includes/db/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * @file
   6  * @ingroup Database
   7  * This file deals with database interface functions
   8  * and query specifics/optimisations
   9  */
  10
  11 /** Number of times to re-try an operation in case of deadlock */
  12 define( 'DEADLOCK_TRIES', 4 );
  13 /** Minimum time to wait before retry, in microseconds */
  14 define( 'DEADLOCK_DELAY_MIN', 500000 );
  15 /** Maximum time to wait before retry */
  16 define( 'DEADLOCK_DELAY_MAX', 1500000 );
  17
  18 /**
  19  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  20  * following must be implemented to support MediaWiki
  21  *
  22  * @file
  23  * @ingroup Database
  24  */
  25 interface DatabaseType {
  26         /**
  27          * Get the type of the DBMS, as it appears in $wgDBtype.
  28          *
  29          * @return string
  30          */
  31         function getType();
  32
  33         /**
  34          * Open a connection to the database. Usually aborts on failure
  35          *
  36          * @param $server String: database server host
  37          * @param $user String: database user name
  38          * @param $password String: database user password
  39          * @param $dbName String: database name
  40          * @return bool
  41          * @throws DBConnectionError
  42          */
  43         function open( $server, $user, $password, $dbName );
  44
  45         /**
  46          * Fetch the next row from the given result object, in object form.
  47          * Fields can be retrieved with $row->fieldname, with fields acting like
  48          * member variables.
  49          *
  50          * @param $res SQL result object as returned from DatabaseBase::query(), etc.
  51          * @return Row object
  52          * @throws DBUnexpectedError Thrown if the database returns an error
  53          */
  54         function fetchObject( $res );
  55
  56         /**
  57          * Fetch the next row from the given result object, in associative array
  58          * form.  Fields are retrieved with $row['fieldname'].
  59          *
  60          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  61          * @return Row object
  62          * @throws DBUnexpectedError Thrown if the database returns an error
  63          */
  64         function fetchRow( $res );
  65
  66         /**
  67          * Get the number of rows in a result object
  68          *
  69          * @param $res Mixed: A SQL result
  70          * @return int
  71          */
  72         function numRows( $res );
  73
  74         /**
  75          * Get the number of fields in a result object
  76          * @see http://www.php.net/mysql_num_fields
  77          *
  78          * @param $res Mixed: A SQL result
  79          * @return int
  80          */
  81         function numFields( $res );
  82
  83         /**
  84          * Get a field name in a result object
  85          * @see http://www.php.net/mysql_field_name
  86          *
  87          * @param $res Mixed: A SQL result
  88          * @param $n Integer
  89          * @return string
  90          */
  91         function fieldName( $res, $n );
  92
  93         /**
  94          * Get the inserted value of an auto-increment row
  95          *
  96          * The value inserted should be fetched from nextSequenceValue()
  97          *
  98          * Example:
  99          * $id = $dbw->nextSequenceValue('page_page_id_seq');
 100          * $dbw->insert('page',array('page_id' => $id));
 101          * $id = $dbw->insertId();
 102          *
 103          * @return int
 104          */
 105         function insertId();
 106
 107         /**
 108          * Change the position of the cursor in a result object
 109          * @see http://www.php.net/mysql_data_seek
 110          *
 111          * @param $res Mixed: A SQL result
 112          * @param $row Mixed: Either MySQL row or ResultWrapper
 113          */
 114         function dataSeek( $res, $row );
 115
 116         /**
 117          * Get the last error number
 118          * @see http://www.php.net/mysql_errno
 119          *
 120          * @return int
 121          */
 122         function lastErrno();
 123
 124         /**
 125          * Get a description of the last error
 126          * @see http://www.php.net/mysql_error
 127          *
 128          * @return string
 129          */
 130         function lastError();
 131
 132         /**
 133          * mysql_fetch_field() wrapper
 134          * Returns false if the field doesn't exist
 135          *
 136          * @param $table string: table name
 137          * @param $field string: field name
 138          *
 139          * @return Field
 140          */
 141         function fieldInfo( $table, $field );
 142
 143         /**
 144          * Get information about an index into an object
 145          * @param $table string: Table name
 146          * @param $index string: Index name
 147          * @param $fname string: Calling function name
 148          * @return Mixed: Database-specific index description class or false if the index does not exist
 149          */
 150         function indexInfo( $table, $index, $fname = 'Database::indexInfo' );
 151
 152         /**
 153          * Get the number of rows affected by the last write query
 154          * @see http://www.php.net/mysql_affected_rows
 155          *
 156          * @return int
 157          */
 158         function affectedRows();
 159
 160         /**
 161          * Wrapper for addslashes()
 162          *
 163          * @param $s string: to be slashed.
 164          * @return string: slashed string.
 165          */
 166         function strencode( $s );
 167
 168         /**
 169          * Returns a wikitext link to the DB's website, e.g.,
 170          *     return "[http://www.mysql.com/ MySQL]";
 171          * Should at least contain plain text, if for some reason
 172          * your database has no website.
 173          *
 174          * @return string: wikitext of a link to the server software's web site
 175          */
 176         static function getSoftwareLink();
 177
 178         /**
 179          * A string describing the current software version, like from
 180          * mysql_get_server_info().
 181          *
 182          * @return string: Version information from the database server.
 183          */
 184         function getServerVersion();
 185
 186         /**
 187          * A string describing the current software version, and possibly
 188          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 189          * Use getServerVersion() to get machine-friendly information.
 190          *
 191          * @return string: Version information from the database server
 192          */
 193         function getServerInfo();
 194 }
 195
 196 /**
 197  * Database abstraction object
 198  * @ingroup Database
 199  */
 200 abstract class DatabaseBase implements DatabaseType {
 201
 202 # ------------------------------------------------------------------------------
 203 # Variables
 204 # ------------------------------------------------------------------------------
 205
 206         protected $mLastQuery = '';
 207         protected $mDoneWrites = false;
 208         protected $mPHPError = false;
 209
 210         protected $mServer, $mUser, $mPassword, $mDBname;
 211
 212         /**
 213          * @var DatabaseBase
 214          */
 215         protected $mConn = null;
 216         protected $mOpened = false;
 217
 218         protected $mTablePrefix;
 219         protected $mFlags;
 220         protected $mTrxLevel = 0;
 221         protected $mErrorCount = 0;
 222         protected $mLBInfo = array();
 223         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 224         protected $mDefaultBigSelects = null;
 225         protected $mSchemaVars = false;
 226
 227         protected $preparedArgs;
 228
 229 # ------------------------------------------------------------------------------
 230 # Accessors
 231 # ------------------------------------------------------------------------------
 232         # These optionally set a variable and return the previous state
 233
 234         /**
 235          * A string describing the current software version, and possibly
 236          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 237          * Use getServerVersion() to get machine-friendly information.
 238          *
 239          * @return string: Version information from the database server
 240          */
 241         public function getServerInfo() {
 242                 return $this->getServerVersion();
 243         }
 244
 245         /**
 246          * Boolean, controls output of large amounts of debug information.
 247          * @param $debug bool|null
 248          *   - true to enable debugging
 249          *   - false to disable debugging
 250          *   - omitted or null to do nothing
 251          *
 252          * @return The previous value of the flag
 253          */
 254         function debug( $debug = null ) {
 255                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 256         }
 257
 258         /**
 259          * Turns buffering of SQL result sets on (true) or off (false). Default is
 260          * "on".
 261          *
 262          * Unbuffered queries are very troublesome in MySQL:
 263          *
 264          *   - If another query is executed while the first query is being read
 265          *     out, the first query is killed. This means you can't call normal
 266          *     MediaWiki functions while you are reading an unbuffered query result
 267          *     from a normal wfGetDB() connection.
 268          *
 269          *   - Unbuffered queries cause the MySQL server to use large amounts of
 270          *     memory and to hold broad locks which block other queries.
 271          *
 272          * If you want to limit client-side memory, it's almost always better to
 273          * split up queries into batches using a LIMIT clause than to switch off
 274          * buffering.
 275          *
 276          * @param $buffer null|bool
 277          *
 278          * @return The previous value of the flag
 279          */
 280         function bufferResults( $buffer = null ) {
 281                 if ( is_null( $buffer ) ) {
 282                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 283                 } else {
 284                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 285                 }
 286         }
 287
 288         /**
 289          * Turns on (false) or off (true) the automatic generation and sending
 290          * of a "we're sorry, but there has been a database error" page on
 291          * database errors. Default is on (false). When turned off, the
 292          * code should use lastErrno() and lastError() to handle the
 293          * situation as appropriate.
 294          *
 295          * @param $ignoreErrors bool|null
 296          *
 297          * @return The previous value of the flag.
 298          */
 299         function ignoreErrors( $ignoreErrors = null ) {
 300                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 301         }
 302
 303         /**
 304          * Gets or sets the current transaction level.
 305          *
 306          * Historically, transactions were allowed to be "nested". This is no
 307          * longer supported, so this function really only returns a boolean.
 308          *
 309          * @param $level An integer (0 or 1), or omitted to leave it unchanged.
 310          * @return The previous value
 311          */
 312         function trxLevel( $level = null ) {
 313                 return wfSetVar( $this->mTrxLevel, $level );
 314         }
 315
 316         /**
 317          * Get/set the number of errors logged. Only useful when errors are ignored
 318          * @param $count The count to set, or omitted to leave it unchanged.
 319          * @return The error count
 320          */
 321         function errorCount( $count = null ) {
 322                 return wfSetVar( $this->mErrorCount, $count );
 323         }
 324
 325         /**
 326          * Get/set the table prefix.
 327          * @param $prefix The table prefix to set, or omitted to leave it unchanged.
 328          * @return The previous table prefix.
 329          */
 330         function tablePrefix( $prefix = null ) {
 331                 return wfSetVar( $this->mTablePrefix, $prefix );
 332         }
 333
 334         /**
 335          * Get properties passed down from the server info array of the load
 336          * balancer.
 337          *
 338          * @param $name string The entry of the info array to get, or null to get the
 339          *   whole array
 340          *
 341          * @return LoadBalancer|null
 342          */
 343         function getLBInfo( $name = null ) {
 344                 if ( is_null( $name ) ) {
 345                         return $this->mLBInfo;
 346                 } else {
 347                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 348                                 return $this->mLBInfo[$name];
 349                         } else {
 350                                 return null;
 351                         }
 352                 }
 353         }
 354
 355         /**
 356          * Set the LB info array, or a member of it. If called with one parameter,
 357          * the LB info array is set to that parameter. If it is called with two
 358          * parameters, the member with the given name is set to the given value.
 359          *
 360          * @param $name
 361          * @param $value
 362          */
 363         function setLBInfo( $name, $value = null ) {
 364                 if ( is_null( $value ) ) {
 365                         $this->mLBInfo = $name;
 366                 } else {
 367                         $this->mLBInfo[$name] = $value;
 368                 }
 369         }
 370
 371         /**
 372          * Set lag time in seconds for a fake slave
 373          *
 374          * @param $lag int
 375          */
 376         function setFakeSlaveLag( $lag ) {
 377                 $this->mFakeSlaveLag = $lag;
 378         }
 379
 380         /**
 381          * Make this connection a fake master
 382          *
 383          * @param $enabled bool
 384          */
 385         function setFakeMaster( $enabled = true ) {
 386                 $this->mFakeMaster = $enabled;
 387         }
 388
 389         /**
 390          * Returns true if this database supports (and uses) cascading deletes
 391          *
 392          * @return bool
 393          */
 394         function cascadingDeletes() {
 395                 return false;
 396         }
 397
 398         /**
 399          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 400          *
 401          * @return bool
 402          */
 403         function cleanupTriggers() {
 404                 return false;
 405         }
 406
 407         /**
 408          * Returns true if this database is strict about what can be put into an IP field.
 409          * Specifically, it uses a NULL value instead of an empty string.
 410          *
 411          * @return bool
 412          */
 413         function strictIPs() {
 414                 return false;
 415         }
 416
 417         /**
 418          * Returns true if this database uses timestamps rather than integers
 419          *
 420          * @return bool
 421         */
 422         function realTimestamps() {
 423                 return false;
 424         }
 425
 426         /**
 427          * Returns true if this database does an implicit sort when doing GROUP BY
 428          *
 429          * @return bool
 430          */
 431         function implicitGroupby() {
 432                 return true;
 433         }
 434
 435         /**
 436          * Returns true if this database does an implicit order by when the column has an index
 437          * For example: SELECT page_title FROM page LIMIT 1
 438          *
 439          * @return bool
 440          */
 441         function implicitOrderby() {
 442                 return true;
 443         }
 444
 445         /**
 446          * Returns true if this database requires that SELECT DISTINCT queries require that all
 447            ORDER BY expressions occur in the SELECT list per the SQL92 standard
 448          *
 449          * @return bool
 450          */
 451         function standardSelectDistinct() {
 452                 return true;
 453         }
 454
 455         /**
 456          * Returns true if this database can do a native search on IP columns
 457          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 458          *
 459          * @return bool
 460          */
 461         function searchableIPs() {
 462                 return false;
 463         }
 464
 465         /**
 466          * Returns true if this database can use functional indexes
 467          *
 468          * @return bool
 469          */
 470         function functionalIndexes() {
 471                 return false;
 472         }
 473
 474         /**
 475          * Return the last query that went through DatabaseBase::query()
 476          * @return String
 477          */
 478         function lastQuery() {
 479                 return $this->mLastQuery;
 480         }
 481
 482         /**
 483          * Returns true if the connection may have been used for write queries.
 484          * Should return true if unsure.
 485          *
 486          * @return bool
 487          */
 488         function doneWrites() {
 489                 return $this->mDoneWrites;
 490         }
 491
 492         /**
 493          * Is a connection to the database open?
 494          * @return Boolean
 495          */
 496         function isOpen() {
 497                 return $this->mOpened;
 498         }
 499
 500         /**
 501          * Set a flag for this connection
 502          *
 503          * @param $flag Integer: DBO_* constants from Defines.php:
 504          *   - DBO_DEBUG: output some debug info (same as debug())
 505          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 506          *   - DBO_IGNORE: ignore errors (same as ignoreErrors())
 507          *   - DBO_TRX: automatically start transactions
 508          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 509          *       and removes it in command line mode
 510          *   - DBO_PERSISTENT: use persistant database connection
 511          */
 512         function setFlag( $flag ) {
 513                 $this->mFlags |= $flag;
 514         }
 515
 516         /**
 517          * Clear a flag for this connection
 518          *
 519          * @param $flag: same as setFlag()'s $flag param
 520          */
 521         function clearFlag( $flag ) {
 522                 $this->mFlags &= ~$flag;
 523         }
 524
 525         /**
 526          * Returns a boolean whether the flag $flag is set for this connection
 527          *
 528          * @param $flag: same as setFlag()'s $flag param
 529          * @return Boolean
 530          */
 531         function getFlag( $flag ) {
 532                 return !!( $this->mFlags & $flag );
 533         }
 534
 535         /**
 536          * General read-only accessor
 537          *
 538          * @param $name string
 539          *
 540          * @return string
 541          */
 542         function getProperty( $name ) {
 543                 return $this->$name;
 544         }
 545
 546         /**
 547          * @return string
 548          */
 549         function getWikiID() {
 550                 if ( $this->mTablePrefix ) {
 551                         return "{$this->mDBname}-{$this->mTablePrefix}";
 552                 } else {
 553                         return $this->mDBname;
 554                 }
 555         }
 556
 557         /**
 558          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 559          *
 560          * @return string
 561          */
 562         public function getSchemaPath() {
 563                 global $IP;
 564                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 565                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 566                 } else {
 567                         return "$IP/maintenance/tables.sql";
 568                 }
 569         }
 570
 571 # ------------------------------------------------------------------------------
 572 # Other functions
 573 # ------------------------------------------------------------------------------
 574
 575         /**
 576          * Constructor.
 577          * @param $server String: database server host
 578          * @param $user String: database user name
 579          * @param $password String: database user password
 580          * @param $dbName String: database name
 581          * @param $flags
 582          * @param $tablePrefix String: database table prefixes. By default use the prefix gave in LocalSettings.php
 583          */
 584         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 585                 $flags = 0, $tablePrefix = 'get from global'
 586         ) {
 587                 global $wgDBprefix, $wgCommandLineMode;
 588
 589                 $this->mFlags = $flags;
 590
 591                 if ( $this->mFlags & DBO_DEFAULT ) {
 592                         if ( $wgCommandLineMode ) {
 593                                 $this->mFlags &= ~DBO_TRX;
 594                         } else {
 595                                 $this->mFlags |= DBO_TRX;
 596                         }
 597                 }
 598
 599                 /** Get the default table prefix*/
 600                 if ( $tablePrefix == 'get from global' ) {
 601                         $this->mTablePrefix = $wgDBprefix;
 602                 } else {
 603                         $this->mTablePrefix = $tablePrefix;
 604                 }
 605
 606                 if ( $user ) {
 607                         $this->open( $server, $user, $password, $dbName );
 608                 }
 609         }
 610
 611         /**
 612          * Called by unserialize. Needed to reopen DB connection, which
 613          * is not saved by serialize.
 614          */
 615         public function __wakeup() {
 616         if ( $this->isOpen() ) {
 617                         $this->open( $this->mServer, $this->mUser,
 618                                      $this->mPassword, $this->mDBname);
 619                 }
 620         }
 621
 622         /**
 623          * Same as new DatabaseMysql( ... ), kept for backward compatibility
 624          * @deprecated since 1.17
 625          *
 626          * @return DatabaseMysql
 627          */
 628         static function newFromParams( $server, $user, $password, $dbName, $flags = 0 ) {
 629                 wfDeprecated( __METHOD__ );
 630                 return new DatabaseMysql( $server, $user, $password, $dbName, $flags );
 631         }
 632
 633         /**
 634          * Given a DB type, construct the name of the appropriate child class of
 635          * DatabaseBase. This is designed to replace all of the manual stuff like:
 636          *      $class = 'Database' . ucfirst( strtolower( $type ) );
 637          * as well as validate against the canonical list of DB types we have
 638          *
 639          * This factory function is mostly useful for when you need to connect to a
 640          * database other than the MediaWiki default (such as for external auth,
 641          * an extension, et cetera). Do not use this to connect to the MediaWiki
 642          * database. Example uses in core:
 643          * @see LoadBalancer::reallyOpenConnection()
 644          * @see ExternalUser_MediaWiki::initFromCond()
 645          * @see ForeignDBRepo::getMasterDB()
 646          * @see WebInstaller_DBConnect::execute()
 647          *
 648          * @param $dbType String A possible DB type
 649          * @param $p Array An array of options to pass to the constructor.
 650          *    Valid options are: host, user, password, dbname, flags, tablePrefix
 651          * @return DatabaseBase subclass or null
 652          */
 653         public final static function factory( $dbType, $p = array() ) {
 654                 $canonicalDBTypes = array(
 655                         'mysql', 'postgres', 'sqlite', 'oracle', 'mssql', 'ibm_db2'
 656                 );
 657                 $dbType = strtolower( $dbType );
 658
 659                 if( in_array( $dbType, $canonicalDBTypes ) ) {
 660                         $class = 'Database' . ucfirst( $dbType );
 661                         return new $class(
 662                                 isset( $p['host'] ) ? $p['host'] : false,
 663                                 isset( $p['user'] ) ? $p['user'] : false,
 664                                 isset( $p['password'] ) ? $p['password'] : false,
 665                                 isset( $p['dbname'] ) ? $p['dbname'] : false,
 666                                 isset( $p['flags'] ) ? $p['flags'] : 0,
 667                                 isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global'
 668                         );
 669                 } else {
 670                         return null;
 671                 }
 672         }
 673
 674         protected function installErrorHandler() {
 675                 $this->mPHPError = false;
 676                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 677                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 678         }
 679
 680         /**
 681          * @return bool|string
 682          */
 683         protected function restoreErrorHandler() {
 684                 restore_error_handler();
 685                 if ( $this->htmlErrors !== false ) {
 686                         ini_set( 'html_errors', $this->htmlErrors );
 687                 }
 688                 if ( $this->mPHPError ) {
 689                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 690                         $error = preg_replace( '!^.*?:(.*)$!', '$1', $error );
 691                         return $error;
 692                 } else {
 693                         return false;
 694                 }
 695         }
 696
 697         protected function connectionErrorHandler( $errno,  $errstr ) {
 698                 $this->mPHPError = $errstr;
 699         }
 700
 701         /**
 702          * Closes a database connection.
 703          * if it is open : commits any open transactions
 704          *
 705          * @return Bool operation success. true if already closed.
 706          */
 707         function close() {
 708                 # Stub, should probably be overridden
 709                 return true;
 710         }
 711
 712         /**
 713          * @param $error String: fallback error message, used if none is given by DB
 714          */
 715         function reportConnectionError( $error = 'Unknown error' ) {
 716                 $myError = $this->lastError();
 717                 if ( $myError ) {
 718                         $error = $myError;
 719                 }
 720
 721                 # New method
 722                 throw new DBConnectionError( $this, $error );
 723         }
 724
 725         /**
 726          * The DBMS-dependent part of query()
 727          *
 728          * @param  $sql String: SQL query.
 729          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 730          */
 731         protected abstract function doQuery( $sql );
 732
 733         /**
 734          * Determine whether a query writes to the DB.
 735          * Should return true if unsure.
 736          *
 737          * @param $sql string
 738          *
 739          * @return bool
 740          */
 741         function isWriteQuery( $sql ) {
 742                 return !preg_match( '/^(?:SELECT|BEGIN|COMMIT|SET|SHOW|\(SELECT)\b/i', $sql );
 743         }
 744
 745         /**
 746          * Run an SQL query and return the result. Normally throws a DBQueryError
 747          * on failure. If errors are ignored, returns false instead.
 748          *
 749          * In new code, the query wrappers select(), insert(), update(), delete(),
 750          * etc. should be used where possible, since they give much better DBMS
 751          * independence and automatically quote or validate user input in a variety
 752          * of contexts. This function is generally only useful for queries which are
 753          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 754          * as CREATE TABLE.
 755          *
 756          * However, the query wrappers themselves should call this function.
 757          *
 758          * @param  $sql        String: SQL query
 759          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 760          *     comment (you can use __METHOD__ or add some extra info)
 761          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 762          *     maybe best to catch the exception instead?
 763          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 764          *     for a successful read query, or false on failure if $tempIgnore set
 765          * @throws DBQueryError Thrown when the database returns an error of any kind
 766          */
 767         public function query( $sql, $fname = '', $tempIgnore = false ) {
 768                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 769                 if ( !Profiler::instance()->isStub() ) {
 770                         # generalizeSQL will probably cut down the query to reasonable
 771                         # logging size most of the time. The substr is really just a sanity check.
 772
 773                         if ( $isMaster ) {
 774                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 775                                 $totalProf = 'DatabaseBase::query-master';
 776                         } else {
 777                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 778                                 $totalProf = 'DatabaseBase::query';
 779                         }
 780
 781                         wfProfileIn( $totalProf );
 782                         wfProfileIn( $queryProf );
 783                 }
 784
 785                 $this->mLastQuery = $sql;
 786                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 787                         # Set a flag indicating that writes have been done
 788                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 789                         $this->mDoneWrites = true;
 790                 }
 791
 792                 # Add a comment for easy SHOW PROCESSLIST interpretation
 793                 global $wgUser;
 794                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 795                         $userName = $wgUser->getName();
 796                         if ( mb_strlen( $userName ) > 15 ) {
 797                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 798                         }
 799                         $userName = str_replace( '/', '', $userName );
 800                 } else {
 801                         $userName = '';
 802                 }
 803                 $commentedSql = preg_replace( '/\s/', " /* $fname $userName */ ", $sql, 1 );
 804
 805                 # If DBO_TRX is set, start a transaction
 806                 if ( ( $this->mFlags & DBO_TRX ) && !$this->trxLevel() &&
 807                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' ) {
 808                         # avoid establishing transactions for SHOW and SET statements too -
 809                         # that would delay transaction initializations to once connection
 810                         # is really used by application
 811                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 812                         if ( strpos( $sqlstart, "SHOW " ) !== 0 and strpos( $sqlstart, "SET " ) !== 0 )
 813                                 $this->begin();
 814                 }
 815
 816                 if ( $this->debug() ) {
 817                         static $cnt = 0;
 818
 819                         $cnt++;
 820                         $sqlx = substr( $commentedSql, 0, 500 );
 821                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 822
 823                         if ( $isMaster ) {
 824                                 wfDebug( "Query $cnt (master): $sqlx\n" );
 825                         } else {
 826                                 wfDebug( "Query $cnt (slave): $sqlx\n" );
 827                         }
 828                 }
 829
 830                 if ( istainted( $sql ) & TC_MYSQL ) {
 831                         throw new MWException( 'Tainted query found' );
 832                 }
 833
 834                 # Do the query and handle errors
 835                 $ret = $this->doQuery( $commentedSql );
 836
 837                 # Try reconnecting if the connection was lost
 838                 if ( false === $ret && $this->wasErrorReissuable() ) {
 839                         # Transaction is gone, like it or not
 840                         $this->mTrxLevel = 0;
 841                         wfDebug( "Connection lost, reconnecting...\n" );
 842
 843                         if ( $this->ping() ) {
 844                                 wfDebug( "Reconnected\n" );
 845                                 $sqlx = substr( $commentedSql, 0, 500 );
 846                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
 847                                 global $wgRequestTime;
 848                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
 849                                 if ( $elapsed < 300 ) {
 850                                         # Not a database error to lose a transaction after a minute or two
 851                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
 852                                 }
 853                                 $ret = $this->doQuery( $commentedSql );
 854                         } else {
 855                                 wfDebug( "Failed\n" );
 856                         }
 857                 }
 858
 859                 if ( false === $ret ) {
 860                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 861                 }
 862
 863                 if ( !Profiler::instance()->isStub() ) {
 864                         wfProfileOut( $queryProf );
 865                         wfProfileOut( $totalProf );
 866                 }
 867
 868                 return $this->resultObject( $ret );
 869         }
 870
 871         /**
 872          * Report a query error. Log the error, and if neither the object ignore
 873          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
 874          *
 875          * @param $error String
 876          * @param $errno Integer
 877          * @param $sql String
 878          * @param $fname String
 879          * @param $tempIgnore Boolean
 880          */
 881         function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
 882                 # Ignore errors during error handling to avoid infinite recursion
 883                 $ignore = $this->ignoreErrors( true );
 884                 ++$this->mErrorCount;
 885
 886                 if ( $ignore || $tempIgnore ) {
 887                         wfDebug( "SQL ERROR (ignored): $error\n" );
 888                         $this->ignoreErrors( $ignore );
 889                 } else {
 890                         $sql1line = str_replace( "\n", "\\n", $sql );
 891                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
 892                         wfDebug( "SQL ERROR: " . $error . "\n" );
 893                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
 894                 }
 895         }
 896
 897         /**
 898          * Intended to be compatible with the PEAR::DB wrapper functions.
 899          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
 900          *
 901          * ? = scalar value, quoted as necessary
 902          * ! = raw SQL bit (a function for instance)
 903          * & = filename; reads the file and inserts as a blob
 904          *     (we don't use this though...)
 905          *
 906          * This function should not be used directly by new code outside of the
 907          * database classes. The query wrapper functions (select() etc.) should be
 908          * used instead.
 909          *
 910          * @param $sql string
 911          * @param $func string
 912          *
 913          * @return array
 914          */
 915         function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
 916                 /* MySQL doesn't support prepared statements (yet), so just
 917                    pack up the query for reference. We'll manually replace
 918                    the bits later. */
 919                 return array( 'query' => $sql, 'func' => $func );
 920         }
 921
 922         /**
 923          * Free a prepared query, generated by prepare().
 924          */
 925         function freePrepared( $prepared ) {
 926                 /* No-op by default */
 927         }
 928
 929         /**
 930          * Execute a prepared query with the various arguments
 931          * @param $prepared String: the prepared sql
 932          * @param $args Mixed: Either an array here, or put scalars as varargs
 933          *
 934          * @return ResultWrapper
 935          */
 936         function execute( $prepared, $args = null ) {
 937                 if ( !is_array( $args ) ) {
 938                         # Pull the var args
 939                         $args = func_get_args();
 940                         array_shift( $args );
 941                 }
 942
 943                 $sql = $this->fillPrepared( $prepared['query'], $args );
 944
 945                 return $this->query( $sql, $prepared['func'] );
 946         }
 947
 948         /**
 949          * Prepare & execute an SQL statement, quoting and inserting arguments
 950          * in the appropriate places.
 951          *
 952          * This function should not be used directly by new code outside of the
 953          * database classes. The query wrapper functions (select() etc.) should be
 954          * used instead.
 955          *
 956          * @param $query String
 957          * @param $args ...
 958          *
 959          * @return ResultWrapper
 960          */
 961         function safeQuery( $query, $args = null ) {
 962                 $prepared = $this->prepare( $query, 'DatabaseBase::safeQuery' );
 963
 964                 if ( !is_array( $args ) ) {
 965                         # Pull the var args
 966                         $args = func_get_args();
 967                         array_shift( $args );
 968                 }
 969
 970                 $retval = $this->execute( $prepared, $args );
 971                 $this->freePrepared( $prepared );
 972
 973                 return $retval;
 974         }
 975
 976         /**
 977          * For faking prepared SQL statements on DBs that don't support
 978          * it directly.
 979          * @param $preparedQuery String: a 'preparable' SQL statement
 980          * @param $args Array of arguments to fill it with
 981          * @return string executable SQL
 982          */
 983         function fillPrepared( $preparedQuery, $args ) {
 984                 reset( $args );
 985                 $this->preparedArgs =& $args;
 986
 987                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
 988                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
 989         }
 990
 991         /**
 992          * preg_callback func for fillPrepared()
 993          * The arguments should be in $this->preparedArgs and must not be touched
 994          * while we're doing this.
 995          *
 996          * @param $matches Array
 997          * @return String
 998          */
 999         function fillPreparedArg( $matches ) {
1000                 switch( $matches[1] ) {
1001                         case '\\?': return '?';
1002                         case '\\!': return '!';
1003                         case '\\&': return '&';
1004                 }
1005
1006                 list( /* $n */ , $arg ) = each( $this->preparedArgs );
1007
1008                 switch( $matches[1] ) {
1009                         case '?': return $this->addQuotes( $arg );
1010                         case '!': return $arg;
1011                         case '&':
1012                                 # return $this->addQuotes( file_get_contents( $arg ) );
1013                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1014                         default:
1015                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1016                 }
1017         }
1018
1019         /**
1020          * Free a result object returned by query() or select(). It's usually not
1021          * necessary to call this, just use unset() or let the variable holding
1022          * the result object go out of scope.
1023          *
1024          * @param $res Mixed: A SQL result
1025          */
1026         function freeResult( $res ) {
1027         }
1028
1029         /**
1030          * Simple UPDATE wrapper.
1031          * Usually throws a DBQueryError on failure.
1032          * If errors are explicitly ignored, returns success
1033          *
1034          * This function exists for historical reasons, DatabaseBase::update() has a more standard
1035          * calling convention and feature set
1036          *
1037          * @param $table string
1038          * @param $var
1039          * @param $value
1040          * @param $cond
1041          * @param $fname string
1042          *
1043          * @return bool
1044          */
1045         function set( $table, $var, $value, $cond, $fname = 'DatabaseBase::set' ) {
1046                 $table = $this->tableName( $table );
1047                 $sql = "UPDATE $table SET $var = '" .
1048                   $this->strencode( $value ) . "' WHERE ($cond)";
1049
1050                 return (bool)$this->query( $sql, $fname );
1051         }
1052
1053         /**
1054          * A SELECT wrapper which returns a single field from a single result row.
1055          *
1056          * Usually throws a DBQueryError on failure. If errors are explicitly
1057          * ignored, returns false on failure.
1058          *
1059          * If no result rows are returned from the query, false is returned.
1060          *
1061          * @param $table string|array Table name. See DatabaseBase::select() for details.
1062          * @param $var string The field name to select. This must be a valid SQL
1063          *   fragment: do not use unvalidated user input.
1064          * @param $cond string|array The condition array. See DatabaseBase::select() for details.
1065          * @param $fname string The function name of the caller.
1066          * @param $options string|array The query options. See DatabaseBase::select() for details.
1067          *
1068          * @return false|mixed The value from the field, or false on failure.
1069          */
1070         function selectField( $table, $var, $cond = '', $fname = 'DatabaseBase::selectField',
1071                 $options = array() )
1072         {
1073                 if ( !is_array( $options ) ) {
1074                         $options = array( $options );
1075                 }
1076
1077                 $options['LIMIT'] = 1;
1078
1079                 $res = $this->select( $table, $var, $cond, $fname, $options );
1080
1081                 if ( $res === false || !$this->numRows( $res ) ) {
1082                         return false;
1083                 }
1084
1085                 $row = $this->fetchRow( $res );
1086
1087                 if ( $row !== false ) {
1088                         return reset( $row );
1089                 } else {
1090                         return false;
1091                 }
1092         }
1093
1094         /**
1095          * Returns an optional USE INDEX clause to go after the table, and a
1096          * string to go at the end of the query.
1097          *
1098          * @param $options Array: associative array of options to be turned into
1099          *              an SQL query, valid keys are listed in the function.
1100          * @return Array
1101          * @see DatabaseBase::select()
1102          */
1103         function makeSelectOptions( $options ) {
1104                 $preLimitTail = $postLimitTail = '';
1105                 $startOpts = '';
1106
1107                 $noKeyOptions = array();
1108
1109                 foreach ( $options as $key => $option ) {
1110                         if ( is_numeric( $key ) ) {
1111                                 $noKeyOptions[$option] = true;
1112                         }
1113                 }
1114
1115                 if ( isset( $options['GROUP BY'] ) ) {
1116                         $gb = is_array( $options['GROUP BY'] )
1117                                 ? implode( ',', $options['GROUP BY'] )
1118                                 : $options['GROUP BY'];
1119                         $preLimitTail .= " GROUP BY {$gb}";
1120                 }
1121
1122                 if ( isset( $options['HAVING'] ) ) {
1123                         $preLimitTail .= " HAVING {$options['HAVING']}";
1124                 }
1125
1126                 if ( isset( $options['ORDER BY'] ) ) {
1127                         $ob = is_array( $options['ORDER BY'] )
1128                                 ? implode( ',', $options['ORDER BY'] )
1129                                 : $options['ORDER BY'];
1130                         $preLimitTail .= " ORDER BY {$ob}";
1131                 }
1132
1133                 // if (isset($options['LIMIT'])) {
1134                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1135                 //              isset($options['OFFSET']) ? $options['OFFSET']
1136                 //              : false);
1137                 // }
1138
1139                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1140                         $postLimitTail .= ' FOR UPDATE';
1141                 }
1142
1143                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1144                         $postLimitTail .= ' LOCK IN SHARE MODE';
1145                 }
1146
1147                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1148                         $startOpts .= 'DISTINCT';
1149                 }
1150
1151                 # Various MySQL extensions
1152                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1153                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1154                 }
1155
1156                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1157                         $startOpts .= ' HIGH_PRIORITY';
1158                 }
1159
1160                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1161                         $startOpts .= ' SQL_BIG_RESULT';
1162                 }
1163
1164                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1165                         $startOpts .= ' SQL_BUFFER_RESULT';
1166                 }
1167
1168                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1169                         $startOpts .= ' SQL_SMALL_RESULT';
1170                 }
1171
1172                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1173                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1174                 }
1175
1176                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1177                         $startOpts .= ' SQL_CACHE';
1178                 }
1179
1180                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1181                         $startOpts .= ' SQL_NO_CACHE';
1182                 }
1183
1184                 if ( isset( $options['USE INDEX'] ) && ! is_array( $options['USE INDEX'] ) ) {
1185                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1186                 } else {
1187                         $useIndex = '';
1188                 }
1189
1190                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1191         }
1192
1193         /**
1194          * Execute a SELECT query constructed using the various parameters provided.
1195          * See below for full details of the parameters.
1196          *
1197          * @param $table String|Array Table name
1198          * @param $vars String|Array Field names
1199          * @param $conds String|Array Conditions
1200          * @param $fname String Caller function name
1201          * @param $options Array Query options
1202          * @param $join_conds Array Join conditions
1203          *
1204          * @param $table string|array
1205          *
1206          * May be either an array of table names, or a single string holding a table
1207          * name. If an array is given, table aliases can be specified, for example:
1208          *
1209          *    array( 'a' => 'user' )
1210          *
1211          * This includes the user table in the query, with the alias "a" available
1212          * for use in field names (e.g. a.user_name).
1213          *
1214          * All of the table names given here are automatically run through
1215          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1216          * added, and various other table name mappings to be performed.
1217          *
1218          *
1219          * @param $vars string|array
1220          *
1221          * May be either a field name or an array of field names. The field names
1222          * here are complete fragments of SQL, for direct inclusion into the SELECT
1223          * query. Expressions and aliases may be specified as in SQL, for example:
1224          *
1225          *   array( 'MAX(rev_id) AS maxrev' )
1226          *
1227          * If an expression is given, care must be taken to ensure that it is
1228          * DBMS-independent.
1229          *
1230          *
1231          * @param $conds string|array
1232          *
1233          * May be either a string containing a single condition, or an array of
1234          * conditions. If an array is given, the conditions constructed from each
1235          * element are combined with AND.
1236          *
1237          * Array elements may take one of two forms:
1238          *
1239          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1240          *   - Elements with a string key are interpreted as equality conditions,
1241          *     where the key is the field name.
1242          *     - If the value of such an array element is a scalar (such as a
1243          *       string), it will be treated as data and thus quoted appropriately.
1244          *       If it is null, an IS NULL clause will be added.
1245          *     - If the value is an array, an IN(...) clause will be constructed,
1246          *       such that the field name may match any of the elements in the
1247          *       array. The elements of the array will be quoted.
1248          *     - If the field name ends with "!", this is taken as a flag which
1249          *       inverts the comparison, allowing NOT IN clauses to be constructed,
1250          *       for example: array( 'user_id!' => array( 1, 2, 3 ) )
1251          *
1252          * Note that expressions are often DBMS-dependent in their syntax.
1253          * DBMS-independent wrappers are provided for constructing several types of
1254          * expression commonly used in condition queries. See:
1255          *    - DatabaseBase::buildLike()
1256          *    - DatabaseBase::conditional()
1257          *
1258          *
1259          * @param $options string|array
1260          *
1261          * Optional: Array of query options. Boolean options are specified by
1262          * including them in the array as a string value with a numeric key, for
1263          * example:
1264          *
1265          *    array( 'FOR UPDATE' )
1266          *
1267          * The supported options are:
1268          *
1269          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1270          *     with LIMIT can theoretically be used for paging through a result set,
1271          *     but this is discouraged in MediaWiki for performance reasons.
1272          *
1273          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1274          *     and then the first rows are taken until the limit is reached. LIMIT
1275          *     is applied to a result set after OFFSET.
1276          *
1277          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1278          *     changed until the next COMMIT.
1279          *
1280          *   - DISTINCT: Boolean: return only unique result rows.
1281          *
1282          *   - GROUP BY: May be either an SQL fragment string naming a field or
1283          *     expression to group by, or an array of such SQL fragments.
1284          *
1285          *   - HAVING: A string containing a HAVING clause.
1286          *
1287          *   - ORDER BY: May be either an SQL fragment giving a field name or
1288          *     expression to order by, or an array of such SQL fragments.
1289          *
1290          *   - USE INDEX: This may be either a string giving the index name to use
1291          *     for the query, or an array. If it is an associative array, each key
1292          *     gives the table name (or alias), each value gives the index name to
1293          *     use for that table. All strings are SQL fragments and so should be
1294          *     validated by the caller.
1295          *
1296          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1297          *     instead of SELECT.
1298          *
1299          * And also the following boolean MySQL extensions, see the MySQL manual
1300          * for documentation:
1301          *
1302          *    - LOCK IN SHARE MODE
1303          *    - STRAIGHT_JOIN
1304          *    - HIGH_PRIORITY
1305          *    - SQL_BIG_RESULT
1306          *    - SQL_BUFFER_RESULT
1307          *    - SQL_SMALL_RESULT
1308          *    - SQL_CALC_FOUND_ROWS
1309          *    - SQL_CACHE
1310          *    - SQL_NO_CACHE
1311          *
1312          *
1313          * @param $join_conds string|array
1314          *
1315          * Optional associative array of table-specific join conditions. In the
1316          * most common case, this is unnecessary, since the join condition can be
1317          * in $conds. However, it is useful for doing a LEFT JOIN.
1318          *
1319          * The key of the array contains the table name or alias. The value is an
1320          * array with two elements, numbered 0 and 1. The first gives the type of
1321          * join, the second is an SQL fragment giving the join condition for that
1322          * table. For example:
1323          *
1324          *    array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
1325          *
1326          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1327          *   with no rows in it will be returned. If there was a query error, a
1328          *   DBQueryError exception will be thrown, except if the "ignore errors"
1329          *   option was set, in which case false will be returned.
1330          */
1331         function select( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1332                 $options = array(), $join_conds = array() ) {
1333                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1334
1335                 return $this->query( $sql, $fname );
1336         }
1337
1338         /**
1339          * The equivalent of DatabaseBase::select() except that the constructed SQL
1340          * is returned, instead of being immediately executed.
1341          *
1342          * @param $table string|array Table name
1343          * @param $vars string|array Field names
1344          * @param $conds string|array Conditions
1345          * @param $fname string Caller function name
1346          * @param $options string|array Query options
1347          * @param $join_conds string|array Join conditions
1348          *
1349          * @return SQL query string.
1350          * @see DatabaseBase::select()
1351          */
1352         function selectSQLText( $table, $vars, $conds = '', $fname = 'DatabaseBase::select', $options = array(), $join_conds = array() ) {
1353                 if ( is_array( $vars ) ) {
1354                         $vars = implode( ',', $vars );
1355                 }
1356
1357                 $options = (array)$options;
1358
1359                 if ( is_array( $table ) ) {
1360                         $useIndex = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1361                                 ? $options['USE INDEX']
1362                                 : array();
1363                         if ( count( $join_conds ) || count( $useIndex ) ) {
1364                                 $from = ' FROM ' .
1365                                         $this->tableNamesWithUseIndexOrJOIN( $table, $useIndex, $join_conds );
1366                         } else {
1367                                 $from = ' FROM ' . implode( ',', $this->tableNamesWithAlias( $table ) );
1368                         }
1369                 } elseif ( $table != '' ) {
1370                         if ( $table { 0 } == ' ' ) {
1371                                 $from = ' FROM ' . $table;
1372                         } else {
1373                                 $from = ' FROM ' . $this->tableName( $table );
1374                         }
1375                 } else {
1376                         $from = '';
1377                 }
1378
1379                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) = $this->makeSelectOptions( $options );
1380
1381                 if ( !empty( $conds ) ) {
1382                         if ( is_array( $conds ) ) {
1383                                 $conds = $this->makeList( $conds, LIST_AND );
1384                         }
1385                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1386                 } else {
1387                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1388                 }
1389
1390                 if ( isset( $options['LIMIT'] ) ) {
1391                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1392                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1393                 }
1394                 $sql = "$sql $postLimitTail";
1395
1396                 if ( isset( $options['EXPLAIN'] ) ) {
1397                         $sql = 'EXPLAIN ' . $sql;
1398                 }
1399
1400                 return $sql;
1401         }
1402
1403         /**
1404          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1405          * that a single row object is returned. If the query returns no rows,
1406          * false is returned.
1407          *
1408          * @param $table string|array Table name
1409          * @param $vars string|array Field names
1410          * @param $conds|array Conditions
1411          * @param $fname string Caller function name
1412          * @param $options string|array Query options
1413          * @param $join_conds array|string Join conditions
1414          *
1415          * @return ResultWrapper|bool
1416          */
1417         function selectRow( $table, $vars, $conds, $fname = 'DatabaseBase::selectRow',
1418                 $options = array(), $join_conds = array() )
1419         {
1420                 $options['LIMIT'] = 1;
1421                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1422
1423                 if ( $res === false ) {
1424                         return false;
1425                 }
1426
1427                 if ( !$this->numRows( $res ) ) {
1428                         return false;
1429                 }
1430
1431                 $obj = $this->fetchObject( $res );
1432
1433                 return $obj;
1434         }
1435
1436         /**
1437          * Estimate rows in dataset.
1438          *
1439          * MySQL allows you to estimate the number of rows that would be returned
1440          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1441          * index cardinality statistics, and is notoriously inaccurate, especially
1442          * when large numbers of rows have recently been added or deleted.
1443          *
1444          * For DBMSs that don't support fast result size estimation, this function
1445          * will actually perform the SELECT COUNT(*).
1446          *
1447          * Takes the same arguments as DatabaseBase::select().
1448          *
1449          * @param $table String: table name
1450          * @param Array|string $vars : unused
1451          * @param Array|string $conds : filters on the table
1452          * @param $fname String: function name for profiling
1453          * @param $options Array: options for select
1454          * @return Integer: row count
1455          */
1456         public function estimateRowCount( $table, $vars = '*', $conds = '',
1457                 $fname = 'DatabaseBase::estimateRowCount', $options = array() )
1458         {
1459                 $rows = 0;
1460                 $res = $this->select ( $table, 'COUNT(*) AS rowcount', $conds, $fname, $options );
1461
1462                 if ( $res ) {
1463                         $row = $this->fetchRow( $res );
1464                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1465                 }
1466
1467                 return $rows;
1468         }
1469
1470         /**
1471          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1472          * It's only slightly flawed. Don't use for anything important.
1473          *
1474          * @param $sql String A SQL Query
1475          *
1476          * @return string
1477          */
1478         static function generalizeSQL( $sql ) {
1479                 # This does the same as the regexp below would do, but in such a way
1480                 # as to avoid crashing php on some large strings.
1481                 # $sql = preg_replace ( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql);
1482
1483                 $sql = str_replace ( "\\\\", '', $sql );
1484                 $sql = str_replace ( "\\'", '', $sql );
1485                 $sql = str_replace ( "\\\"", '', $sql );
1486                 $sql = preg_replace ( "/'.*'/s", "'X'", $sql );
1487                 $sql = preg_replace ( '/".*"/s', "'X'", $sql );
1488
1489                 # All newlines, tabs, etc replaced by single space
1490                 $sql = preg_replace ( '/\s+/', ' ', $sql );
1491
1492                 # All numbers => N
1493                 $sql = preg_replace ( '/-?[0-9]+/s', 'N', $sql );
1494
1495                 return $sql;
1496         }
1497
1498         /**
1499          * Determines whether a field exists in a table
1500          *
1501          * @param $table String: table name
1502          * @param $field String: filed to check on that table
1503          * @param $fname String: calling function name (optional)
1504          * @return Boolean: whether $table has filed $field
1505          */
1506         function fieldExists( $table, $field, $fname = 'DatabaseBase::fieldExists' ) {
1507                 $info = $this->fieldInfo( $table, $field );
1508
1509                 return (bool)$info;
1510         }
1511
1512         /**
1513          * Determines whether an index exists
1514          * Usually throws a DBQueryError on failure
1515          * If errors are explicitly ignored, returns NULL on failure
1516          *
1517          * @param $table
1518          * @param $index
1519          * @param $fname string
1520          *
1521          * @return bool|null
1522          */
1523         function indexExists( $table, $index, $fname = 'DatabaseBase::indexExists' ) {
1524                 $info = $this->indexInfo( $table, $index, $fname );
1525                 if ( is_null( $info ) ) {
1526                         return null;
1527                 } else {
1528                         return $info !== false;
1529                 }
1530         }
1531
1532         /**
1533          * Query whether a given table exists
1534          *
1535          * @param $table string
1536          *
1537          * @return bool
1538          */
1539         function tableExists( $table ) {
1540                 $table = $this->tableName( $table );
1541                 $old = $this->ignoreErrors( true );
1542                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", __METHOD__ );
1543                 $this->ignoreErrors( $old );
1544
1545                 return (bool)$res;
1546         }
1547
1548         /**
1549          * @todo document
1550          * mysql_field_type() wrapper
1551          */
1552         function fieldType( $res, $index ) {
1553                 if ( $res instanceof ResultWrapper ) {
1554                         $res = $res->result;
1555                 }
1556
1557                 return mysql_field_type( $res, $index );
1558         }
1559
1560         /**
1561          * Determines if a given index is unique
1562          *
1563          * @param $table string
1564          * @param $index string
1565          *
1566          * @return bool
1567          */
1568         function indexUnique( $table, $index ) {
1569                 $indexInfo = $this->indexInfo( $table, $index );
1570
1571                 if ( !$indexInfo ) {
1572                         return null;
1573                 }
1574
1575                 return !$indexInfo[0]->Non_unique;
1576         }
1577
1578         /**
1579          * Helper for DatabaseBase::insert().
1580          *
1581          * @param $options array
1582          * @return string
1583          */
1584         function makeInsertOptions( $options ) {
1585                 return implode( ' ', $options );
1586         }
1587
1588         /**
1589          * INSERT wrapper, inserts an array into a table.
1590          *
1591          * $a may be either:
1592          *
1593          *   - A single associative array. The array keys are the field names, and
1594          *     the values are the values to insert. The values are treated as data
1595          *     and will be quoted appropriately. If NULL is inserted, this will be
1596          *     converted to a database NULL.
1597          *   - An array with numeric keys, holding a list of associative arrays.
1598          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1599          *     each subarray must be identical to each other, and in the same order.
1600          *
1601          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1602          * returns success.
1603          *
1604          * $options is an array of options, with boolean options encoded as values
1605          * with numeric keys, in the same style as $options in
1606          * DatabaseBase::select(). Supported options are:
1607          *
1608          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1609          *     any rows which cause duplicate key errors are not inserted. It's
1610          *     possible to determine how many rows were successfully inserted using
1611          *     DatabaseBase::affectedRows().
1612          *
1613          * @param $table   String Table name. This will be passed through
1614          *                 DatabaseBase::tableName().
1615          * @param $a       Array of rows to insert
1616          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1617          * @param $options Array of options
1618          *
1619          * @return bool
1620          */
1621         function insert( $table, $a, $fname = 'DatabaseBase::insert', $options = array() ) {
1622                 # No rows to insert, easy just return now
1623                 if ( !count( $a ) ) {
1624                         return true;
1625                 }
1626
1627                 $table = $this->tableName( $table );
1628
1629                 if ( !is_array( $options ) ) {
1630                         $options = array( $options );
1631                 }
1632
1633                 $options = $this->makeInsertOptions( $options );
1634
1635                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1636                         $multi = true;
1637                         $keys = array_keys( $a[0] );
1638                 } else {
1639                         $multi = false;
1640                         $keys = array_keys( $a );
1641                 }
1642
1643                 $sql = 'INSERT ' . $options .
1644                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1645
1646                 if ( $multi ) {
1647                         $first = true;
1648                         foreach ( $a as $row ) {
1649                                 if ( $first ) {
1650                                         $first = false;
1651                                 } else {
1652                                         $sql .= ',';
1653                                 }
1654                                 $sql .= '(' . $this->makeList( $row ) . ')';
1655                         }
1656                 } else {
1657                         $sql .= '(' . $this->makeList( $a ) . ')';
1658                 }
1659
1660                 return (bool)$this->query( $sql, $fname );
1661         }
1662
1663         /**
1664          * Make UPDATE options for the DatabaseBase::update function
1665          *
1666          * @param $options Array: The options passed to DatabaseBase::update
1667          * @return string
1668          */
1669         function makeUpdateOptions( $options ) {
1670                 if ( !is_array( $options ) ) {
1671                         $options = array( $options );
1672                 }
1673
1674                 $opts = array();
1675
1676                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1677                         $opts[] = $this->lowPriorityOption();
1678                 }
1679
1680                 if ( in_array( 'IGNORE', $options ) ) {
1681                         $opts[] = 'IGNORE';
1682                 }
1683
1684                 return implode( ' ', $opts );
1685         }
1686
1687         /**
1688          * UPDATE wrapper. Takes a condition array and a SET array.
1689          *
1690          * @param $table  String name of the table to UPDATE. This will be passed through
1691          *                DatabaseBase::tableName().
1692          *
1693          * @param $values Array:  An array of values to SET. For each array element,
1694          *                the key gives the field name, and the value gives the data
1695          *                to set that field to. The data will be quoted by
1696          *                DatabaseBase::addQuotes().
1697          *
1698          * @param $conds  Array:  An array of conditions (WHERE). See
1699          *                DatabaseBase::select() for the details of the format of
1700          *                condition arrays. Use '*' to update all rows.
1701          *
1702          * @param $fname  String: The function name of the caller (from __METHOD__),
1703          *                for logging and profiling.
1704          *
1705          * @param $options Array: An array of UPDATE options, can be:
1706          *                   - IGNORE: Ignore unique key conflicts
1707          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1708          * @return Boolean
1709          */
1710         function update( $table, $values, $conds, $fname = 'DatabaseBase::update', $options = array() ) {
1711                 $table = $this->tableName( $table );
1712                 $opts = $this->makeUpdateOptions( $options );
1713                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1714
1715                 if ( $conds !== array() && $conds !== '*' ) {
1716                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1717                 }
1718
1719                 return $this->query( $sql, $fname );
1720         }
1721
1722         /**
1723          * Makes an encoded list of strings from an array
1724          * @param $a Array containing the data
1725          * @param $mode int Constant
1726          *      - LIST_COMMA:          comma separated, no field names
1727          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1728          *        the documentation for $conds in DatabaseBase::select().
1729          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1730          *      - LIST_SET:            comma separated with field names, like a SET clause
1731          *      - LIST_NAMES:          comma separated field names
1732          *
1733          * @return string
1734          */
1735         function makeList( $a, $mode = LIST_COMMA ) {
1736                 if ( !is_array( $a ) ) {
1737                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1738                 }
1739
1740                 $first = true;
1741                 $list = '';
1742
1743                 foreach ( $a as $field => $value ) {
1744                         if ( !$first ) {
1745                                 if ( $mode == LIST_AND ) {
1746                                         $list .= ' AND ';
1747                                 } elseif ( $mode == LIST_OR ) {
1748                                         $list .= ' OR ';
1749                                 } else {
1750                                         $list .= ',';
1751                                 }
1752                         } else {
1753                                 $first = false;
1754                         }
1755
1756                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1757                                 $list .= "($value)";
1758                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1759                                 $list .= "$value";
1760                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1761                                 if ( count( $value ) == 0 ) {
1762                                         throw new MWException( __METHOD__ . ': empty input' );
1763                                 } elseif ( count( $value ) == 1 ) {
1764                                         // Special-case single values, as IN isn't terribly efficient
1765                                         // Don't necessarily assume the single key is 0; we don't
1766                                         // enforce linear numeric ordering on other arrays here.
1767                                         $value = array_values( $value );
1768                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1769                                 } else {
1770                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1771                                 }
1772                         } elseif ( $value === null ) {
1773                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1774                                         $list .= "$field IS ";
1775                                 } elseif ( $mode == LIST_SET ) {
1776                                         $list .= "$field = ";
1777                                 }
1778                                 $list .= 'NULL';
1779                         } else {
1780                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1781                                         $list .= "$field = ";
1782                                 }
1783                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1784                         }
1785                 }
1786
1787                 return $list;
1788         }
1789
1790         /**
1791          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1792          * The keys on each level may be either integers or strings.
1793          *
1794          * @param $data Array: organized as 2-d
1795          *              array(baseKeyVal => array(subKeyVal => <ignored>, ...), ...)
1796          * @param $baseKey String: field name to match the base-level keys to (eg 'pl_namespace')
1797          * @param $subKey String: field name to match the sub-level keys to (eg 'pl_title')
1798          * @return Mixed: string SQL fragment, or false if no items in array.
1799          */
1800         function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1801                 $conds = array();
1802
1803                 foreach ( $data as $base => $sub ) {
1804                         if ( count( $sub ) ) {
1805                                 $conds[] = $this->makeList(
1806                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1807                                         LIST_AND );
1808                         }
1809                 }
1810
1811                 if ( $conds ) {
1812                         return $this->makeList( $conds, LIST_OR );
1813                 } else {
1814                         // Nothing to search for...
1815                         return false;
1816                 }
1817         }
1818
1819         /**
1820          * Build a partial where clause from a 3-d array
1821          * The keys on each level may be either integers or strings.
1822          *
1823          * @param $data Array: organized as 3-d array(baseKeyVal => array(middleKeyVal => array(subKeyVal => <ignored>, ...), ...), ...)
1824          * @param $baseKey String: field name to match the base-level keys to (eg 'gtl_to_prefix')
1825          * @param $middleKey String: field name to match the middle-level keys to (eg 'gtl_to_namespace')
1826          * @param $subKey String: field name to match the sub-level keys to (eg 'gtl_to_title')
1827          * @return Mixed: string SQL fragment, or false if no items in array.
1828          */
1829         function makeWhereFrom3d( $data, $baseKey, $middleKey, $subKey ) {
1830                 $conds = array();
1831                 foreach ( $data as $base => $subdata ) {
1832                         foreach ( $subdata as $middle => $sub ) {
1833                                 if ( count( $sub ) ) {
1834                                         $conds[] = $this->makeList(
1835                                                 array( $baseKey => $base,
1836                                                         $middleKey => $middle,
1837                                                         $subKey => array_keys( $sub ) ),
1838                                                 LIST_AND
1839                                         );
1840                                 }
1841                         }
1842                 }
1843
1844                 if ( $conds ) {
1845                         return $this->makeList( $conds, LIST_OR );
1846                 } else {
1847                         // Nothing to search for...
1848                         return false;
1849                 }
1850         }
1851
1852         /**
1853          * Bitwise operations
1854          */
1855
1856         /**
1857          * @param $field
1858          * @return string
1859          */
1860         function bitNot( $field ) {
1861                 return "(~$field)";
1862         }
1863
1864         /**
1865          * @param $fieldLeft
1866          * @param $fieldRight
1867          * @return string
1868          */
1869         function bitAnd( $fieldLeft, $fieldRight ) {
1870                 return "($fieldLeft & $fieldRight)";
1871         }
1872
1873         /**
1874          * @param  $fieldLeft
1875          * @param  $fieldRight
1876          * @return string
1877          */
1878         function bitOr( $fieldLeft, $fieldRight ) {
1879                 return "($fieldLeft | $fieldRight)";
1880         }
1881
1882         /**
1883          * Change the current database
1884          *
1885          * @todo Explain what exactly will fail if this is not overridden.
1886          *
1887          * @param $db
1888          *
1889          * @return bool Success or failure
1890          */
1891         function selectDB( $db ) {
1892                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
1893                 # if your database engine supports a concept similar to MySQL's
1894                 # databases you may as well.
1895                 $this->mDBname = $db;
1896                 return true;
1897         }
1898
1899         /**
1900          * Get the current DB name
1901          */
1902         function getDBname() {
1903                 return $this->mDBname;
1904         }
1905
1906         /**
1907          * Get the server hostname or IP address
1908          */
1909         function getServer() {
1910                 return $this->mServer;
1911         }
1912
1913         /**
1914          * Format a table name ready for use in constructing an SQL query
1915          *
1916          * This does two important things: it quotes the table names to clean them up,
1917          * and it adds a table prefix if only given a table name with no quotes.
1918          *
1919          * All functions of this object which require a table name call this function
1920          * themselves. Pass the canonical name to such functions. This is only needed
1921          * when calling query() directly.
1922          *
1923          * @param $name String: database table name
1924          * @param $format String One of:
1925          *   quoted - Automatically pass the table name through addIdentifierQuotes()
1926          *            so that it can be used in a query.
1927          *   raw - Do not add identifier quotes to the table name
1928          * @return String: full database name
1929          */
1930         function tableName( $name, $format = 'quoted' ) {
1931                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
1932                 # Skip the entire process when we have a string quoted on both ends.
1933                 # Note that we check the end so that we will still quote any use of
1934                 # use of `database`.table. But won't break things if someone wants
1935                 # to query a database table with a dot in the name.
1936                 if ( $this->isQuotedIdentifier( $name ) ) {
1937                         return $name;
1938                 }
1939
1940                 # Lets test for any bits of text that should never show up in a table
1941                 # name. Basically anything like JOIN or ON which are actually part of
1942                 # SQL queries, but may end up inside of the table value to combine
1943                 # sql. Such as how the API is doing.
1944                 # Note that we use a whitespace test rather than a \b test to avoid
1945                 # any remote case where a word like on may be inside of a table name
1946                 # surrounded by symbols which may be considered word breaks.
1947                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1948                         return $name;
1949                 }
1950
1951                 # Split database and table into proper variables.
1952                 # We reverse the explode so that database.table and table both output
1953                 # the correct table.
1954                 $dbDetails = array_reverse( explode( '.', $name, 2 ) );
1955                 if ( isset( $dbDetails[1] ) ) {
1956                         list( $table, $database ) = $dbDetails;
1957                 } else {
1958                         list( $table ) = $dbDetails;
1959                 }
1960                 $prefix = $this->mTablePrefix; # Default prefix
1961
1962                 # A database name has been specified in input. We don't want any
1963                 # prefixes added.
1964                 if ( isset( $database ) ) {
1965                         $prefix = '';
1966                 }
1967
1968                 # Note that we use the long format because php will complain in in_array if
1969                 # the input is not an array, and will complain in is_array if it is not set.
1970                 if ( !isset( $database ) # Don't use shared database if pre selected.
1971                  && isset( $wgSharedDB ) # We have a shared database
1972                  && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
1973                  && isset( $wgSharedTables )
1974                  && is_array( $wgSharedTables )
1975                  && in_array( $table, $wgSharedTables ) ) { # A shared table is selected
1976                         $database = $wgSharedDB;
1977                         $prefix   = isset( $wgSharedPrefix ) ? $wgSharedPrefix : $prefix;
1978                 }
1979
1980                 # Quote the $database and $table and apply the prefix if not quoted.
1981                 if ( isset( $database ) ) {
1982                         $database = ( $format == 'quoted' || $this->isQuotedIdentifier( $database ) ? $database : $this->addIdentifierQuotes( $database ) );
1983                 }
1984
1985                 $table = "{$prefix}{$table}";
1986                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $table ) ) {
1987                         $table = $this->addIdentifierQuotes( "{$table}" );
1988                 }
1989
1990                 # Merge our database and table into our final table name.
1991                 $tableName = ( isset( $database ) ? "{$database}.{$table}" : "{$table}" );
1992
1993                 return $tableName;
1994         }
1995
1996         /**
1997          * Fetch a number of table names into an array
1998          * This is handy when you need to construct SQL for joins
1999          *
2000          * Example:
2001          * extract($dbr->tableNames('user','watchlist'));
2002          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2003          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2004          *
2005          * @return array
2006          */
2007         public function tableNames() {
2008                 $inArray = func_get_args();
2009                 $retVal = array();
2010
2011                 foreach ( $inArray as $name ) {
2012                         $retVal[$name] = $this->tableName( $name );
2013                 }
2014
2015                 return $retVal;
2016         }
2017
2018         /**
2019          * Fetch a number of table names into an zero-indexed numerical array
2020          * This is handy when you need to construct SQL for joins
2021          *
2022          * Example:
2023          * list( $user, $watchlist ) = $dbr->tableNamesN('user','watchlist');
2024          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2025          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2026          *
2027          * @return array
2028          */
2029         public function tableNamesN() {
2030                 $inArray = func_get_args();
2031                 $retVal = array();
2032
2033                 foreach ( $inArray as $name ) {
2034                         $retVal[] = $this->tableName( $name );
2035                 }
2036
2037                 return $retVal;
2038         }
2039
2040         /**
2041          * Get an aliased table name
2042          * e.g. tableName AS newTableName
2043          *
2044          * @param $name string Table name, see tableName()
2045          * @param $alias string|bool Alias (optional)
2046          * @return string SQL name for aliased table. Will not alias a table to its own name
2047          */
2048         public function tableNameWithAlias( $name, $alias = false ) {
2049                 if ( !$alias || $alias == $name ) {
2050                         return $this->tableName( $name );
2051                 } else {
2052                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2053                 }
2054         }
2055
2056         /**
2057          * Gets an array of aliased table names
2058          *
2059          * @param $tables array( [alias] => table )
2060          * @return array of strings, see tableNameWithAlias()
2061          */
2062         public function tableNamesWithAlias( $tables ) {
2063                 $retval = array();
2064                 foreach ( $tables as $alias => $table ) {
2065                         if ( is_numeric( $alias ) ) {
2066                                 $alias = $table;
2067                         }
2068                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2069                 }
2070                 return $retval;
2071         }
2072
2073         /**
2074          * Get the aliased table name clause for a FROM clause
2075          * which might have a JOIN and/or USE INDEX clause
2076          *
2077          * @param $tables array ( [alias] => table )
2078          * @param $use_index array Same as for select()
2079          * @param $join_conds array Same as for select()
2080          * @return string
2081          */
2082         protected function tableNamesWithUseIndexOrJOIN(
2083                 $tables, $use_index = array(), $join_conds = array()
2084         ) {
2085                 $ret = array();
2086                 $retJOIN = array();
2087                 $use_index = (array)$use_index;
2088                 $join_conds = (array)$join_conds;
2089
2090                 foreach ( $tables as $alias => $table ) {
2091                         if ( !is_string( $alias ) ) {
2092                                 // No alias? Set it equal to the table name
2093                                 $alias = $table;
2094                         }
2095                         // Is there a JOIN clause for this table?
2096                         if ( isset( $join_conds[$alias] ) ) {
2097                                 list( $joinType, $conds ) = $join_conds[$alias];
2098                                 $tableClause = $joinType;
2099                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2100                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2101                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2102                                         if ( $use != '' ) {
2103                                                 $tableClause .= ' ' . $use;
2104                                         }
2105                                 }
2106                                 $on = $this->makeList( (array)$conds, LIST_AND );
2107                                 if ( $on != '' ) {
2108                                         $tableClause .= ' ON (' . $on . ')';
2109                                 }
2110
2111                                 $retJOIN[] = $tableClause;
2112                         // Is there an INDEX clause for this table?
2113                         } elseif ( isset( $use_index[$alias] ) ) {
2114                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2115                                 $tableClause .= ' ' . $this->useIndexClause(
2116                                         implode( ',', (array)$use_index[$alias] ) );
2117
2118                                 $ret[] = $tableClause;
2119                         } else {
2120                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2121
2122                                 $ret[] = $tableClause;
2123                         }
2124                 }
2125
2126                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2127                 $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2128                 $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2129
2130                 // Compile our final table clause
2131                 return implode( ' ', array( $straightJoins, $otherJoins ) );
2132         }
2133
2134         /**
2135          * Get the name of an index in a given table
2136          *
2137          * @param $index
2138          *
2139          * @return string
2140          */
2141         function indexName( $index ) {
2142                 // Backwards-compatibility hack
2143                 $renamed = array(
2144                         'ar_usertext_timestamp' => 'usertext_timestamp',
2145                         'un_user_id'            => 'user_id',
2146                         'un_user_ip'            => 'user_ip',
2147                 );
2148
2149                 if ( isset( $renamed[$index] ) ) {
2150                         return $renamed[$index];
2151                 } else {
2152                         return $index;
2153                 }
2154         }
2155
2156         /**
2157          * If it's a string, adds quotes and backslashes
2158          * Otherwise returns as-is
2159          *
2160          * @param $s string
2161          *
2162          * @return string
2163          */
2164         function addQuotes( $s ) {
2165                 if ( $s === null ) {
2166                         return 'NULL';
2167                 } else {
2168                         # This will also quote numeric values. This should be harmless,
2169                         # and protects against weird problems that occur when they really
2170                         # _are_ strings such as article titles and string->number->string
2171                         # conversion is not 1:1.
2172                         return "'" . $this->strencode( $s ) . "'";
2173                 }
2174         }
2175
2176         /**
2177          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2178          * MySQL uses `backticks` while basically everything else uses double quotes.
2179          * Since MySQL is the odd one out here the double quotes are our generic
2180          * and we implement backticks in DatabaseMysql.
2181          *
2182          * @param $s string
2183          *
2184          * @return string
2185          */
2186         public function addIdentifierQuotes( $s ) {
2187                 return '"' . str_replace( '"', '""', $s ) . '"';
2188         }
2189
2190         /**
2191          * Returns if the given identifier looks quoted or not according to
2192          * the database convention for quoting identifiers .
2193          *
2194          * @param $name string
2195          *
2196          * @return boolean
2197          */
2198         public function isQuotedIdentifier( $name ) {
2199                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2200         }
2201
2202         /**
2203          * Backwards compatibility, identifier quoting originated in DatabasePostgres
2204          * which used quote_ident which does not follow our naming conventions
2205          * was renamed to addIdentifierQuotes.
2206          * @deprecated since 1.18 use addIdentifierQuotes
2207          *
2208          * @param $s string
2209          *
2210          * @return string
2211          */
2212         function quote_ident( $s ) {
2213                 wfDeprecated( __METHOD__ );
2214                 return $this->addIdentifierQuotes( $s );
2215         }
2216
2217         /**
2218          * Escape string for safe LIKE usage.
2219          * WARNING: you should almost never use this function directly,
2220          * instead use buildLike() that escapes everything automatically
2221          * @deprecated since 1.17, warnings in 1.17, removed in ???
2222          *
2223          * @param $s string
2224          *
2225          * @return string
2226          */
2227         public function escapeLike( $s ) {
2228                 wfDeprecated( __METHOD__ );
2229                 return $this->escapeLikeInternal( $s );
2230         }
2231
2232         /**
2233          * @param $s string
2234          * @return string
2235          */
2236         protected function escapeLikeInternal( $s ) {
2237                 $s = str_replace( '\\', '\\\\', $s );
2238                 $s = $this->strencode( $s );
2239                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2240
2241                 return $s;
2242         }
2243
2244         /**
2245          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2246          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2247          * Alternatively, the function could be provided with an array of aforementioned parameters.
2248          *
2249          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2250          * for subpages of 'My page title'.
2251          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2252          *
2253          * @since 1.16
2254          * @return String: fully built LIKE statement
2255          */
2256         function buildLike() {
2257                 $params = func_get_args();
2258
2259                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2260                         $params = $params[0];
2261                 }
2262
2263                 $s = '';
2264
2265                 foreach ( $params as $value ) {
2266                         if ( $value instanceof LikeMatch ) {
2267                                 $s .= $value->toString();
2268                         } else {
2269                                 $s .= $this->escapeLikeInternal( $value );
2270                         }
2271                 }
2272
2273                 return " LIKE '" . $s . "' ";
2274         }
2275
2276         /**
2277          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2278          *
2279          * @return LikeMatch
2280          */
2281         function anyChar() {
2282                 return new LikeMatch( '_' );
2283         }
2284
2285         /**
2286          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2287          *
2288          * @return LikeMatch
2289          */
2290         function anyString() {
2291                 return new LikeMatch( '%' );
2292         }
2293
2294         /**
2295          * Returns an appropriately quoted sequence value for inserting a new row.
2296          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2297          * subclass will return an integer, and save the value for insertId()
2298          */
2299         function nextSequenceValue( $seqName ) {
2300                 return null;
2301         }
2302
2303         /**
2304          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2305          * is only needed because a) MySQL must be as efficient as possible due to
2306          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2307          * which index to pick.  Anyway, other databases might have different
2308          * indexes on a given table.  So don't bother overriding this unless you're
2309          * MySQL.
2310          */
2311         function useIndexClause( $index ) {
2312                 return '';
2313         }
2314
2315         /**
2316          * REPLACE query wrapper.
2317          *
2318          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2319          * except that when there is a duplicate key error, the old row is deleted
2320          * and the new row is inserted in its place.
2321          *
2322          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2323          * perform the delete, we need to know what the unique indexes are so that
2324          * we know how to find the conflicting rows.
2325          *
2326          * It may be more efficient to leave off unique indexes which are unlikely
2327          * to collide. However if you do this, you run the risk of encountering
2328          * errors which wouldn't have occurred in MySQL.
2329          *
2330          * @param $table String: The table to replace the row(s) in.
2331          * @param $rows array Can be either a single row to insert, or multiple rows,
2332          *    in the same format as for DatabaseBase::insert()
2333          * @param $uniqueIndexes array is an array of indexes. Each element may be either
2334          *    a field name or an array of field names
2335          * @param $fname String: Calling function name (use __METHOD__) for logs/profiling
2336          */
2337         function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseBase::replace' ) {
2338                 $quotedTable = $this->tableName( $table );
2339
2340                 if ( count( $rows ) == 0 ) {
2341                         return;
2342                 }
2343
2344                 # Single row case
2345                 if ( !is_array( reset( $rows ) ) ) {
2346                         $rows = array( $rows );
2347                 }
2348
2349                 foreach( $rows as $row ) {
2350                         # Delete rows which collide
2351                         if ( $uniqueIndexes ) {
2352                                 $sql = "DELETE FROM $quotedTable WHERE ";
2353                                 $first = true;
2354                                 foreach ( $uniqueIndexes as $index ) {
2355                                         if ( $first ) {
2356                                                 $first = false;
2357                                                 $sql .= '( ';
2358                                         } else {
2359                                                 $sql .= ' ) OR ( ';
2360                                         }
2361                                         if ( is_array( $index ) ) {
2362                                                 $first2 = true;
2363                                                 foreach ( $index as $col ) {
2364                                                         if ( $first2 ) {
2365                                                                 $first2 = false;
2366                                                         } else {
2367                                                                 $sql .= ' AND ';
2368                                                         }
2369                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2370                                                 }
2371                                         } else {
2372                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2373                                         }
2374                                 }
2375                                 $sql .= ' )';
2376                                 $this->query( $sql, $fname );
2377                         }
2378
2379                         # Now insert the row
2380                         $this->insert( $table, $row );
2381                 }
2382         }
2383
2384         /**
2385          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2386          * statement.
2387          *
2388          * @param $table Table name
2389          * @param $rows Rows to insert
2390          * @param $fname Caller function name
2391          *
2392          * @return ResultWrapper
2393          */
2394         protected function nativeReplace( $table, $rows, $fname ) {
2395                 $table = $this->tableName( $table );
2396
2397                 # Single row case
2398                 if ( !is_array( reset( $rows ) ) ) {
2399                         $rows = array( $rows );
2400                 }
2401
2402                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2403                 $first = true;
2404
2405                 foreach ( $rows as $row ) {
2406                         if ( $first ) {
2407                                 $first = false;
2408                         } else {
2409                                 $sql .= ',';
2410                         }
2411
2412                         $sql .= '(' . $this->makeList( $row ) . ')';
2413                 }
2414
2415                 return $this->query( $sql, $fname );
2416         }
2417
2418         /**
2419          * DELETE where the condition is a join.
2420          *
2421          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2422          * we use sub-selects
2423          *
2424          * For safety, an empty $conds will not delete everything. If you want to
2425          * delete all rows where the join condition matches, set $conds='*'.
2426          *
2427          * DO NOT put the join condition in $conds.
2428          *
2429          * @param $delTable   String: The table to delete from.
2430          * @param $joinTable  String: The other table.
2431          * @param $delVar     String: The variable to join on, in the first table.
2432          * @param $joinVar    String: The variable to join on, in the second table.
2433          * @param $conds      Array: Condition array of field names mapped to variables,
2434          *                    ANDed together in the WHERE clause
2435          * @param $fname      String: Calling function name (use __METHOD__) for
2436          *                    logs/profiling
2437          */
2438         function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2439                 $fname = 'DatabaseBase::deleteJoin' )
2440         {
2441                 if ( !$conds ) {
2442                         throw new DBUnexpectedError( $this,
2443                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2444                 }
2445
2446                 $delTable = $this->tableName( $delTable );
2447                 $joinTable = $this->tableName( $joinTable );
2448                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2449                 if ( $conds != '*' ) {
2450                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2451                 }
2452                 $sql .= ')';
2453
2454                 $this->query( $sql, $fname );
2455         }
2456
2457         /**
2458          * Returns the size of a text field, or -1 for "unlimited"
2459          *
2460          * @param $table string
2461          * @param $field string
2462          *
2463          * @return int
2464          */
2465         function textFieldSize( $table, $field ) {
2466                 $table = $this->tableName( $table );
2467                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2468                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2469                 $row = $this->fetchObject( $res );
2470
2471                 $m = array();
2472
2473                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2474                         $size = $m[1];
2475                 } else {
2476                         $size = -1;
2477                 }
2478
2479                 return $size;
2480         }
2481
2482         /**
2483          * A string to insert into queries to show that they're low-priority, like
2484          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2485          * string and nothing bad should happen.
2486          *
2487          * @return string Returns the text of the low priority option if it is
2488          *   supported, or a blank string otherwise
2489          */
2490         function lowPriorityOption() {
2491                 return '';
2492         }
2493
2494         /**
2495          * DELETE query wrapper.
2496          *
2497          * @param $table Array Table name
2498          * @param $conds String|Array of conditions. See $conds in DatabaseBase::select() for
2499          *               the format. Use $conds == "*" to delete all rows
2500          * @param $fname String name of the calling function
2501          *
2502          * @return bool
2503          */
2504         function delete( $table, $conds, $fname = 'DatabaseBase::delete' ) {
2505                 if ( !$conds ) {
2506                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2507                 }
2508
2509                 $table = $this->tableName( $table );
2510                 $sql = "DELETE FROM $table";
2511
2512                 if ( $conds != '*' ) {
2513                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2514                 }
2515
2516                 return $this->query( $sql, $fname );
2517         }
2518
2519         /**
2520          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2521          * into another table.
2522          *
2523          * @param $destTable string The table name to insert into
2524          * @param $srcTable string|array May be either a table name, or an array of table names
2525          *    to include in a join.
2526          *
2527          * @param $varMap array must be an associative array of the form
2528          *    array( 'dest1' => 'source1', ...). Source items may be literals
2529          *    rather than field names, but strings should be quoted with
2530          *    DatabaseBase::addQuotes()
2531          *
2532          * @param $conds array Condition array. See $conds in DatabaseBase::select() for
2533          *    the details of the format of condition arrays. May be "*" to copy the
2534          *    whole table.
2535          *
2536          * @param $fname string The function name of the caller, from __METHOD__
2537          *
2538          * @param $insertOptions array Options for the INSERT part of the query, see
2539          *    DatabaseBase::insert() for details.
2540          * @param $selectOptions array Options for the SELECT part of the query, see
2541          *    DatabaseBase::select() for details.
2542          *
2543          * @return ResultWrapper
2544          */
2545         function insertSelect( $destTable, $srcTable, $varMap, $conds,
2546                 $fname = 'DatabaseBase::insertSelect',
2547                 $insertOptions = array(), $selectOptions = array() )
2548         {
2549                 $destTable = $this->tableName( $destTable );
2550
2551                 if ( is_array( $insertOptions ) ) {
2552                         $insertOptions = implode( ' ', $insertOptions );
2553                 }
2554
2555                 if ( !is_array( $selectOptions ) ) {
2556                         $selectOptions = array( $selectOptions );
2557                 }
2558
2559                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2560
2561                 if ( is_array( $srcTable ) ) {
2562                         $srcTable =  implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2563                 } else {
2564                         $srcTable = $this->tableName( $srcTable );
2565                 }
2566
2567                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2568                         " SELECT $startOpts " . implode( ',', $varMap ) .
2569                         " FROM $srcTable $useIndex ";
2570
2571                 if ( $conds != '*' ) {
2572                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2573                 }
2574
2575                 $sql .= " $tailOpts";
2576
2577                 return $this->query( $sql, $fname );
2578         }
2579
2580         /**
2581          * Construct a LIMIT query with optional offset.  This is used for query
2582          * pages.  The SQL should be adjusted so that only the first $limit rows
2583          * are returned.  If $offset is provided as well, then the first $offset
2584          * rows should be discarded, and the next $limit rows should be returned.
2585          * If the result of the query is not ordered, then the rows to be returned
2586          * are theoretically arbitrary.
2587          *
2588          * $sql is expected to be a SELECT, if that makes a difference.  For
2589          * UPDATE, limitResultForUpdate should be used.
2590          *
2591          * The version provided by default works in MySQL and SQLite.  It will very
2592          * likely need to be overridden for most other DBMSes.
2593          *
2594          * @param $sql String SQL query we will append the limit too
2595          * @param $limit Integer the SQL limit
2596          * @param $offset Integer|false the SQL offset (default false)
2597          *
2598          * @return string
2599          */
2600         function limitResult( $sql, $limit, $offset = false ) {
2601                 if ( !is_numeric( $limit ) ) {
2602                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2603                 }
2604
2605                 return "$sql LIMIT "
2606                                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2607                                 . "{$limit} ";
2608         }
2609
2610         /**
2611          * @param $sql
2612          * @param $num
2613          * @return string
2614          */
2615         function limitResultForUpdate( $sql, $num ) {
2616                 return $this->limitResult( $sql, $num, 0 );
2617         }
2618
2619         /**
2620          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2621          * within the UNION construct.
2622          * @return Boolean
2623          */
2624         function unionSupportsOrderAndLimit() {
2625                 return true; // True for almost every DB supported
2626         }
2627
2628         /**
2629          * Construct a UNION query
2630          * This is used for providing overload point for other DB abstractions
2631          * not compatible with the MySQL syntax.
2632          * @param $sqls Array: SQL statements to combine
2633          * @param $all Boolean: use UNION ALL
2634          * @return String: SQL fragment
2635          */
2636         function unionQueries( $sqls, $all ) {
2637                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2638                 return '(' . implode( $glue, $sqls ) . ')';
2639         }
2640
2641         /**
2642          * Returns an SQL expression for a simple conditional.  This doesn't need
2643          * to be overridden unless CASE isn't supported in your DBMS.
2644          *
2645          * @param $cond String: SQL expression which will result in a boolean value
2646          * @param $trueVal String: SQL expression to return if true
2647          * @param $falseVal String: SQL expression to return if false
2648          * @return String: SQL fragment
2649          */
2650         function conditional( $cond, $trueVal, $falseVal ) {
2651                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2652         }
2653
2654         /**
2655          * Returns a comand for str_replace function in SQL query.
2656          * Uses REPLACE() in MySQL
2657          *
2658          * @param $orig String: column to modify
2659          * @param $old String: column to seek
2660          * @param $new String: column to replace with
2661          *
2662          * @return string
2663          */
2664         function strreplace( $orig, $old, $new ) {
2665                 return "REPLACE({$orig}, {$old}, {$new})";
2666         }
2667
2668         /**
2669          * Determines if the last failure was due to a deadlock
2670          * STUB
2671          *
2672          * @return bool
2673          */
2674         function wasDeadlock() {
2675                 return false;
2676         }
2677
2678         /**
2679          * Determines if the last query error was something that should be dealt
2680          * with by pinging the connection and reissuing the query.
2681          * STUB
2682          *
2683          * @return bool
2684          */
2685         function wasErrorReissuable() {
2686                 return false;
2687         }
2688
2689         /**
2690          * Determines if the last failure was due to the database being read-only.
2691          * STUB
2692          *
2693          * @return bool
2694          */
2695         function wasReadOnlyError() {
2696                 return false;
2697         }
2698
2699         /**
2700          * Perform a deadlock-prone transaction.
2701          *
2702          * This function invokes a callback function to perform a set of write
2703          * queries. If a deadlock occurs during the processing, the transaction
2704          * will be rolled back and the callback function will be called again.
2705          *
2706          * Usage:
2707          *   $dbw->deadlockLoop( callback, ... );
2708          *
2709          * Extra arguments are passed through to the specified callback function.
2710          *
2711          * Returns whatever the callback function returned on its successful,
2712          * iteration, or false on error, for example if the retry limit was
2713          * reached.
2714          *
2715          * @return bool
2716          */
2717         function deadlockLoop() {
2718                 $myFname = 'DatabaseBase::deadlockLoop';
2719
2720                 $this->begin();
2721                 $args = func_get_args();
2722                 $function = array_shift( $args );
2723                 $oldIgnore = $this->ignoreErrors( true );
2724                 $tries = DEADLOCK_TRIES;
2725
2726                 if ( is_array( $function ) ) {
2727                         $fname = $function[0];
2728                 } else {
2729                         $fname = $function;
2730                 }
2731
2732                 do {
2733                         $retVal = call_user_func_array( $function, $args );
2734                         $error = $this->lastError();
2735                         $errno = $this->lastErrno();
2736                         $sql = $this->lastQuery();
2737
2738                         if ( $errno ) {
2739                                 if ( $this->wasDeadlock() ) {
2740                                         # Retry
2741                                         usleep( mt_rand( DEADLOCK_DELAY_MIN, DEADLOCK_DELAY_MAX ) );
2742                                 } else {
2743                                         $this->reportQueryError( $error, $errno, $sql, $fname );
2744                                 }
2745                         }
2746                 } while ( $this->wasDeadlock() && --$tries > 0 );
2747
2748                 $this->ignoreErrors( $oldIgnore );
2749
2750                 if ( $tries <= 0 ) {
2751                         $this->rollback( $myFname );
2752                         $this->reportQueryError( $error, $errno, $sql, $fname );
2753                         return false;
2754                 } else {
2755                         $this->commit( $myFname );
2756                         return $retVal;
2757                 }
2758         }
2759
2760         /**
2761          * Wait for the slave to catch up to a given master position.
2762          *
2763          * @param $pos DBMasterPos object
2764          * @param $timeout Integer: the maximum number of seconds to wait for
2765          *   synchronisation
2766          *
2767          * @return An integer: zero if the slave was past that position already,
2768          *   greater than zero if we waited for some period of time, less than
2769          *   zero if we timed out.
2770          */
2771         function masterPosWait( DBMasterPos $pos, $timeout ) {
2772                 $fname = 'DatabaseBase::masterPosWait';
2773                 wfProfileIn( $fname );
2774
2775                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2776                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
2777
2778                         if ( $wait > $timeout * 1e6 ) {
2779                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
2780                                 wfProfileOut( $fname );
2781                                 return -1;
2782                         } elseif ( $wait > 0 ) {
2783                                 wfDebug( "Fake slave waiting $wait us\n" );
2784                                 usleep( $wait );
2785                                 wfProfileOut( $fname );
2786                                 return 1;
2787                         } else {
2788                                 wfDebug( "Fake slave up to date ($wait us)\n" );
2789                                 wfProfileOut( $fname );
2790                                 return 0;
2791                         }
2792                 }
2793
2794                 wfProfileOut( $fname );
2795
2796                 # Real waits are implemented in the subclass.
2797                 return 0;
2798         }
2799
2800         /**
2801          * Get the replication position of this slave
2802          *
2803          * @return DBMasterPos, or false if this is not a slave.
2804          */
2805         function getSlavePos() {
2806                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2807                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
2808                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
2809                         return $pos;
2810                 } else {
2811                         # Stub
2812                         return false;
2813                 }
2814         }
2815
2816         /**
2817          * Get the position of this master
2818          *
2819          * @return DBMasterPos, or false if this is not a master
2820          */
2821         function getMasterPos() {
2822                 if ( $this->mFakeMaster ) {
2823                         return new MySQLMasterPos( 'fake', microtime( true ) );
2824                 } else {
2825                         return false;
2826                 }
2827         }
2828
2829         /**
2830          * Begin a transaction, committing any previously open transaction
2831          *
2832          * @param $fname string
2833          */
2834         function begin( $fname = 'DatabaseBase::begin' ) {
2835                 $this->query( 'BEGIN', $fname );
2836                 $this->mTrxLevel = 1;
2837         }
2838
2839         /**
2840          * End a transaction
2841          *
2842          * @param $fname string
2843          */
2844         function commit( $fname = 'DatabaseBase::commit' ) {
2845                 if ( $this->mTrxLevel ) {
2846                         $this->query( 'COMMIT', $fname );
2847                         $this->mTrxLevel = 0;
2848                 }
2849         }
2850
2851         /**
2852          * Rollback a transaction.
2853          * No-op on non-transactional databases.
2854          *
2855          * @param $fname string
2856          */
2857         function rollback( $fname = 'DatabaseBase::rollback' ) {
2858                 if ( $this->mTrxLevel ) {
2859                         $this->query( 'ROLLBACK', $fname, true );
2860                         $this->mTrxLevel = 0;
2861                 }
2862         }
2863
2864         /**
2865          * Creates a new table with structure copied from existing table
2866          * Note that unlike most database abstraction functions, this function does not
2867          * automatically append database prefix, because it works at a lower
2868          * abstraction level.
2869          * The table names passed to this function shall not be quoted (this
2870          * function calls addIdentifierQuotes when needed).
2871          *
2872          * @param $oldName String: name of table whose structure should be copied
2873          * @param $newName String: name of table to be created
2874          * @param $temporary Boolean: whether the new table should be temporary
2875          * @param $fname String: calling function name
2876          * @return Boolean: true if operation was successful
2877          */
2878         function duplicateTableStructure( $oldName, $newName, $temporary = false,
2879                 $fname = 'DatabaseBase::duplicateTableStructure' )
2880         {
2881                 throw new MWException(
2882                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
2883         }
2884
2885         /**
2886          * List all tables on the database
2887          *
2888          * @param $prefix Only show tables with this prefix, e.g. mw_
2889          * @param $fname String: calling function name
2890          */
2891         function listTables( $prefix = null, $fname = 'DatabaseBase::listTables' ) {
2892                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
2893         }
2894
2895         /**
2896          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2897          * to the format used for inserting into timestamp fields in this DBMS.
2898          *
2899          * The result is unquoted, and needs to be passed through addQuotes()
2900          * before it can be included in raw SQL.
2901          *
2902          * @param $ts string|int
2903          *
2904          * @return string
2905          */
2906         function timestamp( $ts = 0 ) {
2907                 return wfTimestamp( TS_MW, $ts );
2908         }
2909
2910         /**
2911          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2912          * to the format used for inserting into timestamp fields in this DBMS. If
2913          * NULL is input, it is passed through, allowing NULL values to be inserted
2914          * into timestamp fields.
2915          *
2916          * The result is unquoted, and needs to be passed through addQuotes()
2917          * before it can be included in raw SQL.
2918          *
2919          * @param $ts string|int
2920          *
2921          * @return string
2922          */
2923         function timestampOrNull( $ts = null ) {
2924                 if ( is_null( $ts ) ) {
2925                         return null;
2926                 } else {
2927                         return $this->timestamp( $ts );
2928                 }
2929         }
2930
2931         /**
2932          * Take the result from a query, and wrap it in a ResultWrapper if
2933          * necessary. Boolean values are passed through as is, to indicate success
2934          * of write queries or failure.
2935          *
2936          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
2937          * resource, and it was necessary to call this function to convert it to
2938          * a wrapper. Nowadays, raw database objects are never exposed to external
2939          * callers, so this is unnecessary in external code. For compatibility with
2940          * old code, ResultWrapper objects are passed through unaltered.
2941          *
2942          * @param $result bool|ResultWrapper
2943          *
2944          * @param bool|ResultWrapper
2945          */
2946         function resultObject( $result ) {
2947                 if ( empty( $result ) ) {
2948                         return false;
2949                 } elseif ( $result instanceof ResultWrapper ) {
2950                         return $result;
2951                 } elseif ( $result === true ) {
2952                         // Successful write query
2953                         return $result;
2954                 } else {
2955                         return new ResultWrapper( $this, $result );
2956                 }
2957         }
2958
2959         /**
2960          * Return aggregated value alias
2961          *
2962          * @param $valuedata
2963          * @param $valuename string
2964          *
2965          * @return string
2966          */
2967         function aggregateValue ( $valuedata, $valuename = 'value' ) {
2968                 return $valuename;
2969         }
2970
2971         /**
2972          * Ping the server and try to reconnect if it there is no connection
2973          *
2974          * @return bool Success or failure
2975          */
2976         function ping() {
2977                 # Stub.  Not essential to override.
2978                 return true;
2979         }
2980
2981         /**
2982          * Get slave lag. Currently supported only by MySQL.
2983          *
2984          * Note that this function will generate a fatal error on many
2985          * installations. Most callers should use LoadBalancer::safeGetLag()
2986          * instead.
2987          *
2988          * @return Database replication lag in seconds
2989          */
2990         function getLag() {
2991                 return intval( $this->mFakeSlaveLag );
2992         }
2993
2994         /**
2995          * Return the maximum number of items allowed in a list, or 0 for unlimited.
2996          *
2997          * @return int
2998          */
2999         function maxListLen() {
3000                 return 0;
3001         }
3002
3003         /**
3004          * Some DBMSs have a special format for inserting into blob fields, they
3005          * don't allow simple quoted strings to be inserted. To insert into such
3006          * a field, pass the data through this function before passing it to
3007          * DatabaseBase::insert().
3008          */
3009         function encodeBlob( $b ) {
3010                 return $b;
3011         }
3012
3013         /**
3014          * Some DBMSs return a special placeholder object representing blob fields
3015          * in result objects. Pass the object through this function to return the
3016          * original string.
3017          */
3018         function decodeBlob( $b ) {
3019                 return $b;
3020         }
3021
3022         /**
3023          * Override database's default connection timeout.  May be useful for very
3024          * long batch queries such as full-wiki dumps, where a single query reads
3025          * out over hours or days.  May or may not be necessary for non-MySQL
3026          * databases.  For most purposes, leaving it as a no-op should be fine.
3027          *
3028          * @param $timeout Integer in seconds
3029          */
3030         public function setTimeout( $timeout ) {}
3031
3032         /**
3033          * Read and execute SQL commands from a file.
3034          *
3035          * Returns true on success, error string or exception on failure (depending
3036          * on object's error ignore settings).
3037          *
3038          * @param $filename String: File name to open
3039          * @param $lineCallback Callback: Optional function called before reading each line
3040          * @param $resultCallback Callback: Optional function called for each MySQL result
3041          * @param $fname String: Calling function name or false if name should be
3042          *      generated dynamically using $filename
3043          */
3044         function sourceFile( $filename, $lineCallback = false, $resultCallback = false, $fname = false ) {
3045                 wfSuppressWarnings();
3046                 $fp = fopen( $filename, 'r' );
3047                 wfRestoreWarnings();
3048
3049                 if ( false === $fp ) {
3050                         throw new MWException( "Could not open \"{$filename}\".\n" );
3051                 }
3052
3053                 if ( !$fname ) {
3054                         $fname = __METHOD__ . "( $filename )";
3055                 }
3056
3057                 try {
3058                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname );
3059                 }
3060                 catch ( MWException $e ) {
3061                         fclose( $fp );
3062                         throw $e;
3063                 }
3064
3065                 fclose( $fp );
3066
3067                 return $error;
3068         }
3069
3070         /**
3071          * Get the full path of a patch file. Originally based on archive()
3072          * from updaters.inc. Keep in mind this always returns a patch, as
3073          * it fails back to MySQL if no DB-specific patch can be found
3074          *
3075          * @param $patch String The name of the patch, like patch-something.sql
3076          * @return String Full path to patch file
3077          */
3078         public function patchPath( $patch ) {
3079                 global $IP;
3080
3081                 $dbType = $this->getType();
3082                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3083                         return "$IP/maintenance/$dbType/archives/$patch";
3084                 } else {
3085                         return "$IP/maintenance/archives/$patch";
3086                 }
3087         }
3088
3089         /**
3090          * Set variables to be used in sourceFile/sourceStream, in preference to the
3091          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3092          * all. If it's set to false, $GLOBALS will be used.
3093          *
3094          * @param $vars False, or array mapping variable name to value.
3095          */
3096         function setSchemaVars( $vars ) {
3097                 $this->mSchemaVars = $vars;
3098         }
3099
3100         /**
3101          * Read and execute commands from an open file handle.
3102          *
3103          * Returns true on success, error string or exception on failure (depending
3104          * on object's error ignore settings).
3105          *
3106          * @param $fp Resource: File handle
3107          * @param $lineCallback Callback: Optional function called before reading each line
3108          * @param $resultCallback Callback: Optional function called for each MySQL result
3109          * @param $fname String: Calling function name
3110          */
3111         function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3112                 $fname = 'DatabaseBase::sourceStream' )
3113         {
3114                 $cmd = "";
3115                 $done = false;
3116                 $dollarquote = false;
3117
3118                 while ( ! feof( $fp ) ) {
3119                         if ( $lineCallback ) {
3120                                 call_user_func( $lineCallback );
3121                         }
3122
3123                         $line = trim( fgets( $fp ) );
3124                         $sl = strlen( $line ) - 1;
3125
3126                         if ( $sl < 0 ) {
3127                                 continue;
3128                         }
3129
3130                         if ( '-' == $line { 0 } && '-' == $line { 1 } ) {
3131                                 continue;
3132                         }
3133
3134                         # # Allow dollar quoting for function declarations
3135                         if ( substr( $line, 0, 4 ) == '$mw$' ) {
3136                                 if ( $dollarquote ) {
3137                                         $dollarquote = false;
3138                                         $done = true;
3139                                 }
3140                                 else {
3141                                         $dollarquote = true;
3142                                 }
3143                         }
3144                         elseif ( !$dollarquote ) {
3145                                 if ( ';' == $line { $sl } && ( $sl < 2 || ';' != $line { $sl - 1 } ) ) {
3146                                         $done = true;
3147                                         $line = substr( $line, 0, $sl );
3148                                 }
3149                         }
3150
3151                         if ( $cmd != '' ) {
3152                                 $cmd .= ' ';
3153                         }
3154
3155                         $cmd .= "$line\n";
3156
3157                         if ( $done ) {
3158                                 $cmd = str_replace( ';;', ";", $cmd );
3159                                 $cmd = $this->replaceVars( $cmd );
3160                                 $res = $this->query( $cmd, $fname );
3161
3162                                 if ( $resultCallback ) {
3163                                         call_user_func( $resultCallback, $res, $this );
3164                                 }
3165
3166                                 if ( false === $res ) {
3167                                         $err = $this->lastError();
3168                                         return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3169                                 }
3170
3171                                 $cmd = '';
3172                                 $done = false;
3173                         }
3174                 }
3175
3176                 return true;
3177         }
3178
3179         /**
3180          * Database independent variable replacement. Replaces a set of variables
3181          * in an SQL statement with their contents as given by $this->getSchemaVars().
3182          *
3183          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3184          *
3185          * - '{$var}' should be used for text and is passed through the database's
3186          *   addQuotes method.
3187          * - `{$var}` should be used for identifiers (eg: table and database names),
3188          *   it is passed through the database's addIdentifierQuotes method which
3189          *   can be overridden if the database uses something other than backticks.
3190          * - / *$var* / is just encoded, besides traditional table prefix and
3191          *   table options its use should be avoided.
3192          *
3193          * @param $ins String: SQL statement to replace variables in
3194          * @return String The new SQL statement with variables replaced
3195          */
3196         protected function replaceSchemaVars( $ins ) {
3197                 $vars = $this->getSchemaVars();
3198                 foreach ( $vars as $var => $value ) {
3199                         // replace '{$var}'
3200                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3201                         // replace `{$var}`
3202                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3203                         // replace /*$var*/
3204                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ) , $ins );
3205                 }
3206                 return $ins;
3207         }
3208
3209         /**
3210          * Replace variables in sourced SQL
3211          *
3212          * @param $ins string
3213          *
3214          * @return string
3215          */
3216         protected function replaceVars( $ins ) {
3217                 $ins = $this->replaceSchemaVars( $ins );
3218
3219                 // Table prefixes
3220                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3221                         array( $this, 'tableNameCallback' ), $ins );
3222
3223                 // Index names
3224                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3225                         array( $this, 'indexNameCallback' ), $ins );
3226
3227                 return $ins;
3228         }
3229
3230         /**
3231          * Get schema variables. If none have been set via setSchemaVars(), then
3232          * use some defaults from the current object.
3233          */
3234         protected function getSchemaVars() {
3235                 if ( $this->mSchemaVars ) {
3236                         return $this->mSchemaVars;
3237                 } else {
3238                         return $this->getDefaultSchemaVars();
3239                 }
3240         }
3241
3242         /**
3243          * Get schema variables to use if none have been set via setSchemaVars().
3244          *
3245          * Override this in derived classes to provide variables for tables.sql
3246          * and SQL patch files.
3247          *
3248          * @return array
3249          */
3250         protected function getDefaultSchemaVars() {
3251                 return array();
3252         }
3253
3254         /**
3255          * Table name callback
3256          *
3257          * @param $matches array
3258          *
3259          * @return string
3260          */
3261         protected function tableNameCallback( $matches ) {
3262                 return $this->tableName( $matches[1] );
3263         }
3264
3265         /**
3266          * Index name callback
3267          *
3268          * @param $matches array
3269          *
3270          * @return string
3271          */
3272         protected function indexNameCallback( $matches ) {
3273                 return $this->indexName( $matches[1] );
3274         }
3275
3276         /**
3277          * Build a concatenation list to feed into a SQL query
3278          * @param $stringList Array: list of raw SQL expressions; caller is responsible for any quoting
3279          * @return String
3280          */
3281         function buildConcat( $stringList ) {
3282                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
3283         }
3284
3285         /**
3286          * Acquire a named lock
3287          *
3288          * Abstracted from Filestore::lock() so child classes can implement for
3289          * their own needs.
3290          *
3291          * @param $lockName String: name of lock to aquire
3292          * @param $method String: name of method calling us
3293          * @param $timeout Integer: timeout
3294          * @return Boolean
3295          */
3296         public function lock( $lockName, $method, $timeout = 5 ) {
3297                 return true;
3298         }
3299
3300         /**
3301          * Release a lock.
3302          *
3303          * @param $lockName String: Name of lock to release
3304          * @param $method String: Name of method calling us
3305          *
3306          * @return Returns 1 if the lock was released, 0 if the lock was not established
3307          * by this thread (in which case the lock is not released), and NULL if the named
3308          * lock did not exist
3309          */
3310         public function unlock( $lockName, $method ) {
3311                 return true;
3312         }
3313
3314         /**
3315          * Lock specific tables
3316          *
3317          * @param $read Array of tables to lock for read access
3318          * @param $write Array of tables to lock for write access
3319          * @param $method String name of caller
3320          * @param $lowPriority bool Whether to indicate writes to be LOW PRIORITY
3321          *
3322          * @return bool
3323          */
3324         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3325                 return true;
3326         }
3327
3328         /**
3329          * Unlock specific tables
3330          *
3331          * @param $method String the caller
3332          *
3333          * @return bool
3334          */
3335         public function unlockTables( $method ) {
3336                 return true;
3337         }
3338
3339         /**
3340          * Delete a table
3341          * @param $tableName string
3342          * @param $fName string
3343          * @return bool|ResultWrapper
3344          */
3345         public function dropTable( $tableName, $fName = 'DatabaseBase::dropTable' ) {
3346                 if( !$this->tableExists( $tableName ) ) {
3347                         return false;
3348                 }
3349                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3350                 if( $this->cascadingDeletes() ) {
3351                         $sql .= " CASCADE";
3352                 }
3353                 return $this->query( $sql, $fName );
3354         }
3355
3356         /**
3357          * Get search engine class. All subclasses of this need to implement this
3358          * if they wish to use searching.
3359          *
3360          * @return String
3361          */
3362         public function getSearchEngine() {
3363                 return 'SearchEngineDummy';
3364         }
3365
3366         /**
3367          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3368          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3369          * because "i" sorts after all numbers.
3370          *
3371          * @return String
3372          */
3373         public function getInfinity() {
3374                 return 'infinity';
3375         }
3376
3377         /**
3378          * Encode an expiry time
3379          *
3380          * @param $expiry String: timestamp for expiry, or the 'infinity' string
3381          * @return String
3382          */
3383         public function encodeExpiry( $expiry ) {
3384                 if ( $expiry == '' || $expiry == $this->getInfinity() ) {
3385                         return $this->getInfinity();
3386                 } else {
3387                         return $this->timestamp( $expiry );
3388                 }
3389         }
3390
3391         /**
3392          * Allow or deny "big selects" for this session only. This is done by setting
3393          * the sql_big_selects session variable.
3394          *
3395          * This is a MySQL-specific feature.
3396          *
3397          * @param $value Mixed: true for allow, false for deny, or "default" to
3398          *   restore the initial value
3399          */
3400         public function setBigSelects( $value = true ) {
3401                 // no-op
3402         }
3403 }