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