includes/db/Database.php

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