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          * Bitwise operations
1821          */
1822
1823         /**
1824          * @param $field
1825          * @return string
1826          */
1827         function bitNot( $field ) {
1828                 return "(~$field)";
1829         }
1830
1831         /**
1832          * @param $fieldLeft
1833          * @param $fieldRight
1834          * @return string
1835          */
1836         function bitAnd( $fieldLeft, $fieldRight ) {
1837                 return "($fieldLeft & $fieldRight)";
1838         }
1839
1840         /**
1841          * @param  $fieldLeft
1842          * @param  $fieldRight
1843          * @return string
1844          */
1845         function bitOr( $fieldLeft, $fieldRight ) {
1846                 return "($fieldLeft | $fieldRight)";
1847         }
1848
1849         /**
1850          * Change the current database
1851          *
1852          * @todo Explain what exactly will fail if this is not overridden.
1853          *
1854          * @param $db
1855          *
1856          * @return bool Success or failure
1857          */
1858         function selectDB( $db ) {
1859                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
1860                 # if your database engine supports a concept similar to MySQL's
1861                 # databases you may as well.
1862                 $this->mDBname = $db;
1863                 return true;
1864         }
1865
1866         /**
1867          * Get the current DB name
1868          */
1869         function getDBname() {
1870                 return $this->mDBname;
1871         }
1872
1873         /**
1874          * Get the server hostname or IP address
1875          */
1876         function getServer() {
1877                 return $this->mServer;
1878         }
1879
1880         /**
1881          * Format a table name ready for use in constructing an SQL query
1882          *
1883          * This does two important things: it quotes the table names to clean them up,
1884          * and it adds a table prefix if only given a table name with no quotes.
1885          *
1886          * All functions of this object which require a table name call this function
1887          * themselves. Pass the canonical name to such functions. This is only needed
1888          * when calling query() directly.
1889          *
1890          * @param $name String: database table name
1891          * @param $format String One of:
1892          *   quoted - Automatically pass the table name through addIdentifierQuotes()
1893          *            so that it can be used in a query.
1894          *   raw - Do not add identifier quotes to the table name
1895          * @return String: full database name
1896          */
1897         function tableName( $name, $format = 'quoted' ) {
1898                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
1899                 # Skip the entire process when we have a string quoted on both ends.
1900                 # Note that we check the end so that we will still quote any use of
1901                 # use of `database`.table. But won't break things if someone wants
1902                 # to query a database table with a dot in the name.
1903                 if ( $this->isQuotedIdentifier( $name ) ) {
1904                         return $name;
1905                 }
1906
1907                 # Lets test for any bits of text that should never show up in a table
1908                 # name. Basically anything like JOIN or ON which are actually part of
1909                 # SQL queries, but may end up inside of the table value to combine
1910                 # sql. Such as how the API is doing.
1911                 # Note that we use a whitespace test rather than a \b test to avoid
1912                 # any remote case where a word like on may be inside of a table name
1913                 # surrounded by symbols which may be considered word breaks.
1914                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1915                         return $name;
1916                 }
1917
1918                 # Split database and table into proper variables.
1919                 # We reverse the explode so that database.table and table both output
1920                 # the correct table.
1921                 $dbDetails = array_reverse( explode( '.', $name, 2 ) );
1922                 if ( isset( $dbDetails[1] ) ) {
1923                         list( $table, $database ) = $dbDetails;
1924                 } else {
1925                         list( $table ) = $dbDetails;
1926                 }
1927                 $prefix = $this->mTablePrefix; # Default prefix
1928
1929                 # A database name has been specified in input. We don't want any
1930                 # prefixes added.
1931                 if ( isset( $database ) ) {
1932                         $prefix = '';
1933                 }
1934
1935                 # Note that we use the long format because php will complain in in_array if
1936                 # the input is not an array, and will complain in is_array if it is not set.
1937                 if ( !isset( $database ) # Don't use shared database if pre selected.
1938                  && isset( $wgSharedDB ) # We have a shared database
1939                  && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
1940                  && isset( $wgSharedTables )
1941                  && is_array( $wgSharedTables )
1942                  && in_array( $table, $wgSharedTables ) ) { # A shared table is selected
1943                         $database = $wgSharedDB;
1944                         $prefix   = isset( $wgSharedPrefix ) ? $wgSharedPrefix : $prefix;
1945                 }
1946
1947                 # Quote the $database and $table and apply the prefix if not quoted.
1948                 if ( isset( $database ) ) {
1949                         $database = ( $format == 'quoted' || $this->isQuotedIdentifier( $database ) ? $database : $this->addIdentifierQuotes( $database ) );
1950                 }
1951
1952                 $table = "{$prefix}{$table}";
1953                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $table ) ) {
1954                         $table = $this->addIdentifierQuotes( "{$table}" );
1955                 }
1956
1957                 # Merge our database and table into our final table name.
1958                 $tableName = ( isset( $database ) ? "{$database}.{$table}" : "{$table}" );
1959
1960                 return $tableName;
1961         }
1962
1963         /**
1964          * Fetch a number of table names into an array
1965          * This is handy when you need to construct SQL for joins
1966          *
1967          * Example:
1968          * extract($dbr->tableNames('user','watchlist'));
1969          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
1970          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
1971          *
1972          * @return array
1973          */
1974         public function tableNames() {
1975                 $inArray = func_get_args();
1976                 $retVal = array();
1977
1978                 foreach ( $inArray as $name ) {
1979                         $retVal[$name] = $this->tableName( $name );
1980                 }
1981
1982                 return $retVal;
1983         }
1984
1985         /**
1986          * Fetch a number of table names into an zero-indexed numerical array
1987          * This is handy when you need to construct SQL for joins
1988          *
1989          * Example:
1990          * list( $user, $watchlist ) = $dbr->tableNamesN('user','watchlist');
1991          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
1992          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
1993          *
1994          * @return array
1995          */
1996         public function tableNamesN() {
1997                 $inArray = func_get_args();
1998                 $retVal = array();
1999
2000                 foreach ( $inArray as $name ) {
2001                         $retVal[] = $this->tableName( $name );
2002                 }
2003
2004                 return $retVal;
2005         }
2006
2007         /**
2008          * Get an aliased table name
2009          * e.g. tableName AS newTableName
2010          *
2011          * @param $name string Table name, see tableName()
2012          * @param $alias string|bool Alias (optional)
2013          * @return string SQL name for aliased table. Will not alias a table to its own name
2014          */
2015         public function tableNameWithAlias( $name, $alias = false ) {
2016                 if ( !$alias || $alias == $name ) {
2017                         return $this->tableName( $name );
2018                 } else {
2019                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2020                 }
2021         }
2022
2023         /**
2024          * Gets an array of aliased table names
2025          *
2026          * @param $tables array( [alias] => table )
2027          * @return array of strings, see tableNameWithAlias()
2028          */
2029         public function tableNamesWithAlias( $tables ) {
2030                 $retval = array();
2031                 foreach ( $tables as $alias => $table ) {
2032                         if ( is_numeric( $alias ) ) {
2033                                 $alias = $table;
2034                         }
2035                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2036                 }
2037                 return $retval;
2038         }
2039
2040         /**
2041          * Get the aliased table name clause for a FROM clause
2042          * which might have a JOIN and/or USE INDEX clause
2043          *
2044          * @param $tables array ( [alias] => table )
2045          * @param $use_index array Same as for select()
2046          * @param $join_conds array Same as for select()
2047          * @return string
2048          */
2049         protected function tableNamesWithUseIndexOrJOIN(
2050                 $tables, $use_index = array(), $join_conds = array()
2051         ) {
2052                 $ret = array();
2053                 $retJOIN = array();
2054                 $use_index = (array)$use_index;
2055                 $join_conds = (array)$join_conds;
2056
2057                 foreach ( $tables as $alias => $table ) {
2058                         if ( !is_string( $alias ) ) {
2059                                 // No alias? Set it equal to the table name
2060                                 $alias = $table;
2061                         }
2062                         // Is there a JOIN clause for this table?
2063                         if ( isset( $join_conds[$alias] ) ) {
2064                                 list( $joinType, $conds ) = $join_conds[$alias];
2065                                 $tableClause = $joinType;
2066                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2067                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2068                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2069                                         if ( $use != '' ) {
2070                                                 $tableClause .= ' ' . $use;
2071                                         }
2072                                 }
2073                                 $on = $this->makeList( (array)$conds, LIST_AND );
2074                                 if ( $on != '' ) {
2075                                         $tableClause .= ' ON (' . $on . ')';
2076                                 }
2077
2078                                 $retJOIN[] = $tableClause;
2079                         // Is there an INDEX clause for this table?
2080                         } elseif ( isset( $use_index[$alias] ) ) {
2081                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2082                                 $tableClause .= ' ' . $this->useIndexClause(
2083                                         implode( ',', (array)$use_index[$alias] ) );
2084
2085                                 $ret[] = $tableClause;
2086                         } else {
2087                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2088
2089                                 $ret[] = $tableClause;
2090                         }
2091                 }
2092
2093                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2094                 $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2095                 $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2096
2097                 // Compile our final table clause
2098                 return implode( ' ', array( $straightJoins, $otherJoins ) );
2099         }
2100
2101         /**
2102          * Get the name of an index in a given table
2103          *
2104          * @param $index
2105          *
2106          * @return string
2107          */
2108         function indexName( $index ) {
2109                 // Backwards-compatibility hack
2110                 $renamed = array(
2111                         'ar_usertext_timestamp' => 'usertext_timestamp',
2112                         'un_user_id'            => 'user_id',
2113                         'un_user_ip'            => 'user_ip',
2114                 );
2115
2116                 if ( isset( $renamed[$index] ) ) {
2117                         return $renamed[$index];
2118                 } else {
2119                         return $index;
2120                 }
2121         }
2122
2123         /**
2124          * If it's a string, adds quotes and backslashes
2125          * Otherwise returns as-is
2126          *
2127          * @param $s string
2128          *
2129          * @return string
2130          */
2131         function addQuotes( $s ) {
2132                 if ( $s === null ) {
2133                         return 'NULL';
2134                 } else {
2135                         # This will also quote numeric values. This should be harmless,
2136                         # and protects against weird problems that occur when they really
2137                         # _are_ strings such as article titles and string->number->string
2138                         # conversion is not 1:1.
2139                         return "'" . $this->strencode( $s ) . "'";
2140                 }
2141         }
2142
2143         /**
2144          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2145          * MySQL uses `backticks` while basically everything else uses double quotes.
2146          * Since MySQL is the odd one out here the double quotes are our generic
2147          * and we implement backticks in DatabaseMysql.
2148          *
2149          * @param $s string
2150          *
2151          * @return string
2152          */
2153         public function addIdentifierQuotes( $s ) {
2154                 return '"' . str_replace( '"', '""', $s ) . '"';
2155         }
2156
2157         /**
2158          * Returns if the given identifier looks quoted or not according to
2159          * the database convention for quoting identifiers .
2160          *
2161          * @param $name string
2162          *
2163          * @return boolean
2164          */
2165         public function isQuotedIdentifier( $name ) {
2166                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2167         }
2168
2169         /**
2170          * Backwards compatibility, identifier quoting originated in DatabasePostgres
2171          * which used quote_ident which does not follow our naming conventions
2172          * was renamed to addIdentifierQuotes.
2173          * @deprecated since 1.18 use addIdentifierQuotes
2174          *
2175          * @param $s string
2176          *
2177          * @return string
2178          */
2179         function quote_ident( $s ) {
2180                 wfDeprecated( __METHOD__ );
2181                 return $this->addIdentifierQuotes( $s );
2182         }
2183
2184         /**
2185          * Escape string for safe LIKE usage.
2186          * WARNING: you should almost never use this function directly,
2187          * instead use buildLike() that escapes everything automatically
2188          * @deprecated since 1.17, warnings in 1.17, removed in ???
2189          *
2190          * @param $s string
2191          *
2192          * @return string
2193          */
2194         public function escapeLike( $s ) {
2195                 wfDeprecated( __METHOD__ );
2196                 return $this->escapeLikeInternal( $s );
2197         }
2198
2199         /**
2200          * @param $s string
2201          * @return string
2202          */
2203         protected function escapeLikeInternal( $s ) {
2204                 $s = str_replace( '\\', '\\\\', $s );
2205                 $s = $this->strencode( $s );
2206                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2207
2208                 return $s;
2209         }
2210
2211         /**
2212          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2213          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2214          * Alternatively, the function could be provided with an array of aforementioned parameters.
2215          *
2216          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2217          * for subpages of 'My page title'.
2218          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2219          *
2220          * @since 1.16
2221          * @return String: fully built LIKE statement
2222          */
2223         function buildLike() {
2224                 $params = func_get_args();
2225
2226                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2227                         $params = $params[0];
2228                 }
2229
2230                 $s = '';
2231
2232                 foreach ( $params as $value ) {
2233                         if ( $value instanceof LikeMatch ) {
2234                                 $s .= $value->toString();
2235                         } else {
2236                                 $s .= $this->escapeLikeInternal( $value );
2237                         }
2238                 }
2239
2240                 return " LIKE '" . $s . "' ";
2241         }
2242
2243         /**
2244          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2245          *
2246          * @return LikeMatch
2247          */
2248         function anyChar() {
2249                 return new LikeMatch( '_' );
2250         }
2251
2252         /**
2253          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2254          *
2255          * @return LikeMatch
2256          */
2257         function anyString() {
2258                 return new LikeMatch( '%' );
2259         }
2260
2261         /**
2262          * Returns an appropriately quoted sequence value for inserting a new row.
2263          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2264          * subclass will return an integer, and save the value for insertId()
2265          */
2266         function nextSequenceValue( $seqName ) {
2267                 return null;
2268         }
2269
2270         /**
2271          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2272          * is only needed because a) MySQL must be as efficient as possible due to
2273          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2274          * which index to pick.  Anyway, other databases might have different
2275          * indexes on a given table.  So don't bother overriding this unless you're
2276          * MySQL.
2277          */
2278         function useIndexClause( $index ) {
2279                 return '';
2280         }
2281
2282         /**
2283          * REPLACE query wrapper.
2284          *
2285          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2286          * except that when there is a duplicate key error, the old row is deleted
2287          * and the new row is inserted in its place.
2288          *
2289          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2290          * perform the delete, we need to know what the unique indexes are so that
2291          * we know how to find the conflicting rows.
2292          *
2293          * It may be more efficient to leave off unique indexes which are unlikely
2294          * to collide. However if you do this, you run the risk of encountering
2295          * errors which wouldn't have occurred in MySQL.
2296          *
2297          * @param $table String: The table to replace the row(s) in.
2298          * @param $rows array Can be either a single row to insert, or multiple rows,
2299          *    in the same format as for DatabaseBase::insert()
2300          * @param $uniqueIndexes array is an array of indexes. Each element may be either
2301          *    a field name or an array of field names
2302          * @param $fname String: Calling function name (use __METHOD__) for logs/profiling
2303          */
2304         function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseBase::replace' ) {
2305                 $quotedTable = $this->tableName( $table );
2306
2307                 if ( count( $rows ) == 0 ) {
2308                         return;
2309                 }
2310
2311                 # Single row case
2312                 if ( !is_array( reset( $rows ) ) ) {
2313                         $rows = array( $rows );
2314                 }
2315
2316                 foreach( $rows as $row ) {
2317                         # Delete rows which collide
2318                         if ( $uniqueIndexes ) {
2319                                 $sql = "DELETE FROM $quotedTable WHERE ";
2320                                 $first = true;
2321                                 foreach ( $uniqueIndexes as $index ) {
2322                                         if ( $first ) {
2323                                                 $first = false;
2324                                                 $sql .= '( ';
2325                                         } else {
2326                                                 $sql .= ' ) OR ( ';
2327                                         }
2328                                         if ( is_array( $index ) ) {
2329                                                 $first2 = true;
2330                                                 foreach ( $index as $col ) {
2331                                                         if ( $first2 ) {
2332                                                                 $first2 = false;
2333                                                         } else {
2334                                                                 $sql .= ' AND ';
2335                                                         }
2336                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2337                                                 }
2338                                         } else {
2339                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2340                                         }
2341                                 }
2342                                 $sql .= ' )';
2343                                 $this->query( $sql, $fname );
2344                         }
2345
2346                         # Now insert the row
2347                         $this->insert( $table, $row );
2348                 }
2349         }
2350
2351         /**
2352          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2353          * statement.
2354          *
2355          * @param $table Table name
2356          * @param $rows Rows to insert
2357          * @param $fname Caller function name
2358          *
2359          * @return ResultWrapper
2360          */
2361         protected function nativeReplace( $table, $rows, $fname ) {
2362                 $table = $this->tableName( $table );
2363
2364                 # Single row case
2365                 if ( !is_array( reset( $rows ) ) ) {
2366                         $rows = array( $rows );
2367                 }
2368
2369                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2370                 $first = true;
2371
2372                 foreach ( $rows as $row ) {
2373                         if ( $first ) {
2374                                 $first = false;
2375                         } else {
2376                                 $sql .= ',';
2377                         }
2378
2379                         $sql .= '(' . $this->makeList( $row ) . ')';
2380                 }
2381
2382                 return $this->query( $sql, $fname );
2383         }
2384
2385         /**
2386          * DELETE where the condition is a join.
2387          *
2388          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2389          * we use sub-selects
2390          *
2391          * For safety, an empty $conds will not delete everything. If you want to
2392          * delete all rows where the join condition matches, set $conds='*'.
2393          *
2394          * DO NOT put the join condition in $conds.
2395          *
2396          * @param $delTable   String: The table to delete from.
2397          * @param $joinTable  String: The other table.
2398          * @param $delVar     String: The variable to join on, in the first table.
2399          * @param $joinVar    String: The variable to join on, in the second table.
2400          * @param $conds      Array: Condition array of field names mapped to variables,
2401          *                    ANDed together in the WHERE clause
2402          * @param $fname      String: Calling function name (use __METHOD__) for
2403          *                    logs/profiling
2404          */
2405         function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2406                 $fname = 'DatabaseBase::deleteJoin' )
2407         {
2408                 if ( !$conds ) {
2409                         throw new DBUnexpectedError( $this,
2410                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2411                 }
2412
2413                 $delTable = $this->tableName( $delTable );
2414                 $joinTable = $this->tableName( $joinTable );
2415                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2416                 if ( $conds != '*' ) {
2417                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2418                 }
2419                 $sql .= ')';
2420
2421                 $this->query( $sql, $fname );
2422         }
2423
2424         /**
2425          * Returns the size of a text field, or -1 for "unlimited"
2426          *
2427          * @param $table string
2428          * @param $field string
2429          *
2430          * @return int
2431          */
2432         function textFieldSize( $table, $field ) {
2433                 $table = $this->tableName( $table );
2434                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2435                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2436                 $row = $this->fetchObject( $res );
2437
2438                 $m = array();
2439
2440                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2441                         $size = $m[1];
2442                 } else {
2443                         $size = -1;
2444                 }
2445
2446                 return $size;
2447         }
2448
2449         /**
2450          * A string to insert into queries to show that they're low-priority, like
2451          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2452          * string and nothing bad should happen.
2453          *
2454          * @return string Returns the text of the low priority option if it is
2455          *   supported, or a blank string otherwise
2456          */
2457         function lowPriorityOption() {
2458                 return '';
2459         }
2460
2461         /**
2462          * DELETE query wrapper.
2463          *
2464          * @param $table Array Table name
2465          * @param $conds String|Array of conditions. See $conds in DatabaseBase::select() for
2466          *               the format. Use $conds == "*" to delete all rows
2467          * @param $fname String name of the calling function
2468          *
2469          * @return bool
2470          */
2471         function delete( $table, $conds, $fname = 'DatabaseBase::delete' ) {
2472                 if ( !$conds ) {
2473                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2474                 }
2475
2476                 $table = $this->tableName( $table );
2477                 $sql = "DELETE FROM $table";
2478
2479                 if ( $conds != '*' ) {
2480                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2481                 }
2482
2483                 return $this->query( $sql, $fname );
2484         }
2485
2486         /**
2487          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2488          * into another table.
2489          *
2490          * @param $destTable string The table name to insert into
2491          * @param $srcTable string|array May be either a table name, or an array of table names
2492          *    to include in a join.
2493          *
2494          * @param $varMap array must be an associative array of the form
2495          *    array( 'dest1' => 'source1', ...). Source items may be literals
2496          *    rather than field names, but strings should be quoted with
2497          *    DatabaseBase::addQuotes()
2498          *
2499          * @param $conds array Condition array. See $conds in DatabaseBase::select() for
2500          *    the details of the format of condition arrays. May be "*" to copy the
2501          *    whole table.
2502          *
2503          * @param $fname string The function name of the caller, from __METHOD__
2504          *
2505          * @param $insertOptions array Options for the INSERT part of the query, see
2506          *    DatabaseBase::insert() for details.
2507          * @param $selectOptions array Options for the SELECT part of the query, see
2508          *    DatabaseBase::select() for details.
2509          *
2510          * @return ResultWrapper
2511          */
2512         function insertSelect( $destTable, $srcTable, $varMap, $conds,
2513                 $fname = 'DatabaseBase::insertSelect',
2514                 $insertOptions = array(), $selectOptions = array() )
2515         {
2516                 $destTable = $this->tableName( $destTable );
2517
2518                 if ( is_array( $insertOptions ) ) {
2519                         $insertOptions = implode( ' ', $insertOptions );
2520                 }
2521
2522                 if ( !is_array( $selectOptions ) ) {
2523                         $selectOptions = array( $selectOptions );
2524                 }
2525
2526                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2527
2528                 if ( is_array( $srcTable ) ) {
2529                         $srcTable =  implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2530                 } else {
2531                         $srcTable = $this->tableName( $srcTable );
2532                 }
2533
2534                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2535                         " SELECT $startOpts " . implode( ',', $varMap ) .
2536                         " FROM $srcTable $useIndex ";
2537
2538                 if ( $conds != '*' ) {
2539                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2540                 }
2541
2542                 $sql .= " $tailOpts";
2543
2544                 return $this->query( $sql, $fname );
2545         }
2546
2547         /**
2548          * Construct a LIMIT query with optional offset.  This is used for query
2549          * pages.  The SQL should be adjusted so that only the first $limit rows
2550          * are returned.  If $offset is provided as well, then the first $offset
2551          * rows should be discarded, and the next $limit rows should be returned.
2552          * If the result of the query is not ordered, then the rows to be returned
2553          * are theoretically arbitrary.
2554          *
2555          * $sql is expected to be a SELECT, if that makes a difference.  For
2556          * UPDATE, limitResultForUpdate should be used.
2557          *
2558          * The version provided by default works in MySQL and SQLite.  It will very
2559          * likely need to be overridden for most other DBMSes.
2560          *
2561          * @param $sql String SQL query we will append the limit too
2562          * @param $limit Integer the SQL limit
2563          * @param $offset Integer|false the SQL offset (default false)
2564          *
2565          * @return string
2566          */
2567         function limitResult( $sql, $limit, $offset = false ) {
2568                 if ( !is_numeric( $limit ) ) {
2569                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2570                 }
2571
2572                 return "$sql LIMIT "
2573                                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2574                                 . "{$limit} ";
2575         }
2576
2577         /**
2578          * @param $sql
2579          * @param $num
2580          * @return string
2581          */
2582         function limitResultForUpdate( $sql, $num ) {
2583                 return $this->limitResult( $sql, $num, 0 );
2584         }
2585
2586         /**
2587          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2588          * within the UNION construct.
2589          * @return Boolean
2590          */
2591         function unionSupportsOrderAndLimit() {
2592                 return true; // True for almost every DB supported
2593         }
2594
2595         /**
2596          * Construct a UNION query
2597          * This is used for providing overload point for other DB abstractions
2598          * not compatible with the MySQL syntax.
2599          * @param $sqls Array: SQL statements to combine
2600          * @param $all Boolean: use UNION ALL
2601          * @return String: SQL fragment
2602          */
2603         function unionQueries( $sqls, $all ) {
2604                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2605                 return '(' . implode( $glue, $sqls ) . ')';
2606         }
2607
2608         /**
2609          * Returns an SQL expression for a simple conditional.  This doesn't need
2610          * to be overridden unless CASE isn't supported in your DBMS.
2611          *
2612          * @param $cond String: SQL expression which will result in a boolean value
2613          * @param $trueVal String: SQL expression to return if true
2614          * @param $falseVal String: SQL expression to return if false
2615          * @return String: SQL fragment
2616          */
2617         function conditional( $cond, $trueVal, $falseVal ) {
2618                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2619         }
2620
2621         /**
2622          * Returns a comand for str_replace function in SQL query.
2623          * Uses REPLACE() in MySQL
2624          *
2625          * @param $orig String: column to modify
2626          * @param $old String: column to seek
2627          * @param $new String: column to replace with
2628          *
2629          * @return string
2630          */
2631         function strreplace( $orig, $old, $new ) {
2632                 return "REPLACE({$orig}, {$old}, {$new})";
2633         }
2634
2635         /**
2636          * Determines if the last failure was due to a deadlock
2637          * STUB
2638          *
2639          * @return bool
2640          */
2641         function wasDeadlock() {
2642                 return false;
2643         }
2644
2645         /**
2646          * Determines if the last query error was something that should be dealt
2647          * with by pinging the connection and reissuing the query.
2648          * STUB
2649          *
2650          * @return bool
2651          */
2652         function wasErrorReissuable() {
2653                 return false;
2654         }
2655
2656         /**
2657          * Determines if the last failure was due to the database being read-only.
2658          * STUB
2659          *
2660          * @return bool
2661          */
2662         function wasReadOnlyError() {
2663                 return false;
2664         }
2665
2666         /**
2667          * Perform a deadlock-prone transaction.
2668          *
2669          * This function invokes a callback function to perform a set of write
2670          * queries. If a deadlock occurs during the processing, the transaction
2671          * will be rolled back and the callback function will be called again.
2672          *
2673          * Usage:
2674          *   $dbw->deadlockLoop( callback, ... );
2675          *
2676          * Extra arguments are passed through to the specified callback function.
2677          *
2678          * Returns whatever the callback function returned on its successful,
2679          * iteration, or false on error, for example if the retry limit was
2680          * reached.
2681          *
2682          * @return bool
2683          */
2684         function deadlockLoop() {
2685                 $myFname = 'DatabaseBase::deadlockLoop';
2686
2687                 $this->begin();
2688                 $args = func_get_args();
2689                 $function = array_shift( $args );
2690                 $oldIgnore = $this->ignoreErrors( true );
2691                 $tries = DEADLOCK_TRIES;
2692
2693                 if ( is_array( $function ) ) {
2694                         $fname = $function[0];
2695                 } else {
2696                         $fname = $function;
2697                 }
2698
2699                 do {
2700                         $retVal = call_user_func_array( $function, $args );
2701                         $error = $this->lastError();
2702                         $errno = $this->lastErrno();
2703                         $sql = $this->lastQuery();
2704
2705                         if ( $errno ) {
2706                                 if ( $this->wasDeadlock() ) {
2707                                         # Retry
2708                                         usleep( mt_rand( DEADLOCK_DELAY_MIN, DEADLOCK_DELAY_MAX ) );
2709                                 } else {
2710                                         $this->reportQueryError( $error, $errno, $sql, $fname );
2711                                 }
2712                         }
2713                 } while ( $this->wasDeadlock() && --$tries > 0 );
2714
2715                 $this->ignoreErrors( $oldIgnore );
2716
2717                 if ( $tries <= 0 ) {
2718                         $this->rollback( $myFname );
2719                         $this->reportQueryError( $error, $errno, $sql, $fname );
2720                         return false;
2721                 } else {
2722                         $this->commit( $myFname );
2723                         return $retVal;
2724                 }
2725         }
2726
2727         /**
2728          * Wait for the slave to catch up to a given master position.
2729          *
2730          * @param $pos DBMasterPos object
2731          * @param $timeout Integer: the maximum number of seconds to wait for
2732          *   synchronisation
2733          *
2734          * @return An integer: zero if the slave was past that position already,
2735          *   greater than zero if we waited for some period of time, less than
2736          *   zero if we timed out.
2737          */
2738         function masterPosWait( DBMasterPos $pos, $timeout ) {
2739                 $fname = 'DatabaseBase::masterPosWait';
2740                 wfProfileIn( $fname );
2741
2742                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2743                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
2744
2745                         if ( $wait > $timeout * 1e6 ) {
2746                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
2747                                 wfProfileOut( $fname );
2748                                 return -1;
2749                         } elseif ( $wait > 0 ) {
2750                                 wfDebug( "Fake slave waiting $wait us\n" );
2751                                 usleep( $wait );
2752                                 wfProfileOut( $fname );
2753                                 return 1;
2754                         } else {
2755                                 wfDebug( "Fake slave up to date ($wait us)\n" );
2756                                 wfProfileOut( $fname );
2757                                 return 0;
2758                         }
2759                 }
2760
2761                 wfProfileOut( $fname );
2762
2763                 # Real waits are implemented in the subclass.
2764                 return 0;
2765         }
2766
2767         /**
2768          * Get the replication position of this slave
2769          *
2770          * @return DBMasterPos, or false if this is not a slave.
2771          */
2772         function getSlavePos() {
2773                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2774                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
2775                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
2776                         return $pos;
2777                 } else {
2778                         # Stub
2779                         return false;
2780                 }
2781         }
2782
2783         /**
2784          * Get the position of this master
2785          *
2786          * @return DBMasterPos, or false if this is not a master
2787          */
2788         function getMasterPos() {
2789                 if ( $this->mFakeMaster ) {
2790                         return new MySQLMasterPos( 'fake', microtime( true ) );
2791                 } else {
2792                         return false;
2793                 }
2794         }
2795
2796         /**
2797          * Begin a transaction, committing any previously open transaction
2798          *
2799          * @param $fname string
2800          */
2801         function begin( $fname = 'DatabaseBase::begin' ) {
2802                 $this->query( 'BEGIN', $fname );
2803                 $this->mTrxLevel = 1;
2804         }
2805
2806         /**
2807          * End a transaction
2808          *
2809          * @param $fname string
2810          */
2811         function commit( $fname = 'DatabaseBase::commit' ) {
2812                 if ( $this->mTrxLevel ) {
2813                         $this->query( 'COMMIT', $fname );
2814                         $this->mTrxLevel = 0;
2815                 }
2816         }
2817
2818         /**
2819          * Rollback a transaction.
2820          * No-op on non-transactional databases.
2821          *
2822          * @param $fname string
2823          */
2824         function rollback( $fname = 'DatabaseBase::rollback' ) {
2825                 if ( $this->mTrxLevel ) {
2826                         $this->query( 'ROLLBACK', $fname, true );
2827                         $this->mTrxLevel = 0;
2828                 }
2829         }
2830
2831         /**
2832          * Creates a new table with structure copied from existing table
2833          * Note that unlike most database abstraction functions, this function does not
2834          * automatically append database prefix, because it works at a lower
2835          * abstraction level.
2836          * The table names passed to this function shall not be quoted (this
2837          * function calls addIdentifierQuotes when needed).
2838          *
2839          * @param $oldName String: name of table whose structure should be copied
2840          * @param $newName String: name of table to be created
2841          * @param $temporary Boolean: whether the new table should be temporary
2842          * @param $fname String: calling function name
2843          * @return Boolean: true if operation was successful
2844          */
2845         function duplicateTableStructure( $oldName, $newName, $temporary = false,
2846                 $fname = 'DatabaseBase::duplicateTableStructure' )
2847         {
2848                 throw new MWException(
2849                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
2850         }
2851
2852         /**
2853          * List all tables on the database
2854          *
2855          * @param $prefix Only show tables with this prefix, e.g. mw_
2856          * @param $fname String: calling function name
2857          */
2858         function listTables( $prefix = null, $fname = 'DatabaseBase::listTables' ) {
2859                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
2860         }
2861
2862         /**
2863          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2864          * to the format used for inserting into timestamp fields in this DBMS.
2865          *
2866          * The result is unquoted, and needs to be passed through addQuotes()
2867          * before it can be included in raw SQL.
2868          *
2869          * @param $ts string|int
2870          *
2871          * @return string
2872          */
2873         function timestamp( $ts = 0 ) {
2874                 return wfTimestamp( TS_MW, $ts );
2875         }
2876
2877         /**
2878          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2879          * to the format used for inserting into timestamp fields in this DBMS. If
2880          * NULL is input, it is passed through, allowing NULL values to be inserted
2881          * into timestamp fields.
2882          *
2883          * The result is unquoted, and needs to be passed through addQuotes()
2884          * before it can be included in raw SQL.
2885          *
2886          * @param $ts string|int
2887          *
2888          * @return string
2889          */
2890         function timestampOrNull( $ts = null ) {
2891                 if ( is_null( $ts ) ) {
2892                         return null;
2893                 } else {
2894                         return $this->timestamp( $ts );
2895                 }
2896         }
2897
2898         /**
2899          * Take the result from a query, and wrap it in a ResultWrapper if
2900          * necessary. Boolean values are passed through as is, to indicate success
2901          * of write queries or failure.
2902          *
2903          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
2904          * resource, and it was necessary to call this function to convert it to
2905          * a wrapper. Nowadays, raw database objects are never exposed to external
2906          * callers, so this is unnecessary in external code. For compatibility with
2907          * old code, ResultWrapper objects are passed through unaltered.
2908          *
2909          * @param $result bool|ResultWrapper
2910          *
2911          * @param bool|ResultWrapper
2912          */
2913         function resultObject( $result ) {
2914                 if ( empty( $result ) ) {
2915                         return false;
2916                 } elseif ( $result instanceof ResultWrapper ) {
2917                         return $result;
2918                 } elseif ( $result === true ) {
2919                         // Successful write query
2920                         return $result;
2921                 } else {
2922                         return new ResultWrapper( $this, $result );
2923                 }
2924         }
2925
2926         /**
2927          * Return aggregated value alias
2928          *
2929          * @param $valuedata
2930          * @param $valuename string
2931          *
2932          * @return string
2933          */
2934         function aggregateValue ( $valuedata, $valuename = 'value' ) {
2935                 return $valuename;
2936         }
2937
2938         /**
2939          * Ping the server and try to reconnect if it there is no connection
2940          *
2941          * @return bool Success or failure
2942          */
2943         function ping() {
2944                 # Stub.  Not essential to override.
2945                 return true;
2946         }
2947
2948         /**
2949          * Get slave lag. Currently supported only by MySQL.
2950          *
2951          * Note that this function will generate a fatal error on many
2952          * installations. Most callers should use LoadBalancer::safeGetLag()
2953          * instead.
2954          *
2955          * @return Database replication lag in seconds
2956          */
2957         function getLag() {
2958                 return intval( $this->mFakeSlaveLag );
2959         }
2960
2961         /**
2962          * Return the maximum number of items allowed in a list, or 0 for unlimited.
2963          *
2964          * @return int
2965          */
2966         function maxListLen() {
2967                 return 0;
2968         }
2969
2970         /**
2971          * Some DBMSs have a special format for inserting into blob fields, they
2972          * don't allow simple quoted strings to be inserted. To insert into such
2973          * a field, pass the data through this function before passing it to
2974          * DatabaseBase::insert().
2975          */
2976         function encodeBlob( $b ) {
2977                 return $b;
2978         }
2979
2980         /**
2981          * Some DBMSs return a special placeholder object representing blob fields
2982          * in result objects. Pass the object through this function to return the
2983          * original string.
2984          */
2985         function decodeBlob( $b ) {
2986                 return $b;
2987         }
2988
2989         /**
2990          * Override database's default connection timeout.  May be useful for very
2991          * long batch queries such as full-wiki dumps, where a single query reads
2992          * out over hours or days.  May or may not be necessary for non-MySQL
2993          * databases.  For most purposes, leaving it as a no-op should be fine.
2994          *
2995          * @param $timeout Integer in seconds
2996          */
2997         public function setTimeout( $timeout ) {}
2998
2999         /**
3000          * Read and execute SQL commands from a file.
3001          *
3002          * Returns true on success, error string or exception on failure (depending
3003          * on object's error ignore settings).
3004          *
3005          * @param $filename String: File name to open
3006          * @param $lineCallback Callback: Optional function called before reading each line
3007          * @param $resultCallback Callback: Optional function called for each MySQL result
3008          * @param $fname String: Calling function name or false if name should be
3009          *      generated dynamically using $filename
3010          */
3011         function sourceFile( $filename, $lineCallback = false, $resultCallback = false, $fname = false ) {
3012                 wfSuppressWarnings();
3013                 $fp = fopen( $filename, 'r' );
3014                 wfRestoreWarnings();
3015
3016                 if ( false === $fp ) {
3017                         throw new MWException( "Could not open \"{$filename}\".\n" );
3018                 }
3019
3020                 if ( !$fname ) {
3021                         $fname = __METHOD__ . "( $filename )";
3022                 }
3023
3024                 try {
3025                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname );
3026                 }
3027                 catch ( MWException $e ) {
3028                         fclose( $fp );
3029                         throw $e;
3030                 }
3031
3032                 fclose( $fp );
3033
3034                 return $error;
3035         }
3036
3037         /**
3038          * Get the full path of a patch file. Originally based on archive()
3039          * from updaters.inc. Keep in mind this always returns a patch, as
3040          * it fails back to MySQL if no DB-specific patch can be found
3041          *
3042          * @param $patch String The name of the patch, like patch-something.sql
3043          * @return String Full path to patch file
3044          */
3045         public function patchPath( $patch ) {
3046                 global $IP;
3047
3048                 $dbType = $this->getType();
3049                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3050                         return "$IP/maintenance/$dbType/archives/$patch";
3051                 } else {
3052                         return "$IP/maintenance/archives/$patch";
3053                 }
3054         }
3055
3056         /**
3057          * Set variables to be used in sourceFile/sourceStream, in preference to the
3058          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3059          * all. If it's set to false, $GLOBALS will be used.
3060          *
3061          * @param $vars False, or array mapping variable name to value.
3062          */
3063         function setSchemaVars( $vars ) {
3064                 $this->mSchemaVars = $vars;
3065         }
3066
3067         /**
3068          * Read and execute commands from an open file handle.
3069          *
3070          * Returns true on success, error string or exception on failure (depending
3071          * on object's error ignore settings).
3072          *
3073          * @param $fp Resource: File handle
3074          * @param $lineCallback Callback: Optional function called before reading each line
3075          * @param $resultCallback Callback: Optional function called for each MySQL result
3076          * @param $fname String: Calling function name
3077          */
3078         function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3079                 $fname = 'DatabaseBase::sourceStream' )
3080         {
3081                 $cmd = "";
3082                 $done = false;
3083                 $dollarquote = false;
3084
3085                 while ( ! feof( $fp ) ) {
3086                         if ( $lineCallback ) {
3087                                 call_user_func( $lineCallback );
3088                         }
3089
3090                         $line = trim( fgets( $fp ) );
3091                         $sl = strlen( $line ) - 1;
3092
3093                         if ( $sl < 0 ) {
3094                                 continue;
3095                         }
3096
3097                         if ( '-' == $line[0] && '-' == $line[1] ) {
3098                                 continue;
3099                         }
3100
3101                         # # Allow dollar quoting for function declarations
3102                         if ( substr( $line, 0, 4 ) == '$mw$' ) {
3103                                 if ( $dollarquote ) {
3104                                         $dollarquote = false;
3105                                         $done = true;
3106                                 }
3107                                 else {
3108                                         $dollarquote = true;
3109                                 }
3110                         }
3111                         elseif ( !$dollarquote ) {
3112                                 if ( ';' == $line[$sl] && ( $sl < 2 || ';' != $line[$sl - 1] ) ) {
3113                                         $done = true;
3114                                         $line = substr( $line, 0, $sl );
3115                                 }
3116                         }
3117
3118                         if ( $cmd != '' ) {
3119                                 $cmd .= ' ';
3120                         }
3121
3122                         $cmd .= "$line\n";
3123
3124                         if ( $done ) {
3125                                 $cmd = str_replace( ';;', ";", $cmd );
3126                                 $cmd = $this->replaceVars( $cmd );
3127                                 $res = $this->query( $cmd, $fname );
3128
3129                                 if ( $resultCallback ) {
3130                                         call_user_func( $resultCallback, $res, $this );
3131                                 }
3132
3133                                 if ( false === $res ) {
3134                                         $err = $this->lastError();
3135                                         return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3136                                 }
3137
3138                                 $cmd = '';
3139                                 $done = false;
3140                         }
3141                 }
3142
3143                 return true;
3144         }
3145
3146         /**
3147          * Database independent variable replacement. Replaces a set of variables
3148          * in an SQL statement with their contents as given by $this->getSchemaVars().
3149          *
3150          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3151          *
3152          * - '{$var}' should be used for text and is passed through the database's
3153          *   addQuotes method.
3154          * - `{$var}` should be used for identifiers (eg: table and database names),
3155          *   it is passed through the database's addIdentifierQuotes method which
3156          *   can be overridden if the database uses something other than backticks.
3157          * - / *$var* / is just encoded, besides traditional table prefix and
3158          *   table options its use should be avoided.
3159          *
3160          * @param $ins String: SQL statement to replace variables in
3161          * @return String The new SQL statement with variables replaced
3162          */
3163         protected function replaceSchemaVars( $ins ) {
3164                 $vars = $this->getSchemaVars();
3165                 foreach ( $vars as $var => $value ) {
3166                         // replace '{$var}'
3167                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3168                         // replace `{$var}`
3169                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3170                         // replace /*$var*/
3171                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ) , $ins );
3172                 }
3173                 return $ins;
3174         }
3175
3176         /**
3177          * Replace variables in sourced SQL
3178          *
3179          * @param $ins string
3180          *
3181          * @return string
3182          */
3183         protected function replaceVars( $ins ) {
3184                 $ins = $this->replaceSchemaVars( $ins );
3185
3186                 // Table prefixes
3187                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3188                         array( $this, 'tableNameCallback' ), $ins );
3189
3190                 // Index names
3191                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3192                         array( $this, 'indexNameCallback' ), $ins );
3193
3194                 return $ins;
3195         }
3196
3197         /**
3198          * Get schema variables. If none have been set via setSchemaVars(), then
3199          * use some defaults from the current object.
3200          */
3201         protected function getSchemaVars() {
3202                 if ( $this->mSchemaVars ) {
3203                         return $this->mSchemaVars;
3204                 } else {
3205                         return $this->getDefaultSchemaVars();
3206                 }
3207         }
3208
3209         /**
3210          * Get schema variables to use if none have been set via setSchemaVars().
3211          *
3212          * Override this in derived classes to provide variables for tables.sql
3213          * and SQL patch files.
3214          *
3215          * @return array
3216          */
3217         protected function getDefaultSchemaVars() {
3218                 return array();
3219         }
3220
3221         /**
3222          * Table name callback
3223          *
3224          * @param $matches array
3225          *
3226          * @return string
3227          */
3228         protected function tableNameCallback( $matches ) {
3229                 return $this->tableName( $matches[1] );
3230         }
3231
3232         /**
3233          * Index name callback
3234          *
3235          * @param $matches array
3236          *
3237          * @return string
3238          */
3239         protected function indexNameCallback( $matches ) {
3240                 return $this->indexName( $matches[1] );
3241         }
3242
3243         /**
3244          * Build a concatenation list to feed into a SQL query
3245          * @param $stringList Array: list of raw SQL expressions; caller is responsible for any quoting
3246          * @return String
3247          */
3248         function buildConcat( $stringList ) {
3249                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
3250         }
3251
3252         /**
3253          * Acquire a named lock
3254          *
3255          * Abstracted from Filestore::lock() so child classes can implement for
3256          * their own needs.
3257          *
3258          * @param $lockName String: name of lock to aquire
3259          * @param $method String: name of method calling us
3260          * @param $timeout Integer: timeout
3261          * @return Boolean
3262          */
3263         public function lock( $lockName, $method, $timeout = 5 ) {
3264                 return true;
3265         }
3266
3267         /**
3268          * Release a lock.
3269          *
3270          * @param $lockName String: Name of lock to release
3271          * @param $method String: Name of method calling us
3272          *
3273          * @return Returns 1 if the lock was released, 0 if the lock was not established
3274          * by this thread (in which case the lock is not released), and NULL if the named
3275          * lock did not exist
3276          */
3277         public function unlock( $lockName, $method ) {
3278                 return true;
3279         }
3280
3281         /**
3282          * Lock specific tables
3283          *
3284          * @param $read Array of tables to lock for read access
3285          * @param $write Array of tables to lock for write access
3286          * @param $method String name of caller
3287          * @param $lowPriority bool Whether to indicate writes to be LOW PRIORITY
3288          *
3289          * @return bool
3290          */
3291         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3292                 return true;
3293         }
3294
3295         /**
3296          * Unlock specific tables
3297          *
3298          * @param $method String the caller
3299          *
3300          * @return bool
3301          */
3302         public function unlockTables( $method ) {
3303                 return true;
3304         }
3305
3306         /**
3307          * Delete a table
3308          * @param $tableName string
3309          * @param $fName string
3310          * @return bool|ResultWrapper
3311          */
3312         public function dropTable( $tableName, $fName = 'DatabaseBase::dropTable' ) {
3313                 if( !$this->tableExists( $tableName ) ) {
3314                         return false;
3315                 }
3316                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3317                 if( $this->cascadingDeletes() ) {
3318                         $sql .= " CASCADE";
3319                 }
3320                 return $this->query( $sql, $fName );
3321         }
3322
3323         /**
3324          * Get search engine class. All subclasses of this need to implement this
3325          * if they wish to use searching.
3326          *
3327          * @return String
3328          */
3329         public function getSearchEngine() {
3330                 return 'SearchEngineDummy';
3331         }
3332
3333         /**
3334          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3335          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3336          * because "i" sorts after all numbers.
3337          *
3338          * @return String
3339          */
3340         public function getInfinity() {
3341                 return 'infinity';
3342         }
3343
3344         /**
3345          * Encode an expiry time
3346          *
3347          * @param $expiry String: timestamp for expiry, or the 'infinity' string
3348          * @return String
3349          */
3350         public function encodeExpiry( $expiry ) {
3351                 if ( $expiry == '' || $expiry == $this->getInfinity() ) {
3352                         return $this->getInfinity();
3353                 } else {
3354                         return $this->timestamp( $expiry );
3355                 }
3356         }
3357
3358         /**
3359          * Allow or deny "big selects" for this session only. This is done by setting
3360          * the sql_big_selects session variable.
3361          *
3362          * This is a MySQL-specific feature.
3363          *
3364          * @param $value Mixed: true for allow, false for deny, or "default" to
3365          *   restore the initial value
3366          */
3367         public function setBigSelects( $value = true ) {
3368                 // no-op
3369         }
3370 }