includes/db/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * This file deals with database interface functions
   6  * and query specifics/optimisations.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Database
  25  */
  26
  27 /** Number of times to re-try an operation in case of deadlock */
  28 define( 'DEADLOCK_TRIES', 4 );
  29 /** Minimum time to wait before retry, in microseconds */
  30 define( 'DEADLOCK_DELAY_MIN', 500000 );
  31 /** Maximum time to wait before retry */
  32 define( 'DEADLOCK_DELAY_MAX', 1500000 );
  33
  34 /**
  35  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  36  * following must be implemented to support MediaWiki
  37  *
  38  * @file
  39  * @ingroup Database
  40  */
  41 interface DatabaseType {
  42         /**
  43          * Get the type of the DBMS, as it appears in $wgDBtype.
  44          *
  45          * @return string
  46          */
  47         function getType();
  48
  49         /**
  50          * Open a connection to the database. Usually aborts on failure
  51          *
  52          * @param $server String: database server host
  53          * @param $user String: database user name
  54          * @param $password String: database user password
  55          * @param $dbName String: database name
  56          * @return bool
  57          * @throws DBConnectionError
  58          */
  59         function open( $server, $user, $password, $dbName );
  60
  61         /**
  62          * Fetch the next row from the given result object, in object form.
  63          * Fields can be retrieved with $row->fieldname, with fields acting like
  64          * member variables.
  65          *
  66          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  67          * @return Row object
  68          * @throws DBUnexpectedError Thrown if the database returns an error
  69          */
  70         function fetchObject( $res );
  71
  72         /**
  73          * Fetch the next row from the given result object, in associative array
  74          * form.  Fields are retrieved with $row['fieldname'].
  75          *
  76          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  77          * @return Row object
  78          * @throws DBUnexpectedError Thrown if the database returns an error
  79          */
  80         function fetchRow( $res );
  81
  82         /**
  83          * Get the number of rows in a result object
  84          *
  85          * @param $res Mixed: A SQL result
  86          * @return int
  87          */
  88         function numRows( $res );
  89
  90         /**
  91          * Get the number of fields in a result object
  92          * @see http://www.php.net/mysql_num_fields
  93          *
  94          * @param $res Mixed: A SQL result
  95          * @return int
  96          */
  97         function numFields( $res );
  98
  99         /**
 100          * Get a field name in a result object
 101          * @see http://www.php.net/mysql_field_name
 102          *
 103          * @param $res Mixed: A SQL result
 104          * @param $n Integer
 105          * @return string
 106          */
 107         function fieldName( $res, $n );
 108
 109         /**
 110          * Get the inserted value of an auto-increment row
 111          *
 112          * The value inserted should be fetched from nextSequenceValue()
 113          *
 114          * Example:
 115          * $id = $dbw->nextSequenceValue('page_page_id_seq');
 116          * $dbw->insert('page',array('page_id' => $id));
 117          * $id = $dbw->insertId();
 118          *
 119          * @return int
 120          */
 121         function insertId();
 122
 123         /**
 124          * Change the position of the cursor in a result object
 125          * @see http://www.php.net/mysql_data_seek
 126          *
 127          * @param $res Mixed: A SQL result
 128          * @param $row Mixed: Either MySQL row or ResultWrapper
 129          */
 130         function dataSeek( $res, $row );
 131
 132         /**
 133          * Get the last error number
 134          * @see http://www.php.net/mysql_errno
 135          *
 136          * @return int
 137          */
 138         function lastErrno();
 139
 140         /**
 141          * Get a description of the last error
 142          * @see http://www.php.net/mysql_error
 143          *
 144          * @return string
 145          */
 146         function lastError();
 147
 148         /**
 149          * mysql_fetch_field() wrapper
 150          * Returns false if the field doesn't exist
 151          *
 152          * @param $table string: table name
 153          * @param $field string: field name
 154          *
 155          * @return Field
 156          */
 157         function fieldInfo( $table, $field );
 158
 159         /**
 160          * Get information about an index into an object
 161          * @param $table string: Table name
 162          * @param $index string: Index name
 163          * @param $fname string: Calling function name
 164          * @return Mixed: Database-specific index description class or false if the index does not exist
 165          */
 166         function indexInfo( $table, $index, $fname = 'Database::indexInfo' );
 167
 168         /**
 169          * Get the number of rows affected by the last write query
 170          * @see http://www.php.net/mysql_affected_rows
 171          *
 172          * @return int
 173          */
 174         function affectedRows();
 175
 176         /**
 177          * Wrapper for addslashes()
 178          *
 179          * @param $s string: to be slashed.
 180          * @return string: slashed string.
 181          */
 182         function strencode( $s );
 183
 184         /**
 185          * Returns a wikitext link to the DB's website, e.g.,
 186          *     return "[http://www.mysql.com/ MySQL]";
 187          * Should at least contain plain text, if for some reason
 188          * your database has no website.
 189          *
 190          * @return string: wikitext of a link to the server software's web site
 191          */
 192         static function getSoftwareLink();
 193
 194         /**
 195          * A string describing the current software version, like from
 196          * mysql_get_server_info().
 197          *
 198          * @return string: Version information from the database server.
 199          */
 200         function getServerVersion();
 201
 202         /**
 203          * A string describing the current software version, and possibly
 204          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 205          * Use getServerVersion() to get machine-friendly information.
 206          *
 207          * @return string: Version information from the database server
 208          */
 209         function getServerInfo();
 210 }
 211
 212 /**
 213  * Database abstraction object
 214  * @ingroup Database
 215  */
 216 abstract class DatabaseBase implements DatabaseType {
 217
 218 # ------------------------------------------------------------------------------
 219 # Variables
 220 # ------------------------------------------------------------------------------
 221
 222         protected $mLastQuery = '';
 223         protected $mDoneWrites = false;
 224         protected $mPHPError = false;
 225
 226         protected $mServer, $mUser, $mPassword, $mDBname;
 227
 228         protected $mConn = null;
 229         protected $mOpened = false;
 230
 231         /**
 232          * @since 1.20
 233          * @var array of callable
 234          */
 235         protected $trxIdleCallbacks = array();
 236
 237         protected $mTablePrefix;
 238         protected $mFlags;
 239         protected $mTrxLevel = 0;
 240         protected $mErrorCount = 0;
 241         protected $mLBInfo = array();
 242         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 243         protected $mDefaultBigSelects = null;
 244         protected $mSchemaVars = false;
 245
 246         protected $preparedArgs;
 247
 248         protected $htmlErrors;
 249
 250         protected $delimiter = ';';
 251
 252         /**
 253          * Remembers the function name given for starting the most recent transaction via begin().
 254          * Used to provide additional context for error reporting.
 255          *
 256          * @var String
 257          * @see DatabaseBase::mTrxLevel
 258          */
 259         private $mTrxFname = null;
 260
 261         /**
 262          * Record if possible write queries were done in the last transaction started
 263          *
 264          * @var Bool
 265          * @see DatabaseBase::mTrxLevel
 266          */
 267         private $mTrxDoneWrites = false;
 268
 269         /**
 270          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 271          *
 272          * @var Bool
 273          * @see DatabaseBase::mTrxLevel
 274          */
 275         private $mTrxAutomatic = false;
 276
 277 # ------------------------------------------------------------------------------
 278 # Accessors
 279 # ------------------------------------------------------------------------------
 280         # These optionally set a variable and return the previous state
 281
 282         /**
 283          * A string describing the current software version, and possibly
 284          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 285          * Use getServerVersion() to get machine-friendly information.
 286          *
 287          * @return string: Version information from the database server
 288          */
 289         public function getServerInfo() {
 290                 return $this->getServerVersion();
 291         }
 292
 293         /**
 294          * Boolean, controls output of large amounts of debug information.
 295          * @param $debug bool|null
 296          *   - true to enable debugging
 297          *   - false to disable debugging
 298          *   - omitted or null to do nothing
 299          *
 300          * @return bool|null previous value of the flag
 301          */
 302         public function debug( $debug = null ) {
 303                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 304         }
 305
 306         /**
 307          * Turns buffering of SQL result sets on (true) or off (false). Default is
 308          * "on".
 309          *
 310          * Unbuffered queries are very troublesome in MySQL:
 311          *
 312          *   - If another query is executed while the first query is being read
 313          *     out, the first query is killed. This means you can't call normal
 314          *     MediaWiki functions while you are reading an unbuffered query result
 315          *     from a normal wfGetDB() connection.
 316          *
 317          *   - Unbuffered queries cause the MySQL server to use large amounts of
 318          *     memory and to hold broad locks which block other queries.
 319          *
 320          * If you want to limit client-side memory, it's almost always better to
 321          * split up queries into batches using a LIMIT clause than to switch off
 322          * buffering.
 323          *
 324          * @param $buffer null|bool
 325          *
 326          * @return null|bool The previous value of the flag
 327          */
 328         public function bufferResults( $buffer = null ) {
 329                 if ( is_null( $buffer ) ) {
 330                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 331                 } else {
 332                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 333                 }
 334         }
 335
 336         /**
 337          * Turns on (false) or off (true) the automatic generation and sending
 338          * of a "we're sorry, but there has been a database error" page on
 339          * database errors. Default is on (false). When turned off, the
 340          * code should use lastErrno() and lastError() to handle the
 341          * situation as appropriate.
 342          *
 343          * @param $ignoreErrors bool|null
 344          *
 345          * @return bool The previous value of the flag.
 346          */
 347         public function ignoreErrors( $ignoreErrors = null ) {
 348                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 349         }
 350
 351         /**
 352          * Gets or sets the current transaction level.
 353          *
 354          * Historically, transactions were allowed to be "nested". This is no
 355          * longer supported, so this function really only returns a boolean.
 356          *
 357          * @param $level int An integer (0 or 1), or omitted to leave it unchanged.
 358          * @return int The previous value
 359          */
 360         public function trxLevel( $level = null ) {
 361                 return wfSetVar( $this->mTrxLevel, $level );
 362         }
 363
 364         /**
 365          * Get/set the number of errors logged. Only useful when errors are ignored
 366          * @param $count int The count to set, or omitted to leave it unchanged.
 367          * @return int The error count
 368          */
 369         public function errorCount( $count = null ) {
 370                 return wfSetVar( $this->mErrorCount, $count );
 371         }
 372
 373         /**
 374          * Get/set the table prefix.
 375          * @param $prefix string The table prefix to set, or omitted to leave it unchanged.
 376          * @return string The previous table prefix.
 377          */
 378         public function tablePrefix( $prefix = null ) {
 379                 return wfSetVar( $this->mTablePrefix, $prefix );
 380         }
 381
 382         /**
 383          * Get properties passed down from the server info array of the load
 384          * balancer.
 385          *
 386          * @param $name string The entry of the info array to get, or null to get the
 387          *   whole array
 388          *
 389          * @return LoadBalancer|null
 390          */
 391         public function getLBInfo( $name = null ) {
 392                 if ( is_null( $name ) ) {
 393                         return $this->mLBInfo;
 394                 } else {
 395                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 396                                 return $this->mLBInfo[$name];
 397                         } else {
 398                                 return null;
 399                         }
 400                 }
 401         }
 402
 403         /**
 404          * Set the LB info array, or a member of it. If called with one parameter,
 405          * the LB info array is set to that parameter. If it is called with two
 406          * parameters, the member with the given name is set to the given value.
 407          *
 408          * @param $name
 409          * @param $value
 410          */
 411         public function setLBInfo( $name, $value = null ) {
 412                 if ( is_null( $value ) ) {
 413                         $this->mLBInfo = $name;
 414                 } else {
 415                         $this->mLBInfo[$name] = $value;
 416                 }
 417         }
 418
 419         /**
 420          * Set lag time in seconds for a fake slave
 421          *
 422          * @param $lag int
 423          */
 424         public function setFakeSlaveLag( $lag ) {
 425                 $this->mFakeSlaveLag = $lag;
 426         }
 427
 428         /**
 429          * Make this connection a fake master
 430          *
 431          * @param $enabled bool
 432          */
 433         public function setFakeMaster( $enabled = true ) {
 434                 $this->mFakeMaster = $enabled;
 435         }
 436
 437         /**
 438          * Returns true if this database supports (and uses) cascading deletes
 439          *
 440          * @return bool
 441          */
 442         public function cascadingDeletes() {
 443                 return false;
 444         }
 445
 446         /**
 447          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 448          *
 449          * @return bool
 450          */
 451         public function cleanupTriggers() {
 452                 return false;
 453         }
 454
 455         /**
 456          * Returns true if this database is strict about what can be put into an IP field.
 457          * Specifically, it uses a NULL value instead of an empty string.
 458          *
 459          * @return bool
 460          */
 461         public function strictIPs() {
 462                 return false;
 463         }
 464
 465         /**
 466          * Returns true if this database uses timestamps rather than integers
 467          *
 468          * @return bool
 469         */
 470         public function realTimestamps() {
 471                 return false;
 472         }
 473
 474         /**
 475          * Returns true if this database does an implicit sort when doing GROUP BY
 476          *
 477          * @return bool
 478          */
 479         public function implicitGroupby() {
 480                 return true;
 481         }
 482
 483         /**
 484          * Returns true if this database does an implicit order by when the column has an index
 485          * For example: SELECT page_title FROM page LIMIT 1
 486          *
 487          * @return bool
 488          */
 489         public function implicitOrderby() {
 490                 return true;
 491         }
 492
 493         /**
 494          * Returns true if this database can do a native search on IP columns
 495          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 496          *
 497          * @return bool
 498          */
 499         public function searchableIPs() {
 500                 return false;
 501         }
 502
 503         /**
 504          * Returns true if this database can use functional indexes
 505          *
 506          * @return bool
 507          */
 508         public function functionalIndexes() {
 509                 return false;
 510         }
 511
 512         /**
 513          * Return the last query that went through DatabaseBase::query()
 514          * @return String
 515          */
 516         public function lastQuery() {
 517                 return $this->mLastQuery;
 518         }
 519
 520         /**
 521          * Returns true if the connection may have been used for write queries.
 522          * Should return true if unsure.
 523          *
 524          * @return bool
 525          */
 526         public function doneWrites() {
 527                 return $this->mDoneWrites;
 528         }
 529
 530         /**
 531          * Is a connection to the database open?
 532          * @return Boolean
 533          */
 534         public function isOpen() {
 535                 return $this->mOpened;
 536         }
 537
 538         /**
 539          * Set a flag for this connection
 540          *
 541          * @param $flag Integer: DBO_* constants from Defines.php:
 542          *   - DBO_DEBUG: output some debug info (same as debug())
 543          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 544          *   - DBO_IGNORE: ignore errors (same as ignoreErrors())
 545          *   - DBO_TRX: automatically start transactions
 546          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 547          *       and removes it in command line mode
 548          *   - DBO_PERSISTENT: use persistant database connection
 549          */
 550         public function setFlag( $flag ) {
 551                 global $wgDebugDBTransactions;
 552                 $this->mFlags |= $flag;
 553                 if ( ( $flag & DBO_TRX) & $wgDebugDBTransactions ) {
 554                         wfDebug("Implicit transactions are now  disabled.\n");
 555                 }
 556         }
 557
 558         /**
 559          * Clear a flag for this connection
 560          *
 561          * @param $flag: same as setFlag()'s $flag param
 562          */
 563         public function clearFlag( $flag ) {
 564                 global $wgDebugDBTransactions;
 565                 $this->mFlags &= ~$flag;
 566                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 567                         wfDebug("Implicit transactions are now disabled.\n");
 568                 }
 569         }
 570
 571         /**
 572          * Returns a boolean whether the flag $flag is set for this connection
 573          *
 574          * @param $flag: same as setFlag()'s $flag param
 575          * @return Boolean
 576          */
 577         public function getFlag( $flag ) {
 578                 return !!( $this->mFlags & $flag );
 579         }
 580
 581         /**
 582          * General read-only accessor
 583          *
 584          * @param $name string
 585          *
 586          * @return string
 587          */
 588         public function getProperty( $name ) {
 589                 return $this->$name;
 590         }
 591
 592         /**
 593          * @return string
 594          */
 595         public function getWikiID() {
 596                 if ( $this->mTablePrefix ) {
 597                         return "{$this->mDBname}-{$this->mTablePrefix}";
 598                 } else {
 599                         return $this->mDBname;
 600                 }
 601         }
 602
 603         /**
 604          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 605          *
 606          * @return string
 607          */
 608         public function getSchemaPath() {
 609                 global $IP;
 610                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 611                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 612                 } else {
 613                         return "$IP/maintenance/tables.sql";
 614                 }
 615         }
 616
 617 # ------------------------------------------------------------------------------
 618 # Other functions
 619 # ------------------------------------------------------------------------------
 620
 621         /**
 622          * Constructor.
 623          * @param $server String: database server host
 624          * @param $user String: database user name
 625          * @param $password String: database user password
 626          * @param $dbName String: database name
 627          * @param $flags
 628          * @param $tablePrefix String: database table prefixes. By default use the prefix gave in LocalSettings.php
 629          */
 630         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 631                 $flags = 0, $tablePrefix = 'get from global'
 632         ) {
 633                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 634
 635                 $this->mFlags = $flags;
 636
 637                 if ( $this->mFlags & DBO_DEFAULT ) {
 638                         if ( $wgCommandLineMode ) {
 639                                 $this->mFlags &= ~DBO_TRX;
 640                                 if ( $wgDebugDBTransactions ) {
 641                                         wfDebug("Implicit transaction open disabled.\n");
 642                                 }
 643                         } else {
 644                                 $this->mFlags |= DBO_TRX;
 645                                 if ( $wgDebugDBTransactions ) {
 646                                         wfDebug("Implicit transaction open enabled.\n");
 647                                 }
 648                         }
 649                 }
 650
 651                 /** Get the default table prefix*/
 652                 if ( $tablePrefix == 'get from global' ) {
 653                         $this->mTablePrefix = $wgDBprefix;
 654                 } else {
 655                         $this->mTablePrefix = $tablePrefix;
 656                 }
 657
 658                 if ( $user ) {
 659                         $this->open( $server, $user, $password, $dbName );
 660                 }
 661         }
 662
 663         /**
 664          * Called by serialize. Throw an exception when DB connection is serialized.
 665          * This causes problems on some database engines because the connection is
 666          * not restored on unserialize.
 667          */
 668         public function __sleep() {
 669                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 670         }
 671
 672         /**
 673          * Given a DB type, construct the name of the appropriate child class of
 674          * DatabaseBase. This is designed to replace all of the manual stuff like:
 675          *      $class = 'Database' . ucfirst( strtolower( $type ) );
 676          * as well as validate against the canonical list of DB types we have
 677          *
 678          * This factory function is mostly useful for when you need to connect to a
 679          * database other than the MediaWiki default (such as for external auth,
 680          * an extension, et cetera). Do not use this to connect to the MediaWiki
 681          * database. Example uses in core:
 682          * @see LoadBalancer::reallyOpenConnection()
 683          * @see ExternalUser_MediaWiki::initFromCond()
 684          * @see ForeignDBRepo::getMasterDB()
 685          * @see WebInstaller_DBConnect::execute()
 686          *
 687          * @since 1.18
 688          *
 689          * @param $dbType String A possible DB type
 690          * @param $p Array An array of options to pass to the constructor.
 691          *    Valid options are: host, user, password, dbname, flags, tablePrefix
 692          * @return DatabaseBase subclass or null
 693          */
 694         public final static function factory( $dbType, $p = array() ) {
 695                 $canonicalDBTypes = array(
 696                         'mysql', 'postgres', 'sqlite', 'oracle', 'mssql', 'ibm_db2'
 697                 );
 698                 $dbType = strtolower( $dbType );
 699                 $class = 'Database' . ucfirst( $dbType );
 700
 701                 if( in_array( $dbType, $canonicalDBTypes ) || ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) ) {
 702                         return new $class(
 703                                 isset( $p['host'] ) ? $p['host'] : false,
 704                                 isset( $p['user'] ) ? $p['user'] : false,
 705                                 isset( $p['password'] ) ? $p['password'] : false,
 706                                 isset( $p['dbname'] ) ? $p['dbname'] : false,
 707                                 isset( $p['flags'] ) ? $p['flags'] : 0,
 708                                 isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global'
 709                         );
 710                 } else {
 711                         return null;
 712                 }
 713         }
 714
 715         protected function installErrorHandler() {
 716                 $this->mPHPError = false;
 717                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 718                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 719         }
 720
 721         /**
 722          * @return bool|string
 723          */
 724         protected function restoreErrorHandler() {
 725                 restore_error_handler();
 726                 if ( $this->htmlErrors !== false ) {
 727                         ini_set( 'html_errors', $this->htmlErrors );
 728                 }
 729                 if ( $this->mPHPError ) {
 730                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 731                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 732                         return $error;
 733                 } else {
 734                         return false;
 735                 }
 736         }
 737
 738         /**
 739          * @param $errno
 740          * @param $errstr
 741          */
 742         protected function connectionErrorHandler( $errno,  $errstr ) {
 743                 $this->mPHPError = $errstr;
 744         }
 745
 746         /**
 747          * Closes a database connection.
 748          * if it is open : commits any open transactions
 749          *
 750          * @return Bool operation success. true if already closed.
 751          */
 752         public function close() {
 753                 $this->mOpened = false;
 754                 if ( $this->mConn ) {
 755                         if ( $this->trxLevel() ) {
 756                                 if ( !$this->mTrxAutomatic ) {
 757                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 758                                                 " performing implicit commit before closing connection!" );
 759                                 }
 760
 761                                 $this->commit( __METHOD__, true );
 762                         }
 763
 764                         $ret = $this->closeConnection();
 765                         $this->mConn = false;
 766                         return $ret;
 767                 } else {
 768                         return true;
 769                 }
 770         }
 771
 772         /**
 773          * Closes underlying database connection
 774          * @since 1.20
 775          * @return bool: Whether connection was closed successfully
 776          */
 777         protected abstract function closeConnection();
 778
 779         /**
 780          * @param $error String: fallback error message, used if none is given by DB
 781          * @throws DBConnectionError
 782          */
 783         function reportConnectionError( $error = 'Unknown error' ) {
 784                 $myError = $this->lastError();
 785                 if ( $myError ) {
 786                         $error = $myError;
 787                 }
 788
 789                 # New method
 790                 throw new DBConnectionError( $this, $error );
 791         }
 792
 793         /**
 794          * The DBMS-dependent part of query()
 795          *
 796          * @param  $sql String: SQL query.
 797          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 798          */
 799         protected abstract function doQuery( $sql );
 800
 801         /**
 802          * Determine whether a query writes to the DB.
 803          * Should return true if unsure.
 804          *
 805          * @param $sql string
 806          *
 807          * @return bool
 808          */
 809         public function isWriteQuery( $sql ) {
 810                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 811         }
 812
 813         /**
 814          * Run an SQL query and return the result. Normally throws a DBQueryError
 815          * on failure. If errors are ignored, returns false instead.
 816          *
 817          * In new code, the query wrappers select(), insert(), update(), delete(),
 818          * etc. should be used where possible, since they give much better DBMS
 819          * independence and automatically quote or validate user input in a variety
 820          * of contexts. This function is generally only useful for queries which are
 821          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 822          * as CREATE TABLE.
 823          *
 824          * However, the query wrappers themselves should call this function.
 825          *
 826          * @param  $sql        String: SQL query
 827          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 828          *     comment (you can use __METHOD__ or add some extra info)
 829          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 830          *     maybe best to catch the exception instead?
 831          * @throws MWException
 832          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 833          *     for a successful read query, or false on failure if $tempIgnore set
 834          */
 835         public function query( $sql, $fname = '', $tempIgnore = false ) {
 836                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 837                 if ( !Profiler::instance()->isStub() ) {
 838                         # generalizeSQL will probably cut down the query to reasonable
 839                         # logging size most of the time. The substr is really just a sanity check.
 840
 841                         if ( $isMaster ) {
 842                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 843                                 $totalProf = 'DatabaseBase::query-master';
 844                         } else {
 845                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 846                                 $totalProf = 'DatabaseBase::query';
 847                         }
 848
 849                         wfProfileIn( $totalProf );
 850                         wfProfileIn( $queryProf );
 851                 }
 852
 853                 $this->mLastQuery = $sql;
 854                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 855                         # Set a flag indicating that writes have been done
 856                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 857                         $this->mDoneWrites = true;
 858                 }
 859
 860                 # Add a comment for easy SHOW PROCESSLIST interpretation
 861                 global $wgUser;
 862                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 863                         $userName = $wgUser->getName();
 864                         if ( mb_strlen( $userName ) > 15 ) {
 865                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 866                         }
 867                         $userName = str_replace( '/', '', $userName );
 868                 } else {
 869                         $userName = '';
 870                 }
 871                 $commentedSql = preg_replace( '/\s/', " /* $fname $userName */ ", $sql, 1 );
 872
 873                 # If DBO_TRX is set, start a transaction
 874                 if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
 875                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' )
 876                 {
 877                         # Avoid establishing transactions for SHOW and SET statements too -
 878                         # that would delay transaction initializations to once connection
 879                         # is really used by application
 880                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 881                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 882                                 global $wgDebugDBTransactions;
 883                                 if ( $wgDebugDBTransactions ) {
 884                                         wfDebug("Implicit transaction start.\n");
 885                                 }
 886                                 $this->begin( __METHOD__ . " ($fname)" );
 887                                 $this->mTrxAutomatic = true;
 888                         }
 889                 }
 890
 891                 # Keep track of whether the transaction has write queries pending
 892                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
 893                         $this->mTrxDoneWrites = true;
 894                 }
 895
 896                 if ( $this->debug() ) {
 897                         static $cnt = 0;
 898
 899                         $cnt++;
 900                         $sqlx = substr( $commentedSql, 0, 500 );
 901                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 902
 903                         $master = $isMaster ? 'master' : 'slave';
 904                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 905                 }
 906
 907                 if ( istainted( $sql ) & TC_MYSQL ) {
 908                         throw new MWException( 'Tainted query found' );
 909                 }
 910
 911                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 912
 913                 # Do the query and handle errors
 914                 $ret = $this->doQuery( $commentedSql );
 915
 916                 MWDebug::queryTime( $queryId );
 917
 918                 # Try reconnecting if the connection was lost
 919                 if ( false === $ret && $this->wasErrorReissuable() ) {
 920                         # Transaction is gone, like it or not
 921                         $this->mTrxLevel = 0;
 922                         $this->trxIdleCallbacks = array(); // cancel
 923                         wfDebug( "Connection lost, reconnecting...\n" );
 924
 925                         if ( $this->ping() ) {
 926                                 wfDebug( "Reconnected\n" );
 927                                 $sqlx = substr( $commentedSql, 0, 500 );
 928                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
 929                                 global $wgRequestTime;
 930                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
 931                                 if ( $elapsed < 300 ) {
 932                                         # Not a database error to lose a transaction after a minute or two
 933                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
 934                                 }
 935                                 $ret = $this->doQuery( $commentedSql );
 936                         } else {
 937                                 wfDebug( "Failed\n" );
 938                         }
 939                 }
 940
 941                 if ( false === $ret ) {
 942                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 943                 }
 944
 945                 if ( !Profiler::instance()->isStub() ) {
 946                         wfProfileOut( $queryProf );
 947                         wfProfileOut( $totalProf );
 948                 }
 949
 950                 return $this->resultObject( $ret );
 951         }
 952
 953         /**
 954          * Report a query error. Log the error, and if neither the object ignore
 955          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
 956          *
 957          * @param $error String
 958          * @param $errno Integer
 959          * @param $sql String
 960          * @param $fname String
 961          * @param $tempIgnore Boolean
 962          * @throws DBQueryError
 963          */
 964         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
 965                 # Ignore errors during error handling to avoid infinite recursion
 966                 $ignore = $this->ignoreErrors( true );
 967                 ++$this->mErrorCount;
 968
 969                 if ( $ignore || $tempIgnore ) {
 970                         wfDebug( "SQL ERROR (ignored): $error\n" );
 971                         $this->ignoreErrors( $ignore );
 972                 } else {
 973                         $sql1line = str_replace( "\n", "\\n", $sql );
 974                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
 975                         wfDebug( "SQL ERROR: " . $error . "\n" );
 976                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
 977                 }
 978         }
 979
 980         /**
 981          * Intended to be compatible with the PEAR::DB wrapper functions.
 982          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
 983          *
 984          * ? = scalar value, quoted as necessary
 985          * ! = raw SQL bit (a function for instance)
 986          * & = filename; reads the file and inserts as a blob
 987          *     (we don't use this though...)
 988          *
 989          * @param $sql string
 990          * @param $func string
 991          *
 992          * @return array
 993          */
 994         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
 995                 /* MySQL doesn't support prepared statements (yet), so just
 996                    pack up the query for reference. We'll manually replace
 997                    the bits later. */
 998                 return array( 'query' => $sql, 'func' => $func );
 999         }
1000
1001         /**
1002          * Free a prepared query, generated by prepare().
1003          * @param $prepared
1004          */
1005         protected function freePrepared( $prepared ) {
1006                 /* No-op by default */
1007         }
1008
1009         /**
1010          * Execute a prepared query with the various arguments
1011          * @param $prepared String: the prepared sql
1012          * @param $args Mixed: Either an array here, or put scalars as varargs
1013          *
1014          * @return ResultWrapper
1015          */
1016         public function execute( $prepared, $args = null ) {
1017                 if ( !is_array( $args ) ) {
1018                         # Pull the var args
1019                         $args = func_get_args();
1020                         array_shift( $args );
1021                 }
1022
1023                 $sql = $this->fillPrepared( $prepared['query'], $args );
1024
1025                 return $this->query( $sql, $prepared['func'] );
1026         }
1027
1028         /**
1029          * For faking prepared SQL statements on DBs that don't support it directly.
1030          *
1031          * @param $preparedQuery String: a 'preparable' SQL statement
1032          * @param $args Array of arguments to fill it with
1033          * @return string executable SQL
1034          */
1035         public function fillPrepared( $preparedQuery, $args ) {
1036                 reset( $args );
1037                 $this->preparedArgs =& $args;
1038
1039                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1040                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
1041         }
1042
1043         /**
1044          * preg_callback func for fillPrepared()
1045          * The arguments should be in $this->preparedArgs and must not be touched
1046          * while we're doing this.
1047          *
1048          * @param $matches Array
1049          * @throws DBUnexpectedError
1050          * @return String
1051          */
1052         protected function fillPreparedArg( $matches ) {
1053                 switch( $matches[1] ) {
1054                         case '\\?': return '?';
1055                         case '\\!': return '!';
1056                         case '\\&': return '&';
1057                 }
1058
1059                 list( /* $n */ , $arg ) = each( $this->preparedArgs );
1060
1061                 switch( $matches[1] ) {
1062                         case '?': return $this->addQuotes( $arg );
1063                         case '!': return $arg;
1064                         case '&':
1065                                 # return $this->addQuotes( file_get_contents( $arg ) );
1066                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1067                         default:
1068                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1069                 }
1070         }
1071
1072         /**
1073          * Free a result object returned by query() or select(). It's usually not
1074          * necessary to call this, just use unset() or let the variable holding
1075          * the result object go out of scope.
1076          *
1077          * @param $res Mixed: A SQL result
1078          */
1079         public function freeResult( $res ) {}
1080
1081         /**
1082          * A SELECT wrapper which returns a single field from a single result row.
1083          *
1084          * Usually throws a DBQueryError on failure. If errors are explicitly
1085          * ignored, returns false on failure.
1086          *
1087          * If no result rows are returned from the query, false is returned.
1088          *
1089          * @param $table string|array Table name. See DatabaseBase::select() for details.
1090          * @param $var string The field name to select. This must be a valid SQL
1091          *   fragment: do not use unvalidated user input.
1092          * @param $cond string|array The condition array. See DatabaseBase::select() for details.
1093          * @param $fname string The function name of the caller.
1094          * @param $options string|array The query options. See DatabaseBase::select() for details.
1095          *
1096          * @return bool|mixed The value from the field, or false on failure.
1097          */
1098         public function selectField( $table, $var, $cond = '', $fname = 'DatabaseBase::selectField',
1099                 $options = array() )
1100         {
1101                 if ( !is_array( $options ) ) {
1102                         $options = array( $options );
1103                 }
1104
1105                 $options['LIMIT'] = 1;
1106
1107                 $res = $this->select( $table, $var, $cond, $fname, $options );
1108
1109                 if ( $res === false || !$this->numRows( $res ) ) {
1110                         return false;
1111                 }
1112
1113                 $row = $this->fetchRow( $res );
1114
1115                 if ( $row !== false ) {
1116                         return reset( $row );
1117                 } else {
1118                         return false;
1119                 }
1120         }
1121
1122         /**
1123          * Returns an optional USE INDEX clause to go after the table, and a
1124          * string to go at the end of the query.
1125          *
1126          * @param $options Array: associative array of options to be turned into
1127          *              an SQL query, valid keys are listed in the function.
1128          * @return Array
1129          * @see DatabaseBase::select()
1130          */
1131         public function makeSelectOptions( $options ) {
1132                 $preLimitTail = $postLimitTail = '';
1133                 $startOpts = '';
1134
1135                 $noKeyOptions = array();
1136
1137                 foreach ( $options as $key => $option ) {
1138                         if ( is_numeric( $key ) ) {
1139                                 $noKeyOptions[$option] = true;
1140                         }
1141                 }
1142
1143                 if ( isset( $options['GROUP BY'] ) ) {
1144                         $gb = is_array( $options['GROUP BY'] )
1145                                 ? implode( ',', $options['GROUP BY'] )
1146                                 : $options['GROUP BY'];
1147                         $preLimitTail .= " GROUP BY {$gb}";
1148                 }
1149
1150                 if ( isset( $options['HAVING'] ) ) {
1151                         $having = is_array( $options['HAVING'] )
1152                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1153                                 : $options['HAVING'];
1154                         $preLimitTail .= " HAVING {$having}";
1155                 }
1156
1157                 if ( isset( $options['ORDER BY'] ) ) {
1158                         $ob = is_array( $options['ORDER BY'] )
1159                                 ? implode( ',', $options['ORDER BY'] )
1160                                 : $options['ORDER BY'];
1161                         $preLimitTail .= " ORDER BY {$ob}";
1162                 }
1163
1164                 // if (isset($options['LIMIT'])) {
1165                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1166                 //              isset($options['OFFSET']) ? $options['OFFSET']
1167                 //              : false);
1168                 // }
1169
1170                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1171                         $postLimitTail .= ' FOR UPDATE';
1172                 }
1173
1174                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1175                         $postLimitTail .= ' LOCK IN SHARE MODE';
1176                 }
1177
1178                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1179                         $startOpts .= 'DISTINCT';
1180                 }
1181
1182                 # Various MySQL extensions
1183                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1184                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1185                 }
1186
1187                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1188                         $startOpts .= ' HIGH_PRIORITY';
1189                 }
1190
1191                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1192                         $startOpts .= ' SQL_BIG_RESULT';
1193                 }
1194
1195                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1196                         $startOpts .= ' SQL_BUFFER_RESULT';
1197                 }
1198
1199                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1200                         $startOpts .= ' SQL_SMALL_RESULT';
1201                 }
1202
1203                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1204                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1205                 }
1206
1207                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1208                         $startOpts .= ' SQL_CACHE';
1209                 }
1210
1211                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1212                         $startOpts .= ' SQL_NO_CACHE';
1213                 }
1214
1215                 if ( isset( $options['USE INDEX'] ) && ! is_array( $options['USE INDEX'] ) ) {
1216                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1217                 } else {
1218                         $useIndex = '';
1219                 }
1220
1221                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1222         }
1223
1224         /**
1225          * Execute a SELECT query constructed using the various parameters provided.
1226          * See below for full details of the parameters.
1227          *
1228          * @param $table String|Array Table name
1229          * @param $vars String|Array Field names
1230          * @param $conds String|Array Conditions
1231          * @param $fname String Caller function name
1232          * @param $options Array Query options
1233          * @param $join_conds Array Join conditions
1234          *
1235          * @param $table string|array
1236          *
1237          * May be either an array of table names, or a single string holding a table
1238          * name. If an array is given, table aliases can be specified, for example:
1239          *
1240          *    array( 'a' => 'user' )
1241          *
1242          * This includes the user table in the query, with the alias "a" available
1243          * for use in field names (e.g. a.user_name).
1244          *
1245          * All of the table names given here are automatically run through
1246          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1247          * added, and various other table name mappings to be performed.
1248          *
1249          *
1250          * @param $vars string|array
1251          *
1252          * May be either a field name or an array of field names. The field names
1253          * can be complete fragments of SQL, for direct inclusion into the SELECT
1254          * query. If an array is given, field aliases can be specified, for example:
1255          *
1256          *   array( 'maxrev' => 'MAX(rev_id)' )
1257          *
1258          * This includes an expression with the alias "maxrev" in the query.
1259          *
1260          * If an expression is given, care must be taken to ensure that it is
1261          * DBMS-independent.
1262          *
1263          *
1264          * @param $conds string|array
1265          *
1266          * May be either a string containing a single condition, or an array of
1267          * conditions. If an array is given, the conditions constructed from each
1268          * element are combined with AND.
1269          *
1270          * Array elements may take one of two forms:
1271          *
1272          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1273          *   - Elements with a string key are interpreted as equality conditions,
1274          *     where the key is the field name.
1275          *     - If the value of such an array element is a scalar (such as a
1276          *       string), it will be treated as data and thus quoted appropriately.
1277          *       If it is null, an IS NULL clause will be added.
1278          *     - If the value is an array, an IN(...) clause will be constructed,
1279          *       such that the field name may match any of the elements in the
1280          *       array. The elements of the array will be quoted.
1281          *
1282          * Note that expressions are often DBMS-dependent in their syntax.
1283          * DBMS-independent wrappers are provided for constructing several types of
1284          * expression commonly used in condition queries. See:
1285          *    - DatabaseBase::buildLike()
1286          *    - DatabaseBase::conditional()
1287          *
1288          *
1289          * @param $options string|array
1290          *
1291          * Optional: Array of query options. Boolean options are specified by
1292          * including them in the array as a string value with a numeric key, for
1293          * example:
1294          *
1295          *    array( 'FOR UPDATE' )
1296          *
1297          * The supported options are:
1298          *
1299          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1300          *     with LIMIT can theoretically be used for paging through a result set,
1301          *     but this is discouraged in MediaWiki for performance reasons.
1302          *
1303          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1304          *     and then the first rows are taken until the limit is reached. LIMIT
1305          *     is applied to a result set after OFFSET.
1306          *
1307          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1308          *     changed until the next COMMIT.
1309          *
1310          *   - DISTINCT: Boolean: return only unique result rows.
1311          *
1312          *   - GROUP BY: May be either an SQL fragment string naming a field or
1313          *     expression to group by, or an array of such SQL fragments.
1314          *
1315          *   - HAVING: May be either an string containing a HAVING clause or an array of
1316          *     conditions building the HAVING clause. If an array is given, the conditions
1317          *     constructed from each element are combined with AND.
1318          *
1319          *   - ORDER BY: May be either an SQL fragment giving a field name or
1320          *     expression to order by, or an array of such SQL fragments.
1321          *
1322          *   - USE INDEX: This may be either a string giving the index name to use
1323          *     for the query, or an array. If it is an associative array, each key
1324          *     gives the table name (or alias), each value gives the index name to
1325          *     use for that table. All strings are SQL fragments and so should be
1326          *     validated by the caller.
1327          *
1328          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1329          *     instead of SELECT.
1330          *
1331          * And also the following boolean MySQL extensions, see the MySQL manual
1332          * for documentation:
1333          *
1334          *    - LOCK IN SHARE MODE
1335          *    - STRAIGHT_JOIN
1336          *    - HIGH_PRIORITY
1337          *    - SQL_BIG_RESULT
1338          *    - SQL_BUFFER_RESULT
1339          *    - SQL_SMALL_RESULT
1340          *    - SQL_CALC_FOUND_ROWS
1341          *    - SQL_CACHE
1342          *    - SQL_NO_CACHE
1343          *
1344          *
1345          * @param $join_conds string|array
1346          *
1347          * Optional associative array of table-specific join conditions. In the
1348          * most common case, this is unnecessary, since the join condition can be
1349          * in $conds. However, it is useful for doing a LEFT JOIN.
1350          *
1351          * The key of the array contains the table name or alias. The value is an
1352          * array with two elements, numbered 0 and 1. The first gives the type of
1353          * join, the second is an SQL fragment giving the join condition for that
1354          * table. For example:
1355          *
1356          *    array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
1357          *
1358          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1359          *   with no rows in it will be returned. If there was a query error, a
1360          *   DBQueryError exception will be thrown, except if the "ignore errors"
1361          *   option was set, in which case false will be returned.
1362          */
1363         public function select( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1364                 $options = array(), $join_conds = array() ) {
1365                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1366
1367                 return $this->query( $sql, $fname );
1368         }
1369
1370         /**
1371          * The equivalent of DatabaseBase::select() except that the constructed SQL
1372          * is returned, instead of being immediately executed. This can be useful for
1373          * doing UNION queries, where the SQL text of each query is needed. In general,
1374          * however, callers outside of Database classes should just use select().
1375          *
1376          * @param $table string|array Table name
1377          * @param $vars string|array Field names
1378          * @param $conds string|array Conditions
1379          * @param $fname string Caller function name
1380          * @param $options string|array Query options
1381          * @param $join_conds string|array Join conditions
1382          *
1383          * @return string SQL query string.
1384          * @see DatabaseBase::select()
1385          */
1386         public function selectSQLText( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1387                 $options = array(), $join_conds = array() )
1388         {
1389                 if ( is_array( $vars ) ) {
1390                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1391                 }
1392
1393                 $options = (array)$options;
1394
1395                 if ( is_array( $table ) ) {
1396                         $useIndex = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1397                                 ? $options['USE INDEX']
1398                                 : array();
1399                         if ( count( $join_conds ) || count( $useIndex ) ) {
1400                                 $from = ' FROM ' .
1401                                         $this->tableNamesWithUseIndexOrJOIN( $table, $useIndex, $join_conds );
1402                         } else {
1403                                 $from = ' FROM ' . implode( ',', $this->tableNamesWithAlias( $table ) );
1404                         }
1405                 } elseif ( $table != '' ) {
1406                         if ( $table[0] == ' ' ) {
1407                                 $from = ' FROM ' . $table;
1408                         } else {
1409                                 $from = ' FROM ' . $this->tableName( $table );
1410                         }
1411                 } else {
1412                         $from = '';
1413                 }
1414
1415                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) = $this->makeSelectOptions( $options );
1416
1417                 if ( !empty( $conds ) ) {
1418                         if ( is_array( $conds ) ) {
1419                                 $conds = $this->makeList( $conds, LIST_AND );
1420                         }
1421                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1422                 } else {
1423                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1424                 }
1425
1426                 if ( isset( $options['LIMIT'] ) ) {
1427                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1428                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1429                 }
1430                 $sql = "$sql $postLimitTail";
1431
1432                 if ( isset( $options['EXPLAIN'] ) ) {
1433                         $sql = 'EXPLAIN ' . $sql;
1434                 }
1435
1436                 return $sql;
1437         }
1438
1439         /**
1440          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1441          * that a single row object is returned. If the query returns no rows,
1442          * false is returned.
1443          *
1444          * @param $table string|array Table name
1445          * @param $vars string|array Field names
1446          * @param $conds array Conditions
1447          * @param $fname string Caller function name
1448          * @param $options string|array Query options
1449          * @param $join_conds array|string Join conditions
1450          *
1451          * @return object|bool
1452          */
1453         public function selectRow( $table, $vars, $conds, $fname = 'DatabaseBase::selectRow',
1454                 $options = array(), $join_conds = array() )
1455         {
1456                 $options = (array)$options;
1457                 $options['LIMIT'] = 1;
1458                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1459
1460                 if ( $res === false ) {
1461                         return false;
1462                 }
1463
1464                 if ( !$this->numRows( $res ) ) {
1465                         return false;
1466                 }
1467
1468                 $obj = $this->fetchObject( $res );
1469
1470                 return $obj;
1471         }
1472
1473         /**
1474          * Estimate rows in dataset.
1475          *
1476          * MySQL allows you to estimate the number of rows that would be returned
1477          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1478          * index cardinality statistics, and is notoriously inaccurate, especially
1479          * when large numbers of rows have recently been added or deleted.
1480          *
1481          * For DBMSs that don't support fast result size estimation, this function
1482          * will actually perform the SELECT COUNT(*).
1483          *
1484          * Takes the same arguments as DatabaseBase::select().
1485          *
1486          * @param $table String: table name
1487          * @param Array|string $vars : unused
1488          * @param Array|string $conds : filters on the table
1489          * @param $fname String: function name for profiling
1490          * @param $options Array: options for select
1491          * @return Integer: row count
1492          */
1493         public function estimateRowCount( $table, $vars = '*', $conds = '',
1494                 $fname = 'DatabaseBase::estimateRowCount', $options = array() )
1495         {
1496                 $rows = 0;
1497                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1498
1499                 if ( $res ) {
1500                         $row = $this->fetchRow( $res );
1501                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1502                 }
1503
1504                 return $rows;
1505         }
1506
1507         /**
1508          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1509          * It's only slightly flawed. Don't use for anything important.
1510          *
1511          * @param $sql String A SQL Query
1512          *
1513          * @return string
1514          */
1515         static function generalizeSQL( $sql ) {
1516                 # This does the same as the regexp below would do, but in such a way
1517                 # as to avoid crashing php on some large strings.
1518                 # $sql = preg_replace ( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql);
1519
1520                 $sql = str_replace ( "\\\\", '', $sql );
1521                 $sql = str_replace ( "\\'", '', $sql );
1522                 $sql = str_replace ( "\\\"", '', $sql );
1523                 $sql = preg_replace ( "/'.*'/s", "'X'", $sql );
1524                 $sql = preg_replace ( '/".*"/s', "'X'", $sql );
1525
1526                 # All newlines, tabs, etc replaced by single space
1527                 $sql = preg_replace ( '/\s+/', ' ', $sql );
1528
1529                 # All numbers => N
1530                 $sql = preg_replace ( '/-?[0-9]+/s', 'N', $sql );
1531
1532                 return $sql;
1533         }
1534
1535         /**
1536          * Determines whether a field exists in a table
1537          *
1538          * @param $table String: table name
1539          * @param $field String: filed to check on that table
1540          * @param $fname String: calling function name (optional)
1541          * @return Boolean: whether $table has filed $field
1542          */
1543         public function fieldExists( $table, $field, $fname = 'DatabaseBase::fieldExists' ) {
1544                 $info = $this->fieldInfo( $table, $field );
1545
1546                 return (bool)$info;
1547         }
1548
1549         /**
1550          * Determines whether an index exists
1551          * Usually throws a DBQueryError on failure
1552          * If errors are explicitly ignored, returns NULL on failure
1553          *
1554          * @param $table
1555          * @param $index
1556          * @param $fname string
1557          *
1558          * @return bool|null
1559          */
1560         public function indexExists( $table, $index, $fname = 'DatabaseBase::indexExists' ) {
1561                 $info = $this->indexInfo( $table, $index, $fname );
1562                 if ( is_null( $info ) ) {
1563                         return null;
1564                 } else {
1565                         return $info !== false;
1566                 }
1567         }
1568
1569         /**
1570          * Query whether a given table exists
1571          *
1572          * @param $table string
1573          * @param $fname string
1574          *
1575          * @return bool
1576          */
1577         public function tableExists( $table, $fname = __METHOD__ ) {
1578                 $table = $this->tableName( $table );
1579                 $old = $this->ignoreErrors( true );
1580                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1581                 $this->ignoreErrors( $old );
1582
1583                 return (bool)$res;
1584         }
1585
1586         /**
1587          * mysql_field_type() wrapper
1588          * @param $res
1589          * @param $index
1590          * @return string
1591          */
1592         public function fieldType( $res, $index ) {
1593                 if ( $res instanceof ResultWrapper ) {
1594                         $res = $res->result;
1595                 }
1596
1597                 return mysql_field_type( $res, $index );
1598         }
1599
1600         /**
1601          * Determines if a given index is unique
1602          *
1603          * @param $table string
1604          * @param $index string
1605          *
1606          * @return bool
1607          */
1608         public function indexUnique( $table, $index ) {
1609                 $indexInfo = $this->indexInfo( $table, $index );
1610
1611                 if ( !$indexInfo ) {
1612                         return null;
1613                 }
1614
1615                 return !$indexInfo[0]->Non_unique;
1616         }
1617
1618         /**
1619          * Helper for DatabaseBase::insert().
1620          *
1621          * @param $options array
1622          * @return string
1623          */
1624         protected function makeInsertOptions( $options ) {
1625                 return implode( ' ', $options );
1626         }
1627
1628         /**
1629          * INSERT wrapper, inserts an array into a table.
1630          *
1631          * $a may be either:
1632          *
1633          *   - A single associative array. The array keys are the field names, and
1634          *     the values are the values to insert. The values are treated as data
1635          *     and will be quoted appropriately. If NULL is inserted, this will be
1636          *     converted to a database NULL.
1637          *   - An array with numeric keys, holding a list of associative arrays.
1638          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1639          *     each subarray must be identical to each other, and in the same order.
1640          *
1641          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1642          * returns success.
1643          *
1644          * $options is an array of options, with boolean options encoded as values
1645          * with numeric keys, in the same style as $options in
1646          * DatabaseBase::select(). Supported options are:
1647          *
1648          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1649          *     any rows which cause duplicate key errors are not inserted. It's
1650          *     possible to determine how many rows were successfully inserted using
1651          *     DatabaseBase::affectedRows().
1652          *
1653          * @param $table   String Table name. This will be passed through
1654          *                 DatabaseBase::tableName().
1655          * @param $a       Array of rows to insert
1656          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1657          * @param $options Array of options
1658          *
1659          * @return bool
1660          */
1661         public function insert( $table, $a, $fname = 'DatabaseBase::insert', $options = array() ) {
1662                 # No rows to insert, easy just return now
1663                 if ( !count( $a ) ) {
1664                         return true;
1665                 }
1666
1667                 $table = $this->tableName( $table );
1668
1669                 if ( !is_array( $options ) ) {
1670                         $options = array( $options );
1671                 }
1672
1673                 $options = $this->makeInsertOptions( $options );
1674
1675                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1676                         $multi = true;
1677                         $keys = array_keys( $a[0] );
1678                 } else {
1679                         $multi = false;
1680                         $keys = array_keys( $a );
1681                 }
1682
1683                 $sql = 'INSERT ' . $options .
1684                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1685
1686                 if ( $multi ) {
1687                         $first = true;
1688                         foreach ( $a as $row ) {
1689                                 if ( $first ) {
1690                                         $first = false;
1691                                 } else {
1692                                         $sql .= ',';
1693                                 }
1694                                 $sql .= '(' . $this->makeList( $row ) . ')';
1695                         }
1696                 } else {
1697                         $sql .= '(' . $this->makeList( $a ) . ')';
1698                 }
1699
1700                 return (bool)$this->query( $sql, $fname );
1701         }
1702
1703         /**
1704          * Make UPDATE options for the DatabaseBase::update function
1705          *
1706          * @param $options Array: The options passed to DatabaseBase::update
1707          * @return string
1708          */
1709         protected function makeUpdateOptions( $options ) {
1710                 if ( !is_array( $options ) ) {
1711                         $options = array( $options );
1712                 }
1713
1714                 $opts = array();
1715
1716                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1717                         $opts[] = $this->lowPriorityOption();
1718                 }
1719
1720                 if ( in_array( 'IGNORE', $options ) ) {
1721                         $opts[] = 'IGNORE';
1722                 }
1723
1724                 return implode( ' ', $opts );
1725         }
1726
1727         /**
1728          * UPDATE wrapper. Takes a condition array and a SET array.
1729          *
1730          * @param $table  String name of the table to UPDATE. This will be passed through
1731          *                DatabaseBase::tableName().
1732          *
1733          * @param $values Array:  An array of values to SET. For each array element,
1734          *                the key gives the field name, and the value gives the data
1735          *                to set that field to. The data will be quoted by
1736          *                DatabaseBase::addQuotes().
1737          *
1738          * @param $conds  Array:  An array of conditions (WHERE). See
1739          *                DatabaseBase::select() for the details of the format of
1740          *                condition arrays. Use '*' to update all rows.
1741          *
1742          * @param $fname  String: The function name of the caller (from __METHOD__),
1743          *                for logging and profiling.
1744          *
1745          * @param $options Array: An array of UPDATE options, can be:
1746          *                   - IGNORE: Ignore unique key conflicts
1747          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1748          * @return Boolean
1749          */
1750         function update( $table, $values, $conds, $fname = 'DatabaseBase::update', $options = array() ) {
1751                 $table = $this->tableName( $table );
1752                 $opts = $this->makeUpdateOptions( $options );
1753                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1754
1755                 if ( $conds !== array() && $conds !== '*' ) {
1756                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1757                 }
1758
1759                 return $this->query( $sql, $fname );
1760         }
1761
1762         /**
1763          * Makes an encoded list of strings from an array
1764          * @param $a Array containing the data
1765          * @param int $mode Constant
1766          *      - LIST_COMMA:          comma separated, no field names
1767          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1768          *        the documentation for $conds in DatabaseBase::select().
1769          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1770          *      - LIST_SET:            comma separated with field names, like a SET clause
1771          *      - LIST_NAMES:          comma separated field names
1772          *
1773          * @throws MWException|DBUnexpectedError
1774          * @return string
1775          */
1776         public function makeList( $a, $mode = LIST_COMMA ) {
1777                 if ( !is_array( $a ) ) {
1778                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1779                 }
1780
1781                 $first = true;
1782                 $list = '';
1783
1784                 foreach ( $a as $field => $value ) {
1785                         if ( !$first ) {
1786                                 if ( $mode == LIST_AND ) {
1787                                         $list .= ' AND ';
1788                                 } elseif ( $mode == LIST_OR ) {
1789                                         $list .= ' OR ';
1790                                 } else {
1791                                         $list .= ',';
1792                                 }
1793                         } else {
1794                                 $first = false;
1795                         }
1796
1797                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1798                                 $list .= "($value)";
1799                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1800                                 $list .= "$value";
1801                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1802                                 if ( count( $value ) == 0 ) {
1803                                         throw new MWException( __METHOD__ . ': empty input' );
1804                                 } elseif ( count( $value ) == 1 ) {
1805                                         // Special-case single values, as IN isn't terribly efficient
1806                                         // Don't necessarily assume the single key is 0; we don't
1807                                         // enforce linear numeric ordering on other arrays here.
1808                                         $value = array_values( $value );
1809                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1810                                 } else {
1811                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1812                                 }
1813                         } elseif ( $value === null ) {
1814                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1815                                         $list .= "$field IS ";
1816                                 } elseif ( $mode == LIST_SET ) {
1817                                         $list .= "$field = ";
1818                                 }
1819                                 $list .= 'NULL';
1820                         } else {
1821                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1822                                         $list .= "$field = ";
1823                                 }
1824                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1825                         }
1826                 }
1827
1828                 return $list;
1829         }
1830
1831         /**
1832          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1833          * The keys on each level may be either integers or strings.
1834          *
1835          * @param $data Array: organized as 2-d
1836          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
1837          * @param $baseKey String: field name to match the base-level keys to (eg 'pl_namespace')
1838          * @param $subKey String: field name to match the sub-level keys to (eg 'pl_title')
1839          * @return Mixed: string SQL fragment, or false if no items in array.
1840          */
1841         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1842                 $conds = array();
1843
1844                 foreach ( $data as $base => $sub ) {
1845                         if ( count( $sub ) ) {
1846                                 $conds[] = $this->makeList(
1847                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1848                                         LIST_AND );
1849                         }
1850                 }
1851
1852                 if ( $conds ) {
1853                         return $this->makeList( $conds, LIST_OR );
1854                 } else {
1855                         // Nothing to search for...
1856                         return false;
1857                 }
1858         }
1859
1860         /**
1861          * Return aggregated value alias
1862          *
1863          * @param $valuedata
1864          * @param $valuename string
1865          *
1866          * @return string
1867          */
1868         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1869                 return $valuename;
1870         }
1871
1872         /**
1873          * @param $field
1874          * @return string
1875          */
1876         public function bitNot( $field ) {
1877                 return "(~$field)";
1878         }
1879
1880         /**
1881          * @param $fieldLeft
1882          * @param $fieldRight
1883          * @return string
1884          */
1885         public function bitAnd( $fieldLeft, $fieldRight ) {
1886                 return "($fieldLeft & $fieldRight)";
1887         }
1888
1889         /**
1890          * @param  $fieldLeft
1891          * @param  $fieldRight
1892          * @return string
1893          */
1894         public function bitOr( $fieldLeft, $fieldRight ) {
1895                 return "($fieldLeft | $fieldRight)";
1896         }
1897
1898         /**
1899          * Build a concatenation list to feed into a SQL query
1900          * @param $stringList Array: list of raw SQL expressions; caller is responsible for any quoting
1901          * @return String
1902          */
1903         public function buildConcat( $stringList ) {
1904                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1905         }
1906
1907         /**
1908          * Change the current database
1909          *
1910          * @todo Explain what exactly will fail if this is not overridden.
1911          *
1912          * @param $db
1913          *
1914          * @return bool Success or failure
1915          */
1916         public function selectDB( $db ) {
1917                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
1918                 # if your database engine supports a concept similar to MySQL's
1919                 # databases you may as well.
1920                 $this->mDBname = $db;
1921                 return true;
1922         }
1923
1924         /**
1925          * Get the current DB name
1926          */
1927         public function getDBname() {
1928                 return $this->mDBname;
1929         }
1930
1931         /**
1932          * Get the server hostname or IP address
1933          */
1934         public function getServer() {
1935                 return $this->mServer;
1936         }
1937
1938         /**
1939          * Format a table name ready for use in constructing an SQL query
1940          *
1941          * This does two important things: it quotes the table names to clean them up,
1942          * and it adds a table prefix if only given a table name with no quotes.
1943          *
1944          * All functions of this object which require a table name call this function
1945          * themselves. Pass the canonical name to such functions. This is only needed
1946          * when calling query() directly.
1947          *
1948          * @param $name String: database table name
1949          * @param $format String One of:
1950          *   quoted - Automatically pass the table name through addIdentifierQuotes()
1951          *            so that it can be used in a query.
1952          *   raw - Do not add identifier quotes to the table name
1953          * @return String: full database name
1954          */
1955         public function tableName( $name, $format = 'quoted' ) {
1956                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
1957                 # Skip the entire process when we have a string quoted on both ends.
1958                 # Note that we check the end so that we will still quote any use of
1959                 # use of `database`.table. But won't break things if someone wants
1960                 # to query a database table with a dot in the name.
1961                 if ( $this->isQuotedIdentifier( $name ) ) {
1962                         return $name;
1963                 }
1964
1965                 # Lets test for any bits of text that should never show up in a table
1966                 # name. Basically anything like JOIN or ON which are actually part of
1967                 # SQL queries, but may end up inside of the table value to combine
1968                 # sql. Such as how the API is doing.
1969                 # Note that we use a whitespace test rather than a \b test to avoid
1970                 # any remote case where a word like on may be inside of a table name
1971                 # surrounded by symbols which may be considered word breaks.
1972                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1973                         return $name;
1974                 }
1975
1976                 # Split database and table into proper variables.
1977                 # We reverse the explode so that database.table and table both output
1978                 # the correct table.
1979                 $dbDetails = array_reverse( explode( '.', $name, 2 ) );
1980                 if ( isset( $dbDetails[1] ) ) {
1981                         list( $table, $database ) = $dbDetails;
1982                 } else {
1983                         list( $table ) = $dbDetails;
1984                 }
1985                 $prefix = $this->mTablePrefix; # Default prefix
1986
1987                 # A database name has been specified in input. We don't want any
1988                 # prefixes added.
1989                 if ( isset( $database ) ) {
1990                         $prefix = '';
1991                 }
1992
1993                 # Note that we use the long format because php will complain in in_array if
1994                 # the input is not an array, and will complain in is_array if it is not set.
1995                 if ( !isset( $database ) # Don't use shared database if pre selected.
1996                  && isset( $wgSharedDB ) # We have a shared database
1997                  && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
1998                  && isset( $wgSharedTables )
1999                  && is_array( $wgSharedTables )
2000                  && in_array( $table, $wgSharedTables ) ) { # A shared table is selected
2001                         $database = $wgSharedDB;
2002                         $prefix   = isset( $wgSharedPrefix ) ? $wgSharedPrefix : $prefix;
2003                 }
2004
2005                 # Quote the $database and $table and apply the prefix if not quoted.
2006                 if ( isset( $database ) ) {
2007                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
2008                                 $database = $this->addIdentifierQuotes( $database );
2009                         }
2010                 }
2011
2012                 $table = "{$prefix}{$table}";
2013                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $table ) ) {
2014                         $table = $this->addIdentifierQuotes( "{$table}" );
2015                 }
2016
2017                 # Merge our database and table into our final table name.
2018                 $tableName = ( isset( $database ) ? "{$database}.{$table}" : "{$table}" );
2019
2020                 return $tableName;
2021         }
2022
2023         /**
2024          * Fetch a number of table names into an array
2025          * This is handy when you need to construct SQL for joins
2026          *
2027          * Example:
2028          * extract($dbr->tableNames('user','watchlist'));
2029          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2030          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2031          *
2032          * @return array
2033          */
2034         public function tableNames() {
2035                 $inArray = func_get_args();
2036                 $retVal = array();
2037
2038                 foreach ( $inArray as $name ) {
2039                         $retVal[$name] = $this->tableName( $name );
2040                 }
2041
2042                 return $retVal;
2043         }
2044
2045         /**
2046          * Fetch a number of table names into an zero-indexed numerical array
2047          * This is handy when you need to construct SQL for joins
2048          *
2049          * Example:
2050          * list( $user, $watchlist ) = $dbr->tableNamesN('user','watchlist');
2051          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2052          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2053          *
2054          * @return array
2055          */
2056         public function tableNamesN() {
2057                 $inArray = func_get_args();
2058                 $retVal = array();
2059
2060                 foreach ( $inArray as $name ) {
2061                         $retVal[] = $this->tableName( $name );
2062                 }
2063
2064                 return $retVal;
2065         }
2066
2067         /**
2068          * Get an aliased table name
2069          * e.g. tableName AS newTableName
2070          *
2071          * @param $name string Table name, see tableName()
2072          * @param $alias string|bool Alias (optional)
2073          * @return string SQL name for aliased table. Will not alias a table to its own name
2074          */
2075         public function tableNameWithAlias( $name, $alias = false ) {
2076                 if ( !$alias || $alias == $name ) {
2077                         return $this->tableName( $name );
2078                 } else {
2079                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2080                 }
2081         }
2082
2083         /**
2084          * Gets an array of aliased table names
2085          *
2086          * @param $tables array( [alias] => table )
2087          * @return array of strings, see tableNameWithAlias()
2088          */
2089         public function tableNamesWithAlias( $tables ) {
2090                 $retval = array();
2091                 foreach ( $tables as $alias => $table ) {
2092                         if ( is_numeric( $alias ) ) {
2093                                 $alias = $table;
2094                         }
2095                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2096                 }
2097                 return $retval;
2098         }
2099
2100         /**
2101          * Get an aliased field name
2102          * e.g. fieldName AS newFieldName
2103          *
2104          * @param $name string Field name
2105          * @param $alias string|bool Alias (optional)
2106          * @return string SQL name for aliased field. Will not alias a field to its own name
2107          */
2108         public function fieldNameWithAlias( $name, $alias = false ) {
2109                 if ( !$alias || (string)$alias === (string)$name ) {
2110                         return $name;
2111                 } else {
2112                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2113                 }
2114         }
2115
2116         /**
2117          * Gets an array of aliased field names
2118          *
2119          * @param $fields array( [alias] => field )
2120          * @return array of strings, see fieldNameWithAlias()
2121          */
2122         public function fieldNamesWithAlias( $fields ) {
2123                 $retval = array();
2124                 foreach ( $fields as $alias => $field ) {
2125                         if ( is_numeric( $alias ) ) {
2126                                 $alias = $field;
2127                         }
2128                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2129                 }
2130                 return $retval;
2131         }
2132
2133         /**
2134          * Get the aliased table name clause for a FROM clause
2135          * which might have a JOIN and/or USE INDEX clause
2136          *
2137          * @param $tables array ( [alias] => table )
2138          * @param $use_index array Same as for select()
2139          * @param $join_conds array Same as for select()
2140          * @return string
2141          */
2142         protected function tableNamesWithUseIndexOrJOIN(
2143                 $tables, $use_index = array(), $join_conds = array()
2144         ) {
2145                 $ret = array();
2146                 $retJOIN = array();
2147                 $use_index = (array)$use_index;
2148                 $join_conds = (array)$join_conds;
2149
2150                 foreach ( $tables as $alias => $table ) {
2151                         if ( !is_string( $alias ) ) {
2152                                 // No alias? Set it equal to the table name
2153                                 $alias = $table;
2154                         }
2155                         // Is there a JOIN clause for this table?
2156                         if ( isset( $join_conds[$alias] ) ) {
2157                                 list( $joinType, $conds ) = $join_conds[$alias];
2158                                 $tableClause = $joinType;
2159                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2160                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2161                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2162                                         if ( $use != '' ) {
2163                                                 $tableClause .= ' ' . $use;
2164                                         }
2165                                 }
2166                                 $on = $this->makeList( (array)$conds, LIST_AND );
2167                                 if ( $on != '' ) {
2168                                         $tableClause .= ' ON (' . $on . ')';
2169                                 }
2170
2171                                 $retJOIN[] = $tableClause;
2172                         // Is there an INDEX clause for this table?
2173                         } elseif ( isset( $use_index[$alias] ) ) {
2174                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2175                                 $tableClause .= ' ' . $this->useIndexClause(
2176                                         implode( ',', (array)$use_index[$alias] ) );
2177
2178                                 $ret[] = $tableClause;
2179                         } else {
2180                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2181
2182                                 $ret[] = $tableClause;
2183                         }
2184                 }
2185
2186                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2187                 $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2188                 $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2189
2190                 // Compile our final table clause
2191                 return implode( ' ', array( $straightJoins, $otherJoins ) );
2192         }
2193
2194         /**
2195          * Get the name of an index in a given table
2196          *
2197          * @param $index
2198          *
2199          * @return string
2200          */
2201         protected function indexName( $index ) {
2202                 // Backwards-compatibility hack
2203                 $renamed = array(
2204                         'ar_usertext_timestamp' => 'usertext_timestamp',
2205                         'un_user_id'            => 'user_id',
2206                         'un_user_ip'            => 'user_ip',
2207                 );
2208
2209                 if ( isset( $renamed[$index] ) ) {
2210                         return $renamed[$index];
2211                 } else {
2212                         return $index;
2213                 }
2214         }
2215
2216         /**
2217          * If it's a string, adds quotes and backslashes
2218          * Otherwise returns as-is
2219          *
2220          * @param $s string
2221          *
2222          * @return string
2223          */
2224         public function addQuotes( $s ) {
2225                 if ( $s === null ) {
2226                         return 'NULL';
2227                 } else {
2228                         # This will also quote numeric values. This should be harmless,
2229                         # and protects against weird problems that occur when they really
2230                         # _are_ strings such as article titles and string->number->string
2231                         # conversion is not 1:1.
2232                         return "'" . $this->strencode( $s ) . "'";
2233                 }
2234         }
2235
2236         /**
2237          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2238          * MySQL uses `backticks` while basically everything else uses double quotes.
2239          * Since MySQL is the odd one out here the double quotes are our generic
2240          * and we implement backticks in DatabaseMysql.
2241          *
2242          * @param $s string
2243          *
2244          * @return string
2245          */
2246         public function addIdentifierQuotes( $s ) {
2247                 return '"' . str_replace( '"', '""', $s ) . '"';
2248         }
2249
2250         /**
2251          * Returns if the given identifier looks quoted or not according to
2252          * the database convention for quoting identifiers .
2253          *
2254          * @param $name string
2255          *
2256          * @return boolean
2257          */
2258         public function isQuotedIdentifier( $name ) {
2259                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2260         }
2261
2262         /**
2263          * @param $s string
2264          * @return string
2265          */
2266         protected function escapeLikeInternal( $s ) {
2267                 $s = str_replace( '\\', '\\\\', $s );
2268                 $s = $this->strencode( $s );
2269                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2270
2271                 return $s;
2272         }
2273
2274         /**
2275          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2276          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2277          * Alternatively, the function could be provided with an array of aforementioned parameters.
2278          *
2279          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2280          * for subpages of 'My page title'.
2281          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2282          *
2283          * @since 1.16
2284          * @return String: fully built LIKE statement
2285          */
2286         public function buildLike() {
2287                 $params = func_get_args();
2288
2289                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2290                         $params = $params[0];
2291                 }
2292
2293                 $s = '';
2294
2295                 foreach ( $params as $value ) {
2296                         if ( $value instanceof LikeMatch ) {
2297                                 $s .= $value->toString();
2298                         } else {
2299                                 $s .= $this->escapeLikeInternal( $value );
2300                         }
2301                 }
2302
2303                 return " LIKE '" . $s . "' ";
2304         }
2305
2306         /**
2307          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2308          *
2309          * @return LikeMatch
2310          */
2311         public function anyChar() {
2312                 return new LikeMatch( '_' );
2313         }
2314
2315         /**
2316          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2317          *
2318          * @return LikeMatch
2319          */
2320         public function anyString() {
2321                 return new LikeMatch( '%' );
2322         }
2323
2324         /**
2325          * Returns an appropriately quoted sequence value for inserting a new row.
2326          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2327          * subclass will return an integer, and save the value for insertId()
2328          *
2329          * Any implementation of this function should *not* involve reusing
2330          * sequence numbers created for rolled-back transactions.
2331          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2332          * @param $seqName string
2333          * @return null
2334          */
2335         public function nextSequenceValue( $seqName ) {
2336                 return null;
2337         }
2338
2339         /**
2340          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2341          * is only needed because a) MySQL must be as efficient as possible due to
2342          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2343          * which index to pick.  Anyway, other databases might have different
2344          * indexes on a given table.  So don't bother overriding this unless you're
2345          * MySQL.
2346          * @param $index
2347          * @return string
2348          */
2349         public function useIndexClause( $index ) {
2350                 return '';
2351         }
2352
2353         /**
2354          * REPLACE query wrapper.
2355          *
2356          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2357          * except that when there is a duplicate key error, the old row is deleted
2358          * and the new row is inserted in its place.
2359          *
2360          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2361          * perform the delete, we need to know what the unique indexes are so that
2362          * we know how to find the conflicting rows.
2363          *
2364          * It may be more efficient to leave off unique indexes which are unlikely
2365          * to collide. However if you do this, you run the risk of encountering
2366          * errors which wouldn't have occurred in MySQL.
2367          *
2368          * @param $table String: The table to replace the row(s) in.
2369          * @param $rows array Can be either a single row to insert, or multiple rows,
2370          *    in the same format as for DatabaseBase::insert()
2371          * @param $uniqueIndexes array is an array of indexes. Each element may be either
2372          *    a field name or an array of field names
2373          * @param $fname String: Calling function name (use __METHOD__) for logs/profiling
2374          */
2375         public function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseBase::replace' ) {
2376                 $quotedTable = $this->tableName( $table );
2377
2378                 if ( count( $rows ) == 0 ) {
2379                         return;
2380                 }
2381
2382                 # Single row case
2383                 if ( !is_array( reset( $rows ) ) ) {
2384                         $rows = array( $rows );
2385                 }
2386
2387                 foreach( $rows as $row ) {
2388                         # Delete rows which collide
2389                         if ( $uniqueIndexes ) {
2390                                 $sql = "DELETE FROM $quotedTable WHERE ";
2391                                 $first = true;
2392                                 foreach ( $uniqueIndexes as $index ) {
2393                                         if ( $first ) {
2394                                                 $first = false;
2395                                                 $sql .= '( ';
2396                                         } else {
2397                                                 $sql .= ' ) OR ( ';
2398                                         }
2399                                         if ( is_array( $index ) ) {
2400                                                 $first2 = true;
2401                                                 foreach ( $index as $col ) {
2402                                                         if ( $first2 ) {
2403                                                                 $first2 = false;
2404                                                         } else {
2405                                                                 $sql .= ' AND ';
2406                                                         }
2407                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2408                                                 }
2409                                         } else {
2410                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2411                                         }
2412                                 }
2413                                 $sql .= ' )';
2414                                 $this->query( $sql, $fname );
2415                         }
2416
2417                         # Now insert the row
2418                         $this->insert( $table, $row );
2419                 }
2420         }
2421
2422         /**
2423          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2424          * statement.
2425          *
2426          * @param $table string Table name
2427          * @param $rows array Rows to insert
2428          * @param $fname string Caller function name
2429          *
2430          * @return ResultWrapper
2431          */
2432         protected function nativeReplace( $table, $rows, $fname ) {
2433                 $table = $this->tableName( $table );
2434
2435                 # Single row case
2436                 if ( !is_array( reset( $rows ) ) ) {
2437                         $rows = array( $rows );
2438                 }
2439
2440                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2441                 $first = true;
2442
2443                 foreach ( $rows as $row ) {
2444                         if ( $first ) {
2445                                 $first = false;
2446                         } else {
2447                                 $sql .= ',';
2448                         }
2449
2450                         $sql .= '(' . $this->makeList( $row ) . ')';
2451                 }
2452
2453                 return $this->query( $sql, $fname );
2454         }
2455
2456         /**
2457          * DELETE where the condition is a join.
2458          *
2459          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2460          * we use sub-selects
2461          *
2462          * For safety, an empty $conds will not delete everything. If you want to
2463          * delete all rows where the join condition matches, set $conds='*'.
2464          *
2465          * DO NOT put the join condition in $conds.
2466          *
2467          * @param $delTable   String: The table to delete from.
2468          * @param $joinTable  String: The other table.
2469          * @param $delVar     String: The variable to join on, in the first table.
2470          * @param $joinVar    String: The variable to join on, in the second table.
2471          * @param $conds      Array: Condition array of field names mapped to variables,
2472          *                    ANDed together in the WHERE clause
2473          * @param $fname      String: Calling function name (use __METHOD__) for
2474          *                    logs/profiling
2475          * @throws DBUnexpectedError
2476          */
2477         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2478                 $fname = 'DatabaseBase::deleteJoin' )
2479         {
2480                 if ( !$conds ) {
2481                         throw new DBUnexpectedError( $this,
2482                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2483                 }
2484
2485                 $delTable = $this->tableName( $delTable );
2486                 $joinTable = $this->tableName( $joinTable );
2487                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2488                 if ( $conds != '*' ) {
2489                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2490                 }
2491                 $sql .= ')';
2492
2493                 $this->query( $sql, $fname );
2494         }
2495
2496         /**
2497          * Returns the size of a text field, or -1 for "unlimited"
2498          *
2499          * @param $table string
2500          * @param $field string
2501          *
2502          * @return int
2503          */
2504         public function textFieldSize( $table, $field ) {
2505                 $table = $this->tableName( $table );
2506                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2507                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2508                 $row = $this->fetchObject( $res );
2509
2510                 $m = array();
2511
2512                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2513                         $size = $m[1];
2514                 } else {
2515                         $size = -1;
2516                 }
2517
2518                 return $size;
2519         }
2520
2521         /**
2522          * A string to insert into queries to show that they're low-priority, like
2523          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2524          * string and nothing bad should happen.
2525          *
2526          * @return string Returns the text of the low priority option if it is
2527          *   supported, or a blank string otherwise
2528          */
2529         public function lowPriorityOption() {
2530                 return '';
2531         }
2532
2533         /**
2534          * DELETE query wrapper.
2535          *
2536          * @param $table Array Table name
2537          * @param $conds String|Array of conditions. See $conds in DatabaseBase::select() for
2538          *               the format. Use $conds == "*" to delete all rows
2539          * @param $fname String name of the calling function
2540          *
2541          * @throws DBUnexpectedError
2542          * @return bool
2543          */
2544         public function delete( $table, $conds, $fname = 'DatabaseBase::delete' ) {
2545                 if ( !$conds ) {
2546                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2547                 }
2548
2549                 $table = $this->tableName( $table );
2550                 $sql = "DELETE FROM $table";
2551
2552                 if ( $conds != '*' ) {
2553                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2554                 }
2555
2556                 return $this->query( $sql, $fname );
2557         }
2558
2559         /**
2560          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2561          * into another table.
2562          *
2563          * @param $destTable string The table name to insert into
2564          * @param $srcTable string|array May be either a table name, or an array of table names
2565          *    to include in a join.
2566          *
2567          * @param $varMap array must be an associative array of the form
2568          *    array( 'dest1' => 'source1', ...). Source items may be literals
2569          *    rather than field names, but strings should be quoted with
2570          *    DatabaseBase::addQuotes()
2571          *
2572          * @param $conds array Condition array. See $conds in DatabaseBase::select() for
2573          *    the details of the format of condition arrays. May be "*" to copy the
2574          *    whole table.
2575          *
2576          * @param $fname string The function name of the caller, from __METHOD__
2577          *
2578          * @param $insertOptions array Options for the INSERT part of the query, see
2579          *    DatabaseBase::insert() for details.
2580          * @param $selectOptions array Options for the SELECT part of the query, see
2581          *    DatabaseBase::select() for details.
2582          *
2583          * @return ResultWrapper
2584          */
2585         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2586                 $fname = 'DatabaseBase::insertSelect',
2587                 $insertOptions = array(), $selectOptions = array() )
2588         {
2589                 $destTable = $this->tableName( $destTable );
2590
2591                 if ( is_array( $insertOptions ) ) {
2592                         $insertOptions = implode( ' ', $insertOptions );
2593                 }
2594
2595                 if ( !is_array( $selectOptions ) ) {
2596                         $selectOptions = array( $selectOptions );
2597                 }
2598
2599                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2600
2601                 if ( is_array( $srcTable ) ) {
2602                         $srcTable =  implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2603                 } else {
2604                         $srcTable = $this->tableName( $srcTable );
2605                 }
2606
2607                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2608                         " SELECT $startOpts " . implode( ',', $varMap ) .
2609                         " FROM $srcTable $useIndex ";
2610
2611                 if ( $conds != '*' ) {
2612                         if ( is_array( $conds ) ) {
2613                                 $conds = $this->makeList( $conds, LIST_AND );
2614                         }
2615                         $sql .= " WHERE $conds";
2616                 }
2617
2618                 $sql .= " $tailOpts";
2619
2620                 return $this->query( $sql, $fname );
2621         }
2622
2623         /**
2624          * Construct a LIMIT query with optional offset.  This is used for query
2625          * pages.  The SQL should be adjusted so that only the first $limit rows
2626          * are returned.  If $offset is provided as well, then the first $offset
2627          * rows should be discarded, and the next $limit rows should be returned.
2628          * If the result of the query is not ordered, then the rows to be returned
2629          * are theoretically arbitrary.
2630          *
2631          * $sql is expected to be a SELECT, if that makes a difference.
2632          *
2633          * The version provided by default works in MySQL and SQLite.  It will very
2634          * likely need to be overridden for most other DBMSes.
2635          *
2636          * @param $sql String SQL query we will append the limit too
2637          * @param $limit Integer the SQL limit
2638          * @param $offset Integer|bool the SQL offset (default false)
2639          *
2640          * @throws DBUnexpectedError
2641          * @return string
2642          */
2643         public function limitResult( $sql, $limit, $offset = false ) {
2644                 if ( !is_numeric( $limit ) ) {
2645                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2646                 }
2647                 return "$sql LIMIT "
2648                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2649                         . "{$limit} ";
2650         }
2651
2652         /**
2653          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2654          * within the UNION construct.
2655          * @return Boolean
2656          */
2657         public function unionSupportsOrderAndLimit() {
2658                 return true; // True for almost every DB supported
2659         }
2660
2661         /**
2662          * Construct a UNION query
2663          * This is used for providing overload point for other DB abstractions
2664          * not compatible with the MySQL syntax.
2665          * @param $sqls Array: SQL statements to combine
2666          * @param $all Boolean: use UNION ALL
2667          * @return String: SQL fragment
2668          */
2669         public function unionQueries( $sqls, $all ) {
2670                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2671                 return '(' . implode( $glue, $sqls ) . ')';
2672         }
2673
2674         /**
2675          * Returns an SQL expression for a simple conditional.  This doesn't need
2676          * to be overridden unless CASE isn't supported in your DBMS.
2677          *
2678          * @param $cond string|array SQL expression which will result in a boolean value
2679          * @param $trueVal String: SQL expression to return if true
2680          * @param $falseVal String: SQL expression to return if false
2681          * @return String: SQL fragment
2682          */
2683         public function conditional( $cond, $trueVal, $falseVal ) {
2684                 if ( is_array( $cond ) ) {
2685                         $cond = $this->makeList( $cond, LIST_AND );
2686                 }
2687                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2688         }
2689
2690         /**
2691          * Returns a comand for str_replace function in SQL query.
2692          * Uses REPLACE() in MySQL
2693          *
2694          * @param $orig String: column to modify
2695          * @param $old String: column to seek
2696          * @param $new String: column to replace with
2697          *
2698          * @return string
2699          */
2700         public function strreplace( $orig, $old, $new ) {
2701                 return "REPLACE({$orig}, {$old}, {$new})";
2702         }
2703
2704         /**
2705          * Determines how long the server has been up
2706          * STUB
2707          *
2708          * @return int
2709          */
2710         public function getServerUptime() {
2711                 return 0;
2712         }
2713
2714         /**
2715          * Determines if the last failure was due to a deadlock
2716          * STUB
2717          *
2718          * @return bool
2719          */
2720         public function wasDeadlock() {
2721                 return false;
2722         }
2723
2724         /**
2725          * Determines if the last failure was due to a lock timeout
2726          * STUB
2727          *
2728          * @return bool
2729          */
2730         public function wasLockTimeout() {
2731                 return false;
2732         }
2733
2734         /**
2735          * Determines if the last query error was something that should be dealt
2736          * with by pinging the connection and reissuing the query.
2737          * STUB
2738          *
2739          * @return bool
2740          */
2741         public function wasErrorReissuable() {
2742                 return false;
2743         }
2744
2745         /**
2746          * Determines if the last failure was due to the database being read-only.
2747          * STUB
2748          *
2749          * @return bool
2750          */
2751         public function wasReadOnlyError() {
2752                 return false;
2753         }
2754
2755         /**
2756          * Perform a deadlock-prone transaction.
2757          *
2758          * This function invokes a callback function to perform a set of write
2759          * queries. If a deadlock occurs during the processing, the transaction
2760          * will be rolled back and the callback function will be called again.
2761          *
2762          * Usage:
2763          *   $dbw->deadlockLoop( callback, ... );
2764          *
2765          * Extra arguments are passed through to the specified callback function.
2766          *
2767          * Returns whatever the callback function returned on its successful,
2768          * iteration, or false on error, for example if the retry limit was
2769          * reached.
2770          *
2771          * @return bool
2772          */
2773         public function deadlockLoop() {
2774                 $this->begin( __METHOD__ );
2775                 $args = func_get_args();
2776                 $function = array_shift( $args );
2777                 $oldIgnore = $this->ignoreErrors( true );
2778                 $tries = DEADLOCK_TRIES;
2779
2780                 if ( is_array( $function ) ) {
2781                         $fname = $function[0];
2782                 } else {
2783                         $fname = $function;
2784                 }
2785
2786                 do {
2787                         $retVal = call_user_func_array( $function, $args );
2788                         $error = $this->lastError();
2789                         $errno = $this->lastErrno();
2790                         $sql = $this->lastQuery();
2791
2792                         if ( $errno ) {
2793                                 if ( $this->wasDeadlock() ) {
2794                                         # Retry
2795                                         usleep( mt_rand( DEADLOCK_DELAY_MIN, DEADLOCK_DELAY_MAX ) );
2796                                 } else {
2797                                         $this->reportQueryError( $error, $errno, $sql, $fname );
2798                                 }
2799                         }
2800                 } while ( $this->wasDeadlock() && --$tries > 0 );
2801
2802                 $this->ignoreErrors( $oldIgnore );
2803
2804                 if ( $tries <= 0 ) {
2805                         $this->rollback( __METHOD__ );
2806                         $this->reportQueryError( $error, $errno, $sql, $fname );
2807                         return false;
2808                 } else {
2809                         $this->commit( __METHOD__ );
2810                         return $retVal;
2811                 }
2812         }
2813
2814         /**
2815          * Wait for the slave to catch up to a given master position.
2816          *
2817          * @param $pos DBMasterPos object
2818          * @param $timeout Integer: the maximum number of seconds to wait for
2819          *   synchronisation
2820          *
2821          * @return integer: zero if the slave was past that position already,
2822          *   greater than zero if we waited for some period of time, less than
2823          *   zero if we timed out.
2824          */
2825         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2826                 wfProfileIn( __METHOD__ );
2827
2828                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2829                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
2830
2831                         if ( $wait > $timeout * 1e6 ) {
2832                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
2833                                 wfProfileOut( __METHOD__ );
2834                                 return -1;
2835                         } elseif ( $wait > 0 ) {
2836                                 wfDebug( "Fake slave waiting $wait us\n" );
2837                                 usleep( $wait );
2838                                 wfProfileOut( __METHOD__ );
2839                                 return 1;
2840                         } else {
2841                                 wfDebug( "Fake slave up to date ($wait us)\n" );
2842                                 wfProfileOut( __METHOD__ );
2843                                 return 0;
2844                         }
2845                 }
2846
2847                 wfProfileOut( __METHOD__ );
2848
2849                 # Real waits are implemented in the subclass.
2850                 return 0;
2851         }
2852
2853         /**
2854          * Get the replication position of this slave
2855          *
2856          * @return DBMasterPos, or false if this is not a slave.
2857          */
2858         public function getSlavePos() {
2859                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2860                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
2861                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
2862                         return $pos;
2863                 } else {
2864                         # Stub
2865                         return false;
2866                 }
2867         }
2868
2869         /**
2870          * Get the position of this master
2871          *
2872          * @return DBMasterPos, or false if this is not a master
2873          */
2874         public function getMasterPos() {
2875                 if ( $this->mFakeMaster ) {
2876                         return new MySQLMasterPos( 'fake', microtime( true ) );
2877                 } else {
2878                         return false;
2879                 }
2880         }
2881
2882         /**
2883          * Run an anonymous function as soon as there is no transaction pending.
2884          * If there is a transaction and it is rolled back, then the callback is cancelled.
2885          * Callbacks must commit any transactions that they begin.
2886          *
2887          * This is useful for updates to different systems or separate transactions are needed.
2888          *
2889          * @since 1.20
2890          *
2891          * @param Closure $callback
2892          */
2893         final public function onTransactionIdle( Closure $callback ) {
2894                 if ( $this->mTrxLevel ) {
2895                         $this->trxIdleCallbacks[] = $callback;
2896                 } else {
2897                         $callback();
2898                 }
2899         }
2900
2901         /**
2902          * Actually run the "on transaction idle" callbacks.
2903          *
2904          * @since 1.20
2905          */
2906         protected function runOnTransactionIdleCallbacks() {
2907                 $e = null; // last exception
2908                 do { // callbacks may add callbacks :)
2909                         $callbacks = $this->trxIdleCallbacks;
2910                         $this->trxIdleCallbacks = array(); // recursion guard
2911                         foreach ( $callbacks as $callback ) {
2912                                 try {
2913                                         $callback();
2914                                 } catch ( Exception $e ) {}
2915                         }
2916                 } while ( count( $this->trxIdleCallbacks ) );
2917
2918                 if ( $e instanceof Exception ) {
2919                         throw $e; // re-throw any last exception
2920                 }
2921         }
2922
2923         /**
2924          * Begin a transaction. If a transaction is already in progress, that transaction will be committed before the
2925          * new transaction is started.
2926          *
2927          * Note that when the DBO_TRX flag is set (which is usually the case for web requests, but not for maintenance scripts),
2928          * any previous database query will have started a transaction automatically.
2929          *
2930          * Nesting of transactions is not supported. Attempts to nest transactions will cause a warning, unless the current
2931          * transaction was started automatically because of the DBO_TRX flag.
2932          *
2933          * @param $fname string
2934          */
2935         final public function begin( $fname = 'DatabaseBase::begin' ) {
2936                 global $wgDebugDBTransactions;
2937
2938                 if ( $this->mTrxLevel ) { // implicit commit
2939                         if ( !$this->mTrxAutomatic ) {
2940                                 // We want to warn about inadvertently nested begin/commit pairs, but not about auto-committing
2941                                 // implicit transactions that were started by query() because DBO_TRX was set.
2942
2943                                 wfWarn( "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
2944                                         " performing implicit commit!" );
2945                         } else {
2946                                 // if the transaction was automatic and has done write operations,
2947                                 // log it if $wgDebugDBTransactions is enabled.
2948
2949                                 if ( $this->mTrxDoneWrites && $wgDebugDBTransactions ) {
2950                                         wfDebug( "$fname: Automatic transaction with writes in progress (from {$this->mTrxFname}), " .
2951                                                 " performing implicit commit!\n" );
2952                                 }
2953                         }
2954
2955                         $this->doCommit( $fname );
2956                         $this->runOnTransactionIdleCallbacks();
2957                 }
2958
2959                 $this->doBegin( $fname );
2960                 $this->mTrxFname = $fname;
2961                 $this->mTrxDoneWrites = false;
2962                 $this->mTrxAutomatic = false;
2963         }
2964
2965         /**
2966          * Issues the BEGIN command to the database server.
2967          *
2968          * @see DatabaseBase::begin()
2969          * @param type $fname
2970          */
2971         protected function doBegin( $fname ) {
2972                 $this->query( 'BEGIN', $fname );
2973                 $this->mTrxLevel = 1;
2974         }
2975
2976         /**
2977          * Commits a transaction previously started using begin().
2978          * If no transaction is in progress, a warning is issued.
2979          *
2980          * Nesting of transactions is not supported.
2981          *
2982          * @param $fname string
2983          * @param $suppressWarnings bool Suppress any warnings about open transactions (default_ false).
2984          *        Only set this if you are absolutely sure that it is safe to ignore these warnings in your context.
2985          */
2986         final public function commit( $fname = 'DatabaseBase::commit', $suppressWarnings = false ) {
2987                 if ( !$suppressWarnings ) {
2988                         if ( !$this->mTrxLevel ) {
2989                                 wfWarn( "$fname: No transaction to commit, something got out of sync!" );
2990                         } elseif( $this->mTrxAutomatic ) {
2991                                 wfWarn( "$fname: Explicit commit of implicit transaction. Something may be out of sync!" );
2992                         }
2993                 }
2994
2995                 $this->doCommit( $fname );
2996                 $this->runOnTransactionIdleCallbacks();
2997         }
2998
2999         /**
3000          * Issues the COMMIT command to the database server.
3001          *
3002          * @see DatabaseBase::commit()
3003          * @param type $fname
3004          */
3005         protected function doCommit( $fname ) {
3006                 if ( $this->mTrxLevel ) {
3007                         $this->query( 'COMMIT', $fname );
3008                         $this->mTrxLevel = 0;
3009                 }
3010         }
3011
3012         /**
3013          * Rollback a transaction previously started using begin().
3014          * If no transaction is in progress, a warning is issued.
3015          *
3016          * No-op on non-transactional databases.
3017          *
3018          * @param $fname string
3019          */
3020         final public function rollback( $fname = 'DatabaseBase::rollback' ) {
3021                 if ( !$this->mTrxLevel ) {
3022                         wfWarn( "$fname: No transaction to rollback, something got out of sync!" );
3023                 }
3024                 $this->doRollback( $fname );
3025                 $this->trxIdleCallbacks = array(); // cancel
3026         }
3027
3028         /**
3029          * Issues the ROLLBACK command to the database server.
3030          *
3031          * @see DatabaseBase::rollback()
3032          * @param type $fname
3033          */
3034         protected function doRollback( $fname ) {
3035                 if ( $this->mTrxLevel ) {
3036                         $this->query( 'ROLLBACK', $fname, true );
3037                         $this->mTrxLevel = 0;
3038                 }
3039         }
3040
3041         /**
3042          * Creates a new table with structure copied from existing table
3043          * Note that unlike most database abstraction functions, this function does not
3044          * automatically append database prefix, because it works at a lower
3045          * abstraction level.
3046          * The table names passed to this function shall not be quoted (this
3047          * function calls addIdentifierQuotes when needed).
3048          *
3049          * @param $oldName String: name of table whose structure should be copied
3050          * @param $newName String: name of table to be created
3051          * @param $temporary Boolean: whether the new table should be temporary
3052          * @param $fname String: calling function name
3053          * @throws MWException
3054          * @return Boolean: true if operation was successful
3055          */
3056         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3057                 $fname = 'DatabaseBase::duplicateTableStructure' )
3058         {
3059                 throw new MWException(
3060                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3061         }
3062
3063         /**
3064          * List all tables on the database
3065          *
3066          * @param $prefix string Only show tables with this prefix, e.g. mw_
3067          * @param $fname String: calling function name
3068          * @throws MWException
3069          */
3070         function listTables( $prefix = null, $fname = 'DatabaseBase::listTables' ) {
3071                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3072         }
3073
3074         /**
3075          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3076          * to the format used for inserting into timestamp fields in this DBMS.
3077          *
3078          * The result is unquoted, and needs to be passed through addQuotes()
3079          * before it can be included in raw SQL.
3080          *
3081          * @param $ts string|int
3082          *
3083          * @return string
3084          */
3085         public function timestamp( $ts = 0 ) {
3086                 return wfTimestamp( TS_MW, $ts );
3087         }
3088
3089         /**
3090          * Convert a timestamp in one of the formats accepted by wfTimestamp()
3091          * to the format used for inserting into timestamp fields in this DBMS. If
3092          * NULL is input, it is passed through, allowing NULL values to be inserted
3093          * into timestamp fields.
3094          *
3095          * The result is unquoted, and needs to be passed through addQuotes()
3096          * before it can be included in raw SQL.
3097          *
3098          * @param $ts string|int
3099          *
3100          * @return string
3101          */
3102         public function timestampOrNull( $ts = null ) {
3103                 if ( is_null( $ts ) ) {
3104                         return null;
3105                 } else {
3106                         return $this->timestamp( $ts );
3107                 }
3108         }
3109
3110         /**
3111          * Take the result from a query, and wrap it in a ResultWrapper if
3112          * necessary. Boolean values are passed through as is, to indicate success
3113          * of write queries or failure.
3114          *
3115          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3116          * resource, and it was necessary to call this function to convert it to
3117          * a wrapper. Nowadays, raw database objects are never exposed to external
3118          * callers, so this is unnecessary in external code. For compatibility with
3119          * old code, ResultWrapper objects are passed through unaltered.
3120          *
3121          * @param $result bool|ResultWrapper
3122          *
3123          * @return bool|ResultWrapper
3124          */
3125         public function resultObject( $result ) {
3126                 if ( empty( $result ) ) {
3127                         return false;
3128                 } elseif ( $result instanceof ResultWrapper ) {
3129                         return $result;
3130                 } elseif ( $result === true ) {
3131                         // Successful write query
3132                         return $result;
3133                 } else {
3134                         return new ResultWrapper( $this, $result );
3135                 }
3136         }
3137
3138         /**
3139          * Ping the server and try to reconnect if it there is no connection
3140          *
3141          * @return bool Success or failure
3142          */
3143         public function ping() {
3144                 # Stub.  Not essential to override.
3145                 return true;
3146         }
3147
3148         /**
3149          * Get slave lag. Currently supported only by MySQL.
3150          *
3151          * Note that this function will generate a fatal error on many
3152          * installations. Most callers should use LoadBalancer::safeGetLag()
3153          * instead.
3154          *
3155          * @return int Database replication lag in seconds
3156          */
3157         public function getLag() {
3158                 return intval( $this->mFakeSlaveLag );
3159         }
3160
3161         /**
3162          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3163          *
3164          * @return int
3165          */
3166         function maxListLen() {
3167                 return 0;
3168         }
3169
3170         /**
3171          * Some DBMSs have a special format for inserting into blob fields, they
3172          * don't allow simple quoted strings to be inserted. To insert into such
3173          * a field, pass the data through this function before passing it to
3174          * DatabaseBase::insert().
3175          * @param $b string
3176          * @return string
3177          */
3178         public function encodeBlob( $b ) {
3179                 return $b;
3180         }
3181
3182         /**
3183          * Some DBMSs return a special placeholder object representing blob fields
3184          * in result objects. Pass the object through this function to return the
3185          * original string.
3186          * @param $b string
3187          * @return string
3188          */
3189         public function decodeBlob( $b ) {
3190                 return $b;
3191         }
3192
3193         /**
3194          * Override database's default behavior. $options include:
3195          *     'connTimeout' : Set the connection timeout value in seconds.
3196          *                     May be useful for very long batch queries such as
3197          *                     full-wiki dumps, where a single query reads out over
3198          *                     hours or days.
3199          *
3200          * @param $options Array
3201          * @return void
3202          */
3203         public function setSessionOptions( array $options ) {}
3204
3205         /**
3206          * Read and execute SQL commands from a file.
3207          *
3208          * Returns true on success, error string or exception on failure (depending
3209          * on object's error ignore settings).
3210          *
3211          * @param $filename String: File name to open
3212          * @param bool|callable $lineCallback Optional function called before reading each line
3213          * @param bool|callable $resultCallback Optional function called for each MySQL result
3214          * @param bool|string $fname Calling function name or false if name should be
3215          *      generated dynamically using $filename
3216          * @throws MWException
3217          * @return bool|string
3218          */
3219         public function sourceFile(
3220                 $filename, $lineCallback = false, $resultCallback = false, $fname = false
3221         ) {
3222                 wfSuppressWarnings();
3223                 $fp = fopen( $filename, 'r' );
3224                 wfRestoreWarnings();
3225
3226                 if ( false === $fp ) {
3227                         throw new MWException( "Could not open \"{$filename}\".\n" );
3228                 }
3229
3230                 if ( !$fname ) {
3231                         $fname = __METHOD__ . "( $filename )";
3232                 }
3233
3234                 try {
3235                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname );
3236                 }
3237                 catch ( MWException $e ) {
3238                         fclose( $fp );
3239                         throw $e;
3240                 }
3241
3242                 fclose( $fp );
3243
3244                 return $error;
3245         }
3246
3247         /**
3248          * Get the full path of a patch file. Originally based on archive()
3249          * from updaters.inc. Keep in mind this always returns a patch, as
3250          * it fails back to MySQL if no DB-specific patch can be found
3251          *
3252          * @param $patch String The name of the patch, like patch-something.sql
3253          * @return String Full path to patch file
3254          */
3255         public function patchPath( $patch ) {
3256                 global $IP;
3257
3258                 $dbType = $this->getType();
3259                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3260                         return "$IP/maintenance/$dbType/archives/$patch";
3261                 } else {
3262                         return "$IP/maintenance/archives/$patch";
3263                 }
3264         }
3265
3266         /**
3267          * Set variables to be used in sourceFile/sourceStream, in preference to the
3268          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3269          * all. If it's set to false, $GLOBALS will be used.
3270          *
3271          * @param $vars bool|array mapping variable name to value.
3272          */
3273         public function setSchemaVars( $vars ) {
3274                 $this->mSchemaVars = $vars;
3275         }
3276
3277         /**
3278          * Read and execute commands from an open file handle.
3279          *
3280          * Returns true on success, error string or exception on failure (depending
3281          * on object's error ignore settings).
3282          *
3283          * @param $fp Resource: File handle
3284          * @param $lineCallback Callback: Optional function called before reading each line
3285          * @param $resultCallback Callback: Optional function called for each MySQL result
3286          * @param $fname String: Calling function name
3287          * @param $inputCallback Callback: Optional function called for each complete line (ended with ;) sent
3288          * @return bool|string
3289          */
3290         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3291                 $fname = 'DatabaseBase::sourceStream', $inputCallback = false )
3292         {
3293                 $cmd = '';
3294
3295                 while ( !feof( $fp ) ) {
3296                         if ( $lineCallback ) {
3297                                 call_user_func( $lineCallback );
3298                         }
3299
3300                         $line = trim( fgets( $fp ) );
3301
3302                         if ( $line == '' ) {
3303                                 continue;
3304                         }
3305
3306                         if ( '-' == $line[0] && '-' == $line[1] ) {
3307                                 continue;
3308                         }
3309
3310                         if ( $cmd != '' ) {
3311                                 $cmd .= ' ';
3312                         }
3313
3314                         $done = $this->streamStatementEnd( $cmd, $line );
3315
3316                         $cmd .= "$line\n";
3317
3318                         if ( $done || feof( $fp ) ) {
3319                                 $cmd = $this->replaceVars( $cmd );
3320                                 if ( $inputCallback ) {
3321                                         call_user_func( $inputCallback, $cmd );
3322                                 }
3323                                 $res = $this->query( $cmd, $fname );
3324
3325                                 if ( $resultCallback ) {
3326                                         call_user_func( $resultCallback, $res, $this );
3327                                 }
3328
3329                                 if ( false === $res ) {
3330                                         $err = $this->lastError();
3331                                         return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3332                                 }
3333
3334                                 $cmd = '';
3335                         }
3336                 }
3337
3338                 return true;
3339         }
3340
3341         /**
3342          * Called by sourceStream() to check if we've reached a statement end
3343          *
3344          * @param $sql String SQL assembled so far
3345          * @param $newLine String New line about to be added to $sql
3346          * @return Bool Whether $newLine contains end of the statement
3347          */
3348         public function streamStatementEnd( &$sql, &$newLine ) {
3349                 if ( $this->delimiter ) {
3350                         $prev = $newLine;
3351                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3352                         if ( $newLine != $prev ) {
3353                                 return true;
3354                         }
3355                 }
3356                 return false;
3357         }
3358
3359         /**
3360          * Database independent variable replacement. Replaces a set of variables
3361          * in an SQL statement with their contents as given by $this->getSchemaVars().
3362          *
3363          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3364          *
3365          * - '{$var}' should be used for text and is passed through the database's
3366          *   addQuotes method.
3367          * - `{$var}` should be used for identifiers (eg: table and database names),
3368          *   it is passed through the database's addIdentifierQuotes method which
3369          *   can be overridden if the database uses something other than backticks.
3370          * - / *$var* / is just encoded, besides traditional table prefix and
3371          *   table options its use should be avoided.
3372          *
3373          * @param $ins String: SQL statement to replace variables in
3374          * @return String The new SQL statement with variables replaced
3375          */
3376         protected function replaceSchemaVars( $ins ) {
3377                 $vars = $this->getSchemaVars();
3378                 foreach ( $vars as $var => $value ) {
3379                         // replace '{$var}'
3380                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3381                         // replace `{$var}`
3382                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3383                         // replace /*$var*/
3384                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ) , $ins );
3385                 }
3386                 return $ins;
3387         }
3388
3389         /**
3390          * Replace variables in sourced SQL
3391          *
3392          * @param $ins string
3393          *
3394          * @return string
3395          */
3396         protected function replaceVars( $ins ) {
3397                 $ins = $this->replaceSchemaVars( $ins );
3398
3399                 // Table prefixes
3400                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3401                         array( $this, 'tableNameCallback' ), $ins );
3402
3403                 // Index names
3404                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3405                         array( $this, 'indexNameCallback' ), $ins );
3406
3407                 return $ins;
3408         }
3409
3410         /**
3411          * Get schema variables. If none have been set via setSchemaVars(), then
3412          * use some defaults from the current object.
3413          *
3414          * @return array
3415          */
3416         protected function getSchemaVars() {
3417                 if ( $this->mSchemaVars ) {
3418                         return $this->mSchemaVars;
3419                 } else {
3420                         return $this->getDefaultSchemaVars();
3421                 }
3422         }
3423
3424         /**
3425          * Get schema variables to use if none have been set via setSchemaVars().
3426          *
3427          * Override this in derived classes to provide variables for tables.sql
3428          * and SQL patch files.
3429          *
3430          * @return array
3431          */
3432         protected function getDefaultSchemaVars() {
3433                 return array();
3434         }
3435
3436         /**
3437          * Table name callback
3438          *
3439          * @param $matches array
3440          *
3441          * @return string
3442          */
3443         protected function tableNameCallback( $matches ) {
3444                 return $this->tableName( $matches[1] );
3445         }
3446
3447         /**
3448          * Index name callback
3449          *
3450          * @param $matches array
3451          *
3452          * @return string
3453          */
3454         protected function indexNameCallback( $matches ) {
3455                 return $this->indexName( $matches[1] );
3456         }
3457
3458         /**
3459          * Check to see if a named lock is available. This is non-blocking.
3460          *
3461          * @param $lockName String: name of lock to poll
3462          * @param $method String: name of method calling us
3463          * @return Boolean
3464          * @since 1.20
3465          */
3466         public function lockIsFree( $lockName, $method ) {
3467                 return true;
3468         }
3469
3470         /**
3471          * Acquire a named lock
3472          *
3473          * Abstracted from Filestore::lock() so child classes can implement for
3474          * their own needs.
3475          *
3476          * @param $lockName String: name of lock to aquire
3477          * @param $method String: name of method calling us
3478          * @param $timeout Integer: timeout
3479          * @return Boolean
3480          */
3481         public function lock( $lockName, $method, $timeout = 5 ) {
3482                 return true;
3483         }
3484
3485         /**
3486          * Release a lock.
3487          *
3488          * @param $lockName String: Name of lock to release
3489          * @param $method String: Name of method calling us
3490          *
3491          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3492          * by this thread (in which case the lock is not released), and NULL if the named
3493          * lock did not exist
3494          */
3495         public function unlock( $lockName, $method ) {
3496                 return true;
3497         }
3498
3499         /**
3500          * Lock specific tables
3501          *
3502          * @param $read Array of tables to lock for read access
3503          * @param $write Array of tables to lock for write access
3504          * @param $method String name of caller
3505          * @param $lowPriority bool Whether to indicate writes to be LOW PRIORITY
3506          *
3507          * @return bool
3508          */
3509         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3510                 return true;
3511         }
3512
3513         /**
3514          * Unlock specific tables
3515          *
3516          * @param $method String the caller
3517          *
3518          * @return bool
3519          */
3520         public function unlockTables( $method ) {
3521                 return true;
3522         }
3523
3524         /**
3525          * Delete a table
3526          * @param $tableName string
3527          * @param $fName string
3528          * @return bool|ResultWrapper
3529          * @since 1.18
3530          */
3531         public function dropTable( $tableName, $fName = 'DatabaseBase::dropTable' ) {
3532                 if( !$this->tableExists( $tableName, $fName ) ) {
3533                         return false;
3534                 }
3535                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3536                 if( $this->cascadingDeletes() ) {
3537                         $sql .= " CASCADE";
3538                 }
3539                 return $this->query( $sql, $fName );
3540         }
3541
3542         /**
3543          * Get search engine class. All subclasses of this need to implement this
3544          * if they wish to use searching.
3545          *
3546          * @return String
3547          */
3548         public function getSearchEngine() {
3549                 return 'SearchEngineDummy';
3550         }
3551
3552         /**
3553          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3554          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3555          * because "i" sorts after all numbers.
3556          *
3557          * @return String
3558          */
3559         public function getInfinity() {
3560                 return 'infinity';
3561         }
3562
3563         /**
3564          * Encode an expiry time into the DBMS dependent format
3565          *
3566          * @param $expiry String: timestamp for expiry, or the 'infinity' string
3567          * @return String
3568          */
3569         public function encodeExpiry( $expiry ) {
3570                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3571                         ? $this->getInfinity()
3572                         : $this->timestamp( $expiry );
3573         }
3574
3575         /**
3576          * Decode an expiry time into a DBMS independent format
3577          *
3578          * @param $expiry String: DB timestamp field value for expiry
3579          * @param $format integer: TS_* constant, defaults to TS_MW
3580          * @return String
3581          */
3582         public function decodeExpiry( $expiry, $format = TS_MW ) {
3583                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3584                         ? 'infinity'
3585                         : wfTimestamp( $format, $expiry );
3586         }
3587
3588         /**
3589          * Allow or deny "big selects" for this session only. This is done by setting
3590          * the sql_big_selects session variable.
3591          *
3592          * This is a MySQL-specific feature.
3593          *
3594          * @param $value Mixed: true for allow, false for deny, or "default" to
3595          *   restore the initial value
3596          */
3597         public function setBigSelects( $value = true ) {
3598                 // no-op
3599         }
3600
3601         /**
3602          * @since 1.19
3603          */
3604         public function __toString() {
3605                 return (string)$this->mConn;
3606         }
3607 }