includes/db/Database.php

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