includes/db/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * @file
   6  * @ingroup Database
   7  * This file deals with database interface functions
   8  * and query specifics/optimisations
   9  */
  10
  11 /** Number of times to re-try an operation in case of deadlock */
  12 define( 'DEADLOCK_TRIES', 4 );
  13 /** Minimum time to wait before retry, in microseconds */
  14 define( 'DEADLOCK_DELAY_MIN', 500000 );
  15 /** Maximum time to wait before retry */
  16 define( 'DEADLOCK_DELAY_MAX', 1500000 );
  17
  18 /**
  19  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  20  * following must be implemented to support MediaWiki
  21  *
  22  * @file
  23  * @ingroup Database
  24  */
  25 interface DatabaseType {
  26         /**
  27          * Get the type of the DBMS, as it appears in $wgDBtype.
  28          *
  29          * @return string
  30          */
  31         function getType();
  32
  33         /**
  34          * Open a connection to the database. Usually aborts on failure
  35          *
  36          * @param $server String: database server host
  37          * @param $user String: database user name
  38          * @param $password String: database user password
  39          * @param $dbName String: database name
  40          * @return bool
  41          * @throws DBConnectionError
  42          */
  43         function open( $server, $user, $password, $dbName );
  44
  45         /**
  46          * Fetch the next row from the given result object, in object form.
  47          * Fields can be retrieved with $row->fieldname, with fields acting like
  48          * member variables.
  49          *
  50          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  51          * @return Row object
  52          * @throws DBUnexpectedError Thrown if the database returns an error
  53          */
  54         function fetchObject( $res );
  55
  56         /**
  57          * Fetch the next row from the given result object, in associative array
  58          * form.  Fields are retrieved with $row['fieldname'].
  59          *
  60          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  61          * @return Row object
  62          * @throws DBUnexpectedError Thrown if the database returns an error
  63          */
  64         function fetchRow( $res );
  65
  66         /**
  67          * Get the number of rows in a result object
  68          *
  69          * @param $res Mixed: A SQL result
  70          * @return int
  71          */
  72         function numRows( $res );
  73
  74         /**
  75          * Get the number of fields in a result object
  76          * @see http://www.php.net/mysql_num_fields
  77          *
  78          * @param $res Mixed: A SQL result
  79          * @return int
  80          */
  81         function numFields( $res );
  82
  83         /**
  84          * Get a field name in a result object
  85          * @see http://www.php.net/mysql_field_name
  86          *
  87          * @param $res Mixed: A SQL result
  88          * @param $n Integer
  89          * @return string
  90          */
  91         function fieldName( $res, $n );
  92
  93         /**
  94          * Get the inserted value of an auto-increment row
  95          *
  96          * The value inserted should be fetched from nextSequenceValue()
  97          *
  98          * Example:
  99          * $id = $dbw->nextSequenceValue('page_page_id_seq');
 100          * $dbw->insert('page',array('page_id' => $id));
 101          * $id = $dbw->insertId();
 102          *
 103          * @return int
 104          */
 105         function insertId();
 106
 107         /**
 108          * Change the position of the cursor in a result object
 109          * @see http://www.php.net/mysql_data_seek
 110          *
 111          * @param $res Mixed: A SQL result
 112          * @param $row Mixed: Either MySQL row or ResultWrapper
 113          */
 114         function dataSeek( $res, $row );
 115
 116         /**
 117          * Get the last error number
 118          * @see http://www.php.net/mysql_errno
 119          *
 120          * @return int
 121          */
 122         function lastErrno();
 123
 124         /**
 125          * Get a description of the last error
 126          * @see http://www.php.net/mysql_error
 127          *
 128          * @return string
 129          */
 130         function lastError();
 131
 132         /**
 133          * mysql_fetch_field() wrapper
 134          * Returns false if the field doesn't exist
 135          *
 136          * @param $table string: table name
 137          * @param $field string: field name
 138          *
 139          * @return Field
 140          */
 141         function fieldInfo( $table, $field );
 142
 143         /**
 144          * Get information about an index into an object
 145          * @param $table string: Table name
 146          * @param $index string: Index name
 147          * @param $fname string: Calling function name
 148          * @return Mixed: Database-specific index description class or false if the index does not exist
 149          */
 150         function indexInfo( $table, $index, $fname = 'Database::indexInfo' );
 151
 152         /**
 153          * Get the number of rows affected by the last write query
 154          * @see http://www.php.net/mysql_affected_rows
 155          *
 156          * @return int
 157          */
 158         function affectedRows();
 159
 160         /**
 161          * Wrapper for addslashes()
 162          *
 163          * @param $s string: to be slashed.
 164          * @return string: slashed string.
 165          */
 166         function strencode( $s );
 167
 168         /**
 169          * Returns a wikitext link to the DB's website, e.g.,
 170          *     return "[http://www.mysql.com/ MySQL]";
 171          * Should at least contain plain text, if for some reason
 172          * your database has no website.
 173          *
 174          * @return string: wikitext of a link to the server software's web site
 175          */
 176         static function getSoftwareLink();
 177
 178         /**
 179          * A string describing the current software version, like from
 180          * mysql_get_server_info().
 181          *
 182          * @return string: Version information from the database server.
 183          */
 184         function getServerVersion();
 185
 186         /**
 187          * A string describing the current software version, and possibly
 188          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 189          * Use getServerVersion() to get machine-friendly information.
 190          *
 191          * @return string: Version information from the database server
 192          */
 193         function getServerInfo();
 194 }
 195
 196 /**
 197  * Database abstraction object
 198  * @ingroup Database
 199  */
 200 abstract class DatabaseBase implements DatabaseType {
 201
 202 # ------------------------------------------------------------------------------
 203 # Variables
 204 # ------------------------------------------------------------------------------
 205
 206         protected $mLastQuery = '';
 207         protected $mDoneWrites = false;
 208         protected $mPHPError = false;
 209
 210         protected $mServer, $mUser, $mPassword, $mDBname;
 211
 212         /**
 213          * @var DatabaseBase
 214          */
 215         protected $mConn = null;
 216         protected $mOpened = false;
 217
 218         protected $mTablePrefix;
 219         protected $mFlags;
 220         protected $mTrxLevel = 0;
 221         protected $mErrorCount = 0;
 222         protected $mLBInfo = array();
 223         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 224         protected $mDefaultBigSelects = null;
 225         protected $mSchemaVars = false;
 226
 227         protected $preparedArgs;
 228
 229         protected $htmlErrors;
 230
 231         protected $delimiter = ';';
 232
 233 # ------------------------------------------------------------------------------
 234 # Accessors
 235 # ------------------------------------------------------------------------------
 236         # These optionally set a variable and return the previous state
 237
 238         /**
 239          * A string describing the current software version, and possibly
 240          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 241          * Use getServerVersion() to get machine-friendly information.
 242          *
 243          * @return string: Version information from the database server
 244          */
 245         public function getServerInfo() {
 246                 return $this->getServerVersion();
 247         }
 248
 249         /**
 250          * Boolean, controls output of large amounts of debug information.
 251          * @param $debug bool|null
 252          *   - true to enable debugging
 253          *   - false to disable debugging
 254          *   - omitted or null to do nothing
 255          *
 256          * @return bool|null previous value of the flag
 257          */
 258         function debug( $debug = null ) {
 259                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 260         }
 261
 262         /**
 263          * Turns buffering of SQL result sets on (true) or off (false). Default is
 264          * "on".
 265          *
 266          * Unbuffered queries are very troublesome in MySQL:
 267          *
 268          *   - If another query is executed while the first query is being read
 269          *     out, the first query is killed. This means you can't call normal
 270          *     MediaWiki functions while you are reading an unbuffered query result
 271          *     from a normal wfGetDB() connection.
 272          *
 273          *   - Unbuffered queries cause the MySQL server to use large amounts of
 274          *     memory and to hold broad locks which block other queries.
 275          *
 276          * If you want to limit client-side memory, it's almost always better to
 277          * split up queries into batches using a LIMIT clause than to switch off
 278          * buffering.
 279          *
 280          * @param $buffer null|bool
 281          *
 282          * @return null|bool The previous value of the flag
 283          */
 284         function bufferResults( $buffer = null ) {
 285                 if ( is_null( $buffer ) ) {
 286                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 287                 } else {
 288                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 289                 }
 290         }
 291
 292         /**
 293          * Turns on (false) or off (true) the automatic generation and sending
 294          * of a "we're sorry, but there has been a database error" page on
 295          * database errors. Default is on (false). When turned off, the
 296          * code should use lastErrno() and lastError() to handle the
 297          * situation as appropriate.
 298          *
 299          * @param $ignoreErrors bool|null
 300          *
 301          * @return bool The previous value of the flag.
 302          */
 303         function ignoreErrors( $ignoreErrors = null ) {
 304                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 305         }
 306
 307         /**
 308          * Gets or sets the current transaction level.
 309          *
 310          * Historically, transactions were allowed to be "nested". This is no
 311          * longer supported, so this function really only returns a boolean.
 312          *
 313          * @param $level int An integer (0 or 1), or omitted to leave it unchanged.
 314          * @return int The previous value
 315          */
 316         function trxLevel( $level = null ) {
 317                 return wfSetVar( $this->mTrxLevel, $level );
 318         }
 319
 320         /**
 321          * Get/set the number of errors logged. Only useful when errors are ignored
 322          * @param $count int The count to set, or omitted to leave it unchanged.
 323          * @return int The error count
 324          */
 325         function errorCount( $count = null ) {
 326                 return wfSetVar( $this->mErrorCount, $count );
 327         }
 328
 329         /**
 330          * Get/set the table prefix.
 331          * @param $prefix string The table prefix to set, or omitted to leave it unchanged.
 332          * @return string The previous table prefix.
 333          */
 334         function tablePrefix( $prefix = null ) {
 335                 return wfSetVar( $this->mTablePrefix, $prefix );
 336         }
 337
 338         /**
 339          * Get properties passed down from the server info array of the load
 340          * balancer.
 341          *
 342          * @param $name string The entry of the info array to get, or null to get the
 343          *   whole array
 344          *
 345          * @return LoadBalancer|null
 346          */
 347         function getLBInfo( $name = null ) {
 348                 if ( is_null( $name ) ) {
 349                         return $this->mLBInfo;
 350                 } else {
 351                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 352                                 return $this->mLBInfo[$name];
 353                         } else {
 354                                 return null;
 355                         }
 356                 }
 357         }
 358
 359         /**
 360          * Set the LB info array, or a member of it. If called with one parameter,
 361          * the LB info array is set to that parameter. If it is called with two
 362          * parameters, the member with the given name is set to the given value.
 363          *
 364          * @param $name
 365          * @param $value
 366          */
 367         function setLBInfo( $name, $value = null ) {
 368                 if ( is_null( $value ) ) {
 369                         $this->mLBInfo = $name;
 370                 } else {
 371                         $this->mLBInfo[$name] = $value;
 372                 }
 373         }
 374
 375         /**
 376          * Set lag time in seconds for a fake slave
 377          *
 378          * @param $lag int
 379          */
 380         function setFakeSlaveLag( $lag ) {
 381                 $this->mFakeSlaveLag = $lag;
 382         }
 383
 384         /**
 385          * Make this connection a fake master
 386          *
 387          * @param $enabled bool
 388          */
 389         function setFakeMaster( $enabled = true ) {
 390                 $this->mFakeMaster = $enabled;
 391         }
 392
 393         /**
 394          * Returns true if this database supports (and uses) cascading deletes
 395          *
 396          * @return bool
 397          */
 398         function cascadingDeletes() {
 399                 return false;
 400         }
 401
 402         /**
 403          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 404          *
 405          * @return bool
 406          */
 407         function cleanupTriggers() {
 408                 return false;
 409         }
 410
 411         /**
 412          * Returns true if this database is strict about what can be put into an IP field.
 413          * Specifically, it uses a NULL value instead of an empty string.
 414          *
 415          * @return bool
 416          */
 417         function strictIPs() {
 418                 return false;
 419         }
 420
 421         /**
 422          * Returns true if this database uses timestamps rather than integers
 423          *
 424          * @return bool
 425         */
 426         function realTimestamps() {
 427                 return false;
 428         }
 429
 430         /**
 431          * Returns true if this database does an implicit sort when doing GROUP BY
 432          *
 433          * @return bool
 434          */
 435         function implicitGroupby() {
 436                 return true;
 437         }
 438
 439         /**
 440          * Returns true if this database does an implicit order by when the column has an index
 441          * For example: SELECT page_title FROM page LIMIT 1
 442          *
 443          * @return bool
 444          */
 445         function implicitOrderby() {
 446                 return true;
 447         }
 448
 449         /**
 450          * Returns true if this database requires that SELECT DISTINCT queries require that all
 451            ORDER BY expressions occur in the SELECT list per the SQL92 standard
 452          *
 453          * @return bool
 454          */
 455         function standardSelectDistinct() {
 456                 return true;
 457         }
 458
 459         /**
 460          * Returns true if this database can do a native search on IP columns
 461          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 462          *
 463          * @return bool
 464          */
 465         function searchableIPs() {
 466                 return false;
 467         }
 468
 469         /**
 470          * Returns true if this database can use functional indexes
 471          *
 472          * @return bool
 473          */
 474         function functionalIndexes() {
 475                 return false;
 476         }
 477
 478         /**
 479          * Return the last query that went through DatabaseBase::query()
 480          * @return String
 481          */
 482         function lastQuery() {
 483                 return $this->mLastQuery;
 484         }
 485
 486         /**
 487          * Returns true if the connection may have been used for write queries.
 488          * Should return true if unsure.
 489          *
 490          * @return bool
 491          */
 492         function doneWrites() {
 493                 return $this->mDoneWrites;
 494         }
 495
 496         /**
 497          * Is a connection to the database open?
 498          * @return Boolean
 499          */
 500         function isOpen() {
 501                 return $this->mOpened;
 502         }
 503
 504         /**
 505          * Set a flag for this connection
 506          *
 507          * @param $flag Integer: DBO_* constants from Defines.php:
 508          *   - DBO_DEBUG: output some debug info (same as debug())
 509          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 510          *   - DBO_IGNORE: ignore errors (same as ignoreErrors())
 511          *   - DBO_TRX: automatically start transactions
 512          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 513          *       and removes it in command line mode
 514          *   - DBO_PERSISTENT: use persistant database connection
 515          */
 516         function setFlag( $flag ) {
 517                 $this->mFlags |= $flag;
 518         }
 519
 520         /**
 521          * Clear a flag for this connection
 522          *
 523          * @param $flag: same as setFlag()'s $flag param
 524          */
 525         function clearFlag( $flag ) {
 526                 $this->mFlags &= ~$flag;
 527         }
 528
 529         /**
 530          * Returns a boolean whether the flag $flag is set for this connection
 531          *
 532          * @param $flag: same as setFlag()'s $flag param
 533          * @return Boolean
 534          */
 535         function getFlag( $flag ) {
 536                 return !!( $this->mFlags & $flag );
 537         }
 538
 539         /**
 540          * General read-only accessor
 541          *
 542          * @param $name string
 543          *
 544          * @return string
 545          */
 546         function getProperty( $name ) {
 547                 return $this->$name;
 548         }
 549
 550         /**
 551          * @return string
 552          */
 553         function getWikiID() {
 554                 if ( $this->mTablePrefix ) {
 555                         return "{$this->mDBname}-{$this->mTablePrefix}";
 556                 } else {
 557                         return $this->mDBname;
 558                 }
 559         }
 560
 561         /**
 562          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 563          *
 564          * @return string
 565          */
 566         public function getSchemaPath() {
 567                 global $IP;
 568                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 569                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 570                 } else {
 571                         return "$IP/maintenance/tables.sql";
 572                 }
 573         }
 574
 575 # ------------------------------------------------------------------------------
 576 # Other functions
 577 # ------------------------------------------------------------------------------
 578
 579         /**
 580          * Constructor.
 581          * @param $server String: database server host
 582          * @param $user String: database user name
 583          * @param $password String: database user password
 584          * @param $dbName String: database name
 585          * @param $flags
 586          * @param $tablePrefix String: database table prefixes. By default use the prefix gave in LocalSettings.php
 587          */
 588         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 589                 $flags = 0, $tablePrefix = 'get from global'
 590         ) {
 591                 global $wgDBprefix, $wgCommandLineMode;
 592
 593                 $this->mFlags = $flags;
 594
 595                 if ( $this->mFlags & DBO_DEFAULT ) {
 596                         if ( $wgCommandLineMode ) {
 597                                 $this->mFlags &= ~DBO_TRX;
 598                         } else {
 599                                 $this->mFlags |= DBO_TRX;
 600                         }
 601                 }
 602
 603                 /** Get the default table prefix*/
 604                 if ( $tablePrefix == 'get from global' ) {
 605                         $this->mTablePrefix = $wgDBprefix;
 606                 } else {
 607                         $this->mTablePrefix = $tablePrefix;
 608                 }
 609
 610                 if ( $user ) {
 611                         $this->open( $server, $user, $password, $dbName );
 612                 }
 613         }
 614
 615         /**
 616          * Called by serialize. Throw an exception when DB connection is serialized.
 617          * This causes problems on some database engines because the connection is
 618          * not restored on unserialize.
 619          */
 620         public function __sleep() {
 621                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 622         }
 623
 624         /**
 625          * Same as new DatabaseMysql( ... ), kept for backward compatibility
 626          * @deprecated since 1.17
 627          *
 628          * @param $server
 629          * @param $user
 630          * @param $password
 631          * @param $dbName
 632          * @param $flags int
 633          * @return DatabaseMysql
 634          */
 635         static function newFromParams( $server, $user, $password, $dbName, $flags = 0 ) {
 636                 wfDeprecated( __METHOD__, '1.17' );
 637                 return new DatabaseMysql( $server, $user, $password, $dbName, $flags );
 638         }
 639
 640         /**
 641          * Same as new factory( ... ), kept for backward compatibility
 642          * @deprecated since 1.18
 643          * @see Database::factory()
 644          * @return DatabaseBase
 645          */
 646         public final static function newFromType( $dbType, $p = array() ) {
 647                 wfDeprecated( __METHOD__, '1.18' );
 648                 if ( isset( $p['tableprefix'] ) ) {
 649                         $p['tablePrefix'] = $p['tableprefix'];
 650                 }
 651                 return self::factory( $dbType, $p );
 652         }
 653
 654         /**
 655          * Given a DB type, construct the name of the appropriate child class of
 656          * DatabaseBase. This is designed to replace all of the manual stuff like:
 657          *      $class = 'Database' . ucfirst( strtolower( $type ) );
 658          * as well as validate against the canonical list of DB types we have
 659          *
 660          * This factory function is mostly useful for when you need to connect to a
 661          * database other than the MediaWiki default (such as for external auth,
 662          * an extension, et cetera). Do not use this to connect to the MediaWiki
 663          * database. Example uses in core:
 664          * @see LoadBalancer::reallyOpenConnection()
 665          * @see ExternalUser_MediaWiki::initFromCond()
 666          * @see ForeignDBRepo::getMasterDB()
 667          * @see WebInstaller_DBConnect::execute()
 668          *
 669          * @since 1.18
 670          *
 671          * @param $dbType String A possible DB type
 672          * @param $p Array An array of options to pass to the constructor.
 673          *    Valid options are: host, user, password, dbname, flags, tablePrefix
 674          * @return DatabaseBase subclass or null
 675          */
 676         public final static function factory( $dbType, $p = array() ) {
 677                 $canonicalDBTypes = array(
 678                         'mysql', 'postgres', 'sqlite', 'oracle', 'mssql', 'ibm_db2'
 679                 );
 680                 $dbType = strtolower( $dbType );
 681                 $class = 'Database' . ucfirst( $dbType );
 682
 683                 if( in_array( $dbType, $canonicalDBTypes ) ) {
 684                         return new $class(
 685                                 isset( $p['host'] ) ? $p['host'] : false,
 686                                 isset( $p['user'] ) ? $p['user'] : false,
 687                                 isset( $p['password'] ) ? $p['password'] : false,
 688                                 isset( $p['dbname'] ) ? $p['dbname'] : false,
 689                                 isset( $p['flags'] ) ? $p['flags'] : 0,
 690                                 isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global'
 691                         );
 692                 } elseif ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 693                         return new $class( $p );
 694                 } else {
 695                         return null;
 696                 }
 697         }
 698
 699         protected function installErrorHandler() {
 700                 $this->mPHPError = false;
 701                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 702                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 703         }
 704
 705         /**
 706          * @return bool|string
 707          */
 708         protected function restoreErrorHandler() {
 709                 restore_error_handler();
 710                 if ( $this->htmlErrors !== false ) {
 711                         ini_set( 'html_errors', $this->htmlErrors );
 712                 }
 713                 if ( $this->mPHPError ) {
 714                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 715                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 716                         return $error;
 717                 } else {
 718                         return false;
 719                 }
 720         }
 721
 722         /**
 723          * @param $errno
 724          * @param $errstr
 725          */
 726         protected function connectionErrorHandler( $errno,  $errstr ) {
 727                 $this->mPHPError = $errstr;
 728         }
 729
 730         /**
 731          * Closes a database connection.
 732          * if it is open : commits any open transactions
 733          *
 734          * @return Bool operation success. true if already closed.
 735          */
 736         public function close() {
 737                 $this->mOpened = false;
 738                 if ( $this->mConn ) {
 739                         if ( $this->trxLevel() ) {
 740                                 $this->commit( __METHOD__ );
 741                         }
 742                         $ret = $this->closeConnection();
 743                         $this->mConn = false;
 744                         return $ret;
 745                 } else {
 746                         return true;
 747                 }
 748         }
 749
 750         /**
 751          * Closes underlying database connection
 752          * @since 1.20
 753          * @return bool: Whether connection was closed successfully
 754          */
 755         protected abstract function closeConnection();
 756
 757         /**
 758          * @param $error String: fallback error message, used if none is given by DB
 759          */
 760         function reportConnectionError( $error = 'Unknown error' ) {
 761                 $myError = $this->lastError();
 762                 if ( $myError ) {
 763                         $error = $myError;
 764                 }
 765
 766                 # New method
 767                 throw new DBConnectionError( $this, $error );
 768         }
 769
 770         /**
 771          * The DBMS-dependent part of query()
 772          *
 773          * @param  $sql String: SQL query.
 774          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 775          */
 776         protected abstract function doQuery( $sql );
 777
 778         /**
 779          * Determine whether a query writes to the DB.
 780          * Should return true if unsure.
 781          *
 782          * @param $sql string
 783          *
 784          * @return bool
 785          */
 786         function isWriteQuery( $sql ) {
 787                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|\(SELECT)\b/i', $sql );
 788         }
 789
 790         /**
 791          * Run an SQL query and return the result. Normally throws a DBQueryError
 792          * on failure. If errors are ignored, returns false instead.
 793          *
 794          * In new code, the query wrappers select(), insert(), update(), delete(),
 795          * etc. should be used where possible, since they give much better DBMS
 796          * independence and automatically quote or validate user input in a variety
 797          * of contexts. This function is generally only useful for queries which are
 798          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 799          * as CREATE TABLE.
 800          *
 801          * However, the query wrappers themselves should call this function.
 802          *
 803          * @param  $sql        String: SQL query
 804          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 805          *     comment (you can use __METHOD__ or add some extra info)
 806          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 807          *     maybe best to catch the exception instead?
 808          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 809          *     for a successful read query, or false on failure if $tempIgnore set
 810          * @throws DBQueryError Thrown when the database returns an error of any kind
 811          */
 812         public function query( $sql, $fname = '', $tempIgnore = false ) {
 813                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 814                 if ( !Profiler::instance()->isStub() ) {
 815                         # generalizeSQL will probably cut down the query to reasonable
 816                         # logging size most of the time. The substr is really just a sanity check.
 817
 818                         if ( $isMaster ) {
 819                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 820                                 $totalProf = 'DatabaseBase::query-master';
 821                         } else {
 822                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 823                                 $totalProf = 'DatabaseBase::query';
 824                         }
 825
 826                         wfProfileIn( $totalProf );
 827                         wfProfileIn( $queryProf );
 828                 }
 829
 830                 $this->mLastQuery = $sql;
 831                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 832                         # Set a flag indicating that writes have been done
 833                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 834                         $this->mDoneWrites = true;
 835                 }
 836
 837                 # Add a comment for easy SHOW PROCESSLIST interpretation
 838                 global $wgUser;
 839                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 840                         $userName = $wgUser->getName();
 841                         if ( mb_strlen( $userName ) > 15 ) {
 842                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 843                         }
 844                         $userName = str_replace( '/', '', $userName );
 845                 } else {
 846                         $userName = '';
 847                 }
 848                 $commentedSql = preg_replace( '/\s/', " /* $fname $userName */ ", $sql, 1 );
 849
 850                 # If DBO_TRX is set, start a transaction
 851                 if ( ( $this->mFlags & DBO_TRX ) && !$this->trxLevel() &&
 852                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' ) {
 853                         # avoid establishing transactions for SHOW and SET statements too -
 854                         # that would delay transaction initializations to once connection
 855                         # is really used by application
 856                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 857                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 )
 858                                 $this->begin( __METHOD__ . " ($fname)" );
 859                 }
 860
 861                 if ( $this->debug() ) {
 862                         static $cnt = 0;
 863
 864                         $cnt++;
 865                         $sqlx = substr( $commentedSql, 0, 500 );
 866                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 867
 868                         $master = $isMaster ? 'master' : 'slave';
 869                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 870                 }
 871
 872                 if ( istainted( $sql ) & TC_MYSQL ) {
 873                         throw new MWException( 'Tainted query found' );
 874                 }
 875
 876                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 877
 878                 # Do the query and handle errors
 879                 $ret = $this->doQuery( $commentedSql );
 880
 881                 MWDebug::queryTime( $queryId );
 882
 883                 # Try reconnecting if the connection was lost
 884                 if ( false === $ret && $this->wasErrorReissuable() ) {
 885                         # Transaction is gone, like it or not
 886                         $this->mTrxLevel = 0;
 887                         wfDebug( "Connection lost, reconnecting...\n" );
 888
 889                         if ( $this->ping() ) {
 890                                 wfDebug( "Reconnected\n" );
 891                                 $sqlx = substr( $commentedSql, 0, 500 );
 892                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
 893                                 global $wgRequestTime;
 894                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
 895                                 if ( $elapsed < 300 ) {
 896                                         # Not a database error to lose a transaction after a minute or two
 897                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
 898                                 }
 899                                 $ret = $this->doQuery( $commentedSql );
 900                         } else {
 901                                 wfDebug( "Failed\n" );
 902                         }
 903                 }
 904
 905                 if ( false === $ret ) {
 906                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 907                 }
 908
 909                 if ( !Profiler::instance()->isStub() ) {
 910                         wfProfileOut( $queryProf );
 911                         wfProfileOut( $totalProf );
 912                 }
 913
 914                 return $this->resultObject( $ret );
 915         }
 916
 917         /**
 918          * Report a query error. Log the error, and if neither the object ignore
 919          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
 920          *
 921          * @param $error String
 922          * @param $errno Integer
 923          * @param $sql String
 924          * @param $fname String
 925          * @param $tempIgnore Boolean
 926          */
 927         function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
 928                 # Ignore errors during error handling to avoid infinite recursion
 929                 $ignore = $this->ignoreErrors( true );
 930                 ++$this->mErrorCount;
 931
 932                 if ( $ignore || $tempIgnore ) {
 933                         wfDebug( "SQL ERROR (ignored): $error\n" );
 934                         $this->ignoreErrors( $ignore );
 935                 } else {
 936                         $sql1line = str_replace( "\n", "\\n", $sql );
 937                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
 938                         wfDebug( "SQL ERROR: " . $error . "\n" );
 939                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
 940                 }
 941         }
 942
 943         /**
 944          * Intended to be compatible with the PEAR::DB wrapper functions.
 945          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
 946          *
 947          * ? = scalar value, quoted as necessary
 948          * ! = raw SQL bit (a function for instance)
 949          * & = filename; reads the file and inserts as a blob
 950          *     (we don't use this though...)
 951          *
 952          * This function should not be used directly by new code outside of the
 953          * database classes. The query wrapper functions (select() etc.) should be
 954          * used instead.
 955          *
 956          * @param $sql string
 957          * @param $func string
 958          *
 959          * @return array
 960          */
 961         function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
 962                 /* MySQL doesn't support prepared statements (yet), so just
 963                    pack up the query for reference. We'll manually replace
 964                    the bits later. */
 965                 return array( 'query' => $sql, 'func' => $func );
 966         }
 967
 968         /**
 969          * Free a prepared query, generated by prepare().
 970          * @param $prepared
 971          */
 972         function freePrepared( $prepared ) {
 973                 /* No-op by default */
 974         }
 975
 976         /**
 977          * Execute a prepared query with the various arguments
 978          * @param $prepared String: the prepared sql
 979          * @param $args Mixed: Either an array here, or put scalars as varargs
 980          *
 981          * @return ResultWrapper
 982          */
 983         function execute( $prepared, $args = null ) {
 984                 if ( !is_array( $args ) ) {
 985                         # Pull the var args
 986                         $args = func_get_args();
 987                         array_shift( $args );
 988                 }
 989
 990                 $sql = $this->fillPrepared( $prepared['query'], $args );
 991
 992                 return $this->query( $sql, $prepared['func'] );
 993         }
 994
 995         /**
 996          * Prepare & execute an SQL statement, quoting and inserting arguments
 997          * in the appropriate places.
 998          *
 999          * This function should not be used directly by new code outside of the
1000          * database classes. The query wrapper functions (select() etc.) should be
1001          * used instead.
1002          *
1003          * @param $query String
1004          * @param $args ...
1005          *
1006          * @return ResultWrapper
1007          */
1008         function safeQuery( $query, $args = null ) {
1009                 $prepared = $this->prepare( $query, 'DatabaseBase::safeQuery' );
1010
1011                 if ( !is_array( $args ) ) {
1012                         # Pull the var args
1013                         $args = func_get_args();
1014                         array_shift( $args );
1015                 }
1016
1017                 $retval = $this->execute( $prepared, $args );
1018                 $this->freePrepared( $prepared );
1019
1020                 return $retval;
1021         }
1022
1023         /**
1024          * For faking prepared SQL statements on DBs that don't support
1025          * it directly.
1026          * @param $preparedQuery String: a 'preparable' SQL statement
1027          * @param $args Array of arguments to fill it with
1028          * @return string executable SQL
1029          */
1030         function fillPrepared( $preparedQuery, $args ) {
1031                 reset( $args );
1032                 $this->preparedArgs =& $args;
1033
1034                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1035                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1036         }
1037
1038         /**
1039          * preg_callback func for fillPrepared()
1040          * The arguments should be in $this->preparedArgs and must not be touched
1041          * while we're doing this.
1042          *
1043          * @param $matches Array
1044          * @return String
1045          */
1046         function fillPreparedArg( $matches ) {
1047                 switch( $matches[1] ) {
1048                         case '\\?': return '?';
1049                         case '\\!': return '!';
1050                         case '\\&': return '&';
1051                 }
1052
1053                 list( /* $n */ , $arg ) = each( $this->preparedArgs );
1054
1055                 switch( $matches[1] ) {
1056                         case '?': return $this->addQuotes( $arg );
1057                         case '!': return $arg;
1058                         case '&':
1059                                 # return $this->addQuotes( file_get_contents( $arg ) );
1060                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1061                         default:
1062                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1063                 }
1064         }
1065
1066         /**
1067          * Free a result object returned by query() or select(). It's usually not
1068          * necessary to call this, just use unset() or let the variable holding
1069          * the result object go out of scope.
1070          *
1071          * @param $res Mixed: A SQL result
1072          */
1073         function freeResult( $res ) {
1074         }
1075
1076         /**
1077          * Simple UPDATE wrapper.
1078          * Usually throws a DBQueryError on failure.
1079          * If errors are explicitly ignored, returns success
1080          *
1081          * This function exists for historical reasons, DatabaseBase::update() has a more standard
1082          * calling convention and feature set
1083          *
1084          * @param $table string
1085          * @param $var
1086          * @param $value
1087          * @param $cond
1088          * @param $fname string
1089          *
1090          * @return bool
1091          */
1092         function set( $table, $var, $value, $cond, $fname = 'DatabaseBase::set' ) {
1093                 $table = $this->tableName( $table );
1094                 $sql = "UPDATE $table SET $var = '" .
1095                   $this->strencode( $value ) . "' WHERE ($cond)";
1096
1097                 return (bool)$this->query( $sql, $fname );
1098         }
1099
1100         /**
1101          * A SELECT wrapper which returns a single field from a single result row.
1102          *
1103          * Usually throws a DBQueryError on failure. If errors are explicitly
1104          * ignored, returns false on failure.
1105          *
1106          * If no result rows are returned from the query, false is returned.
1107          *
1108          * @param $table string|array Table name. See DatabaseBase::select() for details.
1109          * @param $var string The field name to select. This must be a valid SQL
1110          *   fragment: do not use unvalidated user input.
1111          * @param $cond string|array The condition array. See DatabaseBase::select() for details.
1112          * @param $fname string The function name of the caller.
1113          * @param $options string|array The query options. See DatabaseBase::select() for details.
1114          *
1115          * @return bool|mixed The value from the field, or false on failure.
1116          */
1117         function selectField( $table, $var, $cond = '', $fname = 'DatabaseBase::selectField',
1118                 $options = array() )
1119         {
1120                 if ( !is_array( $options ) ) {
1121                         $options = array( $options );
1122                 }
1123
1124                 $options['LIMIT'] = 1;
1125
1126                 $res = $this->select( $table, $var, $cond, $fname, $options );
1127
1128                 if ( $res === false || !$this->numRows( $res ) ) {
1129                         return false;
1130                 }
1131
1132                 $row = $this->fetchRow( $res );
1133
1134                 if ( $row !== false ) {
1135                         return reset( $row );
1136                 } else {
1137                         return false;
1138                 }
1139         }
1140
1141         /**
1142          * Returns an optional USE INDEX clause to go after the table, and a
1143          * string to go at the end of the query.
1144          *
1145          * @param $options Array: associative array of options to be turned into
1146          *              an SQL query, valid keys are listed in the function.
1147          * @return Array
1148          * @see DatabaseBase::select()
1149          */
1150         function makeSelectOptions( $options ) {
1151                 $preLimitTail = $postLimitTail = '';
1152                 $startOpts = '';
1153
1154                 $noKeyOptions = array();
1155
1156                 foreach ( $options as $key => $option ) {
1157                         if ( is_numeric( $key ) ) {
1158                                 $noKeyOptions[$option] = true;
1159                         }
1160                 }
1161
1162                 if ( isset( $options['GROUP BY'] ) ) {
1163                         $gb = is_array( $options['GROUP BY'] )
1164                                 ? implode( ',', $options['GROUP BY'] )
1165                                 : $options['GROUP BY'];
1166                         $preLimitTail .= " GROUP BY {$gb}";
1167                 }
1168
1169                 if ( isset( $options['HAVING'] ) ) {
1170                         $preLimitTail .= " HAVING {$options['HAVING']}";
1171                 }
1172
1173                 if ( isset( $options['ORDER BY'] ) ) {
1174                         $ob = is_array( $options['ORDER BY'] )
1175                                 ? implode( ',', $options['ORDER BY'] )
1176                                 : $options['ORDER BY'];
1177                         $preLimitTail .= " ORDER BY {$ob}";
1178                 }
1179
1180                 // if (isset($options['LIMIT'])) {
1181                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1182                 //              isset($options['OFFSET']) ? $options['OFFSET']
1183                 //              : false);
1184                 // }
1185
1186                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1187                         $postLimitTail .= ' FOR UPDATE';
1188                 }
1189
1190                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1191                         $postLimitTail .= ' LOCK IN SHARE MODE';
1192                 }
1193
1194                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1195                         $startOpts .= 'DISTINCT';
1196                 }
1197
1198                 # Various MySQL extensions
1199                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1200                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1201                 }
1202
1203                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1204                         $startOpts .= ' HIGH_PRIORITY';
1205                 }
1206
1207                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1208                         $startOpts .= ' SQL_BIG_RESULT';
1209                 }
1210
1211                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1212                         $startOpts .= ' SQL_BUFFER_RESULT';
1213                 }
1214
1215                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1216                         $startOpts .= ' SQL_SMALL_RESULT';
1217                 }
1218
1219                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1220                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1221                 }
1222
1223                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1224                         $startOpts .= ' SQL_CACHE';
1225                 }
1226
1227                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1228                         $startOpts .= ' SQL_NO_CACHE';
1229                 }
1230
1231                 if ( isset( $options['USE INDEX'] ) && ! is_array( $options['USE INDEX'] ) ) {
1232                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1233                 } else {
1234                         $useIndex = '';
1235                 }
1236
1237                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1238         }
1239
1240         /**
1241          * Execute a SELECT query constructed using the various parameters provided.
1242          * See below for full details of the parameters.
1243          *
1244          * @param $table String|Array Table name
1245          * @param $vars String|Array Field names
1246          * @param $conds String|Array Conditions
1247          * @param $fname String Caller function name
1248          * @param $options Array Query options
1249          * @param $join_conds Array Join conditions
1250          *
1251          * @param $table string|array
1252          *
1253          * May be either an array of table names, or a single string holding a table
1254          * name. If an array is given, table aliases can be specified, for example:
1255          *
1256          *    array( 'a' => 'user' )
1257          *
1258          * This includes the user table in the query, with the alias "a" available
1259          * for use in field names (e.g. a.user_name).
1260          *
1261          * All of the table names given here are automatically run through
1262          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1263          * added, and various other table name mappings to be performed.
1264          *
1265          *
1266          * @param $vars string|array
1267          *
1268          * May be either a field name or an array of field names. The field names
1269          * here are complete fragments of SQL, for direct inclusion into the SELECT
1270          * query. Expressions and aliases may be specified as in SQL, for example:
1271          *
1272          *   array( 'MAX(rev_id) AS maxrev' )
1273          *
1274          * If an expression is given, care must be taken to ensure that it is
1275          * DBMS-independent.
1276          *
1277          *
1278          * @param $conds string|array
1279          *
1280          * May be either a string containing a single condition, or an array of
1281          * conditions. If an array is given, the conditions constructed from each
1282          * element are combined with AND.
1283          *
1284          * Array elements may take one of two forms:
1285          *
1286          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1287          *   - Elements with a string key are interpreted as equality conditions,
1288          *     where the key is the field name.
1289          *     - If the value of such an array element is a scalar (such as a
1290          *       string), it will be treated as data and thus quoted appropriately.
1291          *       If it is null, an IS NULL clause will be added.
1292          *     - If the value is an array, an IN(...) clause will be constructed,
1293          *       such that the field name may match any of the elements in the
1294          *       array. The elements of the array will be quoted.
1295          *
1296          * Note that expressions are often DBMS-dependent in their syntax.
1297          * DBMS-independent wrappers are provided for constructing several types of
1298          * expression commonly used in condition queries. See:
1299          *    - DatabaseBase::buildLike()
1300          *    - DatabaseBase::conditional()
1301          *
1302          *
1303          * @param $options string|array
1304          *
1305          * Optional: Array of query options. Boolean options are specified by
1306          * including them in the array as a string value with a numeric key, for
1307          * example:
1308          *
1309          *    array( 'FOR UPDATE' )
1310          *
1311          * The supported options are:
1312          *
1313          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1314          *     with LIMIT can theoretically be used for paging through a result set,
1315          *     but this is discouraged in MediaWiki for performance reasons.
1316          *
1317          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1318          *     and then the first rows are taken until the limit is reached. LIMIT
1319          *     is applied to a result set after OFFSET.
1320          *
1321          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1322          *     changed until the next COMMIT.
1323          *
1324          *   - DISTINCT: Boolean: return only unique result rows.
1325          *
1326          *   - GROUP BY: May be either an SQL fragment string naming a field or
1327          *     expression to group by, or an array of such SQL fragments.
1328          *
1329          *   - HAVING: A string containing a HAVING clause.
1330          *
1331          *   - ORDER BY: May be either an SQL fragment giving a field name or
1332          *     expression to order by, or an array of such SQL fragments.
1333          *
1334          *   - USE INDEX: This may be either a string giving the index name to use
1335          *     for the query, or an array. If it is an associative array, each key
1336          *     gives the table name (or alias), each value gives the index name to
1337          *     use for that table. All strings are SQL fragments and so should be
1338          *     validated by the caller.
1339          *
1340          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1341          *     instead of SELECT.
1342          *
1343          * And also the following boolean MySQL extensions, see the MySQL manual
1344          * for documentation:
1345          *
1346          *    - LOCK IN SHARE MODE
1347          *    - STRAIGHT_JOIN
1348          *    - HIGH_PRIORITY
1349          *    - SQL_BIG_RESULT
1350          *    - SQL_BUFFER_RESULT
1351          *    - SQL_SMALL_RESULT
1352          *    - SQL_CALC_FOUND_ROWS
1353          *    - SQL_CACHE
1354          *    - SQL_NO_CACHE
1355          *
1356          *
1357          * @param $join_conds string|array
1358          *
1359          * Optional associative array of table-specific join conditions. In the
1360          * most common case, this is unnecessary, since the join condition can be
1361          * in $conds. However, it is useful for doing a LEFT JOIN.
1362          *
1363          * The key of the array contains the table name or alias. The value is an
1364          * array with two elements, numbered 0 and 1. The first gives the type of
1365          * join, the second is an SQL fragment giving the join condition for that
1366          * table. For example:
1367          *
1368          *    array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
1369          *
1370          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1371          *   with no rows in it will be returned. If there was a query error, a
1372          *   DBQueryError exception will be thrown, except if the "ignore errors"
1373          *   option was set, in which case false will be returned.
1374          */
1375         function select( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1376                 $options = array(), $join_conds = array() ) {
1377                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1378
1379                 return $this->query( $sql, $fname );
1380         }
1381
1382         /**
1383          * The equivalent of DatabaseBase::select() except that the constructed SQL
1384          * is returned, instead of being immediately executed.
1385          *
1386          * @param $table string|array Table name
1387          * @param $vars string|array Field names
1388          * @param $conds string|array Conditions
1389          * @param $fname string Caller function name
1390          * @param $options string|array Query options
1391          * @param $join_conds string|array Join conditions
1392          *
1393          * @return string SQL query string.
1394          * @see DatabaseBase::select()
1395          */
1396         function selectSQLText( $table, $vars, $conds = '', $fname = 'DatabaseBase::select', $options = array(), $join_conds = array() ) {
1397                 if ( is_array( $vars ) ) {
1398                         $vars = implode( ',', $vars );
1399                 }
1400
1401                 $options = (array)$options;
1402
1403                 if ( is_array( $table ) ) {
1404                         $useIndex = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1405                                 ? $options['USE INDEX']
1406                                 : array();
1407                         if ( count( $join_conds ) || count( $useIndex ) ) {
1408                                 $from = ' FROM ' .
1409                                         $this->tableNamesWithUseIndexOrJOIN( $table, $useIndex, $join_conds );
1410                         } else {
1411                                 $from = ' FROM ' . implode( ',', $this->tableNamesWithAlias( $table ) );
1412                         }
1413                 } elseif ( $table != '' ) {
1414                         if ( $table[0] == ' ' ) {
1415                                 $from = ' FROM ' . $table;
1416                         } else {
1417                                 $from = ' FROM ' . $this->tableName( $table );
1418                         }
1419                 } else {
1420                         $from = '';
1421                 }
1422
1423                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) = $this->makeSelectOptions( $options );
1424
1425                 if ( !empty( $conds ) ) {
1426                         if ( is_array( $conds ) ) {
1427                                 $conds = $this->makeList( $conds, LIST_AND );
1428                         }
1429                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1430                 } else {
1431                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1432                 }
1433
1434                 if ( isset( $options['LIMIT'] ) ) {
1435                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1436                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1437                 }
1438                 $sql = "$sql $postLimitTail";
1439
1440                 if ( isset( $options['EXPLAIN'] ) ) {
1441                         $sql = 'EXPLAIN ' . $sql;
1442                 }
1443
1444                 return $sql;
1445         }
1446
1447         /**
1448          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1449          * that a single row object is returned. If the query returns no rows,
1450          * false is returned.
1451          *
1452          * @param $table string|array Table name
1453          * @param $vars string|array Field names
1454          * @param $conds array Conditions
1455          * @param $fname string Caller function name
1456          * @param $options string|array Query options
1457          * @param $join_conds array|string Join conditions
1458          *
1459          * @return object|bool
1460          */
1461         function selectRow( $table, $vars, $conds, $fname = 'DatabaseBase::selectRow',
1462                 $options = array(), $join_conds = array() )
1463         {
1464                 $options['LIMIT'] = 1;
1465                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1466
1467                 if ( $res === false ) {
1468                         return false;
1469                 }
1470
1471                 if ( !$this->numRows( $res ) ) {
1472                         return false;
1473                 }
1474
1475                 $obj = $this->fetchObject( $res );
1476
1477                 return $obj;
1478         }
1479
1480         /**
1481          * Estimate rows in dataset.
1482          *
1483          * MySQL allows you to estimate the number of rows that would be returned
1484          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1485          * index cardinality statistics, and is notoriously inaccurate, especially
1486          * when large numbers of rows have recently been added or deleted.
1487          *
1488          * For DBMSs that don't support fast result size estimation, this function
1489          * will actually perform the SELECT COUNT(*).
1490          *
1491          * Takes the same arguments as DatabaseBase::select().
1492          *
1493          * @param $table String: table name
1494          * @param Array|string $vars : unused
1495          * @param Array|string $conds : filters on the table
1496          * @param $fname String: function name for profiling
1497          * @param $options Array: options for select
1498          * @return Integer: row count
1499          */
1500         public function estimateRowCount( $table, $vars = '*', $conds = '',
1501                 $fname = 'DatabaseBase::estimateRowCount', $options = array() )
1502         {
1503                 $rows = 0;
1504                 $res = $this->select ( $table, 'COUNT(*) AS rowcount', $conds, $fname, $options );
1505
1506                 if ( $res ) {
1507                         $row = $this->fetchRow( $res );
1508                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1509                 }
1510
1511                 return $rows;
1512         }
1513
1514         /**
1515          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1516          * It's only slightly flawed. Don't use for anything important.
1517          *
1518          * @param $sql String A SQL Query
1519          *
1520          * @return string
1521          */
1522         static function generalizeSQL( $sql ) {
1523                 # This does the same as the regexp below would do, but in such a way
1524                 # as to avoid crashing php on some large strings.
1525                 # $sql = preg_replace ( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql);
1526
1527                 $sql = str_replace ( "\\\\", '', $sql );
1528                 $sql = str_replace ( "\\'", '', $sql );
1529                 $sql = str_replace ( "\\\"", '', $sql );
1530                 $sql = preg_replace ( "/'.*'/s", "'X'", $sql );
1531                 $sql = preg_replace ( '/".*"/s', "'X'", $sql );
1532
1533                 # All newlines, tabs, etc replaced by single space
1534                 $sql = preg_replace ( '/\s+/', ' ', $sql );
1535
1536                 # All numbers => N
1537                 $sql = preg_replace ( '/-?[0-9]+/s', 'N', $sql );
1538
1539                 return $sql;
1540         }
1541
1542         /**
1543          * Determines whether a field exists in a table
1544          *
1545          * @param $table String: table name
1546          * @param $field String: filed to check on that table
1547          * @param $fname String: calling function name (optional)
1548          * @return Boolean: whether $table has filed $field
1549          */
1550         function fieldExists( $table, $field, $fname = 'DatabaseBase::fieldExists' ) {
1551                 $info = $this->fieldInfo( $table, $field );
1552
1553                 return (bool)$info;
1554         }
1555
1556         /**
1557          * Determines whether an index exists
1558          * Usually throws a DBQueryError on failure
1559          * If errors are explicitly ignored, returns NULL on failure
1560          *
1561          * @param $table
1562          * @param $index
1563          * @param $fname string
1564          *
1565          * @return bool|null
1566          */
1567         function indexExists( $table, $index, $fname = 'DatabaseBase::indexExists' ) {
1568                 $info = $this->indexInfo( $table, $index, $fname );
1569                 if ( is_null( $info ) ) {
1570                         return null;
1571                 } else {
1572                         return $info !== false;
1573                 }
1574         }
1575
1576         /**
1577          * Query whether a given table exists
1578          *
1579          * @param $table string
1580          * @param $fname string
1581          *
1582          * @return bool
1583          */
1584         function tableExists( $table, $fname = __METHOD__ ) {
1585                 $table = $this->tableName( $table );
1586                 $old = $this->ignoreErrors( true );
1587                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1588                 $this->ignoreErrors( $old );
1589
1590                 return (bool)$res;
1591         }
1592
1593         /**
1594          * mysql_field_type() wrapper
1595          * @param $res
1596          * @param $index
1597          * @return string
1598          */
1599         function fieldType( $res, $index ) {
1600                 if ( $res instanceof ResultWrapper ) {
1601                         $res = $res->result;
1602                 }
1603
1604                 return mysql_field_type( $res, $index );
1605         }
1606
1607         /**
1608          * Determines if a given index is unique
1609          *
1610          * @param $table string
1611          * @param $index string
1612          *
1613          * @return bool
1614          */
1615         function indexUnique( $table, $index ) {
1616                 $indexInfo = $this->indexInfo( $table, $index );
1617
1618                 if ( !$indexInfo ) {
1619                         return null;
1620                 }
1621
1622                 return !$indexInfo[0]->Non_unique;
1623         }
1624
1625         /**
1626          * Helper for DatabaseBase::insert().
1627          *
1628          * @param $options array
1629          * @return string
1630          */
1631         function makeInsertOptions( $options ) {
1632                 return implode( ' ', $options );
1633         }
1634
1635         /**
1636          * INSERT wrapper, inserts an array into a table.
1637          *
1638          * $a may be either:
1639          *
1640          *   - A single associative array. The array keys are the field names, and
1641          *     the values are the values to insert. The values are treated as data
1642          *     and will be quoted appropriately. If NULL is inserted, this will be
1643          *     converted to a database NULL.
1644          *   - An array with numeric keys, holding a list of associative arrays.
1645          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1646          *     each subarray must be identical to each other, and in the same order.
1647          *
1648          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1649          * returns success.
1650          *
1651          * $options is an array of options, with boolean options encoded as values
1652          * with numeric keys, in the same style as $options in
1653          * DatabaseBase::select(). Supported options are:
1654          *
1655          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1656          *     any rows which cause duplicate key errors are not inserted. It's
1657          *     possible to determine how many rows were successfully inserted using
1658          *     DatabaseBase::affectedRows().
1659          *
1660          * @param $table   String Table name. This will be passed through
1661          *                 DatabaseBase::tableName().
1662          * @param $a       Array of rows to insert
1663          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1664          * @param $options Array of options
1665          *
1666          * @return bool
1667          */
1668         function insert( $table, $a, $fname = 'DatabaseBase::insert', $options = array() ) {
1669                 # No rows to insert, easy just return now
1670                 if ( !count( $a ) ) {
1671                         return true;
1672                 }
1673
1674                 $table = $this->tableName( $table );
1675
1676                 if ( !is_array( $options ) ) {
1677                         $options = array( $options );
1678                 }
1679
1680                 $options = $this->makeInsertOptions( $options );
1681
1682                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1683                         $multi = true;
1684                         $keys = array_keys( $a[0] );
1685                 } else {
1686                         $multi = false;
1687                         $keys = array_keys( $a );
1688                 }
1689
1690                 $sql = 'INSERT ' . $options .
1691                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1692
1693                 if ( $multi ) {
1694                         $first = true;
1695                         foreach ( $a as $row ) {
1696                                 if ( $first ) {
1697                                         $first = false;
1698                                 } else {
1699                                         $sql .= ',';
1700                                 }
1701                                 $sql .= '(' . $this->makeList( $row ) . ')';
1702                         }
1703                 } else {
1704                         $sql .= '(' . $this->makeList( $a ) . ')';
1705                 }
1706
1707                 return (bool)$this->query( $sql, $fname );
1708         }
1709
1710         /**
1711          * Make UPDATE options for the DatabaseBase::update function
1712          *
1713          * @param $options Array: The options passed to DatabaseBase::update
1714          * @return string
1715          */
1716         function makeUpdateOptions( $options ) {
1717                 if ( !is_array( $options ) ) {
1718                         $options = array( $options );
1719                 }
1720
1721                 $opts = array();
1722
1723                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1724                         $opts[] = $this->lowPriorityOption();
1725                 }
1726
1727                 if ( in_array( 'IGNORE', $options ) ) {
1728                         $opts[] = 'IGNORE';
1729                 }
1730
1731                 return implode( ' ', $opts );
1732         }
1733
1734         /**
1735          * UPDATE wrapper. Takes a condition array and a SET array.
1736          *
1737          * @param $table  String name of the table to UPDATE. This will be passed through
1738          *                DatabaseBase::tableName().
1739          *
1740          * @param $values Array:  An array of values to SET. For each array element,
1741          *                the key gives the field name, and the value gives the data
1742          *                to set that field to. The data will be quoted by
1743          *                DatabaseBase::addQuotes().
1744          *
1745          * @param $conds  Array:  An array of conditions (WHERE). See
1746          *                DatabaseBase::select() for the details of the format of
1747          *                condition arrays. Use '*' to update all rows.
1748          *
1749          * @param $fname  String: The function name of the caller (from __METHOD__),
1750          *                for logging and profiling.
1751          *
1752          * @param $options Array: An array of UPDATE options, can be:
1753          *                   - IGNORE: Ignore unique key conflicts
1754          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1755          * @return Boolean
1756          */
1757         function update( $table, $values, $conds, $fname = 'DatabaseBase::update', $options = array() ) {
1758                 $table = $this->tableName( $table );
1759                 $opts = $this->makeUpdateOptions( $options );
1760                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1761
1762                 if ( $conds !== array() && $conds !== '*' ) {
1763                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1764                 }
1765
1766                 return $this->query( $sql, $fname );
1767         }
1768
1769         /**
1770          * Makes an encoded list of strings from an array
1771          * @param $a Array containing the data
1772          * @param $mode int Constant
1773          *      - LIST_COMMA:          comma separated, no field names
1774          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1775          *        the documentation for $conds in DatabaseBase::select().
1776          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1777          *      - LIST_SET:            comma separated with field names, like a SET clause
1778          *      - LIST_NAMES:          comma separated field names
1779          *
1780          * @return string
1781          */
1782         function makeList( $a, $mode = LIST_COMMA ) {
1783                 if ( !is_array( $a ) ) {
1784                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1785                 }
1786
1787                 $first = true;
1788                 $list = '';
1789
1790                 foreach ( $a as $field => $value ) {
1791                         if ( !$first ) {
1792                                 if ( $mode == LIST_AND ) {
1793                                         $list .= ' AND ';
1794                                 } elseif ( $mode == LIST_OR ) {
1795                                         $list .= ' OR ';
1796                                 } else {
1797                                         $list .= ',';
1798                                 }
1799                         } else {
1800                                 $first = false;
1801                         }
1802
1803                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1804                                 $list .= "($value)";
1805                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1806                                 $list .= "$value";
1807                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1808                                 if ( count( $value ) == 0 ) {
1809                                         throw new MWException( __METHOD__ . ': empty input' );
1810                                 } elseif ( count( $value ) == 1 ) {
1811                                         // Special-case single values, as IN isn't terribly efficient
1812                                         // Don't necessarily assume the single key is 0; we don't
1813                                         // enforce linear numeric ordering on other arrays here.
1814                                         $value = array_values( $value );
1815                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1816                                 } else {
1817                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1818                                 }
1819                         } elseif ( $value === null ) {
1820                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1821                                         $list .= "$field IS ";
1822                                 } elseif ( $mode == LIST_SET ) {
1823                                         $list .= "$field = ";
1824                                 }
1825                                 $list .= 'NULL';
1826                         } else {
1827                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1828                                         $list .= "$field = ";
1829                                 }
1830                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1831                         }
1832                 }
1833
1834                 return $list;
1835         }
1836
1837         /**
1838          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1839          * The keys on each level may be either integers or strings.
1840          *
1841          * @param $data Array: organized as 2-d
1842          *              array(baseKeyVal => array(subKeyVal => <ignored>, ...), ...)
1843          * @param $baseKey String: field name to match the base-level keys to (eg 'pl_namespace')
1844          * @param $subKey String: field name to match the sub-level keys to (eg 'pl_title')
1845          * @return Mixed: string SQL fragment, or false if no items in array.
1846          */
1847         function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1848                 $conds = array();
1849
1850                 foreach ( $data as $base => $sub ) {
1851                         if ( count( $sub ) ) {
1852                                 $conds[] = $this->makeList(
1853                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1854                                         LIST_AND );
1855                         }
1856                 }
1857
1858                 if ( $conds ) {
1859                         return $this->makeList( $conds, LIST_OR );
1860                 } else {
1861                         // Nothing to search for...
1862                         return false;
1863                 }
1864         }
1865
1866         /**
1867          * Bitwise operations
1868          */
1869
1870         /**
1871          * @param $field
1872          * @return string
1873          */
1874         function bitNot( $field ) {
1875                 return "(~$field)";
1876         }
1877
1878         /**
1879          * @param $fieldLeft
1880          * @param $fieldRight
1881          * @return string
1882          */
1883         function bitAnd( $fieldLeft, $fieldRight ) {
1884                 return "($fieldLeft & $fieldRight)";
1885         }
1886
1887         /**
1888          * @param  $fieldLeft
1889          * @param  $fieldRight
1890          * @return string
1891          */
1892         function bitOr( $fieldLeft, $fieldRight ) {
1893                 return "($fieldLeft | $fieldRight)";
1894         }
1895
1896         /**
1897          * Change the current database
1898          *
1899          * @todo Explain what exactly will fail if this is not overridden.
1900          *
1901          * @param $db
1902          *
1903          * @return bool Success or failure
1904          */
1905         function selectDB( $db ) {
1906                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
1907                 # if your database engine supports a concept similar to MySQL's
1908                 # databases you may as well.
1909                 $this->mDBname = $db;
1910                 return true;
1911         }
1912
1913         /**
1914          * Get the current DB name
1915          */
1916         function getDBname() {
1917                 return $this->mDBname;
1918         }
1919
1920         /**
1921          * Get the server hostname or IP address
1922          */
1923         function getServer() {
1924                 return $this->mServer;
1925         }
1926
1927         /**
1928          * Format a table name ready for use in constructing an SQL query
1929          *
1930          * This does two important things: it quotes the table names to clean them up,
1931          * and it adds a table prefix if only given a table name with no quotes.
1932          *
1933          * All functions of this object which require a table name call this function
1934          * themselves. Pass the canonical name to such functions. This is only needed
1935          * when calling query() directly.
1936          *
1937          * @param $name String: database table name
1938          * @param $format String One of:
1939          *   quoted - Automatically pass the table name through addIdentifierQuotes()
1940          *            so that it can be used in a query.
1941          *   raw - Do not add identifier quotes to the table name
1942          * @return String: full database name
1943          */
1944         function tableName( $name, $format = 'quoted' ) {
1945                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
1946                 # Skip the entire process when we have a string quoted on both ends.
1947                 # Note that we check the end so that we will still quote any use of
1948                 # use of `database`.table. But won't break things if someone wants
1949                 # to query a database table with a dot in the name.
1950                 if ( $this->isQuotedIdentifier( $name ) ) {
1951                         return $name;
1952                 }
1953
1954                 # Lets test for any bits of text that should never show up in a table
1955                 # name. Basically anything like JOIN or ON which are actually part of
1956                 # SQL queries, but may end up inside of the table value to combine
1957                 # sql. Such as how the API is doing.
1958                 # Note that we use a whitespace test rather than a \b test to avoid
1959                 # any remote case where a word like on may be inside of a table name
1960                 # surrounded by symbols which may be considered word breaks.
1961                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1962                         return $name;
1963                 }
1964
1965                 # Split database and table into proper variables.
1966                 # We reverse the explode so that database.table and table both output
1967                 # the correct table.
1968                 $dbDetails = array_reverse( explode( '.', $name, 2 ) );
1969                 if ( isset( $dbDetails[1] ) ) {
1970                         list( $table, $database ) = $dbDetails;
1971                 } else {
1972                         list( $table ) = $dbDetails;
1973                 }
1974                 $prefix = $this->mTablePrefix; # Default prefix
1975
1976                 # A database name has been specified in input. We don't want any
1977                 # prefixes added.
1978                 if ( isset( $database ) ) {
1979                         $prefix = '';
1980                 }
1981
1982                 # Note that we use the long format because php will complain in in_array if
1983                 # the input is not an array, and will complain in is_array if it is not set.
1984                 if ( !isset( $database ) # Don't use shared database if pre selected.
1985                  && isset( $wgSharedDB ) # We have a shared database
1986                  && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
1987                  && isset( $wgSharedTables )
1988                  && is_array( $wgSharedTables )
1989                  && in_array( $table, $wgSharedTables ) ) { # A shared table is selected
1990                         $database = $wgSharedDB;
1991                         $prefix   = isset( $wgSharedPrefix ) ? $wgSharedPrefix : $prefix;
1992                 }
1993
1994                 # Quote the $database and $table and apply the prefix if not quoted.
1995                 if ( isset( $database ) ) {
1996                         $database = ( $format == 'quoted' || $this->isQuotedIdentifier( $database ) ? $database : $this->addIdentifierQuotes( $database ) );
1997                 }
1998
1999                 $table = "{$prefix}{$table}";
2000                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $table ) ) {
2001                         $table = $this->addIdentifierQuotes( "{$table}" );
2002                 }
2003
2004                 # Merge our database and table into our final table name.
2005                 $tableName = ( isset( $database ) ? "{$database}.{$table}" : "{$table}" );
2006
2007                 return $tableName;
2008         }
2009
2010         /**
2011          * Fetch a number of table names into an array
2012          * This is handy when you need to construct SQL for joins
2013          *
2014          * Example:
2015          * extract($dbr->tableNames('user','watchlist'));
2016          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2017          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2018          *
2019          * @return array
2020          */
2021         public function tableNames() {
2022                 $inArray = func_get_args();
2023                 $retVal = array();
2024
2025                 foreach ( $inArray as $name ) {
2026                         $retVal[$name] = $this->tableName( $name );
2027                 }
2028
2029                 return $retVal;
2030         }
2031
2032         /**
2033          * Fetch a number of table names into an zero-indexed numerical array
2034          * This is handy when you need to construct SQL for joins
2035          *
2036          * Example:
2037          * list( $user, $watchlist ) = $dbr->tableNamesN('user','watchlist');
2038          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2039          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2040          *
2041          * @return array
2042          */
2043         public function tableNamesN() {
2044                 $inArray = func_get_args();
2045                 $retVal = array();
2046
2047                 foreach ( $inArray as $name ) {
2048                         $retVal[] = $this->tableName( $name );
2049                 }
2050
2051                 return $retVal;
2052         }
2053
2054         /**
2055          * Get an aliased table name
2056          * e.g. tableName AS newTableName
2057          *
2058          * @param $name string Table name, see tableName()
2059          * @param $alias string|bool Alias (optional)
2060          * @return string SQL name for aliased table. Will not alias a table to its own name
2061          */
2062         public function tableNameWithAlias( $name, $alias = false ) {
2063                 if ( !$alias || $alias == $name ) {
2064                         return $this->tableName( $name );
2065                 } else {
2066                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2067                 }
2068         }
2069
2070         /**
2071          * Gets an array of aliased table names
2072          *
2073          * @param $tables array( [alias] => table )
2074          * @return array of strings, see tableNameWithAlias()
2075          */
2076         public function tableNamesWithAlias( $tables ) {
2077                 $retval = array();
2078                 foreach ( $tables as $alias => $table ) {
2079                         if ( is_numeric( $alias ) ) {
2080                                 $alias = $table;
2081                         }
2082                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2083                 }
2084                 return $retval;
2085         }
2086
2087         /**
2088          * Get the aliased table name clause for a FROM clause
2089          * which might have a JOIN and/or USE INDEX clause
2090          *
2091          * @param $tables array ( [alias] => table )
2092          * @param $use_index array Same as for select()
2093          * @param $join_conds array Same as for select()
2094          * @return string
2095          */
2096         protected function tableNamesWithUseIndexOrJOIN(
2097                 $tables, $use_index = array(), $join_conds = array()
2098         ) {
2099                 $ret = array();
2100                 $retJOIN = array();
2101                 $use_index = (array)$use_index;
2102                 $join_conds = (array)$join_conds;
2103
2104                 foreach ( $tables as $alias => $table ) {
2105                         if ( !is_string( $alias ) ) {
2106                                 // No alias? Set it equal to the table name
2107                                 $alias = $table;
2108                         }
2109                         // Is there a JOIN clause for this table?
2110                         if ( isset( $join_conds[$alias] ) ) {
2111                                 list( $joinType, $conds ) = $join_conds[$alias];
2112                                 $tableClause = $joinType;
2113                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2114                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2115                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2116                                         if ( $use != '' ) {
2117                                                 $tableClause .= ' ' . $use;
2118                                         }
2119                                 }
2120                                 $on = $this->makeList( (array)$conds, LIST_AND );
2121                                 if ( $on != '' ) {
2122                                         $tableClause .= ' ON (' . $on . ')';
2123                                 }
2124
2125                                 $retJOIN[] = $tableClause;
2126                         // Is there an INDEX clause for this table?
2127                         } elseif ( isset( $use_index[$alias] ) ) {
2128                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2129                                 $tableClause .= ' ' . $this->useIndexClause(
2130                                         implode( ',', (array)$use_index[$alias] ) );
2131
2132                                 $ret[] = $tableClause;
2133                         } else {
2134                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2135
2136                                 $ret[] = $tableClause;
2137                         }
2138                 }
2139
2140                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2141                 $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2142                 $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2143
2144                 // Compile our final table clause
2145                 return implode( ' ', array( $straightJoins, $otherJoins ) );
2146         }
2147
2148         /**
2149          * Get the name of an index in a given table
2150          *
2151          * @param $index
2152          *
2153          * @return string
2154          */
2155         function indexName( $index ) {
2156                 // Backwards-compatibility hack
2157                 $renamed = array(
2158                         'ar_usertext_timestamp' => 'usertext_timestamp',
2159                         'un_user_id'            => 'user_id',
2160                         'un_user_ip'            => 'user_ip',
2161                 );
2162
2163                 if ( isset( $renamed[$index] ) ) {
2164                         return $renamed[$index];
2165                 } else {
2166                         return $index;
2167                 }
2168         }
2169
2170         /**
2171          * If it's a string, adds quotes and backslashes
2172          * Otherwise returns as-is
2173          *
2174          * @param $s string
2175          *
2176          * @return string
2177          */
2178         function addQuotes( $s ) {
2179                 if ( $s === null ) {
2180                         return 'NULL';
2181                 } else {
2182                         # This will also quote numeric values. This should be harmless,
2183                         # and protects against weird problems that occur when they really
2184                         # _are_ strings such as article titles and string->number->string
2185                         # conversion is not 1:1.
2186                         return "'" . $this->strencode( $s ) . "'";
2187                 }
2188         }
2189
2190         /**
2191          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2192          * MySQL uses `backticks` while basically everything else uses double quotes.
2193          * Since MySQL is the odd one out here the double quotes are our generic
2194          * and we implement backticks in DatabaseMysql.
2195          *
2196          * @param $s string
2197          *
2198          * @return string
2199          */
2200         public function addIdentifierQuotes( $s ) {
2201                 return '"' . str_replace( '"', '""', $s ) . '"';
2202         }
2203
2204         /**
2205          * Returns if the given identifier looks quoted or not according to
2206          * the database convention for quoting identifiers .
2207          *
2208          * @param $name string
2209          *
2210          * @return boolean
2211          */
2212         public function isQuotedIdentifier( $name ) {
2213                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2214         }
2215
2216         /**
2217          * Backwards compatibility, identifier quoting originated in DatabasePostgres
2218          * which used quote_ident which does not follow our naming conventions
2219          * was renamed to addIdentifierQuotes.
2220          * @deprecated since 1.18 use addIdentifierQuotes
2221          *
2222          * @param $s string
2223          *
2224          * @return string
2225          */
2226         function quote_ident( $s ) {
2227                 wfDeprecated( __METHOD__, '1.18' );
2228                 return $this->addIdentifierQuotes( $s );
2229         }
2230
2231         /**
2232          * Escape string for safe LIKE usage.
2233          * WARNING: you should almost never use this function directly,
2234          * instead use buildLike() that escapes everything automatically
2235          * @deprecated since 1.17, warnings in 1.17, removed in ???
2236          *
2237          * @param $s string
2238          *
2239          * @return string
2240          */
2241         public function escapeLike( $s ) {
2242                 wfDeprecated( __METHOD__, '1.17' );
2243                 return $this->escapeLikeInternal( $s );
2244         }
2245
2246         /**
2247          * @param $s string
2248          * @return string
2249          */
2250         protected function escapeLikeInternal( $s ) {
2251                 $s = str_replace( '\\', '\\\\', $s );
2252                 $s = $this->strencode( $s );
2253                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2254
2255                 return $s;
2256         }
2257
2258         /**
2259          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2260          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2261          * Alternatively, the function could be provided with an array of aforementioned parameters.
2262          *
2263          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2264          * for subpages of 'My page title'.
2265          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2266          *
2267          * @since 1.16
2268          * @return String: fully built LIKE statement
2269          */
2270         function buildLike() {
2271                 $params = func_get_args();
2272
2273                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2274                         $params = $params[0];
2275                 }
2276
2277                 $s = '';
2278
2279                 foreach ( $params as $value ) {
2280                         if ( $value instanceof LikeMatch ) {
2281                                 $s .= $value->toString();
2282                         } else {
2283                                 $s .= $this->escapeLikeInternal( $value );
2284                         }
2285                 }
2286
2287                 return " LIKE '" . $s . "' ";
2288         }
2289
2290         /**
2291          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2292          *
2293          * @return LikeMatch
2294          */
2295         function anyChar() {
2296                 return new LikeMatch( '_' );
2297         }
2298
2299         /**
2300          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2301          *
2302          * @return LikeMatch
2303          */
2304         function anyString() {
2305                 return new LikeMatch( '%' );
2306         }
2307
2308         /**
2309          * Returns an appropriately quoted sequence value for inserting a new row.
2310          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2311          * subclass will return an integer, and save the value for insertId()
2312          *
2313          * Any implementation of this function should *not* involve reusing
2314          * sequence numbers created for rolled-back transactions.
2315          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2316          * @param $seqName string
2317          * @return null
2318          */
2319         function nextSequenceValue( $seqName ) {
2320                 return null;
2321         }
2322
2323         /**
2324          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2325          * is only needed because a) MySQL must be as efficient as possible due to
2326          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2327          * which index to pick.  Anyway, other databases might have different
2328          * indexes on a given table.  So don't bother overriding this unless you're
2329          * MySQL.
2330          * @param $index
2331          * @return string
2332          */
2333         function useIndexClause( $index ) {
2334                 return '';
2335         }
2336
2337         /**
2338          * REPLACE query wrapper.
2339          *
2340          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2341          * except that when there is a duplicate key error, the old row is deleted
2342          * and the new row is inserted in its place.
2343          *
2344          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2345          * perform the delete, we need to know what the unique indexes are so that
2346          * we know how to find the conflicting rows.
2347          *
2348          * It may be more efficient to leave off unique indexes which are unlikely
2349          * to collide. However if you do this, you run the risk of encountering
2350          * errors which wouldn't have occurred in MySQL.
2351          *
2352          * @param $table String: The table to replace the row(s) in.
2353          * @param $rows array Can be either a single row to insert, or multiple rows,
2354          *    in the same format as for DatabaseBase::insert()
2355          * @param $uniqueIndexes array is an array of indexes. Each element may be either
2356          *    a field name or an array of field names
2357          * @param $fname String: Calling function name (use __METHOD__) for logs/profiling
2358          */
2359         function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseBase::replace' ) {
2360                 $quotedTable = $this->tableName( $table );
2361
2362                 if ( count( $rows ) == 0 ) {
2363                         return;
2364                 }
2365
2366                 # Single row case
2367                 if ( !is_array( reset( $rows ) ) ) {
2368                         $rows = array( $rows );
2369                 }
2370
2371                 foreach( $rows as $row ) {
2372                         # Delete rows which collide
2373                         if ( $uniqueIndexes ) {
2374                                 $sql = "DELETE FROM $quotedTable WHERE ";
2375                                 $first = true;
2376                                 foreach ( $uniqueIndexes as $index ) {
2377                                         if ( $first ) {
2378                                                 $first = false;
2379                                                 $sql .= '( ';
2380                                         } else {
2381                                                 $sql .= ' ) OR ( ';
2382                                         }
2383                                         if ( is_array( $index ) ) {
2384                                                 $first2 = true;
2385                                                 foreach ( $index as $col ) {
2386                                                         if ( $first2 ) {
2387                                                                 $first2 = false;
2388                                                         } else {
2389                                                                 $sql .= ' AND ';
2390                                                         }
2391                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2392                                                 }
2393                                         } else {
2394                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2395                                         }
2396                                 }
2397                                 $sql .= ' )';
2398                                 $this->query( $sql, $fname );
2399                         }
2400
2401                         # Now insert the row
2402                         $this->insert( $table, $row );
2403                 }
2404         }
2405
2406         /**
2407          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2408          * statement.
2409          *
2410          * @param $table string Table name
2411          * @param $rows array Rows to insert
2412          * @param $fname string Caller function name
2413          *
2414          * @return ResultWrapper
2415          */
2416         protected function nativeReplace( $table, $rows, $fname ) {
2417                 $table = $this->tableName( $table );
2418
2419                 # Single row case
2420                 if ( !is_array( reset( $rows ) ) ) {
2421                         $rows = array( $rows );
2422                 }
2423
2424                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2425                 $first = true;
2426
2427                 foreach ( $rows as $row ) {
2428                         if ( $first ) {
2429                                 $first = false;
2430                         } else {
2431                                 $sql .= ',';
2432                         }
2433
2434                         $sql .= '(' . $this->makeList( $row ) . ')';
2435                 }
2436
2437                 return $this->query( $sql, $fname );
2438         }
2439
2440         /**
2441          * DELETE where the condition is a join.
2442          *
2443          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2444          * we use sub-selects
2445          *
2446          * For safety, an empty $conds will not delete everything. If you want to
2447          * delete all rows where the join condition matches, set $conds='*'.
2448          *
2449          * DO NOT put the join condition in $conds.
2450          *
2451          * @param $delTable   String: The table to delete from.
2452          * @param $joinTable  String: The other table.
2453          * @param $delVar     String: The variable to join on, in the first table.
2454          * @param $joinVar    String: The variable to join on, in the second table.
2455          * @param $conds      Array: Condition array of field names mapped to variables,
2456          *                    ANDed together in the WHERE clause
2457          * @param $fname      String: Calling function name (use __METHOD__) for
2458          *                    logs/profiling
2459          */
2460         function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2461                 $fname = 'DatabaseBase::deleteJoin' )
2462         {
2463                 if ( !$conds ) {
2464                         throw new DBUnexpectedError( $this,
2465                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2466                 }
2467
2468                 $delTable = $this->tableName( $delTable );
2469                 $joinTable = $this->tableName( $joinTable );
2470                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2471                 if ( $conds != '*' ) {
2472                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2473                 }
2474                 $sql .= ')';
2475
2476                 $this->query( $sql, $fname );
2477         }
2478
2479         /**
2480          * Returns the size of a text field, or -1 for "unlimited"
2481          *
2482          * @param $table string
2483          * @param $field string
2484          *
2485          * @return int
2486          */
2487         function textFieldSize( $table, $field ) {
2488                 $table = $this->tableName( $table );
2489                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2490                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2491                 $row = $this->fetchObject( $res );
2492
2493                 $m = array();
2494
2495                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2496                         $size = $m[1];
2497                 } else {
2498                         $size = -1;
2499                 }
2500
2501                 return $size;
2502         }
2503
2504         /**
2505          * A string to insert into queries to show that they're low-priority, like
2506          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2507          * string and nothing bad should happen.
2508          *
2509          * @return string Returns the text of the low priority option if it is
2510          *   supported, or a blank string otherwise
2511          */
2512         function lowPriorityOption() {
2513                 return '';
2514         }
2515
2516         /**
2517          * DELETE query wrapper.
2518          *
2519          * @param $table Array Table name
2520          * @param $conds String|Array of conditions. See $conds in DatabaseBase::select() for
2521          *               the format. Use $conds == "*" to delete all rows
2522          * @param $fname String name of the calling function
2523          *
2524          * @return bool
2525          */
2526         function delete( $table, $conds, $fname = 'DatabaseBase::delete' ) {
2527                 if ( !$conds ) {
2528                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2529                 }
2530
2531                 $table = $this->tableName( $table );
2532                 $sql = "DELETE FROM $table";
2533
2534                 if ( $conds != '*' ) {
2535                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2536                 }
2537
2538                 return $this->query( $sql, $fname );
2539         }
2540
2541         /**
2542          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2543          * into another table.
2544          *
2545          * @param $destTable string The table name to insert into
2546          * @param $srcTable string|array May be either a table name, or an array of table names
2547          *    to include in a join.
2548          *
2549          * @param $varMap array must be an associative array of the form
2550          *    array( 'dest1' => 'source1', ...). Source items may be literals
2551          *    rather than field names, but strings should be quoted with
2552          *    DatabaseBase::addQuotes()
2553          *
2554          * @param $conds array Condition array. See $conds in DatabaseBase::select() for
2555          *    the details of the format of condition arrays. May be "*" to copy the
2556          *    whole table.
2557          *
2558          * @param $fname string The function name of the caller, from __METHOD__
2559          *
2560          * @param $insertOptions array Options for the INSERT part of the query, see
2561          *    DatabaseBase::insert() for details.
2562          * @param $selectOptions array Options for the SELECT part of the query, see
2563          *    DatabaseBase::select() for details.
2564          *
2565          * @return ResultWrapper
2566          */
2567         function insertSelect( $destTable, $srcTable, $varMap, $conds,
2568                 $fname = 'DatabaseBase::insertSelect',
2569                 $insertOptions = array(), $selectOptions = array() )
2570         {
2571                 $destTable = $this->tableName( $destTable );
2572
2573                 if ( is_array( $insertOptions ) ) {
2574                         $insertOptions = implode( ' ', $insertOptions );
2575                 }
2576
2577                 if ( !is_array( $selectOptions ) ) {
2578                         $selectOptions = array( $selectOptions );
2579                 }
2580
2581                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2582
2583                 if ( is_array( $srcTable ) ) {
2584                         $srcTable =  implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2585                 } else {
2586                         $srcTable = $this->tableName( $srcTable );
2587                 }
2588
2589                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2590                         " SELECT $startOpts " . implode( ',', $varMap ) .
2591                         " FROM $srcTable $useIndex ";
2592
2593                 if ( $conds != '*' ) {
2594                         if ( is_array( $conds ) ) {
2595                                 $conds = $this->makeList( $conds, LIST_AND );
2596                         }
2597                         $sql .= " WHERE $conds";
2598                 }
2599
2600                 $sql .= " $tailOpts";
2601
2602                 return $this->query( $sql, $fname );
2603         }
2604
2605         /**
2606          * Construct a LIMIT query with optional offset.  This is used for query
2607          * pages.  The SQL should be adjusted so that only the first $limit rows
2608          * are returned.  If $offset is provided as well, then the first $offset
2609          * rows should be discarded, and the next $limit rows should be returned.
2610          * If the result of the query is not ordered, then the rows to be returned
2611          * are theoretically arbitrary.
2612          *
2613          * $sql is expected to be a SELECT, if that makes a difference.  For
2614          * UPDATE, limitResultForUpdate should be used.
2615          *
2616          * The version provided by default works in MySQL and SQLite.  It will very
2617          * likely need to be overridden for most other DBMSes.
2618          *
2619          * @param $sql String SQL query we will append the limit too
2620          * @param $limit Integer the SQL limit
2621          * @param $offset Integer|bool the SQL offset (default false)
2622          *
2623          * @return string
2624          */
2625         function limitResult( $sql, $limit, $offset = false ) {
2626                 if ( !is_numeric( $limit ) ) {
2627                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2628                 }
2629
2630                 return "$sql LIMIT "
2631                                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2632                                 . "{$limit} ";
2633         }
2634
2635         /**
2636          * @param $sql
2637          * @param $num
2638          * @return string
2639          */
2640         function limitResultForUpdate( $sql, $num ) {
2641                 return $this->limitResult( $sql, $num, 0 );
2642         }
2643
2644         /**
2645          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2646          * within the UNION construct.
2647          * @return Boolean
2648          */
2649         function unionSupportsOrderAndLimit() {
2650                 return true; // True for almost every DB supported
2651         }
2652
2653         /**
2654          * Construct a UNION query
2655          * This is used for providing overload point for other DB abstractions
2656          * not compatible with the MySQL syntax.
2657          * @param $sqls Array: SQL statements to combine
2658          * @param $all Boolean: use UNION ALL
2659          * @return String: SQL fragment
2660          */
2661         function unionQueries( $sqls, $all ) {
2662                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2663                 return '(' . implode( $glue, $sqls ) . ')';
2664         }
2665
2666         /**
2667          * Returns an SQL expression for a simple conditional.  This doesn't need
2668          * to be overridden unless CASE isn't supported in your DBMS.
2669          *
2670          * @param $cond String: SQL expression which will result in a boolean value
2671          * @param $trueVal String: SQL expression to return if true
2672          * @param $falseVal String: SQL expression to return if false
2673          * @return String: SQL fragment
2674          */
2675         function conditional( $cond, $trueVal, $falseVal ) {
2676                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2677         }
2678
2679         /**
2680          * Returns a comand for str_replace function in SQL query.
2681          * Uses REPLACE() in MySQL
2682          *
2683          * @param $orig String: column to modify
2684          * @param $old String: column to seek
2685          * @param $new String: column to replace with
2686          *
2687          * @return string
2688          */
2689         function strreplace( $orig, $old, $new ) {
2690                 return "REPLACE({$orig}, {$old}, {$new})";
2691         }
2692
2693         /**
2694          * Determines how long the server has been up
2695          * STUB
2696          *
2697          * @return int
2698          */
2699         function getServerUptime() {
2700                 return 0;
2701         }
2702
2703         /**
2704          * Determines if the last failure was due to a deadlock
2705          * STUB
2706          *
2707          * @return bool
2708          */
2709         function wasDeadlock() {
2710                 return false;
2711         }
2712
2713         /**
2714          * Determines if the last failure was due to a lock timeout
2715          * STUB
2716          *
2717          * @return bool
2718          */
2719         function wasLockTimeout() {
2720                 return false;
2721         }
2722
2723         /**
2724          * Determines if the last query error was something that should be dealt
2725          * with by pinging the connection and reissuing the query.
2726          * STUB
2727          *
2728          * @return bool
2729          */
2730         function wasErrorReissuable() {
2731                 return false;
2732         }
2733
2734         /**
2735          * Determines if the last failure was due to the database being read-only.
2736          * STUB
2737          *
2738          * @return bool
2739          */
2740         function wasReadOnlyError() {
2741                 return false;
2742         }
2743
2744         /**
2745          * Perform a deadlock-prone transaction.
2746          *
2747          * This function invokes a callback function to perform a set of write
2748          * queries. If a deadlock occurs during the processing, the transaction
2749          * will be rolled back and the callback function will be called again.
2750          *
2751          * Usage:
2752          *   $dbw->deadlockLoop( callback, ... );
2753          *
2754          * Extra arguments are passed through to the specified callback function.
2755          *
2756          * Returns whatever the callback function returned on its successful,
2757          * iteration, or false on error, for example if the retry limit was
2758          * reached.
2759          *
2760          * @return bool
2761          */
2762         function deadlockLoop() {
2763
2764                 $this->begin( __METHOD__ );
2765                 $args = func_get_args();
2766                 $function = array_shift( $args );
2767                 $oldIgnore = $this->ignoreErrors( true );
2768                 $tries = DEADLOCK_TRIES;
2769
2770                 if ( is_array( $function ) ) {
2771                         $fname = $function[0];
2772                 } else {
2773                         $fname = $function;
2774                 }
2775
2776                 do {
2777                         $retVal = call_user_func_array( $function, $args );
2778                         $error = $this->lastError();
2779                         $errno = $this->lastErrno();
2780                         $sql = $this->lastQuery();
2781
2782                         if ( $errno ) {
2783                                 if ( $this->wasDeadlock() ) {
2784                                         # Retry
2785                                         usleep( mt_rand( DEADLOCK_DELAY_MIN, DEADLOCK_DELAY_MAX ) );
2786                                 } else {
2787                                         $this->reportQueryError( $error, $errno, $sql, $fname );
2788                                 }
2789                         }
2790                 } while ( $this->wasDeadlock() && --$tries > 0 );
2791
2792                 $this->ignoreErrors( $oldIgnore );
2793
2794                 if ( $tries <= 0 ) {
2795                         $this->rollback( __METHOD__ );
2796                         $this->reportQueryError( $error, $errno, $sql, $fname );
2797                         return false;
2798                 } else {
2799                         $this->commit( __METHOD__ );
2800                         return $retVal;
2801                 }
2802         }
2803
2804         /**
2805          * Wait for the slave to catch up to a given master position.
2806          *
2807          * @param $pos DBMasterPos object
2808          * @param $timeout Integer: the maximum number of seconds to wait for
2809          *   synchronisation
2810          *
2811          * @return integer: zero if the slave was past that position already,
2812          *   greater than zero if we waited for some period of time, less than
2813          *   zero if we timed out.
2814          */
2815         function masterPosWait( DBMasterPos $pos, $timeout ) {
2816                 wfProfileIn( __METHOD__ );
2817
2818                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2819                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
2820
2821                         if ( $wait > $timeout * 1e6 ) {
2822                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
2823                                 wfProfileOut( __METHOD__ );
2824                                 return -1;
2825                         } elseif ( $wait > 0 ) {
2826                                 wfDebug( "Fake slave waiting $wait us\n" );
2827                                 usleep( $wait );
2828                                 wfProfileOut( __METHOD__ );
2829                                 return 1;
2830                         } else {
2831                                 wfDebug( "Fake slave up to date ($wait us)\n" );
2832                                 wfProfileOut( __METHOD__ );
2833                                 return 0;
2834                         }
2835                 }
2836
2837                 wfProfileOut( __METHOD__ );
2838
2839                 # Real waits are implemented in the subclass.
2840                 return 0;
2841         }
2842
2843         /**
2844          * Get the replication position of this slave
2845          *
2846          * @return DBMasterPos, or false if this is not a slave.
2847          */
2848         function getSlavePos() {
2849                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2850                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
2851                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
2852                         return $pos;
2853                 } else {
2854                         # Stub
2855                         return false;
2856                 }
2857         }
2858
2859         /**
2860          * Get the position of this master
2861          *
2862          * @return DBMasterPos, or false if this is not a master
2863          */
2864         function getMasterPos() {
2865                 if ( $this->mFakeMaster ) {
2866                         return new MySQLMasterPos( 'fake', microtime( true ) );
2867                 } else {
2868                         return false;
2869                 }
2870         }
2871
2872         /**
2873          * Begin a transaction, committing any previously open transaction
2874          *
2875          * @param $fname string
2876          */
2877         function begin( $fname = 'DatabaseBase::begin' ) {
2878                 $this->query( 'BEGIN', $fname );
2879                 $this->mTrxLevel = 1;
2880         }
2881
2882         /**
2883          * End a transaction
2884          *
2885          * @param $fname string
2886          */
2887         function commit( $fname = 'DatabaseBase::commit' ) {
2888                 if ( $this->mTrxLevel ) {
2889                         $this->query( 'COMMIT', $fname );
2890                         $this->mTrxLevel = 0;
2891                 }
2892         }
2893
2894         /**
2895          * Rollback a transaction.
2896          * No-op on non-transactional databases.
2897          *
2898          * @param $fname string
2899          */
2900         function rollback( $fname = 'DatabaseBase::rollback' ) {
2901                 if ( $this->mTrxLevel ) {
2902                         $this->query( 'ROLLBACK', $fname, true );
2903                         $this->mTrxLevel = 0;
2904                 }
2905         }
2906
2907         /**
2908          * Creates a new table with structure copied from existing table
2909          * Note that unlike most database abstraction functions, this function does not
2910          * automatically append database prefix, because it works at a lower
2911          * abstraction level.
2912          * The table names passed to this function shall not be quoted (this
2913          * function calls addIdentifierQuotes when needed).
2914          *
2915          * @param $oldName String: name of table whose structure should be copied
2916          * @param $newName String: name of table to be created
2917          * @param $temporary Boolean: whether the new table should be temporary
2918          * @param $fname String: calling function name
2919          * @return Boolean: true if operation was successful
2920          */
2921         function duplicateTableStructure( $oldName, $newName, $temporary = false,
2922                 $fname = 'DatabaseBase::duplicateTableStructure' )
2923         {
2924                 throw new MWException(
2925                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
2926         }
2927
2928         /**
2929          * List all tables on the database
2930          *
2931          * @param $prefix string Only show tables with this prefix, e.g. mw_
2932          * @param $fname String: calling function name
2933          */
2934         function listTables( $prefix = null, $fname = 'DatabaseBase::listTables' ) {
2935                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
2936         }
2937
2938         /**
2939          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2940          * to the format used for inserting into timestamp fields in this DBMS.
2941          *
2942          * The result is unquoted, and needs to be passed through addQuotes()
2943          * before it can be included in raw SQL.
2944          *
2945          * @param $ts string|int
2946          *
2947          * @return string
2948          */
2949         function timestamp( $ts = 0 ) {
2950                 return wfTimestamp( TS_MW, $ts );
2951         }
2952
2953         /**
2954          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2955          * to the format used for inserting into timestamp fields in this DBMS. If
2956          * NULL is input, it is passed through, allowing NULL values to be inserted
2957          * into timestamp fields.
2958          *
2959          * The result is unquoted, and needs to be passed through addQuotes()
2960          * before it can be included in raw SQL.
2961          *
2962          * @param $ts string|int
2963          *
2964          * @return string
2965          */
2966         function timestampOrNull( $ts = null ) {
2967                 if ( is_null( $ts ) ) {
2968                         return null;
2969                 } else {
2970                         return $this->timestamp( $ts );
2971                 }
2972         }
2973
2974         /**
2975          * Take the result from a query, and wrap it in a ResultWrapper if
2976          * necessary. Boolean values are passed through as is, to indicate success
2977          * of write queries or failure.
2978          *
2979          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
2980          * resource, and it was necessary to call this function to convert it to
2981          * a wrapper. Nowadays, raw database objects are never exposed to external
2982          * callers, so this is unnecessary in external code. For compatibility with
2983          * old code, ResultWrapper objects are passed through unaltered.
2984          *
2985          * @param $result bool|ResultWrapper
2986          *
2987          * @return bool|ResultWrapper
2988          */
2989         function resultObject( $result ) {
2990                 if ( empty( $result ) ) {
2991                         return false;
2992                 } elseif ( $result instanceof ResultWrapper ) {
2993                         return $result;
2994                 } elseif ( $result === true ) {
2995                         // Successful write query
2996                         return $result;
2997                 } else {
2998                         return new ResultWrapper( $this, $result );
2999                 }
3000         }
3001
3002         /**
3003          * Return aggregated value alias
3004          *
3005          * @param $valuedata
3006          * @param $valuename string
3007          *
3008          * @return string
3009          */
3010         function aggregateValue ( $valuedata, $valuename = 'value' ) {
3011                 return $valuename;
3012         }
3013
3014         /**
3015          * Ping the server and try to reconnect if it there is no connection
3016          *
3017          * @return bool Success or failure
3018          */
3019         function ping() {
3020                 # Stub.  Not essential to override.
3021                 return true;
3022         }
3023
3024         /**
3025          * Get slave lag. Currently supported only by MySQL.
3026          *
3027          * Note that this function will generate a fatal error on many
3028          * installations. Most callers should use LoadBalancer::safeGetLag()
3029          * instead.
3030          *
3031          * @return int Database replication lag in seconds
3032          */
3033         function getLag() {
3034                 return intval( $this->mFakeSlaveLag );
3035         }
3036
3037         /**
3038          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3039          *
3040          * @return int
3041          */
3042         function maxListLen() {
3043                 return 0;
3044         }
3045
3046         /**
3047          * Some DBMSs have a special format for inserting into blob fields, they
3048          * don't allow simple quoted strings to be inserted. To insert into such
3049          * a field, pass the data through this function before passing it to
3050          * DatabaseBase::insert().
3051          * @param $b string
3052          * @return string
3053          */
3054         function encodeBlob( $b ) {
3055                 return $b;
3056         }
3057
3058         /**
3059          * Some DBMSs return a special placeholder object representing blob fields
3060          * in result objects. Pass the object through this function to return the
3061          * original string.
3062          * @param $b string
3063          * @return string
3064          */
3065         function decodeBlob( $b ) {
3066                 return $b;
3067         }
3068
3069         /**
3070          * Override database's default connection timeout
3071          *
3072          * @param $timeout Integer in seconds
3073          * @return void
3074          * @deprecated since 1.19; use setSessionOptions()
3075          */
3076         public function setTimeout( $timeout ) {
3077                 wfDeprecated( __METHOD__, '1.19' );
3078                 $this->setSessionOptions( array( 'connTimeout' => $timeout ) );
3079         }
3080
3081         /**
3082          * Override database's default behavior. $options include:
3083          *     'connTimeout' : Set the connection timeout value in seconds.
3084          *                     May be useful for very long batch queries such as
3085          *                     full-wiki dumps, where a single query reads out over
3086          *                     hours or days.
3087          *
3088          * @param $options Array
3089          * @return void
3090          */
3091         public function setSessionOptions( array $options ) {}
3092
3093         /**
3094          * Read and execute SQL commands from a file.
3095          *
3096          * Returns true on success, error string or exception on failure (depending
3097          * on object's error ignore settings).
3098          *
3099          * @param $filename String: File name to open
3100          * @param $lineCallback Callback: Optional function called before reading each line
3101          * @param $resultCallback Callback: Optional function called for each MySQL result
3102          * @param $fname String: Calling function name or false if name should be
3103          *      generated dynamically using $filename
3104          * @return bool|string
3105          */
3106         function sourceFile( $filename, $lineCallback = false, $resultCallback = false, $fname = false ) {
3107                 wfSuppressWarnings();
3108                 $fp = fopen( $filename, 'r' );
3109                 wfRestoreWarnings();
3110
3111                 if ( false === $fp ) {
3112                         throw new MWException( "Could not open \"{$filename}\".\n" );
3113                 }
3114
3115                 if ( !$fname ) {
3116                         $fname = __METHOD__ . "( $filename )";
3117                 }
3118
3119                 try {
3120                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname );
3121                 }
3122                 catch ( MWException $e ) {
3123                         fclose( $fp );
3124                         throw $e;
3125                 }
3126
3127                 fclose( $fp );
3128
3129                 return $error;
3130         }
3131
3132         /**
3133          * Get the full path of a patch file. Originally based on archive()
3134          * from updaters.inc. Keep in mind this always returns a patch, as
3135          * it fails back to MySQL if no DB-specific patch can be found
3136          *
3137          * @param $patch String The name of the patch, like patch-something.sql
3138          * @return String Full path to patch file
3139          */
3140         public function patchPath( $patch ) {
3141                 global $IP;
3142
3143                 $dbType = $this->getType();
3144                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3145                         return "$IP/maintenance/$dbType/archives/$patch";
3146                 } else {
3147                         return "$IP/maintenance/archives/$patch";
3148                 }
3149         }
3150
3151         /**
3152          * Set variables to be used in sourceFile/sourceStream, in preference to the
3153          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3154          * all. If it's set to false, $GLOBALS will be used.
3155          *
3156          * @param $vars bool|array mapping variable name to value.
3157          */
3158         function setSchemaVars( $vars ) {
3159                 $this->mSchemaVars = $vars;
3160         }
3161
3162         /**
3163          * Read and execute commands from an open file handle.
3164          *
3165          * Returns true on success, error string or exception on failure (depending
3166          * on object's error ignore settings).
3167          *
3168          * @param $fp Resource: File handle
3169          * @param $lineCallback Callback: Optional function called before reading each line
3170          * @param $resultCallback Callback: Optional function called for each MySQL result
3171          * @param $fname String: Calling function name
3172          * @param $inputCallback Callback: Optional function called for each complete line (ended with ;) sent
3173          * @return bool|string
3174          */
3175         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3176                 $fname = 'DatabaseBase::sourceStream', $inputCallback = false )
3177         {
3178                 $cmd = '';
3179
3180                 while ( !feof( $fp ) ) {
3181                         if ( $lineCallback ) {
3182                                 call_user_func( $lineCallback );
3183                         }
3184
3185                         $line = trim( fgets( $fp ) );
3186
3187                         if ( $line == '' ) {
3188                                 continue;
3189                         }
3190
3191                         if ( '-' == $line[0] && '-' == $line[1] ) {
3192                                 continue;
3193                         }
3194
3195                         if ( $cmd != '' ) {
3196                                 $cmd .= ' ';
3197                         }
3198
3199                         $done = $this->streamStatementEnd( $cmd, $line );
3200
3201                         $cmd .= "$line\n";
3202
3203                         if ( $done || feof( $fp ) ) {
3204                                 $cmd = $this->replaceVars( $cmd );
3205                                 if ( $inputCallback ) {
3206                                         call_user_func( $inputCallback, $cmd );
3207                                 }
3208                                 $res = $this->query( $cmd, $fname );
3209
3210                                 if ( $resultCallback ) {
3211                                         call_user_func( $resultCallback, $res, $this );
3212                                 }
3213
3214                                 if ( false === $res ) {
3215                                         $err = $this->lastError();
3216                                         return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3217                                 }
3218
3219                                 $cmd = '';
3220                         }
3221                 }
3222
3223                 return true;
3224         }
3225
3226         /**
3227          * Called by sourceStream() to check if we've reached a statement end
3228          *
3229          * @param $sql String SQL assembled so far
3230          * @param $newLine String New line about to be added to $sql
3231          * @return Bool Whether $newLine contains end of the statement
3232          */
3233         public function streamStatementEnd( &$sql, &$newLine ) {
3234                 if ( $this->delimiter ) {
3235                         $prev = $newLine;
3236                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3237                         if ( $newLine != $prev ) {
3238                                 return true;
3239                         }
3240                 }
3241                 return false;
3242         }
3243
3244         /**
3245          * Database independent variable replacement. Replaces a set of variables
3246          * in an SQL statement with their contents as given by $this->getSchemaVars().
3247          *
3248          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3249          *
3250          * - '{$var}' should be used for text and is passed through the database's
3251          *   addQuotes method.
3252          * - `{$var}` should be used for identifiers (eg: table and database names),
3253          *   it is passed through the database's addIdentifierQuotes method which
3254          *   can be overridden if the database uses something other than backticks.
3255          * - / *$var* / is just encoded, besides traditional table prefix and
3256          *   table options its use should be avoided.
3257          *
3258          * @param $ins String: SQL statement to replace variables in
3259          * @return String The new SQL statement with variables replaced
3260          */
3261         protected function replaceSchemaVars( $ins ) {
3262                 $vars = $this->getSchemaVars();
3263                 foreach ( $vars as $var => $value ) {
3264                         // replace '{$var}'
3265                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3266                         // replace `{$var}`
3267                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3268                         // replace /*$var*/
3269                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ) , $ins );
3270                 }
3271                 return $ins;
3272         }
3273
3274         /**
3275          * Replace variables in sourced SQL
3276          *
3277          * @param $ins string
3278          *
3279          * @return string
3280          */
3281         protected function replaceVars( $ins ) {
3282                 $ins = $this->replaceSchemaVars( $ins );
3283
3284                 // Table prefixes
3285                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3286                         array( $this, 'tableNameCallback' ), $ins );
3287
3288                 // Index names
3289                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3290                         array( $this, 'indexNameCallback' ), $ins );
3291
3292                 return $ins;
3293         }
3294
3295         /**
3296          * Get schema variables. If none have been set via setSchemaVars(), then
3297          * use some defaults from the current object.
3298          *
3299          * @return array
3300          */
3301         protected function getSchemaVars() {
3302                 if ( $this->mSchemaVars ) {
3303                         return $this->mSchemaVars;
3304                 } else {
3305                         return $this->getDefaultSchemaVars();
3306                 }
3307         }
3308
3309         /**
3310          * Get schema variables to use if none have been set via setSchemaVars().
3311          *
3312          * Override this in derived classes to provide variables for tables.sql
3313          * and SQL patch files.
3314          *
3315          * @return array
3316          */
3317         protected function getDefaultSchemaVars() {
3318                 return array();
3319         }
3320
3321         /**
3322          * Table name callback
3323          *
3324          * @param $matches array
3325          *
3326          * @return string
3327          */
3328         protected function tableNameCallback( $matches ) {
3329                 return $this->tableName( $matches[1] );
3330         }
3331
3332         /**
3333          * Index name callback
3334          *
3335          * @param $matches array
3336          *
3337          * @return string
3338          */
3339         protected function indexNameCallback( $matches ) {
3340                 return $this->indexName( $matches[1] );
3341         }
3342
3343         /**
3344          * Build a concatenation list to feed into a SQL query
3345          * @param $stringList Array: list of raw SQL expressions; caller is responsible for any quoting
3346          * @return String
3347          */
3348         function buildConcat( $stringList ) {
3349                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
3350         }
3351
3352         /**
3353          * Acquire a named lock
3354          *
3355          * Abstracted from Filestore::lock() so child classes can implement for
3356          * their own needs.
3357          *
3358          * @param $lockName String: name of lock to aquire
3359          * @param $method String: name of method calling us
3360          * @param $timeout Integer: timeout
3361          * @return Boolean
3362          */
3363         public function lock( $lockName, $method, $timeout = 5 ) {
3364                 return true;
3365         }
3366
3367         /**
3368          * Release a lock.
3369          *
3370          * @param $lockName String: Name of lock to release
3371          * @param $method String: Name of method calling us
3372          *
3373          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3374          * by this thread (in which case the lock is not released), and NULL if the named
3375          * lock did not exist
3376          */
3377         public function unlock( $lockName, $method ) {
3378                 return true;
3379         }
3380
3381         /**
3382          * Lock specific tables
3383          *
3384          * @param $read Array of tables to lock for read access
3385          * @param $write Array of tables to lock for write access
3386          * @param $method String name of caller
3387          * @param $lowPriority bool Whether to indicate writes to be LOW PRIORITY
3388          *
3389          * @return bool
3390          */
3391         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3392                 return true;
3393         }
3394
3395         /**
3396          * Unlock specific tables
3397          *
3398          * @param $method String the caller
3399          *
3400          * @return bool
3401          */
3402         public function unlockTables( $method ) {
3403                 return true;
3404         }
3405
3406         /**
3407          * Delete a table
3408          * @param $tableName string
3409          * @param $fName string
3410          * @return bool|ResultWrapper
3411          * @since 1.18
3412          */
3413         public function dropTable( $tableName, $fName = 'DatabaseBase::dropTable' ) {
3414                 if( !$this->tableExists( $tableName, $fName ) ) {
3415                         return false;
3416                 }
3417                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3418                 if( $this->cascadingDeletes() ) {
3419                         $sql .= " CASCADE";
3420                 }
3421                 return $this->query( $sql, $fName );
3422         }
3423
3424         /**
3425          * Get search engine class. All subclasses of this need to implement this
3426          * if they wish to use searching.
3427          *
3428          * @return String
3429          */
3430         public function getSearchEngine() {
3431                 return 'SearchEngineDummy';
3432         }
3433
3434         /**
3435          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3436          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3437          * because "i" sorts after all numbers.
3438          *
3439          * @return String
3440          */
3441         public function getInfinity() {
3442                 return 'infinity';
3443         }
3444
3445         /**
3446          * Encode an expiry time into the DBMS dependent format
3447          *
3448          * @param $expiry String: timestamp for expiry, or the 'infinity' string
3449          * @return String
3450          */
3451         public function encodeExpiry( $expiry ) {
3452                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3453                         ? $this->getInfinity()
3454                         : $this->timestamp( $expiry );
3455         }
3456
3457         /**
3458          * Decode an expiry time into a DBMS independent format
3459          *
3460          * @param $expiry String: DB timestamp field value for expiry
3461          * @param $format integer: TS_* constant, defaults to TS_MW
3462          * @return String
3463          */
3464         public function decodeExpiry( $expiry, $format = TS_MW ) {
3465                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3466                         ? 'infinity'
3467                         : wfTimestamp( $format, $expiry );
3468         }
3469
3470         /**
3471          * Allow or deny "big selects" for this session only. This is done by setting
3472          * the sql_big_selects session variable.
3473          *
3474          * This is a MySQL-specific feature.
3475          *
3476          * @param $value Mixed: true for allow, false for deny, or "default" to
3477          *   restore the initial value
3478          */
3479         public function setBigSelects( $value = true ) {
3480                 // no-op
3481         }
3482 }