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 ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 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                                 $this->begin( __METHOD__ . " ($fname)" );
 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                         $master = $isMaster ? 'master' : 'slave';
 850                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 851                 }
 852
 853                 if ( istainted( $sql ) & TC_MYSQL ) {
 854                         throw new MWException( 'Tainted query found' );
 855                 }
 856
 857                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 858
 859                 # Do the query and handle errors
 860                 $ret = $this->doQuery( $commentedSql );
 861
 862                 MWDebug::queryTime( $queryId );
 863
 864                 # Try reconnecting if the connection was lost
 865                 if ( false === $ret && $this->wasErrorReissuable() ) {
 866                         # Transaction is gone, like it or not
 867                         $this->mTrxLevel = 0;
 868                         wfDebug( "Connection lost, reconnecting...\n" );
 869
 870                         if ( $this->ping() ) {
 871                                 wfDebug( "Reconnected\n" );
 872                                 $sqlx = substr( $commentedSql, 0, 500 );
 873                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
 874                                 global $wgRequestTime;
 875                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
 876                                 if ( $elapsed < 300 ) {
 877                                         # Not a database error to lose a transaction after a minute or two
 878                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
 879                                 }
 880                                 $ret = $this->doQuery( $commentedSql );
 881                         } else {
 882                                 wfDebug( "Failed\n" );
 883                         }
 884                 }
 885
 886                 if ( false === $ret ) {
 887                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 888                 }
 889
 890                 if ( !Profiler::instance()->isStub() ) {
 891                         wfProfileOut( $queryProf );
 892                         wfProfileOut( $totalProf );
 893                 }
 894
 895                 return $this->resultObject( $ret );
 896         }
 897
 898         /**
 899          * Report a query error. Log the error, and if neither the object ignore
 900          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
 901          *
 902          * @param $error String
 903          * @param $errno Integer
 904          * @param $sql String
 905          * @param $fname String
 906          * @param $tempIgnore Boolean
 907          */
 908         function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
 909                 # Ignore errors during error handling to avoid infinite recursion
 910                 $ignore = $this->ignoreErrors( true );
 911                 ++$this->mErrorCount;
 912
 913                 if ( $ignore || $tempIgnore ) {
 914                         wfDebug( "SQL ERROR (ignored): $error\n" );
 915                         $this->ignoreErrors( $ignore );
 916                 } else {
 917                         $sql1line = str_replace( "\n", "\\n", $sql );
 918                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
 919                         wfDebug( "SQL ERROR: " . $error . "\n" );
 920                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
 921                 }
 922         }
 923
 924         /**
 925          * Intended to be compatible with the PEAR::DB wrapper functions.
 926          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
 927          *
 928          * ? = scalar value, quoted as necessary
 929          * ! = raw SQL bit (a function for instance)
 930          * & = filename; reads the file and inserts as a blob
 931          *     (we don't use this though...)
 932          *
 933          * This function should not be used directly by new code outside of the
 934          * database classes. The query wrapper functions (select() etc.) should be
 935          * used instead.
 936          *
 937          * @param $sql string
 938          * @param $func string
 939          *
 940          * @return array
 941          */
 942         function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
 943                 /* MySQL doesn't support prepared statements (yet), so just
 944                    pack up the query for reference. We'll manually replace
 945                    the bits later. */
 946                 return array( 'query' => $sql, 'func' => $func );
 947         }
 948
 949         /**
 950          * Free a prepared query, generated by prepare().
 951          * @param $prepared
 952          */
 953         function freePrepared( $prepared ) {
 954                 /* No-op by default */
 955         }
 956
 957         /**
 958          * Execute a prepared query with the various arguments
 959          * @param $prepared String: the prepared sql
 960          * @param $args Mixed: Either an array here, or put scalars as varargs
 961          *
 962          * @return ResultWrapper
 963          */
 964         function execute( $prepared, $args = null ) {
 965                 if ( !is_array( $args ) ) {
 966                         # Pull the var args
 967                         $args = func_get_args();
 968                         array_shift( $args );
 969                 }
 970
 971                 $sql = $this->fillPrepared( $prepared['query'], $args );
 972
 973                 return $this->query( $sql, $prepared['func'] );
 974         }
 975
 976         /**
 977          * Prepare & execute an SQL statement, quoting and inserting arguments
 978          * in the appropriate places.
 979          *
 980          * This function should not be used directly by new code outside of the
 981          * database classes. The query wrapper functions (select() etc.) should be
 982          * used instead.
 983          *
 984          * @param $query String
 985          * @param $args ...
 986          *
 987          * @return ResultWrapper
 988          */
 989         function safeQuery( $query, $args = null ) {
 990                 $prepared = $this->prepare( $query, 'DatabaseBase::safeQuery' );
 991
 992                 if ( !is_array( $args ) ) {
 993                         # Pull the var args
 994                         $args = func_get_args();
 995                         array_shift( $args );
 996                 }
 997
 998                 $retval = $this->execute( $prepared, $args );
 999                 $this->freePrepared( $prepared );
1000
1001                 return $retval;
1002         }
1003
1004         /**
1005          * For faking prepared SQL statements on DBs that don't support
1006          * it directly.
1007          * @param $preparedQuery String: a 'preparable' SQL statement
1008          * @param $args Array of arguments to fill it with
1009          * @return string executable SQL
1010          */
1011         function fillPrepared( $preparedQuery, $args ) {
1012                 reset( $args );
1013                 $this->preparedArgs =& $args;
1014
1015                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1016                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1017         }
1018
1019         /**
1020          * preg_callback func for fillPrepared()
1021          * The arguments should be in $this->preparedArgs and must not be touched
1022          * while we're doing this.
1023          *
1024          * @param $matches Array
1025          * @return String
1026          */
1027         function fillPreparedArg( $matches ) {
1028                 switch( $matches[1] ) {
1029                         case '\\?': return '?';
1030                         case '\\!': return '!';
1031                         case '\\&': return '&';
1032                 }
1033
1034                 list( /* $n */ , $arg ) = each( $this->preparedArgs );
1035
1036                 switch( $matches[1] ) {
1037                         case '?': return $this->addQuotes( $arg );
1038                         case '!': return $arg;
1039                         case '&':
1040                                 # return $this->addQuotes( file_get_contents( $arg ) );
1041                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1042                         default:
1043                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1044                 }
1045         }
1046
1047         /**
1048          * Free a result object returned by query() or select(). It's usually not
1049          * necessary to call this, just use unset() or let the variable holding
1050          * the result object go out of scope.
1051          *
1052          * @param $res Mixed: A SQL result
1053          */
1054         function freeResult( $res ) {
1055         }
1056
1057         /**
1058          * Simple UPDATE wrapper.
1059          * Usually throws a DBQueryError on failure.
1060          * If errors are explicitly ignored, returns success
1061          *
1062          * This function exists for historical reasons, DatabaseBase::update() has a more standard
1063          * calling convention and feature set
1064          *
1065          * @param $table string
1066          * @param $var
1067          * @param $value
1068          * @param $cond
1069          * @param $fname string
1070          *
1071          * @return bool
1072          */
1073         function set( $table, $var, $value, $cond, $fname = 'DatabaseBase::set' ) {
1074                 $table = $this->tableName( $table );
1075                 $sql = "UPDATE $table SET $var = '" .
1076                   $this->strencode( $value ) . "' WHERE ($cond)";
1077
1078                 return (bool)$this->query( $sql, $fname );
1079         }
1080
1081         /**
1082          * A SELECT wrapper which returns a single field from a single result row.
1083          *
1084          * Usually throws a DBQueryError on failure. If errors are explicitly
1085          * ignored, returns false on failure.
1086          *
1087          * If no result rows are returned from the query, false is returned.
1088          *
1089          * @param $table string|array Table name. See DatabaseBase::select() for details.
1090          * @param $var string The field name to select. This must be a valid SQL
1091          *   fragment: do not use unvalidated user input.
1092          * @param $cond string|array The condition array. See DatabaseBase::select() for details.
1093          * @param $fname string The function name of the caller.
1094          * @param $options string|array The query options. See DatabaseBase::select() for details.
1095          *
1096          * @return false|mixed The value from the field, or false on failure.
1097          */
1098         function selectField( $table, $var, $cond = '', $fname = 'DatabaseBase::selectField',
1099                 $options = array() )
1100         {
1101                 if ( !is_array( $options ) ) {
1102                         $options = array( $options );
1103                 }
1104
1105                 $options['LIMIT'] = 1;
1106
1107                 $res = $this->select( $table, $var, $cond, $fname, $options );
1108
1109                 if ( $res === false || !$this->numRows( $res ) ) {
1110                         return false;
1111                 }
1112
1113                 $row = $this->fetchRow( $res );
1114
1115                 if ( $row !== false ) {
1116                         return reset( $row );
1117                 } else {
1118                         return false;
1119                 }
1120         }
1121
1122         /**
1123          * Returns an optional USE INDEX clause to go after the table, and a
1124          * string to go at the end of the query.
1125          *
1126          * @param $options Array: associative array of options to be turned into
1127          *              an SQL query, valid keys are listed in the function.
1128          * @return Array
1129          * @see DatabaseBase::select()
1130          */
1131         function makeSelectOptions( $options ) {
1132                 $preLimitTail = $postLimitTail = '';
1133                 $startOpts = '';
1134
1135                 $noKeyOptions = array();
1136
1137                 foreach ( $options as $key => $option ) {
1138                         if ( is_numeric( $key ) ) {
1139                                 $noKeyOptions[$option] = true;
1140                         }
1141                 }
1142
1143                 if ( isset( $options['GROUP BY'] ) ) {
1144                         $gb = is_array( $options['GROUP BY'] )
1145                                 ? implode( ',', $options['GROUP BY'] )
1146                                 : $options['GROUP BY'];
1147                         $preLimitTail .= " GROUP BY {$gb}";
1148                 }
1149
1150                 if ( isset( $options['HAVING'] ) ) {
1151                         $preLimitTail .= " HAVING {$options['HAVING']}";
1152                 }
1153
1154                 if ( isset( $options['ORDER BY'] ) ) {
1155                         $ob = is_array( $options['ORDER BY'] )
1156                                 ? implode( ',', $options['ORDER BY'] )
1157                                 : $options['ORDER BY'];
1158                         $preLimitTail .= " ORDER BY {$ob}";
1159                 }
1160
1161                 // if (isset($options['LIMIT'])) {
1162                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1163                 //              isset($options['OFFSET']) ? $options['OFFSET']
1164                 //              : false);
1165                 // }
1166
1167                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1168                         $postLimitTail .= ' FOR UPDATE';
1169                 }
1170
1171                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1172                         $postLimitTail .= ' LOCK IN SHARE MODE';
1173                 }
1174
1175                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1176                         $startOpts .= 'DISTINCT';
1177                 }
1178
1179                 # Various MySQL extensions
1180                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1181                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1182                 }
1183
1184                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1185                         $startOpts .= ' HIGH_PRIORITY';
1186                 }
1187
1188                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1189                         $startOpts .= ' SQL_BIG_RESULT';
1190                 }
1191
1192                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1193                         $startOpts .= ' SQL_BUFFER_RESULT';
1194                 }
1195
1196                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1197                         $startOpts .= ' SQL_SMALL_RESULT';
1198                 }
1199
1200                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1201                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1202                 }
1203
1204                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1205                         $startOpts .= ' SQL_CACHE';
1206                 }
1207
1208                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1209                         $startOpts .= ' SQL_NO_CACHE';
1210                 }
1211
1212                 if ( isset( $options['USE INDEX'] ) && ! is_array( $options['USE INDEX'] ) ) {
1213                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1214                 } else {
1215                         $useIndex = '';
1216                 }
1217
1218                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1219         }
1220
1221         /**
1222          * Execute a SELECT query constructed using the various parameters provided.
1223          * See below for full details of the parameters.
1224          *
1225          * @param $table String|Array Table name
1226          * @param $vars String|Array Field names
1227          * @param $conds String|Array Conditions
1228          * @param $fname String Caller function name
1229          * @param $options Array Query options
1230          * @param $join_conds Array Join conditions
1231          *
1232          * @param $table string|array
1233          *
1234          * May be either an array of table names, or a single string holding a table
1235          * name. If an array is given, table aliases can be specified, for example:
1236          *
1237          *    array( 'a' => 'user' )
1238          *
1239          * This includes the user table in the query, with the alias "a" available
1240          * for use in field names (e.g. a.user_name).
1241          *
1242          * All of the table names given here are automatically run through
1243          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1244          * added, and various other table name mappings to be performed.
1245          *
1246          *
1247          * @param $vars string|array
1248          *
1249          * May be either a field name or an array of field names. The field names
1250          * here are complete fragments of SQL, for direct inclusion into the SELECT
1251          * query. Expressions and aliases may be specified as in SQL, for example:
1252          *
1253          *   array( 'MAX(rev_id) AS maxrev' )
1254          *
1255          * If an expression is given, care must be taken to ensure that it is
1256          * DBMS-independent.
1257          *
1258          *
1259          * @param $conds string|array
1260          *
1261          * May be either a string containing a single condition, or an array of
1262          * conditions. If an array is given, the conditions constructed from each
1263          * element are combined with AND.
1264          *
1265          * Array elements may take one of two forms:
1266          *
1267          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1268          *   - Elements with a string key are interpreted as equality conditions,
1269          *     where the key is the field name.
1270          *     - If the value of such an array element is a scalar (such as a
1271          *       string), it will be treated as data and thus quoted appropriately.
1272          *       If it is null, an IS NULL clause will be added.
1273          *     - If the value is an array, an IN(...) clause will be constructed,
1274          *       such that the field name may match any of the elements in the
1275          *       array. The elements of the array will be quoted.
1276          *
1277          * Note that expressions are often DBMS-dependent in their syntax.
1278          * DBMS-independent wrappers are provided for constructing several types of
1279          * expression commonly used in condition queries. See:
1280          *    - DatabaseBase::buildLike()
1281          *    - DatabaseBase::conditional()
1282          *
1283          *
1284          * @param $options string|array
1285          *
1286          * Optional: Array of query options. Boolean options are specified by
1287          * including them in the array as a string value with a numeric key, for
1288          * example:
1289          *
1290          *    array( 'FOR UPDATE' )
1291          *
1292          * The supported options are:
1293          *
1294          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1295          *     with LIMIT can theoretically be used for paging through a result set,
1296          *     but this is discouraged in MediaWiki for performance reasons.
1297          *
1298          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1299          *     and then the first rows are taken until the limit is reached. LIMIT
1300          *     is applied to a result set after OFFSET.
1301          *
1302          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1303          *     changed until the next COMMIT.
1304          *
1305          *   - DISTINCT: Boolean: return only unique result rows.
1306          *
1307          *   - GROUP BY: May be either an SQL fragment string naming a field or
1308          *     expression to group by, or an array of such SQL fragments.
1309          *
1310          *   - HAVING: A string containing a HAVING clause.
1311          *
1312          *   - ORDER BY: May be either an SQL fragment giving a field name or
1313          *     expression to order by, or an array of such SQL fragments.
1314          *
1315          *   - USE INDEX: This may be either a string giving the index name to use
1316          *     for the query, or an array. If it is an associative array, each key
1317          *     gives the table name (or alias), each value gives the index name to
1318          *     use for that table. All strings are SQL fragments and so should be
1319          *     validated by the caller.
1320          *
1321          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1322          *     instead of SELECT.
1323          *
1324          * And also the following boolean MySQL extensions, see the MySQL manual
1325          * for documentation:
1326          *
1327          *    - LOCK IN SHARE MODE
1328          *    - STRAIGHT_JOIN
1329          *    - HIGH_PRIORITY
1330          *    - SQL_BIG_RESULT
1331          *    - SQL_BUFFER_RESULT
1332          *    - SQL_SMALL_RESULT
1333          *    - SQL_CALC_FOUND_ROWS
1334          *    - SQL_CACHE
1335          *    - SQL_NO_CACHE
1336          *
1337          *
1338          * @param $join_conds string|array
1339          *
1340          * Optional associative array of table-specific join conditions. In the
1341          * most common case, this is unnecessary, since the join condition can be
1342          * in $conds. However, it is useful for doing a LEFT JOIN.
1343          *
1344          * The key of the array contains the table name or alias. The value is an
1345          * array with two elements, numbered 0 and 1. The first gives the type of
1346          * join, the second is an SQL fragment giving the join condition for that
1347          * table. For example:
1348          *
1349          *    array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
1350          *
1351          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1352          *   with no rows in it will be returned. If there was a query error, a
1353          *   DBQueryError exception will be thrown, except if the "ignore errors"
1354          *   option was set, in which case false will be returned.
1355          */
1356         function select( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1357                 $options = array(), $join_conds = array() ) {
1358                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1359
1360                 return $this->query( $sql, $fname );
1361         }
1362
1363         /**
1364          * The equivalent of DatabaseBase::select() except that the constructed SQL
1365          * is returned, instead of being immediately executed.
1366          *
1367          * @param $table string|array Table name
1368          * @param $vars string|array Field names
1369          * @param $conds string|array Conditions
1370          * @param $fname string Caller function name
1371          * @param $options string|array Query options
1372          * @param $join_conds string|array Join conditions
1373          *
1374          * @return SQL query string.
1375          * @see DatabaseBase::select()
1376          */
1377         function selectSQLText( $table, $vars, $conds = '', $fname = 'DatabaseBase::select', $options = array(), $join_conds = array() ) {
1378                 if ( is_array( $vars ) ) {
1379                         $vars = implode( ',', $vars );
1380                 }
1381
1382                 $options = (array)$options;
1383
1384                 if ( is_array( $table ) ) {
1385                         $useIndex = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1386                                 ? $options['USE INDEX']
1387                                 : array();
1388                         if ( count( $join_conds ) || count( $useIndex ) ) {
1389                                 $from = ' FROM ' .
1390                                         $this->tableNamesWithUseIndexOrJOIN( $table, $useIndex, $join_conds );
1391                         } else {
1392                                 $from = ' FROM ' . implode( ',', $this->tableNamesWithAlias( $table ) );
1393                         }
1394                 } elseif ( $table != '' ) {
1395                         if ( $table[0] == ' ' ) {
1396                                 $from = ' FROM ' . $table;
1397                         } else {
1398                                 $from = ' FROM ' . $this->tableName( $table );
1399                         }
1400                 } else {
1401                         $from = '';
1402                 }
1403
1404                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) = $this->makeSelectOptions( $options );
1405
1406                 if ( !empty( $conds ) ) {
1407                         if ( is_array( $conds ) ) {
1408                                 $conds = $this->makeList( $conds, LIST_AND );
1409                         }
1410                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1411                 } else {
1412                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1413                 }
1414
1415                 if ( isset( $options['LIMIT'] ) ) {
1416                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1417                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1418                 }
1419                 $sql = "$sql $postLimitTail";
1420
1421                 if ( isset( $options['EXPLAIN'] ) ) {
1422                         $sql = 'EXPLAIN ' . $sql;
1423                 }
1424
1425                 return $sql;
1426         }
1427
1428         /**
1429          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1430          * that a single row object is returned. If the query returns no rows,
1431          * false is returned.
1432          *
1433          * @param $table string|array Table name
1434          * @param $vars string|array Field names
1435          * @param $conds|array Conditions
1436          * @param $fname string Caller function name
1437          * @param $options string|array Query options
1438          * @param $join_conds array|string Join conditions
1439          *
1440          * @return ResultWrapper|bool
1441          */
1442         function selectRow( $table, $vars, $conds, $fname = 'DatabaseBase::selectRow',
1443                 $options = array(), $join_conds = array() )
1444         {
1445                 $options['LIMIT'] = 1;
1446                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1447
1448                 if ( $res === false ) {
1449                         return false;
1450                 }
1451
1452                 if ( !$this->numRows( $res ) ) {
1453                         return false;
1454                 }
1455
1456                 $obj = $this->fetchObject( $res );
1457
1458                 return $obj;
1459         }
1460
1461         /**
1462          * Estimate rows in dataset.
1463          *
1464          * MySQL allows you to estimate the number of rows that would be returned
1465          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1466          * index cardinality statistics, and is notoriously inaccurate, especially
1467          * when large numbers of rows have recently been added or deleted.
1468          *
1469          * For DBMSs that don't support fast result size estimation, this function
1470          * will actually perform the SELECT COUNT(*).
1471          *
1472          * Takes the same arguments as DatabaseBase::select().
1473          *
1474          * @param $table String: table name
1475          * @param Array|string $vars : unused
1476          * @param Array|string $conds : filters on the table
1477          * @param $fname String: function name for profiling
1478          * @param $options Array: options for select
1479          * @return Integer: row count
1480          */
1481         public function estimateRowCount( $table, $vars = '*', $conds = '',
1482                 $fname = 'DatabaseBase::estimateRowCount', $options = array() )
1483         {
1484                 $rows = 0;
1485                 $res = $this->select ( $table, 'COUNT(*) AS rowcount', $conds, $fname, $options );
1486
1487                 if ( $res ) {
1488                         $row = $this->fetchRow( $res );
1489                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1490                 }
1491
1492                 return $rows;
1493         }
1494
1495         /**
1496          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1497          * It's only slightly flawed. Don't use for anything important.
1498          *
1499          * @param $sql String A SQL Query
1500          *
1501          * @return string
1502          */
1503         static function generalizeSQL( $sql ) {
1504                 # This does the same as the regexp below would do, but in such a way
1505                 # as to avoid crashing php on some large strings.
1506                 # $sql = preg_replace ( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql);
1507
1508                 $sql = str_replace ( "\\\\", '', $sql );
1509                 $sql = str_replace ( "\\'", '', $sql );
1510                 $sql = str_replace ( "\\\"", '', $sql );
1511                 $sql = preg_replace ( "/'.*'/s", "'X'", $sql );
1512                 $sql = preg_replace ( '/".*"/s', "'X'", $sql );
1513
1514                 # All newlines, tabs, etc replaced by single space
1515                 $sql = preg_replace ( '/\s+/', ' ', $sql );
1516
1517                 # All numbers => N
1518                 $sql = preg_replace ( '/-?[0-9]+/s', 'N', $sql );
1519
1520                 return $sql;
1521         }
1522
1523         /**
1524          * Determines whether a field exists in a table
1525          *
1526          * @param $table String: table name
1527          * @param $field String: filed to check on that table
1528          * @param $fname String: calling function name (optional)
1529          * @return Boolean: whether $table has filed $field
1530          */
1531         function fieldExists( $table, $field, $fname = 'DatabaseBase::fieldExists' ) {
1532                 $info = $this->fieldInfo( $table, $field );
1533
1534                 return (bool)$info;
1535         }
1536
1537         /**
1538          * Determines whether an index exists
1539          * Usually throws a DBQueryError on failure
1540          * If errors are explicitly ignored, returns NULL on failure
1541          *
1542          * @param $table
1543          * @param $index
1544          * @param $fname string
1545          *
1546          * @return bool|null
1547          */
1548         function indexExists( $table, $index, $fname = 'DatabaseBase::indexExists' ) {
1549                 $info = $this->indexInfo( $table, $index, $fname );
1550                 if ( is_null( $info ) ) {
1551                         return null;
1552                 } else {
1553                         return $info !== false;
1554                 }
1555         }
1556
1557         /**
1558          * Query whether a given table exists
1559          *
1560          * @param $table string
1561          * @param $fname string
1562          *
1563          * @return bool
1564          */
1565         function tableExists( $table, $fname = __METHOD__ ) {
1566                 $table = $this->tableName( $table );
1567                 $old = $this->ignoreErrors( true );
1568                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1569                 $this->ignoreErrors( $old );
1570
1571                 return (bool)$res;
1572         }
1573
1574         /**
1575          * mysql_field_type() wrapper
1576          * @param $res
1577          * @param $index
1578          * @return string
1579          */
1580         function fieldType( $res, $index ) {
1581                 if ( $res instanceof ResultWrapper ) {
1582                         $res = $res->result;
1583                 }
1584
1585                 return mysql_field_type( $res, $index );
1586         }
1587
1588         /**
1589          * Determines if a given index is unique
1590          *
1591          * @param $table string
1592          * @param $index string
1593          *
1594          * @return bool
1595          */
1596         function indexUnique( $table, $index ) {
1597                 $indexInfo = $this->indexInfo( $table, $index );
1598
1599                 if ( !$indexInfo ) {
1600                         return null;
1601                 }
1602
1603                 return !$indexInfo[0]->Non_unique;
1604         }
1605
1606         /**
1607          * Helper for DatabaseBase::insert().
1608          *
1609          * @param $options array
1610          * @return string
1611          */
1612         function makeInsertOptions( $options ) {
1613                 return implode( ' ', $options );
1614         }
1615
1616         /**
1617          * INSERT wrapper, inserts an array into a table.
1618          *
1619          * $a may be either:
1620          *
1621          *   - A single associative array. The array keys are the field names, and
1622          *     the values are the values to insert. The values are treated as data
1623          *     and will be quoted appropriately. If NULL is inserted, this will be
1624          *     converted to a database NULL.
1625          *   - An array with numeric keys, holding a list of associative arrays.
1626          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1627          *     each subarray must be identical to each other, and in the same order.
1628          *
1629          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1630          * returns success.
1631          *
1632          * $options is an array of options, with boolean options encoded as values
1633          * with numeric keys, in the same style as $options in
1634          * DatabaseBase::select(). Supported options are:
1635          *
1636          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1637          *     any rows which cause duplicate key errors are not inserted. It's
1638          *     possible to determine how many rows were successfully inserted using
1639          *     DatabaseBase::affectedRows().
1640          *
1641          * @param $table   String Table name. This will be passed through
1642          *                 DatabaseBase::tableName().
1643          * @param $a       Array of rows to insert
1644          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1645          * @param $options Array of options
1646          *
1647          * @return bool
1648          */
1649         function insert( $table, $a, $fname = 'DatabaseBase::insert', $options = array() ) {
1650                 # No rows to insert, easy just return now
1651                 if ( !count( $a ) ) {
1652                         return true;
1653                 }
1654
1655                 $table = $this->tableName( $table );
1656
1657                 if ( !is_array( $options ) ) {
1658                         $options = array( $options );
1659                 }
1660
1661                 $options = $this->makeInsertOptions( $options );
1662
1663                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1664                         $multi = true;
1665                         $keys = array_keys( $a[0] );
1666                 } else {
1667                         $multi = false;
1668                         $keys = array_keys( $a );
1669                 }
1670
1671                 $sql = 'INSERT ' . $options .
1672                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1673
1674                 if ( $multi ) {
1675                         $first = true;
1676                         foreach ( $a as $row ) {
1677                                 if ( $first ) {
1678                                         $first = false;
1679                                 } else {
1680                                         $sql .= ',';
1681                                 }
1682                                 $sql .= '(' . $this->makeList( $row ) . ')';
1683                         }
1684                 } else {
1685                         $sql .= '(' . $this->makeList( $a ) . ')';
1686                 }
1687
1688                 return (bool)$this->query( $sql, $fname );
1689         }
1690
1691         /**
1692          * Make UPDATE options for the DatabaseBase::update function
1693          *
1694          * @param $options Array: The options passed to DatabaseBase::update
1695          * @return string
1696          */
1697         function makeUpdateOptions( $options ) {
1698                 if ( !is_array( $options ) ) {
1699                         $options = array( $options );
1700                 }
1701
1702                 $opts = array();
1703
1704                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1705                         $opts[] = $this->lowPriorityOption();
1706                 }
1707
1708                 if ( in_array( 'IGNORE', $options ) ) {
1709                         $opts[] = 'IGNORE';
1710                 }
1711
1712                 return implode( ' ', $opts );
1713         }
1714
1715         /**
1716          * UPDATE wrapper. Takes a condition array and a SET array.
1717          *
1718          * @param $table  String name of the table to UPDATE. This will be passed through
1719          *                DatabaseBase::tableName().
1720          *
1721          * @param $values Array:  An array of values to SET. For each array element,
1722          *                the key gives the field name, and the value gives the data
1723          *                to set that field to. The data will be quoted by
1724          *                DatabaseBase::addQuotes().
1725          *
1726          * @param $conds  Array:  An array of conditions (WHERE). See
1727          *                DatabaseBase::select() for the details of the format of
1728          *                condition arrays. Use '*' to update all rows.
1729          *
1730          * @param $fname  String: The function name of the caller (from __METHOD__),
1731          *                for logging and profiling.
1732          *
1733          * @param $options Array: An array of UPDATE options, can be:
1734          *                   - IGNORE: Ignore unique key conflicts
1735          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1736          * @return Boolean
1737          */
1738         function update( $table, $values, $conds, $fname = 'DatabaseBase::update', $options = array() ) {
1739                 $table = $this->tableName( $table );
1740                 $opts = $this->makeUpdateOptions( $options );
1741                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1742
1743                 if ( $conds !== array() && $conds !== '*' ) {
1744                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1745                 }
1746
1747                 return $this->query( $sql, $fname );
1748         }
1749
1750         /**
1751          * Makes an encoded list of strings from an array
1752          * @param $a Array containing the data
1753          * @param $mode int Constant
1754          *      - LIST_COMMA:          comma separated, no field names
1755          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1756          *        the documentation for $conds in DatabaseBase::select().
1757          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1758          *      - LIST_SET:            comma separated with field names, like a SET clause
1759          *      - LIST_NAMES:          comma separated field names
1760          *
1761          * @return string
1762          */
1763         function makeList( $a, $mode = LIST_COMMA ) {
1764                 if ( !is_array( $a ) ) {
1765                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1766                 }
1767
1768                 $first = true;
1769                 $list = '';
1770
1771                 foreach ( $a as $field => $value ) {
1772                         if ( !$first ) {
1773                                 if ( $mode == LIST_AND ) {
1774                                         $list .= ' AND ';
1775                                 } elseif ( $mode == LIST_OR ) {
1776                                         $list .= ' OR ';
1777                                 } else {
1778                                         $list .= ',';
1779                                 }
1780                         } else {
1781                                 $first = false;
1782                         }
1783
1784                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1785                                 $list .= "($value)";
1786                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1787                                 $list .= "$value";
1788                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1789                                 if ( count( $value ) == 0 ) {
1790                                         throw new MWException( __METHOD__ . ': empty input' );
1791                                 } elseif ( count( $value ) == 1 ) {
1792                                         // Special-case single values, as IN isn't terribly efficient
1793                                         // Don't necessarily assume the single key is 0; we don't
1794                                         // enforce linear numeric ordering on other arrays here.
1795                                         $value = array_values( $value );
1796                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1797                                 } else {
1798                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1799                                 }
1800                         } elseif ( $value === null ) {
1801                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1802                                         $list .= "$field IS ";
1803                                 } elseif ( $mode == LIST_SET ) {
1804                                         $list .= "$field = ";
1805                                 }
1806                                 $list .= 'NULL';
1807                         } else {
1808                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1809                                         $list .= "$field = ";
1810                                 }
1811                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1812                         }
1813                 }
1814
1815                 return $list;
1816         }
1817
1818         /**
1819          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1820          * The keys on each level may be either integers or strings.
1821          *
1822          * @param $data Array: organized as 2-d
1823          *              array(baseKeyVal => array(subKeyVal => <ignored>, ...), ...)
1824          * @param $baseKey String: field name to match the base-level keys to (eg 'pl_namespace')
1825          * @param $subKey String: field name to match the sub-level keys to (eg 'pl_title')
1826          * @return Mixed: string SQL fragment, or false if no items in array.
1827          */
1828         function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1829                 $conds = array();
1830
1831                 foreach ( $data as $base => $sub ) {
1832                         if ( count( $sub ) ) {
1833                                 $conds[] = $this->makeList(
1834                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1835                                         LIST_AND );
1836                         }
1837                 }
1838
1839                 if ( $conds ) {
1840                         return $this->makeList( $conds, LIST_OR );
1841                 } else {
1842                         // Nothing to search for...
1843                         return false;
1844                 }
1845         }
1846
1847         /**
1848          * Bitwise operations
1849          */
1850
1851         /**
1852          * @param $field
1853          * @return string
1854          */
1855         function bitNot( $field ) {
1856                 return "(~$field)";
1857         }
1858
1859         /**
1860          * @param $fieldLeft
1861          * @param $fieldRight
1862          * @return string
1863          */
1864         function bitAnd( $fieldLeft, $fieldRight ) {
1865                 return "($fieldLeft & $fieldRight)";
1866         }
1867
1868         /**
1869          * @param  $fieldLeft
1870          * @param  $fieldRight
1871          * @return string
1872          */
1873         function bitOr( $fieldLeft, $fieldRight ) {
1874                 return "($fieldLeft | $fieldRight)";
1875         }
1876
1877         /**
1878          * Change the current database
1879          *
1880          * @todo Explain what exactly will fail if this is not overridden.
1881          *
1882          * @param $db
1883          *
1884          * @return bool Success or failure
1885          */
1886         function selectDB( $db ) {
1887                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
1888                 # if your database engine supports a concept similar to MySQL's
1889                 # databases you may as well.
1890                 $this->mDBname = $db;
1891                 return true;
1892         }
1893
1894         /**
1895          * Get the current DB name
1896          */
1897         function getDBname() {
1898                 return $this->mDBname;
1899         }
1900
1901         /**
1902          * Get the server hostname or IP address
1903          */
1904         function getServer() {
1905                 return $this->mServer;
1906         }
1907
1908         /**
1909          * Format a table name ready for use in constructing an SQL query
1910          *
1911          * This does two important things: it quotes the table names to clean them up,
1912          * and it adds a table prefix if only given a table name with no quotes.
1913          *
1914          * All functions of this object which require a table name call this function
1915          * themselves. Pass the canonical name to such functions. This is only needed
1916          * when calling query() directly.
1917          *
1918          * @param $name String: database table name
1919          * @param $format String One of:
1920          *   quoted - Automatically pass the table name through addIdentifierQuotes()
1921          *            so that it can be used in a query.
1922          *   raw - Do not add identifier quotes to the table name
1923          * @return String: full database name
1924          */
1925         function tableName( $name, $format = 'quoted' ) {
1926                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
1927                 # Skip the entire process when we have a string quoted on both ends.
1928                 # Note that we check the end so that we will still quote any use of
1929                 # use of `database`.table. But won't break things if someone wants
1930                 # to query a database table with a dot in the name.
1931                 if ( $this->isQuotedIdentifier( $name ) ) {
1932                         return $name;
1933                 }
1934
1935                 # Lets test for any bits of text that should never show up in a table
1936                 # name. Basically anything like JOIN or ON which are actually part of
1937                 # SQL queries, but may end up inside of the table value to combine
1938                 # sql. Such as how the API is doing.
1939                 # Note that we use a whitespace test rather than a \b test to avoid
1940                 # any remote case where a word like on may be inside of a table name
1941                 # surrounded by symbols which may be considered word breaks.
1942                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1943                         return $name;
1944                 }
1945
1946                 # Split database and table into proper variables.
1947                 # We reverse the explode so that database.table and table both output
1948                 # the correct table.
1949                 $dbDetails = array_reverse( explode( '.', $name, 2 ) );
1950                 if ( isset( $dbDetails[1] ) ) {
1951                         list( $table, $database ) = $dbDetails;
1952                 } else {
1953                         list( $table ) = $dbDetails;
1954                 }
1955                 $prefix = $this->mTablePrefix; # Default prefix
1956
1957                 # A database name has been specified in input. We don't want any
1958                 # prefixes added.
1959                 if ( isset( $database ) ) {
1960                         $prefix = '';
1961                 }
1962
1963                 # Note that we use the long format because php will complain in in_array if
1964                 # the input is not an array, and will complain in is_array if it is not set.
1965                 if ( !isset( $database ) # Don't use shared database if pre selected.
1966                  && isset( $wgSharedDB ) # We have a shared database
1967                  && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
1968                  && isset( $wgSharedTables )
1969                  && is_array( $wgSharedTables )
1970                  && in_array( $table, $wgSharedTables ) ) { # A shared table is selected
1971                         $database = $wgSharedDB;
1972                         $prefix   = isset( $wgSharedPrefix ) ? $wgSharedPrefix : $prefix;
1973                 }
1974
1975                 # Quote the $database and $table and apply the prefix if not quoted.
1976                 if ( isset( $database ) ) {
1977                         $database = ( $format == 'quoted' || $this->isQuotedIdentifier( $database ) ? $database : $this->addIdentifierQuotes( $database ) );
1978                 }
1979
1980                 $table = "{$prefix}{$table}";
1981                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $table ) ) {
1982                         $table = $this->addIdentifierQuotes( "{$table}" );
1983                 }
1984
1985                 # Merge our database and table into our final table name.
1986                 $tableName = ( isset( $database ) ? "{$database}.{$table}" : "{$table}" );
1987
1988                 return $tableName;
1989         }
1990
1991         /**
1992          * Fetch a number of table names into an array
1993          * This is handy when you need to construct SQL for joins
1994          *
1995          * Example:
1996          * extract($dbr->tableNames('user','watchlist'));
1997          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
1998          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
1999          *
2000          * @return array
2001          */
2002         public function tableNames() {
2003                 $inArray = func_get_args();
2004                 $retVal = array();
2005
2006                 foreach ( $inArray as $name ) {
2007                         $retVal[$name] = $this->tableName( $name );
2008                 }
2009
2010                 return $retVal;
2011         }
2012
2013         /**
2014          * Fetch a number of table names into an zero-indexed numerical array
2015          * This is handy when you need to construct SQL for joins
2016          *
2017          * Example:
2018          * list( $user, $watchlist ) = $dbr->tableNamesN('user','watchlist');
2019          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2020          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2021          *
2022          * @return array
2023          */
2024         public function tableNamesN() {
2025                 $inArray = func_get_args();
2026                 $retVal = array();
2027
2028                 foreach ( $inArray as $name ) {
2029                         $retVal[] = $this->tableName( $name );
2030                 }
2031
2032                 return $retVal;
2033         }
2034
2035         /**
2036          * Get an aliased table name
2037          * e.g. tableName AS newTableName
2038          *
2039          * @param $name string Table name, see tableName()
2040          * @param $alias string|bool Alias (optional)
2041          * @return string SQL name for aliased table. Will not alias a table to its own name
2042          */
2043         public function tableNameWithAlias( $name, $alias = false ) {
2044                 if ( !$alias || $alias == $name ) {
2045                         return $this->tableName( $name );
2046                 } else {
2047                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2048                 }
2049         }
2050
2051         /**
2052          * Gets an array of aliased table names
2053          *
2054          * @param $tables array( [alias] => table )
2055          * @return array of strings, see tableNameWithAlias()
2056          */
2057         public function tableNamesWithAlias( $tables ) {
2058                 $retval = array();
2059                 foreach ( $tables as $alias => $table ) {
2060                         if ( is_numeric( $alias ) ) {
2061                                 $alias = $table;
2062                         }
2063                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2064                 }
2065                 return $retval;
2066         }
2067
2068         /**
2069          * Get the aliased table name clause for a FROM clause
2070          * which might have a JOIN and/or USE INDEX clause
2071          *
2072          * @param $tables array ( [alias] => table )
2073          * @param $use_index array Same as for select()
2074          * @param $join_conds array Same as for select()
2075          * @return string
2076          */
2077         protected function tableNamesWithUseIndexOrJOIN(
2078                 $tables, $use_index = array(), $join_conds = array()
2079         ) {
2080                 $ret = array();
2081                 $retJOIN = array();
2082                 $use_index = (array)$use_index;
2083                 $join_conds = (array)$join_conds;
2084
2085                 foreach ( $tables as $alias => $table ) {
2086                         if ( !is_string( $alias ) ) {
2087                                 // No alias? Set it equal to the table name
2088                                 $alias = $table;
2089                         }
2090                         // Is there a JOIN clause for this table?
2091                         if ( isset( $join_conds[$alias] ) ) {
2092                                 list( $joinType, $conds ) = $join_conds[$alias];
2093                                 $tableClause = $joinType;
2094                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2095                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2096                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2097                                         if ( $use != '' ) {
2098                                                 $tableClause .= ' ' . $use;
2099                                         }
2100                                 }
2101                                 $on = $this->makeList( (array)$conds, LIST_AND );
2102                                 if ( $on != '' ) {
2103                                         $tableClause .= ' ON (' . $on . ')';
2104                                 }
2105
2106                                 $retJOIN[] = $tableClause;
2107                         // Is there an INDEX clause for this table?
2108                         } elseif ( isset( $use_index[$alias] ) ) {
2109                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2110                                 $tableClause .= ' ' . $this->useIndexClause(
2111                                         implode( ',', (array)$use_index[$alias] ) );
2112
2113                                 $ret[] = $tableClause;
2114                         } else {
2115                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2116
2117                                 $ret[] = $tableClause;
2118                         }
2119                 }
2120
2121                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2122                 $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2123                 $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2124
2125                 // Compile our final table clause
2126                 return implode( ' ', array( $straightJoins, $otherJoins ) );
2127         }
2128
2129         /**
2130          * Get the name of an index in a given table
2131          *
2132          * @param $index
2133          *
2134          * @return string
2135          */
2136         function indexName( $index ) {
2137                 // Backwards-compatibility hack
2138                 $renamed = array(
2139                         'ar_usertext_timestamp' => 'usertext_timestamp',
2140                         'un_user_id'            => 'user_id',
2141                         'un_user_ip'            => 'user_ip',
2142                 );
2143
2144                 if ( isset( $renamed[$index] ) ) {
2145                         return $renamed[$index];
2146                 } else {
2147                         return $index;
2148                 }
2149         }
2150
2151         /**
2152          * If it's a string, adds quotes and backslashes
2153          * Otherwise returns as-is
2154          *
2155          * @param $s string
2156          *
2157          * @return string
2158          */
2159         function addQuotes( $s ) {
2160                 if ( $s === null ) {
2161                         return 'NULL';
2162                 } else {
2163                         # This will also quote numeric values. This should be harmless,
2164                         # and protects against weird problems that occur when they really
2165                         # _are_ strings such as article titles and string->number->string
2166                         # conversion is not 1:1.
2167                         return "'" . $this->strencode( $s ) . "'";
2168                 }
2169         }
2170
2171         /**
2172          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2173          * MySQL uses `backticks` while basically everything else uses double quotes.
2174          * Since MySQL is the odd one out here the double quotes are our generic
2175          * and we implement backticks in DatabaseMysql.
2176          *
2177          * @param $s string
2178          *
2179          * @return string
2180          */
2181         public function addIdentifierQuotes( $s ) {
2182                 return '"' . str_replace( '"', '""', $s ) . '"';
2183         }
2184
2185         /**
2186          * Returns if the given identifier looks quoted or not according to
2187          * the database convention for quoting identifiers .
2188          *
2189          * @param $name string
2190          *
2191          * @return boolean
2192          */
2193         public function isQuotedIdentifier( $name ) {
2194                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2195         }
2196
2197         /**
2198          * Backwards compatibility, identifier quoting originated in DatabasePostgres
2199          * which used quote_ident which does not follow our naming conventions
2200          * was renamed to addIdentifierQuotes.
2201          * @deprecated since 1.18 use addIdentifierQuotes
2202          *
2203          * @param $s string
2204          *
2205          * @return string
2206          */
2207         function quote_ident( $s ) {
2208                 wfDeprecated( __METHOD__, '1.18' );
2209                 return $this->addIdentifierQuotes( $s );
2210         }
2211
2212         /**
2213          * Escape string for safe LIKE usage.
2214          * WARNING: you should almost never use this function directly,
2215          * instead use buildLike() that escapes everything automatically
2216          * @deprecated since 1.17, warnings in 1.17, removed in ???
2217          *
2218          * @param $s string
2219          *
2220          * @return string
2221          */
2222         public function escapeLike( $s ) {
2223                 wfDeprecated( __METHOD__, '1.17' );
2224                 return $this->escapeLikeInternal( $s );
2225         }
2226
2227         /**
2228          * @param $s string
2229          * @return string
2230          */
2231         protected function escapeLikeInternal( $s ) {
2232                 $s = str_replace( '\\', '\\\\', $s );
2233                 $s = $this->strencode( $s );
2234                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2235
2236                 return $s;
2237         }
2238
2239         /**
2240          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2241          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2242          * Alternatively, the function could be provided with an array of aforementioned parameters.
2243          *
2244          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2245          * for subpages of 'My page title'.
2246          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2247          *
2248          * @since 1.16
2249          * @return String: fully built LIKE statement
2250          */
2251         function buildLike() {
2252                 $params = func_get_args();
2253
2254                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2255                         $params = $params[0];
2256                 }
2257
2258                 $s = '';
2259
2260                 foreach ( $params as $value ) {
2261                         if ( $value instanceof LikeMatch ) {
2262                                 $s .= $value->toString();
2263                         } else {
2264                                 $s .= $this->escapeLikeInternal( $value );
2265                         }
2266                 }
2267
2268                 return " LIKE '" . $s . "' ";
2269         }
2270
2271         /**
2272          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2273          *
2274          * @return LikeMatch
2275          */
2276         function anyChar() {
2277                 return new LikeMatch( '_' );
2278         }
2279
2280         /**
2281          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2282          *
2283          * @return LikeMatch
2284          */
2285         function anyString() {
2286                 return new LikeMatch( '%' );
2287         }
2288
2289         /**
2290          * Returns an appropriately quoted sequence value for inserting a new row.
2291          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2292          * subclass will return an integer, and save the value for insertId()
2293          *
2294          * Any implementation of this function should *not* involve reusing
2295          * sequence numbers created for rolled-back transactions.
2296          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2297          * @param $seqName string
2298          * @return null
2299          */
2300         function nextSequenceValue( $seqName ) {
2301                 return null;
2302         }
2303
2304         /**
2305          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2306          * is only needed because a) MySQL must be as efficient as possible due to
2307          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2308          * which index to pick.  Anyway, other databases might have different
2309          * indexes on a given table.  So don't bother overriding this unless you're
2310          * MySQL.
2311          * @param $index
2312          * @return string
2313          */
2314         function useIndexClause( $index ) {
2315                 return '';
2316         }
2317
2318         /**
2319          * REPLACE query wrapper.
2320          *
2321          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2322          * except that when there is a duplicate key error, the old row is deleted
2323          * and the new row is inserted in its place.
2324          *
2325          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2326          * perform the delete, we need to know what the unique indexes are so that
2327          * we know how to find the conflicting rows.
2328          *
2329          * It may be more efficient to leave off unique indexes which are unlikely
2330          * to collide. However if you do this, you run the risk of encountering
2331          * errors which wouldn't have occurred in MySQL.
2332          *
2333          * @param $table String: The table to replace the row(s) in.
2334          * @param $rows array Can be either a single row to insert, or multiple rows,
2335          *    in the same format as for DatabaseBase::insert()
2336          * @param $uniqueIndexes array is an array of indexes. Each element may be either
2337          *    a field name or an array of field names
2338          * @param $fname String: Calling function name (use __METHOD__) for logs/profiling
2339          */
2340         function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseBase::replace' ) {
2341                 $quotedTable = $this->tableName( $table );
2342
2343                 if ( count( $rows ) == 0 ) {
2344                         return;
2345                 }
2346
2347                 # Single row case
2348                 if ( !is_array( reset( $rows ) ) ) {
2349                         $rows = array( $rows );
2350                 }
2351
2352                 foreach( $rows as $row ) {
2353                         # Delete rows which collide
2354                         if ( $uniqueIndexes ) {
2355                                 $sql = "DELETE FROM $quotedTable WHERE ";
2356                                 $first = true;
2357                                 foreach ( $uniqueIndexes as $index ) {
2358                                         if ( $first ) {
2359                                                 $first = false;
2360                                                 $sql .= '( ';
2361                                         } else {
2362                                                 $sql .= ' ) OR ( ';
2363                                         }
2364                                         if ( is_array( $index ) ) {
2365                                                 $first2 = true;
2366                                                 foreach ( $index as $col ) {
2367                                                         if ( $first2 ) {
2368                                                                 $first2 = false;
2369                                                         } else {
2370                                                                 $sql .= ' AND ';
2371                                                         }
2372                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2373                                                 }
2374                                         } else {
2375                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2376                                         }
2377                                 }
2378                                 $sql .= ' )';
2379                                 $this->query( $sql, $fname );
2380                         }
2381
2382                         # Now insert the row
2383                         $this->insert( $table, $row );
2384                 }
2385         }
2386
2387         /**
2388          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2389          * statement.
2390          *
2391          * @param $table string Table name
2392          * @param $rows array Rows to insert
2393          * @param $fname string Caller function name
2394          *
2395          * @return ResultWrapper
2396          */
2397         protected function nativeReplace( $table, $rows, $fname ) {
2398                 $table = $this->tableName( $table );
2399
2400                 # Single row case
2401                 if ( !is_array( reset( $rows ) ) ) {
2402                         $rows = array( $rows );
2403                 }
2404
2405                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2406                 $first = true;
2407
2408                 foreach ( $rows as $row ) {
2409                         if ( $first ) {
2410                                 $first = false;
2411                         } else {
2412                                 $sql .= ',';
2413                         }
2414
2415                         $sql .= '(' . $this->makeList( $row ) . ')';
2416                 }
2417
2418                 return $this->query( $sql, $fname );
2419         }
2420
2421         /**
2422          * DELETE where the condition is a join.
2423          *
2424          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2425          * we use sub-selects
2426          *
2427          * For safety, an empty $conds will not delete everything. If you want to
2428          * delete all rows where the join condition matches, set $conds='*'.
2429          *
2430          * DO NOT put the join condition in $conds.
2431          *
2432          * @param $delTable   String: The table to delete from.
2433          * @param $joinTable  String: The other table.
2434          * @param $delVar     String: The variable to join on, in the first table.
2435          * @param $joinVar    String: The variable to join on, in the second table.
2436          * @param $conds      Array: Condition array of field names mapped to variables,
2437          *                    ANDed together in the WHERE clause
2438          * @param $fname      String: Calling function name (use __METHOD__) for
2439          *                    logs/profiling
2440          */
2441         function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2442                 $fname = 'DatabaseBase::deleteJoin' )
2443         {
2444                 if ( !$conds ) {
2445                         throw new DBUnexpectedError( $this,
2446                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2447                 }
2448
2449                 $delTable = $this->tableName( $delTable );
2450                 $joinTable = $this->tableName( $joinTable );
2451                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2452                 if ( $conds != '*' ) {
2453                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2454                 }
2455                 $sql .= ')';
2456
2457                 $this->query( $sql, $fname );
2458         }
2459
2460         /**
2461          * Returns the size of a text field, or -1 for "unlimited"
2462          *
2463          * @param $table string
2464          * @param $field string
2465          *
2466          * @return int
2467          */
2468         function textFieldSize( $table, $field ) {
2469                 $table = $this->tableName( $table );
2470                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2471                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2472                 $row = $this->fetchObject( $res );
2473
2474                 $m = array();
2475
2476                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2477                         $size = $m[1];
2478                 } else {
2479                         $size = -1;
2480                 }
2481
2482                 return $size;
2483         }
2484
2485         /**
2486          * A string to insert into queries to show that they're low-priority, like
2487          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2488          * string and nothing bad should happen.
2489          *
2490          * @return string Returns the text of the low priority option if it is
2491          *   supported, or a blank string otherwise
2492          */
2493         function lowPriorityOption() {
2494                 return '';
2495         }
2496
2497         /**
2498          * DELETE query wrapper.
2499          *
2500          * @param $table Array Table name
2501          * @param $conds String|Array of conditions. See $conds in DatabaseBase::select() for
2502          *               the format. Use $conds == "*" to delete all rows
2503          * @param $fname String name of the calling function
2504          *
2505          * @return bool
2506          */
2507         function delete( $table, $conds, $fname = 'DatabaseBase::delete' ) {
2508                 if ( !$conds ) {
2509                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2510                 }
2511
2512                 $table = $this->tableName( $table );
2513                 $sql = "DELETE FROM $table";
2514
2515                 if ( $conds != '*' ) {
2516                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2517                 }
2518
2519                 return $this->query( $sql, $fname );
2520         }
2521
2522         /**
2523          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2524          * into another table.
2525          *
2526          * @param $destTable string The table name to insert into
2527          * @param $srcTable string|array May be either a table name, or an array of table names
2528          *    to include in a join.
2529          *
2530          * @param $varMap array must be an associative array of the form
2531          *    array( 'dest1' => 'source1', ...). Source items may be literals
2532          *    rather than field names, but strings should be quoted with
2533          *    DatabaseBase::addQuotes()
2534          *
2535          * @param $conds array Condition array. See $conds in DatabaseBase::select() for
2536          *    the details of the format of condition arrays. May be "*" to copy the
2537          *    whole table.
2538          *
2539          * @param $fname string The function name of the caller, from __METHOD__
2540          *
2541          * @param $insertOptions array Options for the INSERT part of the query, see
2542          *    DatabaseBase::insert() for details.
2543          * @param $selectOptions array Options for the SELECT part of the query, see
2544          *    DatabaseBase::select() for details.
2545          *
2546          * @return ResultWrapper
2547          */
2548         function insertSelect( $destTable, $srcTable, $varMap, $conds,
2549                 $fname = 'DatabaseBase::insertSelect',
2550                 $insertOptions = array(), $selectOptions = array() )
2551         {
2552                 $destTable = $this->tableName( $destTable );
2553
2554                 if ( is_array( $insertOptions ) ) {
2555                         $insertOptions = implode( ' ', $insertOptions );
2556                 }
2557
2558                 if ( !is_array( $selectOptions ) ) {
2559                         $selectOptions = array( $selectOptions );
2560                 }
2561
2562                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2563
2564                 if ( is_array( $srcTable ) ) {
2565                         $srcTable =  implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2566                 } else {
2567                         $srcTable = $this->tableName( $srcTable );
2568                 }
2569
2570                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2571                         " SELECT $startOpts " . implode( ',', $varMap ) .
2572                         " FROM $srcTable $useIndex ";
2573
2574                 if ( $conds != '*' ) {
2575                         if ( is_array( $conds ) ) {
2576                                 $conds = $this->makeList( $conds, LIST_AND );
2577                         }
2578                         $sql .= " WHERE $conds";
2579                 }
2580
2581                 $sql .= " $tailOpts";
2582
2583                 return $this->query( $sql, $fname );
2584         }
2585
2586         /**
2587          * Construct a LIMIT query with optional offset.  This is used for query
2588          * pages.  The SQL should be adjusted so that only the first $limit rows
2589          * are returned.  If $offset is provided as well, then the first $offset
2590          * rows should be discarded, and the next $limit rows should be returned.
2591          * If the result of the query is not ordered, then the rows to be returned
2592          * are theoretically arbitrary.
2593          *
2594          * $sql is expected to be a SELECT, if that makes a difference.  For
2595          * UPDATE, limitResultForUpdate should be used.
2596          *
2597          * The version provided by default works in MySQL and SQLite.  It will very
2598          * likely need to be overridden for most other DBMSes.
2599          *
2600          * @param $sql String SQL query we will append the limit too
2601          * @param $limit Integer the SQL limit
2602          * @param $offset Integer|false the SQL offset (default false)
2603          *
2604          * @return string
2605          */
2606         function limitResult( $sql, $limit, $offset = false ) {
2607                 if ( !is_numeric( $limit ) ) {
2608                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2609                 }
2610
2611                 return "$sql LIMIT "
2612                                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2613                                 . "{$limit} ";
2614         }
2615
2616         /**
2617          * @param $sql
2618          * @param $num
2619          * @return string
2620          */
2621         function limitResultForUpdate( $sql, $num ) {
2622                 return $this->limitResult( $sql, $num, 0 );
2623         }
2624
2625         /**
2626          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2627          * within the UNION construct.
2628          * @return Boolean
2629          */
2630         function unionSupportsOrderAndLimit() {
2631                 return true; // True for almost every DB supported
2632         }
2633
2634         /**
2635          * Construct a UNION query
2636          * This is used for providing overload point for other DB abstractions
2637          * not compatible with the MySQL syntax.
2638          * @param $sqls Array: SQL statements to combine
2639          * @param $all Boolean: use UNION ALL
2640          * @return String: SQL fragment
2641          */
2642         function unionQueries( $sqls, $all ) {
2643                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2644                 return '(' . implode( $glue, $sqls ) . ')';
2645         }
2646
2647         /**
2648          * Returns an SQL expression for a simple conditional.  This doesn't need
2649          * to be overridden unless CASE isn't supported in your DBMS.
2650          *
2651          * @param $cond String: SQL expression which will result in a boolean value
2652          * @param $trueVal String: SQL expression to return if true
2653          * @param $falseVal String: SQL expression to return if false
2654          * @return String: SQL fragment
2655          */
2656         function conditional( $cond, $trueVal, $falseVal ) {
2657                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2658         }
2659
2660         /**
2661          * Returns a comand for str_replace function in SQL query.
2662          * Uses REPLACE() in MySQL
2663          *
2664          * @param $orig String: column to modify
2665          * @param $old String: column to seek
2666          * @param $new String: column to replace with
2667          *
2668          * @return string
2669          */
2670         function strreplace( $orig, $old, $new ) {
2671                 return "REPLACE({$orig}, {$old}, {$new})";
2672         }
2673
2674         /**
2675          * Determines how long the server has been up
2676          * STUB
2677          *
2678          * @return int
2679          */
2680         function getServerUptime() {
2681                 return 0;
2682         }
2683
2684         /**
2685          * Determines if the last failure was due to a deadlock
2686          * STUB
2687          *
2688          * @return bool
2689          */
2690         function wasDeadlock() {
2691                 return false;
2692         }
2693
2694         /**
2695          * Determines if the last failure was due to a lock timeout
2696          * STUB
2697          *
2698          * @return bool
2699          */
2700         function wasLockTimeout() {
2701                 return false;
2702         }
2703
2704         /**
2705          * Determines if the last query error was something that should be dealt
2706          * with by pinging the connection and reissuing the query.
2707          * STUB
2708          *
2709          * @return bool
2710          */
2711         function wasErrorReissuable() {
2712                 return false;
2713         }
2714
2715         /**
2716          * Determines if the last failure was due to the database being read-only.
2717          * STUB
2718          *
2719          * @return bool
2720          */
2721         function wasReadOnlyError() {
2722                 return false;
2723         }
2724
2725         /**
2726          * Perform a deadlock-prone transaction.
2727          *
2728          * This function invokes a callback function to perform a set of write
2729          * queries. If a deadlock occurs during the processing, the transaction
2730          * will be rolled back and the callback function will be called again.
2731          *
2732          * Usage:
2733          *   $dbw->deadlockLoop( callback, ... );
2734          *
2735          * Extra arguments are passed through to the specified callback function.
2736          *
2737          * Returns whatever the callback function returned on its successful,
2738          * iteration, or false on error, for example if the retry limit was
2739          * reached.
2740          *
2741          * @return bool
2742          */
2743         function deadlockLoop() {
2744
2745                 $this->begin( __METHOD__ );
2746                 $args = func_get_args();
2747                 $function = array_shift( $args );
2748                 $oldIgnore = $this->ignoreErrors( true );
2749                 $tries = DEADLOCK_TRIES;
2750
2751                 if ( is_array( $function ) ) {
2752                         $fname = $function[0];
2753                 } else {
2754                         $fname = $function;
2755                 }
2756
2757                 do {
2758                         $retVal = call_user_func_array( $function, $args );
2759                         $error = $this->lastError();
2760                         $errno = $this->lastErrno();
2761                         $sql = $this->lastQuery();
2762
2763                         if ( $errno ) {
2764                                 if ( $this->wasDeadlock() ) {
2765                                         # Retry
2766                                         usleep( mt_rand( DEADLOCK_DELAY_MIN, DEADLOCK_DELAY_MAX ) );
2767                                 } else {
2768                                         $this->reportQueryError( $error, $errno, $sql, $fname );
2769                                 }
2770                         }
2771                 } while ( $this->wasDeadlock() && --$tries > 0 );
2772
2773                 $this->ignoreErrors( $oldIgnore );
2774
2775                 if ( $tries <= 0 ) {
2776                         $this->rollback( __METHOD__ );
2777                         $this->reportQueryError( $error, $errno, $sql, $fname );
2778                         return false;
2779                 } else {
2780                         $this->commit( __METHOD__ );
2781                         return $retVal;
2782                 }
2783         }
2784
2785         /**
2786          * Wait for the slave to catch up to a given master position.
2787          *
2788          * @param $pos DBMasterPos object
2789          * @param $timeout Integer: the maximum number of seconds to wait for
2790          *   synchronisation
2791          *
2792          * @return An integer: zero if the slave was past that position already,
2793          *   greater than zero if we waited for some period of time, less than
2794          *   zero if we timed out.
2795          */
2796         function masterPosWait( DBMasterPos $pos, $timeout ) {
2797                 wfProfileIn( __METHOD__ );
2798
2799                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2800                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
2801
2802                         if ( $wait > $timeout * 1e6 ) {
2803                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
2804                                 wfProfileOut( __METHOD__ );
2805                                 return -1;
2806                         } elseif ( $wait > 0 ) {
2807                                 wfDebug( "Fake slave waiting $wait us\n" );
2808                                 usleep( $wait );
2809                                 wfProfileOut( __METHOD__ );
2810                                 return 1;
2811                         } else {
2812                                 wfDebug( "Fake slave up to date ($wait us)\n" );
2813                                 wfProfileOut( __METHOD__ );
2814                                 return 0;
2815                         }
2816                 }
2817
2818                 wfProfileOut( __METHOD__ );
2819
2820                 # Real waits are implemented in the subclass.
2821                 return 0;
2822         }
2823
2824         /**
2825          * Get the replication position of this slave
2826          *
2827          * @return DBMasterPos, or false if this is not a slave.
2828          */
2829         function getSlavePos() {
2830                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2831                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
2832                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
2833                         return $pos;
2834                 } else {
2835                         # Stub
2836                         return false;
2837                 }
2838         }
2839
2840         /**
2841          * Get the position of this master
2842          *
2843          * @return DBMasterPos, or false if this is not a master
2844          */
2845         function getMasterPos() {
2846                 if ( $this->mFakeMaster ) {
2847                         return new MySQLMasterPos( 'fake', microtime( true ) );
2848                 } else {
2849                         return false;
2850                 }
2851         }
2852
2853         /**
2854          * Begin a transaction, committing any previously open transaction
2855          *
2856          * @param $fname string
2857          */
2858         function begin( $fname = 'DatabaseBase::begin' ) {
2859                 $this->query( 'BEGIN', $fname );
2860                 $this->mTrxLevel = 1;
2861         }
2862
2863         /**
2864          * End a transaction
2865          *
2866          * @param $fname string
2867          */
2868         function commit( $fname = 'DatabaseBase::commit' ) {
2869                 if ( $this->mTrxLevel ) {
2870                         $this->query( 'COMMIT', $fname );
2871                         $this->mTrxLevel = 0;
2872                 }
2873         }
2874
2875         /**
2876          * Rollback a transaction.
2877          * No-op on non-transactional databases.
2878          *
2879          * @param $fname string
2880          */
2881         function rollback( $fname = 'DatabaseBase::rollback' ) {
2882                 if ( $this->mTrxLevel ) {
2883                         $this->query( 'ROLLBACK', $fname, true );
2884                         $this->mTrxLevel = 0;
2885                 }
2886         }
2887
2888         /**
2889          * Creates a new table with structure copied from existing table
2890          * Note that unlike most database abstraction functions, this function does not
2891          * automatically append database prefix, because it works at a lower
2892          * abstraction level.
2893          * The table names passed to this function shall not be quoted (this
2894          * function calls addIdentifierQuotes when needed).
2895          *
2896          * @param $oldName String: name of table whose structure should be copied
2897          * @param $newName String: name of table to be created
2898          * @param $temporary Boolean: whether the new table should be temporary
2899          * @param $fname String: calling function name
2900          * @return Boolean: true if operation was successful
2901          */
2902         function duplicateTableStructure( $oldName, $newName, $temporary = false,
2903                 $fname = 'DatabaseBase::duplicateTableStructure' )
2904         {
2905                 throw new MWException(
2906                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
2907         }
2908
2909         /**
2910          * List all tables on the database
2911          *
2912          * @param $prefix Only show tables with this prefix, e.g. mw_
2913          * @param $fname String: calling function name
2914          */
2915         function listTables( $prefix = null, $fname = 'DatabaseBase::listTables' ) {
2916                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
2917         }
2918
2919         /**
2920          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2921          * to the format used for inserting into timestamp fields in this DBMS.
2922          *
2923          * The result is unquoted, and needs to be passed through addQuotes()
2924          * before it can be included in raw SQL.
2925          *
2926          * @param $ts string|int
2927          *
2928          * @return string
2929          */
2930         function timestamp( $ts = 0 ) {
2931                 return wfTimestamp( TS_MW, $ts );
2932         }
2933
2934         /**
2935          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2936          * to the format used for inserting into timestamp fields in this DBMS. If
2937          * NULL is input, it is passed through, allowing NULL values to be inserted
2938          * into timestamp fields.
2939          *
2940          * The result is unquoted, and needs to be passed through addQuotes()
2941          * before it can be included in raw SQL.
2942          *
2943          * @param $ts string|int
2944          *
2945          * @return string
2946          */
2947         function timestampOrNull( $ts = null ) {
2948                 if ( is_null( $ts ) ) {
2949                         return null;
2950                 } else {
2951                         return $this->timestamp( $ts );
2952                 }
2953         }
2954
2955         /**
2956          * Take the result from a query, and wrap it in a ResultWrapper if
2957          * necessary. Boolean values are passed through as is, to indicate success
2958          * of write queries or failure.
2959          *
2960          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
2961          * resource, and it was necessary to call this function to convert it to
2962          * a wrapper. Nowadays, raw database objects are never exposed to external
2963          * callers, so this is unnecessary in external code. For compatibility with
2964          * old code, ResultWrapper objects are passed through unaltered.
2965          *
2966          * @param $result bool|ResultWrapper
2967          *
2968          * @return bool|ResultWrapper
2969          */
2970         function resultObject( $result ) {
2971                 if ( empty( $result ) ) {
2972                         return false;
2973                 } elseif ( $result instanceof ResultWrapper ) {
2974                         return $result;
2975                 } elseif ( $result === true ) {
2976                         // Successful write query
2977                         return $result;
2978                 } else {
2979                         return new ResultWrapper( $this, $result );
2980                 }
2981         }
2982
2983         /**
2984          * Return aggregated value alias
2985          *
2986          * @param $valuedata
2987          * @param $valuename string
2988          *
2989          * @return string
2990          */
2991         function aggregateValue ( $valuedata, $valuename = 'value' ) {
2992                 return $valuename;
2993         }
2994
2995         /**
2996          * Ping the server and try to reconnect if it there is no connection
2997          *
2998          * @return bool Success or failure
2999          */
3000         function ping() {
3001                 # Stub.  Not essential to override.
3002                 return true;
3003         }
3004
3005         /**
3006          * Get slave lag. Currently supported only by MySQL.
3007          *
3008          * Note that this function will generate a fatal error on many
3009          * installations. Most callers should use LoadBalancer::safeGetLag()
3010          * instead.
3011          *
3012          * @return Database replication lag in seconds
3013          */
3014         function getLag() {
3015                 return intval( $this->mFakeSlaveLag );
3016         }
3017
3018         /**
3019          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3020          *
3021          * @return int
3022          */
3023         function maxListLen() {
3024                 return 0;
3025         }
3026
3027         /**
3028          * Some DBMSs have a special format for inserting into blob fields, they
3029          * don't allow simple quoted strings to be inserted. To insert into such
3030          * a field, pass the data through this function before passing it to
3031          * DatabaseBase::insert().
3032          * @param $b string
3033          * @return string
3034          */
3035         function encodeBlob( $b ) {
3036                 return $b;
3037         }
3038
3039         /**
3040          * Some DBMSs return a special placeholder object representing blob fields
3041          * in result objects. Pass the object through this function to return the
3042          * original string.
3043          * @param $b string
3044          * @return string
3045          */
3046         function decodeBlob( $b ) {
3047                 return $b;
3048         }
3049
3050         /**
3051          * Override database's default connection timeout
3052          *
3053          * @param $timeout Integer in seconds
3054          * @return void
3055          * @deprecated since 1.19; use setSessionOptions()
3056          */
3057         public function setTimeout( $timeout ) {
3058                 wfDeprecated( __METHOD__, '1.19' );
3059                 $this->setSessionOptions( array( 'connTimeout' => $timeout ) );
3060         }
3061
3062         /**
3063          * Override database's default behavior. $options include:
3064          *     'connTimeout' : Set the connection timeout value in seconds.
3065          *                     May be useful for very long batch queries such as
3066          *                     full-wiki dumps, where a single query reads out over
3067          *                     hours or days.
3068          *
3069          * @param $options Array
3070          * @return void
3071          */
3072         public function setSessionOptions( array $options ) {}
3073
3074         /**
3075          * Read and execute SQL commands from a file.
3076          *
3077          * Returns true on success, error string or exception on failure (depending
3078          * on object's error ignore settings).
3079          *
3080          * @param $filename String: File name to open
3081          * @param $lineCallback Callback: Optional function called before reading each line
3082          * @param $resultCallback Callback: Optional function called for each MySQL result
3083          * @param $fname String: Calling function name or false if name should be
3084          *      generated dynamically using $filename
3085          * @return bool|string
3086          */
3087         function sourceFile( $filename, $lineCallback = false, $resultCallback = false, $fname = false ) {
3088                 wfSuppressWarnings();
3089                 $fp = fopen( $filename, 'r' );
3090                 wfRestoreWarnings();
3091
3092                 if ( false === $fp ) {
3093                         throw new MWException( "Could not open \"{$filename}\".\n" );
3094                 }
3095
3096                 if ( !$fname ) {
3097                         $fname = __METHOD__ . "( $filename )";
3098                 }
3099
3100                 try {
3101                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname );
3102                 }
3103                 catch ( MWException $e ) {
3104                         fclose( $fp );
3105                         throw $e;
3106                 }
3107
3108                 fclose( $fp );
3109
3110                 return $error;
3111         }
3112
3113         /**
3114          * Get the full path of a patch file. Originally based on archive()
3115          * from updaters.inc. Keep in mind this always returns a patch, as
3116          * it fails back to MySQL if no DB-specific patch can be found
3117          *
3118          * @param $patch String The name of the patch, like patch-something.sql
3119          * @return String Full path to patch file
3120          */
3121         public function patchPath( $patch ) {
3122                 global $IP;
3123
3124                 $dbType = $this->getType();
3125                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3126                         return "$IP/maintenance/$dbType/archives/$patch";
3127                 } else {
3128                         return "$IP/maintenance/archives/$patch";
3129                 }
3130         }
3131
3132         /**
3133          * Set variables to be used in sourceFile/sourceStream, in preference to the
3134          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3135          * all. If it's set to false, $GLOBALS will be used.
3136          *
3137          * @param $vars False, or array mapping variable name to value.
3138          */
3139         function setSchemaVars( $vars ) {
3140                 $this->mSchemaVars = $vars;
3141         }
3142
3143         /**
3144          * Read and execute commands from an open file handle.
3145          *
3146          * Returns true on success, error string or exception on failure (depending
3147          * on object's error ignore settings).
3148          *
3149          * @param $fp Resource: File handle
3150          * @param $lineCallback Callback: Optional function called before reading each line
3151          * @param $resultCallback Callback: Optional function called for each MySQL result
3152          * @param $fname String: Calling function name
3153          * @param $inputCallback Callback: Optional function called for each complete line (ended with ;) sent
3154          * @return bool|string
3155          */
3156         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3157                 $fname = 'DatabaseBase::sourceStream', $inputCallback = false )
3158         {
3159                 $cmd = '';
3160
3161                 while ( !feof( $fp ) ) {
3162                         if ( $lineCallback ) {
3163                                 call_user_func( $lineCallback );
3164                         }
3165
3166                         $line = trim( fgets( $fp ) );
3167
3168                         if ( $line == '' ) {
3169                                 continue;
3170                         }
3171
3172                         if ( '-' == $line[0] && '-' == $line[1] ) {
3173                                 continue;
3174                         }
3175
3176                         if ( $cmd != '' ) {
3177                                 $cmd .= ' ';
3178                         }
3179
3180                         $done = $this->streamStatementEnd( $cmd, $line );
3181
3182                         $cmd .= "$line\n";
3183
3184                         if ( $done || feof( $fp ) ) {
3185                                 $cmd = $this->replaceVars( $cmd );
3186                                 if ( $inputCallback ) {
3187                                         call_user_func( $inputCallback, $cmd );
3188                                 }
3189                                 $res = $this->query( $cmd, $fname );
3190
3191                                 if ( $resultCallback ) {
3192                                         call_user_func( $resultCallback, $res, $this );
3193                                 }
3194
3195                                 if ( false === $res ) {
3196                                         $err = $this->lastError();
3197                                         return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3198                                 }
3199
3200                                 $cmd = '';
3201                         }
3202                 }
3203
3204                 return true;
3205         }
3206
3207         /**
3208          * Called by sourceStream() to check if we've reached a statement end
3209          *
3210          * @param $sql String SQL assembled so far
3211          * @param $newLine String New line about to be added to $sql
3212          * @return Bool Whether $newLine contains end of the statement
3213          */
3214         public function streamStatementEnd( &$sql, &$newLine ) {
3215                 if ( $this->delimiter ) {
3216                         $prev = $newLine;
3217                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3218                         if ( $newLine != $prev ) {
3219                                 return true;
3220                         }
3221                 }
3222                 return false;
3223         }
3224
3225         /**
3226          * Database independent variable replacement. Replaces a set of variables
3227          * in an SQL statement with their contents as given by $this->getSchemaVars().
3228          *
3229          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3230          *
3231          * - '{$var}' should be used for text and is passed through the database's
3232          *   addQuotes method.
3233          * - `{$var}` should be used for identifiers (eg: table and database names),
3234          *   it is passed through the database's addIdentifierQuotes method which
3235          *   can be overridden if the database uses something other than backticks.
3236          * - / *$var* / is just encoded, besides traditional table prefix and
3237          *   table options its use should be avoided.
3238          *
3239          * @param $ins String: SQL statement to replace variables in
3240          * @return String The new SQL statement with variables replaced
3241          */
3242         protected function replaceSchemaVars( $ins ) {
3243                 $vars = $this->getSchemaVars();
3244                 foreach ( $vars as $var => $value ) {
3245                         // replace '{$var}'
3246                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3247                         // replace `{$var}`
3248                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3249                         // replace /*$var*/
3250                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ) , $ins );
3251                 }
3252                 return $ins;
3253         }
3254
3255         /**
3256          * Replace variables in sourced SQL
3257          *
3258          * @param $ins string
3259          *
3260          * @return string
3261          */
3262         protected function replaceVars( $ins ) {
3263                 $ins = $this->replaceSchemaVars( $ins );
3264
3265                 // Table prefixes
3266                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3267                         array( $this, 'tableNameCallback' ), $ins );
3268
3269                 // Index names
3270                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3271                         array( $this, 'indexNameCallback' ), $ins );
3272
3273                 return $ins;
3274         }
3275
3276         /**
3277          * Get schema variables. If none have been set via setSchemaVars(), then
3278          * use some defaults from the current object.
3279          *
3280          * @return array
3281          */
3282         protected function getSchemaVars() {
3283                 if ( $this->mSchemaVars ) {
3284                         return $this->mSchemaVars;
3285                 } else {
3286                         return $this->getDefaultSchemaVars();
3287                 }
3288         }
3289
3290         /**
3291          * Get schema variables to use if none have been set via setSchemaVars().
3292          *
3293          * Override this in derived classes to provide variables for tables.sql
3294          * and SQL patch files.
3295          *
3296          * @return array
3297          */
3298         protected function getDefaultSchemaVars() {
3299                 return array();
3300         }
3301
3302         /**
3303          * Table name callback
3304          *
3305          * @param $matches array
3306          *
3307          * @return string
3308          */
3309         protected function tableNameCallback( $matches ) {
3310                 return $this->tableName( $matches[1] );
3311         }
3312
3313         /**
3314          * Index name callback
3315          *
3316          * @param $matches array
3317          *
3318          * @return string
3319          */
3320         protected function indexNameCallback( $matches ) {
3321                 return $this->indexName( $matches[1] );
3322         }
3323
3324         /**
3325          * Build a concatenation list to feed into a SQL query
3326          * @param $stringList Array: list of raw SQL expressions; caller is responsible for any quoting
3327          * @return String
3328          */
3329         function buildConcat( $stringList ) {
3330                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
3331         }
3332
3333         /**
3334          * Acquire a named lock
3335          *
3336          * Abstracted from Filestore::lock() so child classes can implement for
3337          * their own needs.
3338          *
3339          * @param $lockName String: name of lock to aquire
3340          * @param $method String: name of method calling us
3341          * @param $timeout Integer: timeout
3342          * @return Boolean
3343          */
3344         public function lock( $lockName, $method, $timeout = 5 ) {
3345                 return true;
3346         }
3347
3348         /**
3349          * Release a lock.
3350          *
3351          * @param $lockName String: Name of lock to release
3352          * @param $method String: Name of method calling us
3353          *
3354          * @return Returns 1 if the lock was released, 0 if the lock was not established
3355          * by this thread (in which case the lock is not released), and NULL if the named
3356          * lock did not exist
3357          */
3358         public function unlock( $lockName, $method ) {
3359                 return true;
3360         }
3361
3362         /**
3363          * Lock specific tables
3364          *
3365          * @param $read Array of tables to lock for read access
3366          * @param $write Array of tables to lock for write access
3367          * @param $method String name of caller
3368          * @param $lowPriority bool Whether to indicate writes to be LOW PRIORITY
3369          *
3370          * @return bool
3371          */
3372         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3373                 return true;
3374         }
3375
3376         /**
3377          * Unlock specific tables
3378          *
3379          * @param $method String the caller
3380          *
3381          * @return bool
3382          */
3383         public function unlockTables( $method ) {
3384                 return true;
3385         }
3386
3387         /**
3388          * Delete a table
3389          * @param $tableName string
3390          * @param $fName string
3391          * @return bool|ResultWrapper
3392          * @since 1.18
3393          */
3394         public function dropTable( $tableName, $fName = 'DatabaseBase::dropTable' ) {
3395                 if( !$this->tableExists( $tableName, $fName ) ) {
3396                         return false;
3397                 }
3398                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3399                 if( $this->cascadingDeletes() ) {
3400                         $sql .= " CASCADE";
3401                 }
3402                 return $this->query( $sql, $fName );
3403         }
3404
3405         /**
3406          * Get search engine class. All subclasses of this need to implement this
3407          * if they wish to use searching.
3408          *
3409          * @return String
3410          */
3411         public function getSearchEngine() {
3412                 return 'SearchEngineDummy';
3413         }
3414
3415         /**
3416          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3417          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3418          * because "i" sorts after all numbers.
3419          *
3420          * @return String
3421          */
3422         public function getInfinity() {
3423                 return 'infinity';
3424         }
3425
3426         /**
3427          * Encode an expiry time
3428          *
3429          * @param $expiry String: timestamp for expiry, or the 'infinity' string
3430          * @return String
3431          */
3432         public function encodeExpiry( $expiry ) {
3433                 if ( $expiry == '' || $expiry == $this->getInfinity() ) {
3434                         return $this->getInfinity();
3435                 } else {
3436                         return $this->timestamp( $expiry );
3437                 }
3438         }
3439
3440         /**
3441          * Allow or deny "big selects" for this session only. This is done by setting
3442          * the sql_big_selects session variable.
3443          *
3444          * This is a MySQL-specific feature.
3445          *
3446          * @param $value Mixed: true for allow, false for deny, or "default" to
3447          *   restore the initial value
3448          */
3449         public function setBigSelects( $value = true ) {
3450                 // no-op
3451         }
3452 }