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