includes/db/Database.php

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