710          *
 711          * This factory function is mostly useful for when you need to connect to a
 712          * database other than the MediaWiki default (such as for external auth,
 713          * an extension, et cetera). Do not use this to connect to the MediaWiki
 714          * database. Example uses in core:
 715          * @see LoadBalancer::reallyOpenConnection()
 716          * @see ExternalUser_MediaWiki::initFromCond()
 717          * @see ForeignDBRepo::getMasterDB()
 718          * @see WebInstaller_DBConnect::execute()
 719          *
 720          * @since 1.18
 721          *
 722          * @param $dbType String A possible DB type
 723          * @param $p Array An array of options to pass to the constructor.
 724          *    Valid options are: host, user, password, dbname, flags, tablePrefix
 725          * @return DatabaseBase subclass or null
 726          */
 727         public final static function factory( $dbType, $p = array() ) {
 728                 $canonicalDBTypes = array(
 729                         'mysql', 'postgres', 'sqlite', 'oracle', 'mssql', 'ibm_db2'
 730                 );
 731                 $dbType = strtolower( $dbType );
 732                 $class = 'Database' . ucfirst( $dbType );
 733
 734                 if( in_array( $dbType, $canonicalDBTypes ) || ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) ) {
 735                         return new $class(
 736                                 isset( $p['host'] ) ? $p['host'] : false,
 737                                 isset( $p['user'] ) ? $p['user'] : false,
 738                                 isset( $p['password'] ) ? $p['password'] : false,
 739                                 isset( $p['dbname'] ) ? $p['dbname'] : false,
 740                                 isset( $p['flags'] ) ? $p['flags'] : 0,
 741                                 isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global'
 742                         );
 743                 } else {
 744                         return null;
 745                 }
 746         }
 747
 748         protected function installErrorHandler() {
 749                 $this->mPHPError = false;
 750                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 751                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 752         }
 753
 754         /**
 755          * @return bool|string
 756          */
 757         protected function restoreErrorHandler() {
 758                 restore_error_handler();
 759                 if ( $this->htmlErrors !== false ) {
 760                         ini_set( 'html_errors', $this->htmlErrors );
 761                 }
 762                 if ( $this->mPHPError ) {
 763                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 764                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 765                         return $error;
 766                 } else {
 767                         return false;
 768                 }
 769         }
 770
 771         /**
 772          * @param $errno
 773          * @param $errstr
 774          */
 775         protected function connectionErrorHandler( $errno,  $errstr ) {
 776                 $this->mPHPError = $errstr;
 777         }
 778
 779         /**
 780          * Closes a database connection.
 781          * if it is open : commits any open transactions
 782          *
 783          * @return Bool operation success. true if already closed.
 784          */
 785         public function close() {
 786                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 787                         throw new MWException( "Transaction idle callbacks still pending." );
 788                 }
 789                 $this->mOpened = false;
 790                 if ( $this->mConn ) {
 791                         if ( $this->trxLevel() ) {
 792                                 if ( !$this->mTrxAutomatic ) {
 793                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 794                                                 " performing implicit commit before closing connection!" );
 795                                 }
 796
 797                                 $this->commit( __METHOD__, 'flush' );
 798                         }
 799
 800                         $ret = $this->closeConnection();
 801                         $this->mConn = false;
 802                         return $ret;
 803                 } else {
 804                         return true;
 805                 }
 806         }
 807
 808         /**
 809          * Closes underlying database connection
 810          * @since 1.20
 811          * @return bool: Whether connection was closed successfully
 812          */
 813         protected abstract function closeConnection();
 814
 815         /**
 816          * @param $error String: fallback error message, used if none is given by DB
 817          * @throws DBConnectionError
 818          */
 819         function reportConnectionError( $error = 'Unknown error' ) {
 820                 $myError = $this->lastError();
 821                 if ( $myError ) {
 822                         $error = $myError;
 823                 }
 824
 825                 # New method
 826                 throw new DBConnectionError( $this, $error );
 827         }
 828
 829         /**
 830          * The DBMS-dependent part of query()
 831          *
 832          * @param  $sql String: SQL query.
 833          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 834          */
 835         protected abstract function doQuery( $sql );
 836
 837         /**
 838          * Determine whether a query writes to the DB.
 839          * Should return true if unsure.
 840          *
 841          * @param $sql string
 842          *
 843          * @return bool
 844          */
 845         public function isWriteQuery( $sql ) {
 846                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 847         }
 848
 849         /**
 850          * Run an SQL query and return the result. Normally throws a DBQueryError
 851          * on failure. If errors are ignored, returns false instead.
 852          *
 853          * In new code, the query wrappers select(), insert(), update(), delete(),
 854          * etc. should be used where possible, since they give much better DBMS
 855          * independence and automatically quote or validate user input in a variety
 856          * of contexts. This function is generally only useful for queries which are
 857          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 858          * as CREATE TABLE.
 859          *
 860          * However, the query wrappers themselves should call this function.
 861          *
 862          * @param  $sql        String: SQL query
 863          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 864          *     comment (you can use __METHOD__ or add some extra info)
 865          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 866          *     maybe best to catch the exception instead?
 867          * @throws MWException
 868          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 869          *     for a successful read query, or false on failure if $tempIgnore set
 870          */
 871         public function query( $sql, $fname = '', $tempIgnore = false ) {
 872                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 873                 if ( !Profiler::instance()->isStub() ) {
 874                         # generalizeSQL will probably cut down the query to reasonable
 875                         # logging size most of the time. The substr is really just a sanity check.
 876
 877                         if ( $isMaster ) {
 878                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 879                                 $totalProf = 'DatabaseBase::query-master';
 880                         } else {
 881                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 882                                 $totalProf = 'DatabaseBase::query';
 883                         }
 884
 885                         wfProfileIn( $totalProf );
 886                         wfProfileIn( $queryProf );
 887                 }
 888
 889                 $this->mLastQuery = $sql;
 890                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 891                         # Set a flag indicating that writes have been done
 892                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 893                         $this->mDoneWrites = true;
 894                 }
 895
 896                 # Add a comment for easy SHOW PROCESSLIST interpretation
 897                 global $wgUser;
 898                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 899                         $userName = $wgUser->getName();
 900                         if ( mb_strlen( $userName ) > 15 ) {
 901                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 902                         }
 903                         $userName = str_replace( '/', '', $userName );
 904                 } else {
 905                         $userName = '';
 906                 }
 907
 908                 // Add trace comment to the begin of the sql string, right after the operator.
 909                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 910                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 911
 912                 # If DBO_TRX is set, start a transaction
 913                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 914                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' )
 915                 {
 916                         # Avoid establishing transactions for SHOW and SET statements too -
 917                         # that would delay transaction initializations to once connection
 918                         # is really used by application
 919                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 920                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 921                                 global $wgDebugDBTransactions;
 922                                 if ( $wgDebugDBTransactions ) {
 923                                         wfDebug("Implicit transaction start.\n");
 924                                 }
 925                                 $this->begin( __METHOD__ . " ($fname)" );
 926                                 $this->mTrxAutomatic = true;
 927                         }
 928                 }
 929
 930                 # Keep track of whether the transaction has write queries pending
 931                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
 932                         $this->mTrxDoneWrites = true;
 933                 }
 934
 935                 if ( $this->debug() ) {
 936                         static $cnt = 0;
 937
 938                         $cnt++;
 939                         $sqlx = substr( $commentedSql, 0, 500 );
 940                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 941
 942                         $master = $isMaster ? 'master' : 'slave';
 943                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 944                 }
 945
 946                 if ( istainted( $sql ) & TC_MYSQL ) {
 947                         throw new MWException( 'Tainted query found' );
 948                 }
 949
 950                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 951
 952                 # Do the query and handle errors
 953                 $ret = $this->doQuery( $commentedSql );
 954
 955                 MWDebug::queryTime( $queryId );
 956
 957                 # Try reconnecting if the connection was lost
 958                 if ( false === $ret && $this->wasErrorReissuable() ) {
 959                         # Transaction is gone, like it or not
 960                         $this->mTrxLevel = 0;
 961                         $this->mTrxIdleCallbacks = array(); // cancel
 962                         wfDebug( "Connection lost, reconnecting...\n" );
 963
 964                         if ( $this->ping() ) {
 965                                 wfDebug( "Reconnected\n" );
 966                                 $sqlx = substr( $commentedSql, 0, 500 );
 967                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
 968                                 global $wgRequestTime;
 969                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
 970                                 if ( $elapsed < 300 ) {
 971                                         # Not a database error to lose a transaction after a minute or two
 972                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
 973                                 }
 974                                 $ret = $this->doQuery( $commentedSql );
 975                         } else {
 976                                 wfDebug( "Failed\n" );
 977                         }
 978                 }
 979
 980                 if ( false === $ret ) {
 981                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 982                 }
 983
 984                 if ( !Profiler::instance()->isStub() ) {
 985                         wfProfileOut( $queryProf );
 986                         wfProfileOut( $totalProf );
 987                 }
 988
 989                 return $this->resultObject( $ret );
 990         }
 991
 992         /**
 993          * Report a query error. Log the error, and if neither the object ignore
 994          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
 995          *
 996          * @param $error String
 997          * @param $errno Integer
 998          * @param $sql String
 999          * @param $fname String
1000          * @param $tempIgnore Boolean
1001          * @throws DBQueryError
1002          */
1003         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1004                 # Ignore errors during error handling to avoid infinite recursion
1005                 $ignore = $this->ignoreErrors( true );
1006                 ++$this->mErrorCount;
1007
1008                 if ( $ignore || $tempIgnore ) {
1009                         wfDebug( "SQL ERROR (ignored): $error\n" );
1010                         $this->ignoreErrors( $ignore );
1011                 } else {
1012                         $sql1line = str_replace( "\n", "\\n", $sql );
1013                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
1014                         wfDebug( "SQL ERROR: " . $error . "\n" );
1015                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1016                 }
1017         }
1018
1019         /**
1020          * Intended to be compatible with the PEAR::DB wrapper functions.
1021          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1022          *
1023          * ? = scalar value, quoted as necessary
1024          * ! = raw SQL bit (a function for instance)
1025          * & = filename; reads the file and inserts as a blob
1026          *     (we don't use this though...)
1027          *
1028          * @param $sql string
1029          * @param $func string
1030          *
1031          * @return array
1032          */
1033         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1034                 /* MySQL doesn't support prepared statements (yet), so just
1035                    pack up the query for reference. We'll manually replace
1036                    the bits later. */
1037                 return array( 'query' => $sql, 'func' => $func );
1038         }
1039
1040         /**
1041          * Free a prepared query, generated by prepare().
1042          * @param $prepared
1043          */
1044         protected function freePrepared( $prepared ) {
1045                 /* No-op by default */
1046         }
1047
1048         /**
1049          * Execute a prepared query with the various arguments
1050          * @param $prepared String: the prepared sql
1051          * @param $args Mixed: Either an array here, or put scalars as varargs
1052          *
1053          * @return ResultWrapper
1054          */
1055         public function execute( $prepared, $args = null ) {
1056                 if ( !is_array( $args ) ) {
1057                         # Pull the var args
1058                         $args = func_get_args();
1059                         array_shift( $args );
1060                 }
1061
1062                 $sql = $this->fillPrepared( $prepared['query'], $args );
1063
1064                 return $this->query( $sql, $prepared['func'] );
1065         }
1066
1067         /**
1068          * For faking prepared SQL statements on DBs that don't support it directly.
1069          *
1070          * @param $preparedQuery String: a 'preparable' SQL statement
1071          * @param $args Array of arguments to fill it with
1072          * @return string executable SQL
1073          */
1074         public function fillPrepared( $preparedQuery, $args ) {
1075                 reset( $args );
1076                 $this->preparedArgs =& $args;
1077
1078                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1079                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1080         }
1081
1082         /**
1083          * preg_callback func for fillPrepared()
1084          * The arguments should be in $this->preparedArgs and must not be touched
1085          * while we're doing this.
1086          *
1087          * @param $matches Array
1088          * @throws DBUnexpectedError
1089          * @return String
1090          */
1091         protected function fillPreparedArg( $matches ) {
1092                 switch( $matches[1] ) {
1093                         case '\\?': return '?';
1094                         case '\\!': return '!';
1095                         case '\\&': return '&';
1096                 }
1097
1098                 list( /* $n */ , $arg ) = each( $this->preparedArgs );
1099
1100                 switch( $matches[1] ) {
1101                         case '?': return $this->addQuotes( $arg );
1102                         case '!': return $arg;
1103                         case '&':
1104                                 # return $this->addQuotes( file_get_contents( $arg ) );
1105                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1106                         default:
1107                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1108                 }
1109         }
1110
1111         /**
1112          * Free a result object returned by query() or select(). It's usually not
1113          * necessary to call this, just use unset() or let the variable holding
1114          * the result object go out of scope.
1115          *
1116          * @param $res Mixed: A SQL result
1117          */
1118         public function freeResult( $res ) {}
1119
1120         /**
1121          * A SELECT wrapper which returns a single field from a single result row.
1122          *
1123          * Usually throws a DBQueryError on failure. If errors are explicitly
1124          * ignored, returns false on failure.
1125          *
1126          * If no result rows are returned from the query, false is returned.
1127          *
1128          * @param $table string|array Table name. See DatabaseBase::select() for details.
1129          * @param $var string The field name to select. This must be a valid SQL
1130          *   fragment: do not use unvalidated user input.
1131          * @param $cond string|array The condition array. See DatabaseBase::select() for details.
1132          * @param $fname string The function name of the caller.
1133          * @param $options string|array The query options. See DatabaseBase::select() for details.
1134          *
1135          * @return bool|mixed The value from the field, or false on failure.
1136          */
1137         public function selectField( $table, $var, $cond = '', $fname = 'DatabaseBase::selectField',
1138                 $options = array() )
1139         {
1140                 if ( !is_array( $options ) ) {
1141                         $options = array( $options );
1142                 }
1143
1144                 $options['LIMIT'] = 1;
1145
1146                 $res = $this->select( $table, $var, $cond, $fname, $options );
1147
1148                 if ( $res === false || !$this->numRows( $res ) ) {
1149                         return false;
1150                 }
1151
1152                 $row = $this->fetchRow( $res );
1153
1154                 if ( $row !== false ) {
1155                         return reset( $row );
1156                 } else {
1157                         return false;
1158                 }
1159         }
1160
1161         /**
1162          * Returns an optional USE INDEX clause to go after the table, and a
1163          * string to go at the end of the query.
1164          *
1165          * @param $options Array: associative array of options to be turned into
1166          *              an SQL query, valid keys are listed in the function.
1167          * @return Array
1168          * @see DatabaseBase::select()
1169          */
1170         public function makeSelectOptions( $options ) {
1171                 $preLimitTail = $postLimitTail = '';
1172                 $startOpts = '';
1173
1174                 $noKeyOptions = array();
1175
1176                 foreach ( $options as $key => $option ) {
1177                         if ( is_numeric( $key ) ) {
1178                                 $noKeyOptions[$option] = true;
1179                         }
1180                 }
1181
1182                 if ( isset( $options['GROUP BY'] ) ) {
1183                         $gb = is_array( $options['GROUP BY'] )
1184                                 ? implode( ',', $options['GROUP BY'] )
1185                                 : $options['GROUP BY'];
1186                         $preLimitTail .= " GROUP BY {$gb}";
1187                 }
1188
1189                 if ( isset( $options['HAVING'] ) ) {
1190                         $having = is_array( $options['HAVING'] )
1191                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1192                                 : $options['HAVING'];
1193                         $preLimitTail .= " HAVING {$having}";
1194                 }
1195
1196                 if ( isset( $options['ORDER BY'] ) ) {
1197                         $ob = is_array( $options['ORDER BY'] )
1198                                 ? implode( ',', $options['ORDER BY'] )
1199                                 : $options['ORDER BY'];
1200                         $preLimitTail .= " ORDER BY {$ob}";
1201                 }
1202
1203                 // if (isset($options['LIMIT'])) {
1204                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1205                 //              isset($options['OFFSET']) ? $options['OFFSET']
1206                 //              : false);
1207                 // }
1208
1209                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1210                         $postLimitTail .= ' FOR UPDATE';
1211                 }
1212
1213                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1214                         $postLimitTail .= ' LOCK IN SHARE MODE';
1215                 }
1216
1217                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1218                         $startOpts .= 'DISTINCT';
1219                 }
1220
1221                 # Various MySQL extensions
1222                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1223                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1224                 }
1225
1226                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1227                         $startOpts .= ' HIGH_PRIORITY';
1228                 }
1229
1230                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1231                         $startOpts .= ' SQL_BIG_RESULT';
1232                 }
1233
1234                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1235                         $startOpts .= ' SQL_BUFFER_RESULT';
1236                 }
1237
1238                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1239                         $startOpts .= ' SQL_SMALL_RESULT';
1240                 }
1241
1242                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1243                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1244                 }
1245
1246                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1247                         $startOpts .= ' SQL_CACHE';
1248                 }
1249
1250                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1251                         $startOpts .= ' SQL_NO_CACHE';
1252                 }
1253
1254                 if ( isset( $options['USE INDEX'] ) && ! is_array( $options['USE INDEX'] ) ) {
1255                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1256                 } else {
1257                         $useIndex = '';
1258                 }
1259
1260                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1261         }
1262
1263         /**
1264          * Execute a SELECT query constructed using the various parameters provided.
1265          * See below for full details of the parameters.
1266          *
1267          * @param $table String|Array Table name
1268          * @param $vars String|Array Field names
1269          * @param $conds String|Array Conditions
1270          * @param $fname String Caller function name
1271          * @param $options Array Query options
1272          * @param $join_conds Array Join conditions
1273          *
1274          * @param $table string|array
1275          *
1276          * May be either an array of table names, or a single string holding a table
1277          * name. If an array is given, table aliases can be specified, for example:
1278          *
1279          *    array( 'a' => 'user' )
1280          *
1281          * This includes the user table in the query, with the alias "a" available
1282          * for use in field names (e.g. a.user_name).
1283          *
1284          * All of the table names given here are automatically run through
1285          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1286          * added, and various other table name mappings to be performed.
1287          *
1288          *
1289          * @param $vars string|array
1290          *
1291          * May be either a field name or an array of field names. The field names
1292          * can be complete fragments of SQL, for direct inclusion into the SELECT
1293          * query. If an array is given, field aliases can be specified, for example:
1294          *
1295          *   array( 'maxrev' => 'MAX(rev_id)' )
1296          *
1297          * This includes an expression with the alias "maxrev" in the query.
1298          *
1299          * If an expression is given, care must be taken to ensure that it is
1300          * DBMS-independent.
1301          *
1302          *
1303          * @param $conds string|array
1304          *
1305          * May be either a string containing a single condition, or an array of
1306          * conditions. If an array is given, the conditions constructed from each
1307          * element are combined with AND.
1308          *
1309          * Array elements may take one of two forms:
1310          *
1311          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1312          *   - Elements with a string key are interpreted as equality conditions,
1313          *     where the key is the field name.
1314          *     - If the value of such an array element is a scalar (such as a
1315          *       string), it will be treated as data and thus quoted appropriately.
1316          *       If it is null, an IS NULL clause will be added.
1317          *     - If the value is an array, an IN(...) clause will be constructed,
1318          *       such that the field name may match any of the elements in the
1319          *       array. The elements of the array will be quoted.
1320          *
1321          * Note that expressions are often DBMS-dependent in their syntax.
1322          * DBMS-independent wrappers are provided for constructing several types of
1323          * expression commonly used in condition queries. See:
1324          *    - DatabaseBase::buildLike()
1325          *    - DatabaseBase::conditional()
1326          *
1327          *
1328          * @param $options string|array
1329          *
1330          * Optional: Array of query options. Boolean options are specified by
1331          * including them in the array as a string value with a numeric key, for
1332          * example:
1333          *
1334          *    array( 'FOR UPDATE' )
1335          *
1336          * The supported options are:
1337          *
1338          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1339          *     with LIMIT can theoretically be used for paging through a result set,
1340          *     but this is discouraged in MediaWiki for performance reasons.
1341          *
1342          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1343          *     and then the first rows are taken until the limit is reached. LIMIT
1344          *     is applied to a result set after OFFSET.
1345          *
1346          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1347          *     changed until the next COMMIT.
1348          *
1349          *   - DISTINCT: Boolean: return only unique result rows.
1350          *
1351          *   - GROUP BY: May be either an SQL fragment string naming a field or
1352          *     expression to group by, or an array of such SQL fragments.
1353          *
1354          *   - HAVING: May be either an string containing a HAVING clause or an array of
1355          *     conditions building the HAVING clause. If an array is given, the conditions
1356          *     constructed from each element are combined with AND.
1357          *
1358          *   - ORDER BY: May be either an SQL fragment giving a field name or
1359          *     expression to order by, or an array of such SQL fragments.
1360          *
1361          *   - USE INDEX: This may be either a string giving the index name to use
1362          *     for the query, or an array. If it is an associative array, each key
1363          *     gives the table name (or alias), each value gives the index name to
1364          *     use for that table. All strings are SQL fragments and so should be
1365          *     validated by the caller.
1366          *
1367          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1368          *     instead of SELECT.
1369          *
1370          * And also the following boolean MySQL extensions, see the MySQL manual
1371          * for documentation:
1372          *
1373          *    - LOCK IN SHARE MODE
1374          *    - STRAIGHT_JOIN
1375          *    - HIGH_PRIORITY
1376          *    - SQL_BIG_RESULT
1377          *    - SQL_BUFFER_RESULT
1378          *    - SQL_SMALL_RESULT
1379          *    - SQL_CALC_FOUND_ROWS
1380          *    - SQL_CACHE
1381          *    - SQL_NO_CACHE
1382          *
1383          *
1384          * @param $join_conds string|array
1385          *
1386          * Optional associative array of table-specific join conditions. In the
1387          * most common case, this is unnecessary, since the join condition can be
1388          * in $conds. However, it is useful for doing a LEFT JOIN.
1389          *
1390          * The key of the array contains the table name or alias. The value is an
1391          * array with two elements, numbered 0 and 1. The first gives the type of
1392          * join, the second is an SQL fragment giving the join condition for that
1393          * table. For example:
1394          *
1395          *    array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
1396          *
1397          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1398          *   with no rows in it will be returned. If there was a query error, a
1399          *   DBQueryError exception will be thrown, except if the "ignore errors"
1400          *   option was set, in which case false will be returned.
1401          */
1402         public function select( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1403                 $options = array(), $join_conds = array() ) {
1404                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1405
1406                 return $this->query( $sql, $fname );
1407         }
1408
1409         /**
1410          * The equivalent of DatabaseBase::select() except that the constructed SQL
1411          * is returned, instead of being immediately executed. This can be useful for
1412          * doing UNION queries, where the SQL text of each query is needed. In general,
1413          * however, callers outside of Database classes should just use select().
1414          *
1415          * @param $table string|array Table name
1416          * @param $vars string|array Field names
1417          * @param $conds string|array Conditions
1418          * @param $fname string Caller function name
1419          * @param $options string|array Query options
1420          * @param $join_conds string|array Join conditions
1421          *
1422          * @return string SQL query string.
1423          * @see DatabaseBase::select()
1424          */
1425         public function selectSQLText( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1426                 $options = array(), $join_conds = array() )
1427         {
1428                 if ( is_array( $vars ) ) {
1429                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1430                 }
1431
1432                 $options = (array)$options;
1433
1434                 if ( is_array( $table ) ) {
1435                         $useIndex = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1436                                 ? $options['USE INDEX']
1437                                 : array();
1438                         if ( count( $join_conds ) || count( $useIndex ) ) {
1439                                 $from = ' FROM ' .
1440                                         $this->tableNamesWithUseIndexOrJOIN( $table, $useIndex, $join_conds );
1441                         } else {
1442                                 $from = ' FROM ' . implode( ',', $this->tableNamesWithAlias( $table ) );
1443                         }
1444                 } elseif ( $table != '' ) {
1445                         if ( $table[0] == ' ' ) {
1446                                 $from = ' FROM ' . $table;
1447                         } else {
1448                                 $from = ' FROM ' . $this->tableName( $table );
1449                         }
1450                 } else {
1451                         $from = '';
1452                 }
1453
1454                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) = $this->makeSelectOptions( $options );
1455
1456                 if ( !empty( $conds ) ) {
1457                         if ( is_array( $conds ) ) {
1458                                 $conds = $this->makeList( $conds, LIST_AND );
1459                         }
1460                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1461                 } else {
1462                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1463                 }
1464
1465                 if ( isset( $options['LIMIT'] ) ) {
1466                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1467                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1468                 }
1469                 $sql = "$sql $postLimitTail";
1470
1471                 if ( isset( $options['EXPLAIN'] ) ) {
1472                         $sql = 'EXPLAIN ' . $sql;
1473                 }
1474
1475                 return $sql;
1476         }
1477
1478         /**
1479          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1480          * that a single row object is returned. If the query returns no rows,
1481          * false is returned.
1482          *
1483          * @param $table string|array Table name
1484          * @param $vars string|array Field names
1485          * @param $conds array Conditions
1486          * @param $fname string Caller function name
1487          * @param $options string|array Query options
1488          * @param $join_conds array|string Join conditions
1489          *
1490          * @return object|bool
1491          */
1492         public function selectRow( $table, $vars, $conds, $fname = 'DatabaseBase::selectRow',
1493                 $options = array(), $join_conds = array() )
1494         {
1495                 $options = (array)$options;
1496                 $options['LIMIT'] = 1;
1497                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1498
1499                 if ( $res === false ) {
1500                         return false;
1501                 }
1502
1503                 if ( !$this->numRows( $res ) ) {
1504                         return false;
1505                 }
1506
1507                 $obj = $this->fetchObject( $res );
1508
1509                 return $obj;
1510         }
1511
1512         /**
1513          * Estimate rows in dataset.
1514          *
1515          * MySQL allows you to estimate the number of rows that would be returned
1516          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1517          * index cardinality statistics, and is notoriously inaccurate, especially
1518          * when large numbers of rows have recently been added or deleted.
1519          *
1520          * For DBMSs that don't support fast result size estimation, this function
1521          * will actually perform the SELECT COUNT(*).
1522          *
1523          * Takes the same arguments as DatabaseBase::select().
1524          *
1525          * @param $table String: table name
1526          * @param Array|string $vars : unused
1527          * @param Array|string $conds : filters on the table
1528          * @param $fname String: function name for profiling
1529          * @param $options Array: options for select
1530          * @return Integer: row count
1531          */
1532         public function estimateRowCount( $table, $vars = '*', $conds = '',
1533                 $fname = 'DatabaseBase::estimateRowCount', $options = array() )
1534         {
1535                 $rows = 0;
1536                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1537
1538                 if ( $res ) {
1539                         $row = $this->fetchRow( $res );
1540                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1541                 }
1542
1543                 return $rows;
1544         }
1545
1546         /**
1547          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1548          * It's only slightly flawed. Don't use for anything important.
1549          *
1550          * @param $sql String A SQL Query
1551          *
1552          * @return string
1553          */
1554         static function generalizeSQL( $sql ) {
1555                 # This does the same as the regexp below would do, but in such a way
1556                 # as to avoid crashing php on some large strings.
1557                 # $sql = preg_replace ( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql);
1558
1559                 $sql = str_replace ( "\\\\", '', $sql );
1560                 $sql = str_replace ( "\\'", '', $sql );
1561                 $sql = str_replace ( "\\\"", '', $sql );
1562                 $sql = preg_replace ( "/'.*'/s", "'X'", $sql );
1563                 $sql = preg_replace ( '/".*"/s', "'X'", $sql );
1564
1565                 # All newlines, tabs, etc replaced by single space
1566                 $sql = preg_replace ( '/\s+/', ' ', $sql );
1567
1568                 # All numbers => N
1569                 $sql = preg_replace ( '/-?[0-9]+/s', 'N', $sql );
1570
1571                 return $sql;
1572         }
1573
1574         /**
1575          * Determines whether a field exists in a table
1576          *
1577          * @param $table String: table name
1578          * @param $field String: filed to check on that table
1579          * @param $fname String: calling function name (optional)
1580          * @return Boolean: whether $table has filed $field
1581          */
1582         public function fieldExists( $table, $field, $fname = 'DatabaseBase::fieldExists' ) {
1583                 $info = $this->fieldInfo( $table, $field );
1584
1585                 return (bool)$info;
1586         }
1587
1588         /**
1589          * Determines whether an index exists
1590          * Usually throws a DBQueryError on failure
1591          * If errors are explicitly ignored, returns NULL on failure
1592          *
1593          * @param $table
1594          * @param $index
1595          * @param $fname string
1596          *
1597          * @return bool|null
1598          */
1599         public function indexExists( $table, $index, $fname = 'DatabaseBase::indexExists' ) {
1600                 if( !$this->tableExists( $table ) ) {
1601                         return null;
1602                 }
1603
1604                 $info = $this->indexInfo( $table, $index, $fname );
1605                 if ( is_null( $info ) ) {
1606                         return null;
1607                 } else {
1608                         return $info !== false;
1609                 }
1610         }
1611
1612         /**
1613          * Query whether a given table exists
1614          *
1615          * @param $table string
1616          * @param $fname string
1617          *
1618          * @return bool
1619          */
1620         public function tableExists( $table, $fname = __METHOD__ ) {
1621                 $table = $this->tableName( $table );
1622                 $old = $this->ignoreErrors( true );
1623                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1624                 $this->ignoreErrors( $old );
1625
1626                 return (bool)$res;
1627         }
1628
1629         /**
1630          * mysql_field_type() wrapper
1631          * @param $res
1632          * @param $index
1633          * @return string
1634          */
1635         public function fieldType( $res, $index ) {
1636                 if ( $res instanceof ResultWrapper ) {
1637                         $res = $res->result;
1638                 }
1639
1640                 return mysql_field_type( $res, $index );
1641         }
1642
1643         /**
1644          * Determines if a given index is unique
1645          *
1646          * @param $table string
1647          * @param $index string
1648          *
1649          * @return bool
1650          */
1651         public function indexUnique( $table, $index ) {
1652                 $indexInfo = $this->indexInfo( $table, $index );
1653
1654                 if ( !$indexInfo ) {
1655                         return null;
1656                 }
1657
1658                 return !$indexInfo[0]->Non_unique;
1659         }
1660
1661         /**
1662          * Helper for DatabaseBase::insert().
1663          *
1664          * @param $options array
1665          * @return string
1666          */
1667         protected function makeInsertOptions( $options ) {
1668                 return implode( ' ', $options );
1669         }
1670
1671         /**
1672          * INSERT wrapper, inserts an array into a table.
1673          *
1674          * $a may be either:
1675          *
1676          *   - A single associative array. The array keys are the field names, and
1677          *     the values are the values to insert. The values are treated as data
1678          *     and will be quoted appropriately. If NULL is inserted, this will be
1679          *     converted to a database NULL.
1680          *   - An array with numeric keys, holding a list of associative arrays.
1681          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1682          *     each subarray must be identical to each other, and in the same order.
1683          *
1684          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1685          * returns success.
1686          *
1687          * $options is an array of options, with boolean options encoded as values
1688          * with numeric keys, in the same style as $options in
1689          * DatabaseBase::select(). Supported options are:
1690          *
1691          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1692          *     any rows which cause duplicate key errors are not inserted. It's
1693          *     possible to determine how many rows were successfully inserted using
1694          *     DatabaseBase::affectedRows().
1695          *
1696          * @param $table   String Table name. This will be passed through
1697          *                 DatabaseBase::tableName().
1698          * @param $a       Array of rows to insert
1699          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1700          * @param $options Array of options
1701          *
1702          * @return bool
1703          */
1704         public function insert( $table, $a, $fname = 'DatabaseBase::insert', $options = array() ) {
1705                 # No rows to insert, easy just return now
1706                 if ( !count( $a ) ) {
1707                         return true;
1708                 }
1709
1710                 $table = $this->tableName( $table );
1711
1712                 if ( !is_array( $options ) ) {
1713                         $options = array( $options );
1714                 }
1715
1716                 $fh = null;
1717                 if ( isset( $options['fileHandle'] ) ) {
1718                         $fh = $options['fileHandle'];
1719                 }
1720                 $options = $this->makeInsertOptions( $options );
1721
1722                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1723                         $multi = true;
1724                         $keys = array_keys( $a[0] );
1725                 } else {
1726                         $multi = false;
1727                         $keys = array_keys( $a );
1728                 }
1729
1730                 $sql = 'INSERT ' . $options .
1731                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1732
1733                 if ( $multi ) {
1734                         $first = true;
1735                         foreach ( $a as $row ) {
1736                                 if ( $first ) {
1737                                         $first = false;
1738                                 } else {
1739                                         $sql .= ',';
1740                                 }
1741                                 $sql .= '(' . $this->makeList( $row ) . ')';
1742                         }
1743                 } else {
1744                         $sql .= '(' . $this->makeList( $a ) . ')';
1745                 }
1746
1747                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1748                         return false;
1749                 } elseif ( $fh !== null ) {
1750                         return true;
1751                 }
1752
1753                 return (bool)$this->query( $sql, $fname );
1754         }
1755
1756         /**
1757          * Make UPDATE options for the DatabaseBase::update function
1758          *
1759          * @param $options Array: The options passed to DatabaseBase::update
1760          * @return string
1761          */
1762         protected function makeUpdateOptions( $options ) {
1763                 if ( !is_array( $options ) ) {
1764                         $options = array( $options );
1765                 }
1766
1767                 $opts = array();
1768
1769                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1770                         $opts[] = $this->lowPriorityOption();
1771                 }
1772
1773                 if ( in_array( 'IGNORE', $options ) ) {
1774                         $opts[] = 'IGNORE';
1775                 }
1776
1777                 return implode( ' ', $opts );
1778         }
1779
1780         /**
1781          * UPDATE wrapper. Takes a condition array and a SET array.
1782          *
1783          * @param $table  String name of the table to UPDATE. This will be passed through
1784          *                DatabaseBase::tableName().
1785          *
1786          * @param $values Array:  An array of values to SET. For each array element,
1787          *                the key gives the field name, and the value gives the data
1788          *                to set that field to. The data will be quoted by
1789          *                DatabaseBase::addQuotes().
1790          *
1791          * @param $conds  Array:  An array of conditions (WHERE). See
1792          *                DatabaseBase::select() for the details of the format of
1793          *                condition arrays. Use '*' to update all rows.
1794          *
1795          * @param $fname  String: The function name of the caller (from __METHOD__),
1796          *                for logging and profiling.
1797          *
1798          * @param $options Array: An array of UPDATE options, can be:
1799          *                   - IGNORE: Ignore unique key conflicts
1800          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1801          * @return Boolean
1802          */
1803         function update( $table, $values, $conds, $fname = 'DatabaseBase::update', $options = array() ) {
1804                 $table = $this->tableName( $table );
1805                 $opts = $this->makeUpdateOptions( $options );
1806                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1807
1808                 if ( $conds !== array() && $conds !== '*' ) {
1809                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1810                 }
1811
1812                 return $this->query( $sql, $fname );
1813         }
1814
1815         /**
1816          * Makes an encoded list of strings from an array
1817          * @param $a Array containing the data
1818          * @param int $mode Constant
1819          *      - LIST_COMMA:          comma separated, no field names
1820          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1821          *        the documentation for $conds in DatabaseBase::select().
1822          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1823          *      - LIST_SET:            comma separated with field names, like a SET clause
1824          *      - LIST_NAMES:          comma separated field names
1825          *
1826          * @throws MWException|DBUnexpectedError
1827          * @return string
1828          */
1829         public function makeList( $a, $mode = LIST_COMMA ) {
1830                 if ( !is_array( $a ) ) {
1831                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1832                 }
1833
1834                 $first = true;
1835                 $list = '';
1836
1837                 foreach ( $a as $field => $value ) {
1838                         if ( !$first ) {
1839                                 if ( $mode == LIST_AND ) {
1840                                         $list .= ' AND ';
1841                                 } elseif ( $mode == LIST_OR ) {
1842                                         $list .= ' OR ';
1843                                 } else {
1844                                         $list .= ',';
1845                                 }
1846                         } else {
1847                                 $first = false;
1848                         }
1849
1850                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1851                                 $list .= "($value)";
1852                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1853                                 $list .= "$value";
1854                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1855                                 if ( count( $value ) == 0 ) {
1856                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1857                                 } elseif ( count( $value ) == 1 ) {
1858                                         // Special-case single values, as IN isn't terribly efficient
1859                                         // Don't necessarily assume the single key is 0; we don't
1860                                         // enforce linear numeric ordering on other arrays here.
1861                                         $value = array_values( $value );
1862                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1863                                 } else {
1864                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1865                                 }
1866                         } elseif ( $value === null ) {
1867                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1868                                         $list .= "$field IS ";
1869                                 } elseif ( $mode == LIST_SET ) {
1870                                         $list .= "$field = ";
1871                                 }
1872                                 $list .= 'NULL';
1873                         } else {
1874                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1875                                         $list .= "$field = ";
1876                                 }
1877                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1878                         }
1879                 }
1880
1881                 return $list;
1882         }
1883
1884         /**
1885          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1886          * The keys on each level may be either integers or strings.
1887          *
1888          * @param $data Array: organized as 2-d
1889          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
1890          * @param $baseKey String: field name to match the base-level keys to (eg 'pl_namespace')
1891          * @param $subKey String: field name to match the sub-level keys to (eg 'pl_title')
1892          * @return Mixed: string SQL fragment, or false if no items in array.
1893          */
1894         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1895                 $conds = array();
1896
1897                 foreach ( $data as $base => $sub ) {
1898                         if ( count( $sub ) ) {
1899                                 $conds[] = $this->makeList(
1900                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1901                                         LIST_AND );
1902                         }
1903                 }
1904
1905                 if ( $conds ) {
1906                         return $this->makeList( $conds, LIST_OR );
1907                 } else {
1908                         // Nothing to search for...
1909                         return false;
1910                 }
1911         }
1912
1913         /**
1914          * Return aggregated value alias
1915          *
1916          * @param $valuedata
1917          * @param $valuename string
1918          *
1919          * @return string
1920          */
1921         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1922                 return $valuename;
1923         }
1924
1925         /**
1926          * @param $field
1927          * @return string
1928          */
1929         public function bitNot( $field ) {
1930                 return "(~$field)";
1931         }
1932
1933         /**
1934          * @param $fieldLeft
1935          * @param $fieldRight
1936          * @return string
1937          */
1938         public function bitAnd( $fieldLeft, $fieldRight ) {
1939                 return "($fieldLeft & $fieldRight)";
1940         }
1941
1942         /**
1943          * @param  $fieldLeft
1944          * @param  $fieldRight
1945          * @return string
1946          */
1947         public function bitOr( $fieldLeft, $fieldRight ) {
1948                 return "($fieldLeft | $fieldRight)";
1949         }
1950
1951         /**
1952          * Build a concatenation list to feed into a SQL query
1953          * @param $stringList Array: list of raw SQL expressions; caller is responsible for any quoting
1954          * @return String
1955          */
1956         public function buildConcat( $stringList ) {
1957                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1958         }
1959
1960         /**
1961          * Change the current database
1962          *
1963          * @todo Explain what exactly will fail if this is not overridden.
1964          *
1965          * @param $db
1966          *
1967          * @return bool Success or failure
1968          */
1969         public function selectDB( $db ) {
1970                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
1971                 # if your database engine supports a concept similar to MySQL's
1972                 # databases you may as well.
1973                 $this->mDBname = $db;
1974                 return true;
1975         }
1976
1977         /**
1978          * Get the current DB name
1979          */
1980         public function getDBname() {
1981                 return $this->mDBname;
1982         }
1983
1984         /**
1985          * Get the server hostname or IP address
1986          */
1987         public function getServer() {
1988                 return $this->mServer;
1989         }
1990
1991         /**
1992          * Format a table name ready for use in constructing an SQL query
1993          *
1994          * This does two important things: it quotes the table names to clean them up,
1995          * and it adds a table prefix if only given a table name with no quotes.
1996          *
1997          * All functions of this object which require a table name call this function
1998          * themselves. Pass the canonical name to such functions. This is only needed
1999          * when calling query() directly.
2000          *
2001          * @param $name String: database table name
2002          * @param $format String One of:
2003          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2004          *            so that it can be used in a query.
2005          *   raw - Do not add identifier quotes to the table name
2006          * @return String: full database name
2007          */
2008         public function tableName( $name, $format = 'quoted' ) {
2009                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
2010                 # Skip the entire process when we have a string quoted on both ends.
2011                 # Note that we check the end so that we will still quote any use of
2012                 # use of `database`.table. But won't break things if someone wants
2013                 # to query a database table with a dot in the name.
2014                 if ( $this->isQuotedIdentifier( $name ) ) {
2015                         return $name;
2016                 }
2017
2018                 # Lets test for any bits of text that should never show up in a table
2019                 # name. Basically anything like JOIN or ON which are actually part of
2020                 # SQL queries, but may end up inside of the table value to combine
2021                 # sql. Such as how the API is doing.
2022                 # Note that we use a whitespace test rather than a \b test to avoid
2023                 # any remote case where a word like on may be inside of a table name
2024                 # surrounded by symbols which may be considered word breaks.
2025                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2026                         return $name;
2027                 }
2028
2029                 # Split database and table into proper variables.
2030                 # We reverse the explode so that database.table and table both output
2031                 # the correct table.
2032                 $dbDetails = array_reverse( explode( '.', $name, 2 ) );
2033                 if ( isset( $dbDetails[1] ) ) {
2034                         list( $table, $database ) = $dbDetails;
2035                 } else {
2036                         list( $table ) = $dbDetails;
2037                 }
2038                 $prefix = $this->mTablePrefix; # Default prefix
2039
2040                 # A database name has been specified in input. We don't want any
2041                 # prefixes added.
2042                 if ( isset( $database ) ) {
2043                         $prefix = '';
2044                 }
2045
2046                 # Note that we use the long format because php will complain in in_array if
2047                 # the input is not an array, and will complain in is_array if it is not set.
2048                 if ( !isset( $database ) # Don't use shared database if pre selected.
2049                  && isset( $wgSharedDB ) # We have a shared database
2050                  && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
2051                  && isset( $wgSharedTables )
2052                  && is_array( $wgSharedTables )
2053                  && in_array( $table, $wgSharedTables ) ) { # A shared table is selected
2054                         $database = $wgSharedDB;
2055                         $prefix   = isset( $wgSharedPrefix ) ? $wgSharedPrefix : $prefix;
2056                 }
2057
2058                 # Quote the $database and $table and apply the prefix if not quoted.
2059                 if ( isset( $database ) ) {
2060                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2061                                 $database = $this->addIdentifierQuotes( $database );
2062                         }
2063                 }
2064
2065                 $table = "{$prefix}{$table}";
2066                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $table ) ) {
2067                         $table = $this->addIdentifierQuotes( "{$table}" );
2068                 }
2069
2070                 # Merge our database and table into our final table name.
2071                 $tableName = ( isset( $database ) ? "{$database}.{$table}" : "{$table}" );
2072
2073                 return $tableName;
2074         }
2075
2076         /**
2077          * Fetch a number of table names into an array
2078          * This is handy when you need to construct SQL for joins
2079          *
2080          * Example:
2081          * extract($dbr->tableNames('user','watchlist'));
2082          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2083          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2084          *
2085          * @return array
2086          */
2087         public function tableNames() {
2088                 $inArray = func_get_args();
2089                 $retVal = array();
2090
2091                 foreach ( $inArray as $name ) {
2092                         $retVal[$name] = $this->tableName( $name );
2093                 }
2094
2095                 return $retVal;
2096         }
2097
2098         /**
2099          * Fetch a number of table names into an zero-indexed numerical array
2100          * This is handy when you need to construct SQL for joins
2101          *
2102          * Example:
2103          * list( $user, $watchlist ) = $dbr->tableNamesN('user','watchlist');
2104          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2105          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2106          *
2107          * @return array
2108          */
2109         public function tableNamesN() {
2110                 $inArray = func_get_args();
2111                 $retVal = array();
2112
2113                 foreach ( $inArray as $name ) {
2114                         $retVal[] = $this->tableName( $name );
2115                 }
2116
2117                 return $retVal;
2118         }
2119
2120         /**
2121          * Get an aliased table name
2122          * e.g. tableName AS newTableName
2123          *
2124          * @param $name string Table name, see tableName()
2125          * @param $alias string|bool Alias (optional)
2126          * @return string SQL name for aliased table. Will not alias a table to its own name
2127          */
2128         public function tableNameWithAlias( $name, $alias = false ) {
2129                 if ( !$alias || $alias == $name ) {
2130                         return $this->tableName( $name );
2131                 } else {
2132                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2133                 }
2134         }
2135
2136         /**
2137          * Gets an array of aliased table names
2138          *
2139          * @param $tables array( [alias] => table )
2140          * @return array of strings, see tableNameWithAlias()
2141          */
2142         public function tableNamesWithAlias( $tables ) {
2143                 $retval = array();
2144                 foreach ( $tables as $alias => $table ) {
2145                         if ( is_numeric( $alias ) ) {
2146                                 $alias = $table;
2147                         }
2148                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2149                 }
2150                 return $retval;
2151         }
2152
2153         /**
2154          * Get an aliased field name
2155          * e.g. fieldName AS newFieldName
2156          *
2157          * @param $name string Field name
2158          * @param $alias string|bool Alias (optional)
2159          * @return string SQL name for aliased field. Will not alias a field to its own name
2160          */
2161         public function fieldNameWithAlias( $name, $alias = false ) {
2162                 if ( !$alias || (string)$alias === (string)$name ) {
2163                         return $name;
2164                 } else {
2165                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2166                 }
2167         }
2168
2169         /**
2170          * Gets an array of aliased field names
2171          *
2172          * @param $fields array( [alias] => field )
2173          * @return array of strings, see fieldNameWithAlias()
2174          */
2175         public function fieldNamesWithAlias( $fields ) {
2176                 $retval = array();
2177                 foreach ( $fields as $alias => $field ) {
2178                         if ( is_numeric( $alias ) ) {
2179                                 $alias = $field;
2180                         }
2181                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2182                 }
2183                 return $retval;
2184         }
2185
2186         /**
2187          * Get the aliased table name clause for a FROM clause
2188          * which might have a JOIN and/or USE INDEX clause
2189          *
2190          * @param $tables array ( [alias] => table )
2191          * @param $use_index array Same as for select()
2192          * @param $join_conds array Same as for select()
2193          * @return string
2194          */
2195         protected function tableNamesWithUseIndexOrJOIN(
2196                 $tables, $use_index = array(), $join_conds = array()
2197         ) {
2198                 $ret = array();
2199                 $retJOIN = array();
2200                 $use_index = (array)$use_index;
2201                 $join_conds = (array)$join_conds;
2202
2203                 foreach ( $tables as $alias => $table ) {
2204                         if ( !is_string( $alias ) ) {
2205                                 // No alias? Set it equal to the table name
2206                                 $alias = $table;
2207                         }
2208                         // Is there a JOIN clause for this table?
2209                         if ( isset( $join_conds[$alias] ) ) {
2210                                 list( $joinType, $conds ) = $join_conds[$alias];
2211                                 $tableClause = $joinType;
2212                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2213                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2214                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2215                                         if ( $use != '' ) {
2216                                                 $tableClause .= ' ' . $use;
2217                                         }
2218                                 }
2219                                 $on = $this->makeList( (array)$conds, LIST_AND );
2220                                 if ( $on != '' ) {
2221                                         $tableClause .= ' ON (' . $on . ')';
2222                                 }
2223
2224                                 $retJOIN[] = $tableClause;
2225                         // Is there an INDEX clause for this table?
2226                         } elseif ( isset( $use_index[$alias] ) ) {
2227                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2228                                 $tableClause .= ' ' . $this->useIndexClause(
2229                                         implode( ',', (array)$use_index[$alias] ) );
2230
2231                                 $ret[] = $tableClause;
2232                         } else {
2233                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2234
2235                                 $ret[] = $tableClause;
2236                         }
2237                 }
2238
2239                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2240                 $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2241                 $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2242
2243                 // Compile our final table clause
2244                 return implode( ' ', array( $straightJoins, $otherJoins ) );
2245         }
2246
2247         /**
2248          * Get the name of an index in a given table
2249          *
2250          * @param $index
2251          *
2252          * @return string
2253          */
2254         protected function indexName( $index ) {
2255                 // Backwards-compatibility hack
2256                 $renamed = array(
2257                         'ar_usertext_timestamp' => 'usertext_timestamp',
2258                         'un_user_id'            => 'user_id',
2259                         'un_user_ip'            => 'user_ip',
2260                 );
2261
2262                 if ( isset( $renamed[$index] ) ) {
2263                         return $renamed[$index];
2264                 } else {
2265                         return $index;
2266                 }
2267         }
2268
2269         /**
2270          * If it's a string, adds quotes and backslashes
2271          * Otherwise returns as-is
2272          *
2273          * @param $s string
2274          *
2275          * @return string
2276          */
2277         public function addQuotes( $s ) {
2278                 if ( $s === null ) {
2279                         return 'NULL';
2280                 } else {
2281                         # This will also quote numeric values. This should be harmless,
2282                         # and protects against weird problems that occur when they really
2283                         # _are_ strings such as article titles and string->number->string
2284                         # conversion is not 1:1.
2285                         return "'" . $this->strencode( $s ) . "'";
2286                 }
2287         }
2288
2289         /**
2290          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2291          * MySQL uses `backticks` while basically everything else uses double quotes.
2292          * Since MySQL is the odd one out here the double quotes are our generic
2293          * and we implement backticks in DatabaseMysql.
2294          *
2295          * @param $s string
2296          *
2297          * @return string
2298          */
2299         public function addIdentifierQuotes( $s ) {
2300                 return '"' . str_replace( '"', '""', $s ) . '"';
2301         }
2302
2303         /**
2304          * Returns if the given identifier looks quoted or not according to
2305          * the database convention for quoting identifiers .
2306          *
2307          * @param $name string
2308          *
2309          * @return boolean
2310          */
2311         public function isQuotedIdentifier( $name ) {
2312                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2313         }
2314
2315         /**
2316          * @param $s string
2317          * @return string
2318          */
2319         protected function escapeLikeInternal( $s ) {
2320                 $s = str_replace( '\\', '\\\\', $s );
2321                 $s = $this->strencode( $s );
2322                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2323
2324                 return $s;
2325         }
2326
2327         /**
2328          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2329          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2330          * Alternatively, the function could be provided with an array of aforementioned parameters.
2331          *
2332          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2333          * for subpages of 'My page title'.
2334          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2335          *
2336          * @since 1.16
2337          * @return String: fully built LIKE statement
2338          */
2339         public function buildLike() {
2340                 $params = func_get_args();
2341
2342                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2343                         $params = $params[0];
2344                 }
2345
2346                 $s = '';
2347
2348                 foreach ( $params as $value ) {
2349                         if ( $value instanceof LikeMatch ) {
2350                                 $s .= $value->toString();
2351                         } else {
2352                                 $s .= $this->escapeLikeInternal( $value );
2353                         }
2354                 }
2355
2356                 return " LIKE '" . $s . "' ";
2357         }
2358
2359         /**
2360          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2361          *
2362          * @return LikeMatch
2363          */
2364         public function anyChar() {
2365                 return new LikeMatch( '_' );
2366         }
2367
2368         /**
2369          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2370          *
2371          * @return LikeMatch
2372          */
2373         public function anyString() {
2374                 return new LikeMatch( '%' );
2375         }
2376
2377         /**
2378          * Returns an appropriately quoted sequence value for inserting a new row.
2379          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2380          * subclass will return an integer, and save the value for insertId()
2381          *
2382          * Any implementation of this function should *not* involve reusing
2383          * sequence numbers created for rolled-back transactions.
2384          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2385          * @param $seqName string
2386          * @return null
2387          */
2388         public function nextSequenceValue( $seqName ) {
2389                 return null;
2390         }
2391
2392         /**
2393          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2394          * is only needed because a) MySQL must be as efficient as possible due to
2395          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2396          * which index to pick.  Anyway, other databases might have different
2397          * indexes on a given table.  So don't bother overriding this unless you're
2398          * MySQL.
2399          * @param $index
2400          * @return string
2401          */
2402         public function useIndexClause( $index ) {
2403                 return '';
2404         }
2405
2406         /**
2407          * REPLACE query wrapper.
2408          *
2409          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2410          * except that when there is a duplicate key error, the old row is deleted
2411          * and the new row is inserted in its place.
2412          *
2413          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2414          * perform the delete, we need to know what the unique indexes are so that
2415          * we know how to find the conflicting rows.
2416          *
2417          * It may be more efficient to leave off unique indexes which are unlikely
2418          * to collide. However if you do this, you run the risk of encountering
2419          * errors which wouldn't have occurred in MySQL.
2420          *
2421          * @param $table String: The table to replace the row(s) in.
2422          * @param $rows array Can be either a single row to insert, or multiple rows,
2423          *    in the same format as for DatabaseBase::insert()
2424          * @param $uniqueIndexes array is an array of indexes. Each element may be either
2425          *    a field name or an array of field names
2426          * @param $fname String: Calling function name (use __METHOD__) for logs/profiling
2427          */
2428         public function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseBase::replace' ) {
2429                 $quotedTable = $this->tableName( $table );
2430
2431                 if ( count( $rows ) == 0 ) {
2432                         return;
2433                 }
2434
2435                 # Single row case
2436                 if ( !is_array( reset( $rows ) ) ) {
2437                         $rows = array( $rows );
2438                 }
2439
2440                 foreach( $rows as $row ) {
2441                         # Delete rows which collide
2442                         if ( $uniqueIndexes ) {
2443                                 $sql = "DELETE FROM $quotedTable WHERE ";
2444                                 $first = true;
2445                                 foreach ( $uniqueIndexes as $index ) {
2446                                         if ( $first ) {
2447                                                 $first = false;
2448                                                 $sql .= '( ';
2449                                         } else {
2450                                                 $sql .= ' ) OR ( ';
2451                                         }
2452                                         if ( is_array( $index ) ) {
2453                                                 $first2 = true;
2454                                                 foreach ( $index as $col ) {
2455                                                         if ( $first2 ) {
2456                                                                 $first2 = false;
2457                                                         } else {
2458                                                                 $sql .= ' AND ';
2459                                                         }
2460                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2461                                                 }
2462                                         } else {
2463                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2464                                         }
2465                                 }
2466                                 $sql .= ' )';
2467                                 $this->query( $sql, $fname );
2468                         }
2469
2470                         # Now insert the row
2471                         $this->insert( $table, $row );
2472                 }
2473         }
2474
2475         /**
2476          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2477          * statement.
2478          *
2479          * @param $table string Table name
2480          * @param $rows array Rows to insert
2481          * @param $fname string Caller function name
2482          *
2483          * @return ResultWrapper
2484          */
2485         protected function nativeReplace( $table, $rows, $fname ) {
2486                 $table = $this->tableName( $table );
2487
2488                 # Single row case
2489                 if ( !is_array( reset( $rows ) ) ) {
2490                         $rows = array( $rows );
2491                 }
2492
2493                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2494                 $first = true;
2495
2496                 foreach ( $rows as $row ) {
2497                         if ( $first ) {
2498                                 $first = false;
2499                         } else {
2500                                 $sql .= ',';
2501                         }
2502
2503                         $sql .= '(' . $this->makeList( $row ) . ')';
2504                 }
2505
2506                 return $this->query( $sql, $fname );
2507         }
2508
2509         /**
2510          * DELETE where the condition is a join.
2511          *
2512          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2513          * we use sub-selects
2514          *
2515          * For safety, an empty $conds will not delete everything. If you want to
2516          * delete all rows where the join condition matches, set $conds='*'.
2517          *
2518          * DO NOT put the join condition in $conds.
2519          *
2520          * @param $delTable   String: The table to delete from.
2521          * @param $joinTable  String: The other table.
2522          * @param $delVar     String: The variable to join on, in the first table.
2523          * @param $joinVar    String: The variable to join on, in the second table.
2524          * @param $conds      Array: Condition array of field names mapped to variables,
2525          *                    ANDed together in the WHERE clause
2526          * @param $fname      String: Calling function name (use __METHOD__) for
2527          *                    logs/profiling
2528          * @throws DBUnexpectedError
2529          */
2530         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2531                 $fname = 'DatabaseBase::deleteJoin' )
2532         {
2533                 if ( !$conds ) {
2534                         throw new DBUnexpectedError( $this,
2535                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2536                 }
2537
2538                 $delTable = $this->tableName( $delTable );
2539                 $joinTable = $this->tableName( $joinTable );
2540                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2541                 if ( $conds != '*' ) {
2542                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2543                 }
2544                 $sql .= ')';
2545
2546                 $this->query( $sql, $fname );
2547         }
2548
2549         /**
2550          * Returns the size of a text field, or -1 for "unlimited"
2551          *
2552          * @param $table string
2553          * @param $field string
2554          *
2555          * @return int
2556          */
2557         public function textFieldSize( $table, $field ) {
2558                 $table = $this->tableName( $table );
2559                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2560                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2561                 $row = $this->fetchObject( $res );
2562
2563                 $m = array();
2564
2565                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2566                         $size = $m[1];
2567                 } else {
2568                         $size = -1;
2569                 }
2570
2571                 return $size;
2572         }
2573
2574         /**
2575          * A string to insert into queries to show that they're low-priority, like
2576          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2577          * string and nothing bad should happen.
2578          *
2579          * @return string Returns the text of the low priority option if it is
2580          *   supported, or a blank string otherwise
2581          */
2582         public function lowPriorityOption() {
2583                 return '';
2584         }
2585
2586         /**
2587          * DELETE query wrapper.
2588          *
2589          * @param $table Array Table name
2590          * @param $conds String|Array of conditions. See $conds in DatabaseBase::select() for
2591          *               the format. Use $conds == "*" to delete all rows
2592          * @param $fname String name of the calling function
2593          *
2594          * @throws DBUnexpectedError
2595          * @return bool
2596          */
2597         public function delete( $table, $conds, $fname = 'DatabaseBase::delete' ) {
2598                 if ( !$conds ) {
2599                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2600                 }
2601
2602                 $table = $this->tableName( $table );
2603                 $sql = "DELETE FROM $table";
2604
2605                 if ( $conds != '*' ) {
2606                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2607                 }
2608
2609                 return $this->query( $sql, $fname );
2610         }
2611
2612         /**
2613          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2614          * into another table.
2615          *
2616          * @param $destTable string The table name to insert into
2617          * @param $srcTable string|array May be either a table name, or an array of table names
2618          *    to include in a join.
2619          *
2620          * @param $varMap array must be an associative array of the form
2621          *    array( 'dest1' => 'source1', ...). Source items may be literals
2622          *    rather than field names, but strings should be quoted with
2623          *    DatabaseBase::addQuotes()
2624          *
2625          * @param $conds array Condition array. See $conds in DatabaseBase::select() for
2626          *    the details of the format of condition arrays. May be "*" to copy the
2627          *    whole table.
2628          *
2629          * @param $fname string The function name of the caller, from __METHOD__
2630          *
2631          * @param $insertOptions array Options for the INSERT part of the query, see
2632          *    DatabaseBase::insert() for details.
2633          * @param $selectOptions array Options for the SELECT part of the query, see
2634          *    DatabaseBase::select() for details.
2635          *
2636          * @return ResultWrapper
2637          */
2638         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2639                 $fname = 'DatabaseBase::insertSelect',
2640                 $insertOptions = array(), $selectOptions = array() )
2641         {
2642                 $destTable = $this->tableName( $destTable );
2643
2644                 if ( is_array( $insertOptions ) ) {
2645                         $insertOptions = implode( ' ', $insertOptions );
2646                 }
2647
2648                 if ( !is_array( $selectOptions ) ) {
2649                         $selectOptions = array( $selectOptions );
2650                 }
2651
2652                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2653
2654                 if ( is_array( $srcTable ) ) {
2655                         $srcTable =  implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2656                 } else {
2657                         $srcTable = $this->tableName( $srcTable );
2658                 }
2659
2660                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2661                         " SELECT $startOpts " . implode( ',', $varMap ) .
2662                         " FROM $srcTable $useIndex ";
2663
2664                 if ( $conds != '*' ) {
2665                         if ( is_array( $conds ) ) {
2666                                 $conds = $this->makeList( $conds, LIST_AND );
2667                         }
2668                         $sql .= " WHERE $conds";
2669                 }
2670
2671                 $sql .= " $tailOpts";
2672
2673                 return $this->query( $sql, $fname );
2674         }
2675
2676         /**
2677          * Construct a LIMIT query with optional offset.  This is used for query
2678          * pages.  The SQL should be adjusted so that only the first $limit rows
2679          * are returned.  If $offset is provided as well, then the first $offset
2680          * rows should be discarded, and the next $limit rows should be returned.
2681          * If the result of the query is not ordered, then the rows to be returned
2682          * are theoretically arbitrary.
2683          *
2684          * $sql is expected to be a SELECT, if that makes a difference.
2685          *
2686          * The version provided by default works in MySQL and SQLite.  It will very
2687          * likely need to be overridden for most other DBMSes.
2688          *
2689          * @param $sql String SQL query we will append the limit too
2690          * @param $limit Integer the SQL limit
2691          * @param $offset Integer|bool the SQL offset (default false)
2692          *
2693          * @throws DBUnexpectedError
2694          * @return string
2695          */
2696         public function limitResult( $sql, $limit, $offset = false ) {
2697                 if ( !is_numeric( $limit ) ) {
2698                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2699                 }
2700                 return "$sql LIMIT "
2701                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2702                         . "{$limit} ";
2703         }
2704
2705         /**
2706          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2707          * within the UNION construct.
2708          * @return Boolean
2709          */
2710         public function unionSupportsOrderAndLimit() {
2711                 return true; // True for almost every DB supported
2712         }
2713
2714         /**
2715          * Construct a UNION query
2716          * This is used for providing overload point for other DB abstractions
2717          * not compatible with the MySQL syntax.
2718          * @param $sqls Array: SQL statements to combine
2719          * @param $all Boolean: use UNION ALL
2720          * @return String: SQL fragment
2721          */
2722         public function unionQueries( $sqls, $all ) {
2723                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2724                 return '(' . implode( $glue, $sqls ) . ')';
2725         }
2726
2727         /**
2728          * Returns an SQL expression for a simple conditional.  This doesn't need
2729          * to be overridden unless CASE isn't supported in your DBMS.
2730          *
2731          * @param $cond string|array SQL expression which will result in a boolean value
2732          * @param $trueVal String: SQL expression to return if true
2733          * @param $falseVal String: SQL expression to return if false
2734          * @return String: SQL fragment
2735          */
2736         public function conditional( $cond, $trueVal, $falseVal ) {
2737                 if ( is_array( $cond ) ) {
2738                         $cond = $this->makeList( $cond, LIST_AND );
2739                 }
2740                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2741         }
2742
2743         /**
2744          * Returns a comand for str_replace function in SQL query.
2745          * Uses REPLACE() in MySQL
2746          *
2747          * @param $orig String: column to modify
2748          * @param $old String: column to seek
2749          * @param $new String: column to replace with
2750          *
2751          * @return string
2752          */
2753         public function strreplace( $orig, $old, $new ) {
2754                 return "REPLACE({$orig}, {$old}, {$new})";
2755         }
2756
2757         /**
2758          * Determines how long the server has been up
2759          * STUB
2760          *
2761          * @return int
2762          */
2763         public function getServerUptime() {
2764                 return 0;
2765         }
2766
2767         /**
2768          * Determines if the last failure was due to a deadlock
2769          * STUB
2770          *
2771          * @return bool
2772          */
2773         public function wasDeadlock() {
2774                 return false;
2775         }
2776
2777         /**
2778          * Determines if the last failure was due to a lock timeout
2779          * STUB
2780          *
2781          * @return bool
2782          */
2783         public function wasLockTimeout() {
2784                 return false;
2785         }
2786
2787         /**
2788          * Determines if the last query error was something that should be dealt
2789          * with by pinging the connection and reissuing the query.
2790          * STUB
2791          *
2792          * @return bool
2793          */
2794         public function wasErrorReissuable() {
2795                 return false;
2796         }
2797
2798         /**
2799          * Determines if the last failure was due to the database being read-only.
2800          * STUB
2801          *
2802          * @return bool
2803          */
2804         public function wasReadOnlyError() {
2805                 return false;
2806         }
2807
2808         /**
2809          * Perform a deadlock-prone transaction.
2810          *
2811          * This function invokes a callback function to perform a set of write
2812          * queries. If a deadlock occurs during the processing, the transaction
2813          * will be rolled back and the callback function will be called again.
2814          *
2815          * Usage:
2816          *   $dbw->deadlockLoop( callback, ... );
2817          *
2818          * Extra arguments are passed through to the specified callback function.
2819          *
2820          * Returns whatever the callback function returned on its successful,
2821          * iteration, or false on error, for example if the retry limit was
2822          * reached.
2823          *
2824          * @return bool
2825          */
2826         public function deadlockLoop() {
2827                 $this->begin( __METHOD__ );
2828                 $args = func_get_args();
2829                 $function = array_shift( $args );
2830                 $oldIgnore = $this->ignoreErrors( true );
2831                 $tries = DEADLOCK_TRIES;
2832
2833                 if ( is_array( $function ) ) {
2834                         $fname = $function[0];
2835                 } else {
2836                         $fname = $function;
2837                 }
2838
2839                 do {
2840                         $retVal = call_user_func_array( $function, $args );
2841                         $error = $this->lastError();
2842                         $errno = $this->lastErrno();
2843                         $sql = $this->lastQuery();
2844
2845                         if ( $errno ) {
2846                                 if ( $this->wasDeadlock() ) {
2847                                         # Retry
2848                                         usleep( mt_rand( DEADLOCK_DELAY_MIN, DEADLOCK_DELAY_MAX ) );
2849                                 } else {
2850                                         $this->reportQueryError( $error, $errno, $sql, $fname );
2851                                 }
2852                         }
2853                 } while ( $this->wasDeadlock() && --$tries > 0 );
2854
2855                 $this->ignoreErrors( $oldIgnore );
2856
2857                 if ( $tries <= 0 ) {
2858                         $this->rollback( __METHOD__ );
2859                         $this->reportQueryError( $error, $errno, $sql, $fname );
2860                         return false;
2861                 } else {
2862                         $this->commit( __METHOD__ );
2863                         return $retVal;
2864                 }
2865         }
2866
2867         /**
2868          * Wait for the slave to catch up to a given master position.
2869          *
2870          * @param $pos DBMasterPos object
2871          * @param $timeout Integer: the maximum number of seconds to wait for
2872          *   synchronisation
2873          *
2874          * @return integer: zero if the slave was past that position already,
2875          *   greater than zero if we waited for some period of time, less than
2876          *   zero if we timed out.
2877          */
2878         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2879                 wfProfileIn( __METHOD__ );
2880
2881                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2882                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
2883
2884                         if ( $wait > $timeout * 1e6 ) {
2885                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
2886                                 wfProfileOut( __METHOD__ );
2887                                 return -1;
2888                         } elseif ( $wait > 0 ) {
2889                                 wfDebug( "Fake slave waiting $wait us\n" );
2890                                 usleep( $wait );
2891                                 wfProfileOut( __METHOD__ );
2892                                 return 1;
2893                         } else {
2894                                 wfDebug( "Fake slave up to date ($wait us)\n" );
2895                                 wfProfileOut( __METHOD__ );
2896                                 return 0;
2897                         }
2898                 }
2899
2900                 wfProfileOut( __METHOD__ );
2901
2902                 # Real waits are implemented in the subclass.
2903                 return 0;
2904         }
2905
2906         /**
2907          * Get the replication position of this slave
2908          *
2909          * @return DBMasterPos, or false if this is not a slave.
2910          */
2911         public function getSlavePos() {
2912                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2913                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
2914                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
2915                         return $pos;
2916                 } else {
2917                         # Stub
2918                         return false;
2919                 }
2920         }
2921
2922         /**
2923          * Get the position of this master
2924          *
2925          * @return DBMasterPos, or false if this is not a master
2926          */
2927         public function getMasterPos() {
2928                 if ( $this->mFakeMaster ) {
2929                         return new MySQLMasterPos( 'fake', microtime( true ) );
2930                 } else {
2931                         return false;
2932                 }
2933         }
2934
2935         /**
2936          * Run an anonymous function as soon as there is no transaction pending.
2937          * If there is a transaction and it is rolled back, then the callback is cancelled.
2938          * Callbacks must commit any transactions that they begin.
2939          *
2940          * This is useful for updates to different systems or separate transactions are needed.
2941          *
2942          * @since 1.20
2943          *
2944          * @param Closure $callback
2945          */
2946         final public function onTransactionIdle( Closure $callback ) {
2947                 if ( $this->mTrxLevel ) {
2948                         $this->mTrxIdleCallbacks[] = $callback;
2949                 } else {
2950                         $callback();
2951                 }
2952         }
2953
2954         /**
2955          * Actually run the "on transaction idle" callbacks.
2956          *
2957          * @since 1.20
2958          */
2959         protected function runOnTransactionIdleCallbacks() {
2960                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
2961
2962                 $e = null; // last exception
2963                 do { // callbacks may add callbacks :)
2964                         $callbacks = $this->mTrxIdleCallbacks;
2965                         $this->mTrxIdleCallbacks = array(); // recursion guard
2966                         foreach ( $callbacks as $callback ) {
2967                                 try {
2968                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
2969                                         $callback();
2970                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
2971                                 } catch ( Exception $e ) {}
2972                         }
2973                 } while ( count( $this->mTrxIdleCallbacks ) );
2974
2975                 if ( $e instanceof Exception ) {
2976                         throw $e; // re-throw any last exception
2977                 }
2978         }
2979
2980         /**
2981          * Begin a transaction. If a transaction is already in progress, that transaction will be committed before the
2982          * new transaction is started.
2983          *
2984          * Note that when the DBO_TRX flag is set (which is usually the case for web requests, but not for maintenance scripts),
2985          * any previous database query will have started a transaction automatically.
2986          *
2987          * Nesting of transactions is not supported. Attempts to nest transactions will cause a warning, unless the current
2988          * transaction was started automatically because of the DBO_TRX flag.
2989          *
2990          * @param $fname string
2991          */
2992         final public function begin( $fname = 'DatabaseBase::begin' ) {
2993                 global $wgDebugDBTransactions;
2994
2995                 if ( $this->mTrxLevel ) { // implicit commit
2996                         if ( !$this->mTrxAutomatic ) {
2997                                 // We want to warn about inadvertently nested begin/commit pairs, but not about auto-committing
2998                                 // implicit transactions that were started by query() because DBO_TRX was set.
2999
3000                                 wfWarn( "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3001                                         " performing implicit commit!" );
3002                         } else {
3003                                 // if the transaction was automatic and has done write operations,
3004                                 // log it if $wgDebugDBTransactions is enabled.
3005
3006                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3007                                         wfDebug( "$fname: Automatic transaction with writes in progress (from {$this->mTrxFname}), " .
3008                                                 " performing implicit commit!\n" );
3009                                 }
3010                         }
3011
3012                         $this->doCommit( $fname );
3013                         $this->runOnTransactionIdleCallbacks();
3014                 }
3015
3016                 $this->doBegin( $fname );
3017                 $this->mTrxFname = $fname;
3018                 $this->mTrxDoneWrites = false;
3019                 $this->mTrxAutomatic = false;
3020         }
3021
3022         /**
3023          * Issues the BEGIN command to the database server.
3024          *
3025          * @see DatabaseBase::begin()
3026          * @param type $fname
3027          */
3028         protected function doBegin( $fname ) {
3029                 $this->query( 'BEGIN', $fname );
3030                 $this->mTrxLevel = 1;
3031         }
3032
3033         /**
3034          * Commits a transaction previously started using begin().
3035          * If no transaction is in progress, a warning is issued.
3036          *
3037          * Nesting of transactions is not supported.
3038          *
3039          * @param $fname string
3040          * @param $flush String Flush flag, set to 'flush' to disable warnings about explicitly committing implicit
3041          *        transactions, or calling commit when no transaction is in progress.
3042          *        This will silently break any ongoing explicit transaction. Only set the flush flag if you are sure
3043          *        that it is safe to ignore these warnings in your context.
3044          */
3045         final public function commit( $fname = 'DatabaseBase::commit', $flush = '' ) {
3046                 if ( $flush != 'flush' ) {
3047                         if ( !$this->mTrxLevel ) {
3048                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3049                         } elseif( $this->mTrxAutomatic ) {
3050                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3051                         }
3052                 } else {
3053                         if ( !$this->mTrxLevel ) {
3054                                 return; // nothing to do
3055                         } elseif( !$this->mTrxAutomatic ) {
3056                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3057                         }
3058                 }
3059
3060                 $this->doCommit( $fname );
3061                 $this->runOnTransactionIdleCallbacks();
3062         }
3063
3064         /**
3065          * Issues the COMMIT command to the database server.
3066          *
3067          * @see DatabaseBase::commit()
3068          * @param type $fname
3069          */
3070         protected function doCommit( $fname ) {
3071                 if ( $this->mTrxLevel ) {
3072                         $this->query( 'COMMIT', $fname );
3073                         $this->mTrxLevel = 0;
3074                 }
3075         }
3076
3077         /**
3078          * Rollback a transaction previously started using begin().
3079          * If no transaction is in progress, a warning is issued.
3080          *
3081          * No-op on non-transactional databases.
3082          *
3083          * @param $fname string
3084          */
3085         final public function rollback( $fname = 'DatabaseBase::rollback' ) {
3086                 if ( !$this->mTrxLevel ) {
3087                         wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3088                 }
3089                 $this->doRollback( $fname );
3090                 $this->mTrxIdleCallbacks = array(); // cancel
3091         }
3092
3093         /**
3094          * Issues the ROLLBACK command to the database server.
3095          *
3096          * @see DatabaseBase::rollback()
3097          * @param type $fname
3098          */
3099         protected function doRollback( $fname ) {
3100                 if ( $this->mTrxLevel ) {
3101                         $this->query( 'ROLLBACK', $fname, true );
3102                         $this->mTrxLevel = 0;
3103                 }
3104         }
3105
3106         /**
3107          * Creates a new table with structure copied from existing table
3108          * Note that unlike most database abstraction functions, this function does not
3109          * automatically append database prefix, because it works at a lower
3110          * abstraction level.
3111          * The table names passed to this function shall not be quoted (this
3112          * function calls addIdentifierQuotes when needed).
3113          *
3114          * @param $oldName String: name of table whose structure should be copied
3115          * @param $newName String: name of table to be created
3116          * @param $temporary Boolean: whether the new table should be temporary
3117          * @param $fname String: calling function name
3118          * @throws MWException
3119          * @return Boolean: true if operation was successful
3120          */
3121         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3122                 $fname = 'DatabaseBase::duplicateTableStructure' )
3123         {
3124                 throw new MWException(
3125                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3126         }
3127
3128         /**
3129          * List all tables on the database
3130          *
3131          * @param $prefix string Only show tables with this prefix, e.g. mw_
3132          * @param $fname String: calling function name
3133          * @throws MWException
3134          */
3135         function listTables( $prefix = null, $fname = 'DatabaseBase::listTables' ) {
3136                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3137         }
3138
3139         /**
3140          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3141          * to the format used for inserting into timestamp fields in this DBMS.
3142          *
3143          * The result is unquoted, and needs to be passed through addQuotes()
3144          * before it can be included in raw SQL.
3145          *
3146          * @param $ts string|int
3147          *
3148          * @return string
3149          */
3150         public function timestamp( $ts = 0 ) {
3151                 return wfTimestamp( TS_MW, $ts );
3152         }
3153
3154         /**
3155          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3156          * to the format used for inserting into timestamp fields in this DBMS. If
3157          * NULL is input, it is passed through, allowing NULL values to be inserted
3158          * into timestamp fields.
3159          *
3160          * The result is unquoted, and needs to be passed through addQuotes()
3161          * before it can be included in raw SQL.
3162          *
3163          * @param $ts string|int
3164          *
3165          * @return string
3166          */
3167         public function timestampOrNull( $ts = null ) {
3168                 if ( is_null( $ts ) ) {
3169                         return null;
3170                 } else {
3171                         return $this->timestamp( $ts );
3172                 }
3173         }
3174
3175         /**
3176          * Take the result from a query, and wrap it in a ResultWrapper if
3177          * necessary. Boolean values are passed through as is, to indicate success
3178          * of write queries or failure.
3179          *
3180          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3181          * resource, and it was necessary to call this function to convert it to
3182          * a wrapper. Nowadays, raw database objects are never exposed to external
3183          * callers, so this is unnecessary in external code. For compatibility with
3184          * old code, ResultWrapper objects are passed through unaltered.
3185          *
3186          * @param $result bool|ResultWrapper
3187          *
3188          * @return bool|ResultWrapper
3189          */
3190         public function resultObject( $result ) {
3191                 if ( empty( $result ) ) {
3192                         return false;
3193                 } elseif ( $result instanceof ResultWrapper ) {
3194                         return $result;
3195                 } elseif ( $result === true ) {
3196                         // Successful write query
3197                         return $result;
3198                 } else {
3199                         return new ResultWrapper( $this, $result );
3200                 }
3201         }
3202
3203         /**
3204          * Ping the server and try to reconnect if it there is no connection
3205          *
3206          * @return bool Success or failure
3207          */
3208         public function ping() {
3209                 # Stub.  Not essential to override.
3210                 return true;
3211         }
3212
3213         /**
3214          * Get slave lag. Currently supported only by MySQL.
3215          *
3216          * Note that this function will generate a fatal error on many
3217          * installations. Most callers should use LoadBalancer::safeGetLag()
3218          * instead.
3219          *
3220          * @return int Database replication lag in seconds
3221          */
3222         public function getLag() {
3223                 return intval( $this->mFakeSlaveLag );
3224         }
3225
3226         /**
3227          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3228          *
3229          * @return int
3230          */
3231         function maxListLen() {
3232                 return 0;
3233         }
3234
3235         /**
3236          * Some DBMSs have a special format for inserting into blob fields, they
3237          * don't allow simple quoted strings to be inserted. To insert into such
3238          * a field, pass the data through this function before passing it to
3239          * DatabaseBase::insert().
3240          * @param $b string
3241          * @return string
3242          */
3243         public function encodeBlob( $b ) {
3244                 return $b;
3245         }
3246
3247         /**
3248          * Some DBMSs return a special placeholder object representing blob fields
3249          * in result objects. Pass the object through this function to return the
3250          * original string.
3251          * @param $b string
3252          * @return string
3253          */
3254         public function decodeBlob( $b ) {
3255                 return $b;
3256         }
3257
3258         /**
3259          * Override database's default behavior. $options include:
3260          *     'connTimeout' : Set the connection timeout value in seconds.
3261          *                     May be useful for very long batch queries such as
3262          *                     full-wiki dumps, where a single query reads out over
3263          *                     hours or days.
3264          *
3265          * @param $options Array
3266          * @return void
3267          */
3268         public function setSessionOptions( array $options ) {}
3269
3270         /**
3271          * Read and execute SQL commands from a file.
3272          *
3273          * Returns true on success, error string or exception on failure (depending
3274          * on object's error ignore settings).
3275          *
3276          * @param $filename String: File name to open
3277          * @param bool|callable $lineCallback Optional function called before reading each line
3278          * @param bool|callable $resultCallback Optional function called for each MySQL result
3279          * @param bool|string $fname Calling function name or false if name should be
3280          *      generated dynamically using $filename
3281          * @param bool|callable $inputCallback Callback: Optional function called for each complete line sent
3282          * @throws MWException
3283          * @return bool|string
3284          */
3285         public function sourceFile(
3286                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3287         ) {
3288                 wfSuppressWarnings();
3289                 $fp = fopen( $filename, 'r' );
3290                 wfRestoreWarnings();
3291
3292                 if ( false === $fp ) {
3293                         throw new MWException( "Could not open \"{$filename}\".\n" );
3294                 }
3295
3296                 if ( !$fname ) {
3297                         $fname = __METHOD__ . "( $filename )";
3298                 }
3299
3300                 try {
3301                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3302                 }
3303                 catch ( MWException $e ) {
3304                         fclose( $fp );
3305                         throw $e;
3306                 }
3307
3308                 fclose( $fp );
3309
3310                 return $error;
3311         }
3312
3313         /**
3314          * Get the full path of a patch file. Originally based on archive()
3315          * from updaters.inc. Keep in mind this always returns a patch, as
3316          * it fails back to MySQL if no DB-specific patch can be found
3317          *
3318          * @param $patch String The name of the patch, like patch-something.sql
3319          * @return String Full path to patch file
3320          */
3321         public function patchPath( $patch ) {
3322                 global $IP;
3323
3324                 $dbType = $this->getType();
3325                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3326                         return "$IP/maintenance/$dbType/archives/$patch";
3327                 } else {
3328                         return "$IP/maintenance/archives/$patch";
3329                 }
3330         }
3331
3332         /**
3333          * Set variables to be used in sourceFile/sourceStream, in preference to the
3334          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3335          * all. If it's set to false, $GLOBALS will be used.
3336          *
3337          * @param $vars bool|array mapping variable name to value.
3338          */
3339         public function setSchemaVars( $vars ) {
3340                 $this->mSchemaVars = $vars;
3341         }
3342
3343         /**
3344          * Read and execute commands from an open file handle.
3345          *
3346          * Returns true on success, error string or exception on failure (depending
3347          * on object's error ignore settings).
3348          *
3349          * @param $fp Resource: File handle
3350          * @param $lineCallback Callback: Optional function called before reading each query
3351          * @param $resultCallback Callback: Optional function called for each MySQL result
3352          * @param $fname String: Calling function name
3353          * @param $inputCallback Callback: Optional function called for each complete query sent
3354          * @return bool|string
3355          */
3356         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3357                 $fname = 'DatabaseBase::sourceStream', $inputCallback = false )
3358         {
3359                 $cmd = '';
3360
3361                 while ( !feof( $fp ) ) {
3362                         if ( $lineCallback ) {
3363                                 call_user_func( $lineCallback );
3364                         }
3365
3366                         $line = trim( fgets( $fp ) );
3367
3368                         if ( $line == '' ) {
3369                                 continue;
3370                         }
3371
3372                         if ( '-' == $line[0] && '-' == $line[1] ) {
3373                                 continue;
3374                         }
3375
3376                         if ( $cmd != '' ) {
3377                                 $cmd .= ' ';
3378                         }
3379
3380                         $done = $this->streamStatementEnd( $cmd, $line );
3381
3382                         $cmd .= "$line\n";
3383
3384                         if ( $done || feof( $fp ) ) {
3385                                 $cmd = $this->replaceVars( $cmd );
3386
3387                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3388                                         $res = $this->query( $cmd, $fname );
3389
3390                                         if ( $resultCallback ) {
3391                                                 call_user_func( $resultCallback, $res, $this );
3392                                         }
3393
3394                                         if ( false === $res ) {
3395                                                 $err = $this->lastError();
3396                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3397                                         }
3398                                 }
3399                                 $cmd = '';
3400                         }
3401                 }
3402
3403                 return true;
3404         }
3405
3406         /**
3407          * Called by sourceStream() to check if we've reached a statement end
3408          *
3409          * @param $sql String SQL assembled so far
3410          * @param $newLine String New line about to be added to $sql
3411          * @return Bool Whether $newLine contains end of the statement
3412          */
3413         public function streamStatementEnd( &$sql, &$newLine ) {
3414                 if ( $this->delimiter ) {
3415                         $prev = $newLine;
3416                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3417                         if ( $newLine != $prev ) {
3418                                 return true;
3419                         }
3420                 }
3421                 return false;
3422         }
3423
3424         /**
3425          * Database independent variable replacement. Replaces a set of variables
3426          * in an SQL statement with their contents as given by $this->getSchemaVars().
3427          *
3428          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3429          *
3430          * - '{$var}' should be used for text and is passed through the database's
3431          *   addQuotes method.
3432          * - `{$var}` should be used for identifiers (eg: table and database names),
3433          *   it is passed through the database's addIdentifierQuotes method which
3434          *   can be overridden if the database uses something other than backticks.
3435          * - / *$var* / is just encoded, besides traditional table prefix and
3436          *   table options its use should be avoided.
3437          *
3438          * @param $ins String: SQL statement to replace variables in
3439          * @return String The new SQL statement with variables replaced
3440          */
3441         protected function replaceSchemaVars( $ins ) {
3442                 $vars = $this->getSchemaVars();
3443                 foreach ( $vars as $var => $value ) {
3444                         // replace '{$var}'
3445                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3446                         // replace `{$var}`
3447                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3448                         // replace /*$var*/
3449                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ) , $ins );
3450                 }
3451                 return $ins;
3452         }
3453
3454         /**
3455          * Replace variables in sourced SQL
3456          *
3457          * @param $ins string
3458          *
3459          * @return string
3460          */
3461         protected function replaceVars( $ins ) {
3462                 $ins = $this->replaceSchemaVars( $ins );
3463
3464                 // Table prefixes
3465                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3466                         array( $this, 'tableNameCallback' ), $ins );
3467
3468                 // Index names
3469                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3470                         array( $this, 'indexNameCallback' ), $ins );
3471
3472                 return $ins;
3473         }
3474
3475         /**
3476          * Get schema variables. If none have been set via setSchemaVars(), then
3477          * use some defaults from the current object.
3478          *
3479          * @return array
3480          */
3481         protected function getSchemaVars() {
3482                 if ( $this->mSchemaVars ) {
3483                         return $this->mSchemaVars;
3484                 } else {
3485                         return $this->getDefaultSchemaVars();
3486                 }
3487         }
3488
3489         /**
3490          * Get schema variables to use if none have been set via setSchemaVars().
3491          *
3492          * Override this in derived classes to provide variables for tables.sql
3493          * and SQL patch files.
3494          *
3495          * @return array
3496          */
3497         protected function getDefaultSchemaVars() {
3498                 return array();
3499         }
3500
3501         /**
3502          * Table name callback
3503          *
3504          * @param $matches array
3505          *
3506          * @return string
3507          */
3508         protected function tableNameCallback( $matches ) {
3509                 return $this->tableName( $matches[1] );
3510         }
3511
3512         /**
3513          * Index name callback
3514          *
3515          * @param $matches array
3516          *
3517          * @return string
3518          */
3519         protected function indexNameCallback( $matches ) {
3520                 return $this->indexName( $matches[1] );
3521         }
3522
3523         /**
3524          * Check to see if a named lock is available. This is non-blocking.
3525          *
3526          * @param $lockName String: name of lock to poll
3527          * @param $method String: name of method calling us
3528          * @return Boolean
3529          * @since 1.20
3530          */
3531         public function lockIsFree( $lockName, $method ) {
3532                 return true;
3533         }
3534
3535         /**
3536          * Acquire a named lock
3537          *
3538          * Abstracted from Filestore::lock() so child classes can implement for
3539          * their own needs.
3540          *
3541          * @param $lockName String: name of lock to aquire
3542          * @param $method String: name of method calling us
3543          * @param $timeout Integer: timeout
3544          * @return Boolean
3545          */
3546         public function lock( $lockName, $method, $timeout = 5 ) {
3547                 return true;
3548         }
3549
3550         /**
3551          * Release a lock.
3552          *
3553          * @param $lockName String: Name of lock to release
3554          * @param $method String: Name of method calling us
3555          *
3556          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3557          * by this thread (in which case the lock is not released), and NULL if the named
3558          * lock did not exist
3559          */
3560         public function unlock( $lockName, $method ) {
3561                 return true;
3562         }
3563
3564         /**
3565          * Lock specific tables
3566          *
3567          * @param $read Array of tables to lock for read access
3568          * @param $write Array of tables to lock for write access
3569          * @param $method String name of caller
3570          * @param $lowPriority bool Whether to indicate writes to be LOW PRIORITY
3571          *
3572          * @return bool
3573          */
3574         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3575                 return true;
3576         }
3577
3578         /**
3579          * Unlock specific tables
3580          *
3581          * @param $method String the caller
3582          *
3583          * @return bool
3584          */
3585         public function unlockTables( $method ) {
3586                 return true;
3587         }
3588
3589         /**
3590          * Delete a table
3591          * @param $tableName string
3592          * @param $fName string
3593          * @return bool|ResultWrapper
3594          * @since 1.18
3595          */
3596         public function dropTable( $tableName, $fName = 'DatabaseBase::dropTable' ) {
3597                 if( !$this->tableExists( $tableName, $fName ) ) {
3598                         return false;
3599                 }
3600                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3601                 if( $this->cascadingDeletes() ) {
3602                         $sql .= " CASCADE";
3603                 }
3604                 return $this->query( $sql, $fName );
3605         }
3606
3607         /**
3608          * Get search engine class. All subclasses of this need to implement this
3609          * if they wish to use searching.
3610          *
3611          * @return String
3612          */
3613         public function getSearchEngine() {
3614                 return 'SearchEngineDummy';
3615         }
3616
3617         /**
3618          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3619          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3620          * because "i" sorts after all numbers.
3621          *
3622          * @return String
3623          */
3624         public function getInfinity() {
3625                 return 'infinity';
3626         }
3627
3628         /**
3629          * Encode an expiry time into the DBMS dependent format
3630          *
3631          * @param $expiry String: timestamp for expiry, or the 'infinity' string
3632          * @return String
3633          */
3634         public function encodeExpiry( $expiry ) {
3635                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3636                         ? $this->getInfinity()
3637                         : $this->timestamp( $expiry );
3638         }
3639
3640         /**
3641          * Decode an expiry time into a DBMS independent format
3642          *
3643          * @param $expiry String: DB timestamp field value for expiry
3644          * @param $format integer: TS_* constant, defaults to TS_MW
3645          * @return String
3646          */
3647         public function decodeExpiry( $expiry, $format = TS_MW ) {
3648                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3649                         ? 'infinity'
3650                         : wfTimestamp( $format, $expiry );
3651         }
3652
3653         /**
3654          * Allow or deny "big selects" for this session only. This is done by setting
3655          * the sql_big_selects session variable.
3656          *
3657          * This is a MySQL-specific feature.
3658          *
3659          * @param $value Mixed: true for allow, false for deny, or "default" to
3660          *   restore the initial value
3661          */
3662         public function setBigSelects( $value = true ) {
3663                 // no-op
3664         }
3665
3666         /**
3667          * @since 1.19
3668          */
3669         public function __toString() {
3670                 return (string)$this->mConn;
3671         }
3672
3673         public function __destruct() {
3674                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
3675                         trigger_error( "Transaction idle callbacks still pending." );
3676                 }
3677         }
3678 }