includes/db/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * This file deals with database interface functions
   6  * and query specifics/optimisations.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Database
  25  */
  26
  27 /** Number of times to re-try an operation in case of deadlock */
  28 define( 'DEADLOCK_TRIES', 4 );
  29 /** Minimum time to wait before retry, in microseconds */
  30 define( 'DEADLOCK_DELAY_MIN', 500000 );
  31 /** Maximum time to wait before retry */
  32 define( 'DEADLOCK_DELAY_MAX', 1500000 );
  33
  34 /**
  35  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  36  * following must be implemented to support MediaWiki
  37  *
  38  * @file
  39  * @ingroup Database
  40  */
  41 interface DatabaseType {
  42         /**
  43          * Get the type of the DBMS, as it appears in $wgDBtype.
  44          *
  45          * @return string
  46          */
  47         function getType();
  48
  49         /**
  50          * Open a connection to the database. Usually aborts on failure
  51          *
  52          * @param $server String: database server host
  53          * @param $user String: database user name
  54          * @param $password String: database user password
  55          * @param $dbName String: database name
  56          * @return bool
  57          * @throws DBConnectionError
  58          */
  59         function open( $server, $user, $password, $dbName );
  60
  61         /**
  62          * Fetch the next row from the given result object, in object form.
  63          * Fields can be retrieved with $row->fieldname, with fields acting like
  64          * member variables.
  65          *
  66          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  67          * @return Row object
  68          * @throws DBUnexpectedError Thrown if the database returns an error
  69          */
  70         function fetchObject( $res );
  71
  72         /**
  73          * Fetch the next row from the given result object, in associative array
  74          * form.  Fields are retrieved with $row['fieldname'].
  75          *
  76          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  77          * @return Row object
  78          * @throws DBUnexpectedError Thrown if the database returns an error
  79          */
  80         function fetchRow( $res );
  81
  82         /**
  83          * Get the number of rows in a result object
  84          *
  85          * @param $res Mixed: A SQL result
  86          * @return int
  87          */
  88         function numRows( $res );
  89
  90         /**
  91          * Get the number of fields in a result object
  92          * @see http://www.php.net/mysql_num_fields
  93          *
  94          * @param $res Mixed: A SQL result
  95          * @return int
  96          */
  97         function numFields( $res );
  98
  99         /**
 100          * Get a field name in a result object
 101          * @see http://www.php.net/mysql_field_name
 102          *
 103          * @param $res Mixed: A SQL result
 104          * @param $n Integer
 105          * @return string
 106          */
 107         function fieldName( $res, $n );
 108
 109         /**
 110          * Get the inserted value of an auto-increment row
 111          *
 112          * The value inserted should be fetched from nextSequenceValue()
 113          *
 114          * Example:
 115          * $id = $dbw->nextSequenceValue('page_page_id_seq');
 116          * $dbw->insert('page',array('page_id' => $id));
 117          * $id = $dbw->insertId();
 118          *
 119          * @return int
 120          */
 121         function insertId();
 122
 123         /**
 124          * Change the position of the cursor in a result object
 125          * @see http://www.php.net/mysql_data_seek
 126          *
 127          * @param $res Mixed: A SQL result
 128          * @param $row Mixed: Either MySQL row or ResultWrapper
 129          */
 130         function dataSeek( $res, $row );
 131
 132         /**
 133          * Get the last error number
 134          * @see http://www.php.net/mysql_errno
 135          *
 136          * @return int
 137          */
 138         function lastErrno();
 139
 140         /**
 141          * Get a description of the last error
 142          * @see http://www.php.net/mysql_error
 143          *
 144          * @return string
 145          */
 146         function lastError();
 147
 148         /**
 149          * mysql_fetch_field() wrapper
 150          * Returns false if the field doesn't exist
 151          *
 152          * @param $table string: table name
 153          * @param $field string: field name
 154          *
 155          * @return Field
 156          */
 157         function fieldInfo( $table, $field );
 158
 159         /**
 160          * Get information about an index into an object
 161          * @param $table string: Table name
 162          * @param $index string: Index name
 163          * @param $fname string: Calling function name
 164          * @return Mixed: Database-specific index description class or false if the index does not exist
 165          */
 166         function indexInfo( $table, $index, $fname = 'Database::indexInfo' );
 167
 168         /**
 169          * Get the number of rows affected by the last write query
 170          * @see http://www.php.net/mysql_affected_rows
 171          *
 172          * @return int
 173          */
 174         function affectedRows();
 175
 176         /**
 177          * Wrapper for addslashes()
 178          *
 179          * @param $s string: to be slashed.
 180          * @return string: slashed string.
 181          */
 182         function strencode( $s );
 183
 184         /**
 185          * Returns a wikitext link to the DB's website, e.g.,
 186          *     return "[http://www.mysql.com/ MySQL]";
 187          * Should at least contain plain text, if for some reason
 188          * your database has no website.
 189          *
 190          * @return string: wikitext of a link to the server software's web site
 191          */
 192         static function getSoftwareLink();
 193
 194         /**
 195          * A string describing the current software version, like from
 196          * mysql_get_server_info().
 197          *
 198          * @return string: Version information from the database server.
 199          */
 200         function getServerVersion();
 201
 202         /**
 203          * A string describing the current software version, and possibly
 204          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 205          * Use getServerVersion() to get machine-friendly information.
 206          *
 207          * @return string: Version information from the database server
 208          */
 209         function getServerInfo();
 210 }
 211
 212 /**
 213  * Database abstraction object
 214  * @ingroup Database
 215  */
 216 abstract class DatabaseBase implements DatabaseType {
 217
 218 # ------------------------------------------------------------------------------
 219 # Variables
 220 # ------------------------------------------------------------------------------
 221
 222         protected $mLastQuery = '';
 223         protected $mDoneWrites = false;
 224         protected $mPHPError = false;
 225
 226         protected $mServer, $mUser, $mPassword, $mDBname;
 227
 228         /**
 229          * @var DatabaseBase
 230          */
 231         protected $mConn = null;
 232         protected $mOpened = false;
 233
 234         protected $mTablePrefix;
 235         protected $mFlags;
 236         protected $mTrxLevel = 0;
 237         protected $mErrorCount = 0;
 238         protected $mLBInfo = array();
 239         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 240         protected $mDefaultBigSelects = null;
 241         protected $mSchemaVars = false;
 242
 243         protected $preparedArgs;
 244
 245         protected $htmlErrors;
 246
 247         protected $delimiter = ';';
 248
 249 # ------------------------------------------------------------------------------
 250 # Accessors
 251 # ------------------------------------------------------------------------------
 252         # These optionally set a variable and return the previous state
 253
 254         /**
 255          * A string describing the current software version, and possibly
 256          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 257          * Use getServerVersion() to get machine-friendly information.
 258          *
 259          * @return string: Version information from the database server
 260          */
 261         public function getServerInfo() {
 262                 return $this->getServerVersion();
 263         }
 264
 265         /**
 266          * Boolean, controls output of large amounts of debug information.
 267          * @param $debug bool|null
 268          *   - true to enable debugging
 269          *   - false to disable debugging
 270          *   - omitted or null to do nothing
 271          *
 272          * @return bool|null previous value of the flag
 273          */
 274         public function debug( $debug = null ) {
 275                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 276         }
 277
 278         /**
 279          * Turns buffering of SQL result sets on (true) or off (false). Default is
 280          * "on".
 281          *
 282          * Unbuffered queries are very troublesome in MySQL:
 283          *
 284          *   - If another query is executed while the first query is being read
 285          *     out, the first query is killed. This means you can't call normal
 286          *     MediaWiki functions while you are reading an unbuffered query result
 287          *     from a normal wfGetDB() connection.
 288          *
 289          *   - Unbuffered queries cause the MySQL server to use large amounts of
 290          *     memory and to hold broad locks which block other queries.
 291          *
 292          * If you want to limit client-side memory, it's almost always better to
 293          * split up queries into batches using a LIMIT clause than to switch off
 294          * buffering.
 295          *
 296          * @param $buffer null|bool
 297          *
 298          * @return null|bool The previous value of the flag
 299          */
 300         public function bufferResults( $buffer = null ) {
 301                 if ( is_null( $buffer ) ) {
 302                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 303                 } else {
 304                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 305                 }
 306         }
 307
 308         /**
 309          * Turns on (false) or off (true) the automatic generation and sending
 310          * of a "we're sorry, but there has been a database error" page on
 311          * database errors. Default is on (false). When turned off, the
 312          * code should use lastErrno() and lastError() to handle the
 313          * situation as appropriate.
 314          *
 315          * @param $ignoreErrors bool|null
 316          *
 317          * @return bool The previous value of the flag.
 318          */
 319         public function ignoreErrors( $ignoreErrors = null ) {
 320                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 321         }
 322
 323         /**
 324          * Gets or sets the current transaction level.
 325          *
 326          * Historically, transactions were allowed to be "nested". This is no
 327          * longer supported, so this function really only returns a boolean.
 328          *
 329          * @param $level int An integer (0 or 1), or omitted to leave it unchanged.
 330          * @return int The previous value
 331          */
 332         public function trxLevel( $level = null ) {
 333                 return wfSetVar( $this->mTrxLevel, $level );
 334         }
 335
 336         /**
 337          * Get/set the number of errors logged. Only useful when errors are ignored
 338          * @param $count int The count to set, or omitted to leave it unchanged.
 339          * @return int The error count
 340          */
 341         public function errorCount( $count = null ) {
 342                 return wfSetVar( $this->mErrorCount, $count );
 343         }
 344
 345         /**
 346          * Get/set the table prefix.
 347          * @param $prefix string The table prefix to set, or omitted to leave it unchanged.
 348          * @return string The previous table prefix.
 349          */
 350         public function tablePrefix( $prefix = null ) {
 351                 return wfSetVar( $this->mTablePrefix, $prefix );
 352         }
 353
 354         /**
 355          * Get properties passed down from the server info array of the load
 356          * balancer.
 357          *
 358          * @param $name string The entry of the info array to get, or null to get the
 359          *   whole array
 360          *
 361          * @return LoadBalancer|null
 362          */
 363         public function getLBInfo( $name = null ) {
 364                 if ( is_null( $name ) ) {
 365                         return $this->mLBInfo;
 366                 } else {
 367                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 368                                 return $this->mLBInfo[$name];
 369                         } else {
 370                                 return null;
 371                         }
 372                 }
 373         }
 374
 375         /**
 376          * Set the LB info array, or a member of it. If called with one parameter,
 377          * the LB info array is set to that parameter. If it is called with two
 378          * parameters, the member with the given name is set to the given value.
 379          *
 380          * @param $name
 381          * @param $value
 382          */
 383         public function setLBInfo( $name, $value = null ) {
 384                 if ( is_null( $value ) ) {
 385                         $this->mLBInfo = $name;
 386                 } else {
 387                         $this->mLBInfo[$name] = $value;
 388                 }
 389         }
 390
 391         /**
 392          * Set lag time in seconds for a fake slave
 393          *
 394          * @param $lag int
 395          */
 396         public function setFakeSlaveLag( $lag ) {
 397                 $this->mFakeSlaveLag = $lag;
 398         }
 399
 400         /**
 401          * Make this connection a fake master
 402          *
 403          * @param $enabled bool
 404          */
 405         public function setFakeMaster( $enabled = true ) {
 406                 $this->mFakeMaster = $enabled;
 407         }
 408
 409         /**
 410          * Returns true if this database supports (and uses) cascading deletes
 411          *
 412          * @return bool
 413          */
 414         public function cascadingDeletes() {
 415                 return false;
 416         }
 417
 418         /**
 419          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 420          *
 421          * @return bool
 422          */
 423         public function cleanupTriggers() {
 424                 return false;
 425         }
 426
 427         /**
 428          * Returns true if this database is strict about what can be put into an IP field.
 429          * Specifically, it uses a NULL value instead of an empty string.
 430          *
 431          * @return bool
 432          */
 433         public function strictIPs() {
 434                 return false;
 435         }
 436
 437         /**
 438          * Returns true if this database uses timestamps rather than integers
 439          *
 440          * @return bool
 441         */
 442         public function realTimestamps() {
 443                 return false;
 444         }
 445
 446         /**
 447          * Returns true if this database does an implicit sort when doing GROUP BY
 448          *
 449          * @return bool
 450          */
 451         public function implicitGroupby() {
 452                 return true;
 453         }
 454
 455         /**
 456          * Returns true if this database does an implicit order by when the column has an index
 457          * For example: SELECT page_title FROM page LIMIT 1
 458          *
 459          * @return bool
 460          */
 461         public function implicitOrderby() {
 462                 return true;
 463         }
 464
 465         /**
 466          * Returns true if this database can do a native search on IP columns
 467          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 468          *
 469          * @return bool
 470          */
 471         public function searchableIPs() {
 472                 return false;
 473         }
 474
 475         /**
 476          * Returns true if this database can use functional indexes
 477          *
 478          * @return bool
 479          */
 480         public function functionalIndexes() {
 481                 return false;
 482         }
 483
 484         /**
 485          * Return the last query that went through DatabaseBase::query()
 486          * @return String
 487          */
 488         public function lastQuery() {
 489                 return $this->mLastQuery;
 490         }
 491
 492         /**
 493          * Returns true if the connection may have been used for write queries.
 494          * Should return true if unsure.
 495          *
 496          * @return bool
 497          */
 498         public function doneWrites() {
 499                 return $this->mDoneWrites;
 500         }
 501
 502         /**
 503          * Is a connection to the database open?
 504          * @return Boolean
 505          */
 506         public function isOpen() {
 507                 return $this->mOpened;
 508         }
 509
 510         /**
 511          * Set a flag for this connection
 512          *
 513          * @param $flag Integer: DBO_* constants from Defines.php:
 514          *   - DBO_DEBUG: output some debug info (same as debug())
 515          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 516          *   - DBO_IGNORE: ignore errors (same as ignoreErrors())
 517          *   - DBO_TRX: automatically start transactions
 518          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 519          *       and removes it in command line mode
 520          *   - DBO_PERSISTENT: use persistant database connection
 521          */
 522         public function setFlag( $flag ) {
 523                 global $wgDebugDBTransactions;
 524                 $this->mFlags |= $flag;
 525                 if ( ( $flag & DBO_TRX) & $wgDebugDBTransactions ) {
 526                         wfDebug("Implicit transactions are now  disabled.\n");
 527                 }
 528         }
 529
 530         /**
 531          * Clear a flag for this connection
 532          *
 533          * @param $flag: same as setFlag()'s $flag param
 534          */
 535         public function clearFlag( $flag ) {
 536                 global $wgDebugDBTransactions;
 537                 $this->mFlags &= ~$flag;
 538                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 539                         wfDebug("Implicit transactions are now disabled.\n");
 540                 }
 541         }
 542
 543         /**
 544          * Returns a boolean whether the flag $flag is set for this connection
 545          *
 546          * @param $flag: same as setFlag()'s $flag param
 547          * @return Boolean
 548          */
 549         public function getFlag( $flag ) {
 550                 return !!( $this->mFlags & $flag );
 551         }
 552
 553         /**
 554          * General read-only accessor
 555          *
 556          * @param $name string
 557          *
 558          * @return string
 559          */
 560         public function getProperty( $name ) {
 561                 return $this->$name;
 562         }
 563
 564         /**
 565          * @return string
 566          */
 567         public function getWikiID() {
 568                 if ( $this->mTablePrefix ) {
 569                         return "{$this->mDBname}-{$this->mTablePrefix}";
 570                 } else {
 571                         return $this->mDBname;
 572                 }
 573         }
 574
 575         /**
 576          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 577          *
 578          * @return string
 579          */
 580         public function getSchemaPath() {
 581                 global $IP;
 582                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 583                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 584                 } else {
 585                         return "$IP/maintenance/tables.sql";
 586                 }
 587         }
 588
 589 # ------------------------------------------------------------------------------
 590 # Other functions
 591 # ------------------------------------------------------------------------------
 592
 593         /**
 594          * Constructor.
 595          * @param $server String: database server host
 596          * @param $user String: database user name
 597          * @param $password String: database user password
 598          * @param $dbName String: database name
 599          * @param $flags
 600          * @param $tablePrefix String: database table prefixes. By default use the prefix gave in LocalSettings.php
 601          */
 602         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 603                 $flags = 0, $tablePrefix = 'get from global'
 604         ) {
 605                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 606
 607                 $this->mFlags = $flags;
 608
 609                 if ( $this->mFlags & DBO_DEFAULT ) {
 610                         if ( $wgCommandLineMode ) {
 611                                 $this->mFlags &= ~DBO_TRX;
 612                                 if ( $wgDebugDBTransactions ) {
 613                                         wfDebug("Implicit transaction open disabled.\n");
 614                                 }
 615                         } else {
 616                                 $this->mFlags |= DBO_TRX;
 617                                 if ( $wgDebugDBTransactions ) {
 618                                         wfDebug("Implicit transaction open enabled.\n");
 619                                 }
 620                         }
 621                 }
 622
 623                 /** Get the default table prefix*/
 624                 if ( $tablePrefix == 'get from global' ) {
 625                         $this->mTablePrefix = $wgDBprefix;
 626                 } else {
 627                         $this->mTablePrefix = $tablePrefix;
 628                 }
 629
 630                 if ( $user ) {
 631                         $this->open( $server, $user, $password, $dbName );
 632                 }
 633         }
 634
 635         /**
 636          * Called by serialize. Throw an exception when DB connection is serialized.
 637          * This causes problems on some database engines because the connection is
 638          * not restored on unserialize.
 639          */
 640         public function __sleep() {
 641                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 642         }
 643
 644         /**
 645          * Given a DB type, construct the name of the appropriate child class of
 646          * DatabaseBase. This is designed to replace all of the manual stuff like:
 647          *      $class = 'Database' . ucfirst( strtolower( $type ) );
 648          * as well as validate against the canonical list of DB types we have
 649          *
 650          * This factory function is mostly useful for when you need to connect to a
 651          * database other than the MediaWiki default (such as for external auth,
 652          * an extension, et cetera). Do not use this to connect to the MediaWiki
 653          * database. Example uses in core:
 654          * @see LoadBalancer::reallyOpenConnection()
 655          * @see ExternalUser_MediaWiki::initFromCond()
 656          * @see ForeignDBRepo::getMasterDB()
 657          * @see WebInstaller_DBConnect::execute()
 658          *
 659          * @since 1.18
 660          *
 661          * @param $dbType String A possible DB type
 662          * @param $p Array An array of options to pass to the constructor.
 663          *    Valid options are: host, user, password, dbname, flags, tablePrefix
 664          * @return DatabaseBase subclass or null
 665          */
 666         public final static function factory( $dbType, $p = array() ) {
 667                 $canonicalDBTypes = array(
 668                         'mysql', 'postgres', 'sqlite', 'oracle', 'mssql', 'ibm_db2'
 669                 );
 670                 $dbType = strtolower( $dbType );
 671                 $class = 'Database' . ucfirst( $dbType );
 672
 673                 if( in_array( $dbType, $canonicalDBTypes ) || ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) ) {
 674                         return new $class(
 675                                 isset( $p['host'] ) ? $p['host'] : false,
 676                                 isset( $p['user'] ) ? $p['user'] : false,
 677                                 isset( $p['password'] ) ? $p['password'] : false,
 678                                 isset( $p['dbname'] ) ? $p['dbname'] : false,
 679                                 isset( $p['flags'] ) ? $p['flags'] : 0,
 680                                 isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global'
 681                         );
 682                 } else {
 683                         return null;
 684                 }
 685         }
 686
 687         protected function installErrorHandler() {
 688                 $this->mPHPError = false;
 689                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 690                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 691         }
 692
 693         /**
 694          * @return bool|string
 695          */
 696         protected function restoreErrorHandler() {
 697                 restore_error_handler();
 698                 if ( $this->htmlErrors !== false ) {
 699                         ini_set( 'html_errors', $this->htmlErrors );
 700                 }
 701                 if ( $this->mPHPError ) {
 702                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 703                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 704                         return $error;
 705                 } else {
 706                         return false;
 707                 }
 708         }
 709
 710         /**
 711          * @param $errno
 712          * @param $errstr
 713          */
 714         protected function connectionErrorHandler( $errno,  $errstr ) {
 715                 $this->mPHPError = $errstr;
 716         }
 717
 718         /**
 719          * Closes a database connection.
 720          * if it is open : commits any open transactions
 721          *
 722          * @return Bool operation success. true if already closed.
 723          */
 724         public function close() {
 725                 $this->mOpened = false;
 726                 if ( $this->mConn ) {
 727                         if ( $this->trxLevel() ) {
 728                                 $this->commit( __METHOD__ );
 729                         }
 730                         $ret = $this->closeConnection();
 731                         $this->mConn = false;
 732                         return $ret;
 733                 } else {
 734                         return true;
 735                 }
 736         }
 737
 738         /**
 739          * Closes underlying database connection
 740          * @since 1.20
 741          * @return bool: Whether connection was closed successfully
 742          */
 743         protected abstract function closeConnection();
 744
 745         /**
 746          * @param $error String: fallback error message, used if none is given by DB
 747          */
 748         function reportConnectionError( $error = 'Unknown error' ) {
 749                 $myError = $this->lastError();
 750                 if ( $myError ) {
 751                         $error = $myError;
 752                 }
 753
 754                 # New method
 755                 throw new DBConnectionError( $this, $error );
 756         }
 757
 758         /**
 759          * The DBMS-dependent part of query()
 760          *
 761          * @param  $sql String: SQL query.
 762          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 763          */
 764         protected abstract function doQuery( $sql );
 765
 766         /**
 767          * Determine whether a query writes to the DB.
 768          * Should return true if unsure.
 769          *
 770          * @param $sql string
 771          *
 772          * @return bool
 773          */
 774         public function isWriteQuery( $sql ) {
 775                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 776         }
 777
 778         /**
 779          * Run an SQL query and return the result. Normally throws a DBQueryError
 780          * on failure. If errors are ignored, returns false instead.
 781          *
 782          * In new code, the query wrappers select(), insert(), update(), delete(),
 783          * etc. should be used where possible, since they give much better DBMS
 784          * independence and automatically quote or validate user input in a variety
 785          * of contexts. This function is generally only useful for queries which are
 786          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 787          * as CREATE TABLE.
 788          *
 789          * However, the query wrappers themselves should call this function.
 790          *
 791          * @param  $sql        String: SQL query
 792          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 793          *     comment (you can use __METHOD__ or add some extra info)
 794          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 795          *     maybe best to catch the exception instead?
 796          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 797          *     for a successful read query, or false on failure if $tempIgnore set
 798          * @throws DBQueryError Thrown when the database returns an error of any kind
 799          */
 800         public function query( $sql, $fname = '', $tempIgnore = false ) {
 801                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 802                 if ( !Profiler::instance()->isStub() ) {
 803                         # generalizeSQL will probably cut down the query to reasonable
 804                         # logging size most of the time. The substr is really just a sanity check.
 805
 806                         if ( $isMaster ) {
 807                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 808                                 $totalProf = 'DatabaseBase::query-master';
 809                         } else {
 810                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 811                                 $totalProf = 'DatabaseBase::query';
 812                         }
 813
 814                         wfProfileIn( $totalProf );
 815                         wfProfileIn( $queryProf );
 816                 }
 817
 818                 $this->mLastQuery = $sql;
 819                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 820                         # Set a flag indicating that writes have been done
 821                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 822                         $this->mDoneWrites = true;
 823                 }
 824
 825                 # Add a comment for easy SHOW PROCESSLIST interpretation
 826                 global $wgUser;
 827                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 828                         $userName = $wgUser->getName();
 829                         if ( mb_strlen( $userName ) > 15 ) {
 830                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 831                         }
 832                         $userName = str_replace( '/', '', $userName );
 833                 } else {
 834                         $userName = '';
 835                 }
 836                 $commentedSql = preg_replace( '/\s/', " /* $fname $userName */ ", $sql, 1 );
 837
 838                 # If DBO_TRX is set, start a transaction
 839                 if ( ( $this->mFlags & DBO_TRX ) && !$this->trxLevel() &&
 840                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' ) {
 841                         # avoid establishing transactions for SHOW and SET statements too -
 842                         # that would delay transaction initializations to once connection
 843                         # is really used by application
 844                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 845                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 846                                 global $wgDebugDBTransactions;
 847                                 if ( $wgDebugDBTransactions ) {
 848                                         wfDebug("Implicit transaction start.\n");
 849                                 }
 850                                 $this->begin( __METHOD__ . " ($fname)" );
 851                         }
 852                 }
 853
 854                 if ( $this->debug() ) {
 855                         static $cnt = 0;
 856
 857                         $cnt++;
 858                         $sqlx = substr( $commentedSql, 0, 500 );
 859                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 860
 861                         $master = $isMaster ? 'master' : 'slave';
 862                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 863                 }
 864
 865                 if ( istainted( $sql ) & TC_MYSQL ) {
 866                         throw new MWException( 'Tainted query found' );
 867                 }
 868
 869                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 870
 871                 # Do the query and handle errors
 872                 $ret = $this->doQuery( $commentedSql );
 873
 874                 MWDebug::queryTime( $queryId );
 875
 876                 # Try reconnecting if the connection was lost
 877                 if ( false === $ret && $this->wasErrorReissuable() ) {
 878                         # Transaction is gone, like it or not
 879                         $this->mTrxLevel = 0;
 880                         wfDebug( "Connection lost, reconnecting...\n" );
 881
 882                         if ( $this->ping() ) {
 883                                 wfDebug( "Reconnected\n" );
 884                                 $sqlx = substr( $commentedSql, 0, 500 );
 885                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
 886                                 global $wgRequestTime;
 887                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
 888                                 if ( $elapsed < 300 ) {
 889                                         # Not a database error to lose a transaction after a minute or two
 890                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
 891                                 }
 892                                 $ret = $this->doQuery( $commentedSql );
 893                         } else {
 894                                 wfDebug( "Failed\n" );
 895                         }
 896                 }
 897
 898                 if ( false === $ret ) {
 899                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 900                 }
 901
 902                 if ( !Profiler::instance()->isStub() ) {
 903                         wfProfileOut( $queryProf );
 904                         wfProfileOut( $totalProf );
 905                 }
 906
 907                 return $this->resultObject( $ret );
 908         }
 909
 910         /**
 911          * Report a query error. Log the error, and if neither the object ignore
 912          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
 913          *
 914          * @param $error String
 915          * @param $errno Integer
 916          * @param $sql String
 917          * @param $fname String
 918          * @param $tempIgnore Boolean
 919          */
 920         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
 921                 # Ignore errors during error handling to avoid infinite recursion
 922                 $ignore = $this->ignoreErrors( true );
 923                 ++$this->mErrorCount;
 924
 925                 if ( $ignore || $tempIgnore ) {
 926                         wfDebug( "SQL ERROR (ignored): $error\n" );
 927                         $this->ignoreErrors( $ignore );
 928                 } else {
 929                         $sql1line = str_replace( "\n", "\\n", $sql );
 930                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
 931                         wfDebug( "SQL ERROR: " . $error . "\n" );
 932                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
 933                 }
 934         }
 935
 936         /**
 937          * Intended to be compatible with the PEAR::DB wrapper functions.
 938          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
 939          *
 940          * ? = scalar value, quoted as necessary
 941          * ! = raw SQL bit (a function for instance)
 942          * & = filename; reads the file and inserts as a blob
 943          *     (we don't use this though...)
 944          *
 945          * @param $sql string
 946          * @param $func string
 947          *
 948          * @return array
 949          */
 950         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
 951                 /* MySQL doesn't support prepared statements (yet), so just
 952                    pack up the query for reference. We'll manually replace
 953                    the bits later. */
 954                 return array( 'query' => $sql, 'func' => $func );
 955         }
 956
 957         /**
 958          * Free a prepared query, generated by prepare().
 959          * @param $prepared
 960          */
 961         protected function freePrepared( $prepared ) {
 962                 /* No-op by default */
 963         }
 964
 965         /**
 966          * Execute a prepared query with the various arguments
 967          * @param $prepared String: the prepared sql
 968          * @param $args Mixed: Either an array here, or put scalars as varargs
 969          *
 970          * @return ResultWrapper
 971          */
 972         public function execute( $prepared, $args = null ) {
 973                 if ( !is_array( $args ) ) {
 974                         # Pull the var args
 975                         $args = func_get_args();
 976                         array_shift( $args );
 977                 }
 978
 979                 $sql = $this->fillPrepared( $prepared['query'], $args );
 980
 981                 return $this->query( $sql, $prepared['func'] );
 982         }
 983
 984         /**
 985          * For faking prepared SQL statements on DBs that don't support it directly.
 986          *
 987          * @param $preparedQuery String: a 'preparable' SQL statement
 988          * @param $args Array of arguments to fill it with
 989          * @return string executable SQL
 990          */
 991         public function fillPrepared( $preparedQuery, $args ) {
 992                 reset( $args );
 993                 $this->preparedArgs =& $args;
 994
 995                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
 996                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
 997         }
 998
 999         /**
1000          * preg_callback func for fillPrepared()
1001          * The arguments should be in $this->preparedArgs and must not be touched
1002          * while we're doing this.
1003          *
1004          * @param $matches Array
1005          * @return String
1006          */
1007         protected function fillPreparedArg( $matches ) {
1008                 switch( $matches[1] ) {
1009                         case '\\?': return '?';
1010                         case '\\!': return '!';
1011                         case '\\&': return '&';
1012                 }
1013
1014                 list( /* $n */ , $arg ) = each( $this->preparedArgs );
1015
1016                 switch( $matches[1] ) {
1017                         case '?': return $this->addQuotes( $arg );
1018                         case '!': return $arg;
1019                         case '&':
1020                                 # return $this->addQuotes( file_get_contents( $arg ) );
1021                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1022                         default:
1023                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1024                 }
1025         }
1026
1027         /**
1028          * Free a result object returned by query() or select(). It's usually not
1029          * necessary to call this, just use unset() or let the variable holding
1030          * the result object go out of scope.
1031          *
1032          * @param $res Mixed: A SQL result
1033          */
1034         public function freeResult( $res ) {}
1035
1036         /**
1037          * A SELECT wrapper which returns a single field from a single result row.
1038          *
1039          * Usually throws a DBQueryError on failure. If errors are explicitly
1040          * ignored, returns false on failure.
1041          *
1042          * If no result rows are returned from the query, false is returned.
1043          *
1044          * @param $table string|array Table name. See DatabaseBase::select() for details.
1045          * @param $var string The field name to select. This must be a valid SQL
1046          *   fragment: do not use unvalidated user input.
1047          * @param $cond string|array The condition array. See DatabaseBase::select() for details.
1048          * @param $fname string The function name of the caller.
1049          * @param $options string|array The query options. See DatabaseBase::select() for details.
1050          *
1051          * @return bool|mixed The value from the field, or false on failure.
1052          */
1053         public function selectField( $table, $var, $cond = '', $fname = 'DatabaseBase::selectField',
1054                 $options = array() )
1055         {
1056                 if ( !is_array( $options ) ) {
1057                         $options = array( $options );
1058                 }
1059
1060                 $options['LIMIT'] = 1;
1061
1062                 $res = $this->select( $table, $var, $cond, $fname, $options );
1063
1064                 if ( $res === false || !$this->numRows( $res ) ) {
1065                         return false;
1066                 }
1067
1068                 $row = $this->fetchRow( $res );
1069
1070                 if ( $row !== false ) {
1071                         return reset( $row );
1072                 } else {
1073                         return false;
1074                 }
1075         }
1076
1077         /**
1078          * Returns an optional USE INDEX clause to go after the table, and a
1079          * string to go at the end of the query.
1080          *
1081          * @param $options Array: associative array of options to be turned into
1082          *              an SQL query, valid keys are listed in the function.
1083          * @return Array
1084          * @see DatabaseBase::select()
1085          */
1086         public function makeSelectOptions( $options ) {
1087                 $preLimitTail = $postLimitTail = '';
1088                 $startOpts = '';
1089
1090                 $noKeyOptions = array();
1091
1092                 foreach ( $options as $key => $option ) {
1093                         if ( is_numeric( $key ) ) {
1094                                 $noKeyOptions[$option] = true;
1095                         }
1096                 }
1097
1098                 if ( isset( $options['GROUP BY'] ) ) {
1099                         $gb = is_array( $options['GROUP BY'] )
1100                                 ? implode( ',', $options['GROUP BY'] )
1101                                 : $options['GROUP BY'];
1102                         $preLimitTail .= " GROUP BY {$gb}";
1103                 }
1104
1105                 if ( isset( $options['HAVING'] ) ) {
1106                         $preLimitTail .= " HAVING {$options['HAVING']}";
1107                 }
1108
1109                 if ( isset( $options['ORDER BY'] ) ) {
1110                         $ob = is_array( $options['ORDER BY'] )
1111                                 ? implode( ',', $options['ORDER BY'] )
1112                                 : $options['ORDER BY'];
1113                         $preLimitTail .= " ORDER BY {$ob}";
1114                 }
1115
1116                 // if (isset($options['LIMIT'])) {
1117                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1118                 //              isset($options['OFFSET']) ? $options['OFFSET']
1119                 //              : false);
1120                 // }
1121
1122                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1123                         $postLimitTail .= ' FOR UPDATE';
1124                 }
1125
1126                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1127                         $postLimitTail .= ' LOCK IN SHARE MODE';
1128                 }
1129
1130                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1131                         $startOpts .= 'DISTINCT';
1132                 }
1133
1134                 # Various MySQL extensions
1135                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1136                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1137                 }
1138
1139                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1140                         $startOpts .= ' HIGH_PRIORITY';
1141                 }
1142
1143                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1144                         $startOpts .= ' SQL_BIG_RESULT';
1145                 }
1146
1147                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1148                         $startOpts .= ' SQL_BUFFER_RESULT';
1149                 }
1150
1151                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1152                         $startOpts .= ' SQL_SMALL_RESULT';
1153                 }
1154
1155                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1156                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1157                 }
1158
1159                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1160                         $startOpts .= ' SQL_CACHE';
1161                 }
1162
1163                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1164                         $startOpts .= ' SQL_NO_CACHE';
1165                 }
1166
1167                 if ( isset( $options['USE INDEX'] ) && ! is_array( $options['USE INDEX'] ) ) {
1168                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1169                 } else {
1170                         $useIndex = '';
1171                 }
1172
1173                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1174         }
1175
1176         /**
1177          * Execute a SELECT query constructed using the various parameters provided.
1178          * See below for full details of the parameters.
1179          *
1180          * @param $table String|Array Table name
1181          * @param $vars String|Array Field names
1182          * @param $conds String|Array Conditions
1183          * @param $fname String Caller function name
1184          * @param $options Array Query options
1185          * @param $join_conds Array Join conditions
1186          *
1187          * @param $table string|array
1188          *
1189          * May be either an array of table names, or a single string holding a table
1190          * name. If an array is given, table aliases can be specified, for example:
1191          *
1192          *    array( 'a' => 'user' )
1193          *
1194          * This includes the user table in the query, with the alias "a" available
1195          * for use in field names (e.g. a.user_name).
1196          *
1197          * All of the table names given here are automatically run through
1198          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1199          * added, and various other table name mappings to be performed.
1200          *
1201          *
1202          * @param $vars string|array
1203          *
1204          * May be either a field name or an array of field names. The field names
1205          * here are complete fragments of SQL, for direct inclusion into the SELECT
1206          * query. Expressions and aliases may be specified as in SQL, for example:
1207          *
1208          *   array( 'MAX(rev_id) AS maxrev' )
1209          *
1210          * If an expression is given, care must be taken to ensure that it is
1211          * DBMS-independent.
1212          *
1213          *
1214          * @param $conds string|array
1215          *
1216          * May be either a string containing a single condition, or an array of
1217          * conditions. If an array is given, the conditions constructed from each
1218          * element are combined with AND.
1219          *
1220          * Array elements may take one of two forms:
1221          *
1222          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1223          *   - Elements with a string key are interpreted as equality conditions,
1224          *     where the key is the field name.
1225          *     - If the value of such an array element is a scalar (such as a
1226          *       string), it will be treated as data and thus quoted appropriately.
1227          *       If it is null, an IS NULL clause will be added.
1228          *     - If the value is an array, an IN(...) clause will be constructed,
1229          *       such that the field name may match any of the elements in the
1230          *       array. The elements of the array will be quoted.
1231          *
1232          * Note that expressions are often DBMS-dependent in their syntax.
1233          * DBMS-independent wrappers are provided for constructing several types of
1234          * expression commonly used in condition queries. See:
1235          *    - DatabaseBase::buildLike()
1236          *    - DatabaseBase::conditional()
1237          *
1238          *
1239          * @param $options string|array
1240          *
1241          * Optional: Array of query options. Boolean options are specified by
1242          * including them in the array as a string value with a numeric key, for
1243          * example:
1244          *
1245          *    array( 'FOR UPDATE' )
1246          *
1247          * The supported options are:
1248          *
1249          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1250          *     with LIMIT can theoretically be used for paging through a result set,
1251          *     but this is discouraged in MediaWiki for performance reasons.
1252          *
1253          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1254          *     and then the first rows are taken until the limit is reached. LIMIT
1255          *     is applied to a result set after OFFSET.
1256          *
1257          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1258          *     changed until the next COMMIT.
1259          *
1260          *   - DISTINCT: Boolean: return only unique result rows.
1261          *
1262          *   - GROUP BY: May be either an SQL fragment string naming a field or
1263          *     expression to group by, or an array of such SQL fragments.
1264          *
1265          *   - HAVING: A string containing a HAVING clause.
1266          *
1267          *   - ORDER BY: May be either an SQL fragment giving a field name or
1268          *     expression to order by, or an array of such SQL fragments.
1269          *
1270          *   - USE INDEX: This may be either a string giving the index name to use
1271          *     for the query, or an array. If it is an associative array, each key
1272          *     gives the table name (or alias), each value gives the index name to
1273          *     use for that table. All strings are SQL fragments and so should be
1274          *     validated by the caller.
1275          *
1276          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1277          *     instead of SELECT.
1278          *
1279          * And also the following boolean MySQL extensions, see the MySQL manual
1280          * for documentation:
1281          *
1282          *    - LOCK IN SHARE MODE
1283          *    - STRAIGHT_JOIN
1284          *    - HIGH_PRIORITY
1285          *    - SQL_BIG_RESULT
1286          *    - SQL_BUFFER_RESULT
1287          *    - SQL_SMALL_RESULT
1288          *    - SQL_CALC_FOUND_ROWS
1289          *    - SQL_CACHE
1290          *    - SQL_NO_CACHE
1291          *
1292          *
1293          * @param $join_conds string|array
1294          *
1295          * Optional associative array of table-specific join conditions. In the
1296          * most common case, this is unnecessary, since the join condition can be
1297          * in $conds. However, it is useful for doing a LEFT JOIN.
1298          *
1299          * The key of the array contains the table name or alias. The value is an
1300          * array with two elements, numbered 0 and 1. The first gives the type of
1301          * join, the second is an SQL fragment giving the join condition for that
1302          * table. For example:
1303          *
1304          *    array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
1305          *
1306          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1307          *   with no rows in it will be returned. If there was a query error, a
1308          *   DBQueryError exception will be thrown, except if the "ignore errors"
1309          *   option was set, in which case false will be returned.
1310          */
1311         public function select( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1312                 $options = array(), $join_conds = array() ) {
1313                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1314
1315                 return $this->query( $sql, $fname );
1316         }
1317
1318         /**
1319          * The equivalent of DatabaseBase::select() except that the constructed SQL
1320          * is returned, instead of being immediately executed. This can be useful for
1321          * doing UNION queries, where the SQL text of each query is needed. In general,
1322          * however, callers outside of Database classes should just use select().
1323          *
1324          * @param $table string|array Table name
1325          * @param $vars string|array Field names
1326          * @param $conds string|array Conditions
1327          * @param $fname string Caller function name
1328          * @param $options string|array Query options
1329          * @param $join_conds string|array Join conditions
1330          *
1331          * @return string SQL query string.
1332          * @see DatabaseBase::select()
1333          */
1334         public function selectSQLText( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1335                 $options = array(), $join_conds = array() )
1336         {
1337                 if ( is_array( $vars ) ) {
1338                         $vars = implode( ',', $vars );
1339                 }
1340
1341                 $options = (array)$options;
1342
1343                 if ( is_array( $table ) ) {
1344                         $useIndex = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1345                                 ? $options['USE INDEX']
1346                                 : array();
1347                         if ( count( $join_conds ) || count( $useIndex ) ) {
1348                                 $from = ' FROM ' .
1349                                         $this->tableNamesWithUseIndexOrJOIN( $table, $useIndex, $join_conds );
1350                         } else {
1351                                 $from = ' FROM ' . implode( ',', $this->tableNamesWithAlias( $table ) );
1352                         }
1353                 } elseif ( $table != '' ) {
1354                         if ( $table[0] == ' ' ) {
1355                                 $from = ' FROM ' . $table;
1356                         } else {
1357                                 $from = ' FROM ' . $this->tableName( $table );
1358                         }
1359                 } else {
1360                         $from = '';
1361                 }
1362
1363                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) = $this->makeSelectOptions( $options );
1364
1365                 if ( !empty( $conds ) ) {
1366                         if ( is_array( $conds ) ) {
1367                                 $conds = $this->makeList( $conds, LIST_AND );
1368                         }
1369                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1370                 } else {
1371                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1372                 }
1373
1374                 if ( isset( $options['LIMIT'] ) ) {
1375                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1376                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1377                 }
1378                 $sql = "$sql $postLimitTail";
1379
1380                 if ( isset( $options['EXPLAIN'] ) ) {
1381                         $sql = 'EXPLAIN ' . $sql;
1382                 }
1383
1384                 return $sql;
1385         }
1386
1387         /**
1388          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1389          * that a single row object is returned. If the query returns no rows,
1390          * false is returned.
1391          *
1392          * @param $table string|array Table name
1393          * @param $vars string|array Field names
1394          * @param $conds array Conditions
1395          * @param $fname string Caller function name
1396          * @param $options string|array Query options
1397          * @param $join_conds array|string Join conditions
1398          *
1399          * @return object|bool
1400          */
1401         public function selectRow( $table, $vars, $conds, $fname = 'DatabaseBase::selectRow',
1402                 $options = array(), $join_conds = array() )
1403         {
1404                 $options = (array)$options;
1405                 $options['LIMIT'] = 1;
1406                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1407
1408                 if ( $res === false ) {
1409                         return false;
1410                 }
1411
1412                 if ( !$this->numRows( $res ) ) {
1413                         return false;
1414                 }
1415
1416                 $obj = $this->fetchObject( $res );
1417
1418                 return $obj;
1419         }
1420
1421         /**
1422          * Estimate rows in dataset.
1423          *
1424          * MySQL allows you to estimate the number of rows that would be returned
1425          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1426          * index cardinality statistics, and is notoriously inaccurate, especially
1427          * when large numbers of rows have recently been added or deleted.
1428          *
1429          * For DBMSs that don't support fast result size estimation, this function
1430          * will actually perform the SELECT COUNT(*).
1431          *
1432          * Takes the same arguments as DatabaseBase::select().
1433          *
1434          * @param $table String: table name
1435          * @param Array|string $vars : unused
1436          * @param Array|string $conds : filters on the table
1437          * @param $fname String: function name for profiling
1438          * @param $options Array: options for select
1439          * @return Integer: row count
1440          */
1441         public function estimateRowCount( $table, $vars = '*', $conds = '',
1442                 $fname = 'DatabaseBase::estimateRowCount', $options = array() )
1443         {
1444                 $rows = 0;
1445                 $res = $this->select( $table, 'COUNT(*) AS rowcount', $conds, $fname, $options );
1446
1447                 if ( $res ) {
1448                         $row = $this->fetchRow( $res );
1449                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1450                 }
1451
1452                 return $rows;
1453         }
1454
1455         /**
1456          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1457          * It's only slightly flawed. Don't use for anything important.
1458          *
1459          * @param $sql String A SQL Query
1460          *
1461          * @return string
1462          */
1463         static function generalizeSQL( $sql ) {
1464                 # This does the same as the regexp below would do, but in such a way
1465                 # as to avoid crashing php on some large strings.
1466                 # $sql = preg_replace ( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql);
1467
1468                 $sql = str_replace ( "\\\\", '', $sql );
1469                 $sql = str_replace ( "\\'", '', $sql );
1470                 $sql = str_replace ( "\\\"", '', $sql );
1471                 $sql = preg_replace ( "/'.*'/s", "'X'", $sql );
1472                 $sql = preg_replace ( '/".*"/s', "'X'", $sql );
1473
1474                 # All newlines, tabs, etc replaced by single space
1475                 $sql = preg_replace ( '/\s+/', ' ', $sql );
1476
1477                 # All numbers => N
1478                 $sql = preg_replace ( '/-?[0-9]+/s', 'N', $sql );
1479
1480                 return $sql;
1481         }
1482
1483         /**
1484          * Determines whether a field exists in a table
1485          *
1486          * @param $table String: table name
1487          * @param $field String: filed to check on that table
1488          * @param $fname String: calling function name (optional)
1489          * @return Boolean: whether $table has filed $field
1490          */
1491         public function fieldExists( $table, $field, $fname = 'DatabaseBase::fieldExists' ) {
1492                 $info = $this->fieldInfo( $table, $field );
1493
1494                 return (bool)$info;
1495         }
1496
1497         /**
1498          * Determines whether an index exists
1499          * Usually throws a DBQueryError on failure
1500          * If errors are explicitly ignored, returns NULL on failure
1501          *
1502          * @param $table
1503          * @param $index
1504          * @param $fname string
1505          *
1506          * @return bool|null
1507          */
1508         public function indexExists( $table, $index, $fname = 'DatabaseBase::indexExists' ) {
1509                 $info = $this->indexInfo( $table, $index, $fname );
1510                 if ( is_null( $info ) ) {
1511                         return null;
1512                 } else {
1513                         return $info !== false;
1514                 }
1515         }
1516
1517         /**
1518          * Query whether a given table exists
1519          *
1520          * @param $table string
1521          * @param $fname string
1522          *
1523          * @return bool
1524          */
1525         public function tableExists( $table, $fname = __METHOD__ ) {
1526                 $table = $this->tableName( $table );
1527                 $old = $this->ignoreErrors( true );
1528                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1529                 $this->ignoreErrors( $old );
1530
1531                 return (bool)$res;
1532         }
1533
1534         /**
1535          * mysql_field_type() wrapper
1536          * @param $res
1537          * @param $index
1538          * @return string
1539          */
1540         public function fieldType( $res, $index ) {
1541                 if ( $res instanceof ResultWrapper ) {
1542                         $res = $res->result;
1543                 }
1544
1545                 return mysql_field_type( $res, $index );
1546         }
1547
1548         /**
1549          * Determines if a given index is unique
1550          *
1551          * @param $table string
1552          * @param $index string
1553          *
1554          * @return bool
1555          */
1556         public function indexUnique( $table, $index ) {
1557                 $indexInfo = $this->indexInfo( $table, $index );
1558
1559                 if ( !$indexInfo ) {
1560                         return null;
1561                 }
1562
1563                 return !$indexInfo[0]->Non_unique;
1564         }
1565
1566         /**
1567          * Helper for DatabaseBase::insert().
1568          *
1569          * @param $options array
1570          * @return string
1571          */
1572         protected function makeInsertOptions( $options ) {
1573                 return implode( ' ', $options );
1574         }
1575
1576         /**
1577          * INSERT wrapper, inserts an array into a table.
1578          *
1579          * $a may be either:
1580          *
1581          *   - A single associative array. The array keys are the field names, and
1582          *     the values are the values to insert. The values are treated as data
1583          *     and will be quoted appropriately. If NULL is inserted, this will be
1584          *     converted to a database NULL.
1585          *   - An array with numeric keys, holding a list of associative arrays.
1586          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1587          *     each subarray must be identical to each other, and in the same order.
1588          *
1589          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1590          * returns success.
1591          *
1592          * $options is an array of options, with boolean options encoded as values
1593          * with numeric keys, in the same style as $options in
1594          * DatabaseBase::select(). Supported options are:
1595          *
1596          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1597          *     any rows which cause duplicate key errors are not inserted. It's
1598          *     possible to determine how many rows were successfully inserted using
1599          *     DatabaseBase::affectedRows().
1600          *
1601          * @param $table   String Table name. This will be passed through
1602          *                 DatabaseBase::tableName().
1603          * @param $a       Array of rows to insert
1604          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1605          * @param $options Array of options
1606          *
1607          * @return bool
1608          */
1609         public function insert( $table, $a, $fname = 'DatabaseBase::insert', $options = array() ) {
1610                 # No rows to insert, easy just return now
1611                 if ( !count( $a ) ) {
1612                         return true;
1613                 }
1614
1615                 $table = $this->tableName( $table );
1616
1617                 if ( !is_array( $options ) ) {
1618                         $options = array( $options );
1619                 }
1620
1621                 $options = $this->makeInsertOptions( $options );
1622
1623                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1624                         $multi = true;
1625                         $keys = array_keys( $a[0] );
1626                 } else {
1627                         $multi = false;
1628                         $keys = array_keys( $a );
1629                 }
1630
1631                 $sql = 'INSERT ' . $options .
1632                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1633
1634                 if ( $multi ) {
1635                         $first = true;
1636                         foreach ( $a as $row ) {
1637                                 if ( $first ) {
1638                                         $first = false;
1639                                 } else {
1640                                         $sql .= ',';
1641                                 }
1642                                 $sql .= '(' . $this->makeList( $row ) . ')';
1643                         }
1644                 } else {
1645                         $sql .= '(' . $this->makeList( $a ) . ')';
1646                 }
1647
1648                 return (bool)$this->query( $sql, $fname );
1649         }
1650
1651         /**
1652          * Make UPDATE options for the DatabaseBase::update function
1653          *
1654          * @param $options Array: The options passed to DatabaseBase::update
1655          * @return string
1656          */
1657         protected function makeUpdateOptions( $options ) {
1658                 if ( !is_array( $options ) ) {
1659                         $options = array( $options );
1660                 }
1661
1662                 $opts = array();
1663
1664                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1665                         $opts[] = $this->lowPriorityOption();
1666                 }
1667
1668                 if ( in_array( 'IGNORE', $options ) ) {
1669                         $opts[] = 'IGNORE';
1670                 }
1671
1672                 return implode( ' ', $opts );
1673         }
1674
1675         /**
1676          * UPDATE wrapper. Takes a condition array and a SET array.
1677          *
1678          * @param $table  String name of the table to UPDATE. This will be passed through
1679          *                DatabaseBase::tableName().
1680          *
1681          * @param $values Array:  An array of values to SET. For each array element,
1682          *                the key gives the field name, and the value gives the data
1683          *                to set that field to. The data will be quoted by
1684          *                DatabaseBase::addQuotes().
1685          *
1686          * @param $conds  Array:  An array of conditions (WHERE). See
1687          *                DatabaseBase::select() for the details of the format of
1688          *                condition arrays. Use '*' to update all rows.
1689          *
1690          * @param $fname  String: The function name of the caller (from __METHOD__),
1691          *                for logging and profiling.
1692          *
1693          * @param $options Array: An array of UPDATE options, can be:
1694          *                   - IGNORE: Ignore unique key conflicts
1695          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1696          * @return Boolean
1697          */
1698         function update( $table, $values, $conds, $fname = 'DatabaseBase::update', $options = array() ) {
1699                 $table = $this->tableName( $table );
1700                 $opts = $this->makeUpdateOptions( $options );
1701                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1702
1703                 if ( $conds !== array() && $conds !== '*' ) {
1704                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1705                 }
1706
1707                 return $this->query( $sql, $fname );
1708         }
1709
1710         /**
1711          * Makes an encoded list of strings from an array
1712          * @param $a Array containing the data
1713          * @param $mode int Constant
1714          *      - LIST_COMMA:          comma separated, no field names
1715          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1716          *        the documentation for $conds in DatabaseBase::select().
1717          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1718          *      - LIST_SET:            comma separated with field names, like a SET clause
1719          *      - LIST_NAMES:          comma separated field names
1720          *
1721          * @return string
1722          */
1723         public function makeList( $a, $mode = LIST_COMMA ) {
1724                 if ( !is_array( $a ) ) {
1725                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1726                 }
1727
1728                 $first = true;
1729                 $list = '';
1730
1731                 foreach ( $a as $field => $value ) {
1732                         if ( !$first ) {
1733                                 if ( $mode == LIST_AND ) {
1734                                         $list .= ' AND ';
1735                                 } elseif ( $mode == LIST_OR ) {
1736                                         $list .= ' OR ';
1737                                 } else {
1738                                         $list .= ',';
1739                                 }
1740                         } else {
1741                                 $first = false;
1742                         }
1743
1744                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1745                                 $list .= "($value)";
1746                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1747                                 $list .= "$value";
1748                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1749                                 if ( count( $value ) == 0 ) {
1750                                         throw new MWException( __METHOD__ . ': empty input' );
1751                                 } elseif ( count( $value ) == 1 ) {
1752                                         // Special-case single values, as IN isn't terribly efficient
1753                                         // Don't necessarily assume the single key is 0; we don't
1754                                         // enforce linear numeric ordering on other arrays here.
1755                                         $value = array_values( $value );
1756                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1757                                 } else {
1758                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1759                                 }
1760                         } elseif ( $value === null ) {
1761                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1762                                         $list .= "$field IS ";
1763                                 } elseif ( $mode == LIST_SET ) {
1764                                         $list .= "$field = ";
1765                                 }
1766                                 $list .= 'NULL';
1767                         } else {
1768                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1769                                         $list .= "$field = ";
1770                                 }
1771                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1772                         }
1773                 }
1774
1775                 return $list;
1776         }
1777
1778         /**
1779          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1780          * The keys on each level may be either integers or strings.
1781          *
1782          * @param $data Array: organized as 2-d
1783          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
1784          * @param $baseKey String: field name to match the base-level keys to (eg 'pl_namespace')
1785          * @param $subKey String: field name to match the sub-level keys to (eg 'pl_title')
1786          * @return Mixed: string SQL fragment, or false if no items in array.
1787          */
1788         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1789                 $conds = array();
1790
1791                 foreach ( $data as $base => $sub ) {
1792                         if ( count( $sub ) ) {
1793                                 $conds[] = $this->makeList(
1794                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1795                                         LIST_AND );
1796                         }
1797                 }
1798
1799                 if ( $conds ) {
1800                         return $this->makeList( $conds, LIST_OR );
1801                 } else {
1802                         // Nothing to search for...
1803                         return false;
1804                 }
1805         }
1806
1807         /**
1808          * Return aggregated value alias
1809          *
1810          * @param $valuedata
1811          * @param $valuename string
1812          *
1813          * @return string
1814          */
1815         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1816                 return $valuename;
1817         }
1818
1819         /**
1820          * @param $field
1821          * @return string
1822          */
1823         public function bitNot( $field ) {
1824                 return "(~$field)";
1825         }
1826
1827         /**
1828          * @param $fieldLeft
1829          * @param $fieldRight
1830          * @return string
1831          */
1832         public function bitAnd( $fieldLeft, $fieldRight ) {
1833                 return "($fieldLeft & $fieldRight)";
1834         }
1835
1836         /**
1837          * @param  $fieldLeft
1838          * @param  $fieldRight
1839          * @return string
1840          */
1841         public function bitOr( $fieldLeft, $fieldRight ) {
1842                 return "($fieldLeft | $fieldRight)";
1843         }
1844
1845         /**
1846          * Build a concatenation list to feed into a SQL query
1847          * @param $stringList Array: list of raw SQL expressions; caller is responsible for any quoting
1848          * @return String
1849          */
1850         public function buildConcat( $stringList ) {
1851                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1852         }
1853
1854         /**
1855          * Change the current database
1856          *
1857          * @todo Explain what exactly will fail if this is not overridden.
1858          *
1859          * @param $db
1860          *
1861          * @return bool Success or failure
1862          */
1863         public function selectDB( $db ) {
1864                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
1865                 # if your database engine supports a concept similar to MySQL's
1866                 # databases you may as well.
1867                 $this->mDBname = $db;
1868                 return true;
1869         }
1870
1871         /**
1872          * Get the current DB name
1873          */
1874         public function getDBname() {
1875                 return $this->mDBname;
1876         }
1877
1878         /**
1879          * Get the server hostname or IP address
1880          */
1881         public function getServer() {
1882                 return $this->mServer;
1883         }
1884
1885         /**
1886          * Format a table name ready for use in constructing an SQL query
1887          *
1888          * This does two important things: it quotes the table names to clean them up,
1889          * and it adds a table prefix if only given a table name with no quotes.
1890          *
1891          * All functions of this object which require a table name call this function
1892          * themselves. Pass the canonical name to such functions. This is only needed
1893          * when calling query() directly.
1894          *
1895          * @param $name String: database table name
1896          * @param $format String One of:
1897          *   quoted - Automatically pass the table name through addIdentifierQuotes()
1898          *            so that it can be used in a query.
1899          *   raw - Do not add identifier quotes to the table name
1900          * @return String: full database name
1901          */
1902         public function tableName( $name, $format = 'quoted' ) {
1903                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
1904                 # Skip the entire process when we have a string quoted on both ends.
1905                 # Note that we check the end so that we will still quote any use of
1906                 # use of `database`.table. But won't break things if someone wants
1907                 # to query a database table with a dot in the name.
1908                 if ( $this->isQuotedIdentifier( $name ) ) {
1909                         return $name;
1910                 }
1911
1912                 # Lets test for any bits of text that should never show up in a table
1913                 # name. Basically anything like JOIN or ON which are actually part of
1914                 # SQL queries, but may end up inside of the table value to combine
1915                 # sql. Such as how the API is doing.
1916                 # Note that we use a whitespace test rather than a \b test to avoid
1917                 # any remote case where a word like on may be inside of a table name
1918                 # surrounded by symbols which may be considered word breaks.
1919                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1920                         return $name;
1921                 }
1922
1923                 # Split database and table into proper variables.
1924                 # We reverse the explode so that database.table and table both output
1925                 # the correct table.
1926                 $dbDetails = array_reverse( explode( '.', $name, 2 ) );
1927                 if ( isset( $dbDetails[1] ) ) {
1928                         list( $table, $database ) = $dbDetails;
1929                 } else {
1930                         list( $table ) = $dbDetails;
1931                 }
1932                 $prefix = $this->mTablePrefix; # Default prefix
1933
1934                 # A database name has been specified in input. We don't want any
1935                 # prefixes added.
1936                 if ( isset( $database ) ) {
1937                         $prefix = '';
1938                 }
1939
1940                 # Note that we use the long format because php will complain in in_array if
1941                 # the input is not an array, and will complain in is_array if it is not set.
1942                 if ( !isset( $database ) # Don't use shared database if pre selected.
1943                  && isset( $wgSharedDB ) # We have a shared database
1944                  && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
1945                  && isset( $wgSharedTables )
1946                  && is_array( $wgSharedTables )
1947                  && in_array( $table, $wgSharedTables ) ) { # A shared table is selected
1948                         $database = $wgSharedDB;
1949                         $prefix   = isset( $wgSharedPrefix ) ? $wgSharedPrefix : $prefix;
1950                 }
1951
1952                 # Quote the $database and $table and apply the prefix if not quoted.
1953                 if ( isset( $database ) ) {
1954                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
1955                                 $database = $this->addIdentifierQuotes( $database );
1956                         }
1957                 }
1958
1959                 $table = "{$prefix}{$table}";
1960                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $table ) ) {
1961                         $table = $this->addIdentifierQuotes( "{$table}" );
1962                 }
1963
1964                 # Merge our database and table into our final table name.
1965                 $tableName = ( isset( $database ) ? "{$database}.{$table}" : "{$table}" );
1966
1967                 return $tableName;
1968         }
1969
1970         /**
1971          * Fetch a number of table names into an array
1972          * This is handy when you need to construct SQL for joins
1973          *
1974          * Example:
1975          * extract($dbr->tableNames('user','watchlist'));
1976          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
1977          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
1978          *
1979          * @return array
1980          */
1981         public function tableNames() {
1982                 $inArray = func_get_args();
1983                 $retVal = array();
1984
1985                 foreach ( $inArray as $name ) {
1986                         $retVal[$name] = $this->tableName( $name );
1987                 }
1988
1989                 return $retVal;
1990         }
1991
1992         /**
1993          * Fetch a number of table names into an zero-indexed numerical array
1994          * This is handy when you need to construct SQL for joins
1995          *
1996          * Example:
1997          * list( $user, $watchlist ) = $dbr->tableNamesN('user','watchlist');
1998          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
1999          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2000          *
2001          * @return array
2002          */
2003         public function tableNamesN() {
2004                 $inArray = func_get_args();
2005                 $retVal = array();
2006
2007                 foreach ( $inArray as $name ) {
2008                         $retVal[] = $this->tableName( $name );
2009                 }
2010
2011                 return $retVal;
2012         }
2013
2014         /**
2015          * Get an aliased table name
2016          * e.g. tableName AS newTableName
2017          *
2018          * @param $name string Table name, see tableName()
2019          * @param $alias string|bool Alias (optional)
2020          * @return string SQL name for aliased table. Will not alias a table to its own name
2021          */
2022         public function tableNameWithAlias( $name, $alias = false ) {
2023                 if ( !$alias || $alias == $name ) {
2024                         return $this->tableName( $name );
2025                 } else {
2026                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2027                 }
2028         }
2029
2030         /**
2031          * Gets an array of aliased table names
2032          *
2033          * @param $tables array( [alias] => table )
2034          * @return array of strings, see tableNameWithAlias()
2035          */
2036         public function tableNamesWithAlias( $tables ) {
2037                 $retval = array();
2038                 foreach ( $tables as $alias => $table ) {
2039                         if ( is_numeric( $alias ) ) {
2040                                 $alias = $table;
2041                         }
2042                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2043                 }
2044                 return $retval;
2045         }
2046
2047         /**
2048          * Get the aliased table name clause for a FROM clause
2049          * which might have a JOIN and/or USE INDEX clause
2050          *
2051          * @param $tables array ( [alias] => table )
2052          * @param $use_index array Same as for select()
2053          * @param $join_conds array Same as for select()
2054          * @return string
2055          */
2056         protected function tableNamesWithUseIndexOrJOIN(
2057                 $tables, $use_index = array(), $join_conds = array()
2058         ) {
2059                 $ret = array();
2060                 $retJOIN = array();
2061                 $use_index = (array)$use_index;
2062                 $join_conds = (array)$join_conds;
2063
2064                 foreach ( $tables as $alias => $table ) {
2065                         if ( !is_string( $alias ) ) {
2066                                 // No alias? Set it equal to the table name
2067                                 $alias = $table;
2068                         }
2069                         // Is there a JOIN clause for this table?
2070                         if ( isset( $join_conds[$alias] ) ) {
2071                                 list( $joinType, $conds ) = $join_conds[$alias];
2072                                 $tableClause = $joinType;
2073                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2074                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2075                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2076                                         if ( $use != '' ) {
2077                                                 $tableClause .= ' ' . $use;
2078                                         }
2079                                 }
2080                                 $on = $this->makeList( (array)$conds, LIST_AND );
2081                                 if ( $on != '' ) {
2082                                         $tableClause .= ' ON (' . $on . ')';
2083                                 }
2084
2085                                 $retJOIN[] = $tableClause;
2086                         // Is there an INDEX clause for this table?
2087                         } elseif ( isset( $use_index[$alias] ) ) {
2088                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2089                                 $tableClause .= ' ' . $this->useIndexClause(
2090                                         implode( ',', (array)$use_index[$alias] ) );
2091
2092                                 $ret[] = $tableClause;
2093                         } else {
2094                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2095
2096                                 $ret[] = $tableClause;
2097                         }
2098                 }
2099
2100                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2101                 $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2102                 $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2103
2104                 // Compile our final table clause
2105                 return implode( ' ', array( $straightJoins, $otherJoins ) );
2106         }
2107
2108         /**
2109          * Get the name of an index in a given table
2110          *
2111          * @param $index
2112          *
2113          * @return string
2114          */
2115         protected function indexName( $index ) {
2116                 // Backwards-compatibility hack
2117                 $renamed = array(
2118                         'ar_usertext_timestamp' => 'usertext_timestamp',
2119                         'un_user_id'            => 'user_id',
2120                         'un_user_ip'            => 'user_ip',
2121                 );
2122
2123                 if ( isset( $renamed[$index] ) ) {
2124                         return $renamed[$index];
2125                 } else {
2126                         return $index;
2127                 }
2128         }
2129
2130         /**
2131          * If it's a string, adds quotes and backslashes
2132          * Otherwise returns as-is
2133          *
2134          * @param $s string
2135          *
2136          * @return string
2137          */
2138         public function addQuotes( $s ) {
2139                 if ( $s === null ) {
2140                         return 'NULL';
2141                 } else {
2142                         # This will also quote numeric values. This should be harmless,
2143                         # and protects against weird problems that occur when they really
2144                         # _are_ strings such as article titles and string->number->string
2145                         # conversion is not 1:1.
2146                         return "'" . $this->strencode( $s ) . "'";
2147                 }
2148         }
2149
2150         /**
2151          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2152          * MySQL uses `backticks` while basically everything else uses double quotes.
2153          * Since MySQL is the odd one out here the double quotes are our generic
2154          * and we implement backticks in DatabaseMysql.
2155          *
2156          * @param $s string
2157          *
2158          * @return string
2159          */
2160         public function addIdentifierQuotes( $s ) {
2161                 return '"' . str_replace( '"', '""', $s ) . '"';
2162         }
2163
2164         /**
2165          * Returns if the given identifier looks quoted or not according to
2166          * the database convention for quoting identifiers .
2167          *
2168          * @param $name string
2169          *
2170          * @return boolean
2171          */
2172         public function isQuotedIdentifier( $name ) {
2173                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2174         }
2175
2176         /**
2177          * @param $s string
2178          * @return string
2179          */
2180         protected function escapeLikeInternal( $s ) {
2181                 $s = str_replace( '\\', '\\\\', $s );
2182                 $s = $this->strencode( $s );
2183                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2184
2185                 return $s;
2186         }
2187
2188         /**
2189          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2190          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2191          * Alternatively, the function could be provided with an array of aforementioned parameters.
2192          *
2193          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2194          * for subpages of 'My page title'.
2195          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2196          *
2197          * @since 1.16
2198          * @return String: fully built LIKE statement
2199          */
2200         public function buildLike() {
2201                 $params = func_get_args();
2202
2203                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2204                         $params = $params[0];
2205                 }
2206
2207                 $s = '';
2208
2209                 foreach ( $params as $value ) {
2210                         if ( $value instanceof LikeMatch ) {
2211                                 $s .= $value->toString();
2212                         } else {
2213                                 $s .= $this->escapeLikeInternal( $value );
2214                         }
2215                 }
2216
2217                 return " LIKE '" . $s . "' ";
2218         }
2219
2220         /**
2221          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2222          *
2223          * @return LikeMatch
2224          */
2225         public function anyChar() {
2226                 return new LikeMatch( '_' );
2227         }
2228
2229         /**
2230          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2231          *
2232          * @return LikeMatch
2233          */
2234         public function anyString() {
2235                 return new LikeMatch( '%' );
2236         }
2237
2238         /**
2239          * Returns an appropriately quoted sequence value for inserting a new row.
2240          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2241          * subclass will return an integer, and save the value for insertId()
2242          *
2243          * Any implementation of this function should *not* involve reusing
2244          * sequence numbers created for rolled-back transactions.
2245          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2246          * @param $seqName string
2247          * @return null
2248          */
2249         public function nextSequenceValue( $seqName ) {
2250                 return null;
2251         }
2252
2253         /**
2254          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2255          * is only needed because a) MySQL must be as efficient as possible due to
2256          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2257          * which index to pick.  Anyway, other databases might have different
2258          * indexes on a given table.  So don't bother overriding this unless you're
2259          * MySQL.
2260          * @param $index
2261          * @return string
2262          */
2263         public function useIndexClause( $index ) {
2264                 return '';
2265         }
2266
2267         /**
2268          * REPLACE query wrapper.
2269          *
2270          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2271          * except that when there is a duplicate key error, the old row is deleted
2272          * and the new row is inserted in its place.
2273          *
2274          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2275          * perform the delete, we need to know what the unique indexes are so that
2276          * we know how to find the conflicting rows.
2277          *
2278          * It may be more efficient to leave off unique indexes which are unlikely
2279          * to collide. However if you do this, you run the risk of encountering
2280          * errors which wouldn't have occurred in MySQL.
2281          *
2282          * @param $table String: The table to replace the row(s) in.
2283          * @param $rows array Can be either a single row to insert, or multiple rows,
2284          *    in the same format as for DatabaseBase::insert()
2285          * @param $uniqueIndexes array is an array of indexes. Each element may be either
2286          *    a field name or an array of field names
2287          * @param $fname String: Calling function name (use __METHOD__) for logs/profiling
2288          */
2289         public function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseBase::replace' ) {
2290                 $quotedTable = $this->tableName( $table );
2291
2292                 if ( count( $rows ) == 0 ) {
2293                         return;
2294                 }
2295
2296                 # Single row case
2297                 if ( !is_array( reset( $rows ) ) ) {
2298                         $rows = array( $rows );
2299                 }
2300
2301                 foreach( $rows as $row ) {
2302                         # Delete rows which collide
2303                         if ( $uniqueIndexes ) {
2304                                 $sql = "DELETE FROM $quotedTable WHERE ";
2305                                 $first = true;
2306                                 foreach ( $uniqueIndexes as $index ) {
2307                                         if ( $first ) {
2308                                                 $first = false;
2309                                                 $sql .= '( ';
2310                                         } else {
2311                                                 $sql .= ' ) OR ( ';
2312                                         }
2313                                         if ( is_array( $index ) ) {
2314                                                 $first2 = true;
2315                                                 foreach ( $index as $col ) {
2316                                                         if ( $first2 ) {
2317                                                                 $first2 = false;
2318                                                         } else {
2319                                                                 $sql .= ' AND ';
2320                                                         }
2321                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2322                                                 }
2323                                         } else {
2324                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2325                                         }
2326                                 }
2327                                 $sql .= ' )';
2328                                 $this->query( $sql, $fname );
2329                         }
2330
2331                         # Now insert the row
2332                         $this->insert( $table, $row );
2333                 }
2334         }
2335
2336         /**
2337          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2338          * statement.
2339          *
2340          * @param $table string Table name
2341          * @param $rows array Rows to insert
2342          * @param $fname string Caller function name
2343          *
2344          * @return ResultWrapper
2345          */
2346         protected function nativeReplace( $table, $rows, $fname ) {
2347                 $table = $this->tableName( $table );
2348
2349                 # Single row case
2350                 if ( !is_array( reset( $rows ) ) ) {
2351                         $rows = array( $rows );
2352                 }
2353
2354                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2355                 $first = true;
2356
2357                 foreach ( $rows as $row ) {
2358                         if ( $first ) {
2359                                 $first = false;
2360                         } else {
2361                                 $sql .= ',';
2362                         }
2363
2364                         $sql .= '(' . $this->makeList( $row ) . ')';
2365                 }
2366
2367                 return $this->query( $sql, $fname );
2368         }
2369
2370         /**
2371          * DELETE where the condition is a join.
2372          *
2373          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2374          * we use sub-selects
2375          *
2376          * For safety, an empty $conds will not delete everything. If you want to
2377          * delete all rows where the join condition matches, set $conds='*'.
2378          *
2379          * DO NOT put the join condition in $conds.
2380          *
2381          * @param $delTable   String: The table to delete from.
2382          * @param $joinTable  String: The other table.
2383          * @param $delVar     String: The variable to join on, in the first table.
2384          * @param $joinVar    String: The variable to join on, in the second table.
2385          * @param $conds      Array: Condition array of field names mapped to variables,
2386          *                    ANDed together in the WHERE clause
2387          * @param $fname      String: Calling function name (use __METHOD__) for
2388          *                    logs/profiling
2389          */
2390         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2391                 $fname = 'DatabaseBase::deleteJoin' )
2392         {
2393                 if ( !$conds ) {
2394                         throw new DBUnexpectedError( $this,
2395                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2396                 }
2397
2398                 $delTable = $this->tableName( $delTable );
2399                 $joinTable = $this->tableName( $joinTable );
2400                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2401                 if ( $conds != '*' ) {
2402                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2403                 }
2404                 $sql .= ')';
2405
2406                 $this->query( $sql, $fname );
2407         }
2408
2409         /**
2410          * Returns the size of a text field, or -1 for "unlimited"
2411          *
2412          * @param $table string
2413          * @param $field string
2414          *
2415          * @return int
2416          */
2417         public function textFieldSize( $table, $field ) {
2418                 $table = $this->tableName( $table );
2419                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2420                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2421                 $row = $this->fetchObject( $res );
2422
2423                 $m = array();
2424
2425                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2426                         $size = $m[1];
2427                 } else {
2428                         $size = -1;
2429                 }
2430
2431                 return $size;
2432         }
2433
2434         /**
2435          * A string to insert into queries to show that they're low-priority, like
2436          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2437          * string and nothing bad should happen.
2438          *
2439          * @return string Returns the text of the low priority option if it is
2440          *   supported, or a blank string otherwise
2441          */
2442         public function lowPriorityOption() {
2443                 return '';
2444         }
2445
2446         /**
2447          * DELETE query wrapper.
2448          *
2449          * @param $table Array Table name
2450          * @param $conds String|Array of conditions. See $conds in DatabaseBase::select() for
2451          *               the format. Use $conds == "*" to delete all rows
2452          * @param $fname String name of the calling function
2453          *
2454          * @return bool
2455          */
2456         public function delete( $table, $conds, $fname = 'DatabaseBase::delete' ) {
2457                 if ( !$conds ) {
2458                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2459                 }
2460
2461                 $table = $this->tableName( $table );
2462                 $sql = "DELETE FROM $table";
2463
2464                 if ( $conds != '*' ) {
2465                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2466                 }
2467
2468                 return $this->query( $sql, $fname );
2469         }
2470
2471         /**
2472          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2473          * into another table.
2474          *
2475          * @param $destTable string The table name to insert into
2476          * @param $srcTable string|array May be either a table name, or an array of table names
2477          *    to include in a join.
2478          *
2479          * @param $varMap array must be an associative array of the form
2480          *    array( 'dest1' => 'source1', ...). Source items may be literals
2481          *    rather than field names, but strings should be quoted with
2482          *    DatabaseBase::addQuotes()
2483          *
2484          * @param $conds array Condition array. See $conds in DatabaseBase::select() for
2485          *    the details of the format of condition arrays. May be "*" to copy the
2486          *    whole table.
2487          *
2488          * @param $fname string The function name of the caller, from __METHOD__
2489          *
2490          * @param $insertOptions array Options for the INSERT part of the query, see
2491          *    DatabaseBase::insert() for details.
2492          * @param $selectOptions array Options for the SELECT part of the query, see
2493          *    DatabaseBase::select() for details.
2494          *
2495          * @return ResultWrapper
2496          */
2497         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2498                 $fname = 'DatabaseBase::insertSelect',
2499                 $insertOptions = array(), $selectOptions = array() )
2500         {
2501                 $destTable = $this->tableName( $destTable );
2502
2503                 if ( is_array( $insertOptions ) ) {
2504                         $insertOptions = implode( ' ', $insertOptions );
2505                 }
2506
2507                 if ( !is_array( $selectOptions ) ) {
2508                         $selectOptions = array( $selectOptions );
2509                 }
2510
2511                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2512
2513                 if ( is_array( $srcTable ) ) {
2514                         $srcTable =  implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2515                 } else {
2516                         $srcTable = $this->tableName( $srcTable );
2517                 }
2518
2519                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2520                         " SELECT $startOpts " . implode( ',', $varMap ) .
2521                         " FROM $srcTable $useIndex ";
2522
2523                 if ( $conds != '*' ) {
2524                         if ( is_array( $conds ) ) {
2525                                 $conds = $this->makeList( $conds, LIST_AND );
2526                         }
2527                         $sql .= " WHERE $conds";
2528                 }
2529
2530                 $sql .= " $tailOpts";
2531
2532                 return $this->query( $sql, $fname );
2533         }
2534
2535         /**
2536          * Construct a LIMIT query with optional offset.  This is used for query
2537          * pages.  The SQL should be adjusted so that only the first $limit rows
2538          * are returned.  If $offset is provided as well, then the first $offset
2539          * rows should be discarded, and the next $limit rows should be returned.
2540          * If the result of the query is not ordered, then the rows to be returned
2541          * are theoretically arbitrary.
2542          *
2543          * $sql is expected to be a SELECT, if that makes a difference.
2544          *
2545          * The version provided by default works in MySQL and SQLite.  It will very
2546          * likely need to be overridden for most other DBMSes.
2547          *
2548          * @param $sql String SQL query we will append the limit too
2549          * @param $limit Integer the SQL limit
2550          * @param $offset Integer|bool the SQL offset (default false)
2551          *
2552          * @return string
2553          */
2554         public function limitResult( $sql, $limit, $offset = false ) {
2555                 if ( !is_numeric( $limit ) ) {
2556                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2557                 }
2558                 return "$sql LIMIT "
2559                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2560                         . "{$limit} ";
2561         }
2562
2563         /**
2564          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2565          * within the UNION construct.
2566          * @return Boolean
2567          */
2568         public function unionSupportsOrderAndLimit() {
2569                 return true; // True for almost every DB supported
2570         }
2571
2572         /**
2573          * Construct a UNION query
2574          * This is used for providing overload point for other DB abstractions
2575          * not compatible with the MySQL syntax.
2576          * @param $sqls Array: SQL statements to combine
2577          * @param $all Boolean: use UNION ALL
2578          * @return String: SQL fragment
2579          */
2580         public function unionQueries( $sqls, $all ) {
2581                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2582                 return '(' . implode( $glue, $sqls ) . ')';
2583         }
2584
2585         /**
2586          * Returns an SQL expression for a simple conditional.  This doesn't need
2587          * to be overridden unless CASE isn't supported in your DBMS.
2588          *
2589          * @param $cond String: SQL expression which will result in a boolean value
2590          * @param $trueVal String: SQL expression to return if true
2591          * @param $falseVal String: SQL expression to return if false
2592          * @return String: SQL fragment
2593          */
2594         public function conditional( $cond, $trueVal, $falseVal ) {
2595                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2596         }
2597
2598         /**
2599          * Returns a comand for str_replace function in SQL query.
2600          * Uses REPLACE() in MySQL
2601          *
2602          * @param $orig String: column to modify
2603          * @param $old String: column to seek
2604          * @param $new String: column to replace with
2605          *
2606          * @return string
2607          */
2608         public function strreplace( $orig, $old, $new ) {
2609                 return "REPLACE({$orig}, {$old}, {$new})";
2610         }
2611
2612         /**
2613          * Determines how long the server has been up
2614          * STUB
2615          *
2616          * @return int
2617          */
2618         public function getServerUptime() {
2619                 return 0;
2620         }
2621
2622         /**
2623          * Determines if the last failure was due to a deadlock
2624          * STUB
2625          *
2626          * @return bool
2627          */
2628         public function wasDeadlock() {
2629                 return false;
2630         }
2631
2632         /**
2633          * Determines if the last failure was due to a lock timeout
2634          * STUB
2635          *
2636          * @return bool
2637          */
2638         public function wasLockTimeout() {
2639                 return false;
2640         }
2641
2642         /**
2643          * Determines if the last query error was something that should be dealt
2644          * with by pinging the connection and reissuing the query.
2645          * STUB
2646          *
2647          * @return bool
2648          */
2649         public function wasErrorReissuable() {
2650                 return false;
2651         }
2652
2653         /**
2654          * Determines if the last failure was due to the database being read-only.
2655          * STUB
2656          *
2657          * @return bool
2658          */
2659         public function wasReadOnlyError() {
2660                 return false;
2661         }
2662
2663         /**
2664          * Perform a deadlock-prone transaction.
2665          *
2666          * This function invokes a callback function to perform a set of write
2667          * queries. If a deadlock occurs during the processing, the transaction
2668          * will be rolled back and the callback function will be called again.
2669          *
2670          * Usage:
2671          *   $dbw->deadlockLoop( callback, ... );
2672          *
2673          * Extra arguments are passed through to the specified callback function.
2674          *
2675          * Returns whatever the callback function returned on its successful,
2676          * iteration, or false on error, for example if the retry limit was
2677          * reached.
2678          *
2679          * @return bool
2680          */
2681         public function deadlockLoop() {
2682                 $this->begin( __METHOD__ );
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( __METHOD__ );
2714                         $this->reportQueryError( $error, $errno, $sql, $fname );
2715                         return false;
2716                 } else {
2717                         $this->commit( __METHOD__ );
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 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         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2734                 wfProfileIn( __METHOD__ );
2735
2736                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2737                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
2738
2739                         if ( $wait > $timeout * 1e6 ) {
2740                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
2741                                 wfProfileOut( __METHOD__ );
2742                                 return -1;
2743                         } elseif ( $wait > 0 ) {
2744                                 wfDebug( "Fake slave waiting $wait us\n" );
2745                                 usleep( $wait );
2746                                 wfProfileOut( __METHOD__ );
2747                                 return 1;
2748                         } else {
2749                                 wfDebug( "Fake slave up to date ($wait us)\n" );
2750                                 wfProfileOut( __METHOD__ );
2751                                 return 0;
2752                         }
2753                 }
2754
2755                 wfProfileOut( __METHOD__ );
2756
2757                 # Real waits are implemented in the subclass.
2758                 return 0;
2759         }
2760
2761         /**
2762          * Get the replication position of this slave
2763          *
2764          * @return DBMasterPos, or false if this is not a slave.
2765          */
2766         public function getSlavePos() {
2767                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2768                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
2769                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
2770                         return $pos;
2771                 } else {
2772                         # Stub
2773                         return false;
2774                 }
2775         }
2776
2777         /**
2778          * Get the position of this master
2779          *
2780          * @return DBMasterPos, or false if this is not a master
2781          */
2782         public function getMasterPos() {
2783                 if ( $this->mFakeMaster ) {
2784                         return new MySQLMasterPos( 'fake', microtime( true ) );
2785                 } else {
2786                         return false;
2787                 }
2788         }
2789
2790         /**
2791          * Begin a transaction
2792          *
2793          * @param $fname string
2794          */
2795         public function begin( $fname = 'DatabaseBase::begin' ) {
2796                 $this->query( 'BEGIN', $fname );
2797                 $this->mTrxLevel = 1;
2798         }
2799
2800         /**
2801          * End a transaction
2802          *
2803          * @param $fname string
2804          */
2805         public function commit( $fname = 'DatabaseBase::commit' ) {
2806                 if ( $this->mTrxLevel ) {
2807                         $this->query( 'COMMIT', $fname );
2808                         $this->mTrxLevel = 0;
2809                 }
2810         }
2811
2812         /**
2813          * Rollback a transaction.
2814          * No-op on non-transactional databases.
2815          *
2816          * @param $fname string
2817          */
2818         public function rollback( $fname = 'DatabaseBase::rollback' ) {
2819                 if ( $this->mTrxLevel ) {
2820                         $this->query( 'ROLLBACK', $fname, true );
2821                         $this->mTrxLevel = 0;
2822                 }
2823         }
2824
2825         /**
2826          * Creates a new table with structure copied from existing table
2827          * Note that unlike most database abstraction functions, this function does not
2828          * automatically append database prefix, because it works at a lower
2829          * abstraction level.
2830          * The table names passed to this function shall not be quoted (this
2831          * function calls addIdentifierQuotes when needed).
2832          *
2833          * @param $oldName String: name of table whose structure should be copied
2834          * @param $newName String: name of table to be created
2835          * @param $temporary Boolean: whether the new table should be temporary
2836          * @param $fname String: calling function name
2837          * @return Boolean: true if operation was successful
2838          */
2839         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
2840                 $fname = 'DatabaseBase::duplicateTableStructure' )
2841         {
2842                 throw new MWException(
2843                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
2844         }
2845
2846         /**
2847          * List all tables on the database
2848          *
2849          * @param $prefix string Only show tables with this prefix, e.g. mw_
2850          * @param $fname String: calling function name
2851          */
2852         function listTables( $prefix = null, $fname = 'DatabaseBase::listTables' ) {
2853                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
2854         }
2855
2856         /**
2857          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2858          * to the format used for inserting into timestamp fields in this DBMS.
2859          *
2860          * The result is unquoted, and needs to be passed through addQuotes()
2861          * before it can be included in raw SQL.
2862          *
2863          * @param $ts string|int
2864          *
2865          * @return string
2866          */
2867         public function timestamp( $ts = 0 ) {
2868                 return wfTimestamp( TS_MW, $ts );
2869         }
2870
2871         /**
2872          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2873          * to the format used for inserting into timestamp fields in this DBMS. If
2874          * NULL is input, it is passed through, allowing NULL values to be inserted
2875          * into timestamp fields.
2876          *
2877          * The result is unquoted, and needs to be passed through addQuotes()
2878          * before it can be included in raw SQL.
2879          *
2880          * @param $ts string|int
2881          *
2882          * @return string
2883          */
2884         public function timestampOrNull( $ts = null ) {
2885                 if ( is_null( $ts ) ) {
2886                         return null;
2887                 } else {
2888                         return $this->timestamp( $ts );
2889                 }
2890         }
2891
2892         /**
2893          * Take the result from a query, and wrap it in a ResultWrapper if
2894          * necessary. Boolean values are passed through as is, to indicate success
2895          * of write queries or failure.
2896          *
2897          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
2898          * resource, and it was necessary to call this function to convert it to
2899          * a wrapper. Nowadays, raw database objects are never exposed to external
2900          * callers, so this is unnecessary in external code. For compatibility with
2901          * old code, ResultWrapper objects are passed through unaltered.
2902          *
2903          * @param $result bool|ResultWrapper
2904          *
2905          * @return bool|ResultWrapper
2906          */
2907         public function resultObject( $result ) {
2908                 if ( empty( $result ) ) {
2909                         return false;
2910                 } elseif ( $result instanceof ResultWrapper ) {
2911                         return $result;
2912                 } elseif ( $result === true ) {
2913                         // Successful write query
2914                         return $result;
2915                 } else {
2916                         return new ResultWrapper( $this, $result );
2917                 }
2918         }
2919
2920         /**
2921          * Ping the server and try to reconnect if it there is no connection
2922          *
2923          * @return bool Success or failure
2924          */
2925         public function ping() {
2926                 # Stub.  Not essential to override.
2927                 return true;
2928         }
2929
2930         /**
2931          * Get slave lag. Currently supported only by MySQL.
2932          *
2933          * Note that this function will generate a fatal error on many
2934          * installations. Most callers should use LoadBalancer::safeGetLag()
2935          * instead.
2936          *
2937          * @return int Database replication lag in seconds
2938          */
2939         public function getLag() {
2940                 return intval( $this->mFakeSlaveLag );
2941         }
2942
2943         /**
2944          * Return the maximum number of items allowed in a list, or 0 for unlimited.
2945          *
2946          * @return int
2947          */
2948         function maxListLen() {
2949                 return 0;
2950         }
2951
2952         /**
2953          * Some DBMSs have a special format for inserting into blob fields, they
2954          * don't allow simple quoted strings to be inserted. To insert into such
2955          * a field, pass the data through this function before passing it to
2956          * DatabaseBase::insert().
2957          * @param $b string
2958          * @return string
2959          */
2960         public function encodeBlob( $b ) {
2961                 return $b;
2962         }
2963
2964         /**
2965          * Some DBMSs return a special placeholder object representing blob fields
2966          * in result objects. Pass the object through this function to return the
2967          * original string.
2968          * @param $b string
2969          * @return string
2970          */
2971         public function decodeBlob( $b ) {
2972                 return $b;
2973         }
2974
2975         /**
2976          * Override database's default behavior. $options include:
2977          *     'connTimeout' : Set the connection timeout value in seconds.
2978          *                     May be useful for very long batch queries such as
2979          *                     full-wiki dumps, where a single query reads out over
2980          *                     hours or days.
2981          *
2982          * @param $options Array
2983          * @return void
2984          */
2985         public function setSessionOptions( array $options ) {}
2986
2987         /**
2988          * Read and execute SQL commands from a file.
2989          *
2990          * Returns true on success, error string or exception on failure (depending
2991          * on object's error ignore settings).
2992          *
2993          * @param $filename String: File name to open
2994          * @param $lineCallback Callback: Optional function called before reading each line
2995          * @param $resultCallback Callback: Optional function called for each MySQL result
2996          * @param $fname String: Calling function name or false if name should be
2997          *      generated dynamically using $filename
2998          * @return bool|string
2999          */
3000         public function sourceFile(
3001                 $filename, $lineCallback = false, $resultCallback = false, $fname = false
3002         ) {
3003                 wfSuppressWarnings();
3004                 $fp = fopen( $filename, 'r' );
3005                 wfRestoreWarnings();
3006
3007                 if ( false === $fp ) {
3008                         throw new MWException( "Could not open \"{$filename}\".\n" );
3009                 }
3010
3011                 if ( !$fname ) {
3012                         $fname = __METHOD__ . "( $filename )";
3013                 }
3014
3015                 try {
3016                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname );
3017                 }
3018                 catch ( MWException $e ) {
3019                         fclose( $fp );
3020                         throw $e;
3021                 }
3022
3023                 fclose( $fp );
3024
3025                 return $error;
3026         }
3027
3028         /**
3029          * Get the full path of a patch file. Originally based on archive()
3030          * from updaters.inc. Keep in mind this always returns a patch, as
3031          * it fails back to MySQL if no DB-specific patch can be found
3032          *
3033          * @param $patch String The name of the patch, like patch-something.sql
3034          * @return String Full path to patch file
3035          */
3036         public function patchPath( $patch ) {
3037                 global $IP;
3038
3039                 $dbType = $this->getType();
3040                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3041                         return "$IP/maintenance/$dbType/archives/$patch";
3042                 } else {
3043                         return "$IP/maintenance/archives/$patch";
3044                 }
3045         }
3046
3047         /**
3048          * Set variables to be used in sourceFile/sourceStream, in preference to the
3049          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3050          * all. If it's set to false, $GLOBALS will be used.
3051          *
3052          * @param $vars bool|array mapping variable name to value.
3053          */
3054         public function setSchemaVars( $vars ) {
3055                 $this->mSchemaVars = $vars;
3056         }
3057
3058         /**
3059          * Read and execute commands from an open file handle.
3060          *
3061          * Returns true on success, error string or exception on failure (depending
3062          * on object's error ignore settings).
3063          *
3064          * @param $fp Resource: File handle
3065          * @param $lineCallback Callback: Optional function called before reading each line
3066          * @param $resultCallback Callback: Optional function called for each MySQL result
3067          * @param $fname String: Calling function name
3068          * @param $inputCallback Callback: Optional function called for each complete line (ended with ;) sent
3069          * @return bool|string
3070          */
3071         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3072                 $fname = 'DatabaseBase::sourceStream', $inputCallback = false )
3073         {
3074                 $cmd = '';
3075
3076                 while ( !feof( $fp ) ) {
3077                         if ( $lineCallback ) {
3078                                 call_user_func( $lineCallback );
3079                         }
3080
3081                         $line = trim( fgets( $fp ) );
3082
3083                         if ( $line == '' ) {
3084                                 continue;
3085                         }
3086
3087                         if ( '-' == $line[0] && '-' == $line[1] ) {
3088                                 continue;
3089                         }
3090
3091                         if ( $cmd != '' ) {
3092                                 $cmd .= ' ';
3093                         }
3094
3095                         $done = $this->streamStatementEnd( $cmd, $line );
3096
3097                         $cmd .= "$line\n";
3098
3099                         if ( $done || feof( $fp ) ) {
3100                                 $cmd = $this->replaceVars( $cmd );
3101                                 if ( $inputCallback ) {
3102                                         call_user_func( $inputCallback, $cmd );
3103                                 }
3104                                 $res = $this->query( $cmd, $fname );
3105
3106                                 if ( $resultCallback ) {
3107                                         call_user_func( $resultCallback, $res, $this );
3108                                 }
3109
3110                                 if ( false === $res ) {
3111                                         $err = $this->lastError();
3112                                         return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3113                                 }
3114
3115                                 $cmd = '';
3116                         }
3117                 }
3118
3119                 return true;
3120         }
3121
3122         /**
3123          * Called by sourceStream() to check if we've reached a statement end
3124          *
3125          * @param $sql String SQL assembled so far
3126          * @param $newLine String New line about to be added to $sql
3127          * @return Bool Whether $newLine contains end of the statement
3128          */
3129         public function streamStatementEnd( &$sql, &$newLine ) {
3130                 if ( $this->delimiter ) {
3131                         $prev = $newLine;
3132                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3133                         if ( $newLine != $prev ) {
3134                                 return true;
3135                         }
3136                 }
3137                 return false;
3138         }
3139
3140         /**
3141          * Database independent variable replacement. Replaces a set of variables
3142          * in an SQL statement with their contents as given by $this->getSchemaVars().
3143          *
3144          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3145          *
3146          * - '{$var}' should be used for text and is passed through the database's
3147          *   addQuotes method.
3148          * - `{$var}` should be used for identifiers (eg: table and database names),
3149          *   it is passed through the database's addIdentifierQuotes method which
3150          *   can be overridden if the database uses something other than backticks.
3151          * - / *$var* / is just encoded, besides traditional table prefix and
3152          *   table options its use should be avoided.
3153          *
3154          * @param $ins String: SQL statement to replace variables in
3155          * @return String The new SQL statement with variables replaced
3156          */
3157         protected function replaceSchemaVars( $ins ) {
3158                 $vars = $this->getSchemaVars();
3159                 foreach ( $vars as $var => $value ) {
3160                         // replace '{$var}'
3161                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3162                         // replace `{$var}`
3163                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3164                         // replace /*$var*/
3165                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ) , $ins );
3166                 }
3167                 return $ins;
3168         }
3169
3170         /**
3171          * Replace variables in sourced SQL
3172          *
3173          * @param $ins string
3174          *
3175          * @return string
3176          */
3177         protected function replaceVars( $ins ) {
3178                 $ins = $this->replaceSchemaVars( $ins );
3179
3180                 // Table prefixes
3181                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3182                         array( $this, 'tableNameCallback' ), $ins );
3183
3184                 // Index names
3185                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3186                         array( $this, 'indexNameCallback' ), $ins );
3187
3188                 return $ins;
3189         }
3190
3191         /**
3192          * Get schema variables. If none have been set via setSchemaVars(), then
3193          * use some defaults from the current object.
3194          *
3195          * @return array
3196          */
3197         protected function getSchemaVars() {
3198                 if ( $this->mSchemaVars ) {
3199                         return $this->mSchemaVars;
3200                 } else {
3201                         return $this->getDefaultSchemaVars();
3202                 }
3203         }
3204
3205         /**
3206          * Get schema variables to use if none have been set via setSchemaVars().
3207          *
3208          * Override this in derived classes to provide variables for tables.sql
3209          * and SQL patch files.
3210          *
3211          * @return array
3212          */
3213         protected function getDefaultSchemaVars() {
3214                 return array();
3215         }
3216
3217         /**
3218          * Table name callback
3219          *
3220          * @param $matches array
3221          *
3222          * @return string
3223          */
3224         protected function tableNameCallback( $matches ) {
3225                 return $this->tableName( $matches[1] );
3226         }
3227
3228         /**
3229          * Index name callback
3230          *
3231          * @param $matches array
3232          *
3233          * @return string
3234          */
3235         protected function indexNameCallback( $matches ) {
3236                 return $this->indexName( $matches[1] );
3237         }
3238
3239         /**
3240          * Check to see if a named lock is available. This is non-blocking.
3241          *
3242          * @param $lockName String: name of lock to poll
3243          * @param $method String: name of method calling us
3244          * @return Boolean
3245          * @since 1.20
3246          */
3247         public function lockIsFree( $lockName, $method ) {
3248                 return true;
3249         }
3250
3251         /**
3252          * Acquire a named lock
3253          *
3254          * Abstracted from Filestore::lock() so child classes can implement for
3255          * their own needs.
3256          *
3257          * @param $lockName String: name of lock to aquire
3258          * @param $method String: name of method calling us
3259          * @param $timeout Integer: timeout
3260          * @return Boolean
3261          */
3262         public function lock( $lockName, $method, $timeout = 5 ) {
3263                 return true;
3264         }
3265
3266         /**
3267          * Release a lock.
3268          *
3269          * @param $lockName String: Name of lock to release
3270          * @param $method String: Name of method calling us
3271          *
3272          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3273          * by this thread (in which case the lock is not released), and NULL if the named
3274          * lock did not exist
3275          */
3276         public function unlock( $lockName, $method ) {
3277                 return true;
3278         }
3279
3280         /**
3281          * Lock specific tables
3282          *
3283          * @param $read Array of tables to lock for read access
3284          * @param $write Array of tables to lock for write access
3285          * @param $method String name of caller
3286          * @param $lowPriority bool Whether to indicate writes to be LOW PRIORITY
3287          *
3288          * @return bool
3289          */
3290         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3291                 return true;
3292         }
3293
3294         /**
3295          * Unlock specific tables
3296          *
3297          * @param $method String the caller
3298          *
3299          * @return bool
3300          */
3301         public function unlockTables( $method ) {
3302                 return true;
3303         }
3304
3305         /**
3306          * Delete a table
3307          * @param $tableName string
3308          * @param $fName string
3309          * @return bool|ResultWrapper
3310          * @since 1.18
3311          */
3312         public function dropTable( $tableName, $fName = 'DatabaseBase::dropTable' ) {
3313                 if( !$this->tableExists( $tableName, $fName ) ) {
3314                         return false;
3315                 }
3316                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3317                 if( $this->cascadingDeletes() ) {
3318                         $sql .= " CASCADE";
3319                 }
3320                 return $this->query( $sql, $fName );
3321         }
3322
3323         /**
3324          * Get search engine class. All subclasses of this need to implement this
3325          * if they wish to use searching.
3326          *
3327          * @return String
3328          */
3329         public function getSearchEngine() {
3330                 return 'SearchEngineDummy';
3331         }
3332
3333         /**
3334          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3335          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3336          * because "i" sorts after all numbers.
3337          *
3338          * @return String
3339          */
3340         public function getInfinity() {
3341                 return 'infinity';
3342         }
3343
3344         /**
3345          * Encode an expiry time into the DBMS dependent format
3346          *
3347          * @param $expiry String: timestamp for expiry, or the 'infinity' string
3348          * @return String
3349          */
3350         public function encodeExpiry( $expiry ) {
3351                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3352                         ? $this->getInfinity()
3353                         : $this->timestamp( $expiry );
3354         }
3355
3356         /**
3357          * Decode an expiry time into a DBMS independent format
3358          *
3359          * @param $expiry String: DB timestamp field value for expiry
3360          * @param $format integer: TS_* constant, defaults to TS_MW
3361          * @return String
3362          */
3363         public function decodeExpiry( $expiry, $format = TS_MW ) {
3364                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3365                         ? 'infinity'
3366                         : wfTimestamp( $format, $expiry );
3367         }
3368
3369         /**
3370          * Allow or deny "big selects" for this session only. This is done by setting
3371          * the sql_big_selects session variable.
3372          *
3373          * This is a MySQL-specific feature.
3374          *
3375          * @param $value Mixed: true for allow, false for deny, or "default" to
3376          *   restore the initial value
3377          */
3378         public function setBigSelects( $value = true ) {
3379                 // no-op
3380         }
3381
3382         /**
3383          * @since 1.19
3384          */
3385         public function __toString() {
3386                 return (string)$this->mConn;
3387         }
3388 }