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 string $server database server host
  53          * @param string $user database user name
  54          * @param string $password database user password
  55          * @param string $dbName 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          * If no more rows are available, false is returned.
  66          *
  67          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  68          * @return object|bool
  69          * @throws DBUnexpectedError Thrown if the database returns an error
  70          */
  71         function fetchObject( $res );
  72
  73         /**
  74          * Fetch the next row from the given result object, in associative array
  75          * form.  Fields are retrieved with $row['fieldname'].
  76          * If no more rows are available, false is returned.
  77          *
  78          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  79          * @return array|bool
  80          * @throws DBUnexpectedError Thrown if the database returns an error
  81          */
  82         function fetchRow( $res );
  83
  84         /**
  85          * Get the number of rows in a result object
  86          *
  87          * @param $res Mixed: A SQL result
  88          * @return int
  89          */
  90         function numRows( $res );
  91
  92         /**
  93          * Get the number of fields in a result object
  94          * @see http://www.php.net/mysql_num_fields
  95          *
  96          * @param $res Mixed: A SQL result
  97          * @return int
  98          */
  99         function numFields( $res );
 100
 101         /**
 102          * Get a field name in a result object
 103          * @see http://www.php.net/mysql_field_name
 104          *
 105          * @param $res Mixed: A SQL result
 106          * @param $n Integer
 107          * @return string
 108          */
 109         function fieldName( $res, $n );
 110
 111         /**
 112          * Get the inserted value of an auto-increment row
 113          *
 114          * The value inserted should be fetched from nextSequenceValue()
 115          *
 116          * Example:
 117          * $id = $dbw->nextSequenceValue( 'page_page_id_seq' );
 118          * $dbw->insert( 'page', array( 'page_id' => $id ) );
 119          * $id = $dbw->insertId();
 120          *
 121          * @return int
 122          */
 123         function insertId();
 124
 125         /**
 126          * Change the position of the cursor in a result object
 127          * @see http://www.php.net/mysql_data_seek
 128          *
 129          * @param $res Mixed: A SQL result
 130          * @param $row Mixed: Either MySQL row or ResultWrapper
 131          */
 132         function dataSeek( $res, $row );
 133
 134         /**
 135          * Get the last error number
 136          * @see http://www.php.net/mysql_errno
 137          *
 138          * @return int
 139          */
 140         function lastErrno();
 141
 142         /**
 143          * Get a description of the last error
 144          * @see http://www.php.net/mysql_error
 145          *
 146          * @return string
 147          */
 148         function lastError();
 149
 150         /**
 151          * mysql_fetch_field() wrapper
 152          * Returns false if the field doesn't exist
 153          *
 154          * @param string $table table name
 155          * @param string $field field name
 156          *
 157          * @return Field
 158          */
 159         function fieldInfo( $table, $field );
 160
 161         /**
 162          * Get information about an index into an object
 163          * @param string $table Table name
 164          * @param string $index Index name
 165          * @param string $fname Calling function name
 166          * @return Mixed: Database-specific index description class or false if the index does not exist
 167          */
 168         function indexInfo( $table, $index, $fname = 'Database::indexInfo' );
 169
 170         /**
 171          * Get the number of rows affected by the last write query
 172          * @see http://www.php.net/mysql_affected_rows
 173          *
 174          * @return int
 175          */
 176         function affectedRows();
 177
 178         /**
 179          * Wrapper for addslashes()
 180          *
 181          * @param string $s to be slashed.
 182          * @return string: slashed string.
 183          */
 184         function strencode( $s );
 185
 186         /**
 187          * Returns a wikitext link to the DB's website, e.g.,
 188          *     return "[http://www.mysql.com/ MySQL]";
 189          * Should at least contain plain text, if for some reason
 190          * your database has no website.
 191          *
 192          * @return string: wikitext of a link to the server software's web site
 193          */
 194         static function getSoftwareLink();
 195
 196         /**
 197          * A string describing the current software version, like from
 198          * mysql_get_server_info().
 199          *
 200          * @return string: Version information from the database server.
 201          */
 202         function getServerVersion();
 203
 204         /**
 205          * A string describing the current software version, and possibly
 206          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 207          * Use getServerVersion() to get machine-friendly information.
 208          *
 209          * @return string: Version information from the database server
 210          */
 211         function getServerInfo();
 212 }
 213
 214 /**
 215  * Database abstraction object
 216  * @ingroup Database
 217  */
 218 abstract class DatabaseBase implements DatabaseType {
 219
 220 # ------------------------------------------------------------------------------
 221 # Variables
 222 # ------------------------------------------------------------------------------
 223
 224         protected $mLastQuery = '';
 225         protected $mDoneWrites = false;
 226         protected $mPHPError = false;
 227
 228         protected $mServer, $mUser, $mPassword, $mDBname;
 229
 230         protected $mConn = null;
 231         protected $mOpened = false;
 232
 233         /**
 234          * @since 1.20
 235          * @var array of Closure
 236          */
 237         protected $mTrxIdleCallbacks = array();
 238
 239         protected $mTablePrefix;
 240         protected $mFlags;
 241         protected $mTrxLevel = 0;
 242         protected $mErrorCount = 0;
 243         protected $mLBInfo = array();
 244         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 245         protected $mDefaultBigSelects = null;
 246         protected $mSchemaVars = false;
 247
 248         protected $preparedArgs;
 249
 250         protected $htmlErrors;
 251
 252         protected $delimiter = ';';
 253
 254         /**
 255          * Remembers the function name given for starting the most recent transaction via begin().
 256          * Used to provide additional context for error reporting.
 257          *
 258          * @var String
 259          * @see DatabaseBase::mTrxLevel
 260          */
 261         private $mTrxFname = null;
 262
 263         /**
 264          * Record if possible write queries were done in the last transaction started
 265          *
 266          * @var Bool
 267          * @see DatabaseBase::mTrxLevel
 268          */
 269         private $mTrxDoneWrites = false;
 270
 271         /**
 272          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 273          *
 274          * @var Bool
 275          * @see DatabaseBase::mTrxLevel
 276          */
 277         private $mTrxAutomatic = false;
 278
 279         /**
 280          * @since 1.21
 281          * @var file handle for upgrade
 282          */
 283         protected $fileHandle = null;
 284
 285 # ------------------------------------------------------------------------------
 286 # Accessors
 287 # ------------------------------------------------------------------------------
 288         # These optionally set a variable and return the previous state
 289
 290         /**
 291          * A string describing the current software version, and possibly
 292          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 293          * Use getServerVersion() to get machine-friendly information.
 294          *
 295          * @return string: Version information from the database server
 296          */
 297         public function getServerInfo() {
 298                 return $this->getServerVersion();
 299         }
 300
 301         /**
 302          * @return string: command delimiter used by this database engine
 303          */
 304         public function getDelimiter() {
 305                 return $this->delimiter;
 306         }
 307
 308         /**
 309          * Boolean, controls output of large amounts of debug information.
 310          * @param $debug bool|null
 311          *   - true to enable debugging
 312          *   - false to disable debugging
 313          *   - omitted or null to do nothing
 314          *
 315          * @return bool|null previous value of the flag
 316          */
 317         public function debug( $debug = null ) {
 318                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 319         }
 320
 321         /**
 322          * Turns buffering of SQL result sets on (true) or off (false). Default is
 323          * "on".
 324          *
 325          * Unbuffered queries are very troublesome in MySQL:
 326          *
 327          *   - If another query is executed while the first query is being read
 328          *     out, the first query is killed. This means you can't call normal
 329          *     MediaWiki functions while you are reading an unbuffered query result
 330          *     from a normal wfGetDB() connection.
 331          *
 332          *   - Unbuffered queries cause the MySQL server to use large amounts of
 333          *     memory and to hold broad locks which block other queries.
 334          *
 335          * If you want to limit client-side memory, it's almost always better to
 336          * split up queries into batches using a LIMIT clause than to switch off
 337          * buffering.
 338          *
 339          * @param $buffer null|bool
 340          *
 341          * @return null|bool The previous value of the flag
 342          */
 343         public function bufferResults( $buffer = null ) {
 344                 if ( is_null( $buffer ) ) {
 345                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 346                 } else {
 347                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 348                 }
 349         }
 350
 351         /**
 352          * Turns on (false) or off (true) the automatic generation and sending
 353          * of a "we're sorry, but there has been a database error" page on
 354          * database errors. Default is on (false). When turned off, the
 355          * code should use lastErrno() and lastError() to handle the
 356          * situation as appropriate.
 357          *
 358          * @param $ignoreErrors bool|null
 359          *
 360          * @return bool The previous value of the flag.
 361          */
 362         public function ignoreErrors( $ignoreErrors = null ) {
 363                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 364         }
 365
 366         /**
 367          * Gets or sets the current transaction level.
 368          *
 369          * Historically, transactions were allowed to be "nested". This is no
 370          * longer supported, so this function really only returns a boolean.
 371          *
 372          * @param int $level An integer (0 or 1), or omitted to leave it unchanged.
 373          * @return int The previous value
 374          */
 375         public function trxLevel( $level = null ) {
 376                 return wfSetVar( $this->mTrxLevel, $level );
 377         }
 378
 379         /**
 380          * Get/set the number of errors logged. Only useful when errors are ignored
 381          * @param int $count The count to set, or omitted to leave it unchanged.
 382          * @return int The error count
 383          */
 384         public function errorCount( $count = null ) {
 385                 return wfSetVar( $this->mErrorCount, $count );
 386         }
 387
 388         /**
 389          * Get/set the table prefix.
 390          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 391          * @return string The previous table prefix.
 392          */
 393         public function tablePrefix( $prefix = null ) {
 394                 return wfSetVar( $this->mTablePrefix, $prefix );
 395         }
 396
 397         /**
 398          * Set the filehandle to copy write statements to.
 399          *
 400          * @param $fh filehandle
 401          */
 402         public function setFileHandle( $fh ) {
 403                 $this->fileHandle = $fh;
 404         }
 405
 406         /**
 407          * Get properties passed down from the server info array of the load
 408          * balancer.
 409          *
 410          * @param string $name The entry of the info array to get, or null to get the
 411          *   whole array
 412          *
 413          * @return LoadBalancer|null
 414          */
 415         public function getLBInfo( $name = null ) {
 416                 if ( is_null( $name ) ) {
 417                         return $this->mLBInfo;
 418                 } else {
 419                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 420                                 return $this->mLBInfo[$name];
 421                         } else {
 422                                 return null;
 423                         }
 424                 }
 425         }
 426
 427         /**
 428          * Set the LB info array, or a member of it. If called with one parameter,
 429          * the LB info array is set to that parameter. If it is called with two
 430          * parameters, the member with the given name is set to the given value.
 431          *
 432          * @param $name
 433          * @param $value
 434          */
 435         public function setLBInfo( $name, $value = null ) {
 436                 if ( is_null( $value ) ) {
 437                         $this->mLBInfo = $name;
 438                 } else {
 439                         $this->mLBInfo[$name] = $value;
 440                 }
 441         }
 442
 443         /**
 444          * Set lag time in seconds for a fake slave
 445          *
 446          * @param $lag int
 447          */
 448         public function setFakeSlaveLag( $lag ) {
 449                 $this->mFakeSlaveLag = $lag;
 450         }
 451
 452         /**
 453          * Make this connection a fake master
 454          *
 455          * @param $enabled bool
 456          */
 457         public function setFakeMaster( $enabled = true ) {
 458                 $this->mFakeMaster = $enabled;
 459         }
 460
 461         /**
 462          * Returns true if this database supports (and uses) cascading deletes
 463          *
 464          * @return bool
 465          */
 466         public function cascadingDeletes() {
 467                 return false;
 468         }
 469
 470         /**
 471          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 472          *
 473          * @return bool
 474          */
 475         public function cleanupTriggers() {
 476                 return false;
 477         }
 478
 479         /**
 480          * Returns true if this database is strict about what can be put into an IP field.
 481          * Specifically, it uses a NULL value instead of an empty string.
 482          *
 483          * @return bool
 484          */
 485         public function strictIPs() {
 486                 return false;
 487         }
 488
 489         /**
 490          * Returns true if this database uses timestamps rather than integers
 491          *
 492          * @return bool
 493          */
 494         public function realTimestamps() {
 495                 return false;
 496         }
 497
 498         /**
 499          * Returns true if this database does an implicit sort when doing GROUP BY
 500          *
 501          * @return bool
 502          */
 503         public function implicitGroupby() {
 504                 return true;
 505         }
 506
 507         /**
 508          * Returns true if this database does an implicit order by when the column has an index
 509          * For example: SELECT page_title FROM page LIMIT 1
 510          *
 511          * @return bool
 512          */
 513         public function implicitOrderby() {
 514                 return true;
 515         }
 516
 517         /**
 518          * Returns true if this database can do a native search on IP columns
 519          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 520          *
 521          * @return bool
 522          */
 523         public function searchableIPs() {
 524                 return false;
 525         }
 526
 527         /**
 528          * Returns true if this database can use functional indexes
 529          *
 530          * @return bool
 531          */
 532         public function functionalIndexes() {
 533                 return false;
 534         }
 535
 536         /**
 537          * Return the last query that went through DatabaseBase::query()
 538          * @return String
 539          */
 540         public function lastQuery() {
 541                 return $this->mLastQuery;
 542         }
 543
 544         /**
 545          * Returns true if the connection may have been used for write queries.
 546          * Should return true if unsure.
 547          *
 548          * @return bool
 549          */
 550         public function doneWrites() {
 551                 return $this->mDoneWrites;
 552         }
 553
 554         /**
 555          * Returns true if there is a transaction open with possible write
 556          * queries or transaction idle callbacks waiting on it to finish.
 557          *
 558          * @return bool
 559          */
 560         public function writesOrCallbacksPending() {
 561                 return $this->mTrxLevel && ( $this->mTrxDoneWrites || $this->mTrxIdleCallbacks );
 562         }
 563
 564         /**
 565          * Is a connection to the database open?
 566          * @return Boolean
 567          */
 568         public function isOpen() {
 569                 return $this->mOpened;
 570         }
 571
 572         /**
 573          * Set a flag for this connection
 574          *
 575          * @param $flag Integer: DBO_* constants from Defines.php:
 576          *   - DBO_DEBUG: output some debug info (same as debug())
 577          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 578          *   - DBO_IGNORE: ignore errors (same as ignoreErrors())
 579          *   - DBO_TRX: automatically start transactions
 580          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 581          *       and removes it in command line mode
 582          *   - DBO_PERSISTENT: use persistant database connection
 583          */
 584         public function setFlag( $flag ) {
 585                 global $wgDebugDBTransactions;
 586                 $this->mFlags |= $flag;
 587                 if ( ( $flag & DBO_TRX) & $wgDebugDBTransactions ) {
 588                         wfDebug( "Implicit transactions are now  disabled.\n" );
 589                 }
 590         }
 591
 592         /**
 593          * Clear a flag for this connection
 594          *
 595          * @param $flag: same as setFlag()'s $flag param
 596          */
 597         public function clearFlag( $flag ) {
 598                 global $wgDebugDBTransactions;
 599                 $this->mFlags &= ~$flag;
 600                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 601                         wfDebug( "Implicit transactions are now disabled.\n" );
 602                 }
 603         }
 604
 605         /**
 606          * Returns a boolean whether the flag $flag is set for this connection
 607          *
 608          * @param $flag: same as setFlag()'s $flag param
 609          * @return Boolean
 610          */
 611         public function getFlag( $flag ) {
 612                 return !!( $this->mFlags & $flag );
 613         }
 614
 615         /**
 616          * General read-only accessor
 617          *
 618          * @param $name string
 619          *
 620          * @return string
 621          */
 622         public function getProperty( $name ) {
 623                 return $this->$name;
 624         }
 625
 626         /**
 627          * @return string
 628          */
 629         public function getWikiID() {
 630                 if ( $this->mTablePrefix ) {
 631                         return "{$this->mDBname}-{$this->mTablePrefix}";
 632                 } else {
 633                         return $this->mDBname;
 634                 }
 635         }
 636
 637         /**
 638          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 639          *
 640          * @return string
 641          */
 642         public function getSchemaPath() {
 643                 global $IP;
 644                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 645                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 646                 } else {
 647                         return "$IP/maintenance/tables.sql";
 648                 }
 649         }
 650
 651 # ------------------------------------------------------------------------------
 652 # Other functions
 653 # ------------------------------------------------------------------------------
 654
 655         /**
 656          * Constructor.
 657          * @param string $server database server host
 658          * @param string $user database user name
 659          * @param string $password database user password
 660          * @param string $dbName database name
 661          * @param $flags
 662          * @param string $tablePrefix database table prefixes. By default use the prefix gave in LocalSettings.php
 663          */
 664         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 665                 $flags = 0, $tablePrefix = 'get from global'
 666         ) {
 667                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 668
 669                 $this->mFlags = $flags;
 670
 671                 if ( $this->mFlags & DBO_DEFAULT ) {
 672                         if ( $wgCommandLineMode ) {
 673                                 $this->mFlags &= ~DBO_TRX;
 674                                 if ( $wgDebugDBTransactions ) {
 675                                         wfDebug( "Implicit transaction open disabled.\n" );
 676                                 }
 677                         } else {
 678                                 $this->mFlags |= DBO_TRX;
 679                                 if ( $wgDebugDBTransactions ) {
 680                                         wfDebug( "Implicit transaction open enabled.\n" );
 681                                 }
 682                         }
 683                 }
 684
 685                 /** Get the default table prefix*/
 686                 if ( $tablePrefix == 'get from global' ) {
 687                         $this->mTablePrefix = $wgDBprefix;
 688                 } else {
 689                         $this->mTablePrefix = $tablePrefix;
 690                 }
 691
 692                 if ( $user ) {
 693                         $this->open( $server, $user, $password, $dbName );
 694                 }
 695         }
 696
 697         /**
 698          * Called by serialize. Throw an exception when DB connection is serialized.
 699          * This causes problems on some database engines because the connection is
 700          * not restored on unserialize.
 701          */
 702         public function __sleep() {
 703                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 704         }
 705
 706         /**
 707          * Given a DB type, construct the name of the appropriate child class of
 708          * DatabaseBase. This is designed to replace all of the manual stuff like:
 709          *      $class = 'Database' . ucfirst( strtolower( $type ) );
 710          * as well as validate against the canonical list of DB types we have
 711          *
 712          * This factory function is mostly useful for when you need to connect to a
 713          * database other than the MediaWiki default (such as for external auth,
 714          * an extension, et cetera). Do not use this to connect to the MediaWiki
 715          * database. Example uses in core:
 716          * @see LoadBalancer::reallyOpenConnection()
 717          * @see ForeignDBRepo::getMasterDB()
 718          * @see WebInstaller_DBConnect::execute()
 719          *
 720          * @since 1.18
 721          *
 722          * @param string $dbType A possible DB type
 723          * @param array $p 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         final public static function factory( $dbType, $p = array() ) {
 728                 $canonicalDBTypes = array(
 729                         'mysql', 'postgres', 'sqlite', 'oracle', 'mssql'
 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          * @throws MWException
 784          * @return Bool operation success. true if already closed.
 785          */
 786         public function close() {
 787                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 788                         throw new MWException( "Transaction idle callbacks still pending." );
 789                 }
 790                 $this->mOpened = false;
 791                 if ( $this->mConn ) {
 792                         if ( $this->trxLevel() ) {
 793                                 if ( !$this->mTrxAutomatic ) {
 794                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 795                                                 " performing implicit commit before closing connection!" );
 796                                 }
 797
 798                                 $this->commit( __METHOD__, 'flush' );
 799                         }
 800
 801                         $ret = $this->closeConnection();
 802                         $this->mConn = false;
 803                         return $ret;
 804                 } else {
 805                         return true;
 806                 }
 807         }
 808
 809         /**
 810          * Closes underlying database connection
 811          * @since 1.20
 812          * @return bool: Whether connection was closed successfully
 813          */
 814         abstract protected function closeConnection();
 815
 816         /**
 817          * @param string $error fallback error message, used if none is given by DB
 818          * @throws DBConnectionError
 819          */
 820         function reportConnectionError( $error = 'Unknown error' ) {
 821                 $myError = $this->lastError();
 822                 if ( $myError ) {
 823                         $error = $myError;
 824                 }
 825
 826                 # New method
 827                 throw new DBConnectionError( $this, $error );
 828         }
 829
 830         /**
 831          * The DBMS-dependent part of query()
 832          *
 833          * @param  $sql String: SQL query.
 834          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 835          */
 836         abstract protected function doQuery( $sql );
 837
 838         /**
 839          * Determine whether a query writes to the DB.
 840          * Should return true if unsure.
 841          *
 842          * @param $sql string
 843          *
 844          * @return bool
 845          */
 846         public function isWriteQuery( $sql ) {
 847                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 848         }
 849
 850         /**
 851          * Run an SQL query and return the result. Normally throws a DBQueryError
 852          * on failure. If errors are ignored, returns false instead.
 853          *
 854          * In new code, the query wrappers select(), insert(), update(), delete(),
 855          * etc. should be used where possible, since they give much better DBMS
 856          * independence and automatically quote or validate user input in a variety
 857          * of contexts. This function is generally only useful for queries which are
 858          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 859          * as CREATE TABLE.
 860          *
 861          * However, the query wrappers themselves should call this function.
 862          *
 863          * @param  $sql        String: SQL query
 864          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 865          *     comment (you can use __METHOD__ or add some extra info)
 866          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 867          *     maybe best to catch the exception instead?
 868          * @throws MWException
 869          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 870          *     for a successful read query, or false on failure if $tempIgnore set
 871          */
 872         public function query( $sql, $fname = '', $tempIgnore = false ) {
 873                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 874                 if ( !Profiler::instance()->isStub() ) {
 875                         # generalizeSQL will probably cut down the query to reasonable
 876                         # logging size most of the time. The substr is really just a sanity check.
 877
 878                         if ( $isMaster ) {
 879                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 880                                 $totalProf = 'DatabaseBase::query-master';
 881                         } else {
 882                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 883                                 $totalProf = 'DatabaseBase::query';
 884                         }
 885
 886                         wfProfileIn( $totalProf );
 887                         wfProfileIn( $queryProf );
 888                 }
 889
 890                 $this->mLastQuery = $sql;
 891                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 892                         # Set a flag indicating that writes have been done
 893                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 894                         $this->mDoneWrites = true;
 895                 }
 896
 897                 # Add a comment for easy SHOW PROCESSLIST interpretation
 898                 global $wgUser;
 899                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 900                         $userName = $wgUser->getName();
 901                         if ( mb_strlen( $userName ) > 15 ) {
 902                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 903                         }
 904                         $userName = str_replace( '/', '', $userName );
 905                 } else {
 906                         $userName = '';
 907                 }
 908
 909                 // Add trace comment to the begin of the sql string, right after the operator.
 910                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 911                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 912
 913                 # If DBO_TRX is set, start a transaction
 914                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 915                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' )
 916                 {
 917                         # Avoid establishing transactions for SHOW and SET statements too -
 918                         # that would delay transaction initializations to once connection
 919                         # is really used by application
 920                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 921                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 922                                 global $wgDebugDBTransactions;
 923                                 if ( $wgDebugDBTransactions ) {
 924                                         wfDebug( "Implicit transaction start.\n" );
 925                                 }
 926                                 $this->begin( __METHOD__ . " ($fname)" );
 927                                 $this->mTrxAutomatic = true;
 928                         }
 929                 }
 930
 931                 # Keep track of whether the transaction has write queries pending
 932                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
 933                         $this->mTrxDoneWrites = true;
 934                 }
 935
 936                 if ( $this->debug() ) {
 937                         static $cnt = 0;
 938
 939                         $cnt++;
 940                         $sqlx = substr( $commentedSql, 0, 500 );
 941                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 942
 943                         $master = $isMaster ? 'master' : 'slave';
 944                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 945                 }
 946
 947                 if ( istainted( $sql ) & TC_MYSQL ) {
 948                         if ( !Profiler::instance()->isStub() ) {
 949                                 wfProfileOut( $queryProf );
 950                                 wfProfileOut( $totalProf );
 951                         }
 952                         throw new MWException( 'Tainted query found' );
 953                 }
 954
 955                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 956
 957                 # Do the query and handle errors
 958                 $ret = $this->doQuery( $commentedSql );
 959
 960                 MWDebug::queryTime( $queryId );
 961
 962                 # Try reconnecting if the connection was lost
 963                 if ( false === $ret && $this->wasErrorReissuable() ) {
 964                         # Transaction is gone, like it or not
 965                         $this->mTrxLevel = 0;
 966                         $this->mTrxIdleCallbacks = array(); // cancel
 967                         wfDebug( "Connection lost, reconnecting...\n" );
 968
 969                         if ( $this->ping() ) {
 970                                 wfDebug( "Reconnected\n" );
 971                                 $sqlx = substr( $commentedSql, 0, 500 );
 972                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
 973                                 global $wgRequestTime;
 974                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
 975                                 if ( $elapsed < 300 ) {
 976                                         # Not a database error to lose a transaction after a minute or two
 977                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
 978                                 }
 979                                 $ret = $this->doQuery( $commentedSql );
 980                         } else {
 981                                 wfDebug( "Failed\n" );
 982                         }
 983                 }
 984
 985                 if ( false === $ret ) {
 986                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 987                 }
 988
 989                 if ( !Profiler::instance()->isStub() ) {
 990                         wfProfileOut( $queryProf );
 991                         wfProfileOut( $totalProf );
 992                 }
 993
 994                 return $this->resultObject( $ret );
 995         }
 996
 997         /**
 998          * Report a query error. Log the error, and if neither the object ignore
 999          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1000          *
1001          * @param $error String
1002          * @param $errno Integer
1003          * @param $sql String
1004          * @param $fname String
1005          * @param $tempIgnore Boolean
1006          * @throws DBQueryError
1007          */
1008         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1009                 # Ignore errors during error handling to avoid infinite recursion
1010                 $ignore = $this->ignoreErrors( true );
1011                 ++$this->mErrorCount;
1012
1013                 if ( $ignore || $tempIgnore ) {
1014                         wfDebug( "SQL ERROR (ignored): $error\n" );
1015                         $this->ignoreErrors( $ignore );
1016                 } else {
1017                         $sql1line = str_replace( "\n", "\\n", $sql );
1018                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
1019                         wfDebug( "SQL ERROR: " . $error . "\n" );
1020                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1021                 }
1022         }
1023
1024         /**
1025          * Intended to be compatible with the PEAR::DB wrapper functions.
1026          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1027          *
1028          * ? = scalar value, quoted as necessary
1029          * ! = raw SQL bit (a function for instance)
1030          * & = filename; reads the file and inserts as a blob
1031          *     (we don't use this though...)
1032          *
1033          * @param $sql string
1034          * @param $func string
1035          *
1036          * @return array
1037          */
1038         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1039                 /* MySQL doesn't support prepared statements (yet), so just
1040                    pack up the query for reference. We'll manually replace
1041                    the bits later. */
1042                 return array( 'query' => $sql, 'func' => $func );
1043         }
1044
1045         /**
1046          * Free a prepared query, generated by prepare().
1047          * @param $prepared
1048          */
1049         protected function freePrepared( $prepared ) {
1050                 /* No-op by default */
1051         }
1052
1053         /**
1054          * Execute a prepared query with the various arguments
1055          * @param string $prepared the prepared sql
1056          * @param $args Mixed: Either an array here, or put scalars as varargs
1057          *
1058          * @return ResultWrapper
1059          */
1060         public function execute( $prepared, $args = null ) {
1061                 if ( !is_array( $args ) ) {
1062                         # Pull the var args
1063                         $args = func_get_args();
1064                         array_shift( $args );
1065                 }
1066
1067                 $sql = $this->fillPrepared( $prepared['query'], $args );
1068
1069                 return $this->query( $sql, $prepared['func'] );
1070         }
1071
1072         /**
1073          * For faking prepared SQL statements on DBs that don't support it directly.
1074          *
1075          * @param string $preparedQuery a 'preparable' SQL statement
1076          * @param array $args of arguments to fill it with
1077          * @return string executable SQL
1078          */
1079         public function fillPrepared( $preparedQuery, $args ) {
1080                 reset( $args );
1081                 $this->preparedArgs =& $args;
1082
1083                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1084                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1085         }
1086
1087         /**
1088          * preg_callback func for fillPrepared()
1089          * The arguments should be in $this->preparedArgs and must not be touched
1090          * while we're doing this.
1091          *
1092          * @param $matches Array
1093          * @throws DBUnexpectedError
1094          * @return String
1095          */
1096         protected function fillPreparedArg( $matches ) {
1097                 switch ( $matches[1] ) {
1098                         case '\\?':
1099                                 return '?';
1100                         case '\\!':
1101                                 return '!';
1102                         case '\\&':
1103                                 return '&';
1104                 }
1105
1106                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1107
1108                 switch ( $matches[1] ) {
1109                         case '?':
1110                                 return $this->addQuotes( $arg );
1111                         case '!':
1112                                 return $arg;
1113                         case '&':
1114                                 # return $this->addQuotes( file_get_contents( $arg ) );
1115                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1116                         default:
1117                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1118                 }
1119         }
1120
1121         /**
1122          * Free a result object returned by query() or select(). It's usually not
1123          * necessary to call this, just use unset() or let the variable holding
1124          * the result object go out of scope.
1125          *
1126          * @param $res Mixed: A SQL result
1127          */
1128         public function freeResult( $res ) {
1129         }
1130
1131         /**
1132          * A SELECT wrapper which returns a single field from a single result row.
1133          *
1134          * Usually throws a DBQueryError on failure. If errors are explicitly
1135          * ignored, returns false on failure.
1136          *
1137          * If no result rows are returned from the query, false is returned.
1138          *
1139          * @param string|array $table Table name. See DatabaseBase::select() for details.
1140          * @param string $var The field name to select. This must be a valid SQL
1141          *   fragment: do not use unvalidated user input.
1142          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1143          * @param string $fname The function name of the caller.
1144          * @param string|array $options The query options. See DatabaseBase::select() for details.
1145          *
1146          * @return bool|mixed The value from the field, or false on failure.
1147          */
1148         public function selectField( $table, $var, $cond = '', $fname = 'DatabaseBase::selectField',
1149                 $options = array()
1150         ) {
1151                 if ( !is_array( $options ) ) {
1152                         $options = array( $options );
1153                 }
1154
1155                 $options['LIMIT'] = 1;
1156
1157                 $res = $this->select( $table, $var, $cond, $fname, $options );
1158
1159                 if ( $res === false || !$this->numRows( $res ) ) {
1160                         return false;
1161                 }
1162
1163                 $row = $this->fetchRow( $res );
1164
1165                 if ( $row !== false ) {
1166                         return reset( $row );
1167                 } else {
1168                         return false;
1169                 }
1170         }
1171
1172         /**
1173          * Returns an optional USE INDEX clause to go after the table, and a
1174          * string to go at the end of the query.
1175          *
1176          * @param array $options associative array of options to be turned into
1177          *              an SQL query, valid keys are listed in the function.
1178          * @return Array
1179          * @see DatabaseBase::select()
1180          */
1181         public function makeSelectOptions( $options ) {
1182                 $preLimitTail = $postLimitTail = '';
1183                 $startOpts = '';
1184
1185                 $noKeyOptions = array();
1186
1187                 foreach ( $options as $key => $option ) {
1188                         if ( is_numeric( $key ) ) {
1189                                 $noKeyOptions[$option] = true;
1190                         }
1191                 }
1192
1193                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1194
1195                 $preLimitTail .= $this->makeOrderBy( $options );
1196
1197                 // if (isset($options['LIMIT'])) {
1198                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1199                 //              isset($options['OFFSET']) ? $options['OFFSET']
1200                 //              : false);
1201                 // }
1202
1203                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1204                         $postLimitTail .= ' FOR UPDATE';
1205                 }
1206
1207                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1208                         $postLimitTail .= ' LOCK IN SHARE MODE';
1209                 }
1210
1211                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1212                         $startOpts .= 'DISTINCT';
1213                 }
1214
1215                 # Various MySQL extensions
1216                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1217                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1218                 }
1219
1220                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1221                         $startOpts .= ' HIGH_PRIORITY';
1222                 }
1223
1224                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1225                         $startOpts .= ' SQL_BIG_RESULT';
1226                 }
1227
1228                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1229                         $startOpts .= ' SQL_BUFFER_RESULT';
1230                 }
1231
1232                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1233                         $startOpts .= ' SQL_SMALL_RESULT';
1234                 }
1235
1236                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1237                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1238                 }
1239
1240                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1241                         $startOpts .= ' SQL_CACHE';
1242                 }
1243
1244                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1245                         $startOpts .= ' SQL_NO_CACHE';
1246                 }
1247
1248                 if ( isset( $options['USE INDEX'] ) && ! is_array( $options['USE INDEX'] ) ) {
1249                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1250                 } else {
1251                         $useIndex = '';
1252                 }
1253
1254                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1255         }
1256
1257         /**
1258          * Returns an optional GROUP BY with an optional HAVING
1259          *
1260          * @param array $options associative array of options
1261          * @return string
1262          * @see DatabaseBase::select()
1263          * @since 1.21
1264          */
1265         public function makeGroupByWithHaving( $options ) {
1266                 $sql = '';
1267                 if ( isset( $options['GROUP BY'] ) ) {
1268                         $gb = is_array( $options['GROUP BY'] )
1269                                 ? implode( ',', $options['GROUP BY'] )
1270                                 : $options['GROUP BY'];
1271                         $sql .= ' GROUP BY ' . $gb;
1272                 }
1273                 if ( isset( $options['HAVING'] ) ) {
1274                         $having = is_array( $options['HAVING'] )
1275                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1276                                 : $options['HAVING'];
1277                         $sql .= ' HAVING ' . $having;
1278                 }
1279                 return $sql;
1280         }
1281
1282         /**
1283          * Returns an optional ORDER BY
1284          *
1285          * @param array $options associative array of options
1286          * @return string
1287          * @see DatabaseBase::select()
1288          * @since 1.21
1289          */
1290         public function makeOrderBy( $options ) {
1291                 if ( isset( $options['ORDER BY'] ) ) {
1292                         $ob = is_array( $options['ORDER BY'] )
1293                                 ? implode( ',', $options['ORDER BY'] )
1294                                 : $options['ORDER BY'];
1295                         return ' ORDER BY ' . $ob;
1296                 }
1297                 return '';
1298         }
1299
1300         /**
1301          * Execute a SELECT query constructed using the various parameters provided.
1302          * See below for full details of the parameters.
1303          *
1304          * @param string|array $table Table name
1305          * @param string|array $vars Field names
1306          * @param string|array $conds Conditions
1307          * @param string $fname Caller function name
1308          * @param array $options Query options
1309          * @param $join_conds Array Join conditions
1310          *
1311          * @param $table string|array
1312          *
1313          * May be either an array of table names, or a single string holding a table
1314          * name. If an array is given, table aliases can be specified, for example:
1315          *
1316          *    array( 'a' => 'user' )
1317          *
1318          * This includes the user table in the query, with the alias "a" available
1319          * for use in field names (e.g. a.user_name).
1320          *
1321          * All of the table names given here are automatically run through
1322          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1323          * added, and various other table name mappings to be performed.
1324          *
1325          *
1326          * @param $vars string|array
1327          *
1328          * May be either a field name or an array of field names. The field names
1329          * can be complete fragments of SQL, for direct inclusion into the SELECT
1330          * query. If an array is given, field aliases can be specified, for example:
1331          *
1332          *   array( 'maxrev' => 'MAX(rev_id)' )
1333          *
1334          * This includes an expression with the alias "maxrev" in the query.
1335          *
1336          * If an expression is given, care must be taken to ensure that it is
1337          * DBMS-independent.
1338          *
1339          *
1340          * @param $conds string|array
1341          *
1342          * May be either a string containing a single condition, or an array of
1343          * conditions. If an array is given, the conditions constructed from each
1344          * element are combined with AND.
1345          *
1346          * Array elements may take one of two forms:
1347          *
1348          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1349          *   - Elements with a string key are interpreted as equality conditions,
1350          *     where the key is the field name.
1351          *     - If the value of such an array element is a scalar (such as a
1352          *       string), it will be treated as data and thus quoted appropriately.
1353          *       If it is null, an IS NULL clause will be added.
1354          *     - If the value is an array, an IN(...) clause will be constructed,
1355          *       such that the field name may match any of the elements in the
1356          *       array. The elements of the array will be quoted.
1357          *
1358          * Note that expressions are often DBMS-dependent in their syntax.
1359          * DBMS-independent wrappers are provided for constructing several types of
1360          * expression commonly used in condition queries. See:
1361          *    - DatabaseBase::buildLike()
1362          *    - DatabaseBase::conditional()
1363          *
1364          *
1365          * @param $options string|array
1366          *
1367          * Optional: Array of query options. Boolean options are specified by
1368          * including them in the array as a string value with a numeric key, for
1369          * example:
1370          *
1371          *    array( 'FOR UPDATE' )
1372          *
1373          * The supported options are:
1374          *
1375          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1376          *     with LIMIT can theoretically be used for paging through a result set,
1377          *     but this is discouraged in MediaWiki for performance reasons.
1378          *
1379          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1380          *     and then the first rows are taken until the limit is reached. LIMIT
1381          *     is applied to a result set after OFFSET.
1382          *
1383          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1384          *     changed until the next COMMIT.
1385          *
1386          *   - DISTINCT: Boolean: return only unique result rows.
1387          *
1388          *   - GROUP BY: May be either an SQL fragment string naming a field or
1389          *     expression to group by, or an array of such SQL fragments.
1390          *
1391          *   - HAVING: May be either an string containing a HAVING clause or an array of
1392          *     conditions building the HAVING clause. If an array is given, the conditions
1393          *     constructed from each element are combined with AND.
1394          *
1395          *   - ORDER BY: May be either an SQL fragment giving a field name or
1396          *     expression to order by, or an array of such SQL fragments.
1397          *
1398          *   - USE INDEX: This may be either a string giving the index name to use
1399          *     for the query, or an array. If it is an associative array, each key
1400          *     gives the table name (or alias), each value gives the index name to
1401          *     use for that table. All strings are SQL fragments and so should be
1402          *     validated by the caller.
1403          *
1404          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1405          *     instead of SELECT.
1406          *
1407          * And also the following boolean MySQL extensions, see the MySQL manual
1408          * for documentation:
1409          *
1410          *    - LOCK IN SHARE MODE
1411          *    - STRAIGHT_JOIN
1412          *    - HIGH_PRIORITY
1413          *    - SQL_BIG_RESULT
1414          *    - SQL_BUFFER_RESULT
1415          *    - SQL_SMALL_RESULT
1416          *    - SQL_CALC_FOUND_ROWS
1417          *    - SQL_CACHE
1418          *    - SQL_NO_CACHE
1419          *
1420          *
1421          * @param $join_conds string|array
1422          *
1423          * Optional associative array of table-specific join conditions. In the
1424          * most common case, this is unnecessary, since the join condition can be
1425          * in $conds. However, it is useful for doing a LEFT JOIN.
1426          *
1427          * The key of the array contains the table name or alias. The value is an
1428          * array with two elements, numbered 0 and 1. The first gives the type of
1429          * join, the second is an SQL fragment giving the join condition for that
1430          * table. For example:
1431          *
1432          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1433          *
1434          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1435          *   with no rows in it will be returned. If there was a query error, a
1436          *   DBQueryError exception will be thrown, except if the "ignore errors"
1437          *   option was set, in which case false will be returned.
1438          */
1439         public function select( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1440                 $options = array(), $join_conds = array() ) {
1441                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1442
1443                 return $this->query( $sql, $fname );
1444         }
1445
1446         /**
1447          * The equivalent of DatabaseBase::select() except that the constructed SQL
1448          * is returned, instead of being immediately executed. This can be useful for
1449          * doing UNION queries, where the SQL text of each query is needed. In general,
1450          * however, callers outside of Database classes should just use select().
1451          *
1452          * @param string|array $table Table name
1453          * @param string|array $vars Field names
1454          * @param string|array $conds Conditions
1455          * @param string $fname Caller function name
1456          * @param string|array $options Query options
1457          * @param $join_conds string|array Join conditions
1458          *
1459          * @return string SQL query string.
1460          * @see DatabaseBase::select()
1461          */
1462         public function selectSQLText( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1463                 $options = array(), $join_conds = array() )
1464         {
1465                 if ( is_array( $vars ) ) {
1466                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1467                 }
1468
1469                 $options = (array)$options;
1470
1471                 if ( is_array( $table ) ) {
1472                         $useIndex = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1473                                 ? $options['USE INDEX']
1474                                 : array();
1475                         if ( count( $join_conds ) || count( $useIndex ) ) {
1476                                 $from = ' FROM ' .
1477                                         $this->tableNamesWithUseIndexOrJOIN( $table, $useIndex, $join_conds );
1478                         } else {
1479                                 $from = ' FROM ' . implode( ',', $this->tableNamesWithAlias( $table ) );
1480                         }
1481                 } elseif ( $table != '' ) {
1482                         if ( $table[0] == ' ' ) {
1483                                 $from = ' FROM ' . $table;
1484                         } else {
1485                                 $from = ' FROM ' . $this->tableName( $table );
1486                         }
1487                 } else {
1488                         $from = '';
1489                 }
1490
1491                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) = $this->makeSelectOptions( $options );
1492
1493                 if ( !empty( $conds ) ) {
1494                         if ( is_array( $conds ) ) {
1495                                 $conds = $this->makeList( $conds, LIST_AND );
1496                         }
1497                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1498                 } else {
1499                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1500                 }
1501
1502                 if ( isset( $options['LIMIT'] ) ) {
1503                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1504                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1505                 }
1506                 $sql = "$sql $postLimitTail";
1507
1508                 if ( isset( $options['EXPLAIN'] ) ) {
1509                         $sql = 'EXPLAIN ' . $sql;
1510                 }
1511
1512                 return $sql;
1513         }
1514
1515         /**
1516          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1517          * that a single row object is returned. If the query returns no rows,
1518          * false is returned.
1519          *
1520          * @param string|array $table Table name
1521          * @param string|array $vars Field names
1522          * @param array $conds Conditions
1523          * @param string $fname Caller function name
1524          * @param string|array $options Query options
1525          * @param $join_conds array|string Join conditions
1526          *
1527          * @return object|bool
1528          */
1529         public function selectRow( $table, $vars, $conds, $fname = 'DatabaseBase::selectRow',
1530                 $options = array(), $join_conds = array() )
1531         {
1532                 $options = (array)$options;
1533                 $options['LIMIT'] = 1;
1534                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1535
1536                 if ( $res === false ) {
1537                         return false;
1538                 }
1539
1540                 if ( !$this->numRows( $res ) ) {
1541                         return false;
1542                 }
1543
1544                 $obj = $this->fetchObject( $res );
1545
1546                 return $obj;
1547         }
1548
1549         /**
1550          * Estimate rows in dataset.
1551          *
1552          * MySQL allows you to estimate the number of rows that would be returned
1553          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1554          * index cardinality statistics, and is notoriously inaccurate, especially
1555          * when large numbers of rows have recently been added or deleted.
1556          *
1557          * For DBMSs that don't support fast result size estimation, this function
1558          * will actually perform the SELECT COUNT(*).
1559          *
1560          * Takes the same arguments as DatabaseBase::select().
1561          *
1562          * @param string $table table name
1563          * @param array|string $vars : unused
1564          * @param array|string $conds : filters on the table
1565          * @param string $fname function name for profiling
1566          * @param array $options options for select
1567          * @return Integer: row count
1568          */
1569         public function estimateRowCount( $table, $vars = '*', $conds = '',
1570                 $fname = 'DatabaseBase::estimateRowCount', $options = array() )
1571         {
1572                 $rows = 0;
1573                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1574
1575                 if ( $res ) {
1576                         $row = $this->fetchRow( $res );
1577                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1578                 }
1579
1580                 return $rows;
1581         }
1582
1583         /**
1584          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1585          * It's only slightly flawed. Don't use for anything important.
1586          *
1587          * @param string $sql A SQL Query
1588          *
1589          * @return string
1590          */
1591         static function generalizeSQL( $sql ) {
1592                 # This does the same as the regexp below would do, but in such a way
1593                 # as to avoid crashing php on some large strings.
1594                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1595
1596                 $sql = str_replace( "\\\\", '', $sql );
1597                 $sql = str_replace( "\\'", '', $sql );
1598                 $sql = str_replace( "\\\"", '', $sql );
1599                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1600                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1601
1602                 # All newlines, tabs, etc replaced by single space
1603                 $sql = preg_replace( '/\s+/', ' ', $sql );
1604
1605                 # All numbers => N
1606                 $sql = preg_replace( '/-?[0-9]+/s', 'N', $sql );
1607
1608                 return $sql;
1609         }
1610
1611         /**
1612          * Determines whether a field exists in a table
1613          *
1614          * @param string $table table name
1615          * @param string $field filed to check on that table
1616          * @param string $fname calling function name (optional)
1617          * @return Boolean: whether $table has filed $field
1618          */
1619         public function fieldExists( $table, $field, $fname = 'DatabaseBase::fieldExists' ) {
1620                 $info = $this->fieldInfo( $table, $field );
1621
1622                 return (bool)$info;
1623         }
1624
1625         /**
1626          * Determines whether an index exists
1627          * Usually throws a DBQueryError on failure
1628          * If errors are explicitly ignored, returns NULL on failure
1629          *
1630          * @param $table
1631          * @param $index
1632          * @param $fname string
1633          *
1634          * @return bool|null
1635          */
1636         public function indexExists( $table, $index, $fname = 'DatabaseBase::indexExists' ) {
1637                 if( !$this->tableExists( $table ) ) {
1638                         return null;
1639                 }
1640
1641                 $info = $this->indexInfo( $table, $index, $fname );
1642                 if ( is_null( $info ) ) {
1643                         return null;
1644                 } else {
1645                         return $info !== false;
1646                 }
1647         }
1648
1649         /**
1650          * Query whether a given table exists
1651          *
1652          * @param $table string
1653          * @param $fname string
1654          *
1655          * @return bool
1656          */
1657         public function tableExists( $table, $fname = __METHOD__ ) {
1658                 $table = $this->tableName( $table );
1659                 $old = $this->ignoreErrors( true );
1660                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1661                 $this->ignoreErrors( $old );
1662
1663                 return (bool)$res;
1664         }
1665
1666         /**
1667          * mysql_field_type() wrapper
1668          * @param $res
1669          * @param $index
1670          * @return string
1671          */
1672         public function fieldType( $res, $index ) {
1673                 if ( $res instanceof ResultWrapper ) {
1674                         $res = $res->result;
1675                 }
1676
1677                 return mysql_field_type( $res, $index );
1678         }
1679
1680         /**
1681          * Determines if a given index is unique
1682          *
1683          * @param $table string
1684          * @param $index string
1685          *
1686          * @return bool
1687          */
1688         public function indexUnique( $table, $index ) {
1689                 $indexInfo = $this->indexInfo( $table, $index );
1690
1691                 if ( !$indexInfo ) {
1692                         return null;
1693                 }
1694
1695                 return !$indexInfo[0]->Non_unique;
1696         }
1697
1698         /**
1699          * Helper for DatabaseBase::insert().
1700          *
1701          * @param $options array
1702          * @return string
1703          */
1704         protected function makeInsertOptions( $options ) {
1705                 return implode( ' ', $options );
1706         }
1707
1708         /**
1709          * INSERT wrapper, inserts an array into a table.
1710          *
1711          * $a may be either:
1712          *
1713          *   - A single associative array. The array keys are the field names, and
1714          *     the values are the values to insert. The values are treated as data
1715          *     and will be quoted appropriately. If NULL is inserted, this will be
1716          *     converted to a database NULL.
1717          *   - An array with numeric keys, holding a list of associative arrays.
1718          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1719          *     each subarray must be identical to each other, and in the same order.
1720          *
1721          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1722          * returns success.
1723          *
1724          * $options is an array of options, with boolean options encoded as values
1725          * with numeric keys, in the same style as $options in
1726          * DatabaseBase::select(). Supported options are:
1727          *
1728          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1729          *     any rows which cause duplicate key errors are not inserted. It's
1730          *     possible to determine how many rows were successfully inserted using
1731          *     DatabaseBase::affectedRows().
1732          *
1733          * @param $table   String Table name. This will be passed through
1734          *                 DatabaseBase::tableName().
1735          * @param $a       Array of rows to insert
1736          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1737          * @param array $options of options
1738          *
1739          * @return bool
1740          */
1741         public function insert( $table, $a, $fname = 'DatabaseBase::insert', $options = array() ) {
1742                 # No rows to insert, easy just return now
1743                 if ( !count( $a ) ) {
1744                         return true;
1745                 }
1746
1747                 $table = $this->tableName( $table );
1748
1749                 if ( !is_array( $options ) ) {
1750                         $options = array( $options );
1751                 }
1752
1753                 $fh = null;
1754                 if ( isset( $options['fileHandle'] ) ) {
1755                         $fh = $options['fileHandle'];
1756                 }
1757                 $options = $this->makeInsertOptions( $options );
1758
1759                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1760                         $multi = true;
1761                         $keys = array_keys( $a[0] );
1762                 } else {
1763                         $multi = false;
1764                         $keys = array_keys( $a );
1765                 }
1766
1767                 $sql = 'INSERT ' . $options .
1768                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1769
1770                 if ( $multi ) {
1771                         $first = true;
1772                         foreach ( $a as $row ) {
1773                                 if ( $first ) {
1774                                         $first = false;
1775                                 } else {
1776                                         $sql .= ',';
1777                                 }
1778                                 $sql .= '(' . $this->makeList( $row ) . ')';
1779                         }
1780                 } else {
1781                         $sql .= '(' . $this->makeList( $a ) . ')';
1782                 }
1783
1784                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1785                         return false;
1786                 } elseif ( $fh !== null ) {
1787                         return true;
1788                 }
1789
1790                 return (bool)$this->query( $sql, $fname );
1791         }
1792
1793         /**
1794          * Make UPDATE options for the DatabaseBase::update function
1795          *
1796          * @param array $options The options passed to DatabaseBase::update
1797          * @return string
1798          */
1799         protected function makeUpdateOptions( $options ) {
1800                 if ( !is_array( $options ) ) {
1801                         $options = array( $options );
1802                 }
1803
1804                 $opts = array();
1805
1806                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1807                         $opts[] = $this->lowPriorityOption();
1808                 }
1809
1810                 if ( in_array( 'IGNORE', $options ) ) {
1811                         $opts[] = 'IGNORE';
1812                 }
1813
1814                 return implode( ' ', $opts );
1815         }
1816
1817         /**
1818          * UPDATE wrapper. Takes a condition array and a SET array.
1819          *
1820          * @param $table  String name of the table to UPDATE. This will be passed through
1821          *                DatabaseBase::tableName().
1822          *
1823          * @param array $values  An array of values to SET. For each array element,
1824          *                the key gives the field name, and the value gives the data
1825          *                to set that field to. The data will be quoted by
1826          *                DatabaseBase::addQuotes().
1827          *
1828          * @param $conds  Array:  An array of conditions (WHERE). See
1829          *                DatabaseBase::select() for the details of the format of
1830          *                condition arrays. Use '*' to update all rows.
1831          *
1832          * @param $fname  String: The function name of the caller (from __METHOD__),
1833          *                for logging and profiling.
1834          *
1835          * @param array $options An array of UPDATE options, can be:
1836          *                   - IGNORE: Ignore unique key conflicts
1837          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1838          * @return Boolean
1839          */
1840         function update( $table, $values, $conds, $fname = 'DatabaseBase::update', $options = array() ) {
1841                 $table = $this->tableName( $table );
1842                 $opts = $this->makeUpdateOptions( $options );
1843                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1844
1845                 if ( $conds !== array() && $conds !== '*' ) {
1846                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1847                 }
1848
1849                 return $this->query( $sql, $fname );
1850         }
1851
1852         /**
1853          * Makes an encoded list of strings from an array
1854          * @param array $a containing the data
1855          * @param int $mode Constant
1856          *      - LIST_COMMA:          comma separated, no field names
1857          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1858          *        the documentation for $conds in DatabaseBase::select().
1859          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1860          *      - LIST_SET:            comma separated with field names, like a SET clause
1861          *      - LIST_NAMES:          comma separated field names
1862          *
1863          * @throws MWException|DBUnexpectedError
1864          * @return string
1865          */
1866         public function makeList( $a, $mode = LIST_COMMA ) {
1867                 if ( !is_array( $a ) ) {
1868                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1869                 }
1870
1871                 $first = true;
1872                 $list = '';
1873
1874                 foreach ( $a as $field => $value ) {
1875                         if ( !$first ) {
1876                                 if ( $mode == LIST_AND ) {
1877                                         $list .= ' AND ';
1878                                 } elseif ( $mode == LIST_OR ) {
1879                                         $list .= ' OR ';
1880                                 } else {
1881                                         $list .= ',';
1882                                 }
1883                         } else {
1884                                 $first = false;
1885                         }
1886
1887                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1888                                 $list .= "($value)";
1889                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1890                                 $list .= "$value";
1891                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1892                                 if ( count( $value ) == 0 ) {
1893                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1894                                 } elseif ( count( $value ) == 1 ) {
1895                                         // Special-case single values, as IN isn't terribly efficient
1896                                         // Don't necessarily assume the single key is 0; we don't
1897                                         // enforce linear numeric ordering on other arrays here.
1898                                         $value = array_values( $value );
1899                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1900                                 } else {
1901                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1902                                 }
1903                         } elseif ( $value === null ) {
1904                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1905                                         $list .= "$field IS ";
1906                                 } elseif ( $mode == LIST_SET ) {
1907                                         $list .= "$field = ";
1908                                 }
1909                                 $list .= 'NULL';
1910                         } else {
1911                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1912                                         $list .= "$field = ";
1913                                 }
1914                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1915                         }
1916                 }
1917
1918                 return $list;
1919         }
1920
1921         /**
1922          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1923          * The keys on each level may be either integers or strings.
1924          *
1925          * @param array $data organized as 2-d
1926          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
1927          * @param string $baseKey field name to match the base-level keys to (eg 'pl_namespace')
1928          * @param string $subKey field name to match the sub-level keys to (eg 'pl_title')
1929          * @return Mixed: string SQL fragment, or false if no items in array.
1930          */
1931         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1932                 $conds = array();
1933
1934                 foreach ( $data as $base => $sub ) {
1935                         if ( count( $sub ) ) {
1936                                 $conds[] = $this->makeList(
1937                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1938                                         LIST_AND );
1939                         }
1940                 }
1941
1942                 if ( $conds ) {
1943                         return $this->makeList( $conds, LIST_OR );
1944                 } else {
1945                         // Nothing to search for...
1946                         return false;
1947                 }
1948         }
1949
1950         /**
1951          * Return aggregated value alias
1952          *
1953          * @param $valuedata
1954          * @param $valuename string
1955          *
1956          * @return string
1957          */
1958         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1959                 return $valuename;
1960         }
1961
1962         /**
1963          * @param $field
1964          * @return string
1965          */
1966         public function bitNot( $field ) {
1967                 return "(~$field)";
1968         }
1969
1970         /**
1971          * @param $fieldLeft
1972          * @param $fieldRight
1973          * @return string
1974          */
1975         public function bitAnd( $fieldLeft, $fieldRight ) {
1976                 return "($fieldLeft & $fieldRight)";
1977         }
1978
1979         /**
1980          * @param  $fieldLeft
1981          * @param  $fieldRight
1982          * @return string
1983          */
1984         public function bitOr( $fieldLeft, $fieldRight ) {
1985                 return "($fieldLeft | $fieldRight)";
1986         }
1987
1988         /**
1989          * Build a concatenation list to feed into a SQL query
1990          * @param array $stringList list of raw SQL expressions; caller is responsible for any quoting
1991          * @return String
1992          */
1993         public function buildConcat( $stringList ) {
1994                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1995         }
1996
1997         /**
1998          * Change the current database
1999          *
2000          * @todo Explain what exactly will fail if this is not overridden.
2001          *
2002          * @param $db
2003          *
2004          * @return bool Success or failure
2005          */
2006         public function selectDB( $db ) {
2007                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
2008                 # if your database engine supports a concept similar to MySQL's
2009                 # databases you may as well.
2010                 $this->mDBname = $db;
2011                 return true;
2012         }
2013
2014         /**
2015          * Get the current DB name
2016          */
2017         public function getDBname() {
2018                 return $this->mDBname;
2019         }
2020
2021         /**
2022          * Get the server hostname or IP address
2023          */
2024         public function getServer() {
2025                 return $this->mServer;
2026         }
2027
2028         /**
2029          * Format a table name ready for use in constructing an SQL query
2030          *
2031          * This does two important things: it quotes the table names to clean them up,
2032          * and it adds a table prefix if only given a table name with no quotes.
2033          *
2034          * All functions of this object which require a table name call this function
2035          * themselves. Pass the canonical name to such functions. This is only needed
2036          * when calling query() directly.
2037          *
2038          * @param string $name database table name
2039          * @param string $format One of:
2040          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2041          *            so that it can be used in a query.
2042          *   raw - Do not add identifier quotes to the table name
2043          * @return String: full database name
2044          */
2045         public function tableName( $name, $format = 'quoted' ) {
2046                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
2047                 # Skip the entire process when we have a string quoted on both ends.
2048                 # Note that we check the end so that we will still quote any use of
2049                 # use of `database`.table. But won't break things if someone wants
2050                 # to query a database table with a dot in the name.
2051                 if ( $this->isQuotedIdentifier( $name ) ) {
2052                         return $name;
2053                 }
2054
2055                 # Lets test for any bits of text that should never show up in a table
2056                 # name. Basically anything like JOIN or ON which are actually part of
2057                 # SQL queries, but may end up inside of the table value to combine
2058                 # sql. Such as how the API is doing.
2059                 # Note that we use a whitespace test rather than a \b test to avoid
2060                 # any remote case where a word like on may be inside of a table name
2061                 # surrounded by symbols which may be considered word breaks.
2062                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2063                         return $name;
2064                 }
2065
2066                 # Split database and table into proper variables.
2067                 # We reverse the explode so that database.table and table both output
2068                 # the correct table.
2069                 $dbDetails = explode( '.', $name, 2 );
2070                 if ( count( $dbDetails ) == 2 ) {
2071                         list( $database, $table ) = $dbDetails;
2072                         # We don't want any prefix added in this case
2073                         $prefix = '';
2074                 } else {
2075                         list( $table ) = $dbDetails;
2076                         if ( $wgSharedDB !== null # We have a shared database
2077                                 && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
2078                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2079                         ) {
2080                                 $database = $wgSharedDB;
2081                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2082                         } else {
2083                                 $database = null;
2084                                 $prefix = $this->mTablePrefix; # Default prefix
2085                         }
2086                 }
2087
2088                 # Quote $table and apply the prefix if not quoted.
2089                 $tableName = "{$prefix}{$table}";
2090                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) ) {
2091                         $tableName = $this->addIdentifierQuotes( $tableName );
2092                 }
2093
2094                 # Quote $database and merge it with the table name if needed
2095                 if ( $database !== null ) {
2096                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2097                                 $database = $this->addIdentifierQuotes( $database );
2098                         }
2099                         $tableName = $database . '.' . $tableName;
2100                 }
2101
2102                 return $tableName;
2103         }
2104
2105         /**
2106          * Fetch a number of table names into an array
2107          * This is handy when you need to construct SQL for joins
2108          *
2109          * Example:
2110          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2111          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2112          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2113          *
2114          * @return array
2115          */
2116         public function tableNames() {
2117                 $inArray = func_get_args();
2118                 $retVal = array();
2119
2120                 foreach ( $inArray as $name ) {
2121                         $retVal[$name] = $this->tableName( $name );
2122                 }
2123
2124                 return $retVal;
2125         }
2126
2127         /**
2128          * Fetch a number of table names into an zero-indexed numerical array
2129          * This is handy when you need to construct SQL for joins
2130          *
2131          * Example:
2132          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2133          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2134          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2135          *
2136          * @return array
2137          */
2138         public function tableNamesN() {
2139                 $inArray = func_get_args();
2140                 $retVal = array();
2141
2142                 foreach ( $inArray as $name ) {
2143                         $retVal[] = $this->tableName( $name );
2144                 }
2145
2146                 return $retVal;
2147         }
2148
2149         /**
2150          * Get an aliased table name
2151          * e.g. tableName AS newTableName
2152          *
2153          * @param string $name Table name, see tableName()
2154          * @param string|bool $alias Alias (optional)
2155          * @return string SQL name for aliased table. Will not alias a table to its own name
2156          */
2157         public function tableNameWithAlias( $name, $alias = false ) {
2158                 if ( !$alias || $alias == $name ) {
2159                         return $this->tableName( $name );
2160                 } else {
2161                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2162                 }
2163         }
2164
2165         /**
2166          * Gets an array of aliased table names
2167          *
2168          * @param $tables array( [alias] => table )
2169          * @return array of strings, see tableNameWithAlias()
2170          */
2171         public function tableNamesWithAlias( $tables ) {
2172                 $retval = array();
2173                 foreach ( $tables as $alias => $table ) {
2174                         if ( is_numeric( $alias ) ) {
2175                                 $alias = $table;
2176                         }
2177                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2178                 }
2179                 return $retval;
2180         }
2181
2182         /**
2183          * Get an aliased field name
2184          * e.g. fieldName AS newFieldName
2185          *
2186          * @param string $name Field name
2187          * @param string|bool $alias Alias (optional)
2188          * @return string SQL name for aliased field. Will not alias a field to its own name
2189          */
2190         public function fieldNameWithAlias( $name, $alias = false ) {
2191                 if ( !$alias || (string)$alias === (string)$name ) {
2192                         return $name;
2193                 } else {
2194                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2195                 }
2196         }
2197
2198         /**
2199          * Gets an array of aliased field names
2200          *
2201          * @param $fields array( [alias] => field )
2202          * @return array of strings, see fieldNameWithAlias()
2203          */
2204         public function fieldNamesWithAlias( $fields ) {
2205                 $retval = array();
2206                 foreach ( $fields as $alias => $field ) {
2207                         if ( is_numeric( $alias ) ) {
2208                                 $alias = $field;
2209                         }
2210                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2211                 }
2212                 return $retval;
2213         }
2214
2215         /**
2216          * Get the aliased table name clause for a FROM clause
2217          * which might have a JOIN and/or USE INDEX clause
2218          *
2219          * @param array $tables ( [alias] => table )
2220          * @param $use_index array Same as for select()
2221          * @param $join_conds array Same as for select()
2222          * @return string
2223          */
2224         protected function tableNamesWithUseIndexOrJOIN(
2225                 $tables, $use_index = array(), $join_conds = array()
2226         ) {
2227                 $ret = array();
2228                 $retJOIN = array();
2229                 $use_index = (array)$use_index;
2230                 $join_conds = (array)$join_conds;
2231
2232                 foreach ( $tables as $alias => $table ) {
2233                         if ( !is_string( $alias ) ) {
2234                                 // No alias? Set it equal to the table name
2235                                 $alias = $table;
2236                         }
2237                         // Is there a JOIN clause for this table?
2238                         if ( isset( $join_conds[$alias] ) ) {
2239                                 list( $joinType, $conds ) = $join_conds[$alias];
2240                                 $tableClause = $joinType;
2241                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2242                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2243                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2244                                         if ( $use != '' ) {
2245                                                 $tableClause .= ' ' . $use;
2246                                         }
2247                                 }
2248                                 $on = $this->makeList( (array)$conds, LIST_AND );
2249                                 if ( $on != '' ) {
2250                                         $tableClause .= ' ON (' . $on . ')';
2251                                 }
2252
2253                                 $retJOIN[] = $tableClause;
2254                         // Is there an INDEX clause for this table?
2255                         } elseif ( isset( $use_index[$alias] ) ) {
2256                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2257                                 $tableClause .= ' ' . $this->useIndexClause(
2258                                         implode( ',', (array)$use_index[$alias] ) );
2259
2260                                 $ret[] = $tableClause;
2261                         } else {
2262                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2263
2264                                 $ret[] = $tableClause;
2265                         }
2266                 }
2267
2268                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2269                 $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2270                 $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2271
2272                 // Compile our final table clause
2273                 return implode( ' ', array( $straightJoins, $otherJoins ) );
2274         }
2275
2276         /**
2277          * Get the name of an index in a given table
2278          *
2279          * @param $index
2280          *
2281          * @return string
2282          */
2283         protected function indexName( $index ) {
2284                 // Backwards-compatibility hack
2285                 $renamed = array(
2286                         'ar_usertext_timestamp' => 'usertext_timestamp',
2287                         'un_user_id'            => 'user_id',
2288                         'un_user_ip'            => 'user_ip',
2289                 );
2290
2291                 if ( isset( $renamed[$index] ) ) {
2292                         return $renamed[$index];
2293                 } else {
2294                         return $index;
2295                 }
2296         }
2297
2298         /**
2299          * If it's a string, adds quotes and backslashes
2300          * Otherwise returns as-is
2301          *
2302          * @param $s string
2303          *
2304          * @return string
2305          */
2306         public function addQuotes( $s ) {
2307                 if ( $s === null ) {
2308                         return 'NULL';
2309                 } else {
2310                         # This will also quote numeric values. This should be harmless,
2311                         # and protects against weird problems that occur when they really
2312                         # _are_ strings such as article titles and string->number->string
2313                         # conversion is not 1:1.
2314                         return "'" . $this->strencode( $s ) . "'";
2315                 }
2316         }
2317
2318         /**
2319          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2320          * MySQL uses `backticks` while basically everything else uses double quotes.
2321          * Since MySQL is the odd one out here the double quotes are our generic
2322          * and we implement backticks in DatabaseMysql.
2323          *
2324          * @param $s string
2325          *
2326          * @return string
2327          */
2328         public function addIdentifierQuotes( $s ) {
2329                 return '"' . str_replace( '"', '""', $s ) . '"';
2330         }
2331
2332         /**
2333          * Returns if the given identifier looks quoted or not according to
2334          * the database convention for quoting identifiers .
2335          *
2336          * @param $name string
2337          *
2338          * @return boolean
2339          */
2340         public function isQuotedIdentifier( $name ) {
2341                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2342         }
2343
2344         /**
2345          * @param $s string
2346          * @return string
2347          */
2348         protected function escapeLikeInternal( $s ) {
2349                 $s = str_replace( '\\', '\\\\', $s );
2350                 $s = $this->strencode( $s );
2351                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2352
2353                 return $s;
2354         }
2355
2356         /**
2357          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2358          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2359          * Alternatively, the function could be provided with an array of aforementioned parameters.
2360          *
2361          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2362          * for subpages of 'My page title'.
2363          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2364          *
2365          * @since 1.16
2366          * @return String: fully built LIKE statement
2367          */
2368         public function buildLike() {
2369                 $params = func_get_args();
2370
2371                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2372                         $params = $params[0];
2373                 }
2374
2375                 $s = '';
2376
2377                 foreach ( $params as $value ) {
2378                         if ( $value instanceof LikeMatch ) {
2379                                 $s .= $value->toString();
2380                         } else {
2381                                 $s .= $this->escapeLikeInternal( $value );
2382                         }
2383                 }
2384
2385                 return " LIKE '" . $s . "' ";
2386         }
2387
2388         /**
2389          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2390          *
2391          * @return LikeMatch
2392          */
2393         public function anyChar() {
2394                 return new LikeMatch( '_' );
2395         }
2396
2397         /**
2398          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2399          *
2400          * @return LikeMatch
2401          */
2402         public function anyString() {
2403                 return new LikeMatch( '%' );
2404         }
2405
2406         /**
2407          * Returns an appropriately quoted sequence value for inserting a new row.
2408          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2409          * subclass will return an integer, and save the value for insertId()
2410          *
2411          * Any implementation of this function should *not* involve reusing
2412          * sequence numbers created for rolled-back transactions.
2413          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2414          * @param $seqName string
2415          * @return null
2416          */
2417         public function nextSequenceValue( $seqName ) {
2418                 return null;
2419         }
2420
2421         /**
2422          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2423          * is only needed because a) MySQL must be as efficient as possible due to
2424          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2425          * which index to pick.  Anyway, other databases might have different
2426          * indexes on a given table.  So don't bother overriding this unless you're
2427          * MySQL.
2428          * @param $index
2429          * @return string
2430          */
2431         public function useIndexClause( $index ) {
2432                 return '';
2433         }
2434
2435         /**
2436          * REPLACE query wrapper.
2437          *
2438          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2439          * except that when there is a duplicate key error, the old row is deleted
2440          * and the new row is inserted in its place.
2441          *
2442          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2443          * perform the delete, we need to know what the unique indexes are so that
2444          * we know how to find the conflicting rows.
2445          *
2446          * It may be more efficient to leave off unique indexes which are unlikely
2447          * to collide. However if you do this, you run the risk of encountering
2448          * errors which wouldn't have occurred in MySQL.
2449          *
2450          * @param string $table The table to replace the row(s) in.
2451          * @param array $rows Can be either a single row to insert, or multiple rows,
2452          *    in the same format as for DatabaseBase::insert()
2453          * @param array $uniqueIndexes is an array of indexes. Each element may be either
2454          *    a field name or an array of field names
2455          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2456          */
2457         public function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseBase::replace' ) {
2458                 $quotedTable = $this->tableName( $table );
2459
2460                 if ( count( $rows ) == 0 ) {
2461                         return;
2462                 }
2463
2464                 # Single row case
2465                 if ( !is_array( reset( $rows ) ) ) {
2466                         $rows = array( $rows );
2467                 }
2468
2469                 foreach( $rows as $row ) {
2470                         # Delete rows which collide
2471                         if ( $uniqueIndexes ) {
2472                                 $sql = "DELETE FROM $quotedTable WHERE ";
2473                                 $first = true;
2474                                 foreach ( $uniqueIndexes as $index ) {
2475                                         if ( $first ) {
2476                                                 $first = false;
2477                                                 $sql .= '( ';
2478                                         } else {
2479                                                 $sql .= ' ) OR ( ';
2480                                         }
2481                                         if ( is_array( $index ) ) {
2482                                                 $first2 = true;
2483                                                 foreach ( $index as $col ) {
2484                                                         if ( $first2 ) {
2485                                                                 $first2 = false;
2486                                                         } else {
2487                                                                 $sql .= ' AND ';
2488                                                         }
2489                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2490                                                 }
2491                                         } else {
2492                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2493                                         }
2494                                 }
2495                                 $sql .= ' )';
2496                                 $this->query( $sql, $fname );
2497                         }
2498
2499                         # Now insert the row
2500                         $this->insert( $table, $row, $fname );
2501                 }
2502         }
2503
2504         /**
2505          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2506          * statement.
2507          *
2508          * @param string $table Table name
2509          * @param array $rows Rows to insert
2510          * @param string $fname Caller function name
2511          *
2512          * @return ResultWrapper
2513          */
2514         protected function nativeReplace( $table, $rows, $fname ) {
2515                 $table = $this->tableName( $table );
2516
2517                 # Single row case
2518                 if ( !is_array( reset( $rows ) ) ) {
2519                         $rows = array( $rows );
2520                 }
2521
2522                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2523                 $first = true;
2524
2525                 foreach ( $rows as $row ) {
2526                         if ( $first ) {
2527                                 $first = false;
2528                         } else {
2529                                 $sql .= ',';
2530                         }
2531
2532                         $sql .= '(' . $this->makeList( $row ) . ')';
2533                 }
2534
2535                 return $this->query( $sql, $fname );
2536         }
2537
2538         /**
2539          * DELETE where the condition is a join.
2540          *
2541          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2542          * we use sub-selects
2543          *
2544          * For safety, an empty $conds will not delete everything. If you want to
2545          * delete all rows where the join condition matches, set $conds='*'.
2546          *
2547          * DO NOT put the join condition in $conds.
2548          *
2549          * @param $delTable   String: The table to delete from.
2550          * @param $joinTable  String: The other table.
2551          * @param $delVar     String: The variable to join on, in the first table.
2552          * @param $joinVar    String: The variable to join on, in the second table.
2553          * @param $conds      Array: Condition array of field names mapped to variables,
2554          *                    ANDed together in the WHERE clause
2555          * @param $fname      String: Calling function name (use __METHOD__) for
2556          *                    logs/profiling
2557          * @throws DBUnexpectedError
2558          */
2559         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2560                 $fname = 'DatabaseBase::deleteJoin' )
2561         {
2562                 if ( !$conds ) {
2563                         throw new DBUnexpectedError( $this,
2564                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2565                 }
2566
2567                 $delTable = $this->tableName( $delTable );
2568                 $joinTable = $this->tableName( $joinTable );
2569                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2570                 if ( $conds != '*' ) {
2571                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2572                 }
2573                 $sql .= ')';
2574
2575                 $this->query( $sql, $fname );
2576         }
2577
2578         /**
2579          * Returns the size of a text field, or -1 for "unlimited"
2580          *
2581          * @param $table string
2582          * @param $field string
2583          *
2584          * @return int
2585          */
2586         public function textFieldSize( $table, $field ) {
2587                 $table = $this->tableName( $table );
2588                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2589                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2590                 $row = $this->fetchObject( $res );
2591
2592                 $m = array();
2593
2594                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2595                         $size = $m[1];
2596                 } else {
2597                         $size = -1;
2598                 }
2599
2600                 return $size;
2601         }
2602
2603         /**
2604          * A string to insert into queries to show that they're low-priority, like
2605          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2606          * string and nothing bad should happen.
2607          *
2608          * @return string Returns the text of the low priority option if it is
2609          *   supported, or a blank string otherwise
2610          */
2611         public function lowPriorityOption() {
2612                 return '';
2613         }
2614
2615         /**
2616          * DELETE query wrapper.
2617          *
2618          * @param array $table Table name
2619          * @param string|array $conds of conditions. See $conds in DatabaseBase::select() for
2620          *               the format. Use $conds == "*" to delete all rows
2621          * @param string $fname name of the calling function
2622          *
2623          * @throws DBUnexpectedError
2624          * @return bool|ResultWrapper
2625          */
2626         public function delete( $table, $conds, $fname = 'DatabaseBase::delete' ) {
2627                 if ( !$conds ) {
2628                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2629                 }
2630
2631                 $table = $this->tableName( $table );
2632                 $sql = "DELETE FROM $table";
2633
2634                 if ( $conds != '*' ) {
2635                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2636                 }
2637
2638                 return $this->query( $sql, $fname );
2639         }
2640
2641         /**
2642          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2643          * into another table.
2644          *
2645          * @param string $destTable The table name to insert into
2646          * @param string|array $srcTable May be either a table name, or an array of table names
2647          *    to include in a join.
2648          *
2649          * @param array $varMap must be an associative array of the form
2650          *    array( 'dest1' => 'source1', ...). Source items may be literals
2651          *    rather than field names, but strings should be quoted with
2652          *    DatabaseBase::addQuotes()
2653          *
2654          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2655          *    the details of the format of condition arrays. May be "*" to copy the
2656          *    whole table.
2657          *
2658          * @param string $fname The function name of the caller, from __METHOD__
2659          *
2660          * @param array $insertOptions Options for the INSERT part of the query, see
2661          *    DatabaseBase::insert() for details.
2662          * @param array $selectOptions Options for the SELECT part of the query, see
2663          *    DatabaseBase::select() for details.
2664          *
2665          * @return ResultWrapper
2666          */
2667         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2668                 $fname = 'DatabaseBase::insertSelect',
2669                 $insertOptions = array(), $selectOptions = array() )
2670         {
2671                 $destTable = $this->tableName( $destTable );
2672
2673                 if ( is_array( $insertOptions ) ) {
2674                         $insertOptions = implode( ' ', $insertOptions );
2675                 }
2676
2677                 if ( !is_array( $selectOptions ) ) {
2678                         $selectOptions = array( $selectOptions );
2679                 }
2680
2681                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2682
2683                 if ( is_array( $srcTable ) ) {
2684                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2685                 } else {
2686                         $srcTable = $this->tableName( $srcTable );
2687                 }
2688
2689                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2690                         " SELECT $startOpts " . implode( ',', $varMap ) .
2691                         " FROM $srcTable $useIndex ";
2692
2693                 if ( $conds != '*' ) {
2694                         if ( is_array( $conds ) ) {
2695                                 $conds = $this->makeList( $conds, LIST_AND );
2696                         }
2697                         $sql .= " WHERE $conds";
2698                 }
2699
2700                 $sql .= " $tailOpts";
2701
2702                 return $this->query( $sql, $fname );
2703         }
2704
2705         /**
2706          * Construct a LIMIT query with optional offset.  This is used for query
2707          * pages.  The SQL should be adjusted so that only the first $limit rows
2708          * are returned.  If $offset is provided as well, then the first $offset
2709          * rows should be discarded, and the next $limit rows should be returned.
2710          * If the result of the query is not ordered, then the rows to be returned
2711          * are theoretically arbitrary.
2712          *
2713          * $sql is expected to be a SELECT, if that makes a difference.
2714          *
2715          * The version provided by default works in MySQL and SQLite.  It will very
2716          * likely need to be overridden for most other DBMSes.
2717          *
2718          * @param string $sql SQL query we will append the limit too
2719          * @param $limit Integer the SQL limit
2720          * @param $offset Integer|bool the SQL offset (default false)
2721          *
2722          * @throws DBUnexpectedError
2723          * @return string
2724          */
2725         public function limitResult( $sql, $limit, $offset = false ) {
2726                 if ( !is_numeric( $limit ) ) {
2727                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2728                 }
2729                 return "$sql LIMIT "
2730                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2731                         . "{$limit} ";
2732         }
2733
2734         /**
2735          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2736          * within the UNION construct.
2737          * @return Boolean
2738          */
2739         public function unionSupportsOrderAndLimit() {
2740                 return true; // True for almost every DB supported
2741         }
2742
2743         /**
2744          * Construct a UNION query
2745          * This is used for providing overload point for other DB abstractions
2746          * not compatible with the MySQL syntax.
2747          * @param array $sqls SQL statements to combine
2748          * @param $all Boolean: use UNION ALL
2749          * @return String: SQL fragment
2750          */
2751         public function unionQueries( $sqls, $all ) {
2752                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2753                 return '(' . implode( $glue, $sqls ) . ')';
2754         }
2755
2756         /**
2757          * Returns an SQL expression for a simple conditional.  This doesn't need
2758          * to be overridden unless CASE isn't supported in your DBMS.
2759          *
2760          * @param string|array $cond SQL expression which will result in a boolean value
2761          * @param string $trueVal SQL expression to return if true
2762          * @param string $falseVal SQL expression to return if false
2763          * @return String: SQL fragment
2764          */
2765         public function conditional( $cond, $trueVal, $falseVal ) {
2766                 if ( is_array( $cond ) ) {
2767                         $cond = $this->makeList( $cond, LIST_AND );
2768                 }
2769                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2770         }
2771
2772         /**
2773          * Returns a comand for str_replace function in SQL query.
2774          * Uses REPLACE() in MySQL
2775          *
2776          * @param string $orig column to modify
2777          * @param string $old column to seek
2778          * @param string $new column to replace with
2779          *
2780          * @return string
2781          */
2782         public function strreplace( $orig, $old, $new ) {
2783                 return "REPLACE({$orig}, {$old}, {$new})";
2784         }
2785
2786         /**
2787          * Determines how long the server has been up
2788          * STUB
2789          *
2790          * @return int
2791          */
2792         public function getServerUptime() {
2793                 return 0;
2794         }
2795
2796         /**
2797          * Determines if the last failure was due to a deadlock
2798          * STUB
2799          *
2800          * @return bool
2801          */
2802         public function wasDeadlock() {
2803                 return false;
2804         }
2805
2806         /**
2807          * Determines if the last failure was due to a lock timeout
2808          * STUB
2809          *
2810          * @return bool
2811          */
2812         public function wasLockTimeout() {
2813                 return false;
2814         }
2815
2816         /**
2817          * Determines if the last query error was something that should be dealt
2818          * with by pinging the connection and reissuing the query.
2819          * STUB
2820          *
2821          * @return bool
2822          */
2823         public function wasErrorReissuable() {
2824                 return false;
2825         }
2826
2827         /**
2828          * Determines if the last failure was due to the database being read-only.
2829          * STUB
2830          *
2831          * @return bool
2832          */
2833         public function wasReadOnlyError() {
2834                 return false;
2835         }
2836
2837         /**
2838          * Perform a deadlock-prone transaction.
2839          *
2840          * This function invokes a callback function to perform a set of write
2841          * queries. If a deadlock occurs during the processing, the transaction
2842          * will be rolled back and the callback function will be called again.
2843          *
2844          * Usage:
2845          *   $dbw->deadlockLoop( callback, ... );
2846          *
2847          * Extra arguments are passed through to the specified callback function.
2848          *
2849          * Returns whatever the callback function returned on its successful,
2850          * iteration, or false on error, for example if the retry limit was
2851          * reached.
2852          *
2853          * @return bool
2854          */
2855         public function deadlockLoop() {
2856                 $this->begin( __METHOD__ );
2857                 $args = func_get_args();
2858                 $function = array_shift( $args );
2859                 $oldIgnore = $this->ignoreErrors( true );
2860                 $tries = DEADLOCK_TRIES;
2861
2862                 if ( is_array( $function ) ) {
2863                         $fname = $function[0];
2864                 } else {
2865                         $fname = $function;
2866                 }
2867
2868                 do {
2869                         $retVal = call_user_func_array( $function, $args );
2870                         $error = $this->lastError();
2871                         $errno = $this->lastErrno();
2872                         $sql = $this->lastQuery();
2873
2874                         if ( $errno ) {
2875                                 if ( $this->wasDeadlock() ) {
2876                                         # Retry
2877                                         usleep( mt_rand( DEADLOCK_DELAY_MIN, DEADLOCK_DELAY_MAX ) );
2878                                 } else {
2879                                         $this->reportQueryError( $error, $errno, $sql, $fname );
2880                                 }
2881                         }
2882                 } while ( $this->wasDeadlock() && --$tries > 0 );
2883
2884                 $this->ignoreErrors( $oldIgnore );
2885
2886                 if ( $tries <= 0 ) {
2887                         $this->rollback( __METHOD__ );
2888                         $this->reportQueryError( $error, $errno, $sql, $fname );
2889                         return false;
2890                 } else {
2891                         $this->commit( __METHOD__ );
2892                         return $retVal;
2893                 }
2894         }
2895
2896         /**
2897          * Wait for the slave to catch up to a given master position.
2898          *
2899          * @param $pos DBMasterPos object
2900          * @param $timeout Integer: the maximum number of seconds to wait for
2901          *   synchronisation
2902          *
2903          * @return integer: zero if the slave was past that position already,
2904          *   greater than zero if we waited for some period of time, less than
2905          *   zero if we timed out.
2906          */
2907         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2908                 wfProfileIn( __METHOD__ );
2909
2910                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2911                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
2912
2913                         if ( $wait > $timeout * 1e6 ) {
2914                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
2915                                 wfProfileOut( __METHOD__ );
2916                                 return -1;
2917                         } elseif ( $wait > 0 ) {
2918                                 wfDebug( "Fake slave waiting $wait us\n" );
2919                                 usleep( $wait );
2920                                 wfProfileOut( __METHOD__ );
2921                                 return 1;
2922                         } else {
2923                                 wfDebug( "Fake slave up to date ($wait us)\n" );
2924                                 wfProfileOut( __METHOD__ );
2925                                 return 0;
2926                         }
2927                 }
2928
2929                 wfProfileOut( __METHOD__ );
2930
2931                 # Real waits are implemented in the subclass.
2932                 return 0;
2933         }
2934
2935         /**
2936          * Get the replication position of this slave
2937          *
2938          * @return DBMasterPos, or false if this is not a slave.
2939          */
2940         public function getSlavePos() {
2941                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2942                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
2943                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
2944                         return $pos;
2945                 } else {
2946                         # Stub
2947                         return false;
2948                 }
2949         }
2950
2951         /**
2952          * Get the position of this master
2953          *
2954          * @return DBMasterPos, or false if this is not a master
2955          */
2956         public function getMasterPos() {
2957                 if ( $this->mFakeMaster ) {
2958                         return new MySQLMasterPos( 'fake', microtime( true ) );
2959                 } else {
2960                         return false;
2961                 }
2962         }
2963
2964         /**
2965          * Run an anonymous function as soon as there is no transaction pending.
2966          * If there is a transaction and it is rolled back, then the callback is cancelled.
2967          * Callbacks must commit any transactions that they begin.
2968          *
2969          * This is useful for updates to different systems or separate transactions are needed.
2970          *
2971          * @since 1.20
2972          *
2973          * @param Closure $callback
2974          */
2975         final public function onTransactionIdle( Closure $callback ) {
2976                 if ( $this->mTrxLevel ) {
2977                         $this->mTrxIdleCallbacks[] = $callback;
2978                 } else {
2979                         $callback();
2980                 }
2981         }
2982
2983         /**
2984          * Actually run the "on transaction idle" callbacks.
2985          *
2986          * @since 1.20
2987          */
2988         protected function runOnTransactionIdleCallbacks() {
2989                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
2990
2991                 $e = null; // last exception
2992                 do { // callbacks may add callbacks :)
2993                         $callbacks = $this->mTrxIdleCallbacks;
2994                         $this->mTrxIdleCallbacks = array(); // recursion guard
2995                         foreach ( $callbacks as $callback ) {
2996                                 try {
2997                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
2998                                         $callback();
2999                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3000                                 } catch ( Exception $e ) {
3001                                 }
3002                         }
3003                 } while ( count( $this->mTrxIdleCallbacks ) );
3004
3005                 if ( $e instanceof Exception ) {
3006                         throw $e; // re-throw any last exception
3007                 }
3008         }
3009
3010         /**
3011          * Begin a transaction. If a transaction is already in progress, that transaction will be committed before the
3012          * new transaction is started.
3013          *
3014          * Note that when the DBO_TRX flag is set (which is usually the case for web requests, but not for maintenance scripts),
3015          * any previous database query will have started a transaction automatically.
3016          *
3017          * Nesting of transactions is not supported. Attempts to nest transactions will cause a warning, unless the current
3018          * transaction was started automatically because of the DBO_TRX flag.
3019          *
3020          * @param $fname string
3021          */
3022         final public function begin( $fname = 'DatabaseBase::begin' ) {
3023                 global $wgDebugDBTransactions;
3024
3025                 if ( $this->mTrxLevel ) { // implicit commit
3026                         if ( !$this->mTrxAutomatic ) {
3027                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3028                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3029                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3030                                         " performing implicit commit!";
3031                                 wfWarn( $msg );
3032                                 wfLogDBError( $msg );
3033                         } else {
3034                                 // if the transaction was automatic and has done write operations,
3035                                 // log it if $wgDebugDBTransactions is enabled.
3036                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3037                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3038                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3039                                         );
3040                                 }
3041                         }
3042
3043                         $this->doCommit( $fname );
3044                         $this->runOnTransactionIdleCallbacks();
3045                 }
3046
3047                 $this->doBegin( $fname );
3048                 $this->mTrxFname = $fname;
3049                 $this->mTrxDoneWrites = false;
3050                 $this->mTrxAutomatic = false;
3051         }
3052
3053         /**
3054          * Issues the BEGIN command to the database server.
3055          *
3056          * @see DatabaseBase::begin()
3057          * @param type $fname
3058          */
3059         protected function doBegin( $fname ) {
3060                 $this->query( 'BEGIN', $fname );
3061                 $this->mTrxLevel = 1;
3062         }
3063
3064         /**
3065          * Commits a transaction previously started using begin().
3066          * If no transaction is in progress, a warning is issued.
3067          *
3068          * Nesting of transactions is not supported.
3069          *
3070          * @param $fname string
3071          * @param string $flush Flush flag, set to 'flush' to disable warnings about explicitly committing implicit
3072          *        transactions, or calling commit when no transaction is in progress.
3073          *        This will silently break any ongoing explicit transaction. Only set the flush flag if you are sure
3074          *        that it is safe to ignore these warnings in your context.
3075          */
3076         final public function commit( $fname = 'DatabaseBase::commit', $flush = '' ) {
3077                 if ( $flush != 'flush' ) {
3078                         if ( !$this->mTrxLevel ) {
3079                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3080                         } elseif( $this->mTrxAutomatic ) {
3081                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3082                         }
3083                 } else {
3084                         if ( !$this->mTrxLevel ) {
3085                                 return; // nothing to do
3086                         } elseif( !$this->mTrxAutomatic ) {
3087                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3088                         }
3089                 }
3090
3091                 $this->doCommit( $fname );
3092                 $this->runOnTransactionIdleCallbacks();
3093         }
3094
3095         /**
3096          * Issues the COMMIT command to the database server.
3097          *
3098          * @see DatabaseBase::commit()
3099          * @param type $fname
3100          */
3101         protected function doCommit( $fname ) {
3102                 if ( $this->mTrxLevel ) {
3103                         $this->query( 'COMMIT', $fname );
3104                         $this->mTrxLevel = 0;
3105                 }
3106         }
3107
3108         /**
3109          * Rollback a transaction previously started using begin().
3110          * If no transaction is in progress, a warning is issued.
3111          *
3112          * No-op on non-transactional databases.
3113          *
3114          * @param $fname string
3115          */
3116         final public function rollback( $fname = 'DatabaseBase::rollback' ) {
3117                 if ( !$this->mTrxLevel ) {
3118                         wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3119                 }
3120                 $this->doRollback( $fname );
3121                 $this->mTrxIdleCallbacks = array(); // cancel
3122         }
3123
3124         /**
3125          * Issues the ROLLBACK command to the database server.
3126          *
3127          * @see DatabaseBase::rollback()
3128          * @param type $fname
3129          */
3130         protected function doRollback( $fname ) {
3131                 if ( $this->mTrxLevel ) {
3132                         $this->query( 'ROLLBACK', $fname, true );
3133                         $this->mTrxLevel = 0;
3134                 }
3135         }
3136
3137         /**
3138          * Creates a new table with structure copied from existing table
3139          * Note that unlike most database abstraction functions, this function does not
3140          * automatically append database prefix, because it works at a lower
3141          * abstraction level.
3142          * The table names passed to this function shall not be quoted (this
3143          * function calls addIdentifierQuotes when needed).
3144          *
3145          * @param string $oldName name of table whose structure should be copied
3146          * @param string $newName name of table to be created
3147          * @param $temporary Boolean: whether the new table should be temporary
3148          * @param string $fname calling function name
3149          * @throws MWException
3150          * @return Boolean: true if operation was successful
3151          */
3152         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3153                 $fname = 'DatabaseBase::duplicateTableStructure'
3154         ) {
3155                 throw new MWException(
3156                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3157         }
3158
3159         /**
3160          * List all tables on the database
3161          *
3162          * @param string $prefix Only show tables with this prefix, e.g. mw_
3163          * @param string $fname calling function name
3164          * @throws MWException
3165          */
3166         function listTables( $prefix = null, $fname = 'DatabaseBase::listTables' ) {
3167                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3168         }
3169
3170         /**
3171          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3172          * to the format used for inserting into timestamp fields in this DBMS.
3173          *
3174          * The result is unquoted, and needs to be passed through addQuotes()
3175          * before it can be included in raw SQL.
3176          *
3177          * @param $ts string|int
3178          *
3179          * @return string
3180          */
3181         public function timestamp( $ts = 0 ) {
3182                 return wfTimestamp( TS_MW, $ts );
3183         }
3184
3185         /**
3186          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3187          * to the format used for inserting into timestamp fields in this DBMS. If
3188          * NULL is input, it is passed through, allowing NULL values to be inserted
3189          * into timestamp fields.
3190          *
3191          * The result is unquoted, and needs to be passed through addQuotes()
3192          * before it can be included in raw SQL.
3193          *
3194          * @param $ts string|int
3195          *
3196          * @return string
3197          */
3198         public function timestampOrNull( $ts = null ) {
3199                 if ( is_null( $ts ) ) {
3200                         return null;
3201                 } else {
3202                         return $this->timestamp( $ts );
3203                 }
3204         }
3205
3206         /**
3207          * Take the result from a query, and wrap it in a ResultWrapper if
3208          * necessary. Boolean values are passed through as is, to indicate success
3209          * of write queries or failure.
3210          *
3211          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3212          * resource, and it was necessary to call this function to convert it to
3213          * a wrapper. Nowadays, raw database objects are never exposed to external
3214          * callers, so this is unnecessary in external code. For compatibility with
3215          * old code, ResultWrapper objects are passed through unaltered.
3216          *
3217          * @param $result bool|ResultWrapper
3218          *
3219          * @return bool|ResultWrapper
3220          */
3221         public function resultObject( $result ) {
3222                 if ( empty( $result ) ) {
3223                         return false;
3224                 } elseif ( $result instanceof ResultWrapper ) {
3225                         return $result;
3226                 } elseif ( $result === true ) {
3227                         // Successful write query
3228                         return $result;
3229                 } else {
3230                         return new ResultWrapper( $this, $result );
3231                 }
3232         }
3233
3234         /**
3235          * Ping the server and try to reconnect if it there is no connection
3236          *
3237          * @return bool Success or failure
3238          */
3239         public function ping() {
3240                 # Stub.  Not essential to override.
3241                 return true;
3242         }
3243
3244         /**
3245          * Get slave lag. Currently supported only by MySQL.
3246          *
3247          * Note that this function will generate a fatal error on many
3248          * installations. Most callers should use LoadBalancer::safeGetLag()
3249          * instead.
3250          *
3251          * @return int Database replication lag in seconds
3252          */
3253         public function getLag() {
3254                 return intval( $this->mFakeSlaveLag );
3255         }
3256
3257         /**
3258          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3259          *
3260          * @return int
3261          */
3262         function maxListLen() {
3263                 return 0;
3264         }
3265
3266         /**
3267          * Some DBMSs have a special format for inserting into blob fields, they
3268          * don't allow simple quoted strings to be inserted. To insert into such
3269          * a field, pass the data through this function before passing it to
3270          * DatabaseBase::insert().
3271          * @param $b string
3272          * @return string
3273          */
3274         public function encodeBlob( $b ) {
3275                 return $b;
3276         }
3277
3278         /**
3279          * Some DBMSs return a special placeholder object representing blob fields
3280          * in result objects. Pass the object through this function to return the
3281          * original string.
3282          * @param $b string
3283          * @return string
3284          */
3285         public function decodeBlob( $b ) {
3286                 return $b;
3287         }
3288
3289         /**
3290          * Override database's default behavior. $options include:
3291          *     'connTimeout' : Set the connection timeout value in seconds.
3292          *                     May be useful for very long batch queries such as
3293          *                     full-wiki dumps, where a single query reads out over
3294          *                     hours or days.
3295          *
3296          * @param $options Array
3297          * @return void
3298          */
3299         public function setSessionOptions( array $options ) {
3300         }
3301
3302         /**
3303          * Read and execute SQL commands from a file.
3304          *
3305          * Returns true on success, error string or exception on failure (depending
3306          * on object's error ignore settings).
3307          *
3308          * @param string $filename File name to open
3309          * @param bool|callable $lineCallback Optional function called before reading each line
3310          * @param bool|callable $resultCallback Optional function called for each MySQL result
3311          * @param bool|string $fname Calling function name or false if name should be
3312          *      generated dynamically using $filename
3313          * @param bool|callable $inputCallback Callback: Optional function called for each complete line sent
3314          * @throws MWException
3315          * @throws Exception|MWException
3316          * @return bool|string
3317          */
3318         public function sourceFile(
3319                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3320         ) {
3321                 wfSuppressWarnings();
3322                 $fp = fopen( $filename, 'r' );
3323                 wfRestoreWarnings();
3324
3325                 if ( false === $fp ) {
3326                         throw new MWException( "Could not open \"{$filename}\".\n" );
3327                 }
3328
3329                 if ( !$fname ) {
3330                         $fname = __METHOD__ . "( $filename )";
3331                 }
3332
3333                 try {
3334                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3335                 }
3336                 catch ( MWException $e ) {
3337                         fclose( $fp );
3338                         throw $e;
3339                 }
3340
3341                 fclose( $fp );
3342
3343                 return $error;
3344         }
3345
3346         /**
3347          * Get the full path of a patch file. Originally based on archive()
3348          * from updaters.inc. Keep in mind this always returns a patch, as
3349          * it fails back to MySQL if no DB-specific patch can be found
3350          *
3351          * @param string $patch The name of the patch, like patch-something.sql
3352          * @return String Full path to patch file
3353          */
3354         public function patchPath( $patch ) {
3355                 global $IP;
3356
3357                 $dbType = $this->getType();
3358                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3359                         return "$IP/maintenance/$dbType/archives/$patch";
3360                 } else {
3361                         return "$IP/maintenance/archives/$patch";
3362                 }
3363         }
3364
3365         /**
3366          * Set variables to be used in sourceFile/sourceStream, in preference to the
3367          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3368          * all. If it's set to false, $GLOBALS will be used.
3369          *
3370          * @param bool|array $vars mapping variable name to value.
3371          */
3372         public function setSchemaVars( $vars ) {
3373                 $this->mSchemaVars = $vars;
3374         }
3375
3376         /**
3377          * Read and execute commands from an open file handle.
3378          *
3379          * Returns true on success, error string or exception on failure (depending
3380          * on object's error ignore settings).
3381          *
3382          * @param $fp Resource: File handle
3383          * @param $lineCallback Callback: Optional function called before reading each query
3384          * @param $resultCallback Callback: Optional function called for each MySQL result
3385          * @param string $fname Calling function name
3386          * @param $inputCallback Callback: Optional function called for each complete query sent
3387          * @return bool|string
3388          */
3389         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3390                 $fname = 'DatabaseBase::sourceStream', $inputCallback = false )
3391         {
3392                 $cmd = '';
3393
3394                 while ( !feof( $fp ) ) {
3395                         if ( $lineCallback ) {
3396                                 call_user_func( $lineCallback );
3397                         }
3398
3399                         $line = trim( fgets( $fp ) );
3400
3401                         if ( $line == '' ) {
3402                                 continue;
3403                         }
3404
3405                         if ( '-' == $line[0] && '-' == $line[1] ) {
3406                                 continue;
3407                         }
3408
3409                         if ( $cmd != '' ) {
3410                                 $cmd .= ' ';
3411                         }
3412
3413                         $done = $this->streamStatementEnd( $cmd, $line );
3414
3415                         $cmd .= "$line\n";
3416
3417                         if ( $done || feof( $fp ) ) {
3418                                 $cmd = $this->replaceVars( $cmd );
3419
3420                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3421                                         $res = $this->query( $cmd, $fname );
3422
3423                                         if ( $resultCallback ) {
3424                                                 call_user_func( $resultCallback, $res, $this );
3425                                         }
3426
3427                                         if ( false === $res ) {
3428                                                 $err = $this->lastError();
3429                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3430                                         }
3431                                 }
3432                                 $cmd = '';
3433                         }
3434                 }
3435
3436                 return true;
3437         }
3438
3439         /**
3440          * Called by sourceStream() to check if we've reached a statement end
3441          *
3442          * @param string $sql SQL assembled so far
3443          * @param string $newLine New line about to be added to $sql
3444          * @return Bool Whether $newLine contains end of the statement
3445          */
3446         public function streamStatementEnd( &$sql, &$newLine ) {
3447                 if ( $this->delimiter ) {
3448                         $prev = $newLine;
3449                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3450                         if ( $newLine != $prev ) {
3451                                 return true;
3452                         }
3453                 }
3454                 return false;
3455         }
3456
3457         /**
3458          * Database independent variable replacement. Replaces a set of variables
3459          * in an SQL statement with their contents as given by $this->getSchemaVars().
3460          *
3461          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3462          *
3463          * - '{$var}' should be used for text and is passed through the database's
3464          *   addQuotes method.
3465          * - `{$var}` should be used for identifiers (eg: table and database names),
3466          *   it is passed through the database's addIdentifierQuotes method which
3467          *   can be overridden if the database uses something other than backticks.
3468          * - / *$var* / is just encoded, besides traditional table prefix and
3469          *   table options its use should be avoided.
3470          *
3471          * @param string $ins SQL statement to replace variables in
3472          * @return String The new SQL statement with variables replaced
3473          */
3474         protected function replaceSchemaVars( $ins ) {
3475                 $vars = $this->getSchemaVars();
3476                 foreach ( $vars as $var => $value ) {
3477                         // replace '{$var}'
3478                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3479                         // replace `{$var}`
3480                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3481                         // replace /*$var*/
3482                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3483                 }
3484                 return $ins;
3485         }
3486
3487         /**
3488          * Replace variables in sourced SQL
3489          *
3490          * @param $ins string
3491          *
3492          * @return string
3493          */
3494         protected function replaceVars( $ins ) {
3495                 $ins = $this->replaceSchemaVars( $ins );
3496
3497                 // Table prefixes
3498                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3499                         array( $this, 'tableNameCallback' ), $ins );
3500
3501                 // Index names
3502                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3503                         array( $this, 'indexNameCallback' ), $ins );
3504
3505                 return $ins;
3506         }
3507
3508         /**
3509          * Get schema variables. If none have been set via setSchemaVars(), then
3510          * use some defaults from the current object.
3511          *
3512          * @return array
3513          */
3514         protected function getSchemaVars() {
3515                 if ( $this->mSchemaVars ) {
3516                         return $this->mSchemaVars;
3517                 } else {
3518                         return $this->getDefaultSchemaVars();
3519                 }
3520         }
3521
3522         /**
3523          * Get schema variables to use if none have been set via setSchemaVars().
3524          *
3525          * Override this in derived classes to provide variables for tables.sql
3526          * and SQL patch files.
3527          *
3528          * @return array
3529          */
3530         protected function getDefaultSchemaVars() {
3531                 return array();
3532         }
3533
3534         /**
3535          * Table name callback
3536          *
3537          * @param $matches array
3538          *
3539          * @return string
3540          */
3541         protected function tableNameCallback( $matches ) {
3542                 return $this->tableName( $matches[1] );
3543         }
3544
3545         /**
3546          * Index name callback
3547          *
3548          * @param $matches array
3549          *
3550          * @return string
3551          */
3552         protected function indexNameCallback( $matches ) {
3553                 return $this->indexName( $matches[1] );
3554         }
3555
3556         /**
3557          * Check to see if a named lock is available. This is non-blocking.
3558          *
3559          * @param string $lockName name of lock to poll
3560          * @param string $method name of method calling us
3561          * @return Boolean
3562          * @since 1.20
3563          */
3564         public function lockIsFree( $lockName, $method ) {
3565                 return true;
3566         }
3567
3568         /**
3569          * Acquire a named lock
3570          *
3571          * Abstracted from Filestore::lock() so child classes can implement for
3572          * their own needs.
3573          *
3574          * @param string $lockName name of lock to aquire
3575          * @param string $method name of method calling us
3576          * @param $timeout Integer: timeout
3577          * @return Boolean
3578          */
3579         public function lock( $lockName, $method, $timeout = 5 ) {
3580                 return true;
3581         }
3582
3583         /**
3584          * Release a lock.
3585          *
3586          * @param string $lockName Name of lock to release
3587          * @param string $method Name of method calling us
3588          *
3589          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3590          * by this thread (in which case the lock is not released), and NULL if the named
3591          * lock did not exist
3592          */
3593         public function unlock( $lockName, $method ) {
3594                 return true;
3595         }
3596
3597         /**
3598          * Lock specific tables
3599          *
3600          * @param array $read of tables to lock for read access
3601          * @param array $write of tables to lock for write access
3602          * @param string $method name of caller
3603          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
3604          *
3605          * @return bool
3606          */
3607         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3608                 return true;
3609         }
3610
3611         /**
3612          * Unlock specific tables
3613          *
3614          * @param string $method the caller
3615          *
3616          * @return bool
3617          */
3618         public function unlockTables( $method ) {
3619                 return true;
3620         }
3621
3622         /**
3623          * Delete a table
3624          * @param $tableName string
3625          * @param $fName string
3626          * @return bool|ResultWrapper
3627          * @since 1.18
3628          */
3629         public function dropTable( $tableName, $fName = 'DatabaseBase::dropTable' ) {
3630                 if( !$this->tableExists( $tableName, $fName ) ) {
3631                         return false;
3632                 }
3633                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3634                 if( $this->cascadingDeletes() ) {
3635                         $sql .= " CASCADE";
3636                 }
3637                 return $this->query( $sql, $fName );
3638         }
3639
3640         /**
3641          * Get search engine class. All subclasses of this need to implement this
3642          * if they wish to use searching.
3643          *
3644          * @return String
3645          */
3646         public function getSearchEngine() {
3647                 return 'SearchEngineDummy';
3648         }
3649
3650         /**
3651          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3652          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3653          * because "i" sorts after all numbers.
3654          *
3655          * @return String
3656          */
3657         public function getInfinity() {
3658                 return 'infinity';
3659         }
3660
3661         /**
3662          * Encode an expiry time into the DBMS dependent format
3663          *
3664          * @param string $expiry timestamp for expiry, or the 'infinity' string
3665          * @return String
3666          */
3667         public function encodeExpiry( $expiry ) {
3668                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3669                         ? $this->getInfinity()
3670                         : $this->timestamp( $expiry );
3671         }
3672
3673         /**
3674          * Decode an expiry time into a DBMS independent format
3675          *
3676          * @param string $expiry DB timestamp field value for expiry
3677          * @param $format integer: TS_* constant, defaults to TS_MW
3678          * @return String
3679          */
3680         public function decodeExpiry( $expiry, $format = TS_MW ) {
3681                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3682                         ? 'infinity'
3683                         : wfTimestamp( $format, $expiry );
3684         }
3685
3686         /**
3687          * Allow or deny "big selects" for this session only. This is done by setting
3688          * the sql_big_selects session variable.
3689          *
3690          * This is a MySQL-specific feature.
3691          *
3692          * @param $value Mixed: true for allow, false for deny, or "default" to
3693          *   restore the initial value
3694          */
3695         public function setBigSelects( $value = true ) {
3696                 // no-op
3697         }
3698
3699         /**
3700          * @since 1.19
3701          */
3702         public function __toString() {
3703                 return (string)$this->mConn;
3704         }
3705
3706         public function __destruct() {
3707                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
3708                         trigger_error( "Transaction idle callbacks still pending." );
3709                 }
3710         }
3711 }