includes/libs/rdbms/database/DatabaseMysqlBase.php

   1 <?php
   2 /**
   3  * This is the MySQL database abstraction layer.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Database
  22  */
  23 namespace Wikimedia\Rdbms;
  24
  25 use DateTime;
  26 use DateTimeZone;
  27 use MediaWiki;
  28 use InvalidArgumentException;
  29 use Exception;
  30 use stdClass;
  31
  32 /**
  33  * Database abstraction object for MySQL.
  34  * Defines methods independent on used MySQL extension.
  35  *
  36  * @ingroup Database
  37  * @since 1.22
  38  * @see Database
  39  */
  40 abstract class DatabaseMysqlBase extends Database {
  41         /** @var MysqlMasterPos */
  42         protected $lastKnownReplicaPos;
  43         /** @var string Method to detect replica DB lag */
  44         protected $lagDetectionMethod;
  45         /** @var array Method to detect replica DB lag */
  46         protected $lagDetectionOptions = [];
  47         /** @var bool bool Whether to use GTID methods */
  48         protected $useGTIDs = false;
  49         /** @var string|null */
  50         protected $sslKeyPath;
  51         /** @var string|null */
  52         protected $sslCertPath;
  53         /** @var string|null */
  54         protected $sslCAFile;
  55         /** @var string|null */
  56         protected $sslCAPath;
  57         /** @var string[]|null */
  58         protected $sslCiphers;
  59         /** @var string sql_mode value to send on connection */
  60         protected $sqlMode;
  61         /** @var bool Use experimental UTF-8 transmission encoding */
  62         protected $utf8Mode;
  63
  64         /** @var string|null */
  65         private $serverVersion = null;
  66
  67         /**
  68          * Additional $params include:
  69          *   - lagDetectionMethod : set to one of (Seconds_Behind_Master,pt-heartbeat).
  70          *       pt-heartbeat assumes the table is at heartbeat.heartbeat
  71          *       and uses UTC timestamps in the heartbeat.ts column.
  72          *       (https://www.percona.com/doc/percona-toolkit/2.2/pt-heartbeat.html)
  73          *   - lagDetectionOptions : if using pt-heartbeat, this can be set to an array map to change
  74          *       the default behavior. Normally, the heartbeat row with the server
  75          *       ID of this server's master will be used. Set the "conds" field to
  76          *       override the query conditions, e.g. ['shard' => 's1'].
  77          *   - useGTIDs : use GTID methods like MASTER_GTID_WAIT() when possible.
  78          *   - sslKeyPath : path to key file [default: null]
  79          *   - sslCertPath : path to certificate file [default: null]
  80          *   - sslCAFile: path to a single certificate authority PEM file [default: null]
  81          *   - sslCAPath : parth to certificate authority PEM directory [default: null]
  82          *   - sslCiphers : array list of allowable ciphers [default: null]
  83          * @param array $params
  84          */
  85         function __construct( array $params ) {
  86                 $this->lagDetectionMethod = isset( $params['lagDetectionMethod'] )
  87                         ? $params['lagDetectionMethod']
  88                         : 'Seconds_Behind_Master';
  89                 $this->lagDetectionOptions = isset( $params['lagDetectionOptions'] )
  90                         ? $params['lagDetectionOptions']
  91                         : [];
  92                 $this->useGTIDs = !empty( $params['useGTIDs' ] );
  93                 foreach ( [ 'KeyPath', 'CertPath', 'CAFile', 'CAPath', 'Ciphers' ] as $name ) {
  94                         $var = "ssl{$name}";
  95                         if ( isset( $params[$var] ) ) {
  96                                 $this->$var = $params[$var];
  97                         }
  98                 }
  99                 $this->sqlMode = isset( $params['sqlMode'] ) ? $params['sqlMode'] : '';
 100                 $this->utf8Mode = !empty( $params['utf8Mode'] );
 101
 102                 parent::__construct( $params );
 103         }
 104
 105         /**
 106          * @return string
 107          */
 108         public function getType() {
 109                 return 'mysql';
 110         }
 111
 112         /**
 113          * @param string $server
 114          * @param string $user
 115          * @param string $password
 116          * @param string $dbName
 117          * @throws Exception|DBConnectionError
 118          * @return bool
 119          */
 120         public function open( $server, $user, $password, $dbName ) {
 121                 # Close/unset connection handle
 122                 $this->close();
 123
 124                 $this->mServer = $server;
 125                 $this->mUser = $user;
 126                 $this->mPassword = $password;
 127                 $this->mDBname = $dbName;
 128
 129                 $this->installErrorHandler();
 130                 try {
 131                         $this->mConn = $this->mysqlConnect( $this->mServer );
 132                 } catch ( Exception $ex ) {
 133                         $this->restoreErrorHandler();
 134                         throw $ex;
 135                 }
 136                 $error = $this->restoreErrorHandler();
 137
 138                 # Always log connection errors
 139                 if ( !$this->mConn ) {
 140                         if ( !$error ) {
 141                                 $error = $this->lastError();
 142                         }
 143                         $this->connLogger->error(
 144                                 "Error connecting to {db_server}: {error}",
 145                                 $this->getLogContext( [
 146                                         'method' => __METHOD__,
 147                                         'error' => $error,
 148                                 ] )
 149                         );
 150                         $this->connLogger->debug( "DB connection error\n" .
 151                                 "Server: $server, User: $user, Password: " .
 152                                 substr( $password, 0, 3 ) . "..., error: " . $error . "\n" );
 153
 154                         $this->reportConnectionError( $error );
 155                 }
 156
 157                 if ( $dbName != '' ) {
 158                         MediaWiki\suppressWarnings();
 159                         $success = $this->selectDB( $dbName );
 160                         MediaWiki\restoreWarnings();
 161                         if ( !$success ) {
 162                                 $this->queryLogger->error(
 163                                         "Error selecting database {db_name} on server {db_server}",
 164                                         $this->getLogContext( [
 165                                                 'method' => __METHOD__,
 166                                         ] )
 167                                 );
 168                                 $this->queryLogger->debug(
 169                                         "Error selecting database $dbName on server {$this->mServer}" );
 170
 171                                 $this->reportConnectionError( "Error selecting database $dbName" );
 172                         }
 173                 }
 174
 175                 // Tell the server what we're communicating with
 176                 if ( !$this->connectInitCharset() ) {
 177                         $this->reportConnectionError( "Error setting character set" );
 178                 }
 179
 180                 // Abstract over any insane MySQL defaults
 181                 $set = [ 'group_concat_max_len = 262144' ];
 182                 // Set SQL mode, default is turning them all off, can be overridden or skipped with null
 183                 if ( is_string( $this->sqlMode ) ) {
 184                         $set[] = 'sql_mode = ' . $this->addQuotes( $this->sqlMode );
 185                 }
 186                 // Set any custom settings defined by site config
 187                 // (e.g. https://dev.mysql.com/doc/refman/4.1/en/innodb-parameters.html)
 188                 foreach ( $this->mSessionVars as $var => $val ) {
 189                         // Escape strings but not numbers to avoid MySQL complaining
 190                         if ( !is_int( $val ) && !is_float( $val ) ) {
 191                                 $val = $this->addQuotes( $val );
 192                         }
 193                         $set[] = $this->addIdentifierQuotes( $var ) . ' = ' . $val;
 194                 }
 195
 196                 if ( $set ) {
 197                         // Use doQuery() to avoid opening implicit transactions (DBO_TRX)
 198                         $success = $this->doQuery( 'SET ' . implode( ', ', $set ) );
 199                         if ( !$success ) {
 200                                 $this->queryLogger->error(
 201                                         'Error setting MySQL variables on server {db_server} (check $wgSQLMode)',
 202                                         $this->getLogContext( [
 203                                                 'method' => __METHOD__,
 204                                         ] )
 205                                 );
 206                                 $this->reportConnectionError(
 207                                         'Error setting MySQL variables on server {db_server} (check $wgSQLMode)' );
 208                         }
 209                 }
 210
 211                 $this->mOpened = true;
 212
 213                 return true;
 214         }
 215
 216         /**
 217          * Set the character set information right after connection
 218          * @return bool
 219          */
 220         protected function connectInitCharset() {
 221                 if ( $this->utf8Mode ) {
 222                         // Tell the server we're communicating with it in UTF-8.
 223                         // This may engage various charset conversions.
 224                         return $this->mysqlSetCharset( 'utf8' );
 225                 } else {
 226                         return $this->mysqlSetCharset( 'binary' );
 227                 }
 228         }
 229
 230         /**
 231          * Open a connection to a MySQL server
 232          *
 233          * @param string $realServer
 234          * @return mixed Raw connection
 235          * @throws DBConnectionError
 236          */
 237         abstract protected function mysqlConnect( $realServer );
 238
 239         /**
 240          * Set the character set of the MySQL link
 241          *
 242          * @param string $charset
 243          * @return bool
 244          */
 245         abstract protected function mysqlSetCharset( $charset );
 246
 247         /**
 248          * @param ResultWrapper|resource $res
 249          * @throws DBUnexpectedError
 250          */
 251         public function freeResult( $res ) {
 252                 if ( $res instanceof ResultWrapper ) {
 253                         $res = $res->result;
 254                 }
 255                 MediaWiki\suppressWarnings();
 256                 $ok = $this->mysqlFreeResult( $res );
 257                 MediaWiki\restoreWarnings();
 258                 if ( !$ok ) {
 259                         throw new DBUnexpectedError( $this, "Unable to free MySQL result" );
 260                 }
 261         }
 262
 263         /**
 264          * Free result memory
 265          *
 266          * @param resource $res Raw result
 267          * @return bool
 268          */
 269         abstract protected function mysqlFreeResult( $res );
 270
 271         /**
 272          * @param ResultWrapper|resource $res
 273          * @return stdClass|bool
 274          * @throws DBUnexpectedError
 275          */
 276         public function fetchObject( $res ) {
 277                 if ( $res instanceof ResultWrapper ) {
 278                         $res = $res->result;
 279                 }
 280                 MediaWiki\suppressWarnings();
 281                 $row = $this->mysqlFetchObject( $res );
 282                 MediaWiki\restoreWarnings();
 283
 284                 $errno = $this->lastErrno();
 285                 // Unfortunately, mysql_fetch_object does not reset the last errno.
 286                 // Only check for CR_SERVER_LOST and CR_UNKNOWN_ERROR, as
 287                 // these are the only errors mysql_fetch_object can cause.
 288                 // See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
 289                 if ( $errno == 2000 || $errno == 2013 ) {
 290                         throw new DBUnexpectedError(
 291                                 $this,
 292                                 'Error in fetchObject(): ' . htmlspecialchars( $this->lastError() )
 293                         );
 294                 }
 295
 296                 return $row;
 297         }
 298
 299         /**
 300          * Fetch a result row as an object
 301          *
 302          * @param resource $res Raw result
 303          * @return stdClass
 304          */
 305         abstract protected function mysqlFetchObject( $res );
 306
 307         /**
 308          * @param ResultWrapper|resource $res
 309          * @return array|bool
 310          * @throws DBUnexpectedError
 311          */
 312         public function fetchRow( $res ) {
 313                 if ( $res instanceof ResultWrapper ) {
 314                         $res = $res->result;
 315                 }
 316                 MediaWiki\suppressWarnings();
 317                 $row = $this->mysqlFetchArray( $res );
 318                 MediaWiki\restoreWarnings();
 319
 320                 $errno = $this->lastErrno();
 321                 // Unfortunately, mysql_fetch_array does not reset the last errno.
 322                 // Only check for CR_SERVER_LOST and CR_UNKNOWN_ERROR, as
 323                 // these are the only errors mysql_fetch_array can cause.
 324                 // See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
 325                 if ( $errno == 2000 || $errno == 2013 ) {
 326                         throw new DBUnexpectedError(
 327                                 $this,
 328                                 'Error in fetchRow(): ' . htmlspecialchars( $this->lastError() )
 329                         );
 330                 }
 331
 332                 return $row;
 333         }
 334
 335         /**
 336          * Fetch a result row as an associative and numeric array
 337          *
 338          * @param resource $res Raw result
 339          * @return array
 340          */
 341         abstract protected function mysqlFetchArray( $res );
 342
 343         /**
 344          * @throws DBUnexpectedError
 345          * @param ResultWrapper|resource $res
 346          * @return int
 347          */
 348         function numRows( $res ) {
 349                 if ( $res instanceof ResultWrapper ) {
 350                         $res = $res->result;
 351                 }
 352                 MediaWiki\suppressWarnings();
 353                 $n = $this->mysqlNumRows( $res );
 354                 MediaWiki\restoreWarnings();
 355
 356                 // Unfortunately, mysql_num_rows does not reset the last errno.
 357                 // We are not checking for any errors here, since
 358                 // these are no errors mysql_num_rows can cause.
 359                 // See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
 360                 // See https://phabricator.wikimedia.org/T44430
 361                 return $n;
 362         }
 363
 364         /**
 365          * Get number of rows in result
 366          *
 367          * @param resource $res Raw result
 368          * @return int
 369          */
 370         abstract protected function mysqlNumRows( $res );
 371
 372         /**
 373          * @param ResultWrapper|resource $res
 374          * @return int
 375          */
 376         public function numFields( $res ) {
 377                 if ( $res instanceof ResultWrapper ) {
 378                         $res = $res->result;
 379                 }
 380
 381                 return $this->mysqlNumFields( $res );
 382         }
 383
 384         /**
 385          * Get number of fields in result
 386          *
 387          * @param resource $res Raw result
 388          * @return int
 389          */
 390         abstract protected function mysqlNumFields( $res );
 391
 392         /**
 393          * @param ResultWrapper|resource $res
 394          * @param int $n
 395          * @return string
 396          */
 397         public function fieldName( $res, $n ) {
 398                 if ( $res instanceof ResultWrapper ) {
 399                         $res = $res->result;
 400                 }
 401
 402                 return $this->mysqlFieldName( $res, $n );
 403         }
 404
 405         /**
 406          * Get the name of the specified field in a result
 407          *
 408          * @param ResultWrapper|resource $res
 409          * @param int $n
 410          * @return string
 411          */
 412         abstract protected function mysqlFieldName( $res, $n );
 413
 414         /**
 415          * mysql_field_type() wrapper
 416          * @param ResultWrapper|resource $res
 417          * @param int $n
 418          * @return string
 419          */
 420         public function fieldType( $res, $n ) {
 421                 if ( $res instanceof ResultWrapper ) {
 422                         $res = $res->result;
 423                 }
 424
 425                 return $this->mysqlFieldType( $res, $n );
 426         }
 427
 428         /**
 429          * Get the type of the specified field in a result
 430          *
 431          * @param ResultWrapper|resource $res
 432          * @param int $n
 433          * @return string
 434          */
 435         abstract protected function mysqlFieldType( $res, $n );
 436
 437         /**
 438          * @param ResultWrapper|resource $res
 439          * @param int $row
 440          * @return bool
 441          */
 442         public function dataSeek( $res, $row ) {
 443                 if ( $res instanceof ResultWrapper ) {
 444                         $res = $res->result;
 445                 }
 446
 447                 return $this->mysqlDataSeek( $res, $row );
 448         }
 449
 450         /**
 451          * Move internal result pointer
 452          *
 453          * @param ResultWrapper|resource $res
 454          * @param int $row
 455          * @return bool
 456          */
 457         abstract protected function mysqlDataSeek( $res, $row );
 458
 459         /**
 460          * @return string
 461          */
 462         public function lastError() {
 463                 if ( $this->mConn ) {
 464                         # Even if it's non-zero, it can still be invalid
 465                         MediaWiki\suppressWarnings();
 466                         $error = $this->mysqlError( $this->mConn );
 467                         if ( !$error ) {
 468                                 $error = $this->mysqlError();
 469                         }
 470                         MediaWiki\restoreWarnings();
 471                 } else {
 472                         $error = $this->mysqlError();
 473                 }
 474                 if ( $error ) {
 475                         $error .= ' (' . $this->mServer . ')';
 476                 }
 477
 478                 return $error;
 479         }
 480
 481         /**
 482          * Returns the text of the error message from previous MySQL operation
 483          *
 484          * @param resource $conn Raw connection
 485          * @return string
 486          */
 487         abstract protected function mysqlError( $conn = null );
 488
 489         /**
 490          * @param string $table
 491          * @param array $uniqueIndexes
 492          * @param array $rows
 493          * @param string $fname
 494          * @return ResultWrapper
 495          */
 496         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
 497                 return $this->nativeReplace( $table, $rows, $fname );
 498         }
 499
 500         /**
 501          * Estimate rows in dataset
 502          * Returns estimated count, based on EXPLAIN output
 503          * Takes same arguments as Database::select()
 504          *
 505          * @param string|array $table
 506          * @param string|array $vars
 507          * @param string|array $conds
 508          * @param string $fname
 509          * @param string|array $options
 510          * @return bool|int
 511          */
 512         public function estimateRowCount( $table, $vars = '*', $conds = '',
 513                 $fname = __METHOD__, $options = []
 514         ) {
 515                 $options['EXPLAIN'] = true;
 516                 $res = $this->select( $table, $vars, $conds, $fname, $options );
 517                 if ( $res === false ) {
 518                         return false;
 519                 }
 520                 if ( !$this->numRows( $res ) ) {
 521                         return 0;
 522                 }
 523
 524                 $rows = 1;
 525                 foreach ( $res as $plan ) {
 526                         $rows *= $plan->rows > 0 ? $plan->rows : 1; // avoid resetting to zero
 527                 }
 528
 529                 return (int)$rows;
 530         }
 531
 532         public function tableExists( $table, $fname = __METHOD__ ) {
 533                 // Split database and table into proper variables as Database::tableName() returns
 534                 // shared tables prefixed with their database, which do not work in SHOW TABLES statements
 535                 list( $database, , $prefix, $table ) = $this->qualifiedTableComponents( $table );
 536                 $tableName = "{$prefix}{$table}";
 537
 538                 if ( isset( $this->mSessionTempTables[$tableName] ) ) {
 539                         return true; // already known to exist and won't show in SHOW TABLES anyway
 540                 }
 541
 542                 // We can't use buildLike() here, because it specifies an escape character
 543                 // other than the backslash, which is the only one supported by SHOW TABLES
 544                 $encLike = $this->escapeLikeInternal( $tableName, '\\' );
 545
 546                 // If the database has been specified (such as for shared tables), use "FROM"
 547                 if ( $database !== '' ) {
 548                         $encDatabase = $this->addIdentifierQuotes( $database );
 549                         $query = "SHOW TABLES FROM $encDatabase LIKE '$encLike'";
 550                 } else {
 551                         $query = "SHOW TABLES LIKE '$encLike'";
 552                 }
 553
 554                 return $this->query( $query, $fname )->numRows() > 0;
 555         }
 556
 557         /**
 558          * @param string $table
 559          * @param string $field
 560          * @return bool|MySQLField
 561          */
 562         public function fieldInfo( $table, $field ) {
 563                 $table = $this->tableName( $table );
 564                 $res = $this->query( "SELECT * FROM $table LIMIT 1", __METHOD__, true );
 565                 if ( !$res ) {
 566                         return false;
 567                 }
 568                 $n = $this->mysqlNumFields( $res->result );
 569                 for ( $i = 0; $i < $n; $i++ ) {
 570                         $meta = $this->mysqlFetchField( $res->result, $i );
 571                         if ( $field == $meta->name ) {
 572                                 return new MySQLField( $meta );
 573                         }
 574                 }
 575
 576                 return false;
 577         }
 578
 579         /**
 580          * Get column information from a result
 581          *
 582          * @param resource $res Raw result
 583          * @param int $n
 584          * @return stdClass
 585          */
 586         abstract protected function mysqlFetchField( $res, $n );
 587
 588         /**
 589          * Get information about an index into an object
 590          * Returns false if the index does not exist
 591          *
 592          * @param string $table
 593          * @param string $index
 594          * @param string $fname
 595          * @return bool|array|null False or null on failure
 596          */
 597         public function indexInfo( $table, $index, $fname = __METHOD__ ) {
 598                 # SHOW INDEX works in MySQL 3.23.58, but SHOW INDEXES does not.
 599                 # SHOW INDEX should work for 3.x and up:
 600                 # https://dev.mysql.com/doc/mysql/en/SHOW_INDEX.html
 601                 $table = $this->tableName( $table );
 602                 $index = $this->indexName( $index );
 603
 604                 $sql = 'SHOW INDEX FROM ' . $table;
 605                 $res = $this->query( $sql, $fname );
 606
 607                 if ( !$res ) {
 608                         return null;
 609                 }
 610
 611                 $result = [];
 612
 613                 foreach ( $res as $row ) {
 614                         if ( $row->Key_name == $index ) {
 615                                 $result[] = $row;
 616                         }
 617                 }
 618
 619                 return empty( $result ) ? false : $result;
 620         }
 621
 622         /**
 623          * @param string $s
 624          * @return string
 625          */
 626         public function strencode( $s ) {
 627                 return $this->mysqlRealEscapeString( $s );
 628         }
 629
 630         /**
 631          * @param string $s
 632          * @return mixed
 633          */
 634         abstract protected function mysqlRealEscapeString( $s );
 635
 636         public function addQuotes( $s ) {
 637                 if ( is_bool( $s ) ) {
 638                         // Parent would transform to int, which does not play nice with MySQL type juggling.
 639                         // When searching for an int in a string column, the strings are cast to int, which
 640                         // means false would match any string not starting with a number.
 641                         $s = (string)(int)$s;
 642                 }
 643                 return parent::addQuotes( $s );
 644         }
 645
 646         /**
 647          * MySQL uses `backticks` for identifier quoting instead of the sql standard "double quotes".
 648          *
 649          * @param string $s
 650          * @return string
 651          */
 652         public function addIdentifierQuotes( $s ) {
 653                 // Characters in the range \u0001-\uFFFF are valid in a quoted identifier
 654                 // Remove NUL bytes and escape backticks by doubling
 655                 return '`' . str_replace( [ "\0", '`' ], [ '', '``' ], $s ) . '`';
 656         }
 657
 658         /**
 659          * @param string $name
 660          * @return bool
 661          */
 662         public function isQuotedIdentifier( $name ) {
 663                 return strlen( $name ) && $name[0] == '`' && substr( $name, -1, 1 ) == '`';
 664         }
 665
 666         public function getLag() {
 667                 if ( $this->getLagDetectionMethod() === 'pt-heartbeat' ) {
 668                         return $this->getLagFromPtHeartbeat();
 669                 } else {
 670                         return $this->getLagFromSlaveStatus();
 671                 }
 672         }
 673
 674         /**
 675          * @return string
 676          */
 677         protected function getLagDetectionMethod() {
 678                 return $this->lagDetectionMethod;
 679         }
 680
 681         /**
 682          * @return bool|int
 683          */
 684         protected function getLagFromSlaveStatus() {
 685                 $res = $this->query( 'SHOW SLAVE STATUS', __METHOD__ );
 686                 $row = $res ? $res->fetchObject() : false;
 687                 if ( $row && strval( $row->Seconds_Behind_Master ) !== '' ) {
 688                         return intval( $row->Seconds_Behind_Master );
 689                 }
 690
 691                 return false;
 692         }
 693
 694         /**
 695          * @return bool|float
 696          */
 697         protected function getLagFromPtHeartbeat() {
 698                 $options = $this->lagDetectionOptions;
 699
 700                 if ( isset( $options['conds'] ) ) {
 701                         // Best method for multi-DC setups: use logical channel names
 702                         $data = $this->getHeartbeatData( $options['conds'] );
 703                 } else {
 704                         // Standard method: use master server ID (works with stock pt-heartbeat)
 705                         $masterInfo = $this->getMasterServerInfo();
 706                         if ( !$masterInfo ) {
 707                                 $this->queryLogger->error(
 708                                         "Unable to query master of {db_server} for server ID",
 709                                         $this->getLogContext( [
 710                                                 'method' => __METHOD__
 711                                         ] )
 712                                 );
 713
 714                                 return false; // could not get master server ID
 715                         }
 716
 717                         $conds = [ 'server_id' => intval( $masterInfo['serverId'] ) ];
 718                         $data = $this->getHeartbeatData( $conds );
 719                 }
 720
 721                 list( $time, $nowUnix ) = $data;
 722                 if ( $time !== null ) {
 723                         // @time is in ISO format like "2015-09-25T16:48:10.000510"
 724                         $dateTime = new DateTime( $time, new DateTimeZone( 'UTC' ) );
 725                         $timeUnix = (int)$dateTime->format( 'U' ) + $dateTime->format( 'u' ) / 1e6;
 726
 727                         return max( $nowUnix - $timeUnix, 0.0 );
 728                 }
 729
 730                 $this->queryLogger->error(
 731                         "Unable to find pt-heartbeat row for {db_server}",
 732                         $this->getLogContext( [
 733                                 'method' => __METHOD__
 734                         ] )
 735                 );
 736
 737                 return false;
 738         }
 739
 740         protected function getMasterServerInfo() {
 741                 $cache = $this->srvCache;
 742                 $key = $cache->makeGlobalKey(
 743                         'mysql',
 744                         'master-info',
 745                         // Using one key for all cluster replica DBs is preferable
 746                         $this->getLBInfo( 'clusterMasterHost' ) ?: $this->getServer()
 747                 );
 748
 749                 return $cache->getWithSetCallback(
 750                         $key,
 751                         $cache::TTL_INDEFINITE,
 752                         function () use ( $cache, $key ) {
 753                                 // Get and leave a lock key in place for a short period
 754                                 if ( !$cache->lock( $key, 0, 10 ) ) {
 755                                         return false; // avoid master connection spike slams
 756                                 }
 757
 758                                 $conn = $this->getLazyMasterHandle();
 759                                 if ( !$conn ) {
 760                                         return false; // something is misconfigured
 761                                 }
 762
 763                                 // Connect to and query the master; catch errors to avoid outages
 764                                 try {
 765                                         $res = $conn->query( 'SELECT @@server_id AS id', __METHOD__ );
 766                                         $row = $res ? $res->fetchObject() : false;
 767                                         $id = $row ? (int)$row->id : 0;
 768                                 } catch ( DBError $e ) {
 769                                         $id = 0;
 770                                 }
 771
 772                                 // Cache the ID if it was retrieved
 773                                 return $id ? [ 'serverId' => $id, 'asOf' => time() ] : false;
 774                         }
 775                 );
 776         }
 777
 778         /**
 779          * @param array $conds WHERE clause conditions to find a row
 780          * @return array (heartbeat `ts` column value or null, UNIX timestamp) for the newest beat
 781          * @see https://www.percona.com/doc/percona-toolkit/2.1/pt-heartbeat.html
 782          */
 783         protected function getHeartbeatData( array $conds ) {
 784                 // Query time and trip time are not counted
 785                 $nowUnix = microtime( true );
 786                 // Do not bother starting implicit transactions here
 787                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
 788                 try {
 789                         $whereSQL = $this->makeList( $conds, self::LIST_AND );
 790                         // Use ORDER BY for channel based queries since that field might not be UNIQUE.
 791                         // Note: this would use "TIMESTAMPDIFF(MICROSECOND,ts,UTC_TIMESTAMP(6))" but the
 792                         // percision field is not supported in MySQL <= 5.5.
 793                         $res = $this->query(
 794                                 "SELECT ts FROM heartbeat.heartbeat WHERE $whereSQL ORDER BY ts DESC LIMIT 1"
 795                         );
 796                         $row = $res ? $res->fetchObject() : false;
 797                 } finally {
 798                         $this->restoreFlags();
 799                 }
 800
 801                 return [ $row ? $row->ts : null, $nowUnix ];
 802         }
 803
 804         protected function getApproximateLagStatus() {
 805                 if ( $this->getLagDetectionMethod() === 'pt-heartbeat' ) {
 806                         // Disable caching since this is fast enough and we don't wan't
 807                         // to be *too* pessimistic by having both the cache TTL and the
 808                         // pt-heartbeat interval count as lag in getSessionLagStatus()
 809                         return parent::getApproximateLagStatus();
 810                 }
 811
 812                 $key = $this->srvCache->makeGlobalKey( 'mysql-lag', $this->getServer() );
 813                 $approxLag = $this->srvCache->get( $key );
 814                 if ( !$approxLag ) {
 815                         $approxLag = parent::getApproximateLagStatus();
 816                         $this->srvCache->set( $key, $approxLag, 1 );
 817                 }
 818
 819                 return $approxLag;
 820         }
 821
 822         public function masterPosWait( DBMasterPos $pos, $timeout ) {
 823                 if ( !( $pos instanceof MySQLMasterPos ) ) {
 824                         throw new InvalidArgumentException( "Position not an instance of MySQLMasterPos" );
 825                 }
 826
 827                 if ( $this->getLBInfo( 'is static' ) === true ) {
 828                         return 0; // this is a copy of a read-only dataset with no master DB
 829                 } elseif ( $this->lastKnownReplicaPos && $this->lastKnownReplicaPos->hasReached( $pos ) ) {
 830                         return 0; // already reached this point for sure
 831                 }
 832
 833                 // Call doQuery() directly, to avoid opening a transaction if DBO_TRX is set
 834                 if ( $this->useGTIDs && $pos->gtids ) {
 835                         // Wait on the GTID set (MariaDB only)
 836                         $gtidArg = $this->addQuotes( implode( ',', $pos->gtids ) );
 837                         $res = $this->doQuery( "SELECT MASTER_GTID_WAIT($gtidArg, $timeout)" );
 838                 } else {
 839                         // Wait on the binlog coordinates
 840                         $encFile = $this->addQuotes( $pos->file );
 841                         $encPos = intval( $pos->pos );
 842                         $res = $this->doQuery( "SELECT MASTER_POS_WAIT($encFile, $encPos, $timeout)" );
 843                 }
 844
 845                 $row = $res ? $this->fetchRow( $res ) : false;
 846                 if ( !$row ) {
 847                         throw new DBExpectedError( $this,
 848                                 "MASTER_POS_WAIT() or MASTER_GTID_WAIT() failed: {$this->lastError()}" );
 849                 }
 850
 851                 // Result can be NULL (error), -1 (timeout), or 0+ per the MySQL manual
 852                 $status = ( $row[0] !== null ) ? intval( $row[0] ) : null;
 853                 if ( $status === null ) {
 854                         // T126436: jobs programmed to wait on master positions might be referencing binlogs
 855                         // with an old master hostname. Such calls make MASTER_POS_WAIT() return null. Try
 856                         // to detect this and treat the replica DB as having reached the position; a proper master
 857                         // switchover already requires that the new master be caught up before the switch.
 858                         $replicationPos = $this->getReplicaPos();
 859                         if ( $replicationPos && !$replicationPos->channelsMatch( $pos ) ) {
 860                                 $this->lastKnownReplicaPos = $replicationPos;
 861                                 $status = 0;
 862                         }
 863                 } elseif ( $status >= 0 ) {
 864                         // Remember that this position was reached to save queries next time
 865                         $this->lastKnownReplicaPos = $pos;
 866                 }
 867
 868                 return $status;
 869         }
 870
 871         /**
 872          * Get the position of the master from SHOW SLAVE STATUS
 873          *
 874          * @return MySQLMasterPos|bool
 875          */
 876         public function getReplicaPos() {
 877                 $res = $this->query( 'SHOW SLAVE STATUS', __METHOD__ );
 878                 $row = $this->fetchObject( $res );
 879
 880                 if ( $row ) {
 881                         $pos = isset( $row->Exec_master_log_pos )
 882                                 ? $row->Exec_master_log_pos
 883                                 : $row->Exec_Master_Log_Pos;
 884                         // Also fetch the last-applied GTID set (MariaDB)
 885                         if ( $this->useGTIDs ) {
 886                                 $res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'gtid_slave_pos'", __METHOD__ );
 887                                 $gtidRow = $this->fetchObject( $res );
 888                                 $gtidSet = $gtidRow ? $gtidRow->Value : '';
 889                         } else {
 890                                 $gtidSet = '';
 891                         }
 892
 893                         return new MySQLMasterPos( $row->Relay_Master_Log_File, $pos, $gtidSet );
 894                 } else {
 895                         return false;
 896                 }
 897         }
 898
 899         /**
 900          * Get the position of the master from SHOW MASTER STATUS
 901          *
 902          * @return MySQLMasterPos|bool
 903          */
 904         public function getMasterPos() {
 905                 $res = $this->query( 'SHOW MASTER STATUS', __METHOD__ );
 906                 $row = $this->fetchObject( $res );
 907
 908                 if ( $row ) {
 909                         // Also fetch the last-written GTID set (MariaDB)
 910                         if ( $this->useGTIDs ) {
 911                                 $res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'gtid_binlog_pos'", __METHOD__ );
 912                                 $gtidRow = $this->fetchObject( $res );
 913                                 $gtidSet = $gtidRow ? $gtidRow->Value : '';
 914                         } else {
 915                                 $gtidSet = '';
 916                         }
 917
 918                         return new MySQLMasterPos( $row->File, $row->Position, $gtidSet );
 919                 } else {
 920                         return false;
 921                 }
 922         }
 923
 924         public function serverIsReadOnly() {
 925                 $res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'read_only'", __METHOD__ );
 926                 $row = $this->fetchObject( $res );
 927
 928                 return $row ? ( strtolower( $row->Value ) === 'on' ) : false;
 929         }
 930
 931         /**
 932          * @param string $index
 933          * @return string
 934          */
 935         function useIndexClause( $index ) {
 936                 return "FORCE INDEX (" . $this->indexName( $index ) . ")";
 937         }
 938
 939         /**
 940          * @param string $index
 941          * @return string
 942          */
 943         function ignoreIndexClause( $index ) {
 944                 return "IGNORE INDEX (" . $this->indexName( $index ) . ")";
 945         }
 946
 947         /**
 948          * @return string
 949          */
 950         function lowPriorityOption() {
 951                 return 'LOW_PRIORITY';
 952         }
 953
 954         /**
 955          * @return string
 956          */
 957         public function getSoftwareLink() {
 958                 // MariaDB includes its name in its version string; this is how MariaDB's version of
 959                 // the mysql command-line client identifies MariaDB servers (see mariadb_connection()
 960                 // in libmysql/libmysql.c).
 961                 $version = $this->getServerVersion();
 962                 if ( strpos( $version, 'MariaDB' ) !== false || strpos( $version, '-maria-' ) !== false ) {
 963                         return '[{{int:version-db-mariadb-url}} MariaDB]';
 964                 }
 965
 966                 // Percona Server's version suffix is not very distinctive, and @@version_comment
 967                 // doesn't give the necessary info for source builds, so assume the server is MySQL.
 968                 // (Even Percona's version of mysql doesn't try to make the distinction.)
 969                 return '[{{int:version-db-mysql-url}} MySQL]';
 970         }
 971
 972         /**
 973          * @return string
 974          */
 975         public function getServerVersion() {
 976                 // Not using mysql_get_server_info() or similar for consistency: in the handshake,
 977                 // MariaDB 10 adds the prefix "5.5.5-", and only some newer client libraries strip
 978                 // it off (see RPL_VERSION_HACK in include/mysql_com.h).
 979                 if ( $this->serverVersion === null ) {
 980                         $this->serverVersion = $this->selectField( '', 'VERSION()', '', __METHOD__ );
 981                 }
 982                 return $this->serverVersion;
 983         }
 984
 985         /**
 986          * @param array $options
 987          */
 988         public function setSessionOptions( array $options ) {
 989                 if ( isset( $options['connTimeout'] ) ) {
 990                         $timeout = (int)$options['connTimeout'];
 991                         $this->query( "SET net_read_timeout=$timeout" );
 992                         $this->query( "SET net_write_timeout=$timeout" );
 993                 }
 994         }
 995
 996         /**
 997          * @param string &$sql
 998          * @param string &$newLine
 999          * @return bool
1000          */
1001         public function streamStatementEnd( &$sql, &$newLine ) {
1002                 if ( strtoupper( substr( $newLine, 0, 9 ) ) == 'DELIMITER' ) {
1003                         preg_match( '/^DELIMITER\s+(\S+)/', $newLine, $m );
1004                         $this->delimiter = $m[1];
1005                         $newLine = '';
1006                 }
1007
1008                 return parent::streamStatementEnd( $sql, $newLine );
1009         }
1010
1011         /**
1012          * Check to see if a named lock is available. This is non-blocking.
1013          *
1014          * @param string $lockName Name of lock to poll
1015          * @param string $method Name of method calling us
1016          * @return bool
1017          * @since 1.20
1018          */
1019         public function lockIsFree( $lockName, $method ) {
1020                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1021                 $result = $this->query( "SELECT IS_FREE_LOCK($encName) AS lockstatus", $method );
1022                 $row = $this->fetchObject( $result );
1023
1024                 return ( $row->lockstatus == 1 );
1025         }
1026
1027         /**
1028          * @param string $lockName
1029          * @param string $method
1030          * @param int $timeout
1031          * @return bool
1032          */
1033         public function lock( $lockName, $method, $timeout = 5 ) {
1034                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1035                 $result = $this->query( "SELECT GET_LOCK($encName, $timeout) AS lockstatus", $method );
1036                 $row = $this->fetchObject( $result );
1037
1038                 if ( $row->lockstatus == 1 ) {
1039                         parent::lock( $lockName, $method, $timeout ); // record
1040                         return true;
1041                 }
1042
1043                 $this->queryLogger->warning( __METHOD__ . " failed to acquire lock '$lockName'\n" );
1044
1045                 return false;
1046         }
1047
1048         /**
1049          * FROM MYSQL DOCS:
1050          * https://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_release-lock
1051          * @param string $lockName
1052          * @param string $method
1053          * @return bool
1054          */
1055         public function unlock( $lockName, $method ) {
1056                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1057                 $result = $this->query( "SELECT RELEASE_LOCK($encName) as lockstatus", $method );
1058                 $row = $this->fetchObject( $result );
1059
1060                 if ( $row->lockstatus == 1 ) {
1061                         parent::unlock( $lockName, $method ); // record
1062                         return true;
1063                 }
1064
1065                 $this->queryLogger->warning( __METHOD__ . " failed to release lock '$lockName'\n" );
1066
1067                 return false;
1068         }
1069
1070         private function makeLockName( $lockName ) {
1071                 // https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
1072                 // Newer version enforce a 64 char length limit.
1073                 return ( strlen( $lockName ) > 64 ) ? sha1( $lockName ) : $lockName;
1074         }
1075
1076         public function namedLocksEnqueue() {
1077                 return true;
1078         }
1079
1080         public function tableLocksHaveTransactionScope() {
1081                 return false; // tied to TCP connection
1082         }
1083
1084         protected function doLockTables( array $read, array $write, $method ) {
1085                 $items = [];
1086                 foreach ( $write as $table ) {
1087                         $items[] = $this->tableName( $table ) . ' WRITE';
1088                 }
1089                 foreach ( $read as $table ) {
1090                         $items[] = $this->tableName( $table ) . ' READ';
1091                 }
1092
1093                 $sql = "LOCK TABLES " . implode( ',', $items );
1094                 $this->query( $sql, $method );
1095
1096                 return true;
1097         }
1098
1099         protected function doUnlockTables( $method ) {
1100                 $this->query( "UNLOCK TABLES", $method );
1101
1102                 return true;
1103         }
1104
1105         /**
1106          * @param bool $value
1107          */
1108         public function setBigSelects( $value = true ) {
1109                 if ( $value === 'default' ) {
1110                         if ( $this->mDefaultBigSelects === null ) {
1111                                 # Function hasn't been called before so it must already be set to the default
1112                                 return;
1113                         } else {
1114                                 $value = $this->mDefaultBigSelects;
1115                         }
1116                 } elseif ( $this->mDefaultBigSelects === null ) {
1117                         $this->mDefaultBigSelects =
1118                                 (bool)$this->selectField( false, '@@sql_big_selects', '', __METHOD__ );
1119                 }
1120                 $encValue = $value ? '1' : '0';
1121                 $this->query( "SET sql_big_selects=$encValue", __METHOD__ );
1122         }
1123
1124         /**
1125          * DELETE where the condition is a join. MySql uses multi-table deletes.
1126          * @param string $delTable
1127          * @param string $joinTable
1128          * @param string $delVar
1129          * @param string $joinVar
1130          * @param array|string $conds
1131          * @param bool|string $fname
1132          * @throws DBUnexpectedError
1133          * @return bool|ResultWrapper
1134          */
1135         public function deleteJoin(
1136                 $delTable, $joinTable, $delVar, $joinVar, $conds, $fname = __METHOD__
1137         ) {
1138                 if ( !$conds ) {
1139                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
1140                 }
1141
1142                 $delTable = $this->tableName( $delTable );
1143                 $joinTable = $this->tableName( $joinTable );
1144                 $sql = "DELETE $delTable FROM $delTable, $joinTable WHERE $delVar=$joinVar ";
1145
1146                 if ( $conds != '*' ) {
1147                         $sql .= ' AND ' . $this->makeList( $conds, self::LIST_AND );
1148                 }
1149
1150                 return $this->query( $sql, $fname );
1151         }
1152
1153         /**
1154          * @param string $table
1155          * @param array $rows
1156          * @param array $uniqueIndexes
1157          * @param array $set
1158          * @param string $fname
1159          * @return bool
1160          */
1161         public function upsert( $table, array $rows, array $uniqueIndexes,
1162                 array $set, $fname = __METHOD__
1163         ) {
1164                 if ( !count( $rows ) ) {
1165                         return true; // nothing to do
1166                 }
1167
1168                 if ( !is_array( reset( $rows ) ) ) {
1169                         $rows = [ $rows ];
1170                 }
1171
1172                 $table = $this->tableName( $table );
1173                 $columns = array_keys( $rows[0] );
1174
1175                 $sql = "INSERT INTO $table (" . implode( ',', $columns ) . ') VALUES ';
1176                 $rowTuples = [];
1177                 foreach ( $rows as $row ) {
1178                         $rowTuples[] = '(' . $this->makeList( $row ) . ')';
1179                 }
1180                 $sql .= implode( ',', $rowTuples );
1181                 $sql .= " ON DUPLICATE KEY UPDATE " . $this->makeList( $set, self::LIST_SET );
1182
1183                 return (bool)$this->query( $sql, $fname );
1184         }
1185
1186         /**
1187          * Determines how long the server has been up
1188          *
1189          * @return int
1190          */
1191         public function getServerUptime() {
1192                 $vars = $this->getMysqlStatus( 'Uptime' );
1193
1194                 return (int)$vars['Uptime'];
1195         }
1196
1197         /**
1198          * Determines if the last failure was due to a deadlock
1199          *
1200          * @return bool
1201          */
1202         public function wasDeadlock() {
1203                 return $this->lastErrno() == 1213;
1204         }
1205
1206         /**
1207          * Determines if the last failure was due to a lock timeout
1208          *
1209          * @return bool
1210          */
1211         public function wasLockTimeout() {
1212                 return $this->lastErrno() == 1205;
1213         }
1214
1215         public function wasErrorReissuable() {
1216                 return $this->lastErrno() == 2013 || $this->lastErrno() == 2006;
1217         }
1218
1219         /**
1220          * Determines if the last failure was due to the database being read-only.
1221          *
1222          * @return bool
1223          */
1224         public function wasReadOnlyError() {
1225                 return $this->lastErrno() == 1223 ||
1226                         ( $this->lastErrno() == 1290 && strpos( $this->lastError(), '--read-only' ) !== false );
1227         }
1228
1229         public function wasConnectionError( $errno ) {
1230                 return $errno == 2013 || $errno == 2006;
1231         }
1232
1233         /**
1234          * @param string $oldName
1235          * @param string $newName
1236          * @param bool $temporary
1237          * @param string $fname
1238          * @return bool
1239          */
1240         public function duplicateTableStructure(
1241                 $oldName, $newName, $temporary = false, $fname = __METHOD__
1242         ) {
1243                 $tmp = $temporary ? 'TEMPORARY ' : '';
1244                 $newName = $this->addIdentifierQuotes( $newName );
1245                 $oldName = $this->addIdentifierQuotes( $oldName );
1246                 $query = "CREATE $tmp TABLE $newName (LIKE $oldName)";
1247
1248                 return $this->query( $query, $fname );
1249         }
1250
1251         /**
1252          * List all tables on the database
1253          *
1254          * @param string $prefix Only show tables with this prefix, e.g. mw_
1255          * @param string $fname Calling function name
1256          * @return array
1257          */
1258         public function listTables( $prefix = null, $fname = __METHOD__ ) {
1259                 $result = $this->query( "SHOW TABLES", $fname );
1260
1261                 $endArray = [];
1262
1263                 foreach ( $result as $table ) {
1264                         $vars = get_object_vars( $table );
1265                         $table = array_pop( $vars );
1266
1267                         if ( !$prefix || strpos( $table, $prefix ) === 0 ) {
1268                                 $endArray[] = $table;
1269                         }
1270                 }
1271
1272                 return $endArray;
1273         }
1274
1275         /**
1276          * @param string $tableName
1277          * @param string $fName
1278          * @return bool|ResultWrapper
1279          */
1280         public function dropTable( $tableName, $fName = __METHOD__ ) {
1281                 if ( !$this->tableExists( $tableName, $fName ) ) {
1282                         return false;
1283                 }
1284
1285                 return $this->query( "DROP TABLE IF EXISTS " . $this->tableName( $tableName ), $fName );
1286         }
1287
1288         /**
1289          * Get status information from SHOW STATUS in an associative array
1290          *
1291          * @param string $which
1292          * @return array
1293          */
1294         private function getMysqlStatus( $which = "%" ) {
1295                 $res = $this->query( "SHOW STATUS LIKE '{$which}'" );
1296                 $status = [];
1297
1298                 foreach ( $res as $row ) {
1299                         $status[$row->Variable_name] = $row->Value;
1300                 }
1301
1302                 return $status;
1303         }
1304
1305         /**
1306          * Lists VIEWs in the database
1307          *
1308          * @param string $prefix Only show VIEWs with this prefix, eg.
1309          * unit_test_, or $wgDBprefix. Default: null, would return all views.
1310          * @param string $fname Name of calling function
1311          * @return array
1312          * @since 1.22
1313          */
1314         public function listViews( $prefix = null, $fname = __METHOD__ ) {
1315                 // The name of the column containing the name of the VIEW
1316                 $propertyName = 'Tables_in_' . $this->mDBname;
1317
1318                 // Query for the VIEWS
1319                 $res = $this->query( 'SHOW FULL TABLES WHERE TABLE_TYPE = "VIEW"' );
1320                 $allViews = [];
1321                 foreach ( $res as $row ) {
1322                         array_push( $allViews, $row->$propertyName );
1323                 }
1324
1325                 if ( is_null( $prefix ) || $prefix === '' ) {
1326                         return $allViews;
1327                 }
1328
1329                 $filteredViews = [];
1330                 foreach ( $allViews as $viewName ) {
1331                         // Does the name of this VIEW start with the table-prefix?
1332                         if ( strpos( $viewName, $prefix ) === 0 ) {
1333                                 array_push( $filteredViews, $viewName );
1334                         }
1335                 }
1336
1337                 return $filteredViews;
1338         }
1339
1340         /**
1341          * Differentiates between a TABLE and a VIEW.
1342          *
1343          * @param string $name Name of the TABLE/VIEW to test
1344          * @param string $prefix
1345          * @return bool
1346          * @since 1.22
1347          */
1348         public function isView( $name, $prefix = null ) {
1349                 return in_array( $name, $this->listViews( $prefix ) );
1350         }
1351
1352         /**
1353          * Allows for index remapping in queries where this is not consistent across DBMS
1354          *
1355          * @param string $index
1356          * @return string
1357          */
1358         protected function indexName( $index ) {
1359                 /**
1360                  * When SQLite indexes were introduced in r45764, it was noted that
1361                  * SQLite requires index names to be unique within the whole database,
1362                  * not just within a schema. As discussed in CR r45819, to avoid the
1363                  * need for a schema change on existing installations, the indexes
1364                  * were implicitly mapped from the new names to the old names.
1365                  *
1366                  * This mapping can be removed if DB patches are introduced to alter
1367                  * the relevant tables in existing installations. Note that because
1368                  * this index mapping applies to table creation, even new installations
1369                  * of MySQL have the old names (except for installations created during
1370                  * a period where this mapping was inappropriately removed, see
1371                  * T154872).
1372                  */
1373                 $renamed = [
1374                         'ar_usertext_timestamp' => 'usertext_timestamp',
1375                         'un_user_id' => 'user_id',
1376                         'un_user_ip' => 'user_ip',
1377                 ];
1378
1379                 if ( isset( $renamed[$index] ) ) {
1380                         return $renamed[$index];
1381                 } else {
1382                         return $index;
1383                 }
1384         }
1385 }
1386
1387 class_alias( DatabaseMysqlBase::class, 'DatabaseMysqlBase' );