includes/db/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * This file deals with database interface functions
   6  * and query specifics/optimisations.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Database
  25  */
  26
  27 /**
  28  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  29  * following must be implemented to support MediaWiki
  30  *
  31  * @file
  32  * @ingroup Database
  33  */
  34 interface DatabaseType {
  35         /**
  36          * Get the type of the DBMS, as it appears in $wgDBtype.
  37          *
  38          * @return string
  39          */
  40         function getType();
  41
  42         /**
  43          * Open a connection to the database. Usually aborts on failure
  44          *
  45          * @param string $server database server host
  46          * @param string $user database user name
  47          * @param string $password database user password
  48          * @param string $dbName database name
  49          * @return bool
  50          * @throws DBConnectionError
  51          */
  52         function open( $server, $user, $password, $dbName );
  53
  54         /**
  55          * Fetch the next row from the given result object, in object form.
  56          * Fields can be retrieved with $row->fieldname, with fields acting like
  57          * member variables.
  58          * If no more rows are available, false is returned.
  59          *
  60          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  61          * @return object|bool
  62          * @throws DBUnexpectedError Thrown if the database returns an error
  63          */
  64         function fetchObject( $res );
  65
  66         /**
  67          * Fetch the next row from the given result object, in associative array
  68          * form.  Fields are retrieved with $row['fieldname'].
  69          * If no more rows are available, false is returned.
  70          *
  71          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  72          * @return array|bool
  73          * @throws DBUnexpectedError Thrown if the database returns an error
  74          */
  75         function fetchRow( $res );
  76
  77         /**
  78          * Get the number of rows in a result object
  79          *
  80          * @param $res Mixed: A SQL result
  81          * @return int
  82          */
  83         function numRows( $res );
  84
  85         /**
  86          * Get the number of fields in a result object
  87          * @see http://www.php.net/mysql_num_fields
  88          *
  89          * @param $res Mixed: A SQL result
  90          * @return int
  91          */
  92         function numFields( $res );
  93
  94         /**
  95          * Get a field name in a result object
  96          * @see http://www.php.net/mysql_field_name
  97          *
  98          * @param $res Mixed: A SQL result
  99          * @param $n Integer
 100          * @return string
 101          */
 102         function fieldName( $res, $n );
 103
 104         /**
 105          * Get the inserted value of an auto-increment row
 106          *
 107          * The value inserted should be fetched from nextSequenceValue()
 108          *
 109          * Example:
 110          * $id = $dbw->nextSequenceValue( 'page_page_id_seq' );
 111          * $dbw->insert( 'page', array( 'page_id' => $id ) );
 112          * $id = $dbw->insertId();
 113          *
 114          * @return int
 115          */
 116         function insertId();
 117
 118         /**
 119          * Change the position of the cursor in a result object
 120          * @see http://www.php.net/mysql_data_seek
 121          *
 122          * @param $res Mixed: A SQL result
 123          * @param $row Mixed: Either MySQL row or ResultWrapper
 124          */
 125         function dataSeek( $res, $row );
 126
 127         /**
 128          * Get the last error number
 129          * @see http://www.php.net/mysql_errno
 130          *
 131          * @return int
 132          */
 133         function lastErrno();
 134
 135         /**
 136          * Get a description of the last error
 137          * @see http://www.php.net/mysql_error
 138          *
 139          * @return string
 140          */
 141         function lastError();
 142
 143         /**
 144          * mysql_fetch_field() wrapper
 145          * Returns false if the field doesn't exist
 146          *
 147          * @param string $table table name
 148          * @param string $field field name
 149          *
 150          * @return Field
 151          */
 152         function fieldInfo( $table, $field );
 153
 154         /**
 155          * Get information about an index into an object
 156          * @param string $table Table name
 157          * @param string $index Index name
 158          * @param string $fname Calling function name
 159          * @return Mixed: Database-specific index description class or false if the index does not exist
 160          */
 161         function indexInfo( $table, $index, $fname = __METHOD__ );
 162
 163         /**
 164          * Get the number of rows affected by the last write query
 165          * @see http://www.php.net/mysql_affected_rows
 166          *
 167          * @return int
 168          */
 169         function affectedRows();
 170
 171         /**
 172          * Wrapper for addslashes()
 173          *
 174          * @param string $s to be slashed.
 175          * @return string: slashed string.
 176          */
 177         function strencode( $s );
 178
 179         /**
 180          * Returns a wikitext link to the DB's website, e.g.,
 181          *     return "[http://www.mysql.com/ MySQL]";
 182          * Should at least contain plain text, if for some reason
 183          * your database has no website.
 184          *
 185          * @return string: wikitext of a link to the server software's web site
 186          */
 187         function getSoftwareLink();
 188
 189         /**
 190          * A string describing the current software version, like from
 191          * mysql_get_server_info().
 192          *
 193          * @return string: Version information from the database server.
 194          */
 195         function getServerVersion();
 196
 197         /**
 198          * A string describing the current software version, and possibly
 199          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 200          * Use getServerVersion() to get machine-friendly information.
 201          *
 202          * @return string: Version information from the database server
 203          */
 204         function getServerInfo();
 205 }
 206
 207 /**
 208  * Interface for classes that implement or wrap DatabaseBase
 209  * @ingroup Database
 210  */
 211 interface IDatabase {}
 212
 213 /**
 214  * Database abstraction object
 215  * @ingroup Database
 216  */
 217 abstract class DatabaseBase implements IDatabase, DatabaseType {
 218         /** Number of times to re-try an operation in case of deadlock */
 219         const DEADLOCK_TRIES = 4;
 220         /** Minimum time to wait before retry, in microseconds */
 221         const DEADLOCK_DELAY_MIN = 500000;
 222         /** Maximum time to wait before retry */
 223         const DEADLOCK_DELAY_MAX = 1500000;
 224
 225 # ------------------------------------------------------------------------------
 226 # Variables
 227 # ------------------------------------------------------------------------------
 228
 229         protected $mLastQuery = '';
 230         protected $mDoneWrites = false;
 231         protected $mPHPError = false;
 232
 233         protected $mServer, $mUser, $mPassword, $mDBname;
 234
 235         protected $mConn = null;
 236         protected $mOpened = false;
 237
 238         /** @var callable[] */
 239         protected $mTrxIdleCallbacks = array();
 240         /** @var callable[] */
 241         protected $mTrxPreCommitCallbacks = array();
 242
 243         protected $mTablePrefix;
 244         protected $mFlags;
 245         protected $mForeign;
 246         protected $mTrxLevel = 0;
 247         protected $mErrorCount = 0;
 248         protected $mLBInfo = array();
 249         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 250         protected $mDefaultBigSelects = null;
 251         protected $mSchemaVars = false;
 252
 253         protected $preparedArgs;
 254
 255         protected $htmlErrors;
 256
 257         protected $delimiter = ';';
 258
 259         /**
 260          * Remembers the function name given for starting the most recent transaction via begin().
 261          * Used to provide additional context for error reporting.
 262          *
 263          * @var String
 264          * @see DatabaseBase::mTrxLevel
 265          */
 266         private $mTrxFname = null;
 267
 268         /**
 269          * Record if possible write queries were done in the last transaction started
 270          *
 271          * @var Bool
 272          * @see DatabaseBase::mTrxLevel
 273          */
 274         private $mTrxDoneWrites = false;
 275
 276         /**
 277          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 278          *
 279          * @var Bool
 280          * @see DatabaseBase::mTrxLevel
 281          */
 282         private $mTrxAutomatic = false;
 283
 284         /**
 285          * @since 1.21
 286          * @var file handle for upgrade
 287          */
 288         protected $fileHandle = null;
 289
 290 # ------------------------------------------------------------------------------
 291 # Accessors
 292 # ------------------------------------------------------------------------------
 293         # These optionally set a variable and return the previous state
 294
 295         /**
 296          * A string describing the current software version, and possibly
 297          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 298          * Use getServerVersion() to get machine-friendly information.
 299          *
 300          * @return string: Version information from the database server
 301          */
 302         public function getServerInfo() {
 303                 return $this->getServerVersion();
 304         }
 305
 306         /**
 307          * @return string: command delimiter used by this database engine
 308          */
 309         public function getDelimiter() {
 310                 return $this->delimiter;
 311         }
 312
 313         /**
 314          * Boolean, controls output of large amounts of debug information.
 315          * @param $debug bool|null
 316          *   - true to enable debugging
 317          *   - false to disable debugging
 318          *   - omitted or null to do nothing
 319          *
 320          * @return bool|null previous value of the flag
 321          */
 322         public function debug( $debug = null ) {
 323                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 324         }
 325
 326         /**
 327          * Turns buffering of SQL result sets on (true) or off (false). Default is
 328          * "on".
 329          *
 330          * Unbuffered queries are very troublesome in MySQL:
 331          *
 332          *   - If another query is executed while the first query is being read
 333          *     out, the first query is killed. This means you can't call normal
 334          *     MediaWiki functions while you are reading an unbuffered query result
 335          *     from a normal wfGetDB() connection.
 336          *
 337          *   - Unbuffered queries cause the MySQL server to use large amounts of
 338          *     memory and to hold broad locks which block other queries.
 339          *
 340          * If you want to limit client-side memory, it's almost always better to
 341          * split up queries into batches using a LIMIT clause than to switch off
 342          * buffering.
 343          *
 344          * @param $buffer null|bool
 345          *
 346          * @return null|bool The previous value of the flag
 347          */
 348         public function bufferResults( $buffer = null ) {
 349                 if ( is_null( $buffer ) ) {
 350                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 351                 } else {
 352                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 353                 }
 354         }
 355
 356         /**
 357          * Turns on (false) or off (true) the automatic generation and sending
 358          * of a "we're sorry, but there has been a database error" page on
 359          * database errors. Default is on (false). When turned off, the
 360          * code should use lastErrno() and lastError() to handle the
 361          * situation as appropriate.
 362          *
 363          * Do not use this function outside of the Database classes.
 364          *
 365          * @param $ignoreErrors bool|null
 366          *
 367          * @return bool The previous value of the flag.
 368          */
 369         public function ignoreErrors( $ignoreErrors = null ) {
 370                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 371         }
 372
 373         /**
 374          * Gets or sets the current transaction level.
 375          *
 376          * Historically, transactions were allowed to be "nested". This is no
 377          * longer supported, so this function really only returns a boolean.
 378          *
 379          * @param int $level An integer (0 or 1), or omitted to leave it unchanged.
 380          * @return int The previous value
 381          */
 382         public function trxLevel( $level = null ) {
 383                 return wfSetVar( $this->mTrxLevel, $level );
 384         }
 385
 386         /**
 387          * Get/set the number of errors logged. Only useful when errors are ignored
 388          * @param int $count The count to set, or omitted to leave it unchanged.
 389          * @return int The error count
 390          */
 391         public function errorCount( $count = null ) {
 392                 return wfSetVar( $this->mErrorCount, $count );
 393         }
 394
 395         /**
 396          * Get/set the table prefix.
 397          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 398          * @return string The previous table prefix.
 399          */
 400         public function tablePrefix( $prefix = null ) {
 401                 return wfSetVar( $this->mTablePrefix, $prefix );
 402         }
 403
 404         /**
 405          * Set the filehandle to copy write statements to.
 406          *
 407          * @param $fh filehandle
 408          */
 409         public function setFileHandle( $fh ) {
 410                 $this->fileHandle = $fh;
 411         }
 412
 413         /**
 414          * Get properties passed down from the server info array of the load
 415          * balancer.
 416          *
 417          * @param string $name The entry of the info array to get, or null to get the
 418          *   whole array
 419          *
 420          * @return LoadBalancer|null
 421          */
 422         public function getLBInfo( $name = null ) {
 423                 if ( is_null( $name ) ) {
 424                         return $this->mLBInfo;
 425                 } else {
 426                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 427                                 return $this->mLBInfo[$name];
 428                         } else {
 429                                 return null;
 430                         }
 431                 }
 432         }
 433
 434         /**
 435          * Set the LB info array, or a member of it. If called with one parameter,
 436          * the LB info array is set to that parameter. If it is called with two
 437          * parameters, the member with the given name is set to the given value.
 438          *
 439          * @param $name
 440          * @param $value
 441          */
 442         public function setLBInfo( $name, $value = null ) {
 443                 if ( is_null( $value ) ) {
 444                         $this->mLBInfo = $name;
 445                 } else {
 446                         $this->mLBInfo[$name] = $value;
 447                 }
 448         }
 449
 450         /**
 451          * Set lag time in seconds for a fake slave
 452          *
 453          * @param $lag int
 454          */
 455         public function setFakeSlaveLag( $lag ) {
 456                 $this->mFakeSlaveLag = $lag;
 457         }
 458
 459         /**
 460          * Make this connection a fake master
 461          *
 462          * @param $enabled bool
 463          */
 464         public function setFakeMaster( $enabled = true ) {
 465                 $this->mFakeMaster = $enabled;
 466         }
 467
 468         /**
 469          * Returns true if this database supports (and uses) cascading deletes
 470          *
 471          * @return bool
 472          */
 473         public function cascadingDeletes() {
 474                 return false;
 475         }
 476
 477         /**
 478          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 479          *
 480          * @return bool
 481          */
 482         public function cleanupTriggers() {
 483                 return false;
 484         }
 485
 486         /**
 487          * Returns true if this database is strict about what can be put into an IP field.
 488          * Specifically, it uses a NULL value instead of an empty string.
 489          *
 490          * @return bool
 491          */
 492         public function strictIPs() {
 493                 return false;
 494         }
 495
 496         /**
 497          * Returns true if this database uses timestamps rather than integers
 498          *
 499          * @return bool
 500          */
 501         public function realTimestamps() {
 502                 return false;
 503         }
 504
 505         /**
 506          * Returns true if this database does an implicit sort when doing GROUP BY
 507          *
 508          * @return bool
 509          */
 510         public function implicitGroupby() {
 511                 return true;
 512         }
 513
 514         /**
 515          * Returns true if this database does an implicit order by when the column has an index
 516          * For example: SELECT page_title FROM page LIMIT 1
 517          *
 518          * @return bool
 519          */
 520         public function implicitOrderby() {
 521                 return true;
 522         }
 523
 524         /**
 525          * Returns true if this database can do a native search on IP columns
 526          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 527          *
 528          * @return bool
 529          */
 530         public function searchableIPs() {
 531                 return false;
 532         }
 533
 534         /**
 535          * Returns true if this database can use functional indexes
 536          *
 537          * @return bool
 538          */
 539         public function functionalIndexes() {
 540                 return false;
 541         }
 542
 543         /**
 544          * Return the last query that went through DatabaseBase::query()
 545          * @return String
 546          */
 547         public function lastQuery() {
 548                 return $this->mLastQuery;
 549         }
 550
 551         /**
 552          * Returns true if the connection may have been used for write queries.
 553          * Should return true if unsure.
 554          *
 555          * @return bool
 556          */
 557         public function doneWrites() {
 558                 return $this->mDoneWrites;
 559         }
 560
 561         /**
 562          * Returns true if there is a transaction open with possible write
 563          * queries or transaction pre-commit/idle callbacks waiting on it to finish.
 564          *
 565          * @return bool
 566          */
 567         public function writesOrCallbacksPending() {
 568                 return $this->mTrxLevel && (
 569                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 570                 );
 571         }
 572
 573         /**
 574          * Is a connection to the database open?
 575          * @return Boolean
 576          */
 577         public function isOpen() {
 578                 return $this->mOpened;
 579         }
 580
 581         /**
 582          * Set a flag for this connection
 583          *
 584          * @param $flag Integer: DBO_* constants from Defines.php:
 585          *   - DBO_DEBUG: output some debug info (same as debug())
 586          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 587          *   - DBO_TRX: automatically start transactions
 588          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 589          *       and removes it in command line mode
 590          *   - DBO_PERSISTENT: use persistant database connection
 591          */
 592         public function setFlag( $flag ) {
 593                 global $wgDebugDBTransactions;
 594                 $this->mFlags |= $flag;
 595                 if ( ( $flag & DBO_TRX ) & $wgDebugDBTransactions ) {
 596                         wfDebug( "Implicit transactions are now  disabled.\n" );
 597                 }
 598         }
 599
 600         /**
 601          * Clear a flag for this connection
 602          *
 603          * @param $flag: same as setFlag()'s $flag param
 604          */
 605         public function clearFlag( $flag ) {
 606                 global $wgDebugDBTransactions;
 607                 $this->mFlags &= ~$flag;
 608                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 609                         wfDebug( "Implicit transactions are now disabled.\n" );
 610                 }
 611         }
 612
 613         /**
 614          * Returns a boolean whether the flag $flag is set for this connection
 615          *
 616          * @param $flag: same as setFlag()'s $flag param
 617          * @return Boolean
 618          */
 619         public function getFlag( $flag ) {
 620                 return !!( $this->mFlags & $flag );
 621         }
 622
 623         /**
 624          * General read-only accessor
 625          *
 626          * @param $name string
 627          *
 628          * @return string
 629          */
 630         public function getProperty( $name ) {
 631                 return $this->$name;
 632         }
 633
 634         /**
 635          * @return string
 636          */
 637         public function getWikiID() {
 638                 if ( $this->mTablePrefix ) {
 639                         return "{$this->mDBname}-{$this->mTablePrefix}";
 640                 } else {
 641                         return $this->mDBname;
 642                 }
 643         }
 644
 645         /**
 646          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 647          *
 648          * @return string
 649          */
 650         public function getSchemaPath() {
 651                 global $IP;
 652                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 653                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 654                 } else {
 655                         return "$IP/maintenance/tables.sql";
 656                 }
 657         }
 658
 659 # ------------------------------------------------------------------------------
 660 # Other functions
 661 # ------------------------------------------------------------------------------
 662
 663         /**
 664          * Constructor.
 665          *
 666          * FIXME: It is possible to construct a Database object with no associated
 667          * connection object, by specifying no parameters to __construct(). This
 668          * feature is deprecated and should be removed.
 669          *
 670          * FIXME: The long list of formal parameters here is not really appropriate
 671          * for MySQL, and not at all appropriate for any other DBMS. It should be
 672          * replaced by named parameters as in DatabaseBase::factory().
 673          *
 674          * DatabaseBase subclasses should not be constructed directly in external
 675          * code. DatabaseBase::factory() should be used instead.
 676          *
 677          * @param string $server database server host
 678          * @param string $user database user name
 679          * @param string $password database user password
 680          * @param string $dbName database name
 681          * @param $flags
 682          * @param string $tablePrefix database table prefixes. By default use the prefix gave in LocalSettings.php
 683          * @param bool $foreign disable some operations specific to local databases
 684          */
 685         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 686                 $flags = 0, $tablePrefix = 'get from global', $foreign = false
 687         ) {
 688                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 689
 690                 $this->mFlags = $flags;
 691
 692                 if ( $this->mFlags & DBO_DEFAULT ) {
 693                         if ( $wgCommandLineMode ) {
 694                                 $this->mFlags &= ~DBO_TRX;
 695                                 if ( $wgDebugDBTransactions ) {
 696                                         wfDebug( "Implicit transaction open disabled.\n" );
 697                                 }
 698                         } else {
 699                                 $this->mFlags |= DBO_TRX;
 700                                 if ( $wgDebugDBTransactions ) {
 701                                         wfDebug( "Implicit transaction open enabled.\n" );
 702                                 }
 703                         }
 704                 }
 705
 706                 /** Get the default table prefix*/
 707                 if ( $tablePrefix == 'get from global' ) {
 708                         $this->mTablePrefix = $wgDBprefix;
 709                 } else {
 710                         $this->mTablePrefix = $tablePrefix;
 711                 }
 712
 713                 $this->mForeign = $foreign;
 714
 715                 if ( $user ) {
 716                         $this->open( $server, $user, $password, $dbName );
 717                 }
 718         }
 719
 720         /**
 721          * Called by serialize. Throw an exception when DB connection is serialized.
 722          * This causes problems on some database engines because the connection is
 723          * not restored on unserialize.
 724          */
 725         public function __sleep() {
 726                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 727         }
 728
 729         /**
 730          * Given a DB type, construct the name of the appropriate child class of
 731          * DatabaseBase. This is designed to replace all of the manual stuff like:
 732          *      $class = 'Database' . ucfirst( strtolower( $dbType ) );
 733          * as well as validate against the canonical list of DB types we have
 734          *
 735          * This factory function is mostly useful for when you need to connect to a
 736          * database other than the MediaWiki default (such as for external auth,
 737          * an extension, et cetera). Do not use this to connect to the MediaWiki
 738          * database. Example uses in core:
 739          * @see LoadBalancer::reallyOpenConnection()
 740          * @see ForeignDBRepo::getMasterDB()
 741          * @see WebInstaller_DBConnect::execute()
 742          *
 743          * @since 1.18
 744          *
 745          * @param string $dbType A possible DB type
 746          * @param array $p An array of options to pass to the constructor.
 747          *    Valid options are: host, user, password, dbname, flags, tablePrefix, driver
 748          * @return DatabaseBase subclass or null
 749          */
 750         final public static function factory( $dbType, $p = array() ) {
 751                 $canonicalDBTypes = array(
 752                         'mysql'    => array( 'mysqli', 'mysql' ),
 753                         'postgres' => array(),
 754                         'sqlite'   => array(),
 755                         'oracle'   => array(),
 756                         'mssql'    => array(),
 757                 );
 758
 759                 $driver = false;
 760                 $dbType = strtolower( $dbType );
 761                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 762                         $possibleDrivers = $canonicalDBTypes[$dbType];
 763                         if ( !empty( $p['driver'] ) ) {
 764                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 765                                         $driver = $p['driver'];
 766                                 } else {
 767                                         throw new MWException( __METHOD__ .
 768                                                 " cannot construct Database with type '$dbType' and driver '{$p['driver']}'" );
 769                                 }
 770                         } else {
 771                                 foreach ( $possibleDrivers as $posDriver ) {
 772                                         if ( extension_loaded( $posDriver ) ) {
 773                                                 $driver = $posDriver;
 774                                                 break;
 775                                         }
 776                                 }
 777                         }
 778                 } else {
 779                         $driver = $dbType;
 780                 }
 781                 if ( $driver === false ) {
 782                         throw new MWException( __METHOD__ .
 783                                 " no viable database extension found for type '$dbType'" );
 784                 }
 785
 786                 $class = 'Database' . ucfirst( $driver );
 787                 if ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 788                         return new $class(
 789                                 isset( $p['host'] ) ? $p['host'] : false,
 790                                 isset( $p['user'] ) ? $p['user'] : false,
 791                                 isset( $p['password'] ) ? $p['password'] : false,
 792                                 isset( $p['dbname'] ) ? $p['dbname'] : false,
 793                                 isset( $p['flags'] ) ? $p['flags'] : 0,
 794                                 isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global',
 795                                 isset( $p['foreign'] ) ? $p['foreign'] : false
 796                         );
 797                 } else {
 798                         return null;
 799                 }
 800         }
 801
 802         protected function installErrorHandler() {
 803                 $this->mPHPError = false;
 804                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 805                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 806         }
 807
 808         /**
 809          * @return bool|string
 810          */
 811         protected function restoreErrorHandler() {
 812                 restore_error_handler();
 813                 if ( $this->htmlErrors !== false ) {
 814                         ini_set( 'html_errors', $this->htmlErrors );
 815                 }
 816                 if ( $this->mPHPError ) {
 817                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 818                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 819                         return $error;
 820                 } else {
 821                         return false;
 822                 }
 823         }
 824
 825         /**
 826          * @param $errno
 827          * @param $errstr
 828          * @access private
 829          */
 830         public function connectionErrorHandler( $errno, $errstr ) {
 831                 $this->mPHPError = $errstr;
 832         }
 833
 834         /**
 835          * Closes a database connection.
 836          * if it is open : commits any open transactions
 837          *
 838          * @throws MWException
 839          * @return Bool operation success. true if already closed.
 840          */
 841         public function close() {
 842                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 843                         throw new MWException( "Transaction idle callbacks still pending." );
 844                 }
 845                 $this->mOpened = false;
 846                 if ( $this->mConn ) {
 847                         if ( $this->trxLevel() ) {
 848                                 if ( !$this->mTrxAutomatic ) {
 849                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 850                                                 " performing implicit commit before closing connection!" );
 851                                 }
 852
 853                                 $this->commit( __METHOD__, 'flush' );
 854                         }
 855
 856                         $ret = $this->closeConnection();
 857                         $this->mConn = false;
 858                         return $ret;
 859                 } else {
 860                         return true;
 861                 }
 862         }
 863
 864         /**
 865          * Closes underlying database connection
 866          * @since 1.20
 867          * @return bool: Whether connection was closed successfully
 868          */
 869         abstract protected function closeConnection();
 870
 871         /**
 872          * @param string $error fallback error message, used if none is given by DB
 873          * @throws DBConnectionError
 874          */
 875         function reportConnectionError( $error = 'Unknown error' ) {
 876                 $myError = $this->lastError();
 877                 if ( $myError ) {
 878                         $error = $myError;
 879                 }
 880
 881                 # New method
 882                 throw new DBConnectionError( $this, $error );
 883         }
 884
 885         /**
 886          * The DBMS-dependent part of query()
 887          *
 888          * @param  $sql String: SQL query.
 889          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 890          */
 891         abstract protected function doQuery( $sql );
 892
 893         /**
 894          * Determine whether a query writes to the DB.
 895          * Should return true if unsure.
 896          *
 897          * @param $sql string
 898          *
 899          * @return bool
 900          */
 901         public function isWriteQuery( $sql ) {
 902                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 903         }
 904
 905         /**
 906          * Run an SQL query and return the result. Normally throws a DBQueryError
 907          * on failure. If errors are ignored, returns false instead.
 908          *
 909          * In new code, the query wrappers select(), insert(), update(), delete(),
 910          * etc. should be used where possible, since they give much better DBMS
 911          * independence and automatically quote or validate user input in a variety
 912          * of contexts. This function is generally only useful for queries which are
 913          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 914          * as CREATE TABLE.
 915          *
 916          * However, the query wrappers themselves should call this function.
 917          *
 918          * @param  $sql        String: SQL query
 919          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 920          *     comment (you can use __METHOD__ or add some extra info)
 921          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 922          *     maybe best to catch the exception instead?
 923          * @throws MWException
 924          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 925          *     for a successful read query, or false on failure if $tempIgnore set
 926          */
 927         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 928                 global $wgUser, $wgDebugDBTransactions;
 929
 930                 $this->mLastQuery = $sql;
 931                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 932                         # Set a flag indicating that writes have been done
 933                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 934                         $this->mDoneWrites = true;
 935                 }
 936
 937                 # Add a comment for easy SHOW PROCESSLIST interpretation
 938                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 939                         $userName = $wgUser->getName();
 940                         if ( mb_strlen( $userName ) > 15 ) {
 941                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 942                         }
 943                         $userName = str_replace( '/', '', $userName );
 944                 } else {
 945                         $userName = '';
 946                 }
 947
 948                 // Add trace comment to the begin of the sql string, right after the operator.
 949                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 950                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 951
 952                 # If DBO_TRX is set, start a transaction
 953                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 954                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' )
 955                 {
 956                         # Avoid establishing transactions for SHOW and SET statements too -
 957                         # that would delay transaction initializations to once connection
 958                         # is really used by application
 959                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 960                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 961                                 if ( $wgDebugDBTransactions ) {
 962                                         wfDebug( "Implicit transaction start.\n" );
 963                                 }
 964                                 $this->begin( __METHOD__ . " ($fname)" );
 965                                 $this->mTrxAutomatic = true;
 966                         }
 967                 }
 968
 969                 # Keep track of whether the transaction has write queries pending
 970                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
 971                         $this->mTrxDoneWrites = true;
 972                         Profiler::instance()->transactionWritingIn( $this->mServer, $this->mDBname );
 973                 }
 974
 975                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 976                 if ( !Profiler::instance()->isStub() ) {
 977                         # generalizeSQL will probably cut down the query to reasonable
 978                         # logging size most of the time. The substr is really just a sanity check.
 979                         if ( $isMaster ) {
 980                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 981                                 $totalProf = 'DatabaseBase::query-master';
 982                         } else {
 983                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 984                                 $totalProf = 'DatabaseBase::query';
 985                         }
 986                         wfProfileIn( $totalProf );
 987                         wfProfileIn( $queryProf );
 988                 }
 989
 990                 if ( $this->debug() ) {
 991                         static $cnt = 0;
 992
 993                         $cnt++;
 994                         $sqlx = substr( $commentedSql, 0, 500 );
 995                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 996
 997                         $master = $isMaster ? 'master' : 'slave';
 998                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 999                 }
1000
1001                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
1002
1003                 # Do the query and handle errors
1004                 $ret = $this->doQuery( $commentedSql );
1005
1006                 MWDebug::queryTime( $queryId );
1007
1008                 # Try reconnecting if the connection was lost
1009                 if ( false === $ret && $this->wasErrorReissuable() ) {
1010                         # Transaction is gone, like it or not
1011                         $this->mTrxLevel = 0;
1012                         $this->mTrxIdleCallbacks = array(); // cancel
1013                         $this->mTrxPreCommitCallbacks = array(); // cancel
1014                         wfDebug( "Connection lost, reconnecting...\n" );
1015
1016                         if ( $this->ping() ) {
1017                                 wfDebug( "Reconnected\n" );
1018                                 $sqlx = substr( $commentedSql, 0, 500 );
1019                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
1020                                 global $wgRequestTime;
1021                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
1022                                 if ( $elapsed < 300 ) {
1023                                         # Not a database error to lose a transaction after a minute or two
1024                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
1025                                 }
1026                                 $ret = $this->doQuery( $commentedSql );
1027                         } else {
1028                                 wfDebug( "Failed\n" );
1029                         }
1030                 }
1031
1032                 if ( false === $ret ) {
1033                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1034                 }
1035
1036                 if ( !Profiler::instance()->isStub() ) {
1037                         wfProfileOut( $queryProf );
1038                         wfProfileOut( $totalProf );
1039                 }
1040
1041                 return $this->resultObject( $ret );
1042         }
1043
1044         /**
1045          * Report a query error. Log the error, and if neither the object ignore
1046          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1047          *
1048          * @param $error String
1049          * @param $errno Integer
1050          * @param $sql String
1051          * @param $fname String
1052          * @param $tempIgnore Boolean
1053          * @throws DBQueryError
1054          */
1055         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1056                 # Ignore errors during error handling to avoid infinite recursion
1057                 $ignore = $this->ignoreErrors( true );
1058                 ++$this->mErrorCount;
1059
1060                 if ( $ignore || $tempIgnore ) {
1061                         wfDebug( "SQL ERROR (ignored): $error\n" );
1062                         $this->ignoreErrors( $ignore );
1063                 } else {
1064                         $sql1line = str_replace( "\n", "\\n", $sql );
1065                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
1066                         wfDebug( "SQL ERROR: " . $error . "\n" );
1067                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1068                 }
1069         }
1070
1071         /**
1072          * Intended to be compatible with the PEAR::DB wrapper functions.
1073          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1074          *
1075          * ? = scalar value, quoted as necessary
1076          * ! = raw SQL bit (a function for instance)
1077          * & = filename; reads the file and inserts as a blob
1078          *     (we don't use this though...)
1079          *
1080          * @param $sql string
1081          * @param $func string
1082          *
1083          * @return array
1084          */
1085         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1086                 /* MySQL doesn't support prepared statements (yet), so just
1087                    pack up the query for reference. We'll manually replace
1088                    the bits later. */
1089                 return array( 'query' => $sql, 'func' => $func );
1090         }
1091
1092         /**
1093          * Free a prepared query, generated by prepare().
1094          * @param $prepared
1095          */
1096         protected function freePrepared( $prepared ) {
1097                 /* No-op by default */
1098         }
1099
1100         /**
1101          * Execute a prepared query with the various arguments
1102          * @param string $prepared the prepared sql
1103          * @param $args Mixed: Either an array here, or put scalars as varargs
1104          *
1105          * @return ResultWrapper
1106          */
1107         public function execute( $prepared, $args = null ) {
1108                 if ( !is_array( $args ) ) {
1109                         # Pull the var args
1110                         $args = func_get_args();
1111                         array_shift( $args );
1112                 }
1113
1114                 $sql = $this->fillPrepared( $prepared['query'], $args );
1115
1116                 return $this->query( $sql, $prepared['func'] );
1117         }
1118
1119         /**
1120          * For faking prepared SQL statements on DBs that don't support it directly.
1121          *
1122          * @param string $preparedQuery a 'preparable' SQL statement
1123          * @param array $args of arguments to fill it with
1124          * @return string executable SQL
1125          */
1126         public function fillPrepared( $preparedQuery, $args ) {
1127                 reset( $args );
1128                 $this->preparedArgs =& $args;
1129
1130                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1131                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1132         }
1133
1134         /**
1135          * preg_callback func for fillPrepared()
1136          * The arguments should be in $this->preparedArgs and must not be touched
1137          * while we're doing this.
1138          *
1139          * @param $matches Array
1140          * @throws DBUnexpectedError
1141          * @return String
1142          */
1143         protected function fillPreparedArg( $matches ) {
1144                 switch ( $matches[1] ) {
1145                         case '\\?':
1146                                 return '?';
1147                         case '\\!':
1148                                 return '!';
1149                         case '\\&':
1150                                 return '&';
1151                 }
1152
1153                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1154
1155                 switch ( $matches[1] ) {
1156                         case '?':
1157                                 return $this->addQuotes( $arg );
1158                         case '!':
1159                                 return $arg;
1160                         case '&':
1161                                 # return $this->addQuotes( file_get_contents( $arg ) );
1162                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1163                         default:
1164                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1165                 }
1166         }
1167
1168         /**
1169          * Free a result object returned by query() or select(). It's usually not
1170          * necessary to call this, just use unset() or let the variable holding
1171          * the result object go out of scope.
1172          *
1173          * @param $res Mixed: A SQL result
1174          */
1175         public function freeResult( $res ) {
1176         }
1177
1178         /**
1179          * A SELECT wrapper which returns a single field from a single result row.
1180          *
1181          * Usually throws a DBQueryError on failure. If errors are explicitly
1182          * ignored, returns false on failure.
1183          *
1184          * If no result rows are returned from the query, false is returned.
1185          *
1186          * @param string|array $table Table name. See DatabaseBase::select() for details.
1187          * @param string $var The field name to select. This must be a valid SQL
1188          *   fragment: do not use unvalidated user input.
1189          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1190          * @param string $fname The function name of the caller.
1191          * @param string|array $options The query options. See DatabaseBase::select() for details.
1192          *
1193          * @return bool|mixed The value from the field, or false on failure.
1194          */
1195         public function selectField( $table, $var, $cond = '', $fname = __METHOD__,
1196                 $options = array()
1197         ) {
1198                 if ( !is_array( $options ) ) {
1199                         $options = array( $options );
1200                 }
1201
1202                 $options['LIMIT'] = 1;
1203
1204                 $res = $this->select( $table, $var, $cond, $fname, $options );
1205
1206                 if ( $res === false || !$this->numRows( $res ) ) {
1207                         return false;
1208                 }
1209
1210                 $row = $this->fetchRow( $res );
1211
1212                 if ( $row !== false ) {
1213                         return reset( $row );
1214                 } else {
1215                         return false;
1216                 }
1217         }
1218
1219         /**
1220          * Returns an optional USE INDEX clause to go after the table, and a
1221          * string to go at the end of the query.
1222          *
1223          * @param array $options associative array of options to be turned into
1224          *              an SQL query, valid keys are listed in the function.
1225          * @return Array
1226          * @see DatabaseBase::select()
1227          */
1228         public function makeSelectOptions( $options ) {
1229                 $preLimitTail = $postLimitTail = '';
1230                 $startOpts = '';
1231
1232                 $noKeyOptions = array();
1233
1234                 foreach ( $options as $key => $option ) {
1235                         if ( is_numeric( $key ) ) {
1236                                 $noKeyOptions[$option] = true;
1237                         }
1238                 }
1239
1240                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1241
1242                 $preLimitTail .= $this->makeOrderBy( $options );
1243
1244                 // if (isset($options['LIMIT'])) {
1245                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1246                 //              isset($options['OFFSET']) ? $options['OFFSET']
1247                 //              : false);
1248                 // }
1249
1250                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1251                         $postLimitTail .= ' FOR UPDATE';
1252                 }
1253
1254                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1255                         $postLimitTail .= ' LOCK IN SHARE MODE';
1256                 }
1257
1258                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1259                         $startOpts .= 'DISTINCT';
1260                 }
1261
1262                 # Various MySQL extensions
1263                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1264                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1265                 }
1266
1267                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1268                         $startOpts .= ' HIGH_PRIORITY';
1269                 }
1270
1271                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1272                         $startOpts .= ' SQL_BIG_RESULT';
1273                 }
1274
1275                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1276                         $startOpts .= ' SQL_BUFFER_RESULT';
1277                 }
1278
1279                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1280                         $startOpts .= ' SQL_SMALL_RESULT';
1281                 }
1282
1283                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1284                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1285                 }
1286
1287                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1288                         $startOpts .= ' SQL_CACHE';
1289                 }
1290
1291                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1292                         $startOpts .= ' SQL_NO_CACHE';
1293                 }
1294
1295                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1296                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1297                 } else {
1298                         $useIndex = '';
1299                 }
1300
1301                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1302         }
1303
1304         /**
1305          * Returns an optional GROUP BY with an optional HAVING
1306          *
1307          * @param array $options associative array of options
1308          * @return string
1309          * @see DatabaseBase::select()
1310          * @since 1.21
1311          */
1312         public function makeGroupByWithHaving( $options ) {
1313                 $sql = '';
1314                 if ( isset( $options['GROUP BY'] ) ) {
1315                         $gb = is_array( $options['GROUP BY'] )
1316                                 ? implode( ',', $options['GROUP BY'] )
1317                                 : $options['GROUP BY'];
1318                         $sql .= ' GROUP BY ' . $gb;
1319                 }
1320                 if ( isset( $options['HAVING'] ) ) {
1321                         $having = is_array( $options['HAVING'] )
1322                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1323                                 : $options['HAVING'];
1324                         $sql .= ' HAVING ' . $having;
1325                 }
1326                 return $sql;
1327         }
1328
1329         /**
1330          * Returns an optional ORDER BY
1331          *
1332          * @param array $options associative array of options
1333          * @return string
1334          * @see DatabaseBase::select()
1335          * @since 1.21
1336          */
1337         public function makeOrderBy( $options ) {
1338                 if ( isset( $options['ORDER BY'] ) ) {
1339                         $ob = is_array( $options['ORDER BY'] )
1340                                 ? implode( ',', $options['ORDER BY'] )
1341                                 : $options['ORDER BY'];
1342                         return ' ORDER BY ' . $ob;
1343                 }
1344                 return '';
1345         }
1346
1347         /**
1348          * Execute a SELECT query constructed using the various parameters provided.
1349          * See below for full details of the parameters.
1350          *
1351          * @param string|array $table Table name
1352          * @param string|array $vars Field names
1353          * @param string|array $conds Conditions
1354          * @param string $fname Caller function name
1355          * @param array $options Query options
1356          * @param $join_conds Array Join conditions
1357          *
1358          * @param $table string|array
1359          *
1360          * May be either an array of table names, or a single string holding a table
1361          * name. If an array is given, table aliases can be specified, for example:
1362          *
1363          *    array( 'a' => 'user' )
1364          *
1365          * This includes the user table in the query, with the alias "a" available
1366          * for use in field names (e.g. a.user_name).
1367          *
1368          * All of the table names given here are automatically run through
1369          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1370          * added, and various other table name mappings to be performed.
1371          *
1372          *
1373          * @param $vars string|array
1374          *
1375          * May be either a field name or an array of field names. The field names
1376          * can be complete fragments of SQL, for direct inclusion into the SELECT
1377          * query. If an array is given, field aliases can be specified, for example:
1378          *
1379          *   array( 'maxrev' => 'MAX(rev_id)' )
1380          *
1381          * This includes an expression with the alias "maxrev" in the query.
1382          *
1383          * If an expression is given, care must be taken to ensure that it is
1384          * DBMS-independent.
1385          *
1386          *
1387          * @param $conds string|array
1388          *
1389          * May be either a string containing a single condition, or an array of
1390          * conditions. If an array is given, the conditions constructed from each
1391          * element are combined with AND.
1392          *
1393          * Array elements may take one of two forms:
1394          *
1395          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1396          *   - Elements with a string key are interpreted as equality conditions,
1397          *     where the key is the field name.
1398          *     - If the value of such an array element is a scalar (such as a
1399          *       string), it will be treated as data and thus quoted appropriately.
1400          *       If it is null, an IS NULL clause will be added.
1401          *     - If the value is an array, an IN(...) clause will be constructed,
1402          *       such that the field name may match any of the elements in the
1403          *       array. The elements of the array will be quoted.
1404          *
1405          * Note that expressions are often DBMS-dependent in their syntax.
1406          * DBMS-independent wrappers are provided for constructing several types of
1407          * expression commonly used in condition queries. See:
1408          *    - DatabaseBase::buildLike()
1409          *    - DatabaseBase::conditional()
1410          *
1411          *
1412          * @param $options string|array
1413          *
1414          * Optional: Array of query options. Boolean options are specified by
1415          * including them in the array as a string value with a numeric key, for
1416          * example:
1417          *
1418          *    array( 'FOR UPDATE' )
1419          *
1420          * The supported options are:
1421          *
1422          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1423          *     with LIMIT can theoretically be used for paging through a result set,
1424          *     but this is discouraged in MediaWiki for performance reasons.
1425          *
1426          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1427          *     and then the first rows are taken until the limit is reached. LIMIT
1428          *     is applied to a result set after OFFSET.
1429          *
1430          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1431          *     changed until the next COMMIT.
1432          *
1433          *   - DISTINCT: Boolean: return only unique result rows.
1434          *
1435          *   - GROUP BY: May be either an SQL fragment string naming a field or
1436          *     expression to group by, or an array of such SQL fragments.
1437          *
1438          *   - HAVING: May be either an string containing a HAVING clause or an array of
1439          *     conditions building the HAVING clause. If an array is given, the conditions
1440          *     constructed from each element are combined with AND.
1441          *
1442          *   - ORDER BY: May be either an SQL fragment giving a field name or
1443          *     expression to order by, or an array of such SQL fragments.
1444          *
1445          *   - USE INDEX: This may be either a string giving the index name to use
1446          *     for the query, or an array. If it is an associative array, each key
1447          *     gives the table name (or alias), each value gives the index name to
1448          *     use for that table. All strings are SQL fragments and so should be
1449          *     validated by the caller.
1450          *
1451          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1452          *     instead of SELECT.
1453          *
1454          * And also the following boolean MySQL extensions, see the MySQL manual
1455          * for documentation:
1456          *
1457          *    - LOCK IN SHARE MODE
1458          *    - STRAIGHT_JOIN
1459          *    - HIGH_PRIORITY
1460          *    - SQL_BIG_RESULT
1461          *    - SQL_BUFFER_RESULT
1462          *    - SQL_SMALL_RESULT
1463          *    - SQL_CALC_FOUND_ROWS
1464          *    - SQL_CACHE
1465          *    - SQL_NO_CACHE
1466          *
1467          *
1468          * @param $join_conds string|array
1469          *
1470          * Optional associative array of table-specific join conditions. In the
1471          * most common case, this is unnecessary, since the join condition can be
1472          * in $conds. However, it is useful for doing a LEFT JOIN.
1473          *
1474          * The key of the array contains the table name or alias. The value is an
1475          * array with two elements, numbered 0 and 1. The first gives the type of
1476          * join, the second is an SQL fragment giving the join condition for that
1477          * table. For example:
1478          *
1479          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1480          *
1481          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1482          *   with no rows in it will be returned. If there was a query error, a
1483          *   DBQueryError exception will be thrown, except if the "ignore errors"
1484          *   option was set, in which case false will be returned.
1485          */
1486         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1487                 $options = array(), $join_conds = array() ) {
1488                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1489
1490                 return $this->query( $sql, $fname );
1491         }
1492
1493         /**
1494          * The equivalent of DatabaseBase::select() except that the constructed SQL
1495          * is returned, instead of being immediately executed. This can be useful for
1496          * doing UNION queries, where the SQL text of each query is needed. In general,
1497          * however, callers outside of Database classes should just use select().
1498          *
1499          * @param string|array $table Table name
1500          * @param string|array $vars Field names
1501          * @param string|array $conds Conditions
1502          * @param string $fname Caller function name
1503          * @param string|array $options Query options
1504          * @param $join_conds string|array Join conditions
1505          *
1506          * @return string SQL query string.
1507          * @see DatabaseBase::select()
1508          */
1509         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1510                 $options = array(), $join_conds = array() )
1511         {
1512                 if ( is_array( $vars ) ) {
1513                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1514                 }
1515
1516                 $options = (array)$options;
1517                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1518                         ? $options['USE INDEX']
1519                         : array();
1520
1521                 if ( is_array( $table ) ) {
1522                         $from = ' FROM ' .
1523                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1524                 } elseif ( $table != '' ) {
1525                         if ( $table[0] == ' ' ) {
1526                                 $from = ' FROM ' . $table;
1527                         } else {
1528                                 $from = ' FROM ' .
1529                                         $this->tableNamesWithUseIndexOrJOIN( array( $table ), $useIndexes, array() );
1530                         }
1531                 } else {
1532                         $from = '';
1533                 }
1534
1535                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1536                         $this->makeSelectOptions( $options );
1537
1538                 if ( !empty( $conds ) ) {
1539                         if ( is_array( $conds ) ) {
1540                                 $conds = $this->makeList( $conds, LIST_AND );
1541                         }
1542                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1543                 } else {
1544                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1545                 }
1546
1547                 if ( isset( $options['LIMIT'] ) ) {
1548                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1549                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1550                 }
1551                 $sql = "$sql $postLimitTail";
1552
1553                 if ( isset( $options['EXPLAIN'] ) ) {
1554                         $sql = 'EXPLAIN ' . $sql;
1555                 }
1556
1557                 return $sql;
1558         }
1559
1560         /**
1561          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1562          * that a single row object is returned. If the query returns no rows,
1563          * false is returned.
1564          *
1565          * @param string|array $table Table name
1566          * @param string|array $vars Field names
1567          * @param array $conds Conditions
1568          * @param string $fname Caller function name
1569          * @param string|array $options Query options
1570          * @param $join_conds array|string Join conditions
1571          *
1572          * @return object|bool
1573          */
1574         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1575                 $options = array(), $join_conds = array() )
1576         {
1577                 $options = (array)$options;
1578                 $options['LIMIT'] = 1;
1579                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1580
1581                 if ( $res === false ) {
1582                         return false;
1583                 }
1584
1585                 if ( !$this->numRows( $res ) ) {
1586                         return false;
1587                 }
1588
1589                 $obj = $this->fetchObject( $res );
1590
1591                 return $obj;
1592         }
1593
1594         /**
1595          * Estimate rows in dataset.
1596          *
1597          * MySQL allows you to estimate the number of rows that would be returned
1598          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1599          * index cardinality statistics, and is notoriously inaccurate, especially
1600          * when large numbers of rows have recently been added or deleted.
1601          *
1602          * For DBMSs that don't support fast result size estimation, this function
1603          * will actually perform the SELECT COUNT(*).
1604          *
1605          * Takes the same arguments as DatabaseBase::select().
1606          *
1607          * @param string $table table name
1608          * @param array|string $vars : unused
1609          * @param array|string $conds : filters on the table
1610          * @param string $fname function name for profiling
1611          * @param array $options options for select
1612          * @return Integer: row count
1613          */
1614         public function estimateRowCount( $table, $vars = '*', $conds = '',
1615                 $fname = __METHOD__, $options = array() )
1616         {
1617                 $rows = 0;
1618                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1619
1620                 if ( $res ) {
1621                         $row = $this->fetchRow( $res );
1622                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1623                 }
1624
1625                 return $rows;
1626         }
1627
1628         /**
1629          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1630          * It's only slightly flawed. Don't use for anything important.
1631          *
1632          * @param string $sql A SQL Query
1633          *
1634          * @return string
1635          */
1636         static function generalizeSQL( $sql ) {
1637                 # This does the same as the regexp below would do, but in such a way
1638                 # as to avoid crashing php on some large strings.
1639                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1640
1641                 $sql = str_replace( "\\\\", '', $sql );
1642                 $sql = str_replace( "\\'", '', $sql );
1643                 $sql = str_replace( "\\\"", '', $sql );
1644                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1645                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1646
1647                 # All newlines, tabs, etc replaced by single space
1648                 $sql = preg_replace( '/\s+/', ' ', $sql );
1649
1650                 # All numbers => N
1651                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1652                 $sql = preg_replace( '/-?\d+/s', 'N', $sql );
1653
1654                 return $sql;
1655         }
1656
1657         /**
1658          * Determines whether a field exists in a table
1659          *
1660          * @param string $table table name
1661          * @param string $field filed to check on that table
1662          * @param string $fname calling function name (optional)
1663          * @return Boolean: whether $table has filed $field
1664          */
1665         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1666                 $info = $this->fieldInfo( $table, $field );
1667
1668                 return (bool)$info;
1669         }
1670
1671         /**
1672          * Determines whether an index exists
1673          * Usually throws a DBQueryError on failure
1674          * If errors are explicitly ignored, returns NULL on failure
1675          *
1676          * @param $table
1677          * @param $index
1678          * @param $fname string
1679          *
1680          * @return bool|null
1681          */
1682         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1683                 if ( !$this->tableExists( $table ) ) {
1684                         return null;
1685                 }
1686
1687                 $info = $this->indexInfo( $table, $index, $fname );
1688                 if ( is_null( $info ) ) {
1689                         return null;
1690                 } else {
1691                         return $info !== false;
1692                 }
1693         }
1694
1695         /**
1696          * Query whether a given table exists
1697          *
1698          * @param $table string
1699          * @param $fname string
1700          *
1701          * @return bool
1702          */
1703         public function tableExists( $table, $fname = __METHOD__ ) {
1704                 $table = $this->tableName( $table );
1705                 $old = $this->ignoreErrors( true );
1706                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1707                 $this->ignoreErrors( $old );
1708
1709                 return (bool)$res;
1710         }
1711
1712         /**
1713          * mysql_field_type() wrapper
1714          * @param $res
1715          * @param $index
1716          * @return string
1717          */
1718         public function fieldType( $res, $index ) {
1719                 if ( $res instanceof ResultWrapper ) {
1720                         $res = $res->result;
1721                 }
1722
1723                 return mysql_field_type( $res, $index );
1724         }
1725
1726         /**
1727          * Determines if a given index is unique
1728          *
1729          * @param $table string
1730          * @param $index string
1731          *
1732          * @return bool
1733          */
1734         public function indexUnique( $table, $index ) {
1735                 $indexInfo = $this->indexInfo( $table, $index );
1736
1737                 if ( !$indexInfo ) {
1738                         return null;
1739                 }
1740
1741                 return !$indexInfo[0]->Non_unique;
1742         }
1743
1744         /**
1745          * Helper for DatabaseBase::insert().
1746          *
1747          * @param $options array
1748          * @return string
1749          */
1750         protected function makeInsertOptions( $options ) {
1751                 return implode( ' ', $options );
1752         }
1753
1754         /**
1755          * INSERT wrapper, inserts an array into a table.
1756          *
1757          * $a may be either:
1758          *
1759          *   - A single associative array. The array keys are the field names, and
1760          *     the values are the values to insert. The values are treated as data
1761          *     and will be quoted appropriately. If NULL is inserted, this will be
1762          *     converted to a database NULL.
1763          *   - An array with numeric keys, holding a list of associative arrays.
1764          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1765          *     each subarray must be identical to each other, and in the same order.
1766          *
1767          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1768          * returns success.
1769          *
1770          * $options is an array of options, with boolean options encoded as values
1771          * with numeric keys, in the same style as $options in
1772          * DatabaseBase::select(). Supported options are:
1773          *
1774          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1775          *     any rows which cause duplicate key errors are not inserted. It's
1776          *     possible to determine how many rows were successfully inserted using
1777          *     DatabaseBase::affectedRows().
1778          *
1779          * @param $table   String Table name. This will be passed through
1780          *                 DatabaseBase::tableName().
1781          * @param $a       Array of rows to insert
1782          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1783          * @param array $options of options
1784          *
1785          * @return bool
1786          */
1787         public function insert( $table, $a, $fname = __METHOD__, $options = array() ) {
1788                 # No rows to insert, easy just return now
1789                 if ( !count( $a ) ) {
1790                         return true;
1791                 }
1792
1793                 $table = $this->tableName( $table );
1794
1795                 if ( !is_array( $options ) ) {
1796                         $options = array( $options );
1797                 }
1798
1799                 $fh = null;
1800                 if ( isset( $options['fileHandle'] ) ) {
1801                         $fh = $options['fileHandle'];
1802                 }
1803                 $options = $this->makeInsertOptions( $options );
1804
1805                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1806                         $multi = true;
1807                         $keys = array_keys( $a[0] );
1808                 } else {
1809                         $multi = false;
1810                         $keys = array_keys( $a );
1811                 }
1812
1813                 $sql = 'INSERT ' . $options .
1814                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1815
1816                 if ( $multi ) {
1817                         $first = true;
1818                         foreach ( $a as $row ) {
1819                                 if ( $first ) {
1820                                         $first = false;
1821                                 } else {
1822                                         $sql .= ',';
1823                                 }
1824                                 $sql .= '(' . $this->makeList( $row ) . ')';
1825                         }
1826                 } else {
1827                         $sql .= '(' . $this->makeList( $a ) . ')';
1828                 }
1829
1830                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1831                         return false;
1832                 } elseif ( $fh !== null ) {
1833                         return true;
1834                 }
1835
1836                 return (bool)$this->query( $sql, $fname );
1837         }
1838
1839         /**
1840          * Make UPDATE options for the DatabaseBase::update function
1841          *
1842          * @param array $options The options passed to DatabaseBase::update
1843          * @return string
1844          */
1845         protected function makeUpdateOptions( $options ) {
1846                 if ( !is_array( $options ) ) {
1847                         $options = array( $options );
1848                 }
1849
1850                 $opts = array();
1851
1852                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1853                         $opts[] = $this->lowPriorityOption();
1854                 }
1855
1856                 if ( in_array( 'IGNORE', $options ) ) {
1857                         $opts[] = 'IGNORE';
1858                 }
1859
1860                 return implode( ' ', $opts );
1861         }
1862
1863         /**
1864          * UPDATE wrapper. Takes a condition array and a SET array.
1865          *
1866          * @param $table  String name of the table to UPDATE. This will be passed through
1867          *                DatabaseBase::tableName().
1868          *
1869          * @param array $values  An array of values to SET. For each array element,
1870          *                the key gives the field name, and the value gives the data
1871          *                to set that field to. The data will be quoted by
1872          *                DatabaseBase::addQuotes().
1873          *
1874          * @param $conds  Array:  An array of conditions (WHERE). See
1875          *                DatabaseBase::select() for the details of the format of
1876          *                condition arrays. Use '*' to update all rows.
1877          *
1878          * @param $fname  String: The function name of the caller (from __METHOD__),
1879          *                for logging and profiling.
1880          *
1881          * @param array $options An array of UPDATE options, can be:
1882          *                   - IGNORE: Ignore unique key conflicts
1883          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1884          * @return Boolean
1885          */
1886         function update( $table, $values, $conds, $fname = __METHOD__, $options = array() ) {
1887                 $table = $this->tableName( $table );
1888                 $opts = $this->makeUpdateOptions( $options );
1889                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1890
1891                 if ( $conds !== array() && $conds !== '*' ) {
1892                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1893                 }
1894
1895                 return $this->query( $sql, $fname );
1896         }
1897
1898         /**
1899          * Makes an encoded list of strings from an array
1900          * @param array $a containing the data
1901          * @param int $mode Constant
1902          *      - LIST_COMMA:          comma separated, no field names
1903          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1904          *        the documentation for $conds in DatabaseBase::select().
1905          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1906          *      - LIST_SET:            comma separated with field names, like a SET clause
1907          *      - LIST_NAMES:          comma separated field names
1908          *
1909          * @throws MWException|DBUnexpectedError
1910          * @return string
1911          */
1912         public function makeList( $a, $mode = LIST_COMMA ) {
1913                 if ( !is_array( $a ) ) {
1914                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1915                 }
1916
1917                 $first = true;
1918                 $list = '';
1919
1920                 foreach ( $a as $field => $value ) {
1921                         if ( !$first ) {
1922                                 if ( $mode == LIST_AND ) {
1923                                         $list .= ' AND ';
1924                                 } elseif ( $mode == LIST_OR ) {
1925                                         $list .= ' OR ';
1926                                 } else {
1927                                         $list .= ',';
1928                                 }
1929                         } else {
1930                                 $first = false;
1931                         }
1932
1933                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1934                                 $list .= "($value)";
1935                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1936                                 $list .= "$value";
1937                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1938                                 if ( count( $value ) == 0 ) {
1939                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1940                                 } elseif ( count( $value ) == 1 ) {
1941                                         // Special-case single values, as IN isn't terribly efficient
1942                                         // Don't necessarily assume the single key is 0; we don't
1943                                         // enforce linear numeric ordering on other arrays here.
1944                                         $value = array_values( $value );
1945                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1946                                 } else {
1947                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1948                                 }
1949                         } elseif ( $value === null ) {
1950                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1951                                         $list .= "$field IS ";
1952                                 } elseif ( $mode == LIST_SET ) {
1953                                         $list .= "$field = ";
1954                                 }
1955                                 $list .= 'NULL';
1956                         } else {
1957                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1958                                         $list .= "$field = ";
1959                                 }
1960                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1961                         }
1962                 }
1963
1964                 return $list;
1965         }
1966
1967         /**
1968          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1969          * The keys on each level may be either integers or strings.
1970          *
1971          * @param array $data organized as 2-d
1972          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
1973          * @param string $baseKey field name to match the base-level keys to (eg 'pl_namespace')
1974          * @param string $subKey field name to match the sub-level keys to (eg 'pl_title')
1975          * @return Mixed: string SQL fragment, or false if no items in array.
1976          */
1977         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1978                 $conds = array();
1979
1980                 foreach ( $data as $base => $sub ) {
1981                         if ( count( $sub ) ) {
1982                                 $conds[] = $this->makeList(
1983                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1984                                         LIST_AND );
1985                         }
1986                 }
1987
1988                 if ( $conds ) {
1989                         return $this->makeList( $conds, LIST_OR );
1990                 } else {
1991                         // Nothing to search for...
1992                         return false;
1993                 }
1994         }
1995
1996         /**
1997          * Return aggregated value alias
1998          *
1999          * @param $valuedata
2000          * @param $valuename string
2001          *
2002          * @return string
2003          */
2004         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2005                 return $valuename;
2006         }
2007
2008         /**
2009          * @param $field
2010          * @return string
2011          */
2012         public function bitNot( $field ) {
2013                 return "(~$field)";
2014         }
2015
2016         /**
2017          * @param $fieldLeft
2018          * @param $fieldRight
2019          * @return string
2020          */
2021         public function bitAnd( $fieldLeft, $fieldRight ) {
2022                 return "($fieldLeft & $fieldRight)";
2023         }
2024
2025         /**
2026          * @param  $fieldLeft
2027          * @param  $fieldRight
2028          * @return string
2029          */
2030         public function bitOr( $fieldLeft, $fieldRight ) {
2031                 return "($fieldLeft | $fieldRight)";
2032         }
2033
2034         /**
2035          * Build a concatenation list to feed into a SQL query
2036          * @param array $stringList list of raw SQL expressions; caller is responsible for any quoting
2037          * @return String
2038          */
2039         public function buildConcat( $stringList ) {
2040                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2041         }
2042
2043         /**
2044          * Change the current database
2045          *
2046          * @todo Explain what exactly will fail if this is not overridden.
2047          *
2048          * @param $db
2049          *
2050          * @return bool Success or failure
2051          */
2052         public function selectDB( $db ) {
2053                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
2054                 # if your database engine supports a concept similar to MySQL's
2055                 # databases you may as well.
2056                 $this->mDBname = $db;
2057                 return true;
2058         }
2059
2060         /**
2061          * Get the current DB name
2062          */
2063         public function getDBname() {
2064                 return $this->mDBname;
2065         }
2066
2067         /**
2068          * Get the server hostname or IP address
2069          */
2070         public function getServer() {
2071                 return $this->mServer;
2072         }
2073
2074         /**
2075          * Format a table name ready for use in constructing an SQL query
2076          *
2077          * This does two important things: it quotes the table names to clean them up,
2078          * and it adds a table prefix if only given a table name with no quotes.
2079          *
2080          * All functions of this object which require a table name call this function
2081          * themselves. Pass the canonical name to such functions. This is only needed
2082          * when calling query() directly.
2083          *
2084          * @param string $name database table name
2085          * @param string $format One of:
2086          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2087          *            so that it can be used in a query.
2088          *   raw - Do not add identifier quotes to the table name
2089          * @return String: full database name
2090          */
2091         public function tableName( $name, $format = 'quoted' ) {
2092                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
2093                 # Skip the entire process when we have a string quoted on both ends.
2094                 # Note that we check the end so that we will still quote any use of
2095                 # use of `database`.table. But won't break things if someone wants
2096                 # to query a database table with a dot in the name.
2097                 if ( $this->isQuotedIdentifier( $name ) ) {
2098                         return $name;
2099                 }
2100
2101                 # Lets test for any bits of text that should never show up in a table
2102                 # name. Basically anything like JOIN or ON which are actually part of
2103                 # SQL queries, but may end up inside of the table value to combine
2104                 # sql. Such as how the API is doing.
2105                 # Note that we use a whitespace test rather than a \b test to avoid
2106                 # any remote case where a word like on may be inside of a table name
2107                 # surrounded by symbols which may be considered word breaks.
2108                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2109                         return $name;
2110                 }
2111
2112                 # Split database and table into proper variables.
2113                 # We reverse the explode so that database.table and table both output
2114                 # the correct table.
2115                 $dbDetails = explode( '.', $name, 2 );
2116                 if ( count( $dbDetails ) == 2 ) {
2117                         list( $database, $table ) = $dbDetails;
2118                         # We don't want any prefix added in this case
2119                         $prefix = '';
2120                 } else {
2121                         list( $table ) = $dbDetails;
2122                         if ( $wgSharedDB !== null # We have a shared database
2123                                 && $this->mForeign == false # We're not working on a foreign database
2124                                 && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
2125                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2126                         ) {
2127                                 $database = $wgSharedDB;
2128                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2129                         } else {
2130                                 $database = null;
2131                                 $prefix = $this->mTablePrefix; # Default prefix
2132                         }
2133                 }
2134
2135                 # Quote $table and apply the prefix if not quoted.
2136                 $tableName = "{$prefix}{$table}";
2137                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) ) {
2138                         $tableName = $this->addIdentifierQuotes( $tableName );
2139                 }
2140
2141                 # Quote $database and merge it with the table name if needed
2142                 if ( $database !== null ) {
2143                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2144                                 $database = $this->addIdentifierQuotes( $database );
2145                         }
2146                         $tableName = $database . '.' . $tableName;
2147                 }
2148
2149                 return $tableName;
2150         }
2151
2152         /**
2153          * Fetch a number of table names into an array
2154          * This is handy when you need to construct SQL for joins
2155          *
2156          * Example:
2157          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2158          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2159          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2160          *
2161          * @return array
2162          */
2163         public function tableNames() {
2164                 $inArray = func_get_args();
2165                 $retVal = array();
2166
2167                 foreach ( $inArray as $name ) {
2168                         $retVal[$name] = $this->tableName( $name );
2169                 }
2170
2171                 return $retVal;
2172         }
2173
2174         /**
2175          * Fetch a number of table names into an zero-indexed numerical array
2176          * This is handy when you need to construct SQL for joins
2177          *
2178          * Example:
2179          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2180          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2181          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2182          *
2183          * @return array
2184          */
2185         public function tableNamesN() {
2186                 $inArray = func_get_args();
2187                 $retVal = array();
2188
2189                 foreach ( $inArray as $name ) {
2190                         $retVal[] = $this->tableName( $name );
2191                 }
2192
2193                 return $retVal;
2194         }
2195
2196         /**
2197          * Get an aliased table name
2198          * e.g. tableName AS newTableName
2199          *
2200          * @param string $name Table name, see tableName()
2201          * @param string|bool $alias Alias (optional)
2202          * @return string SQL name for aliased table. Will not alias a table to its own name
2203          */
2204         public function tableNameWithAlias( $name, $alias = false ) {
2205                 if ( !$alias || $alias == $name ) {
2206                         return $this->tableName( $name );
2207                 } else {
2208                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2209                 }
2210         }
2211
2212         /**
2213          * Gets an array of aliased table names
2214          *
2215          * @param $tables array( [alias] => table )
2216          * @return array of strings, see tableNameWithAlias()
2217          */
2218         public function tableNamesWithAlias( $tables ) {
2219                 $retval = array();
2220                 foreach ( $tables as $alias => $table ) {
2221                         if ( is_numeric( $alias ) ) {
2222                                 $alias = $table;
2223                         }
2224                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2225                 }
2226                 return $retval;
2227         }
2228
2229         /**
2230          * Get an aliased field name
2231          * e.g. fieldName AS newFieldName
2232          *
2233          * @param string $name Field name
2234          * @param string|bool $alias Alias (optional)
2235          * @return string SQL name for aliased field. Will not alias a field to its own name
2236          */
2237         public function fieldNameWithAlias( $name, $alias = false ) {
2238                 if ( !$alias || (string)$alias === (string)$name ) {
2239                         return $name;
2240                 } else {
2241                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2242                 }
2243         }
2244
2245         /**
2246          * Gets an array of aliased field names
2247          *
2248          * @param $fields array( [alias] => field )
2249          * @return array of strings, see fieldNameWithAlias()
2250          */
2251         public function fieldNamesWithAlias( $fields ) {
2252                 $retval = array();
2253                 foreach ( $fields as $alias => $field ) {
2254                         if ( is_numeric( $alias ) ) {
2255                                 $alias = $field;
2256                         }
2257                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2258                 }
2259                 return $retval;
2260         }
2261
2262         /**
2263          * Get the aliased table name clause for a FROM clause
2264          * which might have a JOIN and/or USE INDEX clause
2265          *
2266          * @param array $tables ( [alias] => table )
2267          * @param $use_index array Same as for select()
2268          * @param $join_conds array Same as for select()
2269          * @return string
2270          */
2271         protected function tableNamesWithUseIndexOrJOIN(
2272                 $tables, $use_index = array(), $join_conds = array()
2273         ) {
2274                 $ret = array();
2275                 $retJOIN = array();
2276                 $use_index = (array)$use_index;
2277                 $join_conds = (array)$join_conds;
2278
2279                 foreach ( $tables as $alias => $table ) {
2280                         if ( !is_string( $alias ) ) {
2281                                 // No alias? Set it equal to the table name
2282                                 $alias = $table;
2283                         }
2284                         // Is there a JOIN clause for this table?
2285                         if ( isset( $join_conds[$alias] ) ) {
2286                                 list( $joinType, $conds ) = $join_conds[$alias];
2287                                 $tableClause = $joinType;
2288                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2289                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2290                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2291                                         if ( $use != '' ) {
2292                                                 $tableClause .= ' ' . $use;
2293                                         }
2294                                 }
2295                                 $on = $this->makeList( (array)$conds, LIST_AND );
2296                                 if ( $on != '' ) {
2297                                         $tableClause .= ' ON (' . $on . ')';
2298                                 }
2299
2300                                 $retJOIN[] = $tableClause;
2301                         // Is there an INDEX clause for this table?
2302                         } elseif ( isset( $use_index[$alias] ) ) {
2303                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2304                                 $tableClause .= ' ' . $this->useIndexClause(
2305                                         implode( ',', (array)$use_index[$alias] ) );
2306
2307                                 $ret[] = $tableClause;
2308                         } else {
2309                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2310
2311                                 $ret[] = $tableClause;
2312                         }
2313                 }
2314
2315                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2316                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2317                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2318
2319                 // Compile our final table clause
2320                 return implode( ' ', array( $implicitJoins, $explicitJoins ) );
2321         }
2322
2323         /**
2324          * Get the name of an index in a given table
2325          *
2326          * @param $index
2327          *
2328          * @return string
2329          */
2330         protected function indexName( $index ) {
2331                 // Backwards-compatibility hack
2332                 $renamed = array(
2333                         'ar_usertext_timestamp' => 'usertext_timestamp',
2334                         'un_user_id' => 'user_id',
2335                         'un_user_ip' => 'user_ip',
2336                 );
2337
2338                 if ( isset( $renamed[$index] ) ) {
2339                         return $renamed[$index];
2340                 } else {
2341                         return $index;
2342                 }
2343         }
2344
2345         /**
2346          * Adds quotes and backslashes.
2347          *
2348          * @param $s string
2349          *
2350          * @return string
2351          */
2352         public function addQuotes( $s ) {
2353                 if ( $s === null ) {
2354                         return 'NULL';
2355                 } else {
2356                         # This will also quote numeric values. This should be harmless,
2357                         # and protects against weird problems that occur when they really
2358                         # _are_ strings such as article titles and string->number->string
2359                         # conversion is not 1:1.
2360                         return "'" . $this->strencode( $s ) . "'";
2361                 }
2362         }
2363
2364         /**
2365          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2366          * MySQL uses `backticks` while basically everything else uses double quotes.
2367          * Since MySQL is the odd one out here the double quotes are our generic
2368          * and we implement backticks in DatabaseMysql.
2369          *
2370          * @param $s string
2371          *
2372          * @return string
2373          */
2374         public function addIdentifierQuotes( $s ) {
2375                 return '"' . str_replace( '"', '""', $s ) . '"';
2376         }
2377
2378         /**
2379          * Returns if the given identifier looks quoted or not according to
2380          * the database convention for quoting identifiers .
2381          *
2382          * @param $name string
2383          *
2384          * @return boolean
2385          */
2386         public function isQuotedIdentifier( $name ) {
2387                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2388         }
2389
2390         /**
2391          * @param $s string
2392          * @return string
2393          */
2394         protected function escapeLikeInternal( $s ) {
2395                 $s = str_replace( '\\', '\\\\', $s );
2396                 $s = $this->strencode( $s );
2397                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2398
2399                 return $s;
2400         }
2401
2402         /**
2403          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2404          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2405          * Alternatively, the function could be provided with an array of aforementioned parameters.
2406          *
2407          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2408          * for subpages of 'My page title'.
2409          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2410          *
2411          * @since 1.16
2412          * @return String: fully built LIKE statement
2413          */
2414         public function buildLike() {
2415                 $params = func_get_args();
2416
2417                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2418                         $params = $params[0];
2419                 }
2420
2421                 $s = '';
2422
2423                 foreach ( $params as $value ) {
2424                         if ( $value instanceof LikeMatch ) {
2425                                 $s .= $value->toString();
2426                         } else {
2427                                 $s .= $this->escapeLikeInternal( $value );
2428                         }
2429                 }
2430
2431                 return " LIKE '" . $s . "' ";
2432         }
2433
2434         /**
2435          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2436          *
2437          * @return LikeMatch
2438          */
2439         public function anyChar() {
2440                 return new LikeMatch( '_' );
2441         }
2442
2443         /**
2444          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2445          *
2446          * @return LikeMatch
2447          */
2448         public function anyString() {
2449                 return new LikeMatch( '%' );
2450         }
2451
2452         /**
2453          * Returns an appropriately quoted sequence value for inserting a new row.
2454          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2455          * subclass will return an integer, and save the value for insertId()
2456          *
2457          * Any implementation of this function should *not* involve reusing
2458          * sequence numbers created for rolled-back transactions.
2459          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2460          * @param $seqName string
2461          * @return null
2462          */
2463         public function nextSequenceValue( $seqName ) {
2464                 return null;
2465         }
2466
2467         /**
2468          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2469          * is only needed because a) MySQL must be as efficient as possible due to
2470          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2471          * which index to pick.  Anyway, other databases might have different
2472          * indexes on a given table.  So don't bother overriding this unless you're
2473          * MySQL.
2474          * @param $index
2475          * @return string
2476          */
2477         public function useIndexClause( $index ) {
2478                 return '';
2479         }
2480
2481         /**
2482          * REPLACE query wrapper.
2483          *
2484          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2485          * except that when there is a duplicate key error, the old row is deleted
2486          * and the new row is inserted in its place.
2487          *
2488          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2489          * perform the delete, we need to know what the unique indexes are so that
2490          * we know how to find the conflicting rows.
2491          *
2492          * It may be more efficient to leave off unique indexes which are unlikely
2493          * to collide. However if you do this, you run the risk of encountering
2494          * errors which wouldn't have occurred in MySQL.
2495          *
2496          * @param string $table The table to replace the row(s) in.
2497          * @param array $rows Can be either a single row to insert, or multiple rows,
2498          *    in the same format as for DatabaseBase::insert()
2499          * @param array $uniqueIndexes is an array of indexes. Each element may be either
2500          *    a field name or an array of field names
2501          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2502          */
2503         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2504                 $quotedTable = $this->tableName( $table );
2505
2506                 if ( count( $rows ) == 0 ) {
2507                         return;
2508                 }
2509
2510                 # Single row case
2511                 if ( !is_array( reset( $rows ) ) ) {
2512                         $rows = array( $rows );
2513                 }
2514
2515                 foreach ( $rows as $row ) {
2516                         # Delete rows which collide
2517                         if ( $uniqueIndexes ) {
2518                                 $sql = "DELETE FROM $quotedTable WHERE ";
2519                                 $first = true;
2520                                 foreach ( $uniqueIndexes as $index ) {
2521                                         if ( $first ) {
2522                                                 $first = false;
2523                                                 $sql .= '( ';
2524                                         } else {
2525                                                 $sql .= ' ) OR ( ';
2526                                         }
2527                                         if ( is_array( $index ) ) {
2528                                                 $first2 = true;
2529                                                 foreach ( $index as $col ) {
2530                                                         if ( $first2 ) {
2531                                                                 $first2 = false;
2532                                                         } else {
2533                                                                 $sql .= ' AND ';
2534                                                         }
2535                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2536                                                 }
2537                                         } else {
2538                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2539                                         }
2540                                 }
2541                                 $sql .= ' )';
2542                                 $this->query( $sql, $fname );
2543                         }
2544
2545                         # Now insert the row
2546                         $this->insert( $table, $row, $fname );
2547                 }
2548         }
2549
2550         /**
2551          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2552          * statement.
2553          *
2554          * @param string $table Table name
2555          * @param array $rows Rows to insert
2556          * @param string $fname Caller function name
2557          *
2558          * @return ResultWrapper
2559          */
2560         protected function nativeReplace( $table, $rows, $fname ) {
2561                 $table = $this->tableName( $table );
2562
2563                 # Single row case
2564                 if ( !is_array( reset( $rows ) ) ) {
2565                         $rows = array( $rows );
2566                 }
2567
2568                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2569                 $first = true;
2570
2571                 foreach ( $rows as $row ) {
2572                         if ( $first ) {
2573                                 $first = false;
2574                         } else {
2575                                 $sql .= ',';
2576                         }
2577
2578                         $sql .= '(' . $this->makeList( $row ) . ')';
2579                 }
2580
2581                 return $this->query( $sql, $fname );
2582         }
2583
2584         /**
2585          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
2586          *
2587          * This updates any conflicting rows (according to the unique indexes) using
2588          * the provided SET clause and inserts any remaining (non-conflicted) rows.
2589          *
2590          * $rows may be either:
2591          *   - A single associative array. The array keys are the field names, and
2592          *     the values are the values to insert. The values are treated as data
2593          *     and will be quoted appropriately. If NULL is inserted, this will be
2594          *     converted to a database NULL.
2595          *   - An array with numeric keys, holding a list of associative arrays.
2596          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
2597          *     each subarray must be identical to each other, and in the same order.
2598          *
2599          * It may be more efficient to leave off unique indexes which are unlikely
2600          * to collide. However if you do this, you run the risk of encountering
2601          * errors which wouldn't have occurred in MySQL.
2602          *
2603          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
2604          * returns success.
2605          *
2606          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
2607          * @param array $rows A single row or list of rows to insert
2608          * @param array $uniqueIndexes List of single field names or field name tuples
2609          * @param array $set An array of values to SET. For each array element,
2610          *                the key gives the field name, and the value gives the data
2611          *                to set that field to. The data will be quoted by
2612          *                DatabaseBase::addQuotes().
2613          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2614          * @param array $options of options
2615          *
2616          * @return bool
2617          * @since 1.22
2618          */
2619         public function upsert(
2620                 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
2621         ) {
2622                 if ( !count( $rows ) ) {
2623                         return true; // nothing to do
2624                 }
2625                 $rows = is_array( reset( $rows ) ) ? $rows : array( $rows );
2626
2627                 if ( count( $uniqueIndexes ) ) {
2628                         $clauses = array(); // list WHERE clauses that each identify a single row
2629                         foreach ( $rows as $row ) {
2630                                 foreach ( $uniqueIndexes as $index ) {
2631                                         $index = is_array( $index ) ? $index : array( $index ); // columns
2632                                         $rowKey = array(); // unique key to this row
2633                                         foreach ( $index as $column ) {
2634                                                 $rowKey[$column] = $row[$column];
2635                                         }
2636                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2637                                 }
2638                         }
2639                         $where = array( $this->makeList( $clauses, LIST_OR ) );
2640                 } else {
2641                         $where = false;
2642                 }
2643
2644                 $useTrx = !$this->mTrxLevel;
2645                 if ( $useTrx ) {
2646                         $this->begin( $fname );
2647                 }
2648                 try {
2649                         # Update any existing conflicting row(s)
2650                         if ( $where !== false ) {
2651                                 $ok = $this->update( $table, $set, $where, $fname );
2652                         } else {
2653                                 $ok = true;
2654                         }
2655                         # Now insert any non-conflicting row(s)
2656                         $ok = $this->insert( $table, $rows, $fname, array( 'IGNORE' ) ) && $ok;
2657                 } catch ( Exception $e ) {
2658                         if ( $useTrx ) {
2659                                 $this->rollback( $fname );
2660                         }
2661                         throw $e;
2662                 }
2663                 if ( $useTrx ) {
2664                         $this->commit( $fname );
2665                 }
2666
2667                 return $ok;
2668         }
2669
2670         /**
2671          * DELETE where the condition is a join.
2672          *
2673          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2674          * we use sub-selects
2675          *
2676          * For safety, an empty $conds will not delete everything. If you want to
2677          * delete all rows where the join condition matches, set $conds='*'.
2678          *
2679          * DO NOT put the join condition in $conds.
2680          *
2681          * @param $delTable   String: The table to delete from.
2682          * @param $joinTable  String: The other table.
2683          * @param $delVar     String: The variable to join on, in the first table.
2684          * @param $joinVar    String: The variable to join on, in the second table.
2685          * @param $conds      Array: Condition array of field names mapped to variables,
2686          *                    ANDed together in the WHERE clause
2687          * @param $fname      String: Calling function name (use __METHOD__) for
2688          *                    logs/profiling
2689          * @throws DBUnexpectedError
2690          */
2691         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2692                 $fname = __METHOD__ )
2693         {
2694                 if ( !$conds ) {
2695                         throw new DBUnexpectedError( $this,
2696                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2697                 }
2698
2699                 $delTable = $this->tableName( $delTable );
2700                 $joinTable = $this->tableName( $joinTable );
2701                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2702                 if ( $conds != '*' ) {
2703                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2704                 }
2705                 $sql .= ')';
2706
2707                 $this->query( $sql, $fname );
2708         }
2709
2710         /**
2711          * Returns the size of a text field, or -1 for "unlimited"
2712          *
2713          * @param $table string
2714          * @param $field string
2715          *
2716          * @return int
2717          */
2718         public function textFieldSize( $table, $field ) {
2719                 $table = $this->tableName( $table );
2720                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2721                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2722                 $row = $this->fetchObject( $res );
2723
2724                 $m = array();
2725
2726                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2727                         $size = $m[1];
2728                 } else {
2729                         $size = -1;
2730                 }
2731
2732                 return $size;
2733         }
2734
2735         /**
2736          * A string to insert into queries to show that they're low-priority, like
2737          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2738          * string and nothing bad should happen.
2739          *
2740          * @return string Returns the text of the low priority option if it is
2741          *   supported, or a blank string otherwise
2742          */
2743         public function lowPriorityOption() {
2744                 return '';
2745         }
2746
2747         /**
2748          * DELETE query wrapper.
2749          *
2750          * @param array $table Table name
2751          * @param string|array $conds of conditions. See $conds in DatabaseBase::select() for
2752          *               the format. Use $conds == "*" to delete all rows
2753          * @param string $fname name of the calling function
2754          *
2755          * @throws DBUnexpectedError
2756          * @return bool|ResultWrapper
2757          */
2758         public function delete( $table, $conds, $fname = __METHOD__ ) {
2759                 if ( !$conds ) {
2760                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2761                 }
2762
2763                 $table = $this->tableName( $table );
2764                 $sql = "DELETE FROM $table";
2765
2766                 if ( $conds != '*' ) {
2767                         if ( is_array( $conds ) ) {
2768                                 $conds = $this->makeList( $conds, LIST_AND );
2769                         }
2770                         $sql .= ' WHERE ' . $conds;
2771                 }
2772
2773                 return $this->query( $sql, $fname );
2774         }
2775
2776         /**
2777          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2778          * into another table.
2779          *
2780          * @param string $destTable The table name to insert into
2781          * @param string|array $srcTable May be either a table name, or an array of table names
2782          *    to include in a join.
2783          *
2784          * @param array $varMap must be an associative array of the form
2785          *    array( 'dest1' => 'source1', ...). Source items may be literals
2786          *    rather than field names, but strings should be quoted with
2787          *    DatabaseBase::addQuotes()
2788          *
2789          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2790          *    the details of the format of condition arrays. May be "*" to copy the
2791          *    whole table.
2792          *
2793          * @param string $fname The function name of the caller, from __METHOD__
2794          *
2795          * @param array $insertOptions Options for the INSERT part of the query, see
2796          *    DatabaseBase::insert() for details.
2797          * @param array $selectOptions Options for the SELECT part of the query, see
2798          *    DatabaseBase::select() for details.
2799          *
2800          * @return ResultWrapper
2801          */
2802         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2803                 $fname = __METHOD__,
2804                 $insertOptions = array(), $selectOptions = array() )
2805         {
2806                 $destTable = $this->tableName( $destTable );
2807
2808                 if ( is_array( $insertOptions ) ) {
2809                         $insertOptions = implode( ' ', $insertOptions );
2810                 }
2811
2812                 if ( !is_array( $selectOptions ) ) {
2813                         $selectOptions = array( $selectOptions );
2814                 }
2815
2816                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2817
2818                 if ( is_array( $srcTable ) ) {
2819                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2820                 } else {
2821                         $srcTable = $this->tableName( $srcTable );
2822                 }
2823
2824                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2825                         " SELECT $startOpts " . implode( ',', $varMap ) .
2826                         " FROM $srcTable $useIndex ";
2827
2828                 if ( $conds != '*' ) {
2829                         if ( is_array( $conds ) ) {
2830                                 $conds = $this->makeList( $conds, LIST_AND );
2831                         }
2832                         $sql .= " WHERE $conds";
2833                 }
2834
2835                 $sql .= " $tailOpts";
2836
2837                 return $this->query( $sql, $fname );
2838         }
2839
2840         /**
2841          * Construct a LIMIT query with optional offset.  This is used for query
2842          * pages.  The SQL should be adjusted so that only the first $limit rows
2843          * are returned.  If $offset is provided as well, then the first $offset
2844          * rows should be discarded, and the next $limit rows should be returned.
2845          * If the result of the query is not ordered, then the rows to be returned
2846          * are theoretically arbitrary.
2847          *
2848          * $sql is expected to be a SELECT, if that makes a difference.
2849          *
2850          * The version provided by default works in MySQL and SQLite.  It will very
2851          * likely need to be overridden for most other DBMSes.
2852          *
2853          * @param string $sql SQL query we will append the limit too
2854          * @param $limit Integer the SQL limit
2855          * @param $offset Integer|bool the SQL offset (default false)
2856          *
2857          * @throws DBUnexpectedError
2858          * @return string
2859          */
2860         public function limitResult( $sql, $limit, $offset = false ) {
2861                 if ( !is_numeric( $limit ) ) {
2862                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2863                 }
2864                 return "$sql LIMIT "
2865                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2866                         . "{$limit} ";
2867         }
2868
2869         /**
2870          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2871          * within the UNION construct.
2872          * @return Boolean
2873          */
2874         public function unionSupportsOrderAndLimit() {
2875                 return true; // True for almost every DB supported
2876         }
2877
2878         /**
2879          * Construct a UNION query
2880          * This is used for providing overload point for other DB abstractions
2881          * not compatible with the MySQL syntax.
2882          * @param array $sqls SQL statements to combine
2883          * @param $all Boolean: use UNION ALL
2884          * @return String: SQL fragment
2885          */
2886         public function unionQueries( $sqls, $all ) {
2887                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2888                 return '(' . implode( $glue, $sqls ) . ')';
2889         }
2890
2891         /**
2892          * Returns an SQL expression for a simple conditional.  This doesn't need
2893          * to be overridden unless CASE isn't supported in your DBMS.
2894          *
2895          * @param string|array $cond SQL expression which will result in a boolean value
2896          * @param string $trueVal SQL expression to return if true
2897          * @param string $falseVal SQL expression to return if false
2898          * @return String: SQL fragment
2899          */
2900         public function conditional( $cond, $trueVal, $falseVal ) {
2901                 if ( is_array( $cond ) ) {
2902                         $cond = $this->makeList( $cond, LIST_AND );
2903                 }
2904                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2905         }
2906
2907         /**
2908          * Returns a comand for str_replace function in SQL query.
2909          * Uses REPLACE() in MySQL
2910          *
2911          * @param string $orig column to modify
2912          * @param string $old column to seek
2913          * @param string $new column to replace with
2914          *
2915          * @return string
2916          */
2917         public function strreplace( $orig, $old, $new ) {
2918                 return "REPLACE({$orig}, {$old}, {$new})";
2919         }
2920
2921         /**
2922          * Determines how long the server has been up
2923          * STUB
2924          *
2925          * @return int
2926          */
2927         public function getServerUptime() {
2928                 return 0;
2929         }
2930
2931         /**
2932          * Determines if the last failure was due to a deadlock
2933          * STUB
2934          *
2935          * @return bool
2936          */
2937         public function wasDeadlock() {
2938                 return false;
2939         }
2940
2941         /**
2942          * Determines if the last failure was due to a lock timeout
2943          * STUB
2944          *
2945          * @return bool
2946          */
2947         public function wasLockTimeout() {
2948                 return false;
2949         }
2950
2951         /**
2952          * Determines if the last query error was something that should be dealt
2953          * with by pinging the connection and reissuing the query.
2954          * STUB
2955          *
2956          * @return bool
2957          */
2958         public function wasErrorReissuable() {
2959                 return false;
2960         }
2961
2962         /**
2963          * Determines if the last failure was due to the database being read-only.
2964          * STUB
2965          *
2966          * @return bool
2967          */
2968         public function wasReadOnlyError() {
2969                 return false;
2970         }
2971
2972         /**
2973          * Perform a deadlock-prone transaction.
2974          *
2975          * This function invokes a callback function to perform a set of write
2976          * queries. If a deadlock occurs during the processing, the transaction
2977          * will be rolled back and the callback function will be called again.
2978          *
2979          * Usage:
2980          *   $dbw->deadlockLoop( callback, ... );
2981          *
2982          * Extra arguments are passed through to the specified callback function.
2983          *
2984          * Returns whatever the callback function returned on its successful,
2985          * iteration, or false on error, for example if the retry limit was
2986          * reached.
2987          *
2988          * @return bool
2989          */
2990         public function deadlockLoop() {
2991                 $this->begin( __METHOD__ );
2992                 $args = func_get_args();
2993                 $function = array_shift( $args );
2994                 $oldIgnore = $this->ignoreErrors( true );
2995                 $tries = self::DEADLOCK_TRIES;
2996
2997                 if ( is_array( $function ) ) {
2998                         $fname = $function[0];
2999                 } else {
3000                         $fname = $function;
3001                 }
3002
3003                 do {
3004                         $retVal = call_user_func_array( $function, $args );
3005                         $error = $this->lastError();
3006                         $errno = $this->lastErrno();
3007                         $sql = $this->lastQuery();
3008
3009                         if ( $errno ) {
3010                                 if ( $this->wasDeadlock() ) {
3011                                         # Retry
3012                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3013                                 } else {
3014                                         $this->reportQueryError( $error, $errno, $sql, $fname );
3015                                 }
3016                         }
3017                 } while ( $this->wasDeadlock() && --$tries > 0 );
3018
3019                 $this->ignoreErrors( $oldIgnore );
3020
3021                 if ( $tries <= 0 ) {
3022                         $this->rollback( __METHOD__ );
3023                         $this->reportQueryError( $error, $errno, $sql, $fname );
3024                         return false;
3025                 } else {
3026                         $this->commit( __METHOD__ );
3027                         return $retVal;
3028                 }
3029         }
3030
3031         /**
3032          * Wait for the slave to catch up to a given master position.
3033          *
3034          * @param $pos DBMasterPos object
3035          * @param $timeout Integer: the maximum number of seconds to wait for
3036          *   synchronisation
3037          *
3038          * @return integer: zero if the slave was past that position already,
3039          *   greater than zero if we waited for some period of time, less than
3040          *   zero if we timed out.
3041          */
3042         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3043                 wfProfileIn( __METHOD__ );
3044
3045                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3046                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
3047
3048                         if ( $wait > $timeout * 1e6 ) {
3049                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
3050                                 wfProfileOut( __METHOD__ );
3051                                 return -1;
3052                         } elseif ( $wait > 0 ) {
3053                                 wfDebug( "Fake slave waiting $wait us\n" );
3054                                 usleep( $wait );
3055                                 wfProfileOut( __METHOD__ );
3056                                 return 1;
3057                         } else {
3058                                 wfDebug( "Fake slave up to date ($wait us)\n" );
3059                                 wfProfileOut( __METHOD__ );
3060                                 return 0;
3061                         }
3062                 }
3063
3064                 wfProfileOut( __METHOD__ );
3065
3066                 # Real waits are implemented in the subclass.
3067                 return 0;
3068         }
3069
3070         /**
3071          * Get the replication position of this slave
3072          *
3073          * @return DBMasterPos, or false if this is not a slave.
3074          */
3075         public function getSlavePos() {
3076                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3077                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
3078                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
3079                         return $pos;
3080                 } else {
3081                         # Stub
3082                         return false;
3083                 }
3084         }
3085
3086         /**
3087          * Get the position of this master
3088          *
3089          * @return DBMasterPos, or false if this is not a master
3090          */
3091         public function getMasterPos() {
3092                 if ( $this->mFakeMaster ) {
3093                         return new MySQLMasterPos( 'fake', microtime( true ) );
3094                 } else {
3095                         return false;
3096                 }
3097         }
3098
3099         /**
3100          * Run an anonymous function as soon as there is no transaction pending.
3101          * If there is a transaction and it is rolled back, then the callback is cancelled.
3102          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
3103          * Callbacks must commit any transactions that they begin.
3104          *
3105          * This is useful for updates to different systems or when separate transactions are needed.
3106          * For example, one might want to enqueue jobs into a system outside the database, but only
3107          * after the database is updated so that the jobs will see the data when they actually run.
3108          * It can also be used for updates that easily cause deadlocks if locks are held too long.
3109          *
3110          * @param callable $callback
3111          * @since 1.20
3112          */
3113         final public function onTransactionIdle( $callback ) {
3114                 $this->mTrxIdleCallbacks[] = array( $callback, wfGetCaller() );
3115                 if ( !$this->mTrxLevel ) {
3116                         $this->runOnTransactionIdleCallbacks();
3117                 }
3118         }
3119
3120         /**
3121          * Run an anonymous function before the current transaction commits or now if there is none.
3122          * If there is a transaction and it is rolled back, then the callback is cancelled.
3123          * Callbacks must not start nor commit any transactions.
3124          *
3125          * This is useful for updates that easily cause deadlocks if locks are held too long
3126          * but where atomicity is strongly desired for these updates and some related updates.
3127          *
3128          * @param callable $callback
3129          * @since 1.22
3130          */
3131         final public function onTransactionPreCommitOrIdle( $callback ) {
3132                 if ( $this->mTrxLevel ) {
3133                         $this->mTrxPreCommitCallbacks[] = array( $callback, wfGetCaller() );
3134                 } else {
3135                         $this->onTransactionIdle( $callback ); // this will trigger immediately
3136                 }
3137         }
3138
3139         /**
3140          * Actually any "on transaction idle" callbacks.
3141          *
3142          * @since 1.20
3143          */
3144         protected function runOnTransactionIdleCallbacks() {
3145                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
3146
3147                 $e = null; // last exception
3148                 do { // callbacks may add callbacks :)
3149                         $callbacks = $this->mTrxIdleCallbacks;
3150                         $this->mTrxIdleCallbacks = array(); // recursion guard
3151                         foreach ( $callbacks as $callback ) {
3152                                 try {
3153                                         list( $phpCallback ) = $callback;
3154                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
3155                                         call_user_func( $phpCallback );
3156                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3157                                 } catch ( Exception $e ) {}
3158                         }
3159                 } while ( count( $this->mTrxIdleCallbacks ) );
3160
3161                 if ( $e instanceof Exception ) {
3162                         throw $e; // re-throw any last exception
3163                 }
3164         }
3165
3166         /**
3167          * Actually any "on transaction pre-commit" callbacks.
3168          *
3169          * @since 1.22
3170          */
3171         protected function runOnTransactionPreCommitCallbacks() {
3172                 $e = null; // last exception
3173                 do { // callbacks may add callbacks :)
3174                         $callbacks = $this->mTrxPreCommitCallbacks;
3175                         $this->mTrxPreCommitCallbacks = array(); // recursion guard
3176                         foreach ( $callbacks as $callback ) {
3177                                 try {
3178                                         list( $phpCallback ) = $callback;
3179                                         call_user_func( $phpCallback );
3180                                 } catch ( Exception $e ) {}
3181                         }
3182                 } while ( count( $this->mTrxPreCommitCallbacks ) );
3183
3184                 if ( $e instanceof Exception ) {
3185                         throw $e; // re-throw any last exception
3186                 }
3187         }
3188
3189         /**
3190          * Begin a transaction. If a transaction is already in progress, that transaction will be committed before the
3191          * new transaction is started.
3192          *
3193          * Note that when the DBO_TRX flag is set (which is usually the case for web requests, but not for maintenance scripts),
3194          * any previous database query will have started a transaction automatically.
3195          *
3196          * Nesting of transactions is not supported. Attempts to nest transactions will cause a warning, unless the current
3197          * transaction was started automatically because of the DBO_TRX flag.
3198          *
3199          * @param $fname string
3200          */
3201         final public function begin( $fname = __METHOD__ ) {
3202                 global $wgDebugDBTransactions;
3203
3204                 if ( $this->mTrxLevel ) { // implicit commit
3205                         if ( !$this->mTrxAutomatic ) {
3206                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3207                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3208                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3209                                         " performing implicit commit!";
3210                                 wfWarn( $msg );
3211                                 wfLogDBError( $msg );
3212                         } else {
3213                                 // if the transaction was automatic and has done write operations,
3214                                 // log it if $wgDebugDBTransactions is enabled.
3215                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3216                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3217                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3218                                         );
3219                                 }
3220                         }
3221
3222                         $this->runOnTransactionPreCommitCallbacks();
3223                         $this->doCommit( $fname );
3224                         if ( $this->mTrxDoneWrites ) {
3225                                 Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3226                         }
3227                         $this->runOnTransactionIdleCallbacks();
3228                 }
3229
3230                 $this->doBegin( $fname );
3231                 $this->mTrxFname = $fname;
3232                 $this->mTrxDoneWrites = false;
3233                 $this->mTrxAutomatic = false;
3234         }
3235
3236         /**
3237          * Issues the BEGIN command to the database server.
3238          *
3239          * @see DatabaseBase::begin()
3240          * @param type $fname
3241          */
3242         protected function doBegin( $fname ) {
3243                 $this->query( 'BEGIN', $fname );
3244                 $this->mTrxLevel = 1;
3245         }
3246
3247         /**
3248          * Commits a transaction previously started using begin().
3249          * If no transaction is in progress, a warning is issued.
3250          *
3251          * Nesting of transactions is not supported.
3252          *
3253          * @param $fname string
3254          * @param string $flush Flush flag, set to 'flush' to disable warnings about explicitly committing implicit
3255          *        transactions, or calling commit when no transaction is in progress.
3256          *        This will silently break any ongoing explicit transaction. Only set the flush flag if you are sure
3257          *        that it is safe to ignore these warnings in your context.
3258          */
3259         final public function commit( $fname = __METHOD__, $flush = '' ) {
3260                 if ( $flush != 'flush' ) {
3261                         if ( !$this->mTrxLevel ) {
3262                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3263                         } elseif ( $this->mTrxAutomatic ) {
3264                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3265                         }
3266                 } else {
3267                         if ( !$this->mTrxLevel ) {
3268                                 return; // nothing to do
3269                         } elseif ( !$this->mTrxAutomatic ) {
3270                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3271                         }
3272                 }
3273
3274                 $this->runOnTransactionPreCommitCallbacks();
3275                 $this->doCommit( $fname );
3276                 if ( $this->mTrxDoneWrites ) {
3277                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3278                 }
3279                 $this->mTrxDoneWrites = false;
3280                 $this->runOnTransactionIdleCallbacks();
3281         }
3282
3283         /**
3284          * Issues the COMMIT command to the database server.
3285          *
3286          * @see DatabaseBase::commit()
3287          * @param type $fname
3288          */
3289         protected function doCommit( $fname ) {
3290                 if ( $this->mTrxLevel ) {
3291                         $this->query( 'COMMIT', $fname );
3292                         $this->mTrxLevel = 0;
3293                 }
3294         }
3295
3296         /**
3297          * Rollback a transaction previously started using begin().
3298          * If no transaction is in progress, a warning is issued.
3299          *
3300          * No-op on non-transactional databases.
3301          *
3302          * @param $fname string
3303          */
3304         final public function rollback( $fname = __METHOD__ ) {
3305                 if ( !$this->mTrxLevel ) {
3306                         wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3307                 }
3308                 $this->doRollback( $fname );
3309                 $this->mTrxIdleCallbacks = array(); // cancel
3310                 $this->mTrxPreCommitCallbacks = array(); // cancel
3311                 if ( $this->mTrxDoneWrites ) {
3312                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3313                 }
3314                 $this->mTrxDoneWrites = false;
3315         }
3316
3317         /**
3318          * Issues the ROLLBACK command to the database server.
3319          *
3320          * @see DatabaseBase::rollback()
3321          * @param type $fname
3322          */
3323         protected function doRollback( $fname ) {
3324                 if ( $this->mTrxLevel ) {
3325                         $this->query( 'ROLLBACK', $fname, true );
3326                         $this->mTrxLevel = 0;
3327                 }
3328         }
3329
3330         /**
3331          * Creates a new table with structure copied from existing table
3332          * Note that unlike most database abstraction functions, this function does not
3333          * automatically append database prefix, because it works at a lower
3334          * abstraction level.
3335          * The table names passed to this function shall not be quoted (this
3336          * function calls addIdentifierQuotes when needed).
3337          *
3338          * @param string $oldName name of table whose structure should be copied
3339          * @param string $newName name of table to be created
3340          * @param $temporary Boolean: whether the new table should be temporary
3341          * @param string $fname calling function name
3342          * @throws MWException
3343          * @return Boolean: true if operation was successful
3344          */
3345         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3346                 $fname = __METHOD__
3347         ) {
3348                 throw new MWException(
3349                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3350         }
3351
3352         /**
3353          * List all tables on the database
3354          *
3355          * @param string $prefix Only show tables with this prefix, e.g. mw_
3356          * @param string $fname calling function name
3357          * @throws MWException
3358          */
3359         function listTables( $prefix = null, $fname = __METHOD__ ) {
3360                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3361         }
3362
3363         /**
3364          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3365          * to the format used for inserting into timestamp fields in this DBMS.
3366          *
3367          * The result is unquoted, and needs to be passed through addQuotes()
3368          * before it can be included in raw SQL.
3369          *
3370          * @param $ts string|int
3371          *
3372          * @return string
3373          */
3374         public function timestamp( $ts = 0 ) {
3375                 return wfTimestamp( TS_MW, $ts );
3376         }
3377
3378         /**
3379          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3380          * to the format used for inserting into timestamp fields in this DBMS. If
3381          * NULL is input, it is passed through, allowing NULL values to be inserted
3382          * into timestamp fields.
3383          *
3384          * The result is unquoted, and needs to be passed through addQuotes()
3385          * before it can be included in raw SQL.
3386          *
3387          * @param $ts string|int
3388          *
3389          * @return string
3390          */
3391         public function timestampOrNull( $ts = null ) {
3392                 if ( is_null( $ts ) ) {
3393                         return null;
3394                 } else {
3395                         return $this->timestamp( $ts );
3396                 }
3397         }
3398
3399         /**
3400          * Take the result from a query, and wrap it in a ResultWrapper if
3401          * necessary. Boolean values are passed through as is, to indicate success
3402          * of write queries or failure.
3403          *
3404          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3405          * resource, and it was necessary to call this function to convert it to
3406          * a wrapper. Nowadays, raw database objects are never exposed to external
3407          * callers, so this is unnecessary in external code. For compatibility with
3408          * old code, ResultWrapper objects are passed through unaltered.
3409          *
3410          * @param $result bool|ResultWrapper
3411          *
3412          * @return bool|ResultWrapper
3413          */
3414         public function resultObject( $result ) {
3415                 if ( empty( $result ) ) {
3416                         return false;
3417                 } elseif ( $result instanceof ResultWrapper ) {
3418                         return $result;
3419                 } elseif ( $result === true ) {
3420                         // Successful write query
3421                         return $result;
3422                 } else {
3423                         return new ResultWrapper( $this, $result );
3424                 }
3425         }
3426
3427         /**
3428          * Ping the server and try to reconnect if it there is no connection
3429          *
3430          * @return bool Success or failure
3431          */
3432         public function ping() {
3433                 # Stub.  Not essential to override.
3434                 return true;
3435         }
3436
3437         /**
3438          * Get slave lag. Currently supported only by MySQL.
3439          *
3440          * Note that this function will generate a fatal error on many
3441          * installations. Most callers should use LoadBalancer::safeGetLag()
3442          * instead.
3443          *
3444          * @return int Database replication lag in seconds
3445          */
3446         public function getLag() {
3447                 return intval( $this->mFakeSlaveLag );
3448         }
3449
3450         /**
3451          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3452          *
3453          * @return int
3454          */
3455         function maxListLen() {
3456                 return 0;
3457         }
3458
3459         /**
3460          * Some DBMSs have a special format for inserting into blob fields, they
3461          * don't allow simple quoted strings to be inserted. To insert into such
3462          * a field, pass the data through this function before passing it to
3463          * DatabaseBase::insert().
3464          * @param $b string
3465          * @return string
3466          */
3467         public function encodeBlob( $b ) {
3468                 return $b;
3469         }
3470
3471         /**
3472          * Some DBMSs return a special placeholder object representing blob fields
3473          * in result objects. Pass the object through this function to return the
3474          * original string.
3475          * @param $b string
3476          * @return string
3477          */
3478         public function decodeBlob( $b ) {
3479                 return $b;
3480         }
3481
3482         /**
3483          * Override database's default behavior. $options include:
3484          *     'connTimeout' : Set the connection timeout value in seconds.
3485          *                     May be useful for very long batch queries such as
3486          *                     full-wiki dumps, where a single query reads out over
3487          *                     hours or days.
3488          *
3489          * @param $options Array
3490          * @return void
3491          */
3492         public function setSessionOptions( array $options ) {
3493         }
3494
3495         /**
3496          * Read and execute SQL commands from a file.
3497          *
3498          * Returns true on success, error string or exception on failure (depending
3499          * on object's error ignore settings).
3500          *
3501          * @param string $filename File name to open
3502          * @param bool|callable $lineCallback Optional function called before reading each line
3503          * @param bool|callable $resultCallback Optional function called for each MySQL result
3504          * @param bool|string $fname Calling function name or false if name should be
3505          *      generated dynamically using $filename
3506          * @param bool|callable $inputCallback Callback: Optional function called for each complete line sent
3507          * @throws MWException
3508          * @throws Exception|MWException
3509          * @return bool|string
3510          */
3511         public function sourceFile(
3512                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3513         ) {
3514                 wfSuppressWarnings();
3515                 $fp = fopen( $filename, 'r' );
3516                 wfRestoreWarnings();
3517
3518                 if ( false === $fp ) {
3519                         throw new MWException( "Could not open \"{$filename}\".\n" );
3520                 }
3521
3522                 if ( !$fname ) {
3523                         $fname = __METHOD__ . "( $filename )";
3524                 }
3525
3526                 try {
3527                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3528                 }
3529                 catch ( MWException $e ) {
3530                         fclose( $fp );
3531                         throw $e;
3532                 }
3533
3534                 fclose( $fp );
3535
3536                 return $error;
3537         }
3538
3539         /**
3540          * Get the full path of a patch file. Originally based on archive()
3541          * from updaters.inc. Keep in mind this always returns a patch, as
3542          * it fails back to MySQL if no DB-specific patch can be found
3543          *
3544          * @param string $patch The name of the patch, like patch-something.sql
3545          * @return String Full path to patch file
3546          */
3547         public function patchPath( $patch ) {
3548                 global $IP;
3549
3550                 $dbType = $this->getType();
3551                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3552                         return "$IP/maintenance/$dbType/archives/$patch";
3553                 } else {
3554                         return "$IP/maintenance/archives/$patch";
3555                 }
3556         }
3557
3558         /**
3559          * Set variables to be used in sourceFile/sourceStream, in preference to the
3560          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3561          * all. If it's set to false, $GLOBALS will be used.
3562          *
3563          * @param bool|array $vars mapping variable name to value.
3564          */
3565         public function setSchemaVars( $vars ) {
3566                 $this->mSchemaVars = $vars;
3567         }
3568
3569         /**
3570          * Read and execute commands from an open file handle.
3571          *
3572          * Returns true on success, error string or exception on failure (depending
3573          * on object's error ignore settings).
3574          *
3575          * @param $fp Resource: File handle
3576          * @param $lineCallback Callback: Optional function called before reading each query
3577          * @param $resultCallback Callback: Optional function called for each MySQL result
3578          * @param string $fname Calling function name
3579          * @param $inputCallback Callback: Optional function called for each complete query sent
3580          * @return bool|string
3581          */
3582         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3583                 $fname = __METHOD__, $inputCallback = false )
3584         {
3585                 $cmd = '';
3586
3587                 while ( !feof( $fp ) ) {
3588                         if ( $lineCallback ) {
3589                                 call_user_func( $lineCallback );
3590                         }
3591
3592                         $line = trim( fgets( $fp ) );
3593
3594                         if ( $line == '' ) {
3595                                 continue;
3596                         }
3597
3598                         if ( '-' == $line[0] && '-' == $line[1] ) {
3599                                 continue;
3600                         }
3601
3602                         if ( $cmd != '' ) {
3603                                 $cmd .= ' ';
3604                         }
3605
3606                         $done = $this->streamStatementEnd( $cmd, $line );
3607
3608                         $cmd .= "$line\n";
3609
3610                         if ( $done || feof( $fp ) ) {
3611                                 $cmd = $this->replaceVars( $cmd );
3612
3613                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3614                                         $res = $this->query( $cmd, $fname );
3615
3616                                         if ( $resultCallback ) {
3617                                                 call_user_func( $resultCallback, $res, $this );
3618                                         }
3619
3620                                         if ( false === $res ) {
3621                                                 $err = $this->lastError();
3622                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3623                                         }
3624                                 }
3625                                 $cmd = '';
3626                         }
3627                 }
3628
3629                 return true;
3630         }
3631
3632         /**
3633          * Called by sourceStream() to check if we've reached a statement end
3634          *
3635          * @param string $sql SQL assembled so far
3636          * @param string $newLine New line about to be added to $sql
3637          * @return Bool Whether $newLine contains end of the statement
3638          */
3639         public function streamStatementEnd( &$sql, &$newLine ) {
3640                 if ( $this->delimiter ) {
3641                         $prev = $newLine;
3642                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3643                         if ( $newLine != $prev ) {
3644                                 return true;
3645                         }
3646                 }
3647                 return false;
3648         }
3649
3650         /**
3651          * Database independent variable replacement. Replaces a set of variables
3652          * in an SQL statement with their contents as given by $this->getSchemaVars().
3653          *
3654          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3655          *
3656          * - '{$var}' should be used for text and is passed through the database's
3657          *   addQuotes method.
3658          * - `{$var}` should be used for identifiers (eg: table and database names),
3659          *   it is passed through the database's addIdentifierQuotes method which
3660          *   can be overridden if the database uses something other than backticks.
3661          * - / *$var* / is just encoded, besides traditional table prefix and
3662          *   table options its use should be avoided.
3663          *
3664          * @param string $ins SQL statement to replace variables in
3665          * @return String The new SQL statement with variables replaced
3666          */
3667         protected function replaceSchemaVars( $ins ) {
3668                 $vars = $this->getSchemaVars();
3669                 foreach ( $vars as $var => $value ) {
3670                         // replace '{$var}'
3671                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3672                         // replace `{$var}`
3673                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3674                         // replace /*$var*/
3675                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3676                 }
3677                 return $ins;
3678         }
3679
3680         /**
3681          * Replace variables in sourced SQL
3682          *
3683          * @param $ins string
3684          *
3685          * @return string
3686          */
3687         protected function replaceVars( $ins ) {
3688                 $ins = $this->replaceSchemaVars( $ins );
3689
3690                 // Table prefixes
3691                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3692                         array( $this, 'tableNameCallback' ), $ins );
3693
3694                 // Index names
3695                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3696                         array( $this, 'indexNameCallback' ), $ins );
3697
3698                 return $ins;
3699         }
3700
3701         /**
3702          * Get schema variables. If none have been set via setSchemaVars(), then
3703          * use some defaults from the current object.
3704          *
3705          * @return array
3706          */
3707         protected function getSchemaVars() {
3708                 if ( $this->mSchemaVars ) {
3709                         return $this->mSchemaVars;
3710                 } else {
3711                         return $this->getDefaultSchemaVars();
3712                 }
3713         }
3714
3715         /**
3716          * Get schema variables to use if none have been set via setSchemaVars().
3717          *
3718          * Override this in derived classes to provide variables for tables.sql
3719          * and SQL patch files.
3720          *
3721          * @return array
3722          */
3723         protected function getDefaultSchemaVars() {
3724                 return array();
3725         }
3726
3727         /**
3728          * Table name callback
3729          *
3730          * @param $matches array
3731          *
3732          * @return string
3733          */
3734         protected function tableNameCallback( $matches ) {
3735                 return $this->tableName( $matches[1] );
3736         }
3737
3738         /**
3739          * Index name callback
3740          *
3741          * @param $matches array
3742          *
3743          * @return string
3744          */
3745         protected function indexNameCallback( $matches ) {
3746                 return $this->indexName( $matches[1] );
3747         }
3748
3749         /**
3750          * Check to see if a named lock is available. This is non-blocking.
3751          *
3752          * @param string $lockName name of lock to poll
3753          * @param string $method name of method calling us
3754          * @return Boolean
3755          * @since 1.20
3756          */
3757         public function lockIsFree( $lockName, $method ) {
3758                 return true;
3759         }
3760
3761         /**
3762          * Acquire a named lock
3763          *
3764          * Abstracted from Filestore::lock() so child classes can implement for
3765          * their own needs.
3766          *
3767          * @param string $lockName name of lock to aquire
3768          * @param string $method name of method calling us
3769          * @param $timeout Integer: timeout
3770          * @return Boolean
3771          */
3772         public function lock( $lockName, $method, $timeout = 5 ) {
3773                 return true;
3774         }
3775
3776         /**
3777          * Release a lock.
3778          *
3779          * @param string $lockName Name of lock to release
3780          * @param string $method Name of method calling us
3781          *
3782          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3783          * by this thread (in which case the lock is not released), and NULL if the named
3784          * lock did not exist
3785          */
3786         public function unlock( $lockName, $method ) {
3787                 return true;
3788         }
3789
3790         /**
3791          * Lock specific tables
3792          *
3793          * @param array $read of tables to lock for read access
3794          * @param array $write of tables to lock for write access
3795          * @param string $method name of caller
3796          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
3797          *
3798          * @return bool
3799          */
3800         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3801                 return true;
3802         }
3803
3804         /**
3805          * Unlock specific tables
3806          *
3807          * @param string $method the caller
3808          *
3809          * @return bool
3810          */
3811         public function unlockTables( $method ) {
3812                 return true;
3813         }
3814
3815         /**
3816          * Delete a table
3817          * @param $tableName string
3818          * @param $fName string
3819          * @return bool|ResultWrapper
3820          * @since 1.18
3821          */
3822         public function dropTable( $tableName, $fName = __METHOD__ ) {
3823                 if ( !$this->tableExists( $tableName, $fName ) ) {
3824                         return false;
3825                 }
3826                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3827                 if ( $this->cascadingDeletes() ) {
3828                         $sql .= " CASCADE";
3829                 }
3830                 return $this->query( $sql, $fName );
3831         }
3832
3833         /**
3834          * Get search engine class. All subclasses of this need to implement this
3835          * if they wish to use searching.
3836          *
3837          * @return String
3838          */
3839         public function getSearchEngine() {
3840                 return 'SearchEngineDummy';
3841         }
3842
3843         /**
3844          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3845          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3846          * because "i" sorts after all numbers.
3847          *
3848          * @return String
3849          */
3850         public function getInfinity() {
3851                 return 'infinity';
3852         }
3853
3854         /**
3855          * Encode an expiry time into the DBMS dependent format
3856          *
3857          * @param string $expiry timestamp for expiry, or the 'infinity' string
3858          * @return String
3859          */
3860         public function encodeExpiry( $expiry ) {
3861                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3862                         ? $this->getInfinity()
3863                         : $this->timestamp( $expiry );
3864         }
3865
3866         /**
3867          * Decode an expiry time into a DBMS independent format
3868          *
3869          * @param string $expiry DB timestamp field value for expiry
3870          * @param $format integer: TS_* constant, defaults to TS_MW
3871          * @return String
3872          */
3873         public function decodeExpiry( $expiry, $format = TS_MW ) {
3874                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3875                         ? 'infinity'
3876                         : wfTimestamp( $format, $expiry );
3877         }
3878
3879         /**
3880          * Allow or deny "big selects" for this session only. This is done by setting
3881          * the sql_big_selects session variable.
3882          *
3883          * This is a MySQL-specific feature.
3884          *
3885          * @param $value Mixed: true for allow, false for deny, or "default" to
3886          *   restore the initial value
3887          */
3888         public function setBigSelects( $value = true ) {
3889                 // no-op
3890         }
3891
3892         /**
3893          * @since 1.19
3894          */
3895         public function __toString() {
3896                 return (string)$this->mConn;
3897         }
3898
3899         /**
3900          * Run a few simple sanity checks
3901          */
3902         public function __destruct() {
3903                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
3904                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
3905                 }
3906                 if ( count( $this->mTrxIdleCallbacks ) || count( $this->mTrxPreCommitCallbacks ) ) {
3907                         $callers = array();
3908                         foreach ( $this->mTrxIdleCallbacks as $callbackInfo ) {
3909                                 $callers[] = $callbackInfo[1];
3910
3911                         }
3912                         $callers = implode( ', ', $callers );
3913                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
3914                 }
3915         }
3916 }