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 /**
  28  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  29  * following must be implemented to support MediaWiki
  30  *
  31  * @file
  32  * @ingroup Database
  33  */
  34 interface DatabaseType {
  35         /**
  36          * Get the type of the DBMS, as it appears in $wgDBtype.
  37          *
  38          * @return string
  39          */
  40         function getType();
  41
  42         /**
  43          * Open a connection to the database. Usually aborts on failure
  44          *
  45          * @param string $server database server host
  46          * @param string $user database user name
  47          * @param string $password database user password
  48          * @param string $dbName database name
  49          * @return bool
  50          * @throws DBConnectionError
  51          */
  52         function open( $server, $user, $password, $dbName );
  53
  54         /**
  55          * Fetch the next row from the given result object, in object form.
  56          * Fields can be retrieved with $row->fieldname, with fields acting like
  57          * member variables.
  58          * If no more rows are available, false is returned.
  59          *
  60          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  61          * @return object|bool
  62          * @throws DBUnexpectedError Thrown if the database returns an error
  63          */
  64         function fetchObject( $res );
  65
  66         /**
  67          * Fetch the next row from the given result object, in associative array
  68          * form.  Fields are retrieved with $row['fieldname'].
  69          * If no more rows are available, false is returned.
  70          *
  71          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  72          * @return array|bool
  73          * @throws DBUnexpectedError Thrown if the database returns an error
  74          */
  75         function fetchRow( $res );
  76
  77         /**
  78          * Get the number of rows in a result object
  79          *
  80          * @param $res Mixed: A SQL result
  81          * @return int
  82          */
  83         function numRows( $res );
  84
  85         /**
  86          * Get the number of fields in a result object
  87          * @see http://www.php.net/mysql_num_fields
  88          *
  89          * @param $res Mixed: A SQL result
  90          * @return int
  91          */
  92         function numFields( $res );
  93
  94         /**
  95          * Get a field name in a result object
  96          * @see http://www.php.net/mysql_field_name
  97          *
  98          * @param $res Mixed: A SQL result
  99          * @param $n Integer
 100          * @return string
 101          */
 102         function fieldName( $res, $n );
 103
 104         /**
 105          * Get the inserted value of an auto-increment row
 106          *
 107          * The value inserted should be fetched from nextSequenceValue()
 108          *
 109          * Example:
 110          * $id = $dbw->nextSequenceValue( 'page_page_id_seq' );
 111          * $dbw->insert( 'page', array( 'page_id' => $id ) );
 112          * $id = $dbw->insertId();
 113          *
 114          * @return int
 115          */
 116         function insertId();
 117
 118         /**
 119          * Change the position of the cursor in a result object
 120          * @see http://www.php.net/mysql_data_seek
 121          *
 122          * @param $res Mixed: A SQL result
 123          * @param $row Mixed: Either MySQL row or ResultWrapper
 124          */
 125         function dataSeek( $res, $row );
 126
 127         /**
 128          * Get the last error number
 129          * @see http://www.php.net/mysql_errno
 130          *
 131          * @return int
 132          */
 133         function lastErrno();
 134
 135         /**
 136          * Get a description of the last error
 137          * @see http://www.php.net/mysql_error
 138          *
 139          * @return string
 140          */
 141         function lastError();
 142
 143         /**
 144          * mysql_fetch_field() wrapper
 145          * Returns false if the field doesn't exist
 146          *
 147          * @param string $table table name
 148          * @param string $field field name
 149          *
 150          * @return Field
 151          */
 152         function fieldInfo( $table, $field );
 153
 154         /**
 155          * Get information about an index into an object
 156          * @param string $table Table name
 157          * @param string $index Index name
 158          * @param string $fname Calling function name
 159          * @return Mixed: Database-specific index description class or false if the index does not exist
 160          */
 161         function indexInfo( $table, $index, $fname = __METHOD__ );
 162
 163         /**
 164          * Get the number of rows affected by the last write query
 165          * @see http://www.php.net/mysql_affected_rows
 166          *
 167          * @return int
 168          */
 169         function affectedRows();
 170
 171         /**
 172          * Wrapper for addslashes()
 173          *
 174          * @param string $s to be slashed.
 175          * @return string: slashed string.
 176          */
 177         function strencode( $s );
 178
 179         /**
 180          * Returns a wikitext link to the DB's website, e.g.,
 181          *     return "[http://www.mysql.com/ MySQL]";
 182          * Should at least contain plain text, if for some reason
 183          * your database has no website.
 184          *
 185          * @return string: wikitext of a link to the server software's web site
 186          */
 187         function getSoftwareLink();
 188
 189         /**
 190          * A string describing the current software version, like from
 191          * mysql_get_server_info().
 192          *
 193          * @return string: Version information from the database server.
 194          */
 195         function getServerVersion();
 196
 197         /**
 198          * A string describing the current software version, and possibly
 199          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 200          * Use getServerVersion() to get machine-friendly information.
 201          *
 202          * @return string: Version information from the database server
 203          */
 204         function getServerInfo();
 205 }
 206
 207 /**
 208  * Interface for classes that implement or wrap DatabaseBase
 209  * @ingroup Database
 210  */
 211 interface IDatabase {
 212 }
 213
 214 /**
 215  * Database abstraction object
 216  * @ingroup Database
 217  */
 218 abstract class DatabaseBase implements IDatabase, DatabaseType {
 219         /** Number of times to re-try an operation in case of deadlock */
 220         const DEADLOCK_TRIES = 4;
 221         /** Minimum time to wait before retry, in microseconds */
 222         const DEADLOCK_DELAY_MIN = 500000;
 223         /** Maximum time to wait before retry */
 224         const DEADLOCK_DELAY_MAX = 1500000;
 225
 226 # ------------------------------------------------------------------------------
 227 # Variables
 228 # ------------------------------------------------------------------------------
 229
 230         protected $mLastQuery = '';
 231         protected $mDoneWrites = false;
 232         protected $mPHPError = false;
 233
 234         protected $mServer, $mUser, $mPassword, $mDBname;
 235
 236         protected $mConn = null;
 237         protected $mOpened = false;
 238
 239         /** @var callable[] */
 240         protected $mTrxIdleCallbacks = array();
 241         /** @var callable[] */
 242         protected $mTrxPreCommitCallbacks = array();
 243
 244         protected $mTablePrefix;
 245         protected $mFlags;
 246         protected $mForeign;
 247         protected $mErrorCount = 0;
 248         protected $mLBInfo = array();
 249         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 250         protected $mDefaultBigSelects = null;
 251         protected $mSchemaVars = false;
 252
 253         protected $preparedArgs;
 254
 255         protected $htmlErrors;
 256
 257         protected $delimiter = ';';
 258
 259         /**
 260          * Either 1 if a transaction is active or 0 otherwise.
 261          * The other Trx fields may not be meaningfull if this is 0.
 262          *
 263          * @var int
 264          */
 265         protected $mTrxLevel = 0;
 266
 267         /**
 268          * Remembers the function name given for starting the most recent transaction via begin().
 269          * Used to provide additional context for error reporting.
 270          *
 271          * @var String
 272          * @see DatabaseBase::mTrxLevel
 273          */
 274         private $mTrxFname = null;
 275
 276         /**
 277          * Record if possible write queries were done in the last transaction started
 278          *
 279          * @var Bool
 280          * @see DatabaseBase::mTrxLevel
 281          */
 282         private $mTrxDoneWrites = false;
 283
 284         /**
 285          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 286          *
 287          * @var Bool
 288          * @see DatabaseBase::mTrxLevel
 289          */
 290         private $mTrxAutomatic = false;
 291
 292         /**
 293          * Array of levels of atomicity within transactions
 294          *
 295          * @var SplStack
 296          */
 297         private $mTrxAtomicLevels;
 298
 299         /**
 300          * Record if the current transaction was started implicitly by DatabaseBase::startAtomic
 301          *
 302          * @var Bool
 303          */
 304         private $mTrxAutomaticAtomic = false;
 305
 306         /**
 307          * @since 1.21
 308          * @var file handle for upgrade
 309          */
 310         protected $fileHandle = null;
 311
 312         /**
 313          * @since 1.22
 314          * @var Process cache of VIEWs names in the database
 315          */
 316         protected $allViews = null;
 317
 318 # ------------------------------------------------------------------------------
 319 # Accessors
 320 # ------------------------------------------------------------------------------
 321         # These optionally set a variable and return the previous state
 322
 323         /**
 324          * A string describing the current software version, and possibly
 325          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 326          * Use getServerVersion() to get machine-friendly information.
 327          *
 328          * @return string: Version information from the database server
 329          */
 330         public function getServerInfo() {
 331                 return $this->getServerVersion();
 332         }
 333
 334         /**
 335          * @return string: command delimiter used by this database engine
 336          */
 337         public function getDelimiter() {
 338                 return $this->delimiter;
 339         }
 340
 341         /**
 342          * Boolean, controls output of large amounts of debug information.
 343          * @param $debug bool|null
 344          *   - true to enable debugging
 345          *   - false to disable debugging
 346          *   - omitted or null to do nothing
 347          *
 348          * @return bool|null previous value of the flag
 349          */
 350         public function debug( $debug = null ) {
 351                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 352         }
 353
 354         /**
 355          * Turns buffering of SQL result sets on (true) or off (false). Default is
 356          * "on".
 357          *
 358          * Unbuffered queries are very troublesome in MySQL:
 359          *
 360          *   - If another query is executed while the first query is being read
 361          *     out, the first query is killed. This means you can't call normal
 362          *     MediaWiki functions while you are reading an unbuffered query result
 363          *     from a normal wfGetDB() connection.
 364          *
 365          *   - Unbuffered queries cause the MySQL server to use large amounts of
 366          *     memory and to hold broad locks which block other queries.
 367          *
 368          * If you want to limit client-side memory, it's almost always better to
 369          * split up queries into batches using a LIMIT clause than to switch off
 370          * buffering.
 371          *
 372          * @param $buffer null|bool
 373          *
 374          * @return null|bool The previous value of the flag
 375          */
 376         public function bufferResults( $buffer = null ) {
 377                 if ( is_null( $buffer ) ) {
 378                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 379                 } else {
 380                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 381                 }
 382         }
 383
 384         /**
 385          * Turns on (false) or off (true) the automatic generation and sending
 386          * of a "we're sorry, but there has been a database error" page on
 387          * database errors. Default is on (false). When turned off, the
 388          * code should use lastErrno() and lastError() to handle the
 389          * situation as appropriate.
 390          *
 391          * Do not use this function outside of the Database classes.
 392          *
 393          * @param $ignoreErrors bool|null
 394          *
 395          * @return bool The previous value of the flag.
 396          */
 397         public function ignoreErrors( $ignoreErrors = null ) {
 398                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 399         }
 400
 401         /**
 402          * Gets the current transaction level.
 403          *
 404          * Historically, transactions were allowed to be "nested". This is no
 405          * longer supported, so this function really only returns a boolean.
 406          *
 407          * @return int The previous value
 408          */
 409         public function trxLevel() {
 410                 return $this->mTrxLevel;
 411         }
 412
 413         /**
 414          * Get/set the number of errors logged. Only useful when errors are ignored
 415          * @param int $count The count to set, or omitted to leave it unchanged.
 416          * @return int The error count
 417          */
 418         public function errorCount( $count = null ) {
 419                 return wfSetVar( $this->mErrorCount, $count );
 420         }
 421
 422         /**
 423          * Get/set the table prefix.
 424          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 425          * @return string The previous table prefix.
 426          */
 427         public function tablePrefix( $prefix = null ) {
 428                 return wfSetVar( $this->mTablePrefix, $prefix );
 429         }
 430
 431         /**
 432          * Set the filehandle to copy write statements to.
 433          *
 434          * @param $fh filehandle
 435          */
 436         public function setFileHandle( $fh ) {
 437                 $this->fileHandle = $fh;
 438         }
 439
 440         /**
 441          * Get properties passed down from the server info array of the load
 442          * balancer.
 443          *
 444          * @param string $name The entry of the info array to get, or null to get the
 445          *   whole array
 446          *
 447          * @return LoadBalancer|null
 448          */
 449         public function getLBInfo( $name = null ) {
 450                 if ( is_null( $name ) ) {
 451                         return $this->mLBInfo;
 452                 } else {
 453                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 454                                 return $this->mLBInfo[$name];
 455                         } else {
 456                                 return null;
 457                         }
 458                 }
 459         }
 460
 461         /**
 462          * Set the LB info array, or a member of it. If called with one parameter,
 463          * the LB info array is set to that parameter. If it is called with two
 464          * parameters, the member with the given name is set to the given value.
 465          *
 466          * @param $name
 467          * @param $value
 468          */
 469         public function setLBInfo( $name, $value = null ) {
 470                 if ( is_null( $value ) ) {
 471                         $this->mLBInfo = $name;
 472                 } else {
 473                         $this->mLBInfo[$name] = $value;
 474                 }
 475         }
 476
 477         /**
 478          * Set lag time in seconds for a fake slave
 479          *
 480          * @param $lag int
 481          */
 482         public function setFakeSlaveLag( $lag ) {
 483                 $this->mFakeSlaveLag = $lag;
 484         }
 485
 486         /**
 487          * Make this connection a fake master
 488          *
 489          * @param $enabled bool
 490          */
 491         public function setFakeMaster( $enabled = true ) {
 492                 $this->mFakeMaster = $enabled;
 493         }
 494
 495         /**
 496          * Returns true if this database supports (and uses) cascading deletes
 497          *
 498          * @return bool
 499          */
 500         public function cascadingDeletes() {
 501                 return false;
 502         }
 503
 504         /**
 505          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 506          *
 507          * @return bool
 508          */
 509         public function cleanupTriggers() {
 510                 return false;
 511         }
 512
 513         /**
 514          * Returns true if this database is strict about what can be put into an IP field.
 515          * Specifically, it uses a NULL value instead of an empty string.
 516          *
 517          * @return bool
 518          */
 519         public function strictIPs() {
 520                 return false;
 521         }
 522
 523         /**
 524          * Returns true if this database uses timestamps rather than integers
 525          *
 526          * @return bool
 527          */
 528         public function realTimestamps() {
 529                 return false;
 530         }
 531
 532         /**
 533          * Returns true if this database does an implicit sort when doing GROUP BY
 534          *
 535          * @return bool
 536          */
 537         public function implicitGroupby() {
 538                 return true;
 539         }
 540
 541         /**
 542          * Returns true if this database does an implicit order by when the column has an index
 543          * For example: SELECT page_title FROM page LIMIT 1
 544          *
 545          * @return bool
 546          */
 547         public function implicitOrderby() {
 548                 return true;
 549         }
 550
 551         /**
 552          * Returns true if this database can do a native search on IP columns
 553          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 554          *
 555          * @return bool
 556          */
 557         public function searchableIPs() {
 558                 return false;
 559         }
 560
 561         /**
 562          * Returns true if this database can use functional indexes
 563          *
 564          * @return bool
 565          */
 566         public function functionalIndexes() {
 567                 return false;
 568         }
 569
 570         /**
 571          * Return the last query that went through DatabaseBase::query()
 572          * @return String
 573          */
 574         public function lastQuery() {
 575                 return $this->mLastQuery;
 576         }
 577
 578         /**
 579          * Returns true if the connection may have been used for write queries.
 580          * Should return true if unsure.
 581          *
 582          * @return bool
 583          */
 584         public function doneWrites() {
 585                 return $this->mDoneWrites;
 586         }
 587
 588         /**
 589          * Returns true if there is a transaction open with possible write
 590          * queries or transaction pre-commit/idle callbacks waiting on it to finish.
 591          *
 592          * @return bool
 593          */
 594         public function writesOrCallbacksPending() {
 595                 return $this->mTrxLevel && (
 596                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 597                 );
 598         }
 599
 600         /**
 601          * Is a connection to the database open?
 602          * @return Boolean
 603          */
 604         public function isOpen() {
 605                 return $this->mOpened;
 606         }
 607
 608         /**
 609          * Set a flag for this connection
 610          *
 611          * @param $flag Integer: DBO_* constants from Defines.php:
 612          *   - DBO_DEBUG: output some debug info (same as debug())
 613          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 614          *   - DBO_TRX: automatically start transactions
 615          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 616          *       and removes it in command line mode
 617          *   - DBO_PERSISTENT: use persistant database connection
 618          */
 619         public function setFlag( $flag ) {
 620                 global $wgDebugDBTransactions;
 621                 $this->mFlags |= $flag;
 622                 if ( ( $flag & DBO_TRX ) & $wgDebugDBTransactions ) {
 623                         wfDebug( "Implicit transactions are now  disabled.\n" );
 624                 }
 625         }
 626
 627         /**
 628          * Clear a flag for this connection
 629          *
 630          * @param $flag : same as setFlag()'s $flag param
 631          */
 632         public function clearFlag( $flag ) {
 633                 global $wgDebugDBTransactions;
 634                 $this->mFlags &= ~$flag;
 635                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 636                         wfDebug( "Implicit transactions are now disabled.\n" );
 637                 }
 638         }
 639
 640         /**
 641          * Returns a boolean whether the flag $flag is set for this connection
 642          *
 643          * @param $flag : same as setFlag()'s $flag param
 644          * @return Boolean
 645          */
 646         public function getFlag( $flag ) {
 647                 return !!( $this->mFlags & $flag );
 648         }
 649
 650         /**
 651          * General read-only accessor
 652          *
 653          * @param $name string
 654          *
 655          * @return string
 656          */
 657         public function getProperty( $name ) {
 658                 return $this->$name;
 659         }
 660
 661         /**
 662          * @return string
 663          */
 664         public function getWikiID() {
 665                 if ( $this->mTablePrefix ) {
 666                         return "{$this->mDBname}-{$this->mTablePrefix}";
 667                 } else {
 668                         return $this->mDBname;
 669                 }
 670         }
 671
 672         /**
 673          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 674          *
 675          * @return string
 676          */
 677         public function getSchemaPath() {
 678                 global $IP;
 679                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 680                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 681                 } else {
 682                         return "$IP/maintenance/tables.sql";
 683                 }
 684         }
 685
 686 # ------------------------------------------------------------------------------
 687 # Other functions
 688 # ------------------------------------------------------------------------------
 689
 690         /**
 691          * Constructor.
 692          *
 693          * FIXME: It is possible to construct a Database object with no associated
 694          * connection object, by specifying no parameters to __construct(). This
 695          * feature is deprecated and should be removed.
 696          *
 697          * DatabaseBase subclasses should not be constructed directly in external
 698          * code. DatabaseBase::factory() should be used instead.
 699          *
 700          * @param array Parameters passed from DatabaseBase::factory()
 701          */
 702         function __construct( $params = null ) {
 703                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 704
 705                 $this->mTrxAtomicLevels = new SplStack;
 706
 707                 if ( is_array( $params ) ) { // MW 1.22
 708                         $server = $params['host'];
 709                         $user = $params['user'];
 710                         $password = $params['password'];
 711                         $dbName = $params['dbname'];
 712                         $flags = $params['flags'];
 713                         $tablePrefix = $params['tablePrefix'];
 714                         $foreign = $params['foreign'];
 715                 } else { // legacy calling pattern
 716                         wfDeprecated( __METHOD__ . " method called without parameter array.", "1.23" );
 717                         $args = func_get_args();
 718                         $server = isset( $args[0] ) ? $args[0] : false;
 719                         $user = isset( $args[1] ) ? $args[1] : false;
 720                         $password = isset( $args[2] ) ? $args[2] : false;
 721                         $dbName = isset( $args[3] ) ? $args[3] : false;
 722                         $flags = isset( $args[4] ) ? $args[4] : 0;
 723                         $tablePrefix = isset( $args[5] ) ? $args[5] : 'get from global';
 724                         $foreign = isset( $args[6] ) ? $args[6] : false;
 725                 }
 726
 727                 $this->mFlags = $flags;
 728                 if ( $this->mFlags & DBO_DEFAULT ) {
 729                         if ( $wgCommandLineMode ) {
 730                                 $this->mFlags &= ~DBO_TRX;
 731                                 if ( $wgDebugDBTransactions ) {
 732                                         wfDebug( "Implicit transaction open disabled.\n" );
 733                                 }
 734                         } else {
 735                                 $this->mFlags |= DBO_TRX;
 736                                 if ( $wgDebugDBTransactions ) {
 737                                         wfDebug( "Implicit transaction open enabled.\n" );
 738                                 }
 739                         }
 740                 }
 741
 742                 /** Get the default table prefix*/
 743                 if ( $tablePrefix == 'get from global' ) {
 744                         $this->mTablePrefix = $wgDBprefix;
 745                 } else {
 746                         $this->mTablePrefix = $tablePrefix;
 747                 }
 748
 749                 $this->mForeign = $foreign;
 750
 751                 if ( $user ) {
 752                         $this->open( $server, $user, $password, $dbName );
 753                 }
 754         }
 755
 756         /**
 757          * Called by serialize. Throw an exception when DB connection is serialized.
 758          * This causes problems on some database engines because the connection is
 759          * not restored on unserialize.
 760          */
 761         public function __sleep() {
 762                 throw new MWException( 'Database serialization may cause problems, since ' .
 763                         'the connection is not restored on wakeup.' );
 764         }
 765
 766         /**
 767          * Given a DB type, construct the name of the appropriate child class of
 768          * DatabaseBase. This is designed to replace all of the manual stuff like:
 769          *    $class = 'Database' . ucfirst( strtolower( $dbType ) );
 770          * as well as validate against the canonical list of DB types we have
 771          *
 772          * This factory function is mostly useful for when you need to connect to a
 773          * database other than the MediaWiki default (such as for external auth,
 774          * an extension, et cetera). Do not use this to connect to the MediaWiki
 775          * database. Example uses in core:
 776          * @see LoadBalancer::reallyOpenConnection()
 777          * @see ForeignDBRepo::getMasterDB()
 778          * @see WebInstaller_DBConnect::execute()
 779          *
 780          * @since 1.18
 781          *
 782          * @param string $dbType A possible DB type
 783          * @param array $p An array of options to pass to the constructor.
 784          *    Valid options are: host, user, password, dbname, flags, tablePrefix, driver
 785          * @return DatabaseBase subclass or null
 786          */
 787         final public static function factory( $dbType, $p = array() ) {
 788                 $canonicalDBTypes = array(
 789                         'mysql' => array( 'mysqli', 'mysql' ),
 790                         'postgres' => array(),
 791                         'sqlite' => array(),
 792                         'oracle' => array(),
 793                         'mssql' => array(),
 794                 );
 795
 796                 $driver = false;
 797                 $dbType = strtolower( $dbType );
 798                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 799                         $possibleDrivers = $canonicalDBTypes[$dbType];
 800                         if ( !empty( $p['driver'] ) ) {
 801                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 802                                         $driver = $p['driver'];
 803                                 } else {
 804                                         throw new MWException( __METHOD__ .
 805                                                 " cannot construct Database with type '$dbType' and driver '{$p['driver']}'" );
 806                                 }
 807                         } else {
 808                                 foreach ( $possibleDrivers as $posDriver ) {
 809                                         if ( extension_loaded( $posDriver ) ) {
 810                                                 $driver = $posDriver;
 811                                                 break;
 812                                         }
 813                                 }
 814                         }
 815                 } else {
 816                         $driver = $dbType;
 817                 }
 818                 if ( $driver === false ) {
 819                         throw new MWException( __METHOD__ .
 820                                 " no viable database extension found for type '$dbType'" );
 821                 }
 822
 823                 $class = 'Database' . ucfirst( $driver );
 824                 if ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 825                         $params = array(
 826                                 'host' => isset( $p['host'] ) ? $p['host'] : false,
 827                                 'user' => isset( $p['user'] ) ? $p['user'] : false,
 828                                 'password' => isset( $p['password'] ) ? $p['password'] : false,
 829                                 'dbname' => isset( $p['dbname'] ) ? $p['dbname'] : false,
 830                                 'flags' => isset( $p['flags'] ) ? $p['flags'] : 0,
 831                                 'tablePrefix' => isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global',
 832                                 'foreign' => isset( $p['foreign'] ) ? $p['foreign'] : false
 833                         );
 834
 835                         return new $class( $params );
 836                 } else {
 837                         return null;
 838                 }
 839         }
 840
 841         protected function installErrorHandler() {
 842                 $this->mPHPError = false;
 843                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 844                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 845         }
 846
 847         /**
 848          * @return bool|string
 849          */
 850         protected function restoreErrorHandler() {
 851                 restore_error_handler();
 852                 if ( $this->htmlErrors !== false ) {
 853                         ini_set( 'html_errors', $this->htmlErrors );
 854                 }
 855                 if ( $this->mPHPError ) {
 856                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 857                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 858
 859                         return $error;
 860                 } else {
 861                         return false;
 862                 }
 863         }
 864
 865         /**
 866          * @param $errno
 867          * @param $errstr
 868          * @access private
 869          */
 870         public function connectionErrorHandler( $errno, $errstr ) {
 871                 $this->mPHPError = $errstr;
 872         }
 873
 874         /**
 875          * Closes a database connection.
 876          * if it is open : commits any open transactions
 877          *
 878          * @throws MWException
 879          * @return Bool operation success. true if already closed.
 880          */
 881         public function close() {
 882                 if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
 883                         throw new MWException( "Transaction idle callbacks still pending." );
 884                 }
 885                 $this->mOpened = false;
 886                 if ( $this->mConn ) {
 887                         if ( $this->trxLevel() ) {
 888                                 if ( !$this->mTrxAutomatic ) {
 889                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 890                                                 " performing implicit commit before closing connection!" );
 891                                 }
 892
 893                                 $this->commit( __METHOD__, 'flush' );
 894                         }
 895
 896                         $ret = $this->closeConnection();
 897                         $this->mConn = false;
 898
 899                         return $ret;
 900                 } else {
 901                         return true;
 902                 }
 903         }
 904
 905         /**
 906          * Closes underlying database connection
 907          * @since 1.20
 908          * @return bool: Whether connection was closed successfully
 909          */
 910         abstract protected function closeConnection();
 911
 912         /**
 913          * @param string $error fallback error message, used if none is given by DB
 914          * @throws DBConnectionError
 915          */
 916         function reportConnectionError( $error = 'Unknown error' ) {
 917                 $myError = $this->lastError();
 918                 if ( $myError ) {
 919                         $error = $myError;
 920                 }
 921
 922                 # New method
 923                 throw new DBConnectionError( $this, $error );
 924         }
 925
 926         /**
 927          * The DBMS-dependent part of query()
 928          *
 929          * @param  $sql String: SQL query.
 930          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 931          */
 932         abstract protected function doQuery( $sql );
 933
 934         /**
 935          * Determine whether a query writes to the DB.
 936          * Should return true if unsure.
 937          *
 938          * @param $sql string
 939          *
 940          * @return bool
 941          */
 942         public function isWriteQuery( $sql ) {
 943                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 944         }
 945
 946         /**
 947          * Run an SQL query and return the result. Normally throws a DBQueryError
 948          * on failure. If errors are ignored, returns false instead.
 949          *
 950          * In new code, the query wrappers select(), insert(), update(), delete(),
 951          * etc. should be used where possible, since they give much better DBMS
 952          * independence and automatically quote or validate user input in a variety
 953          * of contexts. This function is generally only useful for queries which are
 954          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 955          * as CREATE TABLE.
 956          *
 957          * However, the query wrappers themselves should call this function.
 958          *
 959          * @param  $sql        String: SQL query
 960          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 961          *     comment (you can use __METHOD__ or add some extra info)
 962          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 963          *     maybe best to catch the exception instead?
 964          * @throws MWException
 965          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 966          *     for a successful read query, or false on failure if $tempIgnore set
 967          */
 968         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 969                 global $wgUser, $wgDebugDBTransactions;
 970
 971                 $this->mLastQuery = $sql;
 972                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 973                         # Set a flag indicating that writes have been done
 974                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 975                         $this->mDoneWrites = true;
 976                 }
 977
 978                 # Add a comment for easy SHOW PROCESSLIST interpretation
 979                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 980                         $userName = $wgUser->getName();
 981                         if ( mb_strlen( $userName ) > 15 ) {
 982                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 983                         }
 984                         $userName = str_replace( '/', '', $userName );
 985                 } else {
 986                         $userName = '';
 987                 }
 988
 989                 // Add trace comment to the begin of the sql string, right after the operator.
 990                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 991                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 992
 993                 # If DBO_TRX is set, start a transaction
 994                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 995                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK'
 996                 ) {
 997                         # Avoid establishing transactions for SHOW and SET statements too -
 998                         # that would delay transaction initializations to once connection
 999                         # is really used by application
1000                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
1001                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
1002                                 if ( $wgDebugDBTransactions ) {
1003                                         wfDebug( "Implicit transaction start.\n" );
1004                                 }
1005                                 $this->begin( __METHOD__ . " ($fname)" );
1006                                 $this->mTrxAutomatic = true;
1007                         }
1008                 }
1009
1010                 # Keep track of whether the transaction has write queries pending
1011                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
1012                         $this->mTrxDoneWrites = true;
1013                         Profiler::instance()->transactionWritingIn( $this->mServer, $this->mDBname );
1014                 }
1015
1016                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1017                 if ( !Profiler::instance()->isStub() ) {
1018                         # generalizeSQL will probably cut down the query to reasonable
1019                         # logging size most of the time. The substr is really just a sanity check.
1020                         if ( $isMaster ) {
1021                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
1022                                 $totalProf = 'DatabaseBase::query-master';
1023                         } else {
1024                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
1025                                 $totalProf = 'DatabaseBase::query';
1026                         }
1027                         wfProfileIn( $totalProf );
1028                         wfProfileIn( $queryProf );
1029                 }
1030
1031                 if ( $this->debug() ) {
1032                         static $cnt = 0;
1033
1034                         $cnt++;
1035                         $sqlx = substr( $commentedSql, 0, 500 );
1036                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
1037
1038                         $master = $isMaster ? 'master' : 'slave';
1039                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
1040                 }
1041
1042                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
1043
1044                 # Do the query and handle errors
1045                 $ret = $this->doQuery( $commentedSql );
1046
1047                 MWDebug::queryTime( $queryId );
1048
1049                 # Try reconnecting if the connection was lost
1050                 if ( false === $ret && $this->wasErrorReissuable() ) {
1051                         # Transaction is gone, like it or not
1052                         $hadTrx = $this->mTrxLevel; // possible lost transaction
1053                         wfDebug( "Connection lost, reconnecting...\n" );
1054                         $this->mTrxLevel = 0;
1055                         wfDebug( "Connection lost, reconnecting...\n" );
1056
1057                         if ( $this->ping() ) {
1058                                 wfDebug( "Reconnected\n" );
1059                                 $sqlx = substr( $commentedSql, 0, 500 );
1060                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
1061                                 global $wgRequestTime;
1062                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
1063                                 if ( $elapsed < 300 ) {
1064                                         # Not a database error to lose a transaction after a minute or two
1065                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
1066                                 }
1067                                 if ( !$hadTrx ) {
1068                                         # Should be safe to silently retry
1069                                         $ret = $this->doQuery( $commentedSql );
1070                                 }
1071                         } else {
1072                                 wfDebug( "Failed\n" );
1073                         }
1074                 }
1075
1076                 if ( false === $ret ) {
1077                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
1078                 }
1079
1080                 if ( !Profiler::instance()->isStub() ) {
1081                         wfProfileOut( $queryProf );
1082                         wfProfileOut( $totalProf );
1083                 }
1084
1085                 return $this->resultObject( $ret );
1086         }
1087
1088         /**
1089          * Report a query error. Log the error, and if neither the object ignore
1090          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1091          *
1092          * @param $error String
1093          * @param $errno Integer
1094          * @param $sql String
1095          * @param $fname String
1096          * @param $tempIgnore Boolean
1097          * @throws DBQueryError
1098          */
1099         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1100                 # Ignore errors during error handling to avoid infinite recursion
1101                 $ignore = $this->ignoreErrors( true );
1102                 ++$this->mErrorCount;
1103
1104                 if ( $ignore || $tempIgnore ) {
1105                         wfDebug( "SQL ERROR (ignored): $error\n" );
1106                         $this->ignoreErrors( $ignore );
1107                 } else {
1108                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1109                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
1110                         wfDebug( "SQL ERROR: " . $error . "\n" );
1111                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1112                 }
1113         }
1114
1115         /**
1116          * Intended to be compatible with the PEAR::DB wrapper functions.
1117          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1118          *
1119          * ? = scalar value, quoted as necessary
1120          * ! = raw SQL bit (a function for instance)
1121          * & = filename; reads the file and inserts as a blob
1122          *     (we don't use this though...)
1123          *
1124          * @param $sql string
1125          * @param $func string
1126          *
1127          * @return array
1128          */
1129         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1130                 /* MySQL doesn't support prepared statements (yet), so just
1131                    pack up the query for reference. We'll manually replace
1132                    the bits later. */
1133                 return array( 'query' => $sql, 'func' => $func );
1134         }
1135
1136         /**
1137          * Free a prepared query, generated by prepare().
1138          * @param $prepared
1139          */
1140         protected function freePrepared( $prepared ) {
1141                 /* No-op by default */
1142         }
1143
1144         /**
1145          * Execute a prepared query with the various arguments
1146          * @param string $prepared the prepared sql
1147          * @param $args Mixed: Either an array here, or put scalars as varargs
1148          *
1149          * @return ResultWrapper
1150          */
1151         public function execute( $prepared, $args = null ) {
1152                 if ( !is_array( $args ) ) {
1153                         # Pull the var args
1154                         $args = func_get_args();
1155                         array_shift( $args );
1156                 }
1157
1158                 $sql = $this->fillPrepared( $prepared['query'], $args );
1159
1160                 return $this->query( $sql, $prepared['func'] );
1161         }
1162
1163         /**
1164          * For faking prepared SQL statements on DBs that don't support it directly.
1165          *
1166          * @param string $preparedQuery a 'preparable' SQL statement
1167          * @param array $args of arguments to fill it with
1168          * @return string executable SQL
1169          */
1170         public function fillPrepared( $preparedQuery, $args ) {
1171                 reset( $args );
1172                 $this->preparedArgs =& $args;
1173
1174                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1175                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1176         }
1177
1178         /**
1179          * preg_callback func for fillPrepared()
1180          * The arguments should be in $this->preparedArgs and must not be touched
1181          * while we're doing this.
1182          *
1183          * @param $matches Array
1184          * @throws DBUnexpectedError
1185          * @return String
1186          */
1187         protected function fillPreparedArg( $matches ) {
1188                 switch ( $matches[1] ) {
1189                         case '\\?':
1190                                 return '?';
1191                         case '\\!':
1192                                 return '!';
1193                         case '\\&':
1194                                 return '&';
1195                 }
1196
1197                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1198
1199                 switch ( $matches[1] ) {
1200                         case '?':
1201                                 return $this->addQuotes( $arg );
1202                         case '!':
1203                                 return $arg;
1204                         case '&':
1205                                 # return $this->addQuotes( file_get_contents( $arg ) );
1206                                 throw new DBUnexpectedError(
1207                                         $this,
1208                                         '& mode is not implemented. If it\'s really needed, uncomment the line above.'
1209                                 );
1210                         default:
1211                                 throw new DBUnexpectedError(
1212                                         $this,
1213                                         'Received invalid match. This should never happen!'
1214                                 );
1215                 }
1216         }
1217
1218         /**
1219          * Free a result object returned by query() or select(). It's usually not
1220          * necessary to call this, just use unset() or let the variable holding
1221          * the result object go out of scope.
1222          *
1223          * @param $res Mixed: A SQL result
1224          */
1225         public function freeResult( $res ) {
1226         }
1227
1228         /**
1229          * A SELECT wrapper which returns a single field from a single result row.
1230          *
1231          * Usually throws a DBQueryError on failure. If errors are explicitly
1232          * ignored, returns false on failure.
1233          *
1234          * If no result rows are returned from the query, false is returned.
1235          *
1236          * @param string|array $table Table name. See DatabaseBase::select() for details.
1237          * @param string $var The field name to select. This must be a valid SQL
1238          *   fragment: do not use unvalidated user input.
1239          * @param string|array $cond The condition array. See DatabaseBase::select() for details.
1240          * @param string $fname The function name of the caller.
1241          * @param string|array $options The query options. See DatabaseBase::select() for details.
1242          *
1243          * @return bool|mixed The value from the field, or false on failure.
1244          */
1245         public function selectField( $table, $var, $cond = '', $fname = __METHOD__,
1246                 $options = array()
1247         ) {
1248                 if ( !is_array( $options ) ) {
1249                         $options = array( $options );
1250                 }
1251
1252                 $options['LIMIT'] = 1;
1253
1254                 $res = $this->select( $table, $var, $cond, $fname, $options );
1255
1256                 if ( $res === false || !$this->numRows( $res ) ) {
1257                         return false;
1258                 }
1259
1260                 $row = $this->fetchRow( $res );
1261
1262                 if ( $row !== false ) {
1263                         return reset( $row );
1264                 } else {
1265                         return false;
1266                 }
1267         }
1268
1269         /**
1270          * Returns an optional USE INDEX clause to go after the table, and a
1271          * string to go at the end of the query.
1272          *
1273          * @param array $options associative array of options to be turned into
1274          *              an SQL query, valid keys are listed in the function.
1275          * @return Array
1276          * @see DatabaseBase::select()
1277          */
1278         public function makeSelectOptions( $options ) {
1279                 $preLimitTail = $postLimitTail = '';
1280                 $startOpts = '';
1281
1282                 $noKeyOptions = array();
1283
1284                 foreach ( $options as $key => $option ) {
1285                         if ( is_numeric( $key ) ) {
1286                                 $noKeyOptions[$option] = true;
1287                         }
1288                 }
1289
1290                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1291
1292                 $preLimitTail .= $this->makeOrderBy( $options );
1293
1294                 // if (isset($options['LIMIT'])) {
1295                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1296                 //              isset($options['OFFSET']) ? $options['OFFSET']
1297                 //              : false);
1298                 // }
1299
1300                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1301                         $postLimitTail .= ' FOR UPDATE';
1302                 }
1303
1304                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1305                         $postLimitTail .= ' LOCK IN SHARE MODE';
1306                 }
1307
1308                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1309                         $startOpts .= 'DISTINCT';
1310                 }
1311
1312                 # Various MySQL extensions
1313                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1314                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1315                 }
1316
1317                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1318                         $startOpts .= ' HIGH_PRIORITY';
1319                 }
1320
1321                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1322                         $startOpts .= ' SQL_BIG_RESULT';
1323                 }
1324
1325                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1326                         $startOpts .= ' SQL_BUFFER_RESULT';
1327                 }
1328
1329                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1330                         $startOpts .= ' SQL_SMALL_RESULT';
1331                 }
1332
1333                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1334                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1335                 }
1336
1337                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1338                         $startOpts .= ' SQL_CACHE';
1339                 }
1340
1341                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1342                         $startOpts .= ' SQL_NO_CACHE';
1343                 }
1344
1345                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1346                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1347                 } else {
1348                         $useIndex = '';
1349                 }
1350
1351                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1352         }
1353
1354         /**
1355          * Returns an optional GROUP BY with an optional HAVING
1356          *
1357          * @param array $options associative array of options
1358          * @return string
1359          * @see DatabaseBase::select()
1360          * @since 1.21
1361          */
1362         public function makeGroupByWithHaving( $options ) {
1363                 $sql = '';
1364                 if ( isset( $options['GROUP BY'] ) ) {
1365                         $gb = is_array( $options['GROUP BY'] )
1366                                 ? implode( ',', $options['GROUP BY'] )
1367                                 : $options['GROUP BY'];
1368                         $sql .= ' GROUP BY ' . $gb;
1369                 }
1370                 if ( isset( $options['HAVING'] ) ) {
1371                         $having = is_array( $options['HAVING'] )
1372                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1373                                 : $options['HAVING'];
1374                         $sql .= ' HAVING ' . $having;
1375                 }
1376
1377                 return $sql;
1378         }
1379
1380         /**
1381          * Returns an optional ORDER BY
1382          *
1383          * @param array $options associative array of options
1384          * @return string
1385          * @see DatabaseBase::select()
1386          * @since 1.21
1387          */
1388         public function makeOrderBy( $options ) {
1389                 if ( isset( $options['ORDER BY'] ) ) {
1390                         $ob = is_array( $options['ORDER BY'] )
1391                                 ? implode( ',', $options['ORDER BY'] )
1392                                 : $options['ORDER BY'];
1393
1394                         return ' ORDER BY ' . $ob;
1395                 }
1396
1397                 return '';
1398         }
1399
1400         /**
1401          * Execute a SELECT query constructed using the various parameters provided.
1402          * See below for full details of the parameters.
1403          *
1404          * @param string|array $table Table name
1405          * @param string|array $vars Field names
1406          * @param string|array $conds Conditions
1407          * @param string $fname Caller function name
1408          * @param array $options Query options
1409          * @param $join_conds Array Join conditions
1410          *
1411          * @param $table string|array
1412          *
1413          * May be either an array of table names, or a single string holding a table
1414          * name. If an array is given, table aliases can be specified, for example:
1415          *
1416          *    array( 'a' => 'user' )
1417          *
1418          * This includes the user table in the query, with the alias "a" available
1419          * for use in field names (e.g. a.user_name).
1420          *
1421          * All of the table names given here are automatically run through
1422          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1423          * added, and various other table name mappings to be performed.
1424          *
1425          *
1426          * @param $vars string|array
1427          *
1428          * May be either a field name or an array of field names. The field names
1429          * can be complete fragments of SQL, for direct inclusion into the SELECT
1430          * query. If an array is given, field aliases can be specified, for example:
1431          *
1432          *   array( 'maxrev' => 'MAX(rev_id)' )
1433          *
1434          * This includes an expression with the alias "maxrev" in the query.
1435          *
1436          * If an expression is given, care must be taken to ensure that it is
1437          * DBMS-independent.
1438          *
1439          *
1440          * @param $conds string|array
1441          *
1442          * May be either a string containing a single condition, or an array of
1443          * conditions. If an array is given, the conditions constructed from each
1444          * element are combined with AND.
1445          *
1446          * Array elements may take one of two forms:
1447          *
1448          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1449          *   - Elements with a string key are interpreted as equality conditions,
1450          *     where the key is the field name.
1451          *     - If the value of such an array element is a scalar (such as a
1452          *       string), it will be treated as data and thus quoted appropriately.
1453          *       If it is null, an IS NULL clause will be added.
1454          *     - If the value is an array, an IN(...) clause will be constructed,
1455          *       such that the field name may match any of the elements in the
1456          *       array. The elements of the array will be quoted.
1457          *
1458          * Note that expressions are often DBMS-dependent in their syntax.
1459          * DBMS-independent wrappers are provided for constructing several types of
1460          * expression commonly used in condition queries. See:
1461          *    - DatabaseBase::buildLike()
1462          *    - DatabaseBase::conditional()
1463          *
1464          *
1465          * @param $options string|array
1466          *
1467          * Optional: Array of query options. Boolean options are specified by
1468          * including them in the array as a string value with a numeric key, for
1469          * example:
1470          *
1471          *    array( 'FOR UPDATE' )
1472          *
1473          * The supported options are:
1474          *
1475          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1476          *     with LIMIT can theoretically be used for paging through a result set,
1477          *     but this is discouraged in MediaWiki for performance reasons.
1478          *
1479          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1480          *     and then the first rows are taken until the limit is reached. LIMIT
1481          *     is applied to a result set after OFFSET.
1482          *
1483          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1484          *     changed until the next COMMIT.
1485          *
1486          *   - DISTINCT: Boolean: return only unique result rows.
1487          *
1488          *   - GROUP BY: May be either an SQL fragment string naming a field or
1489          *     expression to group by, or an array of such SQL fragments.
1490          *
1491          *   - HAVING: May be either an string containing a HAVING clause or an array of
1492          *     conditions building the HAVING clause. If an array is given, the conditions
1493          *     constructed from each element are combined with AND.
1494          *
1495          *   - ORDER BY: May be either an SQL fragment giving a field name or
1496          *     expression to order by, or an array of such SQL fragments.
1497          *
1498          *   - USE INDEX: This may be either a string giving the index name to use
1499          *     for the query, or an array. If it is an associative array, each key
1500          *     gives the table name (or alias), each value gives the index name to
1501          *     use for that table. All strings are SQL fragments and so should be
1502          *     validated by the caller.
1503          *
1504          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1505          *     instead of SELECT.
1506          *
1507          * And also the following boolean MySQL extensions, see the MySQL manual
1508          * for documentation:
1509          *
1510          *    - LOCK IN SHARE MODE
1511          *    - STRAIGHT_JOIN
1512          *    - HIGH_PRIORITY
1513          *    - SQL_BIG_RESULT
1514          *    - SQL_BUFFER_RESULT
1515          *    - SQL_SMALL_RESULT
1516          *    - SQL_CALC_FOUND_ROWS
1517          *    - SQL_CACHE
1518          *    - SQL_NO_CACHE
1519          *
1520          *
1521          * @param $join_conds string|array
1522          *
1523          * Optional associative array of table-specific join conditions. In the
1524          * most common case, this is unnecessary, since the join condition can be
1525          * in $conds. However, it is useful for doing a LEFT JOIN.
1526          *
1527          * The key of the array contains the table name or alias. The value is an
1528          * array with two elements, numbered 0 and 1. The first gives the type of
1529          * join, the second is an SQL fragment giving the join condition for that
1530          * table. For example:
1531          *
1532          *    array( 'page' => array( 'LEFT JOIN', 'page_latest=rev_id' ) )
1533          *
1534          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1535          *   with no rows in it will be returned. If there was a query error, a
1536          *   DBQueryError exception will be thrown, except if the "ignore errors"
1537          *   option was set, in which case false will be returned.
1538          */
1539         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1540                 $options = array(), $join_conds = array() ) {
1541                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1542
1543                 return $this->query( $sql, $fname );
1544         }
1545
1546         /**
1547          * The equivalent of DatabaseBase::select() except that the constructed SQL
1548          * is returned, instead of being immediately executed. This can be useful for
1549          * doing UNION queries, where the SQL text of each query is needed. In general,
1550          * however, callers outside of Database classes should just use select().
1551          *
1552          * @param string|array $table Table name
1553          * @param string|array $vars Field names
1554          * @param string|array $conds Conditions
1555          * @param string $fname Caller function name
1556          * @param string|array $options Query options
1557          * @param $join_conds string|array Join conditions
1558          *
1559          * @return string SQL query string.
1560          * @see DatabaseBase::select()
1561          */
1562         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1563                 $options = array(), $join_conds = array()
1564         ) {
1565                 if ( is_array( $vars ) ) {
1566                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1567                 }
1568
1569                 $options = (array)$options;
1570                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1571                         ? $options['USE INDEX']
1572                         : array();
1573
1574                 if ( is_array( $table ) ) {
1575                         $from = ' FROM ' .
1576                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1577                 } elseif ( $table != '' ) {
1578                         if ( $table[0] == ' ' ) {
1579                                 $from = ' FROM ' . $table;
1580                         } else {
1581                                 $from = ' FROM ' .
1582                                         $this->tableNamesWithUseIndexOrJOIN( array( $table ), $useIndexes, array() );
1583                         }
1584                 } else {
1585                         $from = '';
1586                 }
1587
1588                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1589                         $this->makeSelectOptions( $options );
1590
1591                 if ( !empty( $conds ) ) {
1592                         if ( is_array( $conds ) ) {
1593                                 $conds = $this->makeList( $conds, LIST_AND );
1594                         }
1595                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1596                 } else {
1597                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1598                 }
1599
1600                 if ( isset( $options['LIMIT'] ) ) {
1601                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1602                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1603                 }
1604                 $sql = "$sql $postLimitTail";
1605
1606                 if ( isset( $options['EXPLAIN'] ) ) {
1607                         $sql = 'EXPLAIN ' . $sql;
1608                 }
1609
1610                 return $sql;
1611         }
1612
1613         /**
1614          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1615          * that a single row object is returned. If the query returns no rows,
1616          * false is returned.
1617          *
1618          * @param string|array $table Table name
1619          * @param string|array $vars Field names
1620          * @param array $conds Conditions
1621          * @param string $fname Caller function name
1622          * @param string|array $options Query options
1623          * @param $join_conds array|string Join conditions
1624          *
1625          * @return stdClass|bool
1626          */
1627         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1628                 $options = array(), $join_conds = array()
1629         ) {
1630                 $options = (array)$options;
1631                 $options['LIMIT'] = 1;
1632                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1633
1634                 if ( $res === false ) {
1635                         return false;
1636                 }
1637
1638                 if ( !$this->numRows( $res ) ) {
1639                         return false;
1640                 }
1641
1642                 $obj = $this->fetchObject( $res );
1643
1644                 return $obj;
1645         }
1646
1647         /**
1648          * Estimate rows in dataset.
1649          *
1650          * MySQL allows you to estimate the number of rows that would be returned
1651          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1652          * index cardinality statistics, and is notoriously inaccurate, especially
1653          * when large numbers of rows have recently been added or deleted.
1654          *
1655          * For DBMSs that don't support fast result size estimation, this function
1656          * will actually perform the SELECT COUNT(*).
1657          *
1658          * Takes the same arguments as DatabaseBase::select().
1659          *
1660          * @param string $table table name
1661          * @param array|string $vars : unused
1662          * @param array|string $conds : filters on the table
1663          * @param string $fname function name for profiling
1664          * @param array $options options for select
1665          * @return Integer: row count
1666          */
1667         public function estimateRowCount( $table, $vars = '*', $conds = '',
1668                 $fname = __METHOD__, $options = array()
1669         ) {
1670                 $rows = 0;
1671                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1672
1673                 if ( $res ) {
1674                         $row = $this->fetchRow( $res );
1675                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1676                 }
1677
1678                 return $rows;
1679         }
1680
1681         /**
1682          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1683          * It's only slightly flawed. Don't use for anything important.
1684          *
1685          * @param string $sql A SQL Query
1686          *
1687          * @return string
1688          */
1689         static function generalizeSQL( $sql ) {
1690                 # This does the same as the regexp below would do, but in such a way
1691                 # as to avoid crashing php on some large strings.
1692                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1693
1694                 $sql = str_replace( "\\\\", '', $sql );
1695                 $sql = str_replace( "\\'", '', $sql );
1696                 $sql = str_replace( "\\\"", '', $sql );
1697                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1698                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1699
1700                 # All newlines, tabs, etc replaced by single space
1701                 $sql = preg_replace( '/\s+/', ' ', $sql );
1702
1703                 # All numbers => N
1704                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1705                 $sql = preg_replace( '/-?\d+/s', 'N', $sql );
1706
1707                 return $sql;
1708         }
1709
1710         /**
1711          * Determines whether a field exists in a table
1712          *
1713          * @param string $table table name
1714          * @param string $field filed to check on that table
1715          * @param string $fname calling function name (optional)
1716          * @return Boolean: whether $table has filed $field
1717          */
1718         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1719                 $info = $this->fieldInfo( $table, $field );
1720
1721                 return (bool)$info;
1722         }
1723
1724         /**
1725          * Determines whether an index exists
1726          * Usually throws a DBQueryError on failure
1727          * If errors are explicitly ignored, returns NULL on failure
1728          *
1729          * @param $table
1730          * @param $index
1731          * @param $fname string
1732          *
1733          * @return bool|null
1734          */
1735         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1736                 if ( !$this->tableExists( $table ) ) {
1737                         return null;
1738                 }
1739
1740                 $info = $this->indexInfo( $table, $index, $fname );
1741                 if ( is_null( $info ) ) {
1742                         return null;
1743                 } else {
1744                         return $info !== false;
1745                 }
1746         }
1747
1748         /**
1749          * Query whether a given table exists
1750          *
1751          * @param $table string
1752          * @param $fname string
1753          *
1754          * @return bool
1755          */
1756         public function tableExists( $table, $fname = __METHOD__ ) {
1757                 $table = $this->tableName( $table );
1758                 $old = $this->ignoreErrors( true );
1759                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1760                 $this->ignoreErrors( $old );
1761
1762                 return (bool)$res;
1763         }
1764
1765         /**
1766          * Determines if a given index is unique
1767          *
1768          * @param $table string
1769          * @param $index string
1770          *
1771          * @return bool
1772          */
1773         public function indexUnique( $table, $index ) {
1774                 $indexInfo = $this->indexInfo( $table, $index );
1775
1776                 if ( !$indexInfo ) {
1777                         return null;
1778                 }
1779
1780                 return !$indexInfo[0]->Non_unique;
1781         }
1782
1783         /**
1784          * Helper for DatabaseBase::insert().
1785          *
1786          * @param $options array
1787          * @return string
1788          */
1789         protected function makeInsertOptions( $options ) {
1790                 return implode( ' ', $options );
1791         }
1792
1793         /**
1794          * INSERT wrapper, inserts an array into a table.
1795          *
1796          * $a may be either:
1797          *
1798          *   - A single associative array. The array keys are the field names, and
1799          *     the values are the values to insert. The values are treated as data
1800          *     and will be quoted appropriately. If NULL is inserted, this will be
1801          *     converted to a database NULL.
1802          *   - An array with numeric keys, holding a list of associative arrays.
1803          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1804          *     each subarray must be identical to each other, and in the same order.
1805          *
1806          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1807          * returns success.
1808          *
1809          * $options is an array of options, with boolean options encoded as values
1810          * with numeric keys, in the same style as $options in
1811          * DatabaseBase::select(). Supported options are:
1812          *
1813          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1814          *     any rows which cause duplicate key errors are not inserted. It's
1815          *     possible to determine how many rows were successfully inserted using
1816          *     DatabaseBase::affectedRows().
1817          *
1818          * @param $table   String Table name. This will be passed through
1819          *                 DatabaseBase::tableName().
1820          * @param $a       Array of rows to insert
1821          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1822          * @param array $options of options
1823          *
1824          * @return bool
1825          */
1826         public function insert( $table, $a, $fname = __METHOD__, $options = array() ) {
1827                 # No rows to insert, easy just return now
1828                 if ( !count( $a ) ) {
1829                         return true;
1830                 }
1831
1832                 $table = $this->tableName( $table );
1833
1834                 if ( !is_array( $options ) ) {
1835                         $options = array( $options );
1836                 }
1837
1838                 $fh = null;
1839                 if ( isset( $options['fileHandle'] ) ) {
1840                         $fh = $options['fileHandle'];
1841                 }
1842                 $options = $this->makeInsertOptions( $options );
1843
1844                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1845                         $multi = true;
1846                         $keys = array_keys( $a[0] );
1847                 } else {
1848                         $multi = false;
1849                         $keys = array_keys( $a );
1850                 }
1851
1852                 $sql = 'INSERT ' . $options .
1853                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1854
1855                 if ( $multi ) {
1856                         $first = true;
1857                         foreach ( $a as $row ) {
1858                                 if ( $first ) {
1859                                         $first = false;
1860                                 } else {
1861                                         $sql .= ',';
1862                                 }
1863                                 $sql .= '(' . $this->makeList( $row ) . ')';
1864                         }
1865                 } else {
1866                         $sql .= '(' . $this->makeList( $a ) . ')';
1867                 }
1868
1869                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1870                         return false;
1871                 } elseif ( $fh !== null ) {
1872                         return true;
1873                 }
1874
1875                 return (bool)$this->query( $sql, $fname );
1876         }
1877
1878         /**
1879          * Make UPDATE options for the DatabaseBase::update function
1880          *
1881          * @param array $options The options passed to DatabaseBase::update
1882          * @return string
1883          */
1884         protected function makeUpdateOptions( $options ) {
1885                 if ( !is_array( $options ) ) {
1886                         $options = array( $options );
1887                 }
1888
1889                 $opts = array();
1890
1891                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1892                         $opts[] = $this->lowPriorityOption();
1893                 }
1894
1895                 if ( in_array( 'IGNORE', $options ) ) {
1896                         $opts[] = 'IGNORE';
1897                 }
1898
1899                 return implode( ' ', $opts );
1900         }
1901
1902         /**
1903          * UPDATE wrapper. Takes a condition array and a SET array.
1904          *
1905          * @param $table  String name of the table to UPDATE. This will be passed through
1906          *                DatabaseBase::tableName().
1907          *
1908          * @param array $values An array of values to SET. For each array element,
1909          *                the key gives the field name, and the value gives the data
1910          *                to set that field to. The data will be quoted by
1911          *                DatabaseBase::addQuotes().
1912          *
1913          * @param $conds  Array:  An array of conditions (WHERE). See
1914          *                DatabaseBase::select() for the details of the format of
1915          *                condition arrays. Use '*' to update all rows.
1916          *
1917          * @param $fname  String: The function name of the caller (from __METHOD__),
1918          *                for logging and profiling.
1919          *
1920          * @param array $options An array of UPDATE options, can be:
1921          *                   - IGNORE: Ignore unique key conflicts
1922          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1923          * @return Boolean
1924          */
1925         function update( $table, $values, $conds, $fname = __METHOD__, $options = array() ) {
1926                 $table = $this->tableName( $table );
1927                 $opts = $this->makeUpdateOptions( $options );
1928                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1929
1930                 if ( $conds !== array() && $conds !== '*' ) {
1931                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1932                 }
1933
1934                 return $this->query( $sql, $fname );
1935         }
1936
1937         /**
1938          * Makes an encoded list of strings from an array
1939          * @param array $a containing the data
1940          * @param int $mode Constant
1941          *      - LIST_COMMA:          comma separated, no field names
1942          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1943          *        the documentation for $conds in DatabaseBase::select().
1944          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1945          *      - LIST_SET:            comma separated with field names, like a SET clause
1946          *      - LIST_NAMES:          comma separated field names
1947          *
1948          * @throws MWException|DBUnexpectedError
1949          * @return string
1950          */
1951         public function makeList( $a, $mode = LIST_COMMA ) {
1952                 if ( !is_array( $a ) ) {
1953                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1954                 }
1955
1956                 $first = true;
1957                 $list = '';
1958
1959                 foreach ( $a as $field => $value ) {
1960                         if ( !$first ) {
1961                                 if ( $mode == LIST_AND ) {
1962                                         $list .= ' AND ';
1963                                 } elseif ( $mode == LIST_OR ) {
1964                                         $list .= ' OR ';
1965                                 } else {
1966                                         $list .= ',';
1967                                 }
1968                         } else {
1969                                 $first = false;
1970                         }
1971
1972                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1973                                 $list .= "($value)";
1974                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1975                                 $list .= "$value";
1976                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1977                                 if ( count( $value ) == 0 ) {
1978                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1979                                 } elseif ( count( $value ) == 1 ) {
1980                                         // Special-case single values, as IN isn't terribly efficient
1981                                         // Don't necessarily assume the single key is 0; we don't
1982                                         // enforce linear numeric ordering on other arrays here.
1983                                         $value = array_values( $value );
1984                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1985                                 } else {
1986                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1987                                 }
1988                         } elseif ( $value === null ) {
1989                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1990                                         $list .= "$field IS ";
1991                                 } elseif ( $mode == LIST_SET ) {
1992                                         $list .= "$field = ";
1993                                 }
1994                                 $list .= 'NULL';
1995                         } else {
1996                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1997                                         $list .= "$field = ";
1998                                 }
1999                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
2000                         }
2001                 }
2002
2003                 return $list;
2004         }
2005
2006         /**
2007          * Build a partial where clause from a 2-d array such as used for LinkBatch.
2008          * The keys on each level may be either integers or strings.
2009          *
2010          * @param array $data organized as 2-d
2011          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
2012          * @param string $baseKey field name to match the base-level keys to (eg 'pl_namespace')
2013          * @param string $subKey field name to match the sub-level keys to (eg 'pl_title')
2014          * @return Mixed: string SQL fragment, or false if no items in array.
2015          */
2016         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2017                 $conds = array();
2018
2019                 foreach ( $data as $base => $sub ) {
2020                         if ( count( $sub ) ) {
2021                                 $conds[] = $this->makeList(
2022                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
2023                                         LIST_AND );
2024                         }
2025                 }
2026
2027                 if ( $conds ) {
2028                         return $this->makeList( $conds, LIST_OR );
2029                 } else {
2030                         // Nothing to search for...
2031                         return false;
2032                 }
2033         }
2034
2035         /**
2036          * Return aggregated value alias
2037          *
2038          * @param $valuedata
2039          * @param $valuename string
2040          *
2041          * @return string
2042          */
2043         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2044                 return $valuename;
2045         }
2046
2047         /**
2048          * @param $field
2049          * @return string
2050          */
2051         public function bitNot( $field ) {
2052                 return "(~$field)";
2053         }
2054
2055         /**
2056          * @param $fieldLeft
2057          * @param $fieldRight
2058          * @return string
2059          */
2060         public function bitAnd( $fieldLeft, $fieldRight ) {
2061                 return "($fieldLeft & $fieldRight)";
2062         }
2063
2064         /**
2065          * @param  $fieldLeft
2066          * @param  $fieldRight
2067          * @return string
2068          */
2069         public function bitOr( $fieldLeft, $fieldRight ) {
2070                 return "($fieldLeft | $fieldRight)";
2071         }
2072
2073         /**
2074          * Build a concatenation list to feed into a SQL query
2075          * @param array $stringList list of raw SQL expressions; caller is responsible for any quoting
2076          * @return String
2077          */
2078         public function buildConcat( $stringList ) {
2079                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2080         }
2081
2082         /**
2083          * Build a GROUP_CONCAT or equivalent statement for a query.
2084          *
2085          * This is useful for combining a field for several rows into a single string.
2086          * NULL values will not appear in the output, duplicated values will appear,
2087          * and the resulting delimiter-separated values have no defined sort order.
2088          * Code using the results may need to use the PHP unique() or sort() methods.
2089          *
2090          * @param string $delim Glue to bind the results together
2091          * @param string|array $table Table name
2092          * @param string $field Field name
2093          * @param string|array $conds Conditions
2094          * @param string|array $join_conds Join conditions
2095          * @return String SQL text
2096          * @since 1.23
2097          */
2098         public function buildGroupConcatField(
2099                 $delim, $table, $field, $conds = '', $join_conds = array()
2100         ) {
2101                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
2102
2103                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, array(), $join_conds ) . ')';
2104         }
2105
2106         /**
2107          * Change the current database
2108          *
2109          * @todo Explain what exactly will fail if this is not overridden.
2110          *
2111          * @param $db
2112          *
2113          * @return bool Success or failure
2114          */
2115         public function selectDB( $db ) {
2116                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
2117                 # if your database engine supports a concept similar to MySQL's
2118                 # databases you may as well.
2119                 $this->mDBname = $db;
2120
2121                 return true;
2122         }
2123
2124         /**
2125          * Get the current DB name
2126          */
2127         public function getDBname() {
2128                 return $this->mDBname;
2129         }
2130
2131         /**
2132          * Get the server hostname or IP address
2133          */
2134         public function getServer() {
2135                 return $this->mServer;
2136         }
2137
2138         /**
2139          * Format a table name ready for use in constructing an SQL query
2140          *
2141          * This does two important things: it quotes the table names to clean them up,
2142          * and it adds a table prefix if only given a table name with no quotes.
2143          *
2144          * All functions of this object which require a table name call this function
2145          * themselves. Pass the canonical name to such functions. This is only needed
2146          * when calling query() directly.
2147          *
2148          * @param string $name database table name
2149          * @param string $format One of:
2150          *   quoted - Automatically pass the table name through addIdentifierQuotes()
2151          *            so that it can be used in a query.
2152          *   raw - Do not add identifier quotes to the table name
2153          * @return String: full database name
2154          */
2155         public function tableName( $name, $format = 'quoted' ) {
2156                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
2157                 # Skip the entire process when we have a string quoted on both ends.
2158                 # Note that we check the end so that we will still quote any use of
2159                 # use of `database`.table. But won't break things if someone wants
2160                 # to query a database table with a dot in the name.
2161                 if ( $this->isQuotedIdentifier( $name ) ) {
2162                         return $name;
2163                 }
2164
2165                 # Lets test for any bits of text that should never show up in a table
2166                 # name. Basically anything like JOIN or ON which are actually part of
2167                 # SQL queries, but may end up inside of the table value to combine
2168                 # sql. Such as how the API is doing.
2169                 # Note that we use a whitespace test rather than a \b test to avoid
2170                 # any remote case where a word like on may be inside of a table name
2171                 # surrounded by symbols which may be considered word breaks.
2172                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2173                         return $name;
2174                 }
2175
2176                 # Split database and table into proper variables.
2177                 # We reverse the explode so that database.table and table both output
2178                 # the correct table.
2179                 $dbDetails = explode( '.', $name, 2 );
2180                 if ( count( $dbDetails ) == 2 ) {
2181                         list( $database, $table ) = $dbDetails;
2182                         # We don't want any prefix added in this case
2183                         $prefix = '';
2184                 } else {
2185                         list( $table ) = $dbDetails;
2186                         if ( $wgSharedDB !== null # We have a shared database
2187                                 && $this->mForeign == false # We're not working on a foreign database
2188                                 && !$this->isQuotedIdentifier( $table ) # Prevent shared tables listing '`table`'
2189                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
2190                         ) {
2191                                 $database = $wgSharedDB;
2192                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
2193                         } else {
2194                                 $database = null;
2195                                 $prefix = $this->mTablePrefix; # Default prefix
2196                         }
2197                 }
2198
2199                 # Quote $table and apply the prefix if not quoted.
2200                 $tableName = "{$prefix}{$table}";
2201                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) ) {
2202                         $tableName = $this->addIdentifierQuotes( $tableName );
2203                 }
2204
2205                 # Quote $database and merge it with the table name if needed
2206                 if ( $database !== null ) {
2207                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2208                                 $database = $this->addIdentifierQuotes( $database );
2209                         }
2210                         $tableName = $database . '.' . $tableName;
2211                 }
2212
2213                 return $tableName;
2214         }
2215
2216         /**
2217          * Fetch a number of table names into an array
2218          * This is handy when you need to construct SQL for joins
2219          *
2220          * Example:
2221          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
2222          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2223          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2224          *
2225          * @return array
2226          */
2227         public function tableNames() {
2228                 $inArray = func_get_args();
2229                 $retVal = array();
2230
2231                 foreach ( $inArray as $name ) {
2232                         $retVal[$name] = $this->tableName( $name );
2233                 }
2234
2235                 return $retVal;
2236         }
2237
2238         /**
2239          * Fetch a number of table names into an zero-indexed numerical array
2240          * This is handy when you need to construct SQL for joins
2241          *
2242          * Example:
2243          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
2244          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2245          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2246          *
2247          * @return array
2248          */
2249         public function tableNamesN() {
2250                 $inArray = func_get_args();
2251                 $retVal = array();
2252
2253                 foreach ( $inArray as $name ) {
2254                         $retVal[] = $this->tableName( $name );
2255                 }
2256
2257                 return $retVal;
2258         }
2259
2260         /**
2261          * Get an aliased table name
2262          * e.g. tableName AS newTableName
2263          *
2264          * @param string $name Table name, see tableName()
2265          * @param string|bool $alias Alias (optional)
2266          * @return string SQL name for aliased table. Will not alias a table to its own name
2267          */
2268         public function tableNameWithAlias( $name, $alias = false ) {
2269                 if ( !$alias || $alias == $name ) {
2270                         return $this->tableName( $name );
2271                 } else {
2272                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2273                 }
2274         }
2275
2276         /**
2277          * Gets an array of aliased table names
2278          *
2279          * @param $tables array( [alias] => table )
2280          * @return array of strings, see tableNameWithAlias()
2281          */
2282         public function tableNamesWithAlias( $tables ) {
2283                 $retval = array();
2284                 foreach ( $tables as $alias => $table ) {
2285                         if ( is_numeric( $alias ) ) {
2286                                 $alias = $table;
2287                         }
2288                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2289                 }
2290
2291                 return $retval;
2292         }
2293
2294         /**
2295          * Get an aliased field name
2296          * e.g. fieldName AS newFieldName
2297          *
2298          * @param string $name Field name
2299          * @param string|bool $alias Alias (optional)
2300          * @return string SQL name for aliased field. Will not alias a field to its own name
2301          */
2302         public function fieldNameWithAlias( $name, $alias = false ) {
2303                 if ( !$alias || (string)$alias === (string)$name ) {
2304                         return $name;
2305                 } else {
2306                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2307                 }
2308         }
2309
2310         /**
2311          * Gets an array of aliased field names
2312          *
2313          * @param $fields array( [alias] => field )
2314          * @return array of strings, see fieldNameWithAlias()
2315          */
2316         public function fieldNamesWithAlias( $fields ) {
2317                 $retval = array();
2318                 foreach ( $fields as $alias => $field ) {
2319                         if ( is_numeric( $alias ) ) {
2320                                 $alias = $field;
2321                         }
2322                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2323                 }
2324
2325                 return $retval;
2326         }
2327
2328         /**
2329          * Get the aliased table name clause for a FROM clause
2330          * which might have a JOIN and/or USE INDEX clause
2331          *
2332          * @param array $tables ( [alias] => table )
2333          * @param $use_index array Same as for select()
2334          * @param $join_conds array Same as for select()
2335          * @return string
2336          */
2337         protected function tableNamesWithUseIndexOrJOIN(
2338                 $tables, $use_index = array(), $join_conds = array()
2339         ) {
2340                 $ret = array();
2341                 $retJOIN = array();
2342                 $use_index = (array)$use_index;
2343                 $join_conds = (array)$join_conds;
2344
2345                 foreach ( $tables as $alias => $table ) {
2346                         if ( !is_string( $alias ) ) {
2347                                 // No alias? Set it equal to the table name
2348                                 $alias = $table;
2349                         }
2350                         // Is there a JOIN clause for this table?
2351                         if ( isset( $join_conds[$alias] ) ) {
2352                                 list( $joinType, $conds ) = $join_conds[$alias];
2353                                 $tableClause = $joinType;
2354                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2355                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2356                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2357                                         if ( $use != '' ) {
2358                                                 $tableClause .= ' ' . $use;
2359                                         }
2360                                 }
2361                                 $on = $this->makeList( (array)$conds, LIST_AND );
2362                                 if ( $on != '' ) {
2363                                         $tableClause .= ' ON (' . $on . ')';
2364                                 }
2365
2366                                 $retJOIN[] = $tableClause;
2367                         // Is there an INDEX clause for this table?
2368                         } elseif ( isset( $use_index[$alias] ) ) {
2369                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2370                                 $tableClause .= ' ' . $this->useIndexClause(
2371                                         implode( ',', (array)$use_index[$alias] ) );
2372
2373                                 $ret[] = $tableClause;
2374                         } else {
2375                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2376
2377                                 $ret[] = $tableClause;
2378                         }
2379                 }
2380
2381                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2382                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2383                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2384
2385                 // Compile our final table clause
2386                 return implode( ' ', array( $implicitJoins, $explicitJoins ) );
2387         }
2388
2389         /**
2390          * Get the name of an index in a given table
2391          *
2392          * @param $index
2393          *
2394          * @return string
2395          */
2396         protected function indexName( $index ) {
2397                 // Backwards-compatibility hack
2398                 $renamed = array(
2399                         'ar_usertext_timestamp' => 'usertext_timestamp',
2400                         'un_user_id' => 'user_id',
2401                         'un_user_ip' => 'user_ip',
2402                 );
2403
2404                 if ( isset( $renamed[$index] ) ) {
2405                         return $renamed[$index];
2406                 } else {
2407                         return $index;
2408                 }
2409         }
2410
2411         /**
2412          * Adds quotes and backslashes.
2413          *
2414          * @param $s string
2415          *
2416          * @return string
2417          */
2418         public function addQuotes( $s ) {
2419                 if ( $s === null ) {
2420                         return 'NULL';
2421                 } else {
2422                         # This will also quote numeric values. This should be harmless,
2423                         # and protects against weird problems that occur when they really
2424                         # _are_ strings such as article titles and string->number->string
2425                         # conversion is not 1:1.
2426                         return "'" . $this->strencode( $s ) . "'";
2427                 }
2428         }
2429
2430         /**
2431          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2432          * MySQL uses `backticks` while basically everything else uses double quotes.
2433          * Since MySQL is the odd one out here the double quotes are our generic
2434          * and we implement backticks in DatabaseMysql.
2435          *
2436          * @param $s string
2437          *
2438          * @return string
2439          */
2440         public function addIdentifierQuotes( $s ) {
2441                 return '"' . str_replace( '"', '""', $s ) . '"';
2442         }
2443
2444         /**
2445          * Returns if the given identifier looks quoted or not according to
2446          * the database convention for quoting identifiers .
2447          *
2448          * @param $name string
2449          *
2450          * @return boolean
2451          */
2452         public function isQuotedIdentifier( $name ) {
2453                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2454         }
2455
2456         /**
2457          * @param $s string
2458          * @return string
2459          */
2460         protected function escapeLikeInternal( $s ) {
2461                 $s = str_replace( '\\', '\\\\', $s );
2462                 $s = $this->strencode( $s );
2463                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2464
2465                 return $s;
2466         }
2467
2468         /**
2469          * LIKE statement wrapper, receives a variable-length argument list with
2470          * parts of pattern to match containing either string literals that will be
2471          * escaped or tokens returned by anyChar() or anyString(). Alternatively,
2472          * the function could be provided with an array of aforementioned
2473          * parameters.
2474          *
2475          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
2476          * a LIKE clause that searches for subpages of 'My page title'.
2477          * Alternatively:
2478          *   $pattern = array( 'My_page_title/', $dbr->anyString() );
2479          *   $query .= $dbr->buildLike( $pattern );
2480          *
2481          * @since 1.16
2482          * @return String: fully built LIKE statement
2483          */
2484         public function buildLike() {
2485                 $params = func_get_args();
2486
2487                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2488                         $params = $params[0];
2489                 }
2490
2491                 $s = '';
2492
2493                 foreach ( $params as $value ) {
2494                         if ( $value instanceof LikeMatch ) {
2495                                 $s .= $value->toString();
2496                         } else {
2497                                 $s .= $this->escapeLikeInternal( $value );
2498                         }
2499                 }
2500
2501                 return " LIKE '" . $s . "' ";
2502         }
2503
2504         /**
2505          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2506          *
2507          * @return LikeMatch
2508          */
2509         public function anyChar() {
2510                 return new LikeMatch( '_' );
2511         }
2512
2513         /**
2514          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2515          *
2516          * @return LikeMatch
2517          */
2518         public function anyString() {
2519                 return new LikeMatch( '%' );
2520         }
2521
2522         /**
2523          * Returns an appropriately quoted sequence value for inserting a new row.
2524          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2525          * subclass will return an integer, and save the value for insertId()
2526          *
2527          * Any implementation of this function should *not* involve reusing
2528          * sequence numbers created for rolled-back transactions.
2529          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2530          * @param $seqName string
2531          * @return null
2532          */
2533         public function nextSequenceValue( $seqName ) {
2534                 return null;
2535         }
2536
2537         /**
2538          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2539          * is only needed because a) MySQL must be as efficient as possible due to
2540          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2541          * which index to pick.  Anyway, other databases might have different
2542          * indexes on a given table.  So don't bother overriding this unless you're
2543          * MySQL.
2544          * @param $index
2545          * @return string
2546          */
2547         public function useIndexClause( $index ) {
2548                 return '';
2549         }
2550
2551         /**
2552          * REPLACE query wrapper.
2553          *
2554          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2555          * except that when there is a duplicate key error, the old row is deleted
2556          * and the new row is inserted in its place.
2557          *
2558          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2559          * perform the delete, we need to know what the unique indexes are so that
2560          * we know how to find the conflicting rows.
2561          *
2562          * It may be more efficient to leave off unique indexes which are unlikely
2563          * to collide. However if you do this, you run the risk of encountering
2564          * errors which wouldn't have occurred in MySQL.
2565          *
2566          * @param string $table The table to replace the row(s) in.
2567          * @param array $rows Can be either a single row to insert, or multiple rows,
2568          *    in the same format as for DatabaseBase::insert()
2569          * @param array $uniqueIndexes is an array of indexes. Each element may be either
2570          *    a field name or an array of field names
2571          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2572          */
2573         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2574                 $quotedTable = $this->tableName( $table );
2575
2576                 if ( count( $rows ) == 0 ) {
2577                         return;
2578                 }
2579
2580                 # Single row case
2581                 if ( !is_array( reset( $rows ) ) ) {
2582                         $rows = array( $rows );
2583                 }
2584
2585                 foreach ( $rows as $row ) {
2586                         # Delete rows which collide
2587                         if ( $uniqueIndexes ) {
2588                                 $sql = "DELETE FROM $quotedTable WHERE ";
2589                                 $first = true;
2590                                 foreach ( $uniqueIndexes as $index ) {
2591                                         if ( $first ) {
2592                                                 $first = false;
2593                                                 $sql .= '( ';
2594                                         } else {
2595                                                 $sql .= ' ) OR ( ';
2596                                         }
2597                                         if ( is_array( $index ) ) {
2598                                                 $first2 = true;
2599                                                 foreach ( $index as $col ) {
2600                                                         if ( $first2 ) {
2601                                                                 $first2 = false;
2602                                                         } else {
2603                                                                 $sql .= ' AND ';
2604                                                         }
2605                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2606                                                 }
2607                                         } else {
2608                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2609                                         }
2610                                 }
2611                                 $sql .= ' )';
2612                                 $this->query( $sql, $fname );
2613                         }
2614
2615                         # Now insert the row
2616                         $this->insert( $table, $row, $fname );
2617                 }
2618         }
2619
2620         /**
2621          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2622          * statement.
2623          *
2624          * @param string $table Table name
2625          * @param array $rows Rows to insert
2626          * @param string $fname Caller function name
2627          *
2628          * @return ResultWrapper
2629          */
2630         protected function nativeReplace( $table, $rows, $fname ) {
2631                 $table = $this->tableName( $table );
2632
2633                 # Single row case
2634                 if ( !is_array( reset( $rows ) ) ) {
2635                         $rows = array( $rows );
2636                 }
2637
2638                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2639                 $first = true;
2640
2641                 foreach ( $rows as $row ) {
2642                         if ( $first ) {
2643                                 $first = false;
2644                         } else {
2645                                 $sql .= ',';
2646                         }
2647
2648                         $sql .= '(' . $this->makeList( $row ) . ')';
2649                 }
2650
2651                 return $this->query( $sql, $fname );
2652         }
2653
2654         /**
2655          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
2656          *
2657          * This updates any conflicting rows (according to the unique indexes) using
2658          * the provided SET clause and inserts any remaining (non-conflicted) rows.
2659          *
2660          * $rows may be either:
2661          *   - A single associative array. The array keys are the field names, and
2662          *     the values are the values to insert. The values are treated as data
2663          *     and will be quoted appropriately. If NULL is inserted, this will be
2664          *     converted to a database NULL.
2665          *   - An array with numeric keys, holding a list of associative arrays.
2666          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
2667          *     each subarray must be identical to each other, and in the same order.
2668          *
2669          * It may be more efficient to leave off unique indexes which are unlikely
2670          * to collide. However if you do this, you run the risk of encountering
2671          * errors which wouldn't have occurred in MySQL.
2672          *
2673          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
2674          * returns success.
2675          *
2676          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
2677          * @param array $rows A single row or list of rows to insert
2678          * @param array $uniqueIndexes List of single field names or field name tuples
2679          * @param array $set An array of values to SET. For each array element,
2680          *                the key gives the field name, and the value gives the data
2681          *                to set that field to. The data will be quoted by
2682          *                DatabaseBase::addQuotes().
2683          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
2684          *
2685          * @return bool
2686          * @since 1.22
2687          */
2688         public function upsert(
2689                 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
2690         ) {
2691                 if ( !count( $rows ) ) {
2692                         return true; // nothing to do
2693                 }
2694                 $rows = is_array( reset( $rows ) ) ? $rows : array( $rows );
2695
2696                 if ( count( $uniqueIndexes ) ) {
2697                         $clauses = array(); // list WHERE clauses that each identify a single row
2698                         foreach ( $rows as $row ) {
2699                                 foreach ( $uniqueIndexes as $index ) {
2700                                         $index = is_array( $index ) ? $index : array( $index ); // columns
2701                                         $rowKey = array(); // unique key to this row
2702                                         foreach ( $index as $column ) {
2703                                                 $rowKey[$column] = $row[$column];
2704                                         }
2705                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2706                                 }
2707                         }
2708                         $where = array( $this->makeList( $clauses, LIST_OR ) );
2709                 } else {
2710                         $where = false;
2711                 }
2712
2713                 $useTrx = !$this->mTrxLevel;
2714                 if ( $useTrx ) {
2715                         $this->begin( $fname );
2716                 }
2717                 try {
2718                         # Update any existing conflicting row(s)
2719                         if ( $where !== false ) {
2720                                 $ok = $this->update( $table, $set, $where, $fname );
2721                         } else {
2722                                 $ok = true;
2723                         }
2724                         # Now insert any non-conflicting row(s)
2725                         $ok = $this->insert( $table, $rows, $fname, array( 'IGNORE' ) ) && $ok;
2726                 } catch ( Exception $e ) {
2727                         if ( $useTrx ) {
2728                                 $this->rollback( $fname );
2729                         }
2730                         throw $e;
2731                 }
2732                 if ( $useTrx ) {
2733                         $this->commit( $fname );
2734                 }
2735
2736                 return $ok;
2737         }
2738
2739         /**
2740          * DELETE where the condition is a join.
2741          *
2742          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2743          * we use sub-selects
2744          *
2745          * For safety, an empty $conds will not delete everything. If you want to
2746          * delete all rows where the join condition matches, set $conds='*'.
2747          *
2748          * DO NOT put the join condition in $conds.
2749          *
2750          * @param $delTable   String: The table to delete from.
2751          * @param $joinTable  String: The other table.
2752          * @param $delVar     String: The variable to join on, in the first table.
2753          * @param $joinVar    String: The variable to join on, in the second table.
2754          * @param $conds      Array: Condition array of field names mapped to variables,
2755          *                    ANDed together in the WHERE clause
2756          * @param $fname      String: Calling function name (use __METHOD__) for
2757          *                    logs/profiling
2758          * @throws DBUnexpectedError
2759          */
2760         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2761                 $fname = __METHOD__
2762         ) {
2763                 if ( !$conds ) {
2764                         throw new DBUnexpectedError( $this,
2765                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2766                 }
2767
2768                 $delTable = $this->tableName( $delTable );
2769                 $joinTable = $this->tableName( $joinTable );
2770                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2771                 if ( $conds != '*' ) {
2772                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2773                 }
2774                 $sql .= ')';
2775
2776                 $this->query( $sql, $fname );
2777         }
2778
2779         /**
2780          * Returns the size of a text field, or -1 for "unlimited"
2781          *
2782          * @param $table string
2783          * @param $field string
2784          *
2785          * @return int
2786          */
2787         public function textFieldSize( $table, $field ) {
2788                 $table = $this->tableName( $table );
2789                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2790                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2791                 $row = $this->fetchObject( $res );
2792
2793                 $m = array();
2794
2795                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2796                         $size = $m[1];
2797                 } else {
2798                         $size = -1;
2799                 }
2800
2801                 return $size;
2802         }
2803
2804         /**
2805          * A string to insert into queries to show that they're low-priority, like
2806          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2807          * string and nothing bad should happen.
2808          *
2809          * @return string Returns the text of the low priority option if it is
2810          *   supported, or a blank string otherwise
2811          */
2812         public function lowPriorityOption() {
2813                 return '';
2814         }
2815
2816         /**
2817          * DELETE query wrapper.
2818          *
2819          * @param array $table Table name
2820          * @param string|array $conds of conditions. See $conds in DatabaseBase::select() for
2821          *               the format. Use $conds == "*" to delete all rows
2822          * @param string $fname name of the calling function
2823          *
2824          * @throws DBUnexpectedError
2825          * @return bool|ResultWrapper
2826          */
2827         public function delete( $table, $conds, $fname = __METHOD__ ) {
2828                 if ( !$conds ) {
2829                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2830                 }
2831
2832                 $table = $this->tableName( $table );
2833                 $sql = "DELETE FROM $table";
2834
2835                 if ( $conds != '*' ) {
2836                         if ( is_array( $conds ) ) {
2837                                 $conds = $this->makeList( $conds, LIST_AND );
2838                         }
2839                         $sql .= ' WHERE ' . $conds;
2840                 }
2841
2842                 return $this->query( $sql, $fname );
2843         }
2844
2845         /**
2846          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2847          * into another table.
2848          *
2849          * @param string $destTable The table name to insert into
2850          * @param string|array $srcTable May be either a table name, or an array of table names
2851          *    to include in a join.
2852          *
2853          * @param array $varMap must be an associative array of the form
2854          *    array( 'dest1' => 'source1', ...). Source items may be literals
2855          *    rather than field names, but strings should be quoted with
2856          *    DatabaseBase::addQuotes()
2857          *
2858          * @param array $conds Condition array. See $conds in DatabaseBase::select() for
2859          *    the details of the format of condition arrays. May be "*" to copy the
2860          *    whole table.
2861          *
2862          * @param string $fname The function name of the caller, from __METHOD__
2863          *
2864          * @param array $insertOptions Options for the INSERT part of the query, see
2865          *    DatabaseBase::insert() for details.
2866          * @param array $selectOptions Options for the SELECT part of the query, see
2867          *    DatabaseBase::select() for details.
2868          *
2869          * @return ResultWrapper
2870          */
2871         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2872                 $fname = __METHOD__,
2873                 $insertOptions = array(), $selectOptions = array()
2874         ) {
2875                 $destTable = $this->tableName( $destTable );
2876
2877                 if ( !is_array( $insertOptions ) ) {
2878                         $insertOptions = array( $insertOptions );
2879                 }
2880
2881                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2882
2883                 if ( !is_array( $selectOptions ) ) {
2884                         $selectOptions = array( $selectOptions );
2885                 }
2886
2887                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2888
2889                 if ( is_array( $srcTable ) ) {
2890                         $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2891                 } else {
2892                         $srcTable = $this->tableName( $srcTable );
2893                 }
2894
2895                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2896                         " SELECT $startOpts " . implode( ',', $varMap ) .
2897                         " FROM $srcTable $useIndex ";
2898
2899                 if ( $conds != '*' ) {
2900                         if ( is_array( $conds ) ) {
2901                                 $conds = $this->makeList( $conds, LIST_AND );
2902                         }
2903                         $sql .= " WHERE $conds";
2904                 }
2905
2906                 $sql .= " $tailOpts";
2907
2908                 return $this->query( $sql, $fname );
2909         }
2910
2911         /**
2912          * Construct a LIMIT query with optional offset.  This is used for query
2913          * pages.  The SQL should be adjusted so that only the first $limit rows
2914          * are returned.  If $offset is provided as well, then the first $offset
2915          * rows should be discarded, and the next $limit rows should be returned.
2916          * If the result of the query is not ordered, then the rows to be returned
2917          * are theoretically arbitrary.
2918          *
2919          * $sql is expected to be a SELECT, if that makes a difference.
2920          *
2921          * The version provided by default works in MySQL and SQLite.  It will very
2922          * likely need to be overridden for most other DBMSes.
2923          *
2924          * @param string $sql SQL query we will append the limit too
2925          * @param $limit Integer the SQL limit
2926          * @param $offset Integer|bool the SQL offset (default false)
2927          *
2928          * @throws DBUnexpectedError
2929          * @return string
2930          */
2931         public function limitResult( $sql, $limit, $offset = false ) {
2932                 if ( !is_numeric( $limit ) ) {
2933                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2934                 }
2935
2936                 return "$sql LIMIT "
2937                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2938                         . "{$limit} ";
2939         }
2940
2941         /**
2942          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2943          * within the UNION construct.
2944          * @return Boolean
2945          */
2946         public function unionSupportsOrderAndLimit() {
2947                 return true; // True for almost every DB supported
2948         }
2949
2950         /**
2951          * Construct a UNION query
2952          * This is used for providing overload point for other DB abstractions
2953          * not compatible with the MySQL syntax.
2954          * @param array $sqls SQL statements to combine
2955          * @param $all Boolean: use UNION ALL
2956          * @return String: SQL fragment
2957          */
2958         public function unionQueries( $sqls, $all ) {
2959                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2960
2961                 return '(' . implode( $glue, $sqls ) . ')';
2962         }
2963
2964         /**
2965          * Returns an SQL expression for a simple conditional.  This doesn't need
2966          * to be overridden unless CASE isn't supported in your DBMS.
2967          *
2968          * @param string|array $cond SQL expression which will result in a boolean value
2969          * @param string $trueVal SQL expression to return if true
2970          * @param string $falseVal SQL expression to return if false
2971          * @return String: SQL fragment
2972          */
2973         public function conditional( $cond, $trueVal, $falseVal ) {
2974                 if ( is_array( $cond ) ) {
2975                         $cond = $this->makeList( $cond, LIST_AND );
2976                 }
2977
2978                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2979         }
2980
2981         /**
2982          * Returns a comand for str_replace function in SQL query.
2983          * Uses REPLACE() in MySQL
2984          *
2985          * @param string $orig column to modify
2986          * @param string $old column to seek
2987          * @param string $new column to replace with
2988          *
2989          * @return string
2990          */
2991         public function strreplace( $orig, $old, $new ) {
2992                 return "REPLACE({$orig}, {$old}, {$new})";
2993         }
2994
2995         /**
2996          * Determines how long the server has been up
2997          * STUB
2998          *
2999          * @return int
3000          */
3001         public function getServerUptime() {
3002                 return 0;
3003         }
3004
3005         /**
3006          * Determines if the last failure was due to a deadlock
3007          * STUB
3008          *
3009          * @return bool
3010          */
3011         public function wasDeadlock() {
3012                 return false;
3013         }
3014
3015         /**
3016          * Determines if the last failure was due to a lock timeout
3017          * STUB
3018          *
3019          * @return bool
3020          */
3021         public function wasLockTimeout() {
3022                 return false;
3023         }
3024
3025         /**
3026          * Determines if the last query error was something that should be dealt
3027          * with by pinging the connection and reissuing the query.
3028          * STUB
3029          *
3030          * @return bool
3031          */
3032         public function wasErrorReissuable() {
3033                 return false;
3034         }
3035
3036         /**
3037          * Determines if the last failure was due to the database being read-only.
3038          * STUB
3039          *
3040          * @return bool
3041          */
3042         public function wasReadOnlyError() {
3043                 return false;
3044         }
3045
3046         /**
3047          * Perform a deadlock-prone transaction.
3048          *
3049          * This function invokes a callback function to perform a set of write
3050          * queries. If a deadlock occurs during the processing, the transaction
3051          * will be rolled back and the callback function will be called again.
3052          *
3053          * Usage:
3054          *   $dbw->deadlockLoop( callback, ... );
3055          *
3056          * Extra arguments are passed through to the specified callback function.
3057          *
3058          * Returns whatever the callback function returned on its successful,
3059          * iteration, or false on error, for example if the retry limit was
3060          * reached.
3061          *
3062          * @return bool
3063          */
3064         public function deadlockLoop() {
3065                 $this->begin( __METHOD__ );
3066                 $args = func_get_args();
3067                 $function = array_shift( $args );
3068                 $oldIgnore = $this->ignoreErrors( true );
3069                 $tries = self::DEADLOCK_TRIES;
3070
3071                 if ( is_array( $function ) ) {
3072                         $fname = $function[0];
3073                 } else {
3074                         $fname = $function;
3075                 }
3076
3077                 do {
3078                         $retVal = call_user_func_array( $function, $args );
3079                         $error = $this->lastError();
3080                         $errno = $this->lastErrno();
3081                         $sql = $this->lastQuery();
3082
3083                         if ( $errno ) {
3084                                 if ( $this->wasDeadlock() ) {
3085                                         # Retry
3086                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3087                                 } else {
3088                                         $this->reportQueryError( $error, $errno, $sql, $fname );
3089                                 }
3090                         }
3091                 } while ( $this->wasDeadlock() && --$tries > 0 );
3092
3093                 $this->ignoreErrors( $oldIgnore );
3094
3095                 if ( $tries <= 0 ) {
3096                         $this->rollback( __METHOD__ );
3097                         $this->reportQueryError( $error, $errno, $sql, $fname );
3098
3099                         return false;
3100                 } else {
3101                         $this->commit( __METHOD__ );
3102
3103                         return $retVal;
3104                 }
3105         }
3106
3107         /**
3108          * Wait for the slave to catch up to a given master position.
3109          *
3110          * @param $pos DBMasterPos object
3111          * @param $timeout Integer: the maximum number of seconds to wait for
3112          *   synchronisation
3113          *
3114          * @return integer: zero if the slave was past that position already,
3115          *   greater than zero if we waited for some period of time, less than
3116          *   zero if we timed out.
3117          */
3118         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3119                 wfProfileIn( __METHOD__ );
3120
3121                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3122                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
3123
3124                         if ( $wait > $timeout * 1e6 ) {
3125                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
3126                                 wfProfileOut( __METHOD__ );
3127
3128                                 return -1;
3129                         } elseif ( $wait > 0 ) {
3130                                 wfDebug( "Fake slave waiting $wait us\n" );
3131                                 usleep( $wait );
3132                                 wfProfileOut( __METHOD__ );
3133
3134                                 return 1;
3135                         } else {
3136                                 wfDebug( "Fake slave up to date ($wait us)\n" );
3137                                 wfProfileOut( __METHOD__ );
3138
3139                                 return 0;
3140                         }
3141                 }
3142
3143                 wfProfileOut( __METHOD__ );
3144
3145                 # Real waits are implemented in the subclass.
3146                 return 0;
3147         }
3148
3149         /**
3150          * Get the replication position of this slave
3151          *
3152          * @return DBMasterPos, or false if this is not a slave.
3153          */
3154         public function getSlavePos() {
3155                 if ( !is_null( $this->mFakeSlaveLag ) ) {
3156                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
3157                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
3158
3159                         return $pos;
3160                 } else {
3161                         # Stub
3162                         return false;
3163                 }
3164         }
3165
3166         /**
3167          * Get the position of this master
3168          *
3169          * @return DBMasterPos, or false if this is not a master
3170          */
3171         public function getMasterPos() {
3172                 if ( $this->mFakeMaster ) {
3173                         return new MySQLMasterPos( 'fake', microtime( true ) );
3174                 } else {
3175                         return false;
3176                 }
3177         }
3178
3179         /**
3180          * Run an anonymous function as soon as there is no transaction pending.
3181          * If there is a transaction and it is rolled back, then the callback is cancelled.
3182          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
3183          * Callbacks must commit any transactions that they begin.
3184          *
3185          * This is useful for updates to different systems or when separate transactions are needed.
3186          * For example, one might want to enqueue jobs into a system outside the database, but only
3187          * after the database is updated so that the jobs will see the data when they actually run.
3188          * It can also be used for updates that easily cause deadlocks if locks are held too long.
3189          *
3190          * @param callable $callback
3191          * @since 1.20
3192          */
3193         final public function onTransactionIdle( $callback ) {
3194                 $this->mTrxIdleCallbacks[] = array( $callback, wfGetCaller() );
3195                 if ( !$this->mTrxLevel ) {
3196                         $this->runOnTransactionIdleCallbacks();
3197                 }
3198         }
3199
3200         /**
3201          * Run an anonymous function before the current transaction commits or now if there is none.
3202          * If there is a transaction and it is rolled back, then the callback is cancelled.
3203          * Callbacks must not start nor commit any transactions.
3204          *
3205          * This is useful for updates that easily cause deadlocks if locks are held too long
3206          * but where atomicity is strongly desired for these updates and some related updates.
3207          *
3208          * @param callable $callback
3209          * @since 1.22
3210          */
3211         final public function onTransactionPreCommitOrIdle( $callback ) {
3212                 if ( $this->mTrxLevel ) {
3213                         $this->mTrxPreCommitCallbacks[] = array( $callback, wfGetCaller() );
3214                 } else {
3215                         $this->onTransactionIdle( $callback ); // this will trigger immediately
3216                 }
3217         }
3218
3219         /**
3220          * Actually any "on transaction idle" callbacks.
3221          *
3222          * @since 1.20
3223          */
3224         protected function runOnTransactionIdleCallbacks() {
3225                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
3226
3227                 $e = null; // last exception
3228                 do { // callbacks may add callbacks :)
3229                         $callbacks = $this->mTrxIdleCallbacks;
3230                         $this->mTrxIdleCallbacks = array(); // recursion guard
3231                         foreach ( $callbacks as $callback ) {
3232                                 try {
3233                                         list( $phpCallback ) = $callback;
3234                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
3235                                         call_user_func( $phpCallback );
3236                                         $this->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore automatic begin()
3237                                 } catch ( Exception $e ) {
3238                                 }
3239                         }
3240                 } while ( count( $this->mTrxIdleCallbacks ) );
3241
3242                 if ( $e instanceof Exception ) {
3243                         throw $e; // re-throw any last exception
3244                 }
3245         }
3246
3247         /**
3248          * Actually any "on transaction pre-commit" callbacks.
3249          *
3250          * @since 1.22
3251          */
3252         protected function runOnTransactionPreCommitCallbacks() {
3253                 $e = null; // last exception
3254                 do { // callbacks may add callbacks :)
3255                         $callbacks = $this->mTrxPreCommitCallbacks;
3256                         $this->mTrxPreCommitCallbacks = array(); // recursion guard
3257                         foreach ( $callbacks as $callback ) {
3258                                 try {
3259                                         list( $phpCallback ) = $callback;
3260                                         call_user_func( $phpCallback );
3261                                 } catch ( Exception $e ) {
3262                                 }
3263                         }
3264                 } while ( count( $this->mTrxPreCommitCallbacks ) );
3265
3266                 if ( $e instanceof Exception ) {
3267                         throw $e; // re-throw any last exception
3268                 }
3269         }
3270
3271         /**
3272          * Begin an atomic section of statements
3273          *
3274          * If a transaction has been started already, just keep track of the given
3275          * section name to make sure the transaction is not committed pre-maturely.
3276          * This function can be used in layers (with sub-sections), so use a stack
3277          * to keep track of the different atomic sections. If there is no transaction,
3278          * start one implicitly.
3279          *
3280          * The goal of this function is to create an atomic section of SQL queries
3281          * without having to start a new transaction if it already exists.
3282          *
3283          * Atomic sections are more strict than transactions. With transactions,
3284          * attempting to begin a new transaction when one is already running results
3285          * in MediaWiki issuing a brief warning and doing an implicit commit. All
3286          * atomic levels *must* be explicitly closed using DatabaseBase::endAtomic(),
3287          * and any database transactions cannot be began or committed until all atomic
3288          * levels are closed. There is no such thing as implicitly opening or closing
3289          * an atomic section.
3290          *
3291          * @since 1.23
3292          * @param string $fname
3293          * @throws DBError
3294          */
3295         final public function startAtomic( $fname = __METHOD__ ) {
3296                 if ( !$this->mTrxLevel ) {
3297                         $this->begin( $fname );
3298                         $this->mTrxAutomatic = true;
3299                         $this->mTrxAutomaticAtomic = true;
3300                 }
3301
3302                 $this->mTrxAtomicLevels->push( $fname );
3303         }
3304
3305         /**
3306          * Ends an atomic section of SQL statements
3307          *
3308          * Ends the next section of atomic SQL statements and commits the transaction
3309          * if necessary.
3310          *
3311          * @since 1.23
3312          * @see DatabaseBase::startAtomic
3313          * @param string $fname
3314          * @throws DBError
3315          */
3316         final public function endAtomic( $fname = __METHOD__ ) {
3317                 if ( !$this->mTrxLevel ) {
3318                         throw new DBUnexpectedError( $this, 'No atomic transaction is open.' );
3319                 }
3320                 if ( $this->mTrxAtomicLevels->isEmpty() ||
3321                         $this->mTrxAtomicLevels->pop() !== $fname
3322                 ) {
3323                         throw new DBUnexpectedError( $this, 'Invalid atomic section ended.' );
3324                 }
3325
3326                 if ( $this->mTrxAtomicLevels->isEmpty() && $this->mTrxAutomaticAtomic ) {
3327                         $this->commit( $fname, 'flush' );
3328                 }
3329         }
3330
3331         /**
3332          * Begin a transaction. If a transaction is already in progress,
3333          * that transaction will be committed before the new transaction is started.
3334          *
3335          * Note that when the DBO_TRX flag is set (which is usually the case for web
3336          * requests, but not for maintenance scripts), any previous database query
3337          * will have started a transaction automatically.
3338          *
3339          * Nesting of transactions is not supported. Attempts to nest transactions
3340          * will cause a warning, unless the current transaction was started
3341          * automatically because of the DBO_TRX flag.
3342          *
3343          * @param $fname string
3344          * @throws DBError
3345          */
3346         final public function begin( $fname = __METHOD__ ) {
3347                 global $wgDebugDBTransactions;
3348
3349                 if ( $this->mTrxLevel ) { // implicit commit
3350                         if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3351                                 // If the current transaction was an automatic atomic one, then we definitely have
3352                                 // a problem. Same if there is any unclosed atomic level.
3353                                 throw new DBUnexpectedError( $this,
3354                                         "Attempted to start explicit transaction when atomic levels are still open."
3355                                 );
3356                         } elseif ( !$this->mTrxAutomatic ) {
3357                                 // We want to warn about inadvertently nested begin/commit pairs, but not about
3358                                 // auto-committing implicit transactions that were started by query() via DBO_TRX
3359                                 $msg = "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
3360                                         " performing implicit commit!";
3361                                 wfWarn( $msg );
3362                                 wfLogDBError( $msg );
3363                         } else {
3364                                 // if the transaction was automatic and has done write operations,
3365                                 // log it if $wgDebugDBTransactions is enabled.
3366                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
3367                                         wfDebug( "$fname: Automatic transaction with writes in progress" .
3368                                                 " (from {$this->mTrxFname}), performing implicit commit!\n"
3369                                         );
3370                                 }
3371                         }
3372
3373                         $this->runOnTransactionPreCommitCallbacks();
3374                         $this->doCommit( $fname );
3375                         if ( $this->mTrxDoneWrites ) {
3376                                 Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3377                         }
3378                         $this->runOnTransactionIdleCallbacks();
3379                 }
3380
3381                 $this->doBegin( $fname );
3382                 $this->mTrxFname = $fname;
3383                 $this->mTrxDoneWrites = false;
3384                 $this->mTrxAutomatic = false;
3385                 $this->mTrxAutomaticAtomic = false;
3386                 $this->mTrxAtomicLevels = new SplStack;
3387                 $this->mTrxIdleCallbacks = array();
3388                 $this->mTrxPreCommitCallbacks = array();
3389         }
3390
3391         /**
3392          * Issues the BEGIN command to the database server.
3393          *
3394          * @see DatabaseBase::begin()
3395          * @param type $fname
3396          */
3397         protected function doBegin( $fname ) {
3398                 $this->query( 'BEGIN', $fname );
3399                 $this->mTrxLevel = 1;
3400         }
3401
3402         /**
3403          * Commits a transaction previously started using begin().
3404          * If no transaction is in progress, a warning is issued.
3405          *
3406          * Nesting of transactions is not supported.
3407          *
3408          * @param $fname string
3409          * @param string $flush Flush flag, set to 'flush' to disable warnings about
3410          *   explicitly committing implicit transactions, or calling commit when no
3411          *   transaction is in progress. This will silently break any ongoing
3412          *   explicit transaction. Only set the flush flag if you are sure that it
3413          *   is safe to ignore these warnings in your context.
3414          */
3415         final public function commit( $fname = __METHOD__, $flush = '' ) {
3416                 if ( !$this->mTrxAtomicLevels->isEmpty() ) {
3417                         // There are still atomic sections open. This cannot be ignored
3418                         throw new DBUnexpectedError(
3419                                 $this,
3420                                 "Attempted to commit transaction while atomic sections are still open"
3421                         );
3422                 }
3423
3424                 if ( $flush != 'flush' ) {
3425                         if ( !$this->mTrxLevel ) {
3426                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
3427                         } elseif ( $this->mTrxAutomatic ) {
3428                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
3429                         }
3430                 } else {
3431                         if ( !$this->mTrxLevel ) {
3432                                 return; // nothing to do
3433                         } elseif ( !$this->mTrxAutomatic ) {
3434                                 wfWarn( "$fname: Flushing an explicit transaction, getting out of sync!" );
3435                         }
3436                 }
3437
3438                 $this->runOnTransactionPreCommitCallbacks();
3439                 $this->doCommit( $fname );
3440                 if ( $this->mTrxDoneWrites ) {
3441                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3442                 }
3443                 $this->runOnTransactionIdleCallbacks();
3444         }
3445
3446         /**
3447          * Issues the COMMIT command to the database server.
3448          *
3449          * @see DatabaseBase::commit()
3450          * @param type $fname
3451          */
3452         protected function doCommit( $fname ) {
3453                 if ( $this->mTrxLevel ) {
3454                         $this->query( 'COMMIT', $fname );
3455                         $this->mTrxLevel = 0;
3456                 }
3457         }
3458
3459         /**
3460          * Rollback a transaction previously started using begin().
3461          * If no transaction is in progress, a warning is issued.
3462          *
3463          * No-op on non-transactional databases.
3464          *
3465          * @param $fname string
3466          */
3467         final public function rollback( $fname = __METHOD__ ) {
3468                 if ( !$this->mTrxLevel ) {
3469                         wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3470                 }
3471                 $this->doRollback( $fname );
3472                 $this->mTrxIdleCallbacks = array(); // cancel
3473                 $this->mTrxPreCommitCallbacks = array(); // cancel
3474                 $this->mTrxAtomicLevels = new SplStack;
3475                 if ( $this->mTrxDoneWrites ) {
3476                         Profiler::instance()->transactionWritingOut( $this->mServer, $this->mDBname );
3477                 }
3478         }
3479
3480         /**
3481          * Issues the ROLLBACK command to the database server.
3482          *
3483          * @see DatabaseBase::rollback()
3484          * @param type $fname
3485          */
3486         protected function doRollback( $fname ) {
3487                 if ( $this->mTrxLevel ) {
3488                         $this->query( 'ROLLBACK', $fname, true );
3489                         $this->mTrxLevel = 0;
3490                 }
3491         }
3492
3493         /**
3494          * Creates a new table with structure copied from existing table
3495          * Note that unlike most database abstraction functions, this function does not
3496          * automatically append database prefix, because it works at a lower
3497          * abstraction level.
3498          * The table names passed to this function shall not be quoted (this
3499          * function calls addIdentifierQuotes when needed).
3500          *
3501          * @param string $oldName name of table whose structure should be copied
3502          * @param string $newName name of table to be created
3503          * @param $temporary Boolean: whether the new table should be temporary
3504          * @param string $fname calling function name
3505          * @throws MWException
3506          * @return Boolean: true if operation was successful
3507          */
3508         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3509                 $fname = __METHOD__
3510         ) {
3511                 throw new MWException(
3512                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3513         }
3514
3515         /**
3516          * List all tables on the database
3517          *
3518          * @param string $prefix Only show tables with this prefix, e.g. mw_
3519          * @param string $fname calling function name
3520          * @throws MWException
3521          */
3522         function listTables( $prefix = null, $fname = __METHOD__ ) {
3523                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3524         }
3525
3526         /**
3527          * Reset the views process cache set by listViews()
3528          * @since 1.22
3529          */
3530         final public function clearViewsCache() {
3531                 $this->allViews = null;
3532         }
3533
3534         /**
3535          * Lists all the VIEWs in the database
3536          *
3537          * For caching purposes the list of all views should be stored in
3538          * $this->allViews. The process cache can be cleared with clearViewsCache()
3539          *
3540          * @param string $prefix Only show VIEWs with this prefix, eg. unit_test_
3541          * @param string $fname Name of calling function
3542          * @throws MWException
3543          * @since 1.22
3544          */
3545         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3546                 throw new MWException( 'DatabaseBase::listViews is not implemented in descendant class' );
3547         }
3548
3549         /**
3550          * Differentiates between a TABLE and a VIEW
3551          *
3552          * @param $name string: Name of the database-structure to test.
3553          * @throws MWException
3554          * @since 1.22
3555          */
3556         public function isView( $name ) {
3557                 throw new MWException( 'DatabaseBase::isView is not implemented in descendant class' );
3558         }
3559
3560         /**
3561          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3562          * to the format used for inserting into timestamp fields in this DBMS.
3563          *
3564          * The result is unquoted, and needs to be passed through addQuotes()
3565          * before it can be included in raw SQL.
3566          *
3567          * @param $ts string|int
3568          *
3569          * @return string
3570          */
3571         public function timestamp( $ts = 0 ) {
3572                 return wfTimestamp( TS_MW, $ts );
3573         }
3574
3575         /**
3576          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3577          * to the format used for inserting into timestamp fields in this DBMS. If
3578          * NULL is input, it is passed through, allowing NULL values to be inserted
3579          * into timestamp fields.
3580          *
3581          * The result is unquoted, and needs to be passed through addQuotes()
3582          * before it can be included in raw SQL.
3583          *
3584          * @param $ts string|int
3585          *
3586          * @return string
3587          */
3588         public function timestampOrNull( $ts = null ) {
3589                 if ( is_null( $ts ) ) {
3590                         return null;
3591                 } else {
3592                         return $this->timestamp( $ts );
3593                 }
3594         }
3595
3596         /**
3597          * Take the result from a query, and wrap it in a ResultWrapper if
3598          * necessary. Boolean values are passed through as is, to indicate success
3599          * of write queries or failure.
3600          *
3601          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3602          * resource, and it was necessary to call this function to convert it to
3603          * a wrapper. Nowadays, raw database objects are never exposed to external
3604          * callers, so this is unnecessary in external code. For compatibility with
3605          * old code, ResultWrapper objects are passed through unaltered.
3606          *
3607          * @param $result bool|ResultWrapper
3608          *
3609          * @return bool|ResultWrapper
3610          */
3611         public function resultObject( $result ) {
3612                 if ( empty( $result ) ) {
3613                         return false;
3614                 } elseif ( $result instanceof ResultWrapper ) {
3615                         return $result;
3616                 } elseif ( $result === true ) {
3617                         // Successful write query
3618                         return $result;
3619                 } else {
3620                         return new ResultWrapper( $this, $result );
3621                 }
3622         }
3623
3624         /**
3625          * Ping the server and try to reconnect if it there is no connection
3626          *
3627          * @return bool Success or failure
3628          */
3629         public function ping() {
3630                 # Stub.  Not essential to override.
3631                 return true;
3632         }
3633
3634         /**
3635          * Get slave lag. Currently supported only by MySQL.
3636          *
3637          * Note that this function will generate a fatal error on many
3638          * installations. Most callers should use LoadBalancer::safeGetLag()
3639          * instead.
3640          *
3641          * @return int Database replication lag in seconds
3642          */
3643         public function getLag() {
3644                 return intval( $this->mFakeSlaveLag );
3645         }
3646
3647         /**
3648          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3649          *
3650          * @return int
3651          */
3652         function maxListLen() {
3653                 return 0;
3654         }
3655
3656         /**
3657          * Some DBMSs have a special format for inserting into blob fields, they
3658          * don't allow simple quoted strings to be inserted. To insert into such
3659          * a field, pass the data through this function before passing it to
3660          * DatabaseBase::insert().
3661          * @param $b string
3662          * @return string
3663          */
3664         public function encodeBlob( $b ) {
3665                 return $b;
3666         }
3667
3668         /**
3669          * Some DBMSs return a special placeholder object representing blob fields
3670          * in result objects. Pass the object through this function to return the
3671          * original string.
3672          * @param $b string
3673          * @return string
3674          */
3675         public function decodeBlob( $b ) {
3676                 return $b;
3677         }
3678
3679         /**
3680          * Override database's default behavior. $options include:
3681          *     'connTimeout' : Set the connection timeout value in seconds.
3682          *                     May be useful for very long batch queries such as
3683          *                     full-wiki dumps, where a single query reads out over
3684          *                     hours or days.
3685          *
3686          * @param $options Array
3687          * @return void
3688          */
3689         public function setSessionOptions( array $options ) {
3690         }
3691
3692         /**
3693          * Read and execute SQL commands from a file.
3694          *
3695          * Returns true on success, error string or exception on failure (depending
3696          * on object's error ignore settings).
3697          *
3698          * @param string $filename File name to open
3699          * @param bool|callable $lineCallback Optional function called before reading each line
3700          * @param bool|callable $resultCallback Optional function called for each MySQL result
3701          * @param bool|string $fname Calling function name or false if name should be
3702          *   generated dynamically using $filename
3703          * @param bool|callable $inputCallback Callback: Optional function called
3704          *   for each complete line sent
3705          * @throws MWException
3706          * @throws Exception|MWException
3707          * @return bool|string
3708          */
3709         public function sourceFile(
3710                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3711         ) {
3712                 wfSuppressWarnings();
3713                 $fp = fopen( $filename, 'r' );
3714                 wfRestoreWarnings();
3715
3716                 if ( false === $fp ) {
3717                         throw new MWException( "Could not open \"{$filename}\".\n" );
3718                 }
3719
3720                 if ( !$fname ) {
3721                         $fname = __METHOD__ . "( $filename )";
3722                 }
3723
3724                 try {
3725                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3726                 } catch ( MWException $e ) {
3727                         fclose( $fp );
3728                         throw $e;
3729                 }
3730
3731                 fclose( $fp );
3732
3733                 return $error;
3734         }
3735
3736         /**
3737          * Get the full path of a patch file. Originally based on archive()
3738          * from updaters.inc. Keep in mind this always returns a patch, as
3739          * it fails back to MySQL if no DB-specific patch can be found
3740          *
3741          * @param string $patch The name of the patch, like patch-something.sql
3742          * @return String Full path to patch file
3743          */
3744         public function patchPath( $patch ) {
3745                 global $IP;
3746
3747                 $dbType = $this->getType();
3748                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3749                         return "$IP/maintenance/$dbType/archives/$patch";
3750                 } else {
3751                         return "$IP/maintenance/archives/$patch";
3752                 }
3753         }
3754
3755         /**
3756          * Set variables to be used in sourceFile/sourceStream, in preference to the
3757          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3758          * all. If it's set to false, $GLOBALS will be used.
3759          *
3760          * @param bool|array $vars mapping variable name to value.
3761          */
3762         public function setSchemaVars( $vars ) {
3763                 $this->mSchemaVars = $vars;
3764         }
3765
3766         /**
3767          * Read and execute commands from an open file handle.
3768          *
3769          * Returns true on success, error string or exception on failure (depending
3770          * on object's error ignore settings).
3771          *
3772          * @param $fp Resource: File handle
3773          * @param $lineCallback Callback: Optional function called before reading each query
3774          * @param $resultCallback Callback: Optional function called for each MySQL result
3775          * @param string $fname Calling function name
3776          * @param $inputCallback Callback: Optional function called for each complete query sent
3777          * @return bool|string
3778          */
3779         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3780                 $fname = __METHOD__, $inputCallback = false
3781         ) {
3782                 $cmd = '';
3783
3784                 while ( !feof( $fp ) ) {
3785                         if ( $lineCallback ) {
3786                                 call_user_func( $lineCallback );
3787                         }
3788
3789                         $line = trim( fgets( $fp ) );
3790
3791                         if ( $line == '' ) {
3792                                 continue;
3793                         }
3794
3795                         if ( '-' == $line[0] && '-' == $line[1] ) {
3796                                 continue;
3797                         }
3798
3799                         if ( $cmd != '' ) {
3800                                 $cmd .= ' ';
3801                         }
3802
3803                         $done = $this->streamStatementEnd( $cmd, $line );
3804
3805                         $cmd .= "$line\n";
3806
3807                         if ( $done || feof( $fp ) ) {
3808                                 $cmd = $this->replaceVars( $cmd );
3809
3810                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3811                                         $res = $this->query( $cmd, $fname );
3812
3813                                         if ( $resultCallback ) {
3814                                                 call_user_func( $resultCallback, $res, $this );
3815                                         }
3816
3817                                         if ( false === $res ) {
3818                                                 $err = $this->lastError();
3819
3820                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3821                                         }
3822                                 }
3823                                 $cmd = '';
3824                         }
3825                 }
3826
3827                 return true;
3828         }
3829
3830         /**
3831          * Called by sourceStream() to check if we've reached a statement end
3832          *
3833          * @param string $sql SQL assembled so far
3834          * @param string $newLine New line about to be added to $sql
3835          * @return Bool Whether $newLine contains end of the statement
3836          */
3837         public function streamStatementEnd( &$sql, &$newLine ) {
3838                 if ( $this->delimiter ) {
3839                         $prev = $newLine;
3840                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3841                         if ( $newLine != $prev ) {
3842                                 return true;
3843                         }
3844                 }
3845
3846                 return false;
3847         }
3848
3849         /**
3850          * Database independent variable replacement. Replaces a set of variables
3851          * in an SQL statement with their contents as given by $this->getSchemaVars().
3852          *
3853          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3854          *
3855          * - '{$var}' should be used for text and is passed through the database's
3856          *   addQuotes method.
3857          * - `{$var}` should be used for identifiers (eg: table and database names),
3858          *   it is passed through the database's addIdentifierQuotes method which
3859          *   can be overridden if the database uses something other than backticks.
3860          * - / *$var* / is just encoded, besides traditional table prefix and
3861          *   table options its use should be avoided.
3862          *
3863          * @param string $ins SQL statement to replace variables in
3864          * @return String The new SQL statement with variables replaced
3865          */
3866         protected function replaceSchemaVars( $ins ) {
3867                 $vars = $this->getSchemaVars();
3868                 foreach ( $vars as $var => $value ) {
3869                         // replace '{$var}'
3870                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3871                         // replace `{$var}`
3872                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3873                         // replace /*$var*/
3874                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ), $ins );
3875                 }
3876
3877                 return $ins;
3878         }
3879
3880         /**
3881          * Replace variables in sourced SQL
3882          *
3883          * @param $ins string
3884          *
3885          * @return string
3886          */
3887         protected function replaceVars( $ins ) {
3888                 $ins = $this->replaceSchemaVars( $ins );
3889
3890                 // Table prefixes
3891                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3892                         array( $this, 'tableNameCallback' ), $ins );
3893
3894                 // Index names
3895                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3896                         array( $this, 'indexNameCallback' ), $ins );
3897
3898                 return $ins;
3899         }
3900
3901         /**
3902          * Get schema variables. If none have been set via setSchemaVars(), then
3903          * use some defaults from the current object.
3904          *
3905          * @return array
3906          */
3907         protected function getSchemaVars() {
3908                 if ( $this->mSchemaVars ) {
3909                         return $this->mSchemaVars;
3910                 } else {
3911                         return $this->getDefaultSchemaVars();
3912                 }
3913         }
3914
3915         /**
3916          * Get schema variables to use if none have been set via setSchemaVars().
3917          *
3918          * Override this in derived classes to provide variables for tables.sql
3919          * and SQL patch files.
3920          *
3921          * @return array
3922          */
3923         protected function getDefaultSchemaVars() {
3924                 return array();
3925         }
3926
3927         /**
3928          * Table name callback
3929          *
3930          * @param $matches array
3931          *
3932          * @return string
3933          */
3934         protected function tableNameCallback( $matches ) {
3935                 return $this->tableName( $matches[1] );
3936         }
3937
3938         /**
3939          * Index name callback
3940          *
3941          * @param $matches array
3942          *
3943          * @return string
3944          */
3945         protected function indexNameCallback( $matches ) {
3946                 return $this->indexName( $matches[1] );
3947         }
3948
3949         /**
3950          * Check to see if a named lock is available. This is non-blocking.
3951          *
3952          * @param string $lockName name of lock to poll
3953          * @param string $method name of method calling us
3954          * @return Boolean
3955          * @since 1.20
3956          */
3957         public function lockIsFree( $lockName, $method ) {
3958                 return true;
3959         }
3960
3961         /**
3962          * Acquire a named lock
3963          *
3964          * Abstracted from Filestore::lock() so child classes can implement for
3965          * their own needs.
3966          *
3967          * @param string $lockName name of lock to aquire
3968          * @param string $method name of method calling us
3969          * @param $timeout Integer: timeout
3970          * @return Boolean
3971          */
3972         public function lock( $lockName, $method, $timeout = 5 ) {
3973                 return true;
3974         }
3975
3976         /**
3977          * Release a lock.
3978          *
3979          * @param string $lockName Name of lock to release
3980          * @param string $method Name of method calling us
3981          *
3982          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3983          * by this thread (in which case the lock is not released), and NULL if the named
3984          * lock did not exist
3985          */
3986         public function unlock( $lockName, $method ) {
3987                 return true;
3988         }
3989
3990         /**
3991          * Lock specific tables
3992          *
3993          * @param array $read of tables to lock for read access
3994          * @param array $write of tables to lock for write access
3995          * @param string $method name of caller
3996          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
3997          *
3998          * @return bool
3999          */
4000         public function lockTables( $read, $write, $method, $lowPriority = true ) {
4001                 return true;
4002         }
4003
4004         /**
4005          * Unlock specific tables
4006          *
4007          * @param string $method the caller
4008          *
4009          * @return bool
4010          */
4011         public function unlockTables( $method ) {
4012                 return true;
4013         }
4014
4015         /**
4016          * Delete a table
4017          * @param $tableName string
4018          * @param $fName string
4019          * @return bool|ResultWrapper
4020          * @since 1.18
4021          */
4022         public function dropTable( $tableName, $fName = __METHOD__ ) {
4023                 if ( !$this->tableExists( $tableName, $fName ) ) {
4024                         return false;
4025                 }
4026                 $sql = "DROP TABLE " . $this->tableName( $tableName );
4027                 if ( $this->cascadingDeletes() ) {
4028                         $sql .= " CASCADE";
4029                 }
4030
4031                 return $this->query( $sql, $fName );
4032         }
4033
4034         /**
4035          * Get search engine class. All subclasses of this need to implement this
4036          * if they wish to use searching.
4037          *
4038          * @return String
4039          */
4040         public function getSearchEngine() {
4041                 return 'SearchEngineDummy';
4042         }
4043
4044         /**
4045          * Find out when 'infinity' is. Most DBMSes support this. This is a special
4046          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
4047          * because "i" sorts after all numbers.
4048          *
4049          * @return String
4050          */
4051         public function getInfinity() {
4052                 return 'infinity';
4053         }
4054
4055         /**
4056          * Encode an expiry time into the DBMS dependent format
4057          *
4058          * @param string $expiry timestamp for expiry, or the 'infinity' string
4059          * @return String
4060          */
4061         public function encodeExpiry( $expiry ) {
4062                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4063                         ? $this->getInfinity()
4064                         : $this->timestamp( $expiry );
4065         }
4066
4067         /**
4068          * Decode an expiry time into a DBMS independent format
4069          *
4070          * @param string $expiry DB timestamp field value for expiry
4071          * @param $format integer: TS_* constant, defaults to TS_MW
4072          * @return String
4073          */
4074         public function decodeExpiry( $expiry, $format = TS_MW ) {
4075                 return ( $expiry == '' || $expiry == $this->getInfinity() )
4076                         ? 'infinity'
4077                         : wfTimestamp( $format, $expiry );
4078         }
4079
4080         /**
4081          * Allow or deny "big selects" for this session only. This is done by setting
4082          * the sql_big_selects session variable.
4083          *
4084          * This is a MySQL-specific feature.
4085          *
4086          * @param $value Mixed: true for allow, false for deny, or "default" to
4087          *   restore the initial value
4088          */
4089         public function setBigSelects( $value = true ) {
4090                 // no-op
4091         }
4092
4093         /**
4094          * @since 1.19
4095          */
4096         public function __toString() {
4097                 return (string)$this->mConn;
4098         }
4099
4100         /**
4101          * Run a few simple sanity checks
4102          */
4103         public function __destruct() {
4104                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
4105                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
4106                 }
4107                 if ( count( $this->mTrxIdleCallbacks ) || count( $this->mTrxPreCommitCallbacks ) ) {
4108                         $callers = array();
4109                         foreach ( $this->mTrxIdleCallbacks as $callbackInfo ) {
4110                                 $callers[] = $callbackInfo[1];
4111                         }
4112                         $callers = implode( ', ', $callers );
4113                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
4114                 }
4115         }
4116 }