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 $mErrorCount = 0;
 247         protected $mLBInfo = array();
 248         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 249         protected $mDefaultBigSelects = null;
 250         protected $mSchemaVars = false;
 251
 252         protected $preparedArgs;
 253
 254         protected $htmlErrors;
 255
 256         protected $delimiter = ';';
 257
 258         /**
 259          * Either 1 if a transaction is active or 0 otherwise.
 260          * The other Trx fields may not be meaningfull if this is 0.
 261          *
 262          * @var int
 263          */
 264         protected $mTrxLevel = 0;
 265
 266         /**
 267          * Remembers the function name given for starting the most recent transaction via begin().
 268          * Used to provide additional context for error reporting.
 269          *
 270          * @var String
 271          * @see DatabaseBase::mTrxLevel
 272          */
 273         private $mTrxFname = null;
 274
 275         /**
 276          * Record if possible write queries were done in the last transaction started
 277          *
 278          * @var Bool
 279          * @see DatabaseBase::mTrxLevel
 280          */
 281         private $mTrxDoneWrites = false;
 282
 283         /**
 284          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 285          *
 286          * @var Bool
 287          * @see DatabaseBase::mTrxLevel
 288          */
 289         private $mTrxAutomatic = false;
 290
 291         /**
 292          * Array of levels of atomicity within transactions
 293          *
 294          * @var SplStack
 295          */
 296         private $mTrxAtomicLevels;
 297
 298         /**
 299          * Record if the current transaction was started implicitly by DatabaseBase::startAtomic
 300          *
 301          * @var Bool
 302          */
 303         private $mTrxAutomaticAtomic = false;
 304
 305         /**
 306          * @since 1.21
 307          * @var file handle for upgrade
 308          */
 309         protected $fileHandle = null;
 310
 311         /**
 312          * @since 1.22
 313          * @var Process cache of VIEWs names in the database
 314          */
 315         protected $allViews = null;
 316
 317 # ------------------------------------------------------------------------------
 318 # Accessors
 319 # ------------------------------------------------------------------------------
 320         # These optionally set a variable and return the previous state
 321
 322         /**
 323          * A string describing the current software version, and possibly
 324          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 325          * Use getServerVersion() to get machine-friendly information.
 326          *
 327          * @return string: Version information from the database server
 328          */
 329         public function getServerInfo() {
 330                 return $this->getServerVersion();
 331         }
 332
 333         /**
 334          * @return string: command delimiter used by this database engine
 335          */
 336         public function getDelimiter() {
 337                 return $this->delimiter;
 338         }
 339
 340         /**
 341          * Boolean, controls output of large amounts of debug information.
 342          * @param $debug bool|null
 343          *   - true to enable debugging
 344          *   - false to disable debugging
 345          *   - omitted or null to do nothing
 346          *
 347          * @return bool|null previous value of the flag
 348          */
 349         public function debug( $debug = null ) {
 350                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 351         }
 352
 353         /**
 354          * Turns buffering of SQL result sets on (true) or off (false). Default is
 355          * "on".
 356          *
 357          * Unbuffered queries are very troublesome in MySQL:
 358          *
 359          *   - If another query is executed while the first query is being read
 360          *     out, the first query is killed. This means you can't call normal
 361          *     MediaWiki functions while you are reading an unbuffered query result
 362          *     from a normal wfGetDB() connection.
 363          *
 364          *   - Unbuffered queries cause the MySQL server to use large amounts of
 365          *     memory and to hold broad locks which block other queries.
 366          *
 367          * If you want to limit client-side memory, it's almost always better to
 368          * split up queries into batches using a LIMIT clause than to switch off
 369          * buffering.
 370          *
 371          * @param $buffer null|bool
 372          *
 373          * @return null|bool The previous value of the flag
 374          */
 375         public function bufferResults( $buffer = null ) {
 376                 if ( is_null( $buffer ) ) {
 377                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 378                 } else {
 379                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 380                 }
 381         }
 382
 383         /**
 384          * Turns on (false) or off (true) the automatic generation and sending
 385          * of a "we're sorry, but there has been a database error" page on
 386          * database errors. Default is on (false). When turned off, the
 387          * code should use lastErrno() and lastError() to handle the
 388          * situation as appropriate.
 389          *
 390          * Do not use this function outside of the Database classes.
 391          *
 392          * @param $ignoreErrors bool|null
 393          *
 394          * @return bool The previous value of the flag.
 395          */
 396         public function ignoreErrors( $ignoreErrors = null ) {
 397                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 398         }
 399
 400         /**
 401          * Gets the current transaction level.
 402          *
 403          * Historically, transactions were allowed to be "nested". This is no
 404          * longer supported, so this function really only returns a boolean.
 405          *
 406          * @return int The previous value
 407          */
 408         public function trxLevel() {
 409                 return $this->mTrxLevel;
 410         }
 411
 412         /**
 413          * Get/set the number of errors logged. Only useful when errors are ignored
 414          * @param int $count The count to set, or omitted to leave it unchanged.
 415          * @return int The error count
 416          */
 417         public function errorCount( $count = null ) {
 418                 return wfSetVar( $this->mErrorCount, $count );
 419         }
 420
 421         /**
 422          * Get/set the table prefix.
 423          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 424          * @return string The previous table prefix.
 425          */
 426         public function tablePrefix( $prefix = null ) {
 427                 return wfSetVar( $this->mTablePrefix, $prefix );
 428         }
 429
 430         /**
 431          * Set the filehandle to copy write statements to.
 432          *
 433          * @param $fh filehandle
 434          */
 435         public function setFileHandle( $fh ) {
 436                 $this->fileHandle = $fh;
 437         }
 438
 439         /**
 440          * Get properties passed down from the server info array of the load
 441          * balancer.
 442          *
 443          * @param string $name The entry of the info array to get, or null to get the
 444          *   whole array
 445          *
 446          * @return LoadBalancer|null
 447          */
 448         public function getLBInfo( $name = null ) {
 449                 if ( is_null( $name ) ) {
 450                         return $this->mLBInfo;
 451                 } else {
 452                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 453                                 return $this->mLBInfo[$name];
 454                         } else {
 455                                 return null;
 456                         }
 457                 }
 458         }
 459
 460         /**
 461          * Set the LB info array, or a member of it. If called with one parameter,
 462          * the LB info array is set to that parameter. If it is called with two
 463          * parameters, the member with the given name is set to the given value.
 464          *
 465          * @param $name
 466          * @param $value
 467          */
 468         public function setLBInfo( $name, $value = null ) {
 469                 if ( is_null( $value ) ) {
 470                         $this->mLBInfo = $name;
 471                 } else {
 472                         $this->mLBInfo[$name] = $value;
 473                 }
 474         }
 475
 476         /**
 477          * Set lag time in seconds for a fake slave
 478          *
 479          * @param $lag int
 480          */
 481         public function setFakeSlaveLag( $lag ) {
 482                 $this->mFakeSlaveLag = $lag;
 483         }
 484
 485         /**
 486          * Make this connection a fake master
 487          *
 488          * @param $enabled bool
 489          */
 490         public function setFakeMaster( $enabled = true ) {
 491                 $this->mFakeMaster = $enabled;
 492         }
 493
 494         /**
 495          * Returns true if this database supports (and uses) cascading deletes
 496          *
 497          * @return bool
 498          */
 499         public function cascadingDeletes() {
 500                 return false;
 501         }
 502
 503         /**
 504          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 505          *
 506          * @return bool
 507          */
 508         public function cleanupTriggers() {
 509                 return false;
 510         }
 511
 512         /**
 513          * Returns true if this database is strict about what can be put into an IP field.
 514          * Specifically, it uses a NULL value instead of an empty string.
 515          *
 516          * @return bool
 517          */
 518         public function strictIPs() {
 519                 return false;
 520         }
 521
 522         /**
 523          * Returns true if this database uses timestamps rather than integers
 524          *
 525          * @return bool
 526          */
 527         public function realTimestamps() {
 528                 return false;
 529         }
 530
 531         /**
 532          * Returns true if this database does an implicit sort when doing GROUP BY
 533          *
 534          * @return bool
 535          */
 536         public function implicitGroupby() {
 537                 return true;
 538         }
 539
 540         /**
 541          * Returns true if this database does an implicit order by when the column has an index
 542          * For example: SELECT page_title FROM page LIMIT 1
 543          *
 544          * @return bool
 545          */
 546         public function implicitOrderby() {
 547                 return true;
 548         }
 549
 550         /**
 551          * Returns true if this database can do a native search on IP columns
 552          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 553          *
 554          * @return bool
 555          */
 556         public function searchableIPs() {
 557                 return false;
 558         }
 559
 560         /**
 561          * Returns true if this database can use functional indexes
 562          *
 563          * @return bool
 564          */
 565         public function functionalIndexes() {
 566                 return false;
 567         }
 568
 569         /**
 570          * Return the last query that went through DatabaseBase::query()
 571          * @return String
 572          */
 573         public function lastQuery() {
 574                 return $this->mLastQuery;
 575         }
 576
 577         /**
 578          * Returns true if the connection may have been used for write queries.
 579          * Should return true if unsure.
 580          *
 581          * @return bool
 582          */
 583         public function doneWrites() {
 584                 return $this->mDoneWrites;
 585         }
 586
 587         /**
 588          * Returns true if there is a transaction open with possible write
 589          * queries or transaction pre-commit/idle callbacks waiting on it to finish.
 590          *
 591          * @return bool
 592          */
 593         public function writesOrCallbacksPending() {
 594                 return $this->mTrxLevel && (
 595                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 596                 );
 597         }
 598
 599         /**
 600          * Is a connection to the database open?
 601          * @return Boolean
 602          */
 603         public function isOpen() {
 604                 return $this->mOpened;
 605         }
 606
 607         /**
 608          * Set a flag for this connection
 609          *
 610          * @param $flag Integer: DBO_* constants from Defines.php:
 611          *   - DBO_DEBUG: output some debug info (same as debug())
 612          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 613          *   - DBO_TRX: automatically start transactions
 614          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 615          *       and removes it in command line mode
 616          *   - DBO_PERSISTENT: use persistant database connection
 617          */
 618         public function setFlag( $flag ) {
 619                 global $wgDebugDBTransactions;
 620                 $this->mFlags |= $flag;
 621                 if ( ( $flag & DBO_TRX ) & $wgDebugDBTransactions ) {
 622                         wfDebug( "Implicit transactions are now  disabled.\n" );
 623                 }
 624         }
 625
 626         /**
 627          * Clear a flag for this connection
 628          *
 629          * @param $flag: same as setFlag()'s $flag param
 630          */
 631         public function clearFlag( $flag ) {
 632                 global $wgDebugDBTransactions;
 633                 $this->mFlags &= ~$flag;
 634                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 635                         wfDebug( "Implicit transactions are now disabled.\n" );
 636                 }
 637         }
 638
 639         /**
 640          * Returns a boolean whether the flag $flag is set for this connection
 641          *
 642          * @param $flag: same as setFlag()'s $flag param
 643          * @return Boolean
 644          */
 645         public function getFlag( $flag ) {
 646                 return !!( $this->mFlags & $flag );
 647         }
 648
 649         /**
 650          * General read-only accessor
 651          *
 652          * @param $name string
 653          *
 654          * @return string
 655          */
 656         public function getProperty( $name ) {
 657                 return $this->$name;
 658         }
 659
 660         /**
 661          * @return string
 662          */
 663         public function getWikiID() {
 664                 if ( $this->mTablePrefix ) {
 665                         return "{$this->mDBname}-{$this->mTablePrefix}";
 666                 } else {
 667                         return $this->mDBname;
 668                 }
 669         }
 670
 671         /**
 672          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 673          *
 674          * @return string
 675          */
 676         public function getSchemaPath() {
 677                 global $IP;
 678                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 679                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 680                 } else {
 681                         return "$IP/maintenance/tables.sql";
 682                 }
 683         }
 684
 685 # ------------------------------------------------------------------------------
 686 # Other functions
 687 # ------------------------------------------------------------------------------
 688
 689         /**
 690          * Constructor.
 691          *
 692          * FIXME: It is possible to construct a Database object with no associated
 693          * connection object, by specifying no parameters to __construct(). This
 694          * feature is deprecated and should be removed.
 695          *
 696          * DatabaseBase subclasses should not be constructed directly in external
 697          * code. DatabaseBase::factory() should be used instead.
 698          *
 699          * @param array Parameters passed from DatabaseBase::factory()
 700          */
 701         function __construct( $params = null ) {
 702                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 703
 704                 $this->mTrxAtomicLevels = new SplStack;
 705
 706                 if ( is_array( $params ) ) { // MW 1.22
 707                         $server = $params['host'];
 708                         $user = $params['user'];
 709                         $password = $params['password'];
 710                         $dbName = $params['dbname'];
 711                         $flags = $params['flags'];
 712                         $tablePrefix = $params['tablePrefix'];
 713                         $foreign = $params['foreign'];
 714                 } else { // legacy calling pattern
 715                         wfDeprecated( __METHOD__ . " method called without parameter array.", "1.23" );
 716                         $args = func_get_args();
 717                         $server = isset( $args[0] ) ? $args[0] : false;
 718                         $user = isset( $args[1] ) ? $args[1] : false;
 719                         $password = isset( $args[2] ) ? $args[2] : false;
 720                         $dbName = isset( $args[3] ) ? $args[3] : false;
 721                         $flags = isset( $args[4] ) ? $args[4] : 0;
 722                         $tablePrefix = isset( $args[5] ) ? $args[5] : 'get from global';
 723                         $foreign = isset( $args[6] ) ? $args[6] : false;
 724                 }
 725
 726                 $this->mFlags = $flags;
 727                 if ( $this->mFlags & DBO_DEFAULT ) {
 728                         if ( $wgCommandLineMode ) {
 729                                 $this->mFlags &= ~DBO_TRX;
 730                                 if ( $wgDebugDBTransactions ) {
 731                                         wfDebug( "Implicit transaction open disabled.\n" );
 732                                 }
 733                         } else {
 734                                 $this->mFlags |= DBO_TRX;
 735                                 if ( $wgDebugDBTransactions ) {
 736                                         wfDebug( "Implicit transaction open enabled.\n" );
 737                                 }
 738                         }
 739                 }
 740
 741                 /** Get the default table prefix*/
 742                 if ( $tablePrefix == 'get from global' ) {
 743                         $this->mTablePrefix = $wgDBprefix;
 744                 } else {
 745                         $this->mTablePrefix = $tablePrefix;
 746                 }
 747
 748                 $this->mForeign = $foreign;
 749
 750                 if ( $user ) {
 751                         $this->open( $server, $user, $password, $dbName );
 752                 }
 753         }
 754
 755         /**
 756          * Called by serialize. Throw an exception when DB connection is serialized.
 757          * This causes problems on some database engines because the connection is
 758          * not restored on unserialize.
 759          */
 760         public function __sleep() {
 761                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 762         }
 763
 764         /**
 765          * Given a DB type, construct the name of the appropriate child class of
 766          * DatabaseBase. This is designed to replace all of the manual stuff like:
 767          *      $class = 'Database' . ucfirst( strtolower( $dbType ) );
 768          * as well as validate against the canonical list of DB types we have
 769          *
 770          * This factory function is mostly useful for when you need to connect to a
 771          * database other than the MediaWiki default (such as for external auth,
 772          * an extension, et cetera). Do not use this to connect to the MediaWiki
 773          * database. Example uses in core:
 774          * @see LoadBalancer::reallyOpenConnection()
 775          * @see ForeignDBRepo::getMasterDB()
 776          * @see WebInstaller_DBConnect::execute()
 777          *
 778          * @since 1.18
 779          *
 780          * @param string $dbType A possible DB type
 781          * @param array $p An array of options to pass to the constructor.
 782          *    Valid options are: host, user, password, dbname, flags, tablePrefix, driver
 783          * @return DatabaseBase subclass or null
 784          */
 785         final public static function factory( $dbType, $p = array() ) {
 786                 $canonicalDBTypes = array(
 787                         'mysql'    => array( 'mysqli', 'mysql' ),
 788                         'postgres' => array(),
 789                         'sqlite'   => array(),
 790                         'oracle'   => array(),
 791                 );
 792
 793                 $driver = false;
 794                 $dbType = strtolower( $dbType );
 795                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 796                         $possibleDrivers = $canonicalDBTypes[$dbType];
 797                         if ( !empty( $p['driver'] ) ) {
 798                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 799                                         $driver = $p['driver'];
 800                                 } else {
 801                                         throw new MWException( __METHOD__ .
 802                                                 " cannot construct Database with type '$dbType' and driver '{$p['driver']}'" );
 803                                 }
 804                         } else {
 805                                 foreach ( $possibleDrivers as $posDriver ) {
 806                                         if ( extension_loaded( $posDriver ) ) {
 807                                                 $driver = $posDriver;
 808                                                 break;
 809                                         }
 810                                 }
 811                         }
 812                 } else {
 813                         $driver = $dbType;
 814                 }
 815                 if ( $driver === false ) {
 816                         throw new MWException( __METHOD__ .
 817                                 " no viable database extension found for type '$dbType'" );
 818                 }
 819
 820                 $class = 'Database' . ucfirst( $driver );
 821                 if ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 822                         $params = array(
 823                                 'host' => isset( $p['host'] ) ? $p['host'] : false,
 824                                 'user' => isset( $p['user'] ) ? $p['user'] : false,
 825                                 'password' => isset( $p['password'] ) ? $p['password'] : false,
 826                                 'dbname' => isset( $p['dbname'] ) ? $p['dbname'] : false,
 827                                 'flags' => isset( $p['flags'] ) ? $p['flags'] : 0,
 828                                 'tablePrefix' => isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global',
 829                                 'foreign' => isset( $p['foreign'] ) ? $p['foreign'] : false
 830                         );
 831                         return new $class( $params );
 832                 } else {
 833                         return null;
 834                 }
 835         }
 836
 837         protected function installErrorHandler() {
 838                 $this->mPHPError = false;
 839                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 840                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 841         }
 842
 843         /**
 844          * @return bool|string
 845          */
 846         protected function restoreErrorHandler() {
 847                 restore_error_handler();
 848                 if ( $this->htmlErrors !== false ) {
 849                         ini_set( 'html_errors', $this->htmlErrors );
 850                 }
 851                 if ( $this->mPHPError ) {
 852                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 853                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 854                         return $error;
 855                 } else {
 856                         return false;
 857                 }
 858         }
 859
 860         /**
 861          * @param $errno
 862          * @param $errstr
 863          * @access private
 864          */
 865         public function connectionErrorHandler( $errno, $errstr ) {
 866                 $this->mPHPError = $errstr;
 867         }
 868
 869         /**
 870          * Closes a database connection.
 871          * if it is open : commits any open transactions
 872          *
 873          * @throws MWException
 874          * @return Bool operation success. true if already closed.
 875          */
 876         public function close() {
 877                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 878                         throw new MWException( "Transaction idle callbacks still pending." );
 879                 }
 880                 $this->mOpened = false;
 881                 if ( $this->mConn ) {
 882                         if ( $this->trxLevel() ) {
 883                                 if ( !$this->mTrxAutomatic ) {
 884                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 885                                                 " performing implicit commit before closing connection!" );
 886                                 }
 887
 888                                 $this->commit( __METHOD__, 'flush' );
 889                         }
 890
 891                         $ret = $this->closeConnection();
 892                         $this->mConn = false;
 893                         return $ret;
 894                 } else {
 895                         return true;
 896                 }
 897         }
 898
 899         /**
 900          * Closes underlying database connection
 901          * @since 1.20
 902          * @return bool: Whether connection was closed successfully
 903          */
 904         abstract protected function closeConnection();
 905
 906         /**
 907          * @param string $error fallback error message, used if none is given by DB
 908          * @throws DBConnectionError
 909          */
 910         function reportConnectionError( $error = 'Unknown error' ) {
 911                 $myError = $this->lastError();
 912                 if ( $myError ) {
 913                         $error = $myError;
 914                 }
 915
 916                 # New method
 917                 throw new DBConnectionError( $this, $error );
 918         }
 919
 920         /**
 921          * The DBMS-dependent part of query()
 922          *
 923          * @param  $sql String: SQL query.
 924          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 925          */
 926         abstract protected function doQuery( $sql );
 927
 928         /**
 929          * Determine whether a query writes to the DB.
 930          * Should return true if unsure.
 931          *
 932          * @param $sql string
 933          *
 934          * @return bool
 935          */
 936         public function isWriteQuery( $sql ) {
 937                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 938         }
 939
 940         /**
 941          * Run an SQL query and return the result. Normally throws a DBQueryError
 942          * on failure. If errors are ignored, returns false instead.
 943          *
 944          * In new code, the query wrappers select(), insert(), update(), delete(),
 945          * etc. should be used where possible, since they give much better DBMS
 946          * independence and automatically quote or validate user input in a variety
 947          * of contexts. This function is generally only useful for queries which are
 948          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 949          * as CREATE TABLE.
 950          *
 951          * However, the query wrappers themselves should call this function.
 952          *
 953          * @param  $sql        String: SQL query
 954          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 955          *     comment (you can use __METHOD__ or add some extra info)
 956          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 957          *     maybe best to catch the exception instead?
 958          * @throws MWException
 959          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 960          *     for a successful read query, or false on failure if $tempIgnore set
 961          */
 962         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 963                 global $wgUser, $wgDebugDBTransactions;
 964
 965                 $this->mLastQuery = $sql;
 966                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 967                         # Set a flag indicating that writes have been done
 968                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 969                         $this->mDoneWrites = true;
 970                 }
 971
 972                 # Add a comment for easy SHOW PROCESSLIST interpretation
 973                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 974                         $userName = $wgUser->getName();
 975                         if ( mb_strlen( $userName ) > 15 ) {
 976                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 977                         }
 978                         $userName = str_replace( '/', '', $userName );
 979                 } else {
 980                         $userName = '';
 981                 }
 982
 983                 // Add trace comment to the begin of the sql string, right after the operator.
 984                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 985                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 986
 987                 # If DBO_TRX is set, start a transaction
 988                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 989                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' )
 990                 {
 991                         # Avoid establishing transactions for SHOW and SET statements too -
 992                         # that would delay transaction initializations to once connection
 993                         # is really used by application
 994                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 995                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 996                                 if ( $wgDebugDBTransactions ) {
 997                                         wfDebug( "Implicit transaction start.\n" );
 998                                 }
 999                                 $this->begin( __METHOD__ . " ($fname)" );
1000                                 $this->mTrxAutomatic = true;
1001                         }
1002                 }
1003
1004                 # Keep track of whether the transaction has write queries pending
1005                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
1006                         $this->mTrxDoneWrites = true;
1007                         Profiler::instance()->transactionWritingIn( $this->mServer, $this->mDBname );
1008                 }
1009
1010                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1011                 if ( !Profiler::instance()->isStub() ) {
1012                         # generalizeSQL will probably cut down the query to reasonable
1013                         # logging size most of the time. The substr is really just a sanity check.
1014                         if ( $isMaster ) {
1015                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
1016                                 $totalProf = 'DatabaseBase::query-master';
1017                         } else {
1018                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
1019                                 $totalProf = 'DatabaseBase::query';
1020                         }
1021                         wfProfileIn( $totalProf );
1022                         wfProfileIn( $queryProf );
1023                 }
1024
1025                 if ( $this->debug() ) {
1026                         static $cnt = 0;
1027
1028                         $cnt++;
1029                         $sqlx = substr( $commentedSql, 0, 500 );
1030                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
1031
1032                         $master = $isMaster ? 'master' : 'slave';
1033                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
1034                 }
1035
1036                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
1037
1038                 # Do the query and handle errors
1039                 $ret = $this->doQuery( $commentedSql );
1040
1041                 MWDebug::queryTime( $queryId );
1042
1043                 # Try reconnecting if the connection was lost
1044                 if ( false === $ret && $this->wasErrorReissuable() ) {
1045                         # Transaction is gone, like it or not
1046                         $hadTrx = $this->mTrxLevel; // possible lost transaction
1047                         wfDebug( "Connection lost, reconnecting...\n" );
1048                         $this->mTrxLevel = 0;
1049                         wfDebug( "Connection lost, reconnecting...\n" );
1050
1051                         if ( $this->ping() ) {
1052                                 wfDebug( "Reconnected\n" );
1053                                 $sqlx = substr( $commentedSql, 0, 500 );
1054                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
1055                                 global $wgRequestTime;
1056                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
1057                                 if ( $elapsed < 300 ) {
1058                                         # Not a database error to lose a transaction after a minute or two
1059                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
1060                                 }
1061                                 if ( !$hadTrx ) {
1062                                         # Should be safe to silently retry
1063                                         $ret = $this->doQuery( $commentedSql );
1064                                 }
1065                         } else {
1066                                 wfDebug( "Failed\n" );
1067                         }
1068                 }
1069
1070                 if ( false === $ret ) {
1071                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1072                 }
1073
1074                 if ( !Profiler::instance()->isStub() ) {
1075                         wfProfileOut( $queryProf );
1076                         wfProfileOut( $totalProf );
1077                 }
1078
1079                 return $this->resultObject( $ret );
1080         }
1081
1082         /**
1083          * Report a query error. Log the error, and if neither the object ignore
1084          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1085          *
1086          * @param $error String
1087          * @param $errno Integer
1088          * @param $sql String
1089          * @param $fname String
1090          * @param $tempIgnore Boolean
1091          * @throws DBQueryError
1092          */
1093         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1094                 # Ignore errors during error handling to avoid infinite recursion
1095                 $ignore = $this->ignoreErrors( true );
1096                 ++$this->mErrorCount;
1097
1098                 if ( $ignore || $tempIgnore ) {
1099                         wfDebug( "SQL ERROR (ignored): $error\n" );
1100                         $this->ignoreErrors( $ignore );
1101                 } else {
1102                         $sql1line = str_replace( "\n", "\\n", $sql );
1103                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
1104                         wfDebug( "SQL ERROR: " . $error . "\n" );
1105                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1106                 }
1107         }
1108
1109         /**
1110          * Intended to be compatible with the PEAR::DB wrapper functions.
1111          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1112          *
1113          * ? = scalar value, quoted as necessary
1114          * ! = raw SQL bit (a function for instance)
1115          * & = filename; reads the file and inserts as a blob
1116          *     (we don't use this though...)
1117          *
1118          * @param $sql string
1119          * @param $func string
1120          *
1121          * @return array
1122          */
1123         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1124                 /* MySQL doesn't support prepared statements (yet), so just
1125                    pack up the query for reference. We'll manually replace
1126                    the bits later. */
1127                 return array( 'query' => $sql, 'func' => $func );
1128         }
1129
1130         /**
1131          * Free a prepared query, generated by prepare().
1132          * @param $prepared
1133          */
1134         protected function freePrepared( $prepared ) {
1135                 /* No-op by default */
1136         }
1137
1138         /**
1139          * Execute a prepared query with the various arguments
1140          * @param string $prepared the prepared sql
1141          * @param $args Mixed: Either an array here, or put scalars as varargs
1142          *
1143          * @return ResultWrapper
1144          */
1145         public function execute( $prepared, $args = null ) {
1146                 if ( !is_array( $args ) ) {
1147                         # Pull the var args
1148                         $args = func_get_args();
1149                         array_shift( $args );
1150                 }
1151
1152                 $sql = $this->fillPrepared( $prepared['query'], $args );
1153
1154                 return $this->query( $sql, $prepared['func'] );
1155         }
1156
1157         /**
1158          * For faking prepared SQL statements on DBs that don't support it directly.
1159          *
1160          * @param string $preparedQuery a 'preparable' SQL statement
1161          * @param array $args of arguments to fill it with
1162          * @return string executable SQL
1163          */
1164         public function fillPrepared( $preparedQuery, $args ) {
1165                 reset( $args );
1166                 $this->preparedArgs =& $args;
1167
1168                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1169                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1170         }
1171
1172         /**
1173          * preg_callback func for fillPrepared()
1174          * The arguments should be in $this->preparedArgs and must not be touched
1175          * while we're doing this.
1176          *
1177          * @param $matches Array
1178          * @throws DBUnexpectedError
1179          * @return String
1180          */
1181         protected function fillPreparedArg( $matches ) {
1182                 switch ( $matches[1] ) {
1183                         case '\\?':
1184                                 return '?';
1185                         case '\\!':
1186                                 return '!';
1187                         case '\\&':
1188                                 return '&';
1189                 }
1190
1191                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1192
1193                 switch ( $matches[1] ) {
1194                         case '?':
1195                                 return $this->addQuotes( $arg );
1196                         case '!':
1197                                 return $arg;
1198                         case '&':
1199                                 # return $this->addQuotes( file_get_contents( $arg ) );
1200                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1201                         default:
1202                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1203                 }
1204         }
1205
1206         /**
1207          * Free a result object returned by query() or select(). It's usually not
1208          * necessary to call this, just use unset() or let the variable holding
1209          * the result object go out of scope.
1210          *
1211          * @param $res Mixed: A SQL result
1212          */
1213         public function freeResult( $res ) {
1214         }
1215
1216         /**
1217          * A SELECT wrapper which returns a single field from a single result row.
1218          *
1219          * Usually throws a DBQueryError on failure. If errors are explicitly
1220          * ignored, returns false on failure.
1221          *
1222          * If no result rows are returned from the query, false is returned.
1223          *
1224          * @param string|array $table Table name. See DatabaseBase::select() for details.
1225          * @param string $var The field name to select. This must be a valid SQL
1226          *   fragment: do not use unvalidated user input.
1227          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1228          * @param string $fname The function name of the caller.
1229          * @param string|array $options The query options. See DatabaseBase::select() for details.
1230          *
1231          * @return bool|mixed The value from the field, or false on failure.
1232          */
1233         public function selectField( $table, $var, $cond = '', $fname = __METHOD__,
1234                 $options = array()
1235         ) {
1236                 if ( !is_array( $options ) ) {
1237                         $options = array( $options );
1238                 }
1239
1240                 $options['LIMIT'] = 1;
1241
1242                 $res = $this->select( $table, $var, $cond, $fname, $options );
1243
1244                 if ( $res === false || !$this->numRows( $res ) ) {
1245                         return false;
1246                 }
1247
1248                 $row = $this->fetchRow( $res );
1249
1250                 if ( $row !== false ) {
1251                         return reset( $row );
1252                 } else {
1253                         return false;
1254                 }
1255         }
1256
1257         /**
1258          * Returns an optional USE INDEX clause to go after the table, and a
1259          * string to go at the end of the query.
1260          *
1261          * @param array $options associative array of options to be turned into
1262          *              an SQL query, valid keys are listed in the function.
1263          * @return Array
1264          * @see DatabaseBase::select()
1265          */
1266         public function makeSelectOptions( $options ) {
1267                 $preLimitTail = $postLimitTail = '';
1268                 $startOpts = '';
1269
1270                 $noKeyOptions = array();
1271
1272                 foreach ( $options as $key => $option ) {
1273                         if ( is_numeric( $key ) ) {
1274                                 $noKeyOptions[$option] = true;
1275                         }
1276                 }
1277
1278                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1279
1280                 $preLimitTail .= $this->makeOrderBy( $options );
1281
1282                 // if (isset($options['LIMIT'])) {
1283                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1284                 //              isset($options['OFFSET']) ? $options['OFFSET']
1285                 //              : false);
1286                 // }
1287
1288                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1289                         $postLimitTail .= ' FOR UPDATE';
1290                 }
1291
1292                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1293                         $postLimitTail .= ' LOCK IN SHARE MODE';
1294                 }
1295
1296                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1297                         $startOpts .= 'DISTINCT';
1298                 }
1299
1300                 # Various MySQL extensions
1301                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1302                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1303                 }
1304
1305                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1306                         $startOpts .= ' HIGH_PRIORITY';
1307                 }
1308
1309                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1310                         $startOpts .= ' SQL_BIG_RESULT';
1311                 }
1312
1313                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1314                         $startOpts .= ' SQL_BUFFER_RESULT';
1315                 }
1316
1317                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1318                         $startOpts .= ' SQL_SMALL_RESULT';
1319                 }
1320
1321                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1322                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1323                 }
1324
1325                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1326                         $startOpts .= ' SQL_CACHE';
1327                 }
1328
1329                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1330                         $startOpts .= ' SQL_NO_CACHE';
1331                 }
1332
1333                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1334                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1335                 } else {
1336                         $useIndex = '';
1337                 }
1338
1339                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1340         }
1341
1342         /**
1343          * Returns an optional GROUP BY with an optional HAVING
1344          *
1345          * @param array $options associative array of options
1346          * @return string
1347          * @see DatabaseBase::select()
1348          * @since 1.21
1349          */
1350         public function makeGroupByWithHaving( $options ) {
1351                 $sql = '';
1352                 if ( isset( $options['GROUP BY'] ) ) {
1353                         $gb = is_array( $options['GROUP BY'] )
1354                                 ? implode( ',', $options['GROUP BY'] )
1355                                 : $options['GROUP BY'];
1356                         $sql .= ' GROUP BY ' . $gb;
1357                 }
1358                 if ( isset( $options['HAVING'] ) ) {
1359                         $having = is_array( $options['HAVING'] )
1360                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1361                                 : $options['HAVING'];
1362                         $sql .= ' HAVING ' . $having;
1363                 }
1364                 return $sql;
1365         }
1366
1367         /**
1368          * Returns an optional ORDER BY
1369          *
1370          * @param array $options associative array of options
1371          * @return string
1372          * @see DatabaseBase::select()
1373          * @since 1.21
1374          */
1375         public function makeOrderBy( $options ) {
1376                 if ( isset( $options['ORDER BY'] ) ) {
1377                         $ob = is_array( $options['ORDER BY'] )
1378                                 ? implode( ',', $options['ORDER BY'] )
1379                                 : $options['ORDER BY'];
1380                         return ' ORDER BY ' . $ob;
1381                 }
1382                 return '';
1383         }
1384
1385         /**
1386          * Execute a SELECT query constructed using the various parameters provided.
1387          * See below for full details of the parameters.
1388          *
1389          * @param string|array $table Table name
1390          * @param string|array $vars Field names
1391          * @param string|array $conds Conditions
1392          * @param string $fname Caller function name
1393          * @param array $options Query options
1394          * @param $join_conds Array Join conditions
1395          *
1396          * @param $table string|array
1397          *
1398          * May be either an array of table names, or a single string holding a table
1399          * name. If an array is given, table aliases can be specified, for example:
1400          *
1401          *    array( 'a' => 'user' )
1402          *
1403          * This includes the user table in the query, with the alias "a" available
1404          * for use in field names (e.g. a.user_name).
1405          *
1406          * All of the table names given here are automatically run through
1407          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1408          * added, and various other table name mappings to be performed.
1409          *
1410          *
1411          * @param $vars string|array
1412          *
1413          * May be either a field name or an array of field names. The field names
1414          * can be complete fragments of SQL, for direct inclusion into the SELECT
1415          * query. If an array is given, field aliases can be specified, for example:
1416          *
1417          *   array( 'maxrev' => 'MAX(rev_id)' )
1418          *
1419          * This includes an expression with the alias "maxrev" in the query.
1420          *
1421          * If an expression is given, care must be taken to ensure that it is
1422          * DBMS-independent.
1423          *
1424          *
1425          * @param $conds string|array
1426          *
1427          * May be either a string containing a single condition, or an array of
1428          * conditions. If an array is given, the conditions constructed from each
1429          * element are combined with AND.
1430          *
1431          * Array elements may take one of two forms:
1432          *
1433          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1434          *   - Elements with a string key are interpreted as equality conditions,
1435          *     where the key is the field name.
1436          *     - If the value of such an array element is a scalar (such as a
1437          *       string), it will be treated as data and thus quoted appropriately.
1438          *       If it is null, an IS NULL clause will be added.
1439          *     - If the value is an array, an IN(...) clause will be constructed,
1440          *       such that the field name may match any of the elements in the
1441          *       array. The elements of the array will be quoted.
1442          *
1443          * Note that expressions are often DBMS-dependent in their syntax.
1444          * DBMS-independent wrappers are provided for constructing several types of
1445          * expression commonly used in condition queries. See:
1446          *    - DatabaseBase::buildLike()
1447          *    - DatabaseBase::conditional()
1448          *
1449          *
1450          * @param $options string|array
1451          *
1452          * Optional: Array of query options. Boolean options are specified by
1453          * including them in the array as a string value with a numeric key, for
1454          * example:
1455          *
1456          *    array( 'FOR UPDATE' )
1457          *
1458          * The supported options are:
1459          *
1460          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1461          *     with LIMIT can theoretically be used for paging through a result set,
1462          *     but this is discouraged in MediaWiki for performance reasons.
1463          *
1464          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1465          *     and then the first rows are taken until the limit is reached. LIMIT
1466          *     is applied to a result set after OFFSET.
1467          *
1468          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1469          *     changed until the next COMMIT.
1470          *
1471          *   - DISTINCT: Boolean: return only unique result rows.
1472          *
1473          *   - GROUP BY: May be either an SQL fragment string naming a field or
1474          *     expression to group by, or an array of such SQL fragments.
1475          *
1476          *   - HAVING: May be either an string containing a HAVING clause or an array of
1477          *     conditions building the HAVING clause. If an array is given, the conditions
1478          *     constructed from each element are combined with AND.
1479          *
1480          *   - ORDER BY: May be either an SQL fragment giving a field name or
1481          *     expression to order by, or an array of such SQL fragments.
1482          *
1483          *   - USE INDEX: This may be either a string giving the index name to use
1484          *     for the query, or an array. If it is an associative array, each key
1485          *     gives the table name (or alias), each value gives the index name to
1486          *     use for that table. All strings are SQL fragments and so should be
1487          *     validated by the caller.
1488          *
1489          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1490          *     instead of SELECT.
1491          *
1492          * And also the following boolean MySQL extensions, see the MySQL manual
1493          * for documentation:
1494          *
1495          *    - LOCK IN SHARE MODE
1496          *    - STRAIGHT_JOIN
1497          *    - HIGH_PRIORITY
1498          *    - SQL_BIG_RESULT
1499          *    - SQL_BUFFER_RESULT
1500          *    - SQL_SMALL_RESULT
1501          *    - SQL_CALC_FOUND_ROWS
1502          *    - SQL_CACHE
1503          *    - SQL_NO_CACHE
1504          *
1505          *
1506          * @param $join_conds string|array
1507          *
1508          * Optional associative array of table-specific join conditions. In the
1509          * most common case, this is unnecessary, since the join condition can be
1510          * in $conds. However, it is useful for doing a LEFT JOIN.
1511          *
1512          * The key of the array contains the table name or alias. The value is an
1513          * array with two elements, numbered 0 and 1. The first gives the type of
1514          * join, the second is an SQL fragment giving the join condition for that
1515          * table. For example:
1516          *
1517          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1518          *
1519          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1520          *   with no rows in it will be returned. If there was a query error, a
1521          *   DBQueryError exception will be thrown, except if the "ignore errors"
1522          *   option was set, in which case false will be returned.
1523          */
1524         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1525                 $options = array(), $join_conds = array() ) {
1526                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1527
1528                 return $this->query( $sql, $fname );
1529         }
1530
1531         /**
1532          * The equivalent of DatabaseBase::select() except that the constructed SQL
1533          * is returned, instead of being immediately executed. This can be useful for
1534          * doing UNION queries, where the SQL text of each query is needed. In general,
1535          * however, callers outside of Database classes should just use select().
1536          *
1537          * @param string|array $table Table name
1538          * @param string|array $vars Field names
1539          * @param string|array $conds Conditions
1540          * @param string $fname Caller function name
1541          * @param string|array $options Query options
1542          * @param $join_conds string|array Join conditions
1543          *
1544          * @return string SQL query string.
1545          * @see DatabaseBase::select()
1546          */
1547         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1548                 $options = array(), $join_conds = array() )
1549         {
1550                 if ( is_array( $vars ) ) {
1551                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1552                 }
1553
1554                 $options = (array)$options;
1555                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1556                         ? $options['USE INDEX']
1557                         : array();
1558
1559                 if ( is_array( $table ) ) {
1560                         $from = ' FROM ' .
1561                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1562                 } elseif ( $table != '' ) {
1563                         if ( $table[0] == ' ' ) {
1564                                 $from = ' FROM ' . $table;
1565                         } else {
1566                                 $from = ' FROM ' .
1567                                         $this->tableNamesWithUseIndexOrJOIN( array( $table ), $useIndexes, array() );
1568                         }
1569                 } else {
1570                         $from = '';
1571                 }
1572
1573                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1574                         $this->makeSelectOptions( $options );
1575
1576                 if ( !empty( $conds ) ) {
1577                         if ( is_array( $conds ) ) {
1578                                 $conds = $this->makeList( $conds, LIST_AND );
1579                         }
1580                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1581                 } else {
1582                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1583                 }
1584
1585                 if ( isset( $options['LIMIT'] ) ) {
1586                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1587                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1588                 }
1589                 $sql = "$sql $postLimitTail";
1590
1591                 if ( isset( $options['EXPLAIN'] ) ) {
1592                         $sql = 'EXPLAIN ' . $sql;
1593                 }
1594
1595                 return $sql;
1596         }
1597
1598         /**
1599          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1600          * that a single row object is returned. If the query returns no rows,
1601          * false is returned.
1602          *
1603          * @param string|array $table Table name
1604          * @param string|array $vars Field names
1605          * @param array $conds Conditions
1606          * @param string $fname Caller function name
1607          * @param string|array $options Query options
1608          * @param $join_conds array|string Join conditions
1609          *
1610          * @return object|bool
1611          */
1612         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1613                 $options = array(), $join_conds = array() )
1614         {
1615                 $options = (array)$options;
1616                 $options['LIMIT'] = 1;
1617                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1618
1619                 if ( $res === false ) {
1620                         return false;
1621                 }
1622
1623                 if ( !$this->numRows( $res ) ) {
1624                         return false;
1625                 }
1626
1627                 $obj = $this->fetchObject( $res );
1628
1629                 return $obj;
1630         }
1631
1632         /**
1633          * Estimate rows in dataset.
1634          *
1635          * MySQL allows you to estimate the number of rows that would be returned
1636          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1637          * index cardinality statistics, and is notoriously inaccurate, especially
1638          * when large numbers of rows have recently been added or deleted.
1639          *
1640          * For DBMSs that don't support fast result size estimation, this function
1641          * will actually perform the SELECT COUNT(*).
1642          *
1643          * Takes the same arguments as DatabaseBase::select().
1644          *
1645          * @param string $table table name
1646          * @param array|string $vars : unused
1647          * @param array|string $conds : filters on the table
1648          * @param string $fname function name for profiling
1649          * @param array $options options for select
1650          * @return Integer: row count
1651          */
1652         public function estimateRowCount( $table, $vars = '*', $conds = '',
1653                 $fname = __METHOD__, $options = array() )
1654         {
1655                 $rows = 0;
1656                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1657
1658                 if ( $res ) {
1659                         $row = $this->fetchRow( $res );
1660                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1661                 }
1662
1663                 return $rows;
1664         }
1665
1666         /**
1667          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1668          * It's only slightly flawed. Don't use for anything important.
1669          *
1670          * @param string $sql A SQL Query
1671          *
1672          * @return string
1673          */
1674         static function generalizeSQL( $sql ) {
1675                 # This does the same as the regexp below would do, but in such a way
1676                 # as to avoid crashing php on some large strings.
1677                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1678
1679                 $sql = str_replace( "\\\\", '', $sql );
1680                 $sql = str_replace( "\\'", '', $sql );
1681                 $sql = str_replace( "\\\"", '', $sql );
1682                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1683                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1684
1685                 # All newlines, tabs, etc replaced by single space
1686                 $sql = preg_replace( '/\s+/', ' ', $sql );
1687
1688                 # All numbers => N
1689                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1690                 $sql = preg_replace( '/-?\d+/s', 'N', $sql );
1691
1692                 return $sql;
1693         }
1694
1695         /**
1696          * Determines whether a field exists in a table
1697          *
1698          * @param string $table table name
1699          * @param string $field filed to check on that table
1700          * @param string $fname calling function name (optional)
1701          * @return Boolean: whether $table has filed $field
1702          */
1703         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1704                 $info = $this->fieldInfo( $table, $field );
1705
1706                 return (bool)$info;
1707         }
1708
1709         /**
1710          * Determines whether an index exists
1711          * Usually throws a DBQueryError on failure
1712          * If errors are explicitly ignored, returns NULL on failure
1713          *
1714          * @param $table
1715          * @param $index
1716          * @param $fname string
1717          *
1718          * @return bool|null
1719          */
1720         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1721                 if ( !$this->tableExists( $table ) ) {
1722                         return null;
1723                 }
1724
1725                 $info = $this->indexInfo( $table, $index, $fname );
1726                 if ( is_null( $info ) ) {
1727                         return null;
1728                 } else {
1729                         return $info !== false;
1730                 }
1731         }
1732
1733         /**
1734          * Query whether a given table exists
1735          *
1736          * @param $table string
1737          * @param $fname string
1738          *
1739          * @return bool
1740          */
1741         public function tableExists( $table, $fname = __METHOD__ ) {
1742                 $table = $this->tableName( $table );
1743                 $old = $this->ignoreErrors( true );
1744                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1745                 $this->ignoreErrors( $old );
1746
1747                 return (bool)$res;
1748         }
1749
1750         /**
1751          * mysql_field_type() wrapper
1752          * @param $res
1753          * @param $index
1754          * @return string
1755          */
1756         public function fieldType( $res, $index ) {
1757                 if ( $res instanceof ResultWrapper ) {
1758                         $res = $res->result;
1759                 }
1760
1761                 return mysql_field_type( $res, $index );
1762         }
1763
1764         /**
1765          * Determines if a given index is unique
1766          *
1767          * @param $table string
1768          * @param $index string
1769          *
1770          * @return bool
1771          */
1772         public function indexUnique( $table, $index ) {
1773                 $indexInfo = $this->indexInfo( $table, $index );
1774
1775                 if ( !$indexInfo ) {
1776                         return null;
1777                 }
1778
1779                 return !$indexInfo[0]->Non_unique;
1780         }
1781
1782         /**
1783          * Helper for DatabaseBase::insert().
1784          *
1785          * @param $options array
1786          * @return string
1787          */
1788         protected function makeInsertOptions( $options ) {
1789                 return implode( ' ', $options );
1790         }
1791
1792         /**
1793          * INSERT wrapper, inserts an array into a table.
1794          *
1795          * $a may be either:
1796          *
1797          *   - A single associative array. The array keys are the field names, and
1798          *     the values are the values to insert. The values are treated as data
1799          *     and will be quoted appropriately. If NULL is inserted, this will be
1800          *     converted to a database NULL.
1801          *   - An array with numeric keys, holding a list of associative arrays.
1802          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1803          *     each subarray must be identical to each other, and in the same order.
1804          *
1805          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1806          * returns success.
1807          *
1808          * $options is an array of options, with boolean options encoded as values
1809          * with numeric keys, in the same style as $options in
1810          * DatabaseBase::select(). Supported options are:
1811          *
1812          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1813          *     any rows which cause duplicate key errors are not inserted. It's
1814          *     possible to determine how many rows were successfully inserted using
1815          *     DatabaseBase::affectedRows().
1816          *
1817          * @param $table   String Table name. This will be passed through
1818          *                 DatabaseBase::tableName().
1819          * @param $a       Array of rows to insert
1820          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1821          * @param array $options of options
1822          *
1823          * @return bool
1824          */
1825         public function insert( $table, $a, $fname = __METHOD__, $options = array() ) {
1826                 # No rows to insert, easy just return now
1827                 if ( !count( $a ) ) {
1828                         return true;
1829                 }
1830
1831                 $table = $this->tableName( $table );
1832
1833                 if ( !is_array( $options ) ) {
1834                         $options = array( $options );
1835                 }
1836
1837                 $fh = null;
1838                 if ( isset( $options['fileHandle'] ) ) {
1839                         $fh = $options['fileHandle'];
1840                 }
1841                 $options = $this->makeInsertOptions( $options );
1842
1843                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1844                         $multi = true;
1845                         $keys = array_keys( $a[0] );
1846                 } else {
1847                         $multi = false;
1848                         $keys = array_keys( $a );
1849                 }
1850
1851                 $sql = 'INSERT ' . $options .
1852                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1853
1854                 if ( $multi ) {
1855                         $first = true;
1856                         foreach ( $a as $row ) {
1857                                 if ( $first ) {
1858                                         $first = false;
1859                                 } else {
1860                                         $sql .= ',';
1861                                 }
1862                                 $sql .= '(' . $this->makeList( $row ) . ')';
1863                         }
1864                 } else {
1865                         $sql .= '(' . $this->makeList( $a ) . ')';
1866                 }
1867
1868                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1869                         return false;
1870                 } elseif ( $fh !== null ) {
1871                         return true;
1872                 }
1873
1874                 return (bool)$this->query( $sql, $fname );
1875         }
1876
1877         /**
1878          * Make UPDATE options for the DatabaseBase::update function
1879          *
1880          * @param array $options The options passed to DatabaseBase::update
1881          * @return string
1882          */
1883         protected function makeUpdateOptions( $options ) {
1884                 if ( !is_array( $options ) ) {
1885                         $options = array( $options );
1886                 }
1887
1888                 $opts = array();
1889
1890                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1891                         $opts[] = $this->lowPriorityOption();
1892                 }
1893
1894                 if ( in_array( 'IGNORE', $options ) ) {
1895                         $opts[] = 'IGNORE';
1896                 }
1897
1898                 return implode( ' ', $opts );
1899         }
1900
1901         /**
1902          * UPDATE wrapper. Takes a condition array and a SET array.
1903          *
1904          * @param $table  String name of the table to UPDATE. This will be passed through
1905          *                DatabaseBase::tableName().
1906          *
1907          * @param array $values  An array of values to SET. For each array element,
1908          *                the key gives the field name, and the value gives the data
1909          *                to set that field to. The data will be quoted by
1910          *                DatabaseBase::addQuotes().
1911          *
1912          * @param $conds  Array:  An array of conditions (WHERE). See
1913          *                DatabaseBase::select() for the details of the format of
1914          *                condition arrays. Use '*' to update all rows.
1915          *
1916          * @param $fname  String: The function name of the caller (from __METHOD__),
1917          *                for logging and profiling.
1918          *
1919          * @param array $options An array of UPDATE options, can be:
1920          *                   - IGNORE: Ignore unique key conflicts
1921          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1922          * @return Boolean
1923          */
1924         function update( $table, $values, $conds, $fname = __METHOD__, $options = array() ) {
1925                 $table = $this->tableName( $table );
1926                 $opts = $this->makeUpdateOptions( $options );
1927                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1928
1929                 if ( $conds !== array() && $conds !== '*' ) {
1930                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1931                 }
1932
1933                 return $this->query( $sql, $fname );
1934         }
1935
1936         /**
1937          * Makes an encoded list of strings from an array
1938          * @param array $a containing the data
1939          * @param int $mode Constant
1940          *      - LIST_COMMA:          comma separated, no field names
1941          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1942          *        the documentation for $conds in DatabaseBase::select().
1943          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1944          *      - LIST_SET:            comma separated with field names, like a SET clause
1945          *      - LIST_NAMES:          comma separated field names
1946          *
1947          * @throws MWException|DBUnexpectedError
1948          * @return string
1949          */
1950         public function makeList( $a, $mode = LIST_COMMA ) {
1951                 if ( !is_array( $a ) ) {
1952                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1953                 }
1954
1955                 $first = true;
1956                 $list = '';
1957
1958                 foreach ( $a as $field => $value ) {
1959                         if ( !$first ) {
1960                                 if ( $mode == LIST_AND ) {
1961                                         $list .= ' AND ';
1962                                 } elseif ( $mode == LIST_OR ) {
1963                                         $list .= ' OR ';
1964                                 } else {
1965                                         $list .= ',';
1966                                 }
1967                         } else {
1968                                 $first = false;
1969                         }
1970
1971                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1972                                 $list .= "($value)";
1973                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1974                                 $list .= "$value";
1975                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1976                                 if ( count( $value ) == 0 ) {
1977                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1978                                 } elseif ( count( $value ) == 1 ) {
1979                                         // Special-case single values, as IN isn't terribly efficient
1980                                         // Don't necessarily assume the single key is 0; we don't
1981                                         // enforce linear numeric ordering on other arrays here.
1982                                         $value = array_values( $value );
1983                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1984                                 } else {
1985                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1986                                 }
1987                         } elseif ( $value === null ) {
1988                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1989                                         $list .= "$field IS ";
1990                                 } elseif ( $mode == LIST_SET ) {
1991                                         $list .= "$field = ";
1992                                 }
1993                                 $list .= 'NULL';
1994                         } else {
1995                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1996                                         $list .= "$field = ";
1997                                 }
1998                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1999                         }
2000                 }
2001
2002                 return $list;
2003         }
2004
2005         /**
2006          * Build a partial where clause from a 2-d array such as used for LinkBatch.
2007          * The keys on each level may be either integers or strings.
2008          *
2009          * @param array $data organized as 2-d
2010          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
2011          * @param string $baseKey field name to match the base-level keys to (eg 'pl_namespace')
2012          * @param string $subKey field name to match the sub-level keys to (eg 'pl_title')
2013          * @return Mixed: string SQL fragment, or false if no items in array.
2014          */
2015         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2016                 $conds = array();
2017
2018                 foreach ( $data as $base => $sub ) {
2019                         if ( count( $sub ) ) {
2020                                 $conds[] = $this->makeList(
2021                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
2022                                         LIST_AND );
2023                         }
2024                 }
2025
2026                 if ( $conds ) {
2027                         return $this->makeList( $conds, LIST_OR );
2028                 } else {
2029                         // Nothing to search for...
2030                         return false;
2031                 }
2032         }
2033
2034         /**
2035          * Return aggregated value alias
2036          *
2037          * @param $valuedata
2038          * @param $valuename string
2039          *
2040          * @return string
2041          */
2042         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2043                 return $valuename;
2044         }
2045
2046         /**
2047          * @param $field
2048          * @return string
2049          */
2050         public function bitNot( $field ) {
2051                 return "(~$field)";
2052         }
2053
2054         /**
2055          * @param $fieldLeft
2056          * @param $fieldRight
2057          * @return string
2058          */
2059         public function bitAnd( $fieldLeft, $fieldRight ) {
2060                 return "($fieldLeft & $fieldRight)";
2061         }
2062
2063         /**
2064          * @param  $fieldLeft
2065          * @param  $fieldRight
2066          * @return string
2067          */
2068         public function bitOr( $fieldLeft, $fieldRight ) {
2069                 return "($fieldLeft | $fieldRight)";
2070         }
2071
2072         /**
2073          * Build a concatenation list to feed into a SQL query
2074          * @param array $stringList list of raw SQL expressions; caller is responsible for any quoting
2075          * @return String
2076          */
2077         public function buildConcat( $stringList ) {
2078                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2079         }
2080
2081         /**
2082          * Change the current database
2083          *
2084          * @todo Explain what exactly will fail if this is not overridden.
2085          *
2086          * @param $db
2087          *
2088          * @return bool Success or failure
2089          */
2090         public function selectDB( $db ) {
2091                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
2092                 # if your database engine supports a concept similar to MySQL's
2093                 # databases you may as well.
2094                 $this->mDBname = $db;
2095                 return true;
2096         }
2097
2098         /**
2099          * Get the current DB name
2100          */
2101         public function getDBname() {
2102                 return $this->mDBname;
2103         }
2104
2105         /**
2106          * Get the server hostname or IP address
2107          */
2108         public function getServer() {
2109                 return $this->mServer;
2110         }
2111
2112         /**
2113          * Format a table name ready for use in constructing an SQL query
2114          *
2115          * This does two important things: it quotes the table names to clean them up,
2116          * and it adds a table prefix if only given a table name with no quotes.
2117          *
2118          * All functions of this object which require a table name call this function
2119          * themselves. Pass the canonical name to such functions. This is only needed
2120          * when calling query() directly.
2121          *
2122          * @param string $name database table name
2123          * @param string $format One of:
2124          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2125          *            so that it can be used in a query.
2126          *   raw - Do not add identifier quotes to the table name
2127          * @return String: full database name
2128          */
2129         public function tableName( $name, $format = 'quoted' ) {
2130                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
2131                 # Skip the entire process when we have a string quoted on both ends.
2132                 # Note that we check the end so that we will still quote any use of
2133                 # use of `database`.table. But won't break things if someone wants
2134                 # to query a database table with a dot in the name.
2135                 if ( $this->isQuotedIdentifier( $name ) ) {
2136                         return $name;
2137                 }
2138
2139                 # Lets test for any bits of text that should never show up in a table
2140                 # name. Basically anything like JOIN or ON which are actually part of
2141                 # SQL queries, but may end up inside of the table value to combine
2142                 # sql. Such as how the API is doing.
2143                 # Note that we use a whitespace test rather than a \b test to avoid
2144                 # any remote case where a word like on may be inside of a table name
2145                 # surrounded by symbols which may be considered word breaks.
2146                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2147                         return $name;
2148                 }
2149
2150                 # Split database and table into proper variables.
2151                 # We reverse the explode so that database.table and table both output
2152                 # the correct table.
2153                 $dbDetails = explode( '.', $name, 2 );
2154                 if ( count( $dbDetails ) == 2 ) {
2155                         list( $database, $table ) = $dbDetails;
2156                         # We don't want any prefix added in this case
2157                         $prefix = '';
2158                 } else {
2159                         list( $table ) = $dbDetails;
2160                         if ( $wgSharedDB !== null # We have a shared database
2161                                 && $this->mForeign == false # We're not working on a foreign database
2162                                 && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
2163                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2164                         ) {
2165                                 $database = $wgSharedDB;
2166                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2167                         } else {
2168                                 $database = null;
2169                                 $prefix = $this->mTablePrefix; # Default prefix
2170                         }
2171                 }
2172
2173                 # Quote $table and apply the prefix if not quoted.
2174                 $tableName = "{$prefix}{$table}";
2175                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) ) {
2176                         $tableName = $this->addIdentifierQuotes( $tableName );
2177                 }
2178
2179                 # Quote $database and merge it with the table name if needed
2180                 if ( $database !== null ) {
2181                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2182                                 $database = $this->addIdentifierQuotes( $database );
2183                         }
2184                         $tableName = $database . '.' . $tableName;
2185                 }
2186
2187                 return $tableName;
2188         }
2189
2190         /**
2191          * Fetch a number of table names into an array
2192          * This is handy when you need to construct SQL for joins
2193          *
2194          * Example:
2195          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2196          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2197          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2198          *
2199          * @return array
2200          */
2201         public function tableNames() {
2202                 $inArray = func_get_args();
2203                 $retVal = array();
2204
2205                 foreach ( $inArray as $name ) {
2206                         $retVal[$name] = $this->tableName( $name );
2207                 }
2208
2209                 return $retVal;
2210         }
2211
2212         /**
2213          * Fetch a number of table names into an zero-indexed numerical array
2214          * This is handy when you need to construct SQL for joins
2215          *
2216          * Example:
2217          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2218          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2219          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2220          *
2221          * @return array
2222          */
2223         public function tableNamesN() {
2224                 $inArray = func_get_args();
2225                 $retVal = array();
2226
2227                 foreach ( $inArray as $name ) {
2228                         $retVal[] = $this->tableName( $name );
2229                 }
2230
2231                 return $retVal;
2232         }
2233
2234         /**
2235          * Get an aliased table name
2236          * e.g. tableName AS newTableName
2237          *
2238          * @param string $name Table name, see tableName()
2239          * @param string|bool $alias Alias (optional)
2240          * @return string SQL name for aliased table. Will not alias a table to its own name
2241          */
2242         public function tableNameWithAlias( $name, $alias = false ) {
2243                 if ( !$alias || $alias == $name ) {
2244                         return $this->tableName( $name );
2245                 } else {
2246                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2247                 }
2248         }
2249
2250         /**
2251          * Gets an array of aliased table names
2252          *
2253          * @param $tables array( [alias] => table )
2254          * @return array of strings, see tableNameWithAlias()
2255          */
2256         public function tableNamesWithAlias( $tables ) {
2257                 $retval = array();
2258                 foreach ( $tables as $alias => $table ) {
2259                         if ( is_numeric( $alias ) ) {
2260                                 $alias = $table;
2261                         }
2262                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2263                 }
2264                 return $retval;
2265         }
2266
2267         /**
2268          * Get an aliased field name
2269          * e.g. fieldName AS newFieldName
2270          *
2271          * @param string $name Field name
2272          * @param string|bool $alias Alias (optional)
2273          * @return string SQL name for aliased field. Will not alias a field to its own name
2274          */
2275         public function fieldNameWithAlias( $name, $alias = false ) {
2276                 if ( !$alias || (string)$alias === (string)$name ) {
2277                         return $name;
2278                 } else {
2279                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2280                 }
2281         }
2282
2283         /**
2284          * Gets an array of aliased field names
2285          *
2286          * @param $fields array( [alias] => field )
2287          * @return array of strings, see fieldNameWithAlias()
2288          */
2289         public function fieldNamesWithAlias( $fields ) {
2290                 $retval = array();
2291                 foreach ( $fields as $alias => $field ) {
2292                         if ( is_numeric( $alias ) ) {
2293                                 $alias = $field;
2294                         }
2295                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2296                 }
2297                 return $retval;
2298         }
2299
2300         /**
2301          * Get the aliased table name clause for a FROM clause
2302          * which might have a JOIN and/or USE INDEX clause
2303          *
2304          * @param array $tables ( [alias] => table )
2305          * @param $use_index array Same as for select()
2306          * @param $join_conds array Same as for select()
2307          * @return string
2308          */
2309         protected function tableNamesWithUseIndexOrJOIN(
2310                 $tables, $use_index = array(), $join_conds = array()
2311         ) {
2312                 $ret = array();
2313                 $retJOIN = array();
2314                 $use_index = (array)$use_index;
2315                 $join_conds = (array)$join_conds;
2316
2317                 foreach ( $tables as $alias => $table ) {
2318                         if ( !is_string( $alias ) ) {
2319                                 // No alias? Set it equal to the table name
2320                                 $alias = $table;
2321                         }
2322                         // Is there a JOIN clause for this table?
2323                         if ( isset( $join_conds[$alias] ) ) {
2324                                 list( $joinType, $conds ) = $join_conds[$alias];
2325                                 $tableClause = $joinType;
2326                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2327                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2328                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2329                                         if ( $use != '' ) {
2330                                                 $tableClause .= ' ' . $use;
2331                                         }
2332                                 }
2333                                 $on = $this->makeList( (array)$conds, LIST_AND );
2334                                 if ( $on != '' ) {
2335                                         $tableClause .= ' ON (' . $on . ')';
2336                                 }
2337
2338                                 $retJOIN[] = $tableClause;
2339                         // Is there an INDEX clause for this table?
2340                         } elseif ( isset( $use_index[$alias] ) ) {
2341                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2342                                 $tableClause .= ' ' . $this->useIndexClause(
2343                                         implode( ',', (array)$use_index[$alias] ) );
2344
2345                                 $ret[] = $tableClause;
2346                         } else {
2347                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2348
2349                                 $ret[] = $tableClause;
2350                         }
2351                 }
2352
2353                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2354                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2355                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2356
2357                 // Compile our final table clause
2358                 return implode( ' ', array( $implicitJoins, $explicitJoins ) );
2359         }
2360
2361         /**
2362          * Get the name of an index in a given table
2363          *
2364          * @param $index
2365          *
2366          * @return string
2367          */
2368         protected function indexName( $index ) {
2369                 // Backwards-compatibility hack
2370                 $renamed = array(
2371                         'ar_usertext_timestamp' => 'usertext_timestamp',
2372                         'un_user_id' => 'user_id',
2373                         'un_user_ip' => 'user_ip',
2374                 );
2375
2376                 if ( isset( $renamed[$index] ) ) {
2377                         return $renamed[$index];
2378                 } else {
2379                         return $index;
2380                 }
2381         }
2382
2383         /**
2384          * Adds quotes and backslashes.
2385          *
2386          * @param $s string
2387          *
2388          * @return string
2389          */
2390         public function addQuotes( $s ) {
2391                 if ( $s === null ) {
2392                         return 'NULL';
2393                 } else {
2394                         # This will also quote numeric values. This should be harmless,
2395                         # and protects against weird problems that occur when they really
2396                         # _are_ strings such as article titles and string->number->string
2397                         # conversion is not 1:1.
2398                         return "'" . $this->strencode( $s ) . "'";
2399                 }
2400         }
2401
2402         /**
2403          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2404          * MySQL uses `backticks` while basically everything else uses double quotes.
2405          * Since MySQL is the odd one out here the double quotes are our generic
2406          * and we implement backticks in DatabaseMysql.
2407          *
2408          * @param $s string
2409          *
2410          * @return string
2411          */
2412         public function addIdentifierQuotes( $s ) {
2413                 return '"' . str_replace( '"', '""', $s ) . '"';
2414         }
2415
2416         /**
2417          * Returns if the given identifier looks quoted or not according to
2418          * the database convention for quoting identifiers .
2419          *
2420          * @param $name string
2421          *
2422          * @return boolean
2423          */
2424         public function isQuotedIdentifier( $name ) {
2425                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2426         }
2427
2428         /**
2429          * @param $s string
2430          * @return string
2431          */
2432         protected function escapeLikeInternal( $s ) {
2433                 $s = str_replace( '\\', '\\\\', $s );
2434                 $s = $this->strencode( $s );
2435                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2436
2437                 return $s;
2438         }
2439
2440         /**
2441          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2442          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2443          * Alternatively, the function could be provided with an array of aforementioned parameters.
2444          *
2445          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2446          * for subpages of 'My page title'.
2447          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2448          *
2449          * @since 1.16
2450          * @return String: fully built LIKE statement
2451          */
2452         public function buildLike() {
2453                 $params = func_get_args();
2454
2455                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2456                         $params = $params[0];
2457                 }
2458
2459                 $s = '';
2460
2461                 foreach ( $params as $value ) {
2462                         if ( $value instanceof LikeMatch ) {
2463                                 $s .= $value->toString();
2464                         } else {
2465                                 $s .= $this->escapeLikeInternal( $value );
2466                         }
2467                 }
2468
2469                 return " LIKE '" . $s . "' ";
2470         }
2471
2472         /**
2473          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2474          *
2475          * @return LikeMatch
2476          */
2477         public function anyChar() {
2478                 return new LikeMatch( '_' );
2479         }
2480
2481         /**
2482          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2483          *
2484          * @return LikeMatch
2485          */
2486         public function anyString() {
2487                 return new LikeMatch( '%' );
2488         }
2489
2490         /**
2491          * Returns an appropriately quoted sequence value for inserting a new row.
2492          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2493          * subclass will return an integer, and save the value for insertId()
2494          *
2495          * Any implementation of this function should *not* involve reusing
2496          * sequence numbers created for rolled-back transactions.
2497          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2498          * @param $seqName string
2499          * @return null
2500          */
2501         public function nextSequenceValue( $seqName ) {
2502                 return null;
2503         }
2504
2505         /**
2506          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2507          * is only needed because a) MySQL must be as efficient as possible due to
2508          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2509          * which index to pick.  Anyway, other databases might have different
2510          * indexes on a given table.  So don't bother overriding this unless you're
2511          * MySQL.
2512          * @param $index
2513          * @return string
2514          */
2515         public function useIndexClause( $index ) {
2516                 return '';
2517         }
2518
2519         /**
2520          * REPLACE query wrapper.
2521          *
2522          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2523          * except that when there is a duplicate key error, the old row is deleted
2524          * and the new row is inserted in its place.
2525          *
2526          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2527          * perform the delete, we need to know what the unique indexes are so that
2528          * we know how to find the conflicting rows.
2529          *
2530          * It may be more efficient to leave off unique indexes which are unlikely
2531          * to collide. However if you do this, you run the risk of encountering
2532          * errors which wouldn't have occurred in MySQL.
2533          *
2534          * @param string $table The table to replace the row(s) in.
2535          * @param array $rows Can be either a single row to insert, or multiple rows,
2536          *    in the same format as for DatabaseBase::insert()
2537          * @param array $uniqueIndexes is an array of indexes. Each element may be either
2538          *    a field name or an array of field names
2539          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2540          */
2541         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2542                 $quotedTable = $this->tableName( $table );
2543
2544                 if ( count( $rows ) == 0 ) {
2545                         return;
2546                 }
2547
2548                 # Single row case
2549                 if ( !is_array( reset( $rows ) ) ) {
2550                         $rows = array( $rows );
2551                 }
2552
2553                 foreach ( $rows as $row ) {
2554                         # Delete rows which collide
2555                         if ( $uniqueIndexes ) {
2556                                 $sql = "DELETE FROM $quotedTable WHERE ";
2557                                 $first = true;
2558                                 foreach ( $uniqueIndexes as $index ) {
2559                                         if ( $first ) {
2560                                                 $first = false;
2561                                                 $sql .= '( ';
2562                                         } else {
2563                                                 $sql .= ' ) OR ( ';
2564                                         }
2565                                         if ( is_array( $index ) ) {
2566                                                 $first2 = true;
2567                                                 foreach ( $index as $col ) {
2568                                                         if ( $first2 ) {
2569                                                                 $first2 = false;
2570                                                         } else {
2571                                                                 $sql .= ' AND ';
2572                                                         }
2573                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2574                                                 }
2575                                         } else {
2576                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2577                                         }
2578                                 }
2579                                 $sql .= ' )';
2580                                 $this->query( $sql, $fname );
2581                         }
2582
2583                         # Now insert the row
2584                         $this->insert( $table, $row, $fname );
2585                 }
2586         }
2587
2588         /**
2589          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2590          * statement.
2591          *
2592          * @param string $table Table name
2593          * @param array $rows Rows to insert
2594          * @param string $fname Caller function name
2595          *
2596          * @return ResultWrapper
2597          */
2598         protected function nativeReplace( $table, $rows, $fname ) {
2599                 $table = $this->tableName( $table );
2600
2601                 # Single row case
2602                 if ( !is_array( reset( $rows ) ) ) {
2603                         $rows = array( $rows );
2604                 }
2605
2606                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2607                 $first = true;
2608
2609                 foreach ( $rows as $row ) {
2610                         if ( $first ) {
2611                                 $first = false;
2612                         } else {
2613                                 $sql .= ',';
2614                         }
2615
2616                         $sql .= '(' . $this->makeList( $row ) . ')';
2617                 }
2618
2619                 return $this->query( $sql, $fname );
2620         }
2621
2622         /**
2623          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
2624          *
2625          * This updates any conflicting rows (according to the unique indexes) using
2626          * the provided SET clause and inserts any remaining (non-conflicted) rows.
2627          *
2628          * $rows may be either:
2629          *   - A single associative array. The array keys are the field names, and
2630          *     the values are the values to insert. The values are treated as data
2631          *     and will be quoted appropriately. If NULL is inserted, this will be
2632          *     converted to a database NULL.
2633          *   - An array with numeric keys, holding a list of associative arrays.
2634          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
2635          *     each subarray must be identical to each other, and in the same order.
2636          *
2637          * It may be more efficient to leave off unique indexes which are unlikely
2638          * to collide. However if you do this, you run the risk of encountering
2639          * errors which wouldn't have occurred in MySQL.
2640          *
2641          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
2642          * returns success.
2643          *
2644          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
2645          * @param array $rows A single row or list of rows to insert
2646          * @param array $uniqueIndexes List of single field names or field name tuples
2647          * @param array $set An array of values to SET. For each array element,
2648          *                the key gives the field name, and the value gives the data
2649          *                to set that field to. The data will be quoted by
2650          *                DatabaseBase::addQuotes().
2651          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2652          * @param array $options of options
2653          *
2654          * @return bool
2655          * @since 1.22
2656          */
2657         public function upsert(
2658                 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
2659         ) {
2660                 if ( !count( $rows ) ) {
2661                         return true; // nothing to do
2662                 }
2663                 $rows = is_array( reset( $rows ) ) ? $rows : array( $rows );
2664
2665                 if ( count( $uniqueIndexes ) ) {
2666                         $clauses = array(); // list WHERE clauses that each identify a single row
2667                         foreach ( $rows as $row ) {
2668                                 foreach ( $uniqueIndexes as $index ) {
2669                                         $index = is_array( $index ) ? $index : array( $index ); // columns
2670                                         $rowKey = array(); // unique key to this row
2671                                         foreach ( $index as $column ) {
2672                                                 $rowKey[$column] = $row[$column];
2673                                         }
2674                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2675                                 }
2676                         }
2677                         $where = array( $this->makeList( $clauses, LIST_OR ) );
2678                 } else {
2679                         $where = false;
2680                 }
2681
2682                 $useTrx = !$this->mTrxLevel;
2683                 if ( $useTrx ) {
2684                         $this->begin( $fname );
2685                 }
2686                 try {
2687                         # Update any existing conflicting row(s)
2688                         if ( $where !== false ) {
2689                                 $ok = $this->update( $table, $set, $where, $fname );
2690                         } else {
2691                                 $ok = true;
2692                         }
2693                         # Now insert any non-conflicting row(s)
2694                         $ok = $this->insert( $table, $rows, $fname, array( 'IGNORE' ) ) && $ok;
2695                 } catch ( Exception $e ) {
2696                         if ( $useTrx ) {
2697                                 $this->rollback( $fname );
2698                         }
2699                         throw $e;
2700                 }
2701                 if ( $useTrx ) {
2702                         $this->commit( $fname );
2703                 }
2704
2705                 return $ok;
2706         }
2707
2708         /**
2709          * DELETE where the condition is a join.
2710          *
2711          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2712          * we use sub-selects
2713          *
2714          * For safety, an empty $conds will not delete everything. If you want to
2715          * delete all rows where the join condition matches, set $conds='*'.
2716          *
2717          * DO NOT put the join condition in $conds.
2718          *
2719          * @param $delTable   String: The table to delete from.
2720          * @param $joinTable  String: The other table.
2721          * @param $delVar     String: The variable to join on, in the first table.
2722          * @param $joinVar    String: The variable to join on, in the second table.
2723          * @param $conds      Array: Condition array of field names mapped to variables,
2724          *                    ANDed together in the WHERE clause
2725          * @param $fname      String: Calling function name (use __METHOD__) for
2726          *                    logs/profiling
2727          * @throws DBUnexpectedError
2728          */
2729         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2730                 $fname = __METHOD__ )
2731         {
2732                 if ( !$conds ) {
2733                         throw new DBUnexpectedError( $this,
2734                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2735                 }
2736
2737                 $delTable = $this->tableName( $delTable );
2738                 $joinTable = $this->tableName( $joinTable );
2739                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2740                 if ( $conds != '*' ) {
2741                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2742                 }
2743                 $sql .= ')';
2744
2745                 $this->query( $sql, $fname );
2746         }
2747
2748         /**
2749          * Returns the size of a text field, or -1 for "unlimited"
2750          *
2751          * @param $table string
2752          * @param $field string
2753          *
2754          * @return int
2755          */
2756         public function textFieldSize( $table, $field ) {
2757                 $table = $this->tableName( $table );
2758                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2759                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2760                 $row = $this->fetchObject( $res );
2761
2762                 $m = array();
2763
2764                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2765                         $size = $m[1];
2766                 } else {
2767                         $size = -1;
2768                 }
2769
2770                 return $size;
2771         }
2772
2773         /**
2774          * A string to insert into queries to show that they're low-priority, like
2775          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2776          * string and nothing bad should happen.
2777          *
2778          * @return string Returns the text of the low priority option if it is
2779          *   supported, or a blank string otherwise
2780          */
2781         public function lowPriorityOption() {
2782                 return '';
2783         }
2784
2785         /**
2786          * DELETE query wrapper.
2787          *
2788          * @param array $table Table name
2789          * @param string|array $conds of conditions. See $conds in DatabaseBase::select() for
2790          *               the format. Use $conds == "*" to delete all rows
2791          * @param string $fname name of the calling function
2792          *
2793          * @throws DBUnexpectedError
2794          * @return bool|ResultWrapper
2795          */
2796         public function delete( $table, $conds, $fname = __METHOD__ ) {
2797                 if ( !$conds ) {
2798                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2799                 }
2800
2801                 $table = $this->tableName( $table );
2802                 $sql = "DELETE FROM $table";
2803
2804                 if ( $conds != '*' ) {
2805                         if ( is_array( $conds ) ) {
2806                                 $conds = $this->makeList( $conds, LIST_AND );
2807                         }
2808                         $sql .= ' WHERE ' . $conds;
2809                 }
2810
2811                 return $this->query( $sql, $fname );
2812         }
2813
2814         /**
2815          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2816          * into another table.
2817          *
2818          * @param string $destTable The table name to insert into
2819          * @param string|array $srcTable May be either a table name, or an array of table names
2820          *    to include in a join.
2821          *
2822          * @param array $varMap must be an associative array of the form
2823          *    array( 'dest1' => 'source1', ...). Source items may be literals
2824          *    rather than field names, but strings should be quoted with
2825          *    DatabaseBase::addQuotes()
2826          *
2827          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2828          *    the details of the format of condition arrays. May be "*" to copy the
2829          *    whole table.
2830          *
2831          * @param string $fname The function name of the caller, from __METHOD__
2832          *
2833          * @param array $insertOptions Options for the INSERT part of the query, see
2834          *    DatabaseBase::insert() for details.
2835          * @param array $selectOptions Options for the SELECT part of the query, see
2836          *    DatabaseBase::select() for details.
2837          *
2838          * @return ResultWrapper
2839          */
2840         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2841                 $fname = __METHOD__,
2842                 $insertOptions = array(), $selectOptions = array() )
2843         {
2844                 $destTable = $this->tableName( $destTable );
2845
2846                 if ( is_array( $insertOptions ) ) {
2847                         $insertOptions = implode( ' ', $insertOptions );
2848                 }
2849
2850                 if ( !is_array( $selectOptions ) ) {
2851                         $selectOptions = array( $selectOptions );
2852                 }
2853
2854                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2855
2856                 if ( is_array( $srcTable ) ) {
2857                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2858                 } else {
2859                         $srcTable = $this->tableName( $srcTable );
2860                 }
2861
2862                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2863                         " SELECT $startOpts " . implode( ',', $varMap ) .
2864                         " FROM $srcTable $useIndex ";
2865
2866                 if ( $conds != '*' ) {
2867                         if ( is_array( $conds ) ) {
2868                                 $conds = $this->makeList( $conds, LIST_AND );
2869                         }
2870                         $sql .= " WHERE $conds";
2871                 }
2872
2873                 $sql .= " $tailOpts";
2874
2875                 return $this->query( $sql, $fname );
2876         }
2877
2878         /**
2879          * Construct a LIMIT query with optional offset.  This is used for query
2880          * pages.  The SQL should be adjusted so that only the first $limit rows
2881          * are returned.  If $offset is provided as well, then the first $offset
2882          * rows should be discarded, and the next $limit rows should be returned.
2883          * If the result of the query is not ordered, then the rows to be returned
2884          * are theoretically arbitrary.
2885          *
2886          * $sql is expected to be a SELECT, if that makes a difference.
2887          *
2888          * The version provided by default works in MySQL and SQLite.  It will very
2889          * likely need to be overridden for most other DBMSes.
2890          *
2891          * @param string $sql SQL query we will append the limit too
2892          * @param $limit Integer the SQL limit
2893          * @param $offset Integer|bool the SQL offset (default false)
2894          *
2895          * @throws DBUnexpectedError
2896          * @return string
2897          */
2898         public function limitResult( $sql, $limit, $offset = false ) {
2899                 if ( !is_numeric( $limit ) ) {
2900                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2901                 }
2902                 return "$sql LIMIT "
2903                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2904                         . "{$limit} ";
2905         }
2906
2907         /**
2908          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2909          * within the UNION construct.
2910          * @return Boolean
2911          */
2912         public function unionSupportsOrderAndLimit() {
2913                 return true; // True for almost every DB supported
2914         }
2915
2916         /**
2917          * Construct a UNION query
2918          * This is used for providing overload point for other DB abstractions
2919          * not compatible with the MySQL syntax.
2920          * @param array $sqls SQL statements to combine
2921          * @param $all Boolean: use UNION ALL
2922          * @return String: SQL fragment
2923          */
2924         public function unionQueries( $sqls, $all ) {
2925                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2926                 return '(' . implode( $glue, $sqls ) . ')';
2927         }
2928
2929         /**
2930          * Returns an SQL expression for a simple conditional.  This doesn't need
2931          * to be overridden unless CASE isn't supported in your DBMS.
2932          *
2933          * @param string|array $cond SQL expression which will result in a boolean value
2934          * @param string $trueVal SQL expression to return if true
2935          * @param string $falseVal SQL expression to return if false
2936          * @return String: SQL fragment
2937          */
2938         public function conditional( $cond, $trueVal, $falseVal ) {
2939                 if ( is_array( $cond ) ) {
2940                         $cond = $this->makeList( $cond, LIST_AND );
2941                 }
2942                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2943         }
2944
2945         /**
2946          * Returns a comand for str_replace function in SQL query.
2947          * Uses REPLACE() in MySQL
2948          *
2949          * @param string $orig column to modify
2950          * @param string $old column to seek
2951          * @param string $new column to replace with
2952          *
2953          * @return string
2954          */
2955         public function strreplace( $orig, $old, $new ) {
2956                 return "REPLACE({$orig}, {$old}, {$new})";
2957         }
2958
2959         /**
2960          * Determines how long the server has been up
2961          * STUB
2962          *
2963          * @return int
2964          */
2965         public function getServerUptime() {
2966                 return 0;
2967         }
2968
2969         /**
2970          * Determines if the last failure was due to a deadlock
2971          * STUB
2972          *
2973          * @return bool
2974          */
2975         public function wasDeadlock() {
2976                 return false;
2977         }
2978
2979         /**
2980          * Determines if the last failure was due to a lock timeout
2981          * STUB
2982          *
2983          * @return bool
2984          */
2985         public function wasLockTimeout() {
2986                 return false;
2987         }
2988
2989         /**
2990          * Determines if the last query error was something that should be dealt
2991          * with by pinging the connection and reissuing the query.
2992          * STUB
2993          *
2994          * @return bool
2995          */
2996         public function wasErrorReissuable() {
2997                 return false;
2998         }
2999
3000         /**
3001          * Determines if the last failure was due to the database being read-only.
3002          * STUB
3003          *
3004          * @return bool
3005          */
3006         public function wasReadOnlyError() {
3007                 return false;
3008         }
3009
3010         /**
3011          * Perform a deadlock-prone transaction.
3012          *
3013          * This function invokes a callback function to perform a set of write
3014          * queries. If a deadlock occurs during the processing, the transaction
3015          * will be rolled back and the callback function will be called again.
3016          *
3017          * Usage:
3018          *   $dbw->deadlockLoop( callback, ... );
3019          *
3020          * Extra arguments are passed through to the specified callback function.
3021          *
3022          * Returns whatever the callback function returned on its successful,
3023          * iteration, or false on error, for example if the retry limit was
3024          * reached.
3025          *
3026          * @return bool
3027          */
3028         public function deadlockLoop() {
3029                 $this->begin( __METHOD__ );
3030                 $args = func_get_args();
3031                 $function = array_shift( $args );
3032                 $oldIgnore = $this->ignoreErrors( true );
3033                 $tries = self::DEADLOCK_TRIES;
3034
3035                 if ( is_array( $function ) ) {
3036                         $fname = $function[0];
3037                 } else {
3038                         $fname = $function;
3039                 }
3040
3041                 do {
3042                         $retVal = call_user_func_array( $function, $args );
3043                         $error = $this->lastError();
3044                         $errno = $this->lastErrno();
3045                         $sql = $this->lastQuery();
3046
3047                         if ( $errno ) {
3048                                 if ( $this->wasDeadlock() ) {
3049                                         # Retry
3050                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3051                                 } else {
3052                                         $this->reportQueryError( $error, $errno, $sql, $fname );
3053                                 }
3054                         }
3055                 } while ( $this->wasDeadlock() && --$tries > 0 );
3056
3057                 $this->ignoreErrors( $oldIgnore );
3058
3059                 if ( $tries <= 0 ) {
3060                         $this->rollback( __METHOD__ );
3061                         $this->reportQueryError( $error, $errno, $sql, $fname );
3062                         return false;
3063                 } else {
3064                         $this->commit( __METHOD__ );
3065                         return $retVal;
3066                 }
3067         }
3068
3069         /**
3070          * Wait for the slave to catch up to a given master position.
3071          *
3072          * @param $pos DBMasterPos object
3073          * @param $timeout Integer: the maximum number of seconds to wait for
3074          *   synchronisation
3075          *
3076          * @return integer: zero if the slave was past that position already,
3077          *   greater than zero if we waited for some period of time, less than
3078          *   zero if we timed out.
3079          */
3080         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3081                 wfProfileIn( __METHOD__ );
3082
3083                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3084                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
3085
3086                         if ( $wait > $timeout * 1e6 ) {
3087                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
3088                                 wfProfileOut( __METHOD__ );
3089                                 return -1;
3090                         } elseif ( $wait > 0 ) {
3091                                 wfDebug( "Fake slave waiting $wait us\n" );
3092                                 usleep( $wait );
3093                                 wfProfileOut( __METHOD__ );
3094                                 return 1;
3095                         } else {
3096                                 wfDebug( "Fake slave up to date ($wait us)\n" );
3097                                 wfProfileOut( __METHOD__ );
3098                                 return 0;
3099                         }
3100                 }
3101
3102                 wfProfileOut( __METHOD__ );
3103
3104                 # Real waits are implemented in the subclass.
3105                 return 0;
3106         }
3107
3108         /**
3109          * Get the replication position of this slave
3110          *
3111          * @return DBMasterPos, or false if this is not a slave.
3112          */
3113         public function getSlavePos() {
3114                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3115                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
3116                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
3117                         return $pos;
3118                 } else {
3119                         # Stub
3120                         return false;
3121                 }
3122         }
3123
3124         /**
3125          * Get the position of this master
3126          *
3127          * @return DBMasterPos, or false if this is not a master
3128          */
3129         public function getMasterPos() {
3130                 if ( $this->mFakeMaster ) {
3131                         return new MySQLMasterPos( 'fake', microtime( true ) );
3132                 } else {
3133                         return false;
3134                 }
3135         }
3136
3137         /**
3138          * Run an anonymous function as soon as there is no transaction pending.
3139          * If there is a transaction and it is rolled back, then the callback is cancelled.
3140          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
3141          * Callbacks must commit any transactions that they begin.
3142          *
3143          * This is useful for updates to different systems or when separate transactions are needed.
3144          * For example, one might want to enqueue jobs into a system outside the database, but only
3145          * after the database is updated so that the jobs will see the data when they actually run.
3146          * It can also be used for updates that easily cause deadlocks if locks are held too long.
3147          *
3148          * @param callable $callback
3149          * @since 1.20
3150          */
3151         final public function onTransactionIdle( $callback ) {
3152                 $this->mTrxIdleCallbacks[] = array( $callback, wfGetCaller() );
3153                 if ( !$this->mTrxLevel ) {
3154                         $this->runOnTransactionIdleCallbacks();
3155                 }
3156         }
3157
3158         /**
3159          * Run an anonymous function before the current transaction commits or now if there is none.
3160          * If there is a transaction and it is rolled back, then the callback is cancelled.
3161          * Callbacks must not start nor commit any transactions.
3162          *
3163          * This is useful for updates that easily cause deadlocks if locks are held too long
3164          * but where atomicity is strongly desired for these updates and some related updates.
3165          *
3166          * @param callable $callback
3167          * @since 1.22
3168          */
3169         final public function onTransactionPreCommitOrIdle( $callback ) {
3170                 if ( $this->mTrxLevel ) {
3171                         $this->mTrxPreCommitCallbacks[] = array( $callback, wfGetCaller() );
3172                 } else {
3173                         $this->onTransactionIdle( $callback ); // this will trigger immediately
3174                 }
3175         }
3176
3177         /**
3178          * Actually any "on transaction idle" callbacks.
3179          *
3180          * @since 1.20
3181          */
3182         protected function runOnTransactionIdleCallbacks() {
3183                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
3184
3185                 $e = null; // last exception
3186                 do { // callbacks may add callbacks :)
3187                         $callbacks = $this->mTrxIdleCallbacks;
3188                         $this->mTrxIdleCallbacks = array(); // recursion guard
3189                         foreach ( $callbacks as $callback ) {
3190                                 try {
3191                                         list( $phpCallback ) = $callback;
3192                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
3193                                         call_user_func( $phpCallback );
3194                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3195                                 } catch ( Exception $e ) {}
3196                         }
3197                 } while ( count( $this->mTrxIdleCallbacks ) );
3198
3199                 if ( $e instanceof Exception ) {
3200                         throw $e; // re-throw any last exception
3201                 }
3202         }
3203
3204         /**
3205          * Actually any "on transaction pre-commit" callbacks.
3206          *
3207          * @since 1.22
3208          */
3209         protected function runOnTransactionPreCommitCallbacks() {
3210                 $e = null; // last exception
3211                 do { // callbacks may add callbacks :)
3212                         $callbacks = $this->mTrxPreCommitCallbacks;
3213                         $this->mTrxPreCommitCallbacks = array(); // recursion guard
3214                         foreach ( $callbacks as $callback ) {
3215                                 try {
3216                                         list( $phpCallback ) = $callback;
3217                                         call_user_func( $phpCallback );
3218                                 } catch ( Exception $e ) {}
3219                         }
3220                 } while ( count( $this->mTrxPreCommitCallbacks ) );
3221
3222                 if ( $e instanceof Exception ) {
3223                         throw $e; // re-throw any last exception
3224                 }
3225         }
3226
3227         /**
3228          * Begin an atomic section of statements
3229          *
3230          * If a transaction has been started already, just keep track of the given
3231          * section name to make sure the transaction is not committed pre-maturely.
3232          * This function can be used in layers (with sub-sections), so use a stack
3233          * to keep track of the different atomic sections. If there is no transaction,
3234          * start one implicitly.
3235          *
3236          * The goal of this function is to create an atomic section of SQL queries
3237          * without having to start a new transaction if it already exists.
3238          *
3239          * Atomic sections are more strict than transactions. With transactions,
3240          * attempting to begin a new transaction when one is already running results
3241          * in MediaWiki issuing a brief warning and doing an implicit commit. All
3242          * atomic levels *must* be explicitly closed using DatabaseBase::endAtomic(),
3243          * and any database transactions cannot be began or committed until all atomic
3244          * levels are closed. There is no such thing as implicitly opening or closing
3245          * an atomic section.
3246          *
3247          * @since 1.23
3248          * @param string $fname
3249          * @throws DBError
3250          */
3251         final public function startAtomic( $fname = __METHOD__ ) {
3252                 if ( !$this->mTrxLevel ) {
3253                         $this->begin( $fname );
3254                         $this->mTrxAutomatic = true;
3255                         $this->mTrxAutomaticAtomic = true;
3256                 }
3257
3258                 $this->mTrxAtomicLevels->push( $fname );
3259         }
3260
3261         /**
3262          * Ends an atomic section of SQL statements
3263          *
3264          * Ends the next section of atomic SQL statements and commits the transaction
3265          * if necessary.
3266          *
3267          * @since 1.23
3268          * @see DatabaseBase::startAtomic
3269          * @param string $fname
3270          * @throws DBError
3271          */
3272         final public function endAtomic( $fname = __METHOD__ ) {
3273                 if ( !$this->mTrxLevel ) {
3274                         throw new DBUnexpectedError( $this, 'No atomic transaction is open.' );
3275                 }
3276                 if ( $this->mTrxAtomicLevels->isEmpty() ||
3277                         $this->mTrxAtomicLevels->pop() !== $fname
3278                 ) {
3279                         throw new DBUnexpectedError( $this, 'Invalid atomic section ended.' );
3280                 }
3281
3282                 if ( $this->mTrxAtomicLevels->isEmpty() && $this->mTrxAutomaticAtomic ) {
3283                         $this->commit( $fname, 'flush' );
3284                 }
3285         }
3286
3287         /**
3288          * Begin a transaction. If a transaction is already in progress, that transaction will be committed before the
3289          * new transaction is started.
3290          *
3291          * Note that when the DBO_TRX flag is set (which is usually the case for web requests, but not for maintenance scripts),
3292          * any previous database query will have started a transaction automatically.
3293          *
3294          * Nesting of transactions is not supported. Attempts to nest transactions will cause a warning, unless the current
3295          * transaction was started automatically because of the DBO_TRX flag.
3296          *
3297          * @param $fname string
3298          * @throws DBError
3299          */
3300         final public function begin( $fname = __METHOD__ ) {
3301                 global $wgDebugDBTransactions;
3302
3303                 if ( $this->mTrxLevel ) { // implicit commit
3304                         if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3305                                 // If the current transaction was an automatic atomic one, then we definitely have
3306                                 // a problem. Same if there is any unclosed atomic level.
3307                                 throw new DBUnexpectedError( $this,
3308                                         "Attempted to start explicit transaction when atomic levels are still open."
3309                                 );
3310                         } elseif ( !$this->mTrxAutomatic ) {
3311                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3312                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3313                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3314                                         " performing implicit commit!";
3315                                 wfWarn( $msg );
3316                                 wfLogDBError( $msg );
3317                         } else {
3318                                 // if the transaction was automatic and has done write operations,
3319                                 // log it if $wgDebugDBTransactions is enabled.
3320                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3321                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3322                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3323                                         );
3324                                 }
3325                         }
3326
3327                         $this->runOnTransactionPreCommitCallbacks();
3328                         $this->doCommit( $fname );
3329                         if ( $this->mTrxDoneWrites ) {
3330                                 Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3331                         }
3332                         $this->runOnTransactionIdleCallbacks();
3333                 }
3334
3335                 $this->doBegin( $fname );
3336                 $this->mTrxFname = $fname;
3337                 $this->mTrxDoneWrites = false;
3338                 $this->mTrxAutomatic = false;
3339                 $this->mTrxAutomaticAtomic = false;
3340                 $this->mTrxAtomicLevels = new SplStack;
3341                 $this->mTrxIdleCallbacks = array();
3342                 $this->mTrxPreCommitCallbacks = array();
3343         }
3344
3345         /**
3346          * Issues the BEGIN command to the database server.
3347          *
3348          * @see DatabaseBase::begin()
3349          * @param type $fname
3350          */
3351         protected function doBegin( $fname ) {
3352                 $this->query( 'BEGIN', $fname );
3353                 $this->mTrxLevel = 1;
3354         }
3355
3356         /**
3357          * Commits a transaction previously started using begin().
3358          * If no transaction is in progress, a warning is issued.
3359          *
3360          * Nesting of transactions is not supported.
3361          *
3362          * @param $fname string
3363          * @param string $flush Flush flag, set to 'flush' to disable warnings about explicitly committing implicit
3364          *        transactions, or calling commit when no transaction is in progress.
3365          *        This will silently break any ongoing explicit transaction. Only set the flush flag if you are sure
3366          *        that it is safe to ignore these warnings in your context.
3367          */
3368         final public function commit( $fname = __METHOD__, $flush = '' ) {
3369                 if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3370                         // There are still atomic sections open. This cannot be ignored
3371                         throw new DBUnexpectedError( $this, "Attempted to commit transaction while atomic sections are still open" );
3372                 }
3373
3374                 if ( $flush != 'flush' ) {
3375                         if ( !$this->mTrxLevel ) {
3376                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3377                         } elseif ( $this->mTrxAutomatic ) {
3378                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3379                         }
3380                 } else {
3381                         if ( !$this->mTrxLevel ) {
3382                                 return; // nothing to do
3383                         } elseif ( !$this->mTrxAutomatic ) {
3384                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3385                         }
3386                 }
3387
3388                 $this->runOnTransactionPreCommitCallbacks();
3389                 $this->doCommit( $fname );
3390                 if ( $this->mTrxDoneWrites ) {
3391                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3392                 }
3393                 $this->runOnTransactionIdleCallbacks();
3394         }
3395
3396         /**
3397          * Issues the COMMIT command to the database server.
3398          *
3399          * @see DatabaseBase::commit()
3400          * @param type $fname
3401          */
3402         protected function doCommit( $fname ) {
3403                 if ( $this->mTrxLevel ) {
3404                         $this->query( 'COMMIT', $fname );
3405                         $this->mTrxLevel = 0;
3406                 }
3407         }
3408
3409         /**
3410          * Rollback a transaction previously started using begin().
3411          * If no transaction is in progress, a warning is issued.
3412          *
3413          * No-op on non-transactional databases.
3414          *
3415          * @param $fname string
3416          */
3417         final public function rollback( $fname = __METHOD__ ) {
3418                 if ( !$this->mTrxLevel ) {
3419                         wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3420                 }
3421                 $this->doRollback( $fname );
3422                 $this->mTrxIdleCallbacks = array(); // cancel
3423                 $this->mTrxPreCommitCallbacks = array(); // cancel
3424                 $this->mTrxAtomicLevels = new SplStack;
3425                 if ( $this->mTrxDoneWrites ) {
3426                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3427                 }
3428         }
3429
3430         /**
3431          * Issues the ROLLBACK command to the database server.
3432          *
3433          * @see DatabaseBase::rollback()
3434          * @param type $fname
3435          */
3436         protected function doRollback( $fname ) {
3437                 if ( $this->mTrxLevel ) {
3438                         $this->query( 'ROLLBACK', $fname, true );
3439                         $this->mTrxLevel = 0;
3440                 }
3441         }
3442
3443         /**
3444          * Creates a new table with structure copied from existing table
3445          * Note that unlike most database abstraction functions, this function does not
3446          * automatically append database prefix, because it works at a lower
3447          * abstraction level.
3448          * The table names passed to this function shall not be quoted (this
3449          * function calls addIdentifierQuotes when needed).
3450          *
3451          * @param string $oldName name of table whose structure should be copied
3452          * @param string $newName name of table to be created
3453          * @param $temporary Boolean: whether the new table should be temporary
3454          * @param string $fname calling function name
3455          * @throws MWException
3456          * @return Boolean: true if operation was successful
3457          */
3458         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3459                 $fname = __METHOD__
3460         ) {
3461                 throw new MWException(
3462                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3463         }
3464
3465         /**
3466          * List all tables on the database
3467          *
3468          * @param string $prefix Only show tables with this prefix, e.g. mw_
3469          * @param string $fname calling function name
3470          * @throws MWException
3471          */
3472         function listTables( $prefix = null, $fname = __METHOD__ ) {
3473                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3474         }
3475
3476         /**
3477          * Reset the views process cache set by listViews()
3478          * @since 1.22
3479          */
3480         final public function clearViewsCache() {
3481                 $this->allViews = null;
3482         }
3483
3484         /**
3485          * Lists all the VIEWs in the database
3486          *
3487          * For caching purposes the list of all views should be stored in
3488          * $this->allViews. The process cache can be cleared with clearViewsCache()
3489          *
3490          * @param string $prefix   Only show VIEWs with this prefix, eg. unit_test_
3491          * @param string $fname    Name of calling function
3492          * @throws MWException
3493          * @since 1.22
3494          */
3495         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3496                 throw new MWException( 'DatabaseBase::listViews is not implemented in descendant class' );
3497         }
3498
3499         /**
3500          * Differentiates between a TABLE and a VIEW
3501          *
3502          * @param $name string: Name of the database-structure to test.
3503          * @throws MWException
3504          * @since 1.22
3505          */
3506         public function isView( $name ) {
3507                 throw new MWException( 'DatabaseBase::isView is not implemented in descendant class' );
3508         }
3509
3510         /**
3511          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3512          * to the format used for inserting into timestamp fields in this DBMS.
3513          *
3514          * The result is unquoted, and needs to be passed through addQuotes()
3515          * before it can be included in raw SQL.
3516          *
3517          * @param $ts string|int
3518          *
3519          * @return string
3520          */
3521         public function timestamp( $ts = 0 ) {
3522                 return wfTimestamp( TS_MW, $ts );
3523         }
3524
3525         /**
3526          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3527          * to the format used for inserting into timestamp fields in this DBMS. If
3528          * NULL is input, it is passed through, allowing NULL values to be inserted
3529          * into timestamp fields.
3530          *
3531          * The result is unquoted, and needs to be passed through addQuotes()
3532          * before it can be included in raw SQL.
3533          *
3534          * @param $ts string|int
3535          *
3536          * @return string
3537          */
3538         public function timestampOrNull( $ts = null ) {
3539                 if ( is_null( $ts ) ) {
3540                         return null;
3541                 } else {
3542                         return $this->timestamp( $ts );
3543                 }
3544         }
3545
3546         /**
3547          * Take the result from a query, and wrap it in a ResultWrapper if
3548          * necessary. Boolean values are passed through as is, to indicate success
3549          * of write queries or failure.
3550          *
3551          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3552          * resource, and it was necessary to call this function to convert it to
3553          * a wrapper. Nowadays, raw database objects are never exposed to external
3554          * callers, so this is unnecessary in external code. For compatibility with
3555          * old code, ResultWrapper objects are passed through unaltered.
3556          *
3557          * @param $result bool|ResultWrapper
3558          *
3559          * @return bool|ResultWrapper
3560          */
3561         public function resultObject( $result ) {
3562                 if ( empty( $result ) ) {
3563                         return false;
3564                 } elseif ( $result instanceof ResultWrapper ) {
3565                         return $result;
3566                 } elseif ( $result === true ) {
3567                         // Successful write query
3568                         return $result;
3569                 } else {
3570                         return new ResultWrapper( $this, $result );
3571                 }
3572         }
3573
3574         /**
3575          * Ping the server and try to reconnect if it there is no connection
3576          *
3577          * @return bool Success or failure
3578          */
3579         public function ping() {
3580                 # Stub.  Not essential to override.
3581                 return true;
3582         }
3583
3584         /**
3585          * Get slave lag. Currently supported only by MySQL.
3586          *
3587          * Note that this function will generate a fatal error on many
3588          * installations. Most callers should use LoadBalancer::safeGetLag()
3589          * instead.
3590          *
3591          * @return int Database replication lag in seconds
3592          */
3593         public function getLag() {
3594                 return intval( $this->mFakeSlaveLag );
3595         }
3596
3597         /**
3598          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3599          *
3600          * @return int
3601          */
3602         function maxListLen() {
3603                 return 0;
3604         }
3605
3606         /**
3607          * Some DBMSs have a special format for inserting into blob fields, they
3608          * don't allow simple quoted strings to be inserted. To insert into such
3609          * a field, pass the data through this function before passing it to
3610          * DatabaseBase::insert().
3611          * @param $b string
3612          * @return string
3613          */
3614         public function encodeBlob( $b ) {
3615                 return $b;
3616         }
3617
3618         /**
3619          * Some DBMSs return a special placeholder object representing blob fields
3620          * in result objects. Pass the object through this function to return the
3621          * original string.
3622          * @param $b string
3623          * @return string
3624          */
3625         public function decodeBlob( $b ) {
3626                 return $b;
3627         }
3628
3629         /**
3630          * Override database's default behavior. $options include:
3631          *     'connTimeout' : Set the connection timeout value in seconds.
3632          *                     May be useful for very long batch queries such as
3633          *                     full-wiki dumps, where a single query reads out over
3634          *                     hours or days.
3635          *
3636          * @param $options Array
3637          * @return void
3638          */
3639         public function setSessionOptions( array $options ) {
3640         }
3641
3642         /**
3643          * Read and execute SQL commands from a file.
3644          *
3645          * Returns true on success, error string or exception on failure (depending
3646          * on object's error ignore settings).
3647          *
3648          * @param string $filename File name to open
3649          * @param bool|callable $lineCallback Optional function called before reading each line
3650          * @param bool|callable $resultCallback Optional function called for each MySQL result
3651          * @param bool|string $fname Calling function name or false if name should be
3652          *      generated dynamically using $filename
3653          * @param bool|callable $inputCallback Callback: Optional function called for each complete line sent
3654          * @throws MWException
3655          * @throws Exception|MWException
3656          * @return bool|string
3657          */
3658         public function sourceFile(
3659                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3660         ) {
3661                 wfSuppressWarnings();
3662                 $fp = fopen( $filename, 'r' );
3663                 wfRestoreWarnings();
3664
3665                 if ( false === $fp ) {
3666                         throw new MWException( "Could not open \"{$filename}\".\n" );
3667                 }
3668
3669                 if ( !$fname ) {
3670                         $fname = __METHOD__ . "( $filename )";
3671                 }
3672
3673                 try {
3674                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3675                 }
3676                 catch ( MWException $e ) {
3677                         fclose( $fp );
3678                         throw $e;
3679                 }
3680
3681                 fclose( $fp );
3682
3683                 return $error;
3684         }
3685
3686         /**
3687          * Get the full path of a patch file. Originally based on archive()
3688          * from updaters.inc. Keep in mind this always returns a patch, as
3689          * it fails back to MySQL if no DB-specific patch can be found
3690          *
3691          * @param string $patch The name of the patch, like patch-something.sql
3692          * @return String Full path to patch file
3693          */
3694         public function patchPath( $patch ) {
3695                 global $IP;
3696
3697                 $dbType = $this->getType();
3698                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3699                         return "$IP/maintenance/$dbType/archives/$patch";
3700                 } else {
3701                         return "$IP/maintenance/archives/$patch";
3702                 }
3703         }
3704
3705         /**
3706          * Set variables to be used in sourceFile/sourceStream, in preference to the
3707          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3708          * all. If it's set to false, $GLOBALS will be used.
3709          *
3710          * @param bool|array $vars mapping variable name to value.
3711          */
3712         public function setSchemaVars( $vars ) {
3713                 $this->mSchemaVars = $vars;
3714         }
3715
3716         /**
3717          * Read and execute commands from an open file handle.
3718          *
3719          * Returns true on success, error string or exception on failure (depending
3720          * on object's error ignore settings).
3721          *
3722          * @param $fp Resource: File handle
3723          * @param $lineCallback Callback: Optional function called before reading each query
3724          * @param $resultCallback Callback: Optional function called for each MySQL result
3725          * @param string $fname Calling function name
3726          * @param $inputCallback Callback: Optional function called for each complete query sent
3727          * @return bool|string
3728          */
3729         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3730                 $fname = __METHOD__, $inputCallback = false )
3731         {
3732                 $cmd = '';
3733
3734                 while ( !feof( $fp ) ) {
3735                         if ( $lineCallback ) {
3736                                 call_user_func( $lineCallback );
3737                         }
3738
3739                         $line = trim( fgets( $fp ) );
3740
3741                         if ( $line == '' ) {
3742                                 continue;
3743                         }
3744
3745                         if ( '-' == $line[0] && '-' == $line[1] ) {
3746                                 continue;
3747                         }
3748
3749                         if ( $cmd != '' ) {
3750                                 $cmd .= ' ';
3751                         }
3752
3753                         $done = $this->streamStatementEnd( $cmd, $line );
3754
3755                         $cmd .= "$line\n";
3756
3757                         if ( $done || feof( $fp ) ) {
3758                                 $cmd = $this->replaceVars( $cmd );
3759
3760                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3761                                         $res = $this->query( $cmd, $fname );
3762
3763                                         if ( $resultCallback ) {
3764                                                 call_user_func( $resultCallback, $res, $this );
3765                                         }
3766
3767                                         if ( false === $res ) {
3768                                                 $err = $this->lastError();
3769                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3770                                         }
3771                                 }
3772                                 $cmd = '';
3773                         }
3774                 }
3775
3776                 return true;
3777         }
3778
3779         /**
3780          * Called by sourceStream() to check if we've reached a statement end
3781          *
3782          * @param string $sql SQL assembled so far
3783          * @param string $newLine New line about to be added to $sql
3784          * @return Bool Whether $newLine contains end of the statement
3785          */
3786         public function streamStatementEnd( &$sql, &$newLine ) {
3787                 if ( $this->delimiter ) {
3788                         $prev = $newLine;
3789                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3790                         if ( $newLine != $prev ) {
3791                                 return true;
3792                         }
3793                 }
3794                 return false;
3795         }
3796
3797         /**
3798          * Database independent variable replacement. Replaces a set of variables
3799          * in an SQL statement with their contents as given by $this->getSchemaVars().
3800          *
3801          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3802          *
3803          * - '{$var}' should be used for text and is passed through the database's
3804          *   addQuotes method.
3805          * - `{$var}` should be used for identifiers (eg: table and database names),
3806          *   it is passed through the database's addIdentifierQuotes method which
3807          *   can be overridden if the database uses something other than backticks.
3808          * - / *$var* / is just encoded, besides traditional table prefix and
3809          *   table options its use should be avoided.
3810          *
3811          * @param string $ins SQL statement to replace variables in
3812          * @return String The new SQL statement with variables replaced
3813          */
3814         protected function replaceSchemaVars( $ins ) {
3815                 $vars = $this->getSchemaVars();
3816                 foreach ( $vars as $var => $value ) {
3817                         // replace '{$var}'
3818                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3819                         // replace `{$var}`
3820                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3821                         // replace /*$var*/
3822                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3823                 }
3824                 return $ins;
3825         }
3826
3827         /**
3828          * Replace variables in sourced SQL
3829          *
3830          * @param $ins string
3831          *
3832          * @return string
3833          */
3834         protected function replaceVars( $ins ) {
3835                 $ins = $this->replaceSchemaVars( $ins );
3836
3837                 // Table prefixes
3838                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3839                         array( $this, 'tableNameCallback' ), $ins );
3840
3841                 // Index names
3842                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3843                         array( $this, 'indexNameCallback' ), $ins );
3844
3845                 return $ins;
3846         }
3847
3848         /**
3849          * Get schema variables. If none have been set via setSchemaVars(), then
3850          * use some defaults from the current object.
3851          *
3852          * @return array
3853          */
3854         protected function getSchemaVars() {
3855                 if ( $this->mSchemaVars ) {
3856                         return $this->mSchemaVars;
3857                 } else {
3858                         return $this->getDefaultSchemaVars();
3859                 }
3860         }
3861
3862         /**
3863          * Get schema variables to use if none have been set via setSchemaVars().
3864          *
3865          * Override this in derived classes to provide variables for tables.sql
3866          * and SQL patch files.
3867          *
3868          * @return array
3869          */
3870         protected function getDefaultSchemaVars() {
3871                 return array();
3872         }
3873
3874         /**
3875          * Table name callback
3876          *
3877          * @param $matches array
3878          *
3879          * @return string
3880          */
3881         protected function tableNameCallback( $matches ) {
3882                 return $this->tableName( $matches[1] );
3883         }
3884
3885         /**
3886          * Index name callback
3887          *
3888          * @param $matches array
3889          *
3890          * @return string
3891          */
3892         protected function indexNameCallback( $matches ) {
3893                 return $this->indexName( $matches[1] );
3894         }
3895
3896         /**
3897          * Check to see if a named lock is available. This is non-blocking.
3898          *
3899          * @param string $lockName name of lock to poll
3900          * @param string $method name of method calling us
3901          * @return Boolean
3902          * @since 1.20
3903          */
3904         public function lockIsFree( $lockName, $method ) {
3905                 return true;
3906         }
3907
3908         /**
3909          * Acquire a named lock
3910          *
3911          * Abstracted from Filestore::lock() so child classes can implement for
3912          * their own needs.
3913          *
3914          * @param string $lockName name of lock to aquire
3915          * @param string $method name of method calling us
3916          * @param $timeout Integer: timeout
3917          * @return Boolean
3918          */
3919         public function lock( $lockName, $method, $timeout = 5 ) {
3920                 return true;
3921         }
3922
3923         /**
3924          * Release a lock.
3925          *
3926          * @param string $lockName Name of lock to release
3927          * @param string $method Name of method calling us
3928          *
3929          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3930          * by this thread (in which case the lock is not released), and NULL if the named
3931          * lock did not exist
3932          */
3933         public function unlock( $lockName, $method ) {
3934                 return true;
3935         }
3936
3937         /**
3938          * Lock specific tables
3939          *
3940          * @param array $read of tables to lock for read access
3941          * @param array $write of tables to lock for write access
3942          * @param string $method name of caller
3943          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
3944          *
3945          * @return bool
3946          */
3947         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3948                 return true;
3949         }
3950
3951         /**
3952          * Unlock specific tables
3953          *
3954          * @param string $method the caller
3955          *
3956          * @return bool
3957          */
3958         public function unlockTables( $method ) {
3959                 return true;
3960         }
3961
3962         /**
3963          * Delete a table
3964          * @param $tableName string
3965          * @param $fName string
3966          * @return bool|ResultWrapper
3967          * @since 1.18
3968          */
3969         public function dropTable( $tableName, $fName = __METHOD__ ) {
3970                 if ( !$this->tableExists( $tableName, $fName ) ) {
3971                         return false;
3972                 }
3973                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3974                 if ( $this->cascadingDeletes() ) {
3975                         $sql .= " CASCADE";
3976                 }
3977                 return $this->query( $sql, $fName );
3978         }
3979
3980         /**
3981          * Get search engine class. All subclasses of this need to implement this
3982          * if they wish to use searching.
3983          *
3984          * @return String
3985          */
3986         public function getSearchEngine() {
3987                 return 'SearchEngineDummy';
3988         }
3989
3990         /**
3991          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3992          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3993          * because "i" sorts after all numbers.
3994          *
3995          * @return String
3996          */
3997         public function getInfinity() {
3998                 return 'infinity';
3999         }
4000
4001         /**
4002          * Encode an expiry time into the DBMS dependent format
4003          *
4004          * @param string $expiry timestamp for expiry, or the 'infinity' string
4005          * @return String
4006          */
4007         public function encodeExpiry( $expiry ) {
4008                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4009                         ? $this->getInfinity()
4010                         : $this->timestamp( $expiry );
4011         }
4012
4013         /**
4014          * Decode an expiry time into a DBMS independent format
4015          *
4016          * @param string $expiry DB timestamp field value for expiry
4017          * @param $format integer: TS_* constant, defaults to TS_MW
4018          * @return String
4019          */
4020         public function decodeExpiry( $expiry, $format = TS_MW ) {
4021                 return ( $expiry == '' || $expiry == $this->getInfinity() )
4022                         ? 'infinity'
4023                         : wfTimestamp( $format, $expiry );
4024         }
4025
4026         /**
4027          * Allow or deny "big selects" for this session only. This is done by setting
4028          * the sql_big_selects session variable.
4029          *
4030          * This is a MySQL-specific feature.
4031          *
4032          * @param $value Mixed: true for allow, false for deny, or "default" to
4033          *   restore the initial value
4034          */
4035         public function setBigSelects( $value = true ) {
4036                 // no-op
4037         }
4038
4039         /**
4040          * @since 1.19
4041          */
4042         public function __toString() {
4043                 return (string)$this->mConn;
4044         }
4045
4046         /**
4047          * Run a few simple sanity checks
4048          */
4049         public function __destruct() {
4050                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
4051                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
4052                 }
4053                 if ( count( $this->mTrxIdleCallbacks ) || count( $this->mTrxPreCommitCallbacks ) ) {
4054                         $callers = array();
4055                         foreach ( $this->mTrxIdleCallbacks as $callbackInfo ) {
4056                                 $callers[] = $callbackInfo[1];
4057
4058                         }
4059                         $callers = implode( ', ', $callers );
4060                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
4061                 }
4062         }
4063 }