includes/db/Database.php

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