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 /**
  28  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  29  * following must be implemented to support MediaWiki
  30  *
  31  * @file
  32  * @ingroup Database
  33  */
  34 interface DatabaseType {
  35         /**
  36          * Get the type of the DBMS, as it appears in $wgDBtype.
  37          *
  38          * @return string
  39          */
  40         function getType();
  41
  42         /**
  43          * Open a connection to the database. Usually aborts on failure
  44          *
  45          * @param string $server database server host
  46          * @param string $user database user name
  47          * @param string $password database user password
  48          * @param string $dbName database name
  49          * @return bool
  50          * @throws DBConnectionError
  51          */
  52         function open( $server, $user, $password, $dbName );
  53
  54         /**
  55          * Fetch the next row from the given result object, in object form.
  56          * Fields can be retrieved with $row->fieldname, with fields acting like
  57          * member variables.
  58          * If no more rows are available, false is returned.
  59          *
  60          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  61          * @return object|bool
  62          * @throws DBUnexpectedError Thrown if the database returns an error
  63          */
  64         function fetchObject( $res );
  65
  66         /**
  67          * Fetch the next row from the given result object, in associative array
  68          * form.  Fields are retrieved with $row['fieldname'].
  69          * If no more rows are available, false is returned.
  70          *
  71          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  72          * @return array|bool
  73          * @throws DBUnexpectedError Thrown if the database returns an error
  74          */
  75         function fetchRow( $res );
  76
  77         /**
  78          * Get the number of rows in a result object
  79          *
  80          * @param $res Mixed: A SQL result
  81          * @return int
  82          */
  83         function numRows( $res );
  84
  85         /**
  86          * Get the number of fields in a result object
  87          * @see http://www.php.net/mysql_num_fields
  88          *
  89          * @param $res Mixed: A SQL result
  90          * @return int
  91          */
  92         function numFields( $res );
  93
  94         /**
  95          * Get a field name in a result object
  96          * @see http://www.php.net/mysql_field_name
  97          *
  98          * @param $res Mixed: A SQL result
  99          * @param $n Integer
 100          * @return string
 101          */
 102         function fieldName( $res, $n );
 103
 104         /**
 105          * Get the inserted value of an auto-increment row
 106          *
 107          * The value inserted should be fetched from nextSequenceValue()
 108          *
 109          * Example:
 110          * $id = $dbw->nextSequenceValue( 'page_page_id_seq' );
 111          * $dbw->insert( 'page', array( 'page_id' => $id ) );
 112          * $id = $dbw->insertId();
 113          *
 114          * @return int
 115          */
 116         function insertId();
 117
 118         /**
 119          * Change the position of the cursor in a result object
 120          * @see http://www.php.net/mysql_data_seek
 121          *
 122          * @param $res Mixed: A SQL result
 123          * @param $row Mixed: Either MySQL row or ResultWrapper
 124          */
 125         function dataSeek( $res, $row );
 126
 127         /**
 128          * Get the last error number
 129          * @see http://www.php.net/mysql_errno
 130          *
 131          * @return int
 132          */
 133         function lastErrno();
 134
 135         /**
 136          * Get a description of the last error
 137          * @see http://www.php.net/mysql_error
 138          *
 139          * @return string
 140          */
 141         function lastError();
 142
 143         /**
 144          * mysql_fetch_field() wrapper
 145          * Returns false if the field doesn't exist
 146          *
 147          * @param string $table table name
 148          * @param string $field field name
 149          *
 150          * @return Field
 151          */
 152         function fieldInfo( $table, $field );
 153
 154         /**
 155          * Get information about an index into an object
 156          * @param string $table Table name
 157          * @param string $index Index name
 158          * @param string $fname Calling function name
 159          * @return Mixed: Database-specific index description class or false if the index does not exist
 160          */
 161         function indexInfo( $table, $index, $fname = __METHOD__ );
 162
 163         /**
 164          * Get the number of rows affected by the last write query
 165          * @see http://www.php.net/mysql_affected_rows
 166          *
 167          * @return int
 168          */
 169         function affectedRows();
 170
 171         /**
 172          * Wrapper for addslashes()
 173          *
 174          * @param string $s to be slashed.
 175          * @return string: slashed string.
 176          */
 177         function strencode( $s );
 178
 179         /**
 180          * Returns a wikitext link to the DB's website, e.g.,
 181          *     return "[http://www.mysql.com/ MySQL]";
 182          * Should at least contain plain text, if for some reason
 183          * your database has no website.
 184          *
 185          * @return string: wikitext of a link to the server software's web site
 186          */
 187         function getSoftwareLink();
 188
 189         /**
 190          * A string describing the current software version, like from
 191          * mysql_get_server_info().
 192          *
 193          * @return string: Version information from the database server.
 194          */
 195         function getServerVersion();
 196
 197         /**
 198          * A string describing the current software version, and possibly
 199          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 200          * Use getServerVersion() to get machine-friendly information.
 201          *
 202          * @return string: Version information from the database server
 203          */
 204         function getServerInfo();
 205 }
 206
 207 /**
 208  * Interface for classes that implement or wrap DatabaseBase
 209  * @ingroup Database
 210  */
 211 interface IDatabase {}
 212
 213 /**
 214  * Database abstraction object
 215  * @ingroup Database
 216  */
 217 abstract class DatabaseBase implements IDatabase, DatabaseType {
 218         /** Number of times to re-try an operation in case of deadlock */
 219         const DEADLOCK_TRIES = 4;
 220         /** Minimum time to wait before retry, in microseconds */
 221         const DEADLOCK_DELAY_MIN = 500000;
 222         /** Maximum time to wait before retry */
 223         const DEADLOCK_DELAY_MAX = 1500000;
 224
 225 # ------------------------------------------------------------------------------
 226 # Variables
 227 # ------------------------------------------------------------------------------
 228
 229         protected $mLastQuery = '';
 230         protected $mDoneWrites = false;
 231         protected $mPHPError = false;
 232
 233         protected $mServer, $mUser, $mPassword, $mDBname;
 234
 235         protected $mConn = null;
 236         protected $mOpened = false;
 237
 238         /** @var callable[] */
 239         protected $mTrxIdleCallbacks = array();
 240         /** @var callable[] */
 241         protected $mTrxPreCommitCallbacks = array();
 242
 243         protected $mTablePrefix;
 244         protected $mFlags;
 245         protected $mForeign;
 246         protected $mTrxLevel = 0;
 247         protected $mErrorCount = 0;
 248         protected $mLBInfo = array();
 249         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 250         protected $mDefaultBigSelects = null;
 251         protected $mSchemaVars = false;
 252
 253         protected $preparedArgs;
 254
 255         protected $htmlErrors;
 256
 257         protected $delimiter = ';';
 258
 259         /**
 260          * Remembers the function name given for starting the most recent transaction via begin().
 261          * Used to provide additional context for error reporting.
 262          *
 263          * @var String
 264          * @see DatabaseBase::mTrxLevel
 265          */
 266         private $mTrxFname = null;
 267
 268         /**
 269          * Record if possible write queries were done in the last transaction started
 270          *
 271          * @var Bool
 272          * @see DatabaseBase::mTrxLevel
 273          */
 274         private $mTrxDoneWrites = false;
 275
 276         /**
 277          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 278          *
 279          * @var Bool
 280          * @see DatabaseBase::mTrxLevel
 281          */
 282         private $mTrxAutomatic = false;
 283
 284         /**
 285          * @since 1.21
 286          * @var file handle for upgrade
 287          */
 288         protected $fileHandle = null;
 289
 290 # ------------------------------------------------------------------------------
 291 # Accessors
 292 # ------------------------------------------------------------------------------
 293         # These optionally set a variable and return the previous state
 294
 295         /**
 296          * A string describing the current software version, and possibly
 297          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 298          * Use getServerVersion() to get machine-friendly information.
 299          *
 300          * @return string: Version information from the database server
 301          */
 302         public function getServerInfo() {
 303                 return $this->getServerVersion();
 304         }
 305
 306         /**
 307          * @return string: command delimiter used by this database engine
 308          */
 309         public function getDelimiter() {
 310                 return $this->delimiter;
 311         }
 312
 313         /**
 314          * Boolean, controls output of large amounts of debug information.
 315          * @param $debug bool|null
 316          *   - true to enable debugging
 317          *   - false to disable debugging
 318          *   - omitted or null to do nothing
 319          *
 320          * @return bool|null previous value of the flag
 321          */
 322         public function debug( $debug = null ) {
 323                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 324         }
 325
 326         /**
 327          * Turns buffering of SQL result sets on (true) or off (false). Default is
 328          * "on".
 329          *
 330          * Unbuffered queries are very troublesome in MySQL:
 331          *
 332          *   - If another query is executed while the first query is being read
 333          *     out, the first query is killed. This means you can't call normal
 334          *     MediaWiki functions while you are reading an unbuffered query result
 335          *     from a normal wfGetDB() connection.
 336          *
 337          *   - Unbuffered queries cause the MySQL server to use large amounts of
 338          *     memory and to hold broad locks which block other queries.
 339          *
 340          * If you want to limit client-side memory, it's almost always better to
 341          * split up queries into batches using a LIMIT clause than to switch off
 342          * buffering.
 343          *
 344          * @param $buffer null|bool
 345          *
 346          * @return null|bool The previous value of the flag
 347          */
 348         public function bufferResults( $buffer = null ) {
 349                 if ( is_null( $buffer ) ) {
 350                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 351                 } else {
 352                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 353                 }
 354         }
 355
 356         /**
 357          * Turns on (false) or off (true) the automatic generation and sending
 358          * of a "we're sorry, but there has been a database error" page on
 359          * database errors. Default is on (false). When turned off, the
 360          * code should use lastErrno() and lastError() to handle the
 361          * situation as appropriate.
 362          *
 363          * @param $ignoreErrors bool|null
 364          *
 365          * @return bool The previous value of the flag.
 366          */
 367         public function ignoreErrors( $ignoreErrors = null ) {
 368                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 369         }
 370
 371         /**
 372          * Gets or sets the current transaction level.
 373          *
 374          * Historically, transactions were allowed to be "nested". This is no
 375          * longer supported, so this function really only returns a boolean.
 376          *
 377          * @param int $level An integer (0 or 1), or omitted to leave it unchanged.
 378          * @return int The previous value
 379          */
 380         public function trxLevel( $level = null ) {
 381                 return wfSetVar( $this->mTrxLevel, $level );
 382         }
 383
 384         /**
 385          * Get/set the number of errors logged. Only useful when errors are ignored
 386          * @param int $count The count to set, or omitted to leave it unchanged.
 387          * @return int The error count
 388          */
 389         public function errorCount( $count = null ) {
 390                 return wfSetVar( $this->mErrorCount, $count );
 391         }
 392
 393         /**
 394          * Get/set the table prefix.
 395          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 396          * @return string The previous table prefix.
 397          */
 398         public function tablePrefix( $prefix = null ) {
 399                 return wfSetVar( $this->mTablePrefix, $prefix );
 400         }
 401
 402         /**
 403          * Set the filehandle to copy write statements to.
 404          *
 405          * @param $fh filehandle
 406          */
 407         public function setFileHandle( $fh ) {
 408                 $this->fileHandle = $fh;
 409         }
 410
 411         /**
 412          * Get properties passed down from the server info array of the load
 413          * balancer.
 414          *
 415          * @param string $name The entry of the info array to get, or null to get the
 416          *   whole array
 417          *
 418          * @return LoadBalancer|null
 419          */
 420         public function getLBInfo( $name = null ) {
 421                 if ( is_null( $name ) ) {
 422                         return $this->mLBInfo;
 423                 } else {
 424                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 425                                 return $this->mLBInfo[$name];
 426                         } else {
 427                                 return null;
 428                         }
 429                 }
 430         }
 431
 432         /**
 433          * Set the LB info array, or a member of it. If called with one parameter,
 434          * the LB info array is set to that parameter. If it is called with two
 435          * parameters, the member with the given name is set to the given value.
 436          *
 437          * @param $name
 438          * @param $value
 439          */
 440         public function setLBInfo( $name, $value = null ) {
 441                 if ( is_null( $value ) ) {
 442                         $this->mLBInfo = $name;
 443                 } else {
 444                         $this->mLBInfo[$name] = $value;
 445                 }
 446         }
 447
 448         /**
 449          * Set lag time in seconds for a fake slave
 450          *
 451          * @param $lag int
 452          */
 453         public function setFakeSlaveLag( $lag ) {
 454                 $this->mFakeSlaveLag = $lag;
 455         }
 456
 457         /**
 458          * Make this connection a fake master
 459          *
 460          * @param $enabled bool
 461          */
 462         public function setFakeMaster( $enabled = true ) {
 463                 $this->mFakeMaster = $enabled;
 464         }
 465
 466         /**
 467          * Returns true if this database supports (and uses) cascading deletes
 468          *
 469          * @return bool
 470          */
 471         public function cascadingDeletes() {
 472                 return false;
 473         }
 474
 475         /**
 476          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 477          *
 478          * @return bool
 479          */
 480         public function cleanupTriggers() {
 481                 return false;
 482         }
 483
 484         /**
 485          * Returns true if this database is strict about what can be put into an IP field.
 486          * Specifically, it uses a NULL value instead of an empty string.
 487          *
 488          * @return bool
 489          */
 490         public function strictIPs() {
 491                 return false;
 492         }
 493
 494         /**
 495          * Returns true if this database uses timestamps rather than integers
 496          *
 497          * @return bool
 498          */
 499         public function realTimestamps() {
 500                 return false;
 501         }
 502
 503         /**
 504          * Returns true if this database does an implicit sort when doing GROUP BY
 505          *
 506          * @return bool
 507          */
 508         public function implicitGroupby() {
 509                 return true;
 510         }
 511
 512         /**
 513          * Returns true if this database does an implicit order by when the column has an index
 514          * For example: SELECT page_title FROM page LIMIT 1
 515          *
 516          * @return bool
 517          */
 518         public function implicitOrderby() {
 519                 return true;
 520         }
 521
 522         /**
 523          * Returns true if this database can do a native search on IP columns
 524          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 525          *
 526          * @return bool
 527          */
 528         public function searchableIPs() {
 529                 return false;
 530         }
 531
 532         /**
 533          * Returns true if this database can use functional indexes
 534          *
 535          * @return bool
 536          */
 537         public function functionalIndexes() {
 538                 return false;
 539         }
 540
 541         /**
 542          * Return the last query that went through DatabaseBase::query()
 543          * @return String
 544          */
 545         public function lastQuery() {
 546                 return $this->mLastQuery;
 547         }
 548
 549         /**
 550          * Returns true if the connection may have been used for write queries.
 551          * Should return true if unsure.
 552          *
 553          * @return bool
 554          */
 555         public function doneWrites() {
 556                 return $this->mDoneWrites;
 557         }
 558
 559         /**
 560          * Returns true if there is a transaction open with possible write
 561          * queries or transaction pre-commit/idle callbacks waiting on it to finish.
 562          *
 563          * @return bool
 564          */
 565         public function writesOrCallbacksPending() {
 566                 return $this->mTrxLevel && (
 567                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 568                 );
 569         }
 570
 571         /**
 572          * Is a connection to the database open?
 573          * @return Boolean
 574          */
 575         public function isOpen() {
 576                 return $this->mOpened;
 577         }
 578
 579         /**
 580          * Set a flag for this connection
 581          *
 582          * @param $flag Integer: DBO_* constants from Defines.php:
 583          *   - DBO_DEBUG: output some debug info (same as debug())
 584          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 585          *   - DBO_IGNORE: ignore errors (same as ignoreErrors())
 586          *   - DBO_TRX: automatically start transactions
 587          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 588          *       and removes it in command line mode
 589          *   - DBO_PERSISTENT: use persistant database connection
 590          */
 591         public function setFlag( $flag ) {
 592                 global $wgDebugDBTransactions;
 593                 $this->mFlags |= $flag;
 594                 if ( ( $flag & DBO_TRX ) & $wgDebugDBTransactions ) {
 595                         wfDebug( "Implicit transactions are now  disabled.\n" );
 596                 }
 597         }
 598
 599         /**
 600          * Clear a flag for this connection
 601          *
 602          * @param $flag: same as setFlag()'s $flag param
 603          */
 604         public function clearFlag( $flag ) {
 605                 global $wgDebugDBTransactions;
 606                 $this->mFlags &= ~$flag;
 607                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 608                         wfDebug( "Implicit transactions are now disabled.\n" );
 609                 }
 610         }
 611
 612         /**
 613          * Returns a boolean whether the flag $flag is set for this connection
 614          *
 615          * @param $flag: same as setFlag()'s $flag param
 616          * @return Boolean
 617          */
 618         public function getFlag( $flag ) {
 619                 return !!( $this->mFlags & $flag );
 620         }
 621
 622         /**
 623          * General read-only accessor
 624          *
 625          * @param $name string
 626          *
 627          * @return string
 628          */
 629         public function getProperty( $name ) {
 630                 return $this->$name;
 631         }
 632
 633         /**
 634          * @return string
 635          */
 636         public function getWikiID() {
 637                 if ( $this->mTablePrefix ) {
 638                         return "{$this->mDBname}-{$this->mTablePrefix}";
 639                 } else {
 640                         return $this->mDBname;
 641                 }
 642         }
 643
 644         /**
 645          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 646          *
 647          * @return string
 648          */
 649         public function getSchemaPath() {
 650                 global $IP;
 651                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 652                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 653                 } else {
 654                         return "$IP/maintenance/tables.sql";
 655                 }
 656         }
 657
 658 # ------------------------------------------------------------------------------
 659 # Other functions
 660 # ------------------------------------------------------------------------------
 661
 662         /**
 663          * Constructor.
 664          * @param string $server database server host
 665          * @param string $user database user name
 666          * @param string $password database user password
 667          * @param string $dbName database name
 668          * @param $flags
 669          * @param string $tablePrefix database table prefixes. By default use the prefix gave in LocalSettings.php
 670          * @param bool $foreign disable some operations specific to local databases
 671          */
 672         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 673                 $flags = 0, $tablePrefix = 'get from global', $foreign = false
 674         ) {
 675                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 676
 677                 $this->mFlags = $flags;
 678
 679                 if ( $this->mFlags & DBO_DEFAULT ) {
 680                         if ( $wgCommandLineMode ) {
 681                                 $this->mFlags &= ~DBO_TRX;
 682                                 if ( $wgDebugDBTransactions ) {
 683                                         wfDebug( "Implicit transaction open disabled.\n" );
 684                                 }
 685                         } else {
 686                                 $this->mFlags |= DBO_TRX;
 687                                 if ( $wgDebugDBTransactions ) {
 688                                         wfDebug( "Implicit transaction open enabled.\n" );
 689                                 }
 690                         }
 691                 }
 692
 693                 /** Get the default table prefix*/
 694                 if ( $tablePrefix == 'get from global' ) {
 695                         $this->mTablePrefix = $wgDBprefix;
 696                 } else {
 697                         $this->mTablePrefix = $tablePrefix;
 698                 }
 699
 700                 $this->mForeign = $foreign;
 701
 702                 if ( $user ) {
 703                         $this->open( $server, $user, $password, $dbName );
 704                 }
 705         }
 706
 707         /**
 708          * Called by serialize. Throw an exception when DB connection is serialized.
 709          * This causes problems on some database engines because the connection is
 710          * not restored on unserialize.
 711          */
 712         public function __sleep() {
 713                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 714         }
 715
 716         /**
 717          * Given a DB type, construct the name of the appropriate child class of
 718          * DatabaseBase. This is designed to replace all of the manual stuff like:
 719          *      $class = 'Database' . ucfirst( strtolower( $type ) );
 720          * as well as validate against the canonical list of DB types we have
 721          *
 722          * This factory function is mostly useful for when you need to connect to a
 723          * database other than the MediaWiki default (such as for external auth,
 724          * an extension, et cetera). Do not use this to connect to the MediaWiki
 725          * database. Example uses in core:
 726          * @see LoadBalancer::reallyOpenConnection()
 727          * @see ForeignDBRepo::getMasterDB()
 728          * @see WebInstaller_DBConnect::execute()
 729          *
 730          * @since 1.18
 731          *
 732          * @param string $dbType A possible DB type
 733          * @param array $p An array of options to pass to the constructor.
 734          *    Valid options are: host, user, password, dbname, flags, tablePrefix
 735          * @return DatabaseBase subclass or null
 736          */
 737         final public static function factory( $dbType, $p = array() ) {
 738                 $canonicalDBTypes = array(
 739                         'mysql', 'postgres', 'sqlite', 'oracle', 'mssql'
 740                 );
 741                 $dbType = strtolower( $dbType );
 742                 $class = 'Database' . ucfirst( $dbType );
 743
 744                 if ( in_array( $dbType, $canonicalDBTypes ) || ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) ) {
 745                         return new $class(
 746                                 isset( $p['host'] ) ? $p['host'] : false,
 747                                 isset( $p['user'] ) ? $p['user'] : false,
 748                                 isset( $p['password'] ) ? $p['password'] : false,
 749                                 isset( $p['dbname'] ) ? $p['dbname'] : false,
 750                                 isset( $p['flags'] ) ? $p['flags'] : 0,
 751                                 isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global',
 752                                 isset( $p['foreign'] ) ? $p['foreign'] : false
 753                         );
 754                 } else {
 755                         return null;
 756                 }
 757         }
 758
 759         protected function installErrorHandler() {
 760                 $this->mPHPError = false;
 761                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 762                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 763         }
 764
 765         /**
 766          * @return bool|string
 767          */
 768         protected function restoreErrorHandler() {
 769                 restore_error_handler();
 770                 if ( $this->htmlErrors !== false ) {
 771                         ini_set( 'html_errors', $this->htmlErrors );
 772                 }
 773                 if ( $this->mPHPError ) {
 774                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 775                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 776                         return $error;
 777                 } else {
 778                         return false;
 779                 }
 780         }
 781
 782         /**
 783          * @param $errno
 784          * @param $errstr
 785          * @access private
 786          */
 787         public function connectionErrorHandler( $errno, $errstr ) {
 788                 $this->mPHPError = $errstr;
 789         }
 790
 791         /**
 792          * Closes a database connection.
 793          * if it is open : commits any open transactions
 794          *
 795          * @throws MWException
 796          * @return Bool operation success. true if already closed.
 797          */
 798         public function close() {
 799                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 800                         throw new MWException( "Transaction idle callbacks still pending." );
 801                 }
 802                 $this->mOpened = false;
 803                 if ( $this->mConn ) {
 804                         if ( $this->trxLevel() ) {
 805                                 if ( !$this->mTrxAutomatic ) {
 806                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 807                                                 " performing implicit commit before closing connection!" );
 808                                 }
 809
 810                                 $this->commit( __METHOD__, 'flush' );
 811                         }
 812
 813                         $ret = $this->closeConnection();
 814                         $this->mConn = false;
 815                         return $ret;
 816                 } else {
 817                         return true;
 818                 }
 819         }
 820
 821         /**
 822          * Closes underlying database connection
 823          * @since 1.20
 824          * @return bool: Whether connection was closed successfully
 825          */
 826         abstract protected function closeConnection();
 827
 828         /**
 829          * @param string $error fallback error message, used if none is given by DB
 830          * @throws DBConnectionError
 831          */
 832         function reportConnectionError( $error = 'Unknown error' ) {
 833                 $myError = $this->lastError();
 834                 if ( $myError ) {
 835                         $error = $myError;
 836                 }
 837
 838                 # New method
 839                 throw new DBConnectionError( $this, $error );
 840         }
 841
 842         /**
 843          * The DBMS-dependent part of query()
 844          *
 845          * @param  $sql String: SQL query.
 846          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 847          */
 848         abstract protected function doQuery( $sql );
 849
 850         /**
 851          * Determine whether a query writes to the DB.
 852          * Should return true if unsure.
 853          *
 854          * @param $sql string
 855          *
 856          * @return bool
 857          */
 858         public function isWriteQuery( $sql ) {
 859                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 860         }
 861
 862         /**
 863          * Run an SQL query and return the result. Normally throws a DBQueryError
 864          * on failure. If errors are ignored, returns false instead.
 865          *
 866          * In new code, the query wrappers select(), insert(), update(), delete(),
 867          * etc. should be used where possible, since they give much better DBMS
 868          * independence and automatically quote or validate user input in a variety
 869          * of contexts. This function is generally only useful for queries which are
 870          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 871          * as CREATE TABLE.
 872          *
 873          * However, the query wrappers themselves should call this function.
 874          *
 875          * @param  $sql        String: SQL query
 876          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 877          *     comment (you can use __METHOD__ or add some extra info)
 878          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 879          *     maybe best to catch the exception instead?
 880          * @throws MWException
 881          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 882          *     for a successful read query, or false on failure if $tempIgnore set
 883          */
 884         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 885                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 886                 if ( !Profiler::instance()->isStub() ) {
 887                         # generalizeSQL will probably cut down the query to reasonable
 888                         # logging size most of the time. The substr is really just a sanity check.
 889
 890                         if ( $isMaster ) {
 891                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 892                                 $totalProf = 'DatabaseBase::query-master';
 893                         } else {
 894                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 895                                 $totalProf = 'DatabaseBase::query';
 896                         }
 897
 898                         wfProfileIn( $totalProf );
 899                         wfProfileIn( $queryProf );
 900                 }
 901
 902                 $this->mLastQuery = $sql;
 903                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 904                         # Set a flag indicating that writes have been done
 905                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 906                         $this->mDoneWrites = true;
 907                 }
 908
 909                 # Add a comment for easy SHOW PROCESSLIST interpretation
 910                 global $wgUser;
 911                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 912                         $userName = $wgUser->getName();
 913                         if ( mb_strlen( $userName ) > 15 ) {
 914                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 915                         }
 916                         $userName = str_replace( '/', '', $userName );
 917                 } else {
 918                         $userName = '';
 919                 }
 920
 921                 // Add trace comment to the begin of the sql string, right after the operator.
 922                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 923                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 924
 925                 # If DBO_TRX is set, start a transaction
 926                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 927                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' )
 928                 {
 929                         # Avoid establishing transactions for SHOW and SET statements too -
 930                         # that would delay transaction initializations to once connection
 931                         # is really used by application
 932                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 933                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 934                                 global $wgDebugDBTransactions;
 935                                 if ( $wgDebugDBTransactions ) {
 936                                         wfDebug( "Implicit transaction start.\n" );
 937                                 }
 938                                 $this->begin( __METHOD__ . " ($fname)" );
 939                                 $this->mTrxAutomatic = true;
 940                         }
 941                 }
 942
 943                 # Keep track of whether the transaction has write queries pending
 944                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
 945                         $this->mTrxDoneWrites = true;
 946                         Profiler::instance()->transactionWritingIn( $this->mServer, $this->mDBname );
 947                 }
 948
 949                 if ( $this->debug() ) {
 950                         static $cnt = 0;
 951
 952                         $cnt++;
 953                         $sqlx = substr( $commentedSql, 0, 500 );
 954                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 955
 956                         $master = $isMaster ? 'master' : 'slave';
 957                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 958                 }
 959
 960                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 961
 962                 # Do the query and handle errors
 963                 $ret = $this->doQuery( $commentedSql );
 964
 965                 MWDebug::queryTime( $queryId );
 966
 967                 # Try reconnecting if the connection was lost
 968                 if ( false === $ret && $this->wasErrorReissuable() ) {
 969                         # Transaction is gone, like it or not
 970                         $this->mTrxLevel = 0;
 971                         $this->mTrxIdleCallbacks = array(); // cancel
 972                         $this->mTrxPreCommitCallbacks = array(); // cancel
 973                         wfDebug( "Connection lost, reconnecting...\n" );
 974
 975                         if ( $this->ping() ) {
 976                                 wfDebug( "Reconnected\n" );
 977                                 $sqlx = substr( $commentedSql, 0, 500 );
 978                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
 979                                 global $wgRequestTime;
 980                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
 981                                 if ( $elapsed < 300 ) {
 982                                         # Not a database error to lose a transaction after a minute or two
 983                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
 984                                 }
 985                                 $ret = $this->doQuery( $commentedSql );
 986                         } else {
 987                                 wfDebug( "Failed\n" );
 988                         }
 989                 }
 990
 991                 if ( false === $ret ) {
 992                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 993                 }
 994
 995                 if ( !Profiler::instance()->isStub() ) {
 996                         wfProfileOut( $queryProf );
 997                         wfProfileOut( $totalProf );
 998                 }
 999
1000                 return $this->resultObject( $ret );
1001         }
1002
1003         /**
1004          * Report a query error. Log the error, and if neither the object ignore
1005          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1006          *
1007          * @param $error String
1008          * @param $errno Integer
1009          * @param $sql String
1010          * @param $fname String
1011          * @param $tempIgnore Boolean
1012          * @throws DBQueryError
1013          */
1014         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1015                 # Ignore errors during error handling to avoid infinite recursion
1016                 $ignore = $this->ignoreErrors( true );
1017                 ++$this->mErrorCount;
1018
1019                 if ( $ignore || $tempIgnore ) {
1020                         wfDebug( "SQL ERROR (ignored): $error\n" );
1021                         $this->ignoreErrors( $ignore );
1022                 } else {
1023                         $sql1line = str_replace( "\n", "\\n", $sql );
1024                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
1025                         wfDebug( "SQL ERROR: " . $error . "\n" );
1026                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1027                 }
1028         }
1029
1030         /**
1031          * Intended to be compatible with the PEAR::DB wrapper functions.
1032          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1033          *
1034          * ? = scalar value, quoted as necessary
1035          * ! = raw SQL bit (a function for instance)
1036          * & = filename; reads the file and inserts as a blob
1037          *     (we don't use this though...)
1038          *
1039          * @param $sql string
1040          * @param $func string
1041          *
1042          * @return array
1043          */
1044         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1045                 /* MySQL doesn't support prepared statements (yet), so just
1046                    pack up the query for reference. We'll manually replace
1047                    the bits later. */
1048                 return array( 'query' => $sql, 'func' => $func );
1049         }
1050
1051         /**
1052          * Free a prepared query, generated by prepare().
1053          * @param $prepared
1054          */
1055         protected function freePrepared( $prepared ) {
1056                 /* No-op by default */
1057         }
1058
1059         /**
1060          * Execute a prepared query with the various arguments
1061          * @param string $prepared the prepared sql
1062          * @param $args Mixed: Either an array here, or put scalars as varargs
1063          *
1064          * @return ResultWrapper
1065          */
1066         public function execute( $prepared, $args = null ) {
1067                 if ( !is_array( $args ) ) {
1068                         # Pull the var args
1069                         $args = func_get_args();
1070                         array_shift( $args );
1071                 }
1072
1073                 $sql = $this->fillPrepared( $prepared['query'], $args );
1074
1075                 return $this->query( $sql, $prepared['func'] );
1076         }
1077
1078         /**
1079          * For faking prepared SQL statements on DBs that don't support it directly.
1080          *
1081          * @param string $preparedQuery a 'preparable' SQL statement
1082          * @param array $args of arguments to fill it with
1083          * @return string executable SQL
1084          */
1085         public function fillPrepared( $preparedQuery, $args ) {
1086                 reset( $args );
1087                 $this->preparedArgs =& $args;
1088
1089                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1090                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1091         }
1092
1093         /**
1094          * preg_callback func for fillPrepared()
1095          * The arguments should be in $this->preparedArgs and must not be touched
1096          * while we're doing this.
1097          *
1098          * @param $matches Array
1099          * @throws DBUnexpectedError
1100          * @return String
1101          */
1102         protected function fillPreparedArg( $matches ) {
1103                 switch ( $matches[1] ) {
1104                         case '\\?':
1105                                 return '?';
1106                         case '\\!':
1107                                 return '!';
1108                         case '\\&':
1109                                 return '&';
1110                 }
1111
1112                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1113
1114                 switch ( $matches[1] ) {
1115                         case '?':
1116                                 return $this->addQuotes( $arg );
1117                         case '!':
1118                                 return $arg;
1119                         case '&':
1120                                 # return $this->addQuotes( file_get_contents( $arg ) );
1121                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1122                         default:
1123                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1124                 }
1125         }
1126
1127         /**
1128          * Free a result object returned by query() or select(). It's usually not
1129          * necessary to call this, just use unset() or let the variable holding
1130          * the result object go out of scope.
1131          *
1132          * @param $res Mixed: A SQL result
1133          */
1134         public function freeResult( $res ) {
1135         }
1136
1137         /**
1138          * A SELECT wrapper which returns a single field from a single result row.
1139          *
1140          * Usually throws a DBQueryError on failure. If errors are explicitly
1141          * ignored, returns false on failure.
1142          *
1143          * If no result rows are returned from the query, false is returned.
1144          *
1145          * @param string|array $table Table name. See DatabaseBase::select() for details.
1146          * @param string $var The field name to select. This must be a valid SQL
1147          *   fragment: do not use unvalidated user input.
1148          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1149          * @param string $fname The function name of the caller.
1150          * @param string|array $options The query options. See DatabaseBase::select() for details.
1151          *
1152          * @return bool|mixed The value from the field, or false on failure.
1153          */
1154         public function selectField( $table, $var, $cond = '', $fname = __METHOD__,
1155                 $options = array()
1156         ) {
1157                 if ( !is_array( $options ) ) {
1158                         $options = array( $options );
1159                 }
1160
1161                 $options['LIMIT'] = 1;
1162
1163                 $res = $this->select( $table, $var, $cond, $fname, $options );
1164
1165                 if ( $res === false || !$this->numRows( $res ) ) {
1166                         return false;
1167                 }
1168
1169                 $row = $this->fetchRow( $res );
1170
1171                 if ( $row !== false ) {
1172                         return reset( $row );
1173                 } else {
1174                         return false;
1175                 }
1176         }
1177
1178         /**
1179          * Returns an optional USE INDEX clause to go after the table, and a
1180          * string to go at the end of the query.
1181          *
1182          * @param array $options associative array of options to be turned into
1183          *              an SQL query, valid keys are listed in the function.
1184          * @return Array
1185          * @see DatabaseBase::select()
1186          */
1187         public function makeSelectOptions( $options ) {
1188                 $preLimitTail = $postLimitTail = '';
1189                 $startOpts = '';
1190
1191                 $noKeyOptions = array();
1192
1193                 foreach ( $options as $key => $option ) {
1194                         if ( is_numeric( $key ) ) {
1195                                 $noKeyOptions[$option] = true;
1196                         }
1197                 }
1198
1199                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1200
1201                 $preLimitTail .= $this->makeOrderBy( $options );
1202
1203                 // if (isset($options['LIMIT'])) {
1204                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1205                 //              isset($options['OFFSET']) ? $options['OFFSET']
1206                 //              : false);
1207                 // }
1208
1209                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1210                         $postLimitTail .= ' FOR UPDATE';
1211                 }
1212
1213                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1214                         $postLimitTail .= ' LOCK IN SHARE MODE';
1215                 }
1216
1217                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1218                         $startOpts .= 'DISTINCT';
1219                 }
1220
1221                 # Various MySQL extensions
1222                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1223                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1224                 }
1225
1226                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1227                         $startOpts .= ' HIGH_PRIORITY';
1228                 }
1229
1230                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1231                         $startOpts .= ' SQL_BIG_RESULT';
1232                 }
1233
1234                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1235                         $startOpts .= ' SQL_BUFFER_RESULT';
1236                 }
1237
1238                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1239                         $startOpts .= ' SQL_SMALL_RESULT';
1240                 }
1241
1242                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1243                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1244                 }
1245
1246                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1247                         $startOpts .= ' SQL_CACHE';
1248                 }
1249
1250                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1251                         $startOpts .= ' SQL_NO_CACHE';
1252                 }
1253
1254                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1255                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1256                 } else {
1257                         $useIndex = '';
1258                 }
1259
1260                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1261         }
1262
1263         /**
1264          * Returns an optional GROUP BY with an optional HAVING
1265          *
1266          * @param array $options associative array of options
1267          * @return string
1268          * @see DatabaseBase::select()
1269          * @since 1.21
1270          */
1271         public function makeGroupByWithHaving( $options ) {
1272                 $sql = '';
1273                 if ( isset( $options['GROUP BY'] ) ) {
1274                         $gb = is_array( $options['GROUP BY'] )
1275                                 ? implode( ',', $options['GROUP BY'] )
1276                                 : $options['GROUP BY'];
1277                         $sql .= ' GROUP BY ' . $gb;
1278                 }
1279                 if ( isset( $options['HAVING'] ) ) {
1280                         $having = is_array( $options['HAVING'] )
1281                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1282                                 : $options['HAVING'];
1283                         $sql .= ' HAVING ' . $having;
1284                 }
1285                 return $sql;
1286         }
1287
1288         /**
1289          * Returns an optional ORDER BY
1290          *
1291          * @param array $options associative array of options
1292          * @return string
1293          * @see DatabaseBase::select()
1294          * @since 1.21
1295          */
1296         public function makeOrderBy( $options ) {
1297                 if ( isset( $options['ORDER BY'] ) ) {
1298                         $ob = is_array( $options['ORDER BY'] )
1299                                 ? implode( ',', $options['ORDER BY'] )
1300                                 : $options['ORDER BY'];
1301                         return ' ORDER BY ' . $ob;
1302                 }
1303                 return '';
1304         }
1305
1306         /**
1307          * Execute a SELECT query constructed using the various parameters provided.
1308          * See below for full details of the parameters.
1309          *
1310          * @param string|array $table Table name
1311          * @param string|array $vars Field names
1312          * @param string|array $conds Conditions
1313          * @param string $fname Caller function name
1314          * @param array $options Query options
1315          * @param $join_conds Array Join conditions
1316          *
1317          * @param $table string|array
1318          *
1319          * May be either an array of table names, or a single string holding a table
1320          * name. If an array is given, table aliases can be specified, for example:
1321          *
1322          *    array( 'a' => 'user' )
1323          *
1324          * This includes the user table in the query, with the alias "a" available
1325          * for use in field names (e.g. a.user_name).
1326          *
1327          * All of the table names given here are automatically run through
1328          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1329          * added, and various other table name mappings to be performed.
1330          *
1331          *
1332          * @param $vars string|array
1333          *
1334          * May be either a field name or an array of field names. The field names
1335          * can be complete fragments of SQL, for direct inclusion into the SELECT
1336          * query. If an array is given, field aliases can be specified, for example:
1337          *
1338          *   array( 'maxrev' => 'MAX(rev_id)' )
1339          *
1340          * This includes an expression with the alias "maxrev" in the query.
1341          *
1342          * If an expression is given, care must be taken to ensure that it is
1343          * DBMS-independent.
1344          *
1345          *
1346          * @param $conds string|array
1347          *
1348          * May be either a string containing a single condition, or an array of
1349          * conditions. If an array is given, the conditions constructed from each
1350          * element are combined with AND.
1351          *
1352          * Array elements may take one of two forms:
1353          *
1354          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1355          *   - Elements with a string key are interpreted as equality conditions,
1356          *     where the key is the field name.
1357          *     - If the value of such an array element is a scalar (such as a
1358          *       string), it will be treated as data and thus quoted appropriately.
1359          *       If it is null, an IS NULL clause will be added.
1360          *     - If the value is an array, an IN(...) clause will be constructed,
1361          *       such that the field name may match any of the elements in the
1362          *       array. The elements of the array will be quoted.
1363          *
1364          * Note that expressions are often DBMS-dependent in their syntax.
1365          * DBMS-independent wrappers are provided for constructing several types of
1366          * expression commonly used in condition queries. See:
1367          *    - DatabaseBase::buildLike()
1368          *    - DatabaseBase::conditional()
1369          *
1370          *
1371          * @param $options string|array
1372          *
1373          * Optional: Array of query options. Boolean options are specified by
1374          * including them in the array as a string value with a numeric key, for
1375          * example:
1376          *
1377          *    array( 'FOR UPDATE' )
1378          *
1379          * The supported options are:
1380          *
1381          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1382          *     with LIMIT can theoretically be used for paging through a result set,
1383          *     but this is discouraged in MediaWiki for performance reasons.
1384          *
1385          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1386          *     and then the first rows are taken until the limit is reached. LIMIT
1387          *     is applied to a result set after OFFSET.
1388          *
1389          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1390          *     changed until the next COMMIT.
1391          *
1392          *   - DISTINCT: Boolean: return only unique result rows.
1393          *
1394          *   - GROUP BY: May be either an SQL fragment string naming a field or
1395          *     expression to group by, or an array of such SQL fragments.
1396          *
1397          *   - HAVING: May be either an string containing a HAVING clause or an array of
1398          *     conditions building the HAVING clause. If an array is given, the conditions
1399          *     constructed from each element are combined with AND.
1400          *
1401          *   - ORDER BY: May be either an SQL fragment giving a field name or
1402          *     expression to order by, or an array of such SQL fragments.
1403          *
1404          *   - USE INDEX: This may be either a string giving the index name to use
1405          *     for the query, or an array. If it is an associative array, each key
1406          *     gives the table name (or alias), each value gives the index name to
1407          *     use for that table. All strings are SQL fragments and so should be
1408          *     validated by the caller.
1409          *
1410          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1411          *     instead of SELECT.
1412          *
1413          * And also the following boolean MySQL extensions, see the MySQL manual
1414          * for documentation:
1415          *
1416          *    - LOCK IN SHARE MODE
1417          *    - STRAIGHT_JOIN
1418          *    - HIGH_PRIORITY
1419          *    - SQL_BIG_RESULT
1420          *    - SQL_BUFFER_RESULT
1421          *    - SQL_SMALL_RESULT
1422          *    - SQL_CALC_FOUND_ROWS
1423          *    - SQL_CACHE
1424          *    - SQL_NO_CACHE
1425          *
1426          *
1427          * @param $join_conds string|array
1428          *
1429          * Optional associative array of table-specific join conditions. In the
1430          * most common case, this is unnecessary, since the join condition can be
1431          * in $conds. However, it is useful for doing a LEFT JOIN.
1432          *
1433          * The key of the array contains the table name or alias. The value is an
1434          * array with two elements, numbered 0 and 1. The first gives the type of
1435          * join, the second is an SQL fragment giving the join condition for that
1436          * table. For example:
1437          *
1438          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1439          *
1440          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1441          *   with no rows in it will be returned. If there was a query error, a
1442          *   DBQueryError exception will be thrown, except if the "ignore errors"
1443          *   option was set, in which case false will be returned.
1444          */
1445         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1446                 $options = array(), $join_conds = array() ) {
1447                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1448
1449                 return $this->query( $sql, $fname );
1450         }
1451
1452         /**
1453          * The equivalent of DatabaseBase::select() except that the constructed SQL
1454          * is returned, instead of being immediately executed. This can be useful for
1455          * doing UNION queries, where the SQL text of each query is needed. In general,
1456          * however, callers outside of Database classes should just use select().
1457          *
1458          * @param string|array $table Table name
1459          * @param string|array $vars Field names
1460          * @param string|array $conds Conditions
1461          * @param string $fname Caller function name
1462          * @param string|array $options Query options
1463          * @param $join_conds string|array Join conditions
1464          *
1465          * @return string SQL query string.
1466          * @see DatabaseBase::select()
1467          */
1468         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1469                 $options = array(), $join_conds = array() )
1470         {
1471                 if ( is_array( $vars ) ) {
1472                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1473                 }
1474
1475                 $options = (array)$options;
1476                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1477                         ? $options['USE INDEX']
1478                         : array();
1479
1480                 if ( is_array( $table ) ) {
1481                         $from = ' FROM ' .
1482                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1483                 } elseif ( $table != '' ) {
1484                         if ( $table[0] == ' ' ) {
1485                                 $from = ' FROM ' . $table;
1486                         } else {
1487                                 $from = ' FROM ' .
1488                                         $this->tableNamesWithUseIndexOrJOIN( array( $table ), $useIndexes, array() );
1489                         }
1490                 } else {
1491                         $from = '';
1492                 }
1493
1494                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1495                         $this->makeSelectOptions( $options );
1496
1497                 if ( !empty( $conds ) ) {
1498                         if ( is_array( $conds ) ) {
1499                                 $conds = $this->makeList( $conds, LIST_AND );
1500                         }
1501                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1502                 } else {
1503                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1504                 }
1505
1506                 if ( isset( $options['LIMIT'] ) ) {
1507                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1508                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1509                 }
1510                 $sql = "$sql $postLimitTail";
1511
1512                 if ( isset( $options['EXPLAIN'] ) ) {
1513                         $sql = 'EXPLAIN ' . $sql;
1514                 }
1515
1516                 return $sql;
1517         }
1518
1519         /**
1520          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1521          * that a single row object is returned. If the query returns no rows,
1522          * false is returned.
1523          *
1524          * @param string|array $table Table name
1525          * @param string|array $vars Field names
1526          * @param array $conds Conditions
1527          * @param string $fname Caller function name
1528          * @param string|array $options Query options
1529          * @param $join_conds array|string Join conditions
1530          *
1531          * @return object|bool
1532          */
1533         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1534                 $options = array(), $join_conds = array() )
1535         {
1536                 $options = (array)$options;
1537                 $options['LIMIT'] = 1;
1538                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1539
1540                 if ( $res === false ) {
1541                         return false;
1542                 }
1543
1544                 if ( !$this->numRows( $res ) ) {
1545                         return false;
1546                 }
1547
1548                 $obj = $this->fetchObject( $res );
1549
1550                 return $obj;
1551         }
1552
1553         /**
1554          * Estimate rows in dataset.
1555          *
1556          * MySQL allows you to estimate the number of rows that would be returned
1557          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1558          * index cardinality statistics, and is notoriously inaccurate, especially
1559          * when large numbers of rows have recently been added or deleted.
1560          *
1561          * For DBMSs that don't support fast result size estimation, this function
1562          * will actually perform the SELECT COUNT(*).
1563          *
1564          * Takes the same arguments as DatabaseBase::select().
1565          *
1566          * @param string $table table name
1567          * @param array|string $vars : unused
1568          * @param array|string $conds : filters on the table
1569          * @param string $fname function name for profiling
1570          * @param array $options options for select
1571          * @return Integer: row count
1572          */
1573         public function estimateRowCount( $table, $vars = '*', $conds = '',
1574                 $fname = __METHOD__, $options = array() )
1575         {
1576                 $rows = 0;
1577                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1578
1579                 if ( $res ) {
1580                         $row = $this->fetchRow( $res );
1581                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1582                 }
1583
1584                 return $rows;
1585         }
1586
1587         /**
1588          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1589          * It's only slightly flawed. Don't use for anything important.
1590          *
1591          * @param string $sql A SQL Query
1592          *
1593          * @return string
1594          */
1595         static function generalizeSQL( $sql ) {
1596                 # This does the same as the regexp below would do, but in such a way
1597                 # as to avoid crashing php on some large strings.
1598                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1599
1600                 $sql = str_replace( "\\\\", '', $sql );
1601                 $sql = str_replace( "\\'", '', $sql );
1602                 $sql = str_replace( "\\\"", '', $sql );
1603                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1604                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1605
1606                 # All newlines, tabs, etc replaced by single space
1607                 $sql = preg_replace( '/\s+/', ' ', $sql );
1608
1609                 # All numbers => N
1610                 $sql = preg_replace( '/-?[0-9]+/s', 'N', $sql );
1611
1612                 return $sql;
1613         }
1614
1615         /**
1616          * Determines whether a field exists in a table
1617          *
1618          * @param string $table table name
1619          * @param string $field filed to check on that table
1620          * @param string $fname calling function name (optional)
1621          * @return Boolean: whether $table has filed $field
1622          */
1623         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1624                 $info = $this->fieldInfo( $table, $field );
1625
1626                 return (bool)$info;
1627         }
1628
1629         /**
1630          * Determines whether an index exists
1631          * Usually throws a DBQueryError on failure
1632          * If errors are explicitly ignored, returns NULL on failure
1633          *
1634          * @param $table
1635          * @param $index
1636          * @param $fname string
1637          *
1638          * @return bool|null
1639          */
1640         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1641                 if ( !$this->tableExists( $table ) ) {
1642                         return null;
1643                 }
1644
1645                 $info = $this->indexInfo( $table, $index, $fname );
1646                 if ( is_null( $info ) ) {
1647                         return null;
1648                 } else {
1649                         return $info !== false;
1650                 }
1651         }
1652
1653         /**
1654          * Query whether a given table exists
1655          *
1656          * @param $table string
1657          * @param $fname string
1658          *
1659          * @return bool
1660          */
1661         public function tableExists( $table, $fname = __METHOD__ ) {
1662                 $table = $this->tableName( $table );
1663                 $old = $this->ignoreErrors( true );
1664                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1665                 $this->ignoreErrors( $old );
1666
1667                 return (bool)$res;
1668         }
1669
1670         /**
1671          * mysql_field_type() wrapper
1672          * @param $res
1673          * @param $index
1674          * @return string
1675          */
1676         public function fieldType( $res, $index ) {
1677                 if ( $res instanceof ResultWrapper ) {
1678                         $res = $res->result;
1679                 }
1680
1681                 return mysql_field_type( $res, $index );
1682         }
1683
1684         /**
1685          * Determines if a given index is unique
1686          *
1687          * @param $table string
1688          * @param $index string
1689          *
1690          * @return bool
1691          */
1692         public function indexUnique( $table, $index ) {
1693                 $indexInfo = $this->indexInfo( $table, $index );
1694
1695                 if ( !$indexInfo ) {
1696                         return null;
1697                 }
1698
1699                 return !$indexInfo[0]->Non_unique;
1700         }
1701
1702         /**
1703          * Helper for DatabaseBase::insert().
1704          *
1705          * @param $options array
1706          * @return string
1707          */
1708         protected function makeInsertOptions( $options ) {
1709                 return implode( ' ', $options );
1710         }
1711
1712         /**
1713          * INSERT wrapper, inserts an array into a table.
1714          *
1715          * $a may be either:
1716          *
1717          *   - A single associative array. The array keys are the field names, and
1718          *     the values are the values to insert. The values are treated as data
1719          *     and will be quoted appropriately. If NULL is inserted, this will be
1720          *     converted to a database NULL.
1721          *   - An array with numeric keys, holding a list of associative arrays.
1722          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1723          *     each subarray must be identical to each other, and in the same order.
1724          *
1725          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1726          * returns success.
1727          *
1728          * $options is an array of options, with boolean options encoded as values
1729          * with numeric keys, in the same style as $options in
1730          * DatabaseBase::select(). Supported options are:
1731          *
1732          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1733          *     any rows which cause duplicate key errors are not inserted. It's
1734          *     possible to determine how many rows were successfully inserted using
1735          *     DatabaseBase::affectedRows().
1736          *
1737          * @param $table   String Table name. This will be passed through
1738          *                 DatabaseBase::tableName().
1739          * @param $a       Array of rows to insert
1740          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1741          * @param array $options of options
1742          *
1743          * @return bool
1744          */
1745         public function insert( $table, $a, $fname = __METHOD__, $options = array() ) {
1746                 # No rows to insert, easy just return now
1747                 if ( !count( $a ) ) {
1748                         return true;
1749                 }
1750
1751                 $table = $this->tableName( $table );
1752
1753                 if ( !is_array( $options ) ) {
1754                         $options = array( $options );
1755                 }
1756
1757                 $fh = null;
1758                 if ( isset( $options['fileHandle'] ) ) {
1759                         $fh = $options['fileHandle'];
1760                 }
1761                 $options = $this->makeInsertOptions( $options );
1762
1763                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1764                         $multi = true;
1765                         $keys = array_keys( $a[0] );
1766                 } else {
1767                         $multi = false;
1768                         $keys = array_keys( $a );
1769                 }
1770
1771                 $sql = 'INSERT ' . $options .
1772                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1773
1774                 if ( $multi ) {
1775                         $first = true;
1776                         foreach ( $a as $row ) {
1777                                 if ( $first ) {
1778                                         $first = false;
1779                                 } else {
1780                                         $sql .= ',';
1781                                 }
1782                                 $sql .= '(' . $this->makeList( $row ) . ')';
1783                         }
1784                 } else {
1785                         $sql .= '(' . $this->makeList( $a ) . ')';
1786                 }
1787
1788                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1789                         return false;
1790                 } elseif ( $fh !== null ) {
1791                         return true;
1792                 }
1793
1794                 return (bool)$this->query( $sql, $fname );
1795         }
1796
1797         /**
1798          * Make UPDATE options for the DatabaseBase::update function
1799          *
1800          * @param array $options The options passed to DatabaseBase::update
1801          * @return string
1802          */
1803         protected function makeUpdateOptions( $options ) {
1804                 if ( !is_array( $options ) ) {
1805                         $options = array( $options );
1806                 }
1807
1808                 $opts = array();
1809
1810                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1811                         $opts[] = $this->lowPriorityOption();
1812                 }
1813
1814                 if ( in_array( 'IGNORE', $options ) ) {
1815                         $opts[] = 'IGNORE';
1816                 }
1817
1818                 return implode( ' ', $opts );
1819         }
1820
1821         /**
1822          * UPDATE wrapper. Takes a condition array and a SET array.
1823          *
1824          * @param $table  String name of the table to UPDATE. This will be passed through
1825          *                DatabaseBase::tableName().
1826          *
1827          * @param array $values  An array of values to SET. For each array element,
1828          *                the key gives the field name, and the value gives the data
1829          *                to set that field to. The data will be quoted by
1830          *                DatabaseBase::addQuotes().
1831          *
1832          * @param $conds  Array:  An array of conditions (WHERE). See
1833          *                DatabaseBase::select() for the details of the format of
1834          *                condition arrays. Use '*' to update all rows.
1835          *
1836          * @param $fname  String: The function name of the caller (from __METHOD__),
1837          *                for logging and profiling.
1838          *
1839          * @param array $options An array of UPDATE options, can be:
1840          *                   - IGNORE: Ignore unique key conflicts
1841          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1842          * @return Boolean
1843          */
1844         function update( $table, $values, $conds, $fname = __METHOD__, $options = array() ) {
1845                 $table = $this->tableName( $table );
1846                 $opts = $this->makeUpdateOptions( $options );
1847                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1848
1849                 if ( $conds !== array() && $conds !== '*' ) {
1850                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1851                 }
1852
1853                 return $this->query( $sql, $fname );
1854         }
1855
1856         /**
1857          * Makes an encoded list of strings from an array
1858          * @param array $a containing the data
1859          * @param int $mode Constant
1860          *      - LIST_COMMA:          comma separated, no field names
1861          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1862          *        the documentation for $conds in DatabaseBase::select().
1863          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1864          *      - LIST_SET:            comma separated with field names, like a SET clause
1865          *      - LIST_NAMES:          comma separated field names
1866          *
1867          * @throws MWException|DBUnexpectedError
1868          * @return string
1869          */
1870         public function makeList( $a, $mode = LIST_COMMA ) {
1871                 if ( !is_array( $a ) ) {
1872                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1873                 }
1874
1875                 $first = true;
1876                 $list = '';
1877
1878                 foreach ( $a as $field => $value ) {
1879                         if ( !$first ) {
1880                                 if ( $mode == LIST_AND ) {
1881                                         $list .= ' AND ';
1882                                 } elseif ( $mode == LIST_OR ) {
1883                                         $list .= ' OR ';
1884                                 } else {
1885                                         $list .= ',';
1886                                 }
1887                         } else {
1888                                 $first = false;
1889                         }
1890
1891                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1892                                 $list .= "($value)";
1893                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1894                                 $list .= "$value";
1895                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1896                                 if ( count( $value ) == 0 ) {
1897                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1898                                 } elseif ( count( $value ) == 1 ) {
1899                                         // Special-case single values, as IN isn't terribly efficient
1900                                         // Don't necessarily assume the single key is 0; we don't
1901                                         // enforce linear numeric ordering on other arrays here.
1902                                         $value = array_values( $value );
1903                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1904                                 } else {
1905                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1906                                 }
1907                         } elseif ( $value === null ) {
1908                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1909                                         $list .= "$field IS ";
1910                                 } elseif ( $mode == LIST_SET ) {
1911                                         $list .= "$field = ";
1912                                 }
1913                                 $list .= 'NULL';
1914                         } else {
1915                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1916                                         $list .= "$field = ";
1917                                 }
1918                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1919                         }
1920                 }
1921
1922                 return $list;
1923         }
1924
1925         /**
1926          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1927          * The keys on each level may be either integers or strings.
1928          *
1929          * @param array $data organized as 2-d
1930          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
1931          * @param string $baseKey field name to match the base-level keys to (eg 'pl_namespace')
1932          * @param string $subKey field name to match the sub-level keys to (eg 'pl_title')
1933          * @return Mixed: string SQL fragment, or false if no items in array.
1934          */
1935         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1936                 $conds = array();
1937
1938                 foreach ( $data as $base => $sub ) {
1939                         if ( count( $sub ) ) {
1940                                 $conds[] = $this->makeList(
1941                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1942                                         LIST_AND );
1943                         }
1944                 }
1945
1946                 if ( $conds ) {
1947                         return $this->makeList( $conds, LIST_OR );
1948                 } else {
1949                         // Nothing to search for...
1950                         return false;
1951                 }
1952         }
1953
1954         /**
1955          * Return aggregated value alias
1956          *
1957          * @param $valuedata
1958          * @param $valuename string
1959          *
1960          * @return string
1961          */
1962         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1963                 return $valuename;
1964         }
1965
1966         /**
1967          * @param $field
1968          * @return string
1969          */
1970         public function bitNot( $field ) {
1971                 return "(~$field)";
1972         }
1973
1974         /**
1975          * @param $fieldLeft
1976          * @param $fieldRight
1977          * @return string
1978          */
1979         public function bitAnd( $fieldLeft, $fieldRight ) {
1980                 return "($fieldLeft & $fieldRight)";
1981         }
1982
1983         /**
1984          * @param  $fieldLeft
1985          * @param  $fieldRight
1986          * @return string
1987          */
1988         public function bitOr( $fieldLeft, $fieldRight ) {
1989                 return "($fieldLeft | $fieldRight)";
1990         }
1991
1992         /**
1993          * Build a concatenation list to feed into a SQL query
1994          * @param array $stringList list of raw SQL expressions; caller is responsible for any quoting
1995          * @return String
1996          */
1997         public function buildConcat( $stringList ) {
1998                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1999         }
2000
2001         /**
2002          * Change the current database
2003          *
2004          * @todo Explain what exactly will fail if this is not overridden.
2005          *
2006          * @param $db
2007          *
2008          * @return bool Success or failure
2009          */
2010         public function selectDB( $db ) {
2011                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
2012                 # if your database engine supports a concept similar to MySQL's
2013                 # databases you may as well.
2014                 $this->mDBname = $db;
2015                 return true;
2016         }
2017
2018         /**
2019          * Get the current DB name
2020          */
2021         public function getDBname() {
2022                 return $this->mDBname;
2023         }
2024
2025         /**
2026          * Get the server hostname or IP address
2027          */
2028         public function getServer() {
2029                 return $this->mServer;
2030         }
2031
2032         /**
2033          * Format a table name ready for use in constructing an SQL query
2034          *
2035          * This does two important things: it quotes the table names to clean them up,
2036          * and it adds a table prefix if only given a table name with no quotes.
2037          *
2038          * All functions of this object which require a table name call this function
2039          * themselves. Pass the canonical name to such functions. This is only needed
2040          * when calling query() directly.
2041          *
2042          * @param string $name database table name
2043          * @param string $format One of:
2044          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2045          *            so that it can be used in a query.
2046          *   raw - Do not add identifier quotes to the table name
2047          * @return String: full database name
2048          */
2049         public function tableName( $name, $format = 'quoted' ) {
2050                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
2051                 # Skip the entire process when we have a string quoted on both ends.
2052                 # Note that we check the end so that we will still quote any use of
2053                 # use of `database`.table. But won't break things if someone wants
2054                 # to query a database table with a dot in the name.
2055                 if ( $this->isQuotedIdentifier( $name ) ) {
2056                         return $name;
2057                 }
2058
2059                 # Lets test for any bits of text that should never show up in a table
2060                 # name. Basically anything like JOIN or ON which are actually part of
2061                 # SQL queries, but may end up inside of the table value to combine
2062                 # sql. Such as how the API is doing.
2063                 # Note that we use a whitespace test rather than a \b test to avoid
2064                 # any remote case where a word like on may be inside of a table name
2065                 # surrounded by symbols which may be considered word breaks.
2066                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2067                         return $name;
2068                 }
2069
2070                 # Split database and table into proper variables.
2071                 # We reverse the explode so that database.table and table both output
2072                 # the correct table.
2073                 $dbDetails = explode( '.', $name, 2 );
2074                 if ( count( $dbDetails ) == 2 ) {
2075                         list( $database, $table ) = $dbDetails;
2076                         # We don't want any prefix added in this case
2077                         $prefix = '';
2078                 } else {
2079                         list( $table ) = $dbDetails;
2080                         if ( $wgSharedDB !== null # We have a shared database
2081                                 && $this->mForeign == false # We're not working on a foreign database
2082                                 && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
2083                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2084                         ) {
2085                                 $database = $wgSharedDB;
2086                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2087                         } else {
2088                                 $database = null;
2089                                 $prefix = $this->mTablePrefix; # Default prefix
2090                         }
2091                 }
2092
2093                 # Quote $table and apply the prefix if not quoted.
2094                 $tableName = "{$prefix}{$table}";
2095                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) ) {
2096                         $tableName = $this->addIdentifierQuotes( $tableName );
2097                 }
2098
2099                 # Quote $database and merge it with the table name if needed
2100                 if ( $database !== null ) {
2101                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2102                                 $database = $this->addIdentifierQuotes( $database );
2103                         }
2104                         $tableName = $database . '.' . $tableName;
2105                 }
2106
2107                 return $tableName;
2108         }
2109
2110         /**
2111          * Fetch a number of table names into an array
2112          * This is handy when you need to construct SQL for joins
2113          *
2114          * Example:
2115          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2116          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2117          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2118          *
2119          * @return array
2120          */
2121         public function tableNames() {
2122                 $inArray = func_get_args();
2123                 $retVal = array();
2124
2125                 foreach ( $inArray as $name ) {
2126                         $retVal[$name] = $this->tableName( $name );
2127                 }
2128
2129                 return $retVal;
2130         }
2131
2132         /**
2133          * Fetch a number of table names into an zero-indexed numerical array
2134          * This is handy when you need to construct SQL for joins
2135          *
2136          * Example:
2137          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2138          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2139          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2140          *
2141          * @return array
2142          */
2143         public function tableNamesN() {
2144                 $inArray = func_get_args();
2145                 $retVal = array();
2146
2147                 foreach ( $inArray as $name ) {
2148                         $retVal[] = $this->tableName( $name );
2149                 }
2150
2151                 return $retVal;
2152         }
2153
2154         /**
2155          * Get an aliased table name
2156          * e.g. tableName AS newTableName
2157          *
2158          * @param string $name Table name, see tableName()
2159          * @param string|bool $alias Alias (optional)
2160          * @return string SQL name for aliased table. Will not alias a table to its own name
2161          */
2162         public function tableNameWithAlias( $name, $alias = false ) {
2163                 if ( !$alias || $alias == $name ) {
2164                         return $this->tableName( $name );
2165                 } else {
2166                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2167                 }
2168         }
2169
2170         /**
2171          * Gets an array of aliased table names
2172          *
2173          * @param $tables array( [alias] => table )
2174          * @return array of strings, see tableNameWithAlias()
2175          */
2176         public function tableNamesWithAlias( $tables ) {
2177                 $retval = array();
2178                 foreach ( $tables as $alias => $table ) {
2179                         if ( is_numeric( $alias ) ) {
2180                                 $alias = $table;
2181                         }
2182                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2183                 }
2184                 return $retval;
2185         }
2186
2187         /**
2188          * Get an aliased field name
2189          * e.g. fieldName AS newFieldName
2190          *
2191          * @param string $name Field name
2192          * @param string|bool $alias Alias (optional)
2193          * @return string SQL name for aliased field. Will not alias a field to its own name
2194          */
2195         public function fieldNameWithAlias( $name, $alias = false ) {
2196                 if ( !$alias || (string)$alias === (string)$name ) {
2197                         return $name;
2198                 } else {
2199                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2200                 }
2201         }
2202
2203         /**
2204          * Gets an array of aliased field names
2205          *
2206          * @param $fields array( [alias] => field )
2207          * @return array of strings, see fieldNameWithAlias()
2208          */
2209         public function fieldNamesWithAlias( $fields ) {
2210                 $retval = array();
2211                 foreach ( $fields as $alias => $field ) {
2212                         if ( is_numeric( $alias ) ) {
2213                                 $alias = $field;
2214                         }
2215                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2216                 }
2217                 return $retval;
2218         }
2219
2220         /**
2221          * Get the aliased table name clause for a FROM clause
2222          * which might have a JOIN and/or USE INDEX clause
2223          *
2224          * @param array $tables ( [alias] => table )
2225          * @param $use_index array Same as for select()
2226          * @param $join_conds array Same as for select()
2227          * @return string
2228          */
2229         protected function tableNamesWithUseIndexOrJOIN(
2230                 $tables, $use_index = array(), $join_conds = array()
2231         ) {
2232                 $ret = array();
2233                 $retJOIN = array();
2234                 $use_index = (array)$use_index;
2235                 $join_conds = (array)$join_conds;
2236
2237                 foreach ( $tables as $alias => $table ) {
2238                         if ( !is_string( $alias ) ) {
2239                                 // No alias? Set it equal to the table name
2240                                 $alias = $table;
2241                         }
2242                         // Is there a JOIN clause for this table?
2243                         if ( isset( $join_conds[$alias] ) ) {
2244                                 list( $joinType, $conds ) = $join_conds[$alias];
2245                                 $tableClause = $joinType;
2246                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2247                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2248                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2249                                         if ( $use != '' ) {
2250                                                 $tableClause .= ' ' . $use;
2251                                         }
2252                                 }
2253                                 $on = $this->makeList( (array)$conds, LIST_AND );
2254                                 if ( $on != '' ) {
2255                                         $tableClause .= ' ON (' . $on . ')';
2256                                 }
2257
2258                                 $retJOIN[] = $tableClause;
2259                         // Is there an INDEX clause for this table?
2260                         } elseif ( isset( $use_index[$alias] ) ) {
2261                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2262                                 $tableClause .= ' ' . $this->useIndexClause(
2263                                         implode( ',', (array)$use_index[$alias] ) );
2264
2265                                 $ret[] = $tableClause;
2266                         } else {
2267                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2268
2269                                 $ret[] = $tableClause;
2270                         }
2271                 }
2272
2273                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2274                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2275                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2276
2277                 // Compile our final table clause
2278                 return implode( ' ', array( $implicitJoins, $explicitJoins ) );
2279         }
2280
2281         /**
2282          * Get the name of an index in a given table
2283          *
2284          * @param $index
2285          *
2286          * @return string
2287          */
2288         protected function indexName( $index ) {
2289                 // Backwards-compatibility hack
2290                 $renamed = array(
2291                         'ar_usertext_timestamp' => 'usertext_timestamp',
2292                         'un_user_id' => 'user_id',
2293                         'un_user_ip' => 'user_ip',
2294                 );
2295
2296                 if ( isset( $renamed[$index] ) ) {
2297                         return $renamed[$index];
2298                 } else {
2299                         return $index;
2300                 }
2301         }
2302
2303         /**
2304          * If it's a string, adds quotes and backslashes
2305          * Otherwise returns as-is
2306          *
2307          * @param $s string
2308          *
2309          * @return string
2310          */
2311         public function addQuotes( $s ) {
2312                 if ( $s === null ) {
2313                         return 'NULL';
2314                 } else {
2315                         # This will also quote numeric values. This should be harmless,
2316                         # and protects against weird problems that occur when they really
2317                         # _are_ strings such as article titles and string->number->string
2318                         # conversion is not 1:1.
2319                         return "'" . $this->strencode( $s ) . "'";
2320                 }
2321         }
2322
2323         /**
2324          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2325          * MySQL uses `backticks` while basically everything else uses double quotes.
2326          * Since MySQL is the odd one out here the double quotes are our generic
2327          * and we implement backticks in DatabaseMysql.
2328          *
2329          * @param $s string
2330          *
2331          * @return string
2332          */
2333         public function addIdentifierQuotes( $s ) {
2334                 return '"' . str_replace( '"', '""', $s ) . '"';
2335         }
2336
2337         /**
2338          * Returns if the given identifier looks quoted or not according to
2339          * the database convention for quoting identifiers .
2340          *
2341          * @param $name string
2342          *
2343          * @return boolean
2344          */
2345         public function isQuotedIdentifier( $name ) {
2346                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2347         }
2348
2349         /**
2350          * @param $s string
2351          * @return string
2352          */
2353         protected function escapeLikeInternal( $s ) {
2354                 $s = str_replace( '\\', '\\\\', $s );
2355                 $s = $this->strencode( $s );
2356                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2357
2358                 return $s;
2359         }
2360
2361         /**
2362          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2363          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2364          * Alternatively, the function could be provided with an array of aforementioned parameters.
2365          *
2366          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2367          * for subpages of 'My page title'.
2368          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2369          *
2370          * @since 1.16
2371          * @return String: fully built LIKE statement
2372          */
2373         public function buildLike() {
2374                 $params = func_get_args();
2375
2376                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2377                         $params = $params[0];
2378                 }
2379
2380                 $s = '';
2381
2382                 foreach ( $params as $value ) {
2383                         if ( $value instanceof LikeMatch ) {
2384                                 $s .= $value->toString();
2385                         } else {
2386                                 $s .= $this->escapeLikeInternal( $value );
2387                         }
2388                 }
2389
2390                 return " LIKE '" . $s . "' ";
2391         }
2392
2393         /**
2394          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2395          *
2396          * @return LikeMatch
2397          */
2398         public function anyChar() {
2399                 return new LikeMatch( '_' );
2400         }
2401
2402         /**
2403          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2404          *
2405          * @return LikeMatch
2406          */
2407         public function anyString() {
2408                 return new LikeMatch( '%' );
2409         }
2410
2411         /**
2412          * Returns an appropriately quoted sequence value for inserting a new row.
2413          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2414          * subclass will return an integer, and save the value for insertId()
2415          *
2416          * Any implementation of this function should *not* involve reusing
2417          * sequence numbers created for rolled-back transactions.
2418          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2419          * @param $seqName string
2420          * @return null
2421          */
2422         public function nextSequenceValue( $seqName ) {
2423                 return null;
2424         }
2425
2426         /**
2427          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2428          * is only needed because a) MySQL must be as efficient as possible due to
2429          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2430          * which index to pick.  Anyway, other databases might have different
2431          * indexes on a given table.  So don't bother overriding this unless you're
2432          * MySQL.
2433          * @param $index
2434          * @return string
2435          */
2436         public function useIndexClause( $index ) {
2437                 return '';
2438         }
2439
2440         /**
2441          * REPLACE query wrapper.
2442          *
2443          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2444          * except that when there is a duplicate key error, the old row is deleted
2445          * and the new row is inserted in its place.
2446          *
2447          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2448          * perform the delete, we need to know what the unique indexes are so that
2449          * we know how to find the conflicting rows.
2450          *
2451          * It may be more efficient to leave off unique indexes which are unlikely
2452          * to collide. However if you do this, you run the risk of encountering
2453          * errors which wouldn't have occurred in MySQL.
2454          *
2455          * @param string $table The table to replace the row(s) in.
2456          * @param array $rows Can be either a single row to insert, or multiple rows,
2457          *    in the same format as for DatabaseBase::insert()
2458          * @param array $uniqueIndexes is an array of indexes. Each element may be either
2459          *    a field name or an array of field names
2460          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2461          */
2462         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2463                 $quotedTable = $this->tableName( $table );
2464
2465                 if ( count( $rows ) == 0 ) {
2466                         return;
2467                 }
2468
2469                 # Single row case
2470                 if ( !is_array( reset( $rows ) ) ) {
2471                         $rows = array( $rows );
2472                 }
2473
2474                 foreach ( $rows as $row ) {
2475                         # Delete rows which collide
2476                         if ( $uniqueIndexes ) {
2477                                 $sql = "DELETE FROM $quotedTable WHERE ";
2478                                 $first = true;
2479                                 foreach ( $uniqueIndexes as $index ) {
2480                                         if ( $first ) {
2481                                                 $first = false;
2482                                                 $sql .= '( ';
2483                                         } else {
2484                                                 $sql .= ' ) OR ( ';
2485                                         }
2486                                         if ( is_array( $index ) ) {
2487                                                 $first2 = true;
2488                                                 foreach ( $index as $col ) {
2489                                                         if ( $first2 ) {
2490                                                                 $first2 = false;
2491                                                         } else {
2492                                                                 $sql .= ' AND ';
2493                                                         }
2494                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2495                                                 }
2496                                         } else {
2497                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2498                                         }
2499                                 }
2500                                 $sql .= ' )';
2501                                 $this->query( $sql, $fname );
2502                         }
2503
2504                         # Now insert the row
2505                         $this->insert( $table, $row, $fname );
2506                 }
2507         }
2508
2509         /**
2510          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2511          * statement.
2512          *
2513          * @param string $table Table name
2514          * @param array $rows Rows to insert
2515          * @param string $fname Caller function name
2516          *
2517          * @return ResultWrapper
2518          */
2519         protected function nativeReplace( $table, $rows, $fname ) {
2520                 $table = $this->tableName( $table );
2521
2522                 # Single row case
2523                 if ( !is_array( reset( $rows ) ) ) {
2524                         $rows = array( $rows );
2525                 }
2526
2527                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2528                 $first = true;
2529
2530                 foreach ( $rows as $row ) {
2531                         if ( $first ) {
2532                                 $first = false;
2533                         } else {
2534                                 $sql .= ',';
2535                         }
2536
2537                         $sql .= '(' . $this->makeList( $row ) . ')';
2538                 }
2539
2540                 return $this->query( $sql, $fname );
2541         }
2542
2543         /**
2544          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
2545          *
2546          * This updates any conflicting rows (according to the unique indexes) using
2547          * the provided SET clause and inserts any remaining (non-conflicted) rows.
2548          *
2549          * $rows may be either:
2550          *   - A single associative array. The array keys are the field names, and
2551          *     the values are the values to insert. The values are treated as data
2552          *     and will be quoted appropriately. If NULL is inserted, this will be
2553          *     converted to a database NULL.
2554          *   - An array with numeric keys, holding a list of associative arrays.
2555          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
2556          *     each subarray must be identical to each other, and in the same order.
2557          *
2558          * It may be more efficient to leave off unique indexes which are unlikely
2559          * to collide. However if you do this, you run the risk of encountering
2560          * errors which wouldn't have occurred in MySQL.
2561          *
2562          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
2563          * returns success.
2564          *
2565          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
2566          * @param array $rows A single row or list of rows to insert
2567          * @param array $uniqueIndexes List of single field names or field name tuples
2568          * @param array $set An array of values to SET. For each array element,
2569          *                the key gives the field name, and the value gives the data
2570          *                to set that field to. The data will be quoted by
2571          *                DatabaseBase::addQuotes().
2572          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2573          * @param array $options of options
2574          *
2575          * @return bool
2576          * @since 1.22
2577          */
2578         public function upsert(
2579                 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
2580         ) {
2581                 if ( !count( $rows ) ) {
2582                         return true; // nothing to do
2583                 }
2584                 $rows = is_array( reset( $rows ) ) ? $rows : array( $rows );
2585
2586                 if ( count( $uniqueIndexes ) ) {
2587                         $clauses = array(); // list WHERE clauses that each identify a single row
2588                         foreach ( $rows as $row ) {
2589                                 foreach ( $uniqueIndexes as $index ) {
2590                                         $index = is_array( $index ) ? $index : array( $index ); // columns
2591                                         $rowKey = array(); // unique key to this row
2592                                         foreach ( $index as $column ) {
2593                                                 $rowKey[$column] = $row[$column];
2594                                         }
2595                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2596                                 }
2597                         }
2598                         $where = array( $this->makeList( $clauses, LIST_OR ) );
2599                 } else {
2600                         $where = false;
2601                 }
2602
2603                 $useTrx = !$this->mTrxLevel;
2604                 if ( $useTrx ) {
2605                         $this->begin( $fname );
2606                 }
2607                 try {
2608                         # Update any existing conflicting row(s)
2609                         if ( $where !== false ) {
2610                                 $ok = $this->update( $table, $set, $where, $fname );
2611                         } else {
2612                                 $ok = true;
2613                         }
2614                         # Now insert any non-conflicting row(s)
2615                         $ok = $this->insert( $table, $rows, $fname, array( 'IGNORE' ) ) && $ok;
2616                 } catch ( Exception $e ) {
2617                         if ( $useTrx ) {
2618                                 $this->rollback( $fname );
2619                         }
2620                         throw $e;
2621                 }
2622                 if ( $useTrx ) {
2623                         $this->commit( $fname );
2624                 }
2625
2626                 return $ok;
2627         }
2628
2629         /**
2630          * DELETE where the condition is a join.
2631          *
2632          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2633          * we use sub-selects
2634          *
2635          * For safety, an empty $conds will not delete everything. If you want to
2636          * delete all rows where the join condition matches, set $conds='*'.
2637          *
2638          * DO NOT put the join condition in $conds.
2639          *
2640          * @param $delTable   String: The table to delete from.
2641          * @param $joinTable  String: The other table.
2642          * @param $delVar     String: The variable to join on, in the first table.
2643          * @param $joinVar    String: The variable to join on, in the second table.
2644          * @param $conds      Array: Condition array of field names mapped to variables,
2645          *                    ANDed together in the WHERE clause
2646          * @param $fname      String: Calling function name (use __METHOD__) for
2647          *                    logs/profiling
2648          * @throws DBUnexpectedError
2649          */
2650         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2651                 $fname = __METHOD__ )
2652         {
2653                 if ( !$conds ) {
2654                         throw new DBUnexpectedError( $this,
2655                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2656                 }
2657
2658                 $delTable = $this->tableName( $delTable );
2659                 $joinTable = $this->tableName( $joinTable );
2660                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2661                 if ( $conds != '*' ) {
2662                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2663                 }
2664                 $sql .= ')';
2665
2666                 $this->query( $sql, $fname );
2667         }
2668
2669         /**
2670          * Returns the size of a text field, or -1 for "unlimited"
2671          *
2672          * @param $table string
2673          * @param $field string
2674          *
2675          * @return int
2676          */
2677         public function textFieldSize( $table, $field ) {
2678                 $table = $this->tableName( $table );
2679                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2680                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2681                 $row = $this->fetchObject( $res );
2682
2683                 $m = array();
2684
2685                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2686                         $size = $m[1];
2687                 } else {
2688                         $size = -1;
2689                 }
2690
2691                 return $size;
2692         }
2693
2694         /**
2695          * A string to insert into queries to show that they're low-priority, like
2696          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2697          * string and nothing bad should happen.
2698          *
2699          * @return string Returns the text of the low priority option if it is
2700          *   supported, or a blank string otherwise
2701          */
2702         public function lowPriorityOption() {
2703                 return '';
2704         }
2705
2706         /**
2707          * DELETE query wrapper.
2708          *
2709          * @param array $table Table name
2710          * @param string|array $conds of conditions. See $conds in DatabaseBase::select() for
2711          *               the format. Use $conds == "*" to delete all rows
2712          * @param string $fname name of the calling function
2713          *
2714          * @throws DBUnexpectedError
2715          * @return bool|ResultWrapper
2716          */
2717         public function delete( $table, $conds, $fname = __METHOD__ ) {
2718                 if ( !$conds ) {
2719                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2720                 }
2721
2722                 $table = $this->tableName( $table );
2723                 $sql = "DELETE FROM $table";
2724
2725                 if ( $conds != '*' ) {
2726                         if ( is_array( $conds ) ) {
2727                                 $conds = $this->makeList( $conds, LIST_AND );
2728                         }
2729                         $sql .= ' WHERE ' . $conds;
2730                 }
2731
2732                 return $this->query( $sql, $fname );
2733         }
2734
2735         /**
2736          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2737          * into another table.
2738          *
2739          * @param string $destTable The table name to insert into
2740          * @param string|array $srcTable May be either a table name, or an array of table names
2741          *    to include in a join.
2742          *
2743          * @param array $varMap must be an associative array of the form
2744          *    array( 'dest1' => 'source1', ...). Source items may be literals
2745          *    rather than field names, but strings should be quoted with
2746          *    DatabaseBase::addQuotes()
2747          *
2748          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2749          *    the details of the format of condition arrays. May be "*" to copy the
2750          *    whole table.
2751          *
2752          * @param string $fname The function name of the caller, from __METHOD__
2753          *
2754          * @param array $insertOptions Options for the INSERT part of the query, see
2755          *    DatabaseBase::insert() for details.
2756          * @param array $selectOptions Options for the SELECT part of the query, see
2757          *    DatabaseBase::select() for details.
2758          *
2759          * @return ResultWrapper
2760          */
2761         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2762                 $fname = __METHOD__,
2763                 $insertOptions = array(), $selectOptions = array() )
2764         {
2765                 $destTable = $this->tableName( $destTable );
2766
2767                 if ( is_array( $insertOptions ) ) {
2768                         $insertOptions = implode( ' ', $insertOptions );
2769                 }
2770
2771                 if ( !is_array( $selectOptions ) ) {
2772                         $selectOptions = array( $selectOptions );
2773                 }
2774
2775                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2776
2777                 if ( is_array( $srcTable ) ) {
2778                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2779                 } else {
2780                         $srcTable = $this->tableName( $srcTable );
2781                 }
2782
2783                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2784                         " SELECT $startOpts " . implode( ',', $varMap ) .
2785                         " FROM $srcTable $useIndex ";
2786
2787                 if ( $conds != '*' ) {
2788                         if ( is_array( $conds ) ) {
2789                                 $conds = $this->makeList( $conds, LIST_AND );
2790                         }
2791                         $sql .= " WHERE $conds";
2792                 }
2793
2794                 $sql .= " $tailOpts";
2795
2796                 return $this->query( $sql, $fname );
2797         }
2798
2799         /**
2800          * Construct a LIMIT query with optional offset.  This is used for query
2801          * pages.  The SQL should be adjusted so that only the first $limit rows
2802          * are returned.  If $offset is provided as well, then the first $offset
2803          * rows should be discarded, and the next $limit rows should be returned.
2804          * If the result of the query is not ordered, then the rows to be returned
2805          * are theoretically arbitrary.
2806          *
2807          * $sql is expected to be a SELECT, if that makes a difference.
2808          *
2809          * The version provided by default works in MySQL and SQLite.  It will very
2810          * likely need to be overridden for most other DBMSes.
2811          *
2812          * @param string $sql SQL query we will append the limit too
2813          * @param $limit Integer the SQL limit
2814          * @param $offset Integer|bool the SQL offset (default false)
2815          *
2816          * @throws DBUnexpectedError
2817          * @return string
2818          */
2819         public function limitResult( $sql, $limit, $offset = false ) {
2820                 if ( !is_numeric( $limit ) ) {
2821                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2822                 }
2823                 return "$sql LIMIT "
2824                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2825                         . "{$limit} ";
2826         }
2827
2828         /**
2829          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2830          * within the UNION construct.
2831          * @return Boolean
2832          */
2833         public function unionSupportsOrderAndLimit() {
2834                 return true; // True for almost every DB supported
2835         }
2836
2837         /**
2838          * Construct a UNION query
2839          * This is used for providing overload point for other DB abstractions
2840          * not compatible with the MySQL syntax.
2841          * @param array $sqls SQL statements to combine
2842          * @param $all Boolean: use UNION ALL
2843          * @return String: SQL fragment
2844          */
2845         public function unionQueries( $sqls, $all ) {
2846                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2847                 return '(' . implode( $glue, $sqls ) . ')';
2848         }
2849
2850         /**
2851          * Returns an SQL expression for a simple conditional.  This doesn't need
2852          * to be overridden unless CASE isn't supported in your DBMS.
2853          *
2854          * @param string|array $cond SQL expression which will result in a boolean value
2855          * @param string $trueVal SQL expression to return if true
2856          * @param string $falseVal SQL expression to return if false
2857          * @return String: SQL fragment
2858          */
2859         public function conditional( $cond, $trueVal, $falseVal ) {
2860                 if ( is_array( $cond ) ) {
2861                         $cond = $this->makeList( $cond, LIST_AND );
2862                 }
2863                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2864         }
2865
2866         /**
2867          * Returns a comand for str_replace function in SQL query.
2868          * Uses REPLACE() in MySQL
2869          *
2870          * @param string $orig column to modify
2871          * @param string $old column to seek
2872          * @param string $new column to replace with
2873          *
2874          * @return string
2875          */
2876         public function strreplace( $orig, $old, $new ) {
2877                 return "REPLACE({$orig}, {$old}, {$new})";
2878         }
2879
2880         /**
2881          * Determines how long the server has been up
2882          * STUB
2883          *
2884          * @return int
2885          */
2886         public function getServerUptime() {
2887                 return 0;
2888         }
2889
2890         /**
2891          * Determines if the last failure was due to a deadlock
2892          * STUB
2893          *
2894          * @return bool
2895          */
2896         public function wasDeadlock() {
2897                 return false;
2898         }
2899
2900         /**
2901          * Determines if the last failure was due to a lock timeout
2902          * STUB
2903          *
2904          * @return bool
2905          */
2906         public function wasLockTimeout() {
2907                 return false;
2908         }
2909
2910         /**
2911          * Determines if the last query error was something that should be dealt
2912          * with by pinging the connection and reissuing the query.
2913          * STUB
2914          *
2915          * @return bool
2916          */
2917         public function wasErrorReissuable() {
2918                 return false;
2919         }
2920
2921         /**
2922          * Determines if the last failure was due to the database being read-only.
2923          * STUB
2924          *
2925          * @return bool
2926          */
2927         public function wasReadOnlyError() {
2928                 return false;
2929         }
2930
2931         /**
2932          * Perform a deadlock-prone transaction.
2933          *
2934          * This function invokes a callback function to perform a set of write
2935          * queries. If a deadlock occurs during the processing, the transaction
2936          * will be rolled back and the callback function will be called again.
2937          *
2938          * Usage:
2939          *   $dbw->deadlockLoop( callback, ... );
2940          *
2941          * Extra arguments are passed through to the specified callback function.
2942          *
2943          * Returns whatever the callback function returned on its successful,
2944          * iteration, or false on error, for example if the retry limit was
2945          * reached.
2946          *
2947          * @return bool
2948          */
2949         public function deadlockLoop() {
2950                 $this->begin( __METHOD__ );
2951                 $args = func_get_args();
2952                 $function = array_shift( $args );
2953                 $oldIgnore = $this->ignoreErrors( true );
2954                 $tries = self::DEADLOCK_TRIES;
2955
2956                 if ( is_array( $function ) ) {
2957                         $fname = $function[0];
2958                 } else {
2959                         $fname = $function;
2960                 }
2961
2962                 do {
2963                         $retVal = call_user_func_array( $function, $args );
2964                         $error = $this->lastError();
2965                         $errno = $this->lastErrno();
2966                         $sql = $this->lastQuery();
2967
2968                         if ( $errno ) {
2969                                 if ( $this->wasDeadlock() ) {
2970                                         # Retry
2971                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
2972                                 } else {
2973                                         $this->reportQueryError( $error, $errno, $sql, $fname );
2974                                 }
2975                         }
2976                 } while ( $this->wasDeadlock() && --$tries > 0 );
2977
2978                 $this->ignoreErrors( $oldIgnore );
2979
2980                 if ( $tries <= 0 ) {
2981                         $this->rollback( __METHOD__ );
2982                         $this->reportQueryError( $error, $errno, $sql, $fname );
2983                         return false;
2984                 } else {
2985                         $this->commit( __METHOD__ );
2986                         return $retVal;
2987                 }
2988         }
2989
2990         /**
2991          * Wait for the slave to catch up to a given master position.
2992          *
2993          * @param $pos DBMasterPos object
2994          * @param $timeout Integer: the maximum number of seconds to wait for
2995          *   synchronisation
2996          *
2997          * @return integer: zero if the slave was past that position already,
2998          *   greater than zero if we waited for some period of time, less than
2999          *   zero if we timed out.
3000          */
3001         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3002                 wfProfileIn( __METHOD__ );
3003
3004                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3005                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
3006
3007                         if ( $wait > $timeout * 1e6 ) {
3008                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
3009                                 wfProfileOut( __METHOD__ );
3010                                 return -1;
3011                         } elseif ( $wait > 0 ) {
3012                                 wfDebug( "Fake slave waiting $wait us\n" );
3013                                 usleep( $wait );
3014                                 wfProfileOut( __METHOD__ );
3015                                 return 1;
3016                         } else {
3017                                 wfDebug( "Fake slave up to date ($wait us)\n" );
3018                                 wfProfileOut( __METHOD__ );
3019                                 return 0;
3020                         }
3021                 }
3022
3023                 wfProfileOut( __METHOD__ );
3024
3025                 # Real waits are implemented in the subclass.
3026                 return 0;
3027         }
3028
3029         /**
3030          * Get the replication position of this slave
3031          *
3032          * @return DBMasterPos, or false if this is not a slave.
3033          */
3034         public function getSlavePos() {
3035                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3036                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
3037                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
3038                         return $pos;
3039                 } else {
3040                         # Stub
3041                         return false;
3042                 }
3043         }
3044
3045         /**
3046          * Get the position of this master
3047          *
3048          * @return DBMasterPos, or false if this is not a master
3049          */
3050         public function getMasterPos() {
3051                 if ( $this->mFakeMaster ) {
3052                         return new MySQLMasterPos( 'fake', microtime( true ) );
3053                 } else {
3054                         return false;
3055                 }
3056         }
3057
3058         /**
3059          * Run an anonymous function as soon as there is no transaction pending.
3060          * If there is a transaction and it is rolled back, then the callback is cancelled.
3061          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
3062          * Callbacks must commit any transactions that they begin.
3063          *
3064          * This is useful for updates to different systems or when separate transactions are needed.
3065          * For example, one might want to enqueue jobs into a system outside the database, but only
3066          * after the database is updated so that the jobs will see the data when they actually run.
3067          * It can also be used for updates that easily cause deadlocks if locks are held too long.
3068          *
3069          * @param callable $callback
3070          * @since 1.20
3071          */
3072         final public function onTransactionIdle( $callback ) {
3073                 $this->mTrxIdleCallbacks[] = $callback;
3074                 if ( !$this->mTrxLevel ) {
3075                         $this->runOnTransactionIdleCallbacks();
3076                 }
3077         }
3078
3079         /**
3080          * Run an anonymous function before the current transaction commits or now if there is none.
3081          * If there is a transaction and it is rolled back, then the callback is cancelled.
3082          * Callbacks must not start nor commit any transactions.
3083          *
3084          * This is useful for updates that easily cause deadlocks if locks are held too long
3085          * but where atomicity is strongly desired for these updates and some related updates.
3086          *
3087          * @param callable $callback
3088          * @since 1.22
3089          */
3090         final public function onTransactionPreCommitOrIdle( $callback ) {
3091                 if ( $this->mTrxLevel ) {
3092                         $this->mTrxPreCommitCallbacks[] = $callback;
3093                 } else {
3094                         $this->onTransactionIdle( $callback ); // this will trigger immediately
3095                 }
3096         }
3097
3098         /**
3099          * Actually any "on transaction idle" callbacks.
3100          *
3101          * @since 1.20
3102          */
3103         protected function runOnTransactionIdleCallbacks() {
3104                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
3105
3106                 $e = null; // last exception
3107                 do { // callbacks may add callbacks :)
3108                         $callbacks = $this->mTrxIdleCallbacks;
3109                         $this->mTrxIdleCallbacks = array(); // recursion guard
3110                         foreach ( $callbacks as $callback ) {
3111                                 try {
3112                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
3113                                         $callback();
3114                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3115                                 } catch ( Exception $e ) {
3116                                 }
3117                         }
3118                 } while ( count( $this->mTrxIdleCallbacks ) );
3119
3120                 if ( $e instanceof Exception ) {
3121                         throw $e; // re-throw any last exception
3122                 }
3123         }
3124
3125         /**
3126          * Actually any "on transaction pre-commit" callbacks.
3127          *
3128          * @since 1.22
3129          */
3130         protected function runOnTransactionPreCommitCallbacks() {
3131                 $e = null; // last exception
3132                 do { // callbacks may add callbacks :)
3133                         $callbacks = $this->mTrxPreCommitCallbacks;
3134                         $this->mTrxPreCommitCallbacks = array(); // recursion guard
3135                         foreach ( $callbacks as $callback ) {
3136                                 try {
3137                                         $callback();
3138                                 } catch ( Exception $e ) {}
3139                         }
3140                 } while ( count( $this->mTrxPreCommitCallbacks ) );
3141
3142                 if ( $e instanceof Exception ) {
3143                         throw $e; // re-throw any last exception
3144                 }
3145         }
3146
3147         /**
3148          * Begin a transaction. If a transaction is already in progress, that transaction will be committed before the
3149          * new transaction is started.
3150          *
3151          * Note that when the DBO_TRX flag is set (which is usually the case for web requests, but not for maintenance scripts),
3152          * any previous database query will have started a transaction automatically.
3153          *
3154          * Nesting of transactions is not supported. Attempts to nest transactions will cause a warning, unless the current
3155          * transaction was started automatically because of the DBO_TRX flag.
3156          *
3157          * @param $fname string
3158          */
3159         final public function begin( $fname = __METHOD__ ) {
3160                 global $wgDebugDBTransactions;
3161
3162                 if ( $this->mTrxLevel ) { // implicit commit
3163                         if ( !$this->mTrxAutomatic ) {
3164                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3165                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3166                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3167                                         " performing implicit commit!";
3168                                 wfWarn( $msg );
3169                                 wfLogDBError( $msg );
3170                         } else {
3171                                 // if the transaction was automatic and has done write operations,
3172                                 // log it if $wgDebugDBTransactions is enabled.
3173                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3174                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3175                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3176                                         );
3177                                 }
3178                         }
3179
3180                         $this->runOnTransactionPreCommitCallbacks();
3181                         $this->doCommit( $fname );
3182                         if ( $this->mTrxDoneWrites ) {
3183                                 Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3184                         }
3185                         $this->runOnTransactionIdleCallbacks();
3186                 }
3187
3188                 $this->doBegin( $fname );
3189                 $this->mTrxFname = $fname;
3190                 $this->mTrxDoneWrites = false;
3191                 $this->mTrxAutomatic = false;
3192         }
3193
3194         /**
3195          * Issues the BEGIN command to the database server.
3196          *
3197          * @see DatabaseBase::begin()
3198          * @param type $fname
3199          */
3200         protected function doBegin( $fname ) {
3201                 $this->query( 'BEGIN', $fname );
3202                 $this->mTrxLevel = 1;
3203         }
3204
3205         /**
3206          * Commits a transaction previously started using begin().
3207          * If no transaction is in progress, a warning is issued.
3208          *
3209          * Nesting of transactions is not supported.
3210          *
3211          * @param $fname string
3212          * @param string $flush Flush flag, set to 'flush' to disable warnings about explicitly committing implicit
3213          *        transactions, or calling commit when no transaction is in progress.
3214          *        This will silently break any ongoing explicit transaction. Only set the flush flag if you are sure
3215          *        that it is safe to ignore these warnings in your context.
3216          */
3217         final public function commit( $fname = __METHOD__, $flush = '' ) {
3218                 if ( $flush != 'flush' ) {
3219                         if ( !$this->mTrxLevel ) {
3220                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3221                         } elseif ( $this->mTrxAutomatic ) {
3222                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3223                         }
3224                 } else {
3225                         if ( !$this->mTrxLevel ) {
3226                                 return; // nothing to do
3227                         } elseif ( !$this->mTrxAutomatic ) {
3228                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3229                         }
3230                 }
3231
3232                 $this->runOnTransactionPreCommitCallbacks();
3233                 $this->doCommit( $fname );
3234                 if ( $this->mTrxDoneWrites ) {
3235                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3236                 }
3237                 $this->runOnTransactionIdleCallbacks();
3238         }
3239
3240         /**
3241          * Issues the COMMIT command to the database server.
3242          *
3243          * @see DatabaseBase::commit()
3244          * @param type $fname
3245          */
3246         protected function doCommit( $fname ) {
3247                 if ( $this->mTrxLevel ) {
3248                         $this->query( 'COMMIT', $fname );
3249                         $this->mTrxLevel = 0;
3250                 }
3251         }
3252
3253         /**
3254          * Rollback a transaction previously started using begin().
3255          * If no transaction is in progress, a warning is issued.
3256          *
3257          * No-op on non-transactional databases.
3258          *
3259          * @param $fname string
3260          */
3261         final public function rollback( $fname = __METHOD__ ) {
3262                 if ( !$this->mTrxLevel ) {
3263                         wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3264                 }
3265                 $this->doRollback( $fname );
3266                 $this->mTrxIdleCallbacks = array(); // cancel
3267                 $this->mTrxPreCommitCallbacks = array(); // cancel
3268                 if ( $this->mTrxDoneWrites ) {
3269                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3270                 }
3271         }
3272
3273         /**
3274          * Issues the ROLLBACK command to the database server.
3275          *
3276          * @see DatabaseBase::rollback()
3277          * @param type $fname
3278          */
3279         protected function doRollback( $fname ) {
3280                 if ( $this->mTrxLevel ) {
3281                         $this->query( 'ROLLBACK', $fname, true );
3282                         $this->mTrxLevel = 0;
3283                 }
3284         }
3285
3286         /**
3287          * Creates a new table with structure copied from existing table
3288          * Note that unlike most database abstraction functions, this function does not
3289          * automatically append database prefix, because it works at a lower
3290          * abstraction level.
3291          * The table names passed to this function shall not be quoted (this
3292          * function calls addIdentifierQuotes when needed).
3293          *
3294          * @param string $oldName name of table whose structure should be copied
3295          * @param string $newName name of table to be created
3296          * @param $temporary Boolean: whether the new table should be temporary
3297          * @param string $fname calling function name
3298          * @throws MWException
3299          * @return Boolean: true if operation was successful
3300          */
3301         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3302                 $fname = __METHOD__
3303         ) {
3304                 throw new MWException(
3305                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3306         }
3307
3308         /**
3309          * List all tables on the database
3310          *
3311          * @param string $prefix Only show tables with this prefix, e.g. mw_
3312          * @param string $fname calling function name
3313          * @throws MWException
3314          */
3315         function listTables( $prefix = null, $fname = __METHOD__ ) {
3316                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3317         }
3318
3319         /**
3320          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3321          * to the format used for inserting into timestamp fields in this DBMS.
3322          *
3323          * The result is unquoted, and needs to be passed through addQuotes()
3324          * before it can be included in raw SQL.
3325          *
3326          * @param $ts string|int
3327          *
3328          * @return string
3329          */
3330         public function timestamp( $ts = 0 ) {
3331                 return wfTimestamp( TS_MW, $ts );
3332         }
3333
3334         /**
3335          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3336          * to the format used for inserting into timestamp fields in this DBMS. If
3337          * NULL is input, it is passed through, allowing NULL values to be inserted
3338          * into timestamp fields.
3339          *
3340          * The result is unquoted, and needs to be passed through addQuotes()
3341          * before it can be included in raw SQL.
3342          *
3343          * @param $ts string|int
3344          *
3345          * @return string
3346          */
3347         public function timestampOrNull( $ts = null ) {
3348                 if ( is_null( $ts ) ) {
3349                         return null;
3350                 } else {
3351                         return $this->timestamp( $ts );
3352                 }
3353         }
3354
3355         /**
3356          * Take the result from a query, and wrap it in a ResultWrapper if
3357          * necessary. Boolean values are passed through as is, to indicate success
3358          * of write queries or failure.
3359          *
3360          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3361          * resource, and it was necessary to call this function to convert it to
3362          * a wrapper. Nowadays, raw database objects are never exposed to external
3363          * callers, so this is unnecessary in external code. For compatibility with
3364          * old code, ResultWrapper objects are passed through unaltered.
3365          *
3366          * @param $result bool|ResultWrapper
3367          *
3368          * @return bool|ResultWrapper
3369          */
3370         public function resultObject( $result ) {
3371                 if ( empty( $result ) ) {
3372                         return false;
3373                 } elseif ( $result instanceof ResultWrapper ) {
3374                         return $result;
3375                 } elseif ( $result === true ) {
3376                         // Successful write query
3377                         return $result;
3378                 } else {
3379                         return new ResultWrapper( $this, $result );
3380                 }
3381         }
3382
3383         /**
3384          * Ping the server and try to reconnect if it there is no connection
3385          *
3386          * @return bool Success or failure
3387          */
3388         public function ping() {
3389                 # Stub.  Not essential to override.
3390                 return true;
3391         }
3392
3393         /**
3394          * Get slave lag. Currently supported only by MySQL.
3395          *
3396          * Note that this function will generate a fatal error on many
3397          * installations. Most callers should use LoadBalancer::safeGetLag()
3398          * instead.
3399          *
3400          * @return int Database replication lag in seconds
3401          */
3402         public function getLag() {
3403                 return intval( $this->mFakeSlaveLag );
3404         }
3405
3406         /**
3407          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3408          *
3409          * @return int
3410          */
3411         function maxListLen() {
3412                 return 0;
3413         }
3414
3415         /**
3416          * Some DBMSs have a special format for inserting into blob fields, they
3417          * don't allow simple quoted strings to be inserted. To insert into such
3418          * a field, pass the data through this function before passing it to
3419          * DatabaseBase::insert().
3420          * @param $b string
3421          * @return string
3422          */
3423         public function encodeBlob( $b ) {
3424                 return $b;
3425         }
3426
3427         /**
3428          * Some DBMSs return a special placeholder object representing blob fields
3429          * in result objects. Pass the object through this function to return the
3430          * original string.
3431          * @param $b string
3432          * @return string
3433          */
3434         public function decodeBlob( $b ) {
3435                 return $b;
3436         }
3437
3438         /**
3439          * Override database's default behavior. $options include:
3440          *     'connTimeout' : Set the connection timeout value in seconds.
3441          *                     May be useful for very long batch queries such as
3442          *                     full-wiki dumps, where a single query reads out over
3443          *                     hours or days.
3444          *
3445          * @param $options Array
3446          * @return void
3447          */
3448         public function setSessionOptions( array $options ) {
3449         }
3450
3451         /**
3452          * Read and execute SQL commands from a file.
3453          *
3454          * Returns true on success, error string or exception on failure (depending
3455          * on object's error ignore settings).
3456          *
3457          * @param string $filename File name to open
3458          * @param bool|callable $lineCallback Optional function called before reading each line
3459          * @param bool|callable $resultCallback Optional function called for each MySQL result
3460          * @param bool|string $fname Calling function name or false if name should be
3461          *      generated dynamically using $filename
3462          * @param bool|callable $inputCallback Callback: Optional function called for each complete line sent
3463          * @throws MWException
3464          * @throws Exception|MWException
3465          * @return bool|string
3466          */
3467         public function sourceFile(
3468                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3469         ) {
3470                 wfSuppressWarnings();
3471                 $fp = fopen( $filename, 'r' );
3472                 wfRestoreWarnings();
3473
3474                 if ( false === $fp ) {
3475                         throw new MWException( "Could not open \"{$filename}\".\n" );
3476                 }
3477
3478                 if ( !$fname ) {
3479                         $fname = __METHOD__ . "( $filename )";
3480                 }
3481
3482                 try {
3483                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3484                 }
3485                 catch ( MWException $e ) {
3486                         fclose( $fp );
3487                         throw $e;
3488                 }
3489
3490                 fclose( $fp );
3491
3492                 return $error;
3493         }
3494
3495         /**
3496          * Get the full path of a patch file. Originally based on archive()
3497          * from updaters.inc. Keep in mind this always returns a patch, as
3498          * it fails back to MySQL if no DB-specific patch can be found
3499          *
3500          * @param string $patch The name of the patch, like patch-something.sql
3501          * @return String Full path to patch file
3502          */
3503         public function patchPath( $patch ) {
3504                 global $IP;
3505
3506                 $dbType = $this->getType();
3507                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3508                         return "$IP/maintenance/$dbType/archives/$patch";
3509                 } else {
3510                         return "$IP/maintenance/archives/$patch";
3511                 }
3512         }
3513
3514         /**
3515          * Set variables to be used in sourceFile/sourceStream, in preference to the
3516          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3517          * all. If it's set to false, $GLOBALS will be used.
3518          *
3519          * @param bool|array $vars mapping variable name to value.
3520          */
3521         public function setSchemaVars( $vars ) {
3522                 $this->mSchemaVars = $vars;
3523         }
3524
3525         /**
3526          * Read and execute commands from an open file handle.
3527          *
3528          * Returns true on success, error string or exception on failure (depending
3529          * on object's error ignore settings).
3530          *
3531          * @param $fp Resource: File handle
3532          * @param $lineCallback Callback: Optional function called before reading each query
3533          * @param $resultCallback Callback: Optional function called for each MySQL result
3534          * @param string $fname Calling function name
3535          * @param $inputCallback Callback: Optional function called for each complete query sent
3536          * @return bool|string
3537          */
3538         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3539                 $fname = __METHOD__, $inputCallback = false )
3540         {
3541                 $cmd = '';
3542
3543                 while ( !feof( $fp ) ) {
3544                         if ( $lineCallback ) {
3545                                 call_user_func( $lineCallback );
3546                         }
3547
3548                         $line = trim( fgets( $fp ) );
3549
3550                         if ( $line == '' ) {
3551                                 continue;
3552                         }
3553
3554                         if ( '-' == $line[0] && '-' == $line[1] ) {
3555                                 continue;
3556                         }
3557
3558                         if ( $cmd != '' ) {
3559                                 $cmd .= ' ';
3560                         }
3561
3562                         $done = $this->streamStatementEnd( $cmd, $line );
3563
3564                         $cmd .= "$line\n";
3565
3566                         if ( $done || feof( $fp ) ) {
3567                                 $cmd = $this->replaceVars( $cmd );
3568
3569                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3570                                         $res = $this->query( $cmd, $fname );
3571
3572                                         if ( $resultCallback ) {
3573                                                 call_user_func( $resultCallback, $res, $this );
3574                                         }
3575
3576                                         if ( false === $res ) {
3577                                                 $err = $this->lastError();
3578                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3579                                         }
3580                                 }
3581                                 $cmd = '';
3582                         }
3583                 }
3584
3585                 return true;
3586         }
3587
3588         /**
3589          * Called by sourceStream() to check if we've reached a statement end
3590          *
3591          * @param string $sql SQL assembled so far
3592          * @param string $newLine New line about to be added to $sql
3593          * @return Bool Whether $newLine contains end of the statement
3594          */
3595         public function streamStatementEnd( &$sql, &$newLine ) {
3596                 if ( $this->delimiter ) {
3597                         $prev = $newLine;
3598                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3599                         if ( $newLine != $prev ) {
3600                                 return true;
3601                         }
3602                 }
3603                 return false;
3604         }
3605
3606         /**
3607          * Database independent variable replacement. Replaces a set of variables
3608          * in an SQL statement with their contents as given by $this->getSchemaVars().
3609          *
3610          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3611          *
3612          * - '{$var}' should be used for text and is passed through the database's
3613          *   addQuotes method.
3614          * - `{$var}` should be used for identifiers (eg: table and database names),
3615          *   it is passed through the database's addIdentifierQuotes method which
3616          *   can be overridden if the database uses something other than backticks.
3617          * - / *$var* / is just encoded, besides traditional table prefix and
3618          *   table options its use should be avoided.
3619          *
3620          * @param string $ins SQL statement to replace variables in
3621          * @return String The new SQL statement with variables replaced
3622          */
3623         protected function replaceSchemaVars( $ins ) {
3624                 $vars = $this->getSchemaVars();
3625                 foreach ( $vars as $var => $value ) {
3626                         // replace '{$var}'
3627                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3628                         // replace `{$var}`
3629                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3630                         // replace /*$var*/
3631                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3632                 }
3633                 return $ins;
3634         }
3635
3636         /**
3637          * Replace variables in sourced SQL
3638          *
3639          * @param $ins string
3640          *
3641          * @return string
3642          */
3643         protected function replaceVars( $ins ) {
3644                 $ins = $this->replaceSchemaVars( $ins );
3645
3646                 // Table prefixes
3647                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3648                         array( $this, 'tableNameCallback' ), $ins );
3649
3650                 // Index names
3651                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3652                         array( $this, 'indexNameCallback' ), $ins );
3653
3654                 return $ins;
3655         }
3656
3657         /**
3658          * Get schema variables. If none have been set via setSchemaVars(), then
3659          * use some defaults from the current object.
3660          *
3661          * @return array
3662          */
3663         protected function getSchemaVars() {
3664                 if ( $this->mSchemaVars ) {
3665                         return $this->mSchemaVars;
3666                 } else {
3667                         return $this->getDefaultSchemaVars();
3668                 }
3669         }
3670
3671         /**
3672          * Get schema variables to use if none have been set via setSchemaVars().
3673          *
3674          * Override this in derived classes to provide variables for tables.sql
3675          * and SQL patch files.
3676          *
3677          * @return array
3678          */
3679         protected function getDefaultSchemaVars() {
3680                 return array();
3681         }
3682
3683         /**
3684          * Table name callback
3685          *
3686          * @param $matches array
3687          *
3688          * @return string
3689          */
3690         protected function tableNameCallback( $matches ) {
3691                 return $this->tableName( $matches[1] );
3692         }
3693
3694         /**
3695          * Index name callback
3696          *
3697          * @param $matches array
3698          *
3699          * @return string
3700          */
3701         protected function indexNameCallback( $matches ) {
3702                 return $this->indexName( $matches[1] );
3703         }
3704
3705         /**
3706          * Check to see if a named lock is available. This is non-blocking.
3707          *
3708          * @param string $lockName name of lock to poll
3709          * @param string $method name of method calling us
3710          * @return Boolean
3711          * @since 1.20
3712          */
3713         public function lockIsFree( $lockName, $method ) {
3714                 return true;
3715         }
3716
3717         /**
3718          * Acquire a named lock
3719          *
3720          * Abstracted from Filestore::lock() so child classes can implement for
3721          * their own needs.
3722          *
3723          * @param string $lockName name of lock to aquire
3724          * @param string $method name of method calling us
3725          * @param $timeout Integer: timeout
3726          * @return Boolean
3727          */
3728         public function lock( $lockName, $method, $timeout = 5 ) {
3729                 return true;
3730         }
3731
3732         /**
3733          * Release a lock.
3734          *
3735          * @param string $lockName Name of lock to release
3736          * @param string $method Name of method calling us
3737          *
3738          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3739          * by this thread (in which case the lock is not released), and NULL if the named
3740          * lock did not exist
3741          */
3742         public function unlock( $lockName, $method ) {
3743                 return true;
3744         }
3745
3746         /**
3747          * Lock specific tables
3748          *
3749          * @param array $read of tables to lock for read access
3750          * @param array $write of tables to lock for write access
3751          * @param string $method name of caller
3752          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
3753          *
3754          * @return bool
3755          */
3756         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3757                 return true;
3758         }
3759
3760         /**
3761          * Unlock specific tables
3762          *
3763          * @param string $method the caller
3764          *
3765          * @return bool
3766          */
3767         public function unlockTables( $method ) {
3768                 return true;
3769         }
3770
3771         /**
3772          * Delete a table
3773          * @param $tableName string
3774          * @param $fName string
3775          * @return bool|ResultWrapper
3776          * @since 1.18
3777          */
3778         public function dropTable( $tableName, $fName = __METHOD__ ) {
3779                 if ( !$this->tableExists( $tableName, $fName ) ) {
3780                         return false;
3781                 }
3782                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3783                 if ( $this->cascadingDeletes() ) {
3784                         $sql .= " CASCADE";
3785                 }
3786                 return $this->query( $sql, $fName );
3787         }
3788
3789         /**
3790          * Get search engine class. All subclasses of this need to implement this
3791          * if they wish to use searching.
3792          *
3793          * @return String
3794          */
3795         public function getSearchEngine() {
3796                 return 'SearchEngineDummy';
3797         }
3798
3799         /**
3800          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3801          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3802          * because "i" sorts after all numbers.
3803          *
3804          * @return String
3805          */
3806         public function getInfinity() {
3807                 return 'infinity';
3808         }
3809
3810         /**
3811          * Encode an expiry time into the DBMS dependent format
3812          *
3813          * @param string $expiry timestamp for expiry, or the 'infinity' string
3814          * @return String
3815          */
3816         public function encodeExpiry( $expiry ) {
3817                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3818                         ? $this->getInfinity()
3819                         : $this->timestamp( $expiry );
3820         }
3821
3822         /**
3823          * Decode an expiry time into a DBMS independent format
3824          *
3825          * @param string $expiry DB timestamp field value for expiry
3826          * @param $format integer: TS_* constant, defaults to TS_MW
3827          * @return String
3828          */
3829         public function decodeExpiry( $expiry, $format = TS_MW ) {
3830                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3831                         ? 'infinity'
3832                         : wfTimestamp( $format, $expiry );
3833         }
3834
3835         /**
3836          * Allow or deny "big selects" for this session only. This is done by setting
3837          * the sql_big_selects session variable.
3838          *
3839          * This is a MySQL-specific feature.
3840          *
3841          * @param $value Mixed: true for allow, false for deny, or "default" to
3842          *   restore the initial value
3843          */
3844         public function setBigSelects( $value = true ) {
3845                 // no-op
3846         }
3847
3848         /**
3849          * @since 1.19
3850          */
3851         public function __toString() {
3852                 return (string)$this->mConn;
3853         }
3854
3855         public function __destruct() {
3856                 if ( count( $this->mTrxIdleCallbacks ) || count( $this->mTrxPreCommitCallbacks ) ) {
3857                         trigger_error( "Transaction idle or pre-commit callbacks still pending." ); // sanity
3858                 }
3859         }
3860 }